KR101631077B1

KR101631077B1 - Apparatus and method for boosting a backlight based on image characteristics

Info

Publication number: KR101631077B1
Application number: KR1020150112547A
Authority: KR
Inventors: 유재희
Original assignee: 홍익대학교 산학협력단
Priority date: 2015-08-10
Filing date: 2015-08-10
Publication date: 2016-06-16

Abstract

The purpose of the present invention is to adjust boosting of a backlight based on image characteristics. A display device according to the present invention grasps distribution characteristics of a unit image when the unit image such as an image frame or a block in the image frame is inputted, and determines whether to boost brightness of a backlight provided in a region of a panel in which the unit image is to be displayed, based on density of the grasped distribution characteristics in one or more of a plurality of sections obtained by dividing an allowable range of a pixel value of an image (for example, a concentration of the pixel value with respect to a reference value in a section). The brightness of the backlight is boosted when the density is equal to or greater than a certain degree. A boosting intensity is determined to be greater when the density is high than when the density is low. Image quality is considerably improved due to the booting with respect to an image having pixel value distribution characteristics having high density.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight boosting method and a backlight boosting method,

The present invention relates to a method and apparatus for adjusting the brightness of a backlight used as a light source for visually expressing a video signal.

BACKGROUND ART [0002] An LCD typically used for an image display device is largely composed of a liquid crystal panel and a backlight. The backlight provides light as a light source, and the liquid crystal panel visually expresses the image by adjusting the light transmittance of each color filter according to the color of a given image.

As described above, the LCD must have a backlight for providing a light source for displaying an image, and the backlight must be always on irrespective of which image is given to the liquid crystal panel. However, since the light of the backlight is not always used 100% in the expression of color, brightness, etc. of a given image, the backlight that is always on causes a waste of electric power.

In addition, since the liquid crystal panel does not completely block the backlight by the color filter and light leakage occurs, there is a problem that the contrast can not be faithfully expressed in the original image.

However, if the brightness of the backlight is appropriately reduced, it is possible to solve the problems caused by the aforementioned power consumption and light leakage. When the brightness of the backlight is reduced, i.e., dimmed, the displayed image becomes relatively dark. Therefore, in dimming the backlight, the light transmittance of the liquid crystal panel is increased, thereby compensating for the darkening of the image due to the intentional dimming. This compensation is called Backlight Dimming Compensation. In this backlight dimming compensation, the light transmittance adjustment for compensation is made by changing the original pixel value of the image.

However, since the pixel value can not be changed to a predetermined maximum value, for example, a value of 255 or more in the case of an 8-bit pixel, dimming compensation is limited. That is, power consumption can be reduced by dimming. However, when the original image has a bright characteristic, the brightness is not compensated by the dimming, and the image quality of the displayed image is deteriorated.

Figure 1A is an illustration of such a problem. When the dimming is performed to lower the ratio of the backlight maximum brightness to the alpha ratio, the input pixel value is converted to 1 /? In order to compensate for the darkening of the image due to the dimming. For example, if α is 0.8 (that is, when 20% is lowered), each input pixel value is converted into 1.25 times pixel values corresponding to 1 / α based on the compensation rule (1) do. However, in this example, the input pixel values 2 that are 0.8 or more of the maximum value Max (255 in the case of 8 bits, for example) that can be represented by the pixel data are all equal to the maximum value Max The image quality of the displayed image is deteriorated by the saturation phenomenon 1a which is converted into the saturation phenomenon 1a.

In order to avoid such a problem of image quality degradation, a backlight dimming method has been proposed in which dimming is performed based on a maximum value among pixel values in an image. In this dimming method, the brightest pixel value of the image is used as the brightness of the backlight. However, using such a dimming method does not deteriorate the brightness of the image, but because the pixel value is used as the brightness of the backlight when there is a small number of bright pixels having little relation to the overall image characteristics of the image, or Since the pixel value due to noise may be used as the brightness of the backlight, the backlight may provide more brightness than necessary for the overall characteristics of the image. If this happens, more power is consumed than necessary. In addition, since it is not properly dimmed in accordance with the overall characteristics of the image, there arises a problem that the contrast is lowered due to the light leakage phenomenon in the above-mentioned liquid crystal panel.

In order to reduce the power consumption of the backlight, there is a case in which the backlight dimming is performed in a manner as described above. However, when the backlight is increased more than the current brightness to improve the image quality (boosting the backlight) ).

Fig. 1B is a schematic diagram for explaining the principle that the image quality is enhanced by the backlight boosting. For any of the dark pixel value 2a and the arbitrary bright pixel value 2b, Between the pixel values 2a and 2b when the backlight is boosted (the example of FIG. 1B shows that the brightness of the backlight is boosted by 1.6 times, that is, 60%) than the visually outputted brightness difference 3 And the brightness difference (4) is larger. Theoretically, the brightness difference will be as much as the percentage of boosting the backlight, i.e., 60%. Therefore, the image displayed by the boosting has a higher contrast than when it is not boosted, and the user feels much more clear visually. By this effect, the user can experience improvement in image quality by boosting the backlight.

However, if the image is uniformly boosted, some images may appear to be faded, or dark portions may appear in grayscale, resulting in deterioration in image quality.

Thus, uniformly boosting the images may negatively affect the image quality even though power consumption is additionally generated. That is, there is a problem that image quality is rather distorted even though power consumption is additionally consumed by boosting.

It is an object of the present invention to provide a backlight dimming method and apparatus for reducing power consumption by backlight while minimizing degradation of image quality for an image.

It is another object of the present invention to provide a method and an apparatus that can maximize the backlight dimming by reflecting the human tolerance of image quality deterioration.

It is yet another object of the present invention to provide a method and apparatus that enables dimming of a backlight to be optimized for the characteristics of a given image.

It is still another object of the present invention to provide a method and an apparatus that can improve the image quality of an image by boosting the brightness of the backlight according to image characteristics.

It is a further object of the present invention to provide a method and apparatus for increasing the brightness of a backlight such that the additional power consumed by boosting is most efficient at increasing the brightness of a pixel.

It is still another object of the present invention to provide an image display apparatus and a method for controlling brightness of a backlight for improving image quality and / or power consumption in consideration of brightness change between temporally continuous images, In order to prevent the occurrence of the problem.

It is to be understood that the object of the present invention is not limited to the explicitly stated objects, but, of course, it is an object of the present invention to achieve the effect which can be derived from the following specific and exemplary description of the present invention.

According to an aspect of the present invention, an apparatus for visually representing a video signal includes a backlight for providing a light source, a panel for outputting a visual signal by adjusting a transmittance of the light source according to input pixel values, An analyzing unit for analyzing distribution characteristics of pixel values of a unit image based on the degree of density distribution of the identified distribution characteristics in one or more sections of the plurality of sections divided for the range that the pixel value can have, A controller configured to determine an intensity of the light source provided in an area of the panel to be output as a visual signal, each pixel value in the unit image being an intensity that is greater than a currently set intensity, and apply the determined intensity to the backlight; A signal processor configured to convert each pixel value into a signal that can be visually displayed by the panel and to apply the signal to the panel And the like. When the density is high, the controller determines a width that is greater than the currently set intensity as compared with when the density is high.

In an exemplary embodiment of the present invention, the control unit may control the density of the detected distribution characteristic centered on the first reference value and the third reference value in the darkest interval and the brightest interval among the plurality of intervals, A density state of the grasped distribution characteristic centered on a second reference value in an interval of medium brightness among the plurality of intervals and a density state of the grasped distribution characteristic centered on the fourth reference value in the brightest interval among the plurality of intervals And the degree of densification is grasped from at least one dense state among the dense states of the grasped distribution characteristics. The fourth reference value may be the same as or different from the third reference value. The controller may further include a first distribution sample in which the pixel values distributed in the brightest interval are largest compared to other intervals and a second distribution sample in which pixel values distributed in the interval of the middle brightness are the largest, , The pixel values distributed in the darkest interval are the largest compared to other intervals and the pixel values distributed in the brightest interval are compared with the distribution samples and the third distribution samples The disturbance degree with respect to each distribution sample is calculated, and the at least one densest state, in which the degree of density is grasped, is selected based on the calculated disturbance. When the at least one dense state is a plurality of dense states, the control unit reflects the dense states according to a given ratio to grasp the dense degree, wherein the ratio of the dense state, A value larger than a ratio reflected on a dense state having a low dense density is allocated and the degree of denseness is grasped from the plurality of dense states according to the assigned ratio.

In another embodiment according to the present invention, the control unit may determine the density of the cluster based on one or more differences among the distribution differences obtained by comparing the obtained distribution characteristics with respect to each of the plurality of distribution criteria The more the one or more differences are, the higher the density is. Here, the distribution criterion may include a requirement that the pixel values distributed in the brightest interval be the largest compared to other intervals, a requirement that the pixel values distributed in the interval of the middle brightness should be the largest compared with other intervals, The pixel values distributed in the darkest region have the largest number of pixel values compared to the other regions, and the pixel values distributed in the brightest region satisfy the requirements that the pixel values must be larger than the intermediate brightness region.

In one embodiment of the present invention, the controller determines the increased intensity based on the efficiency of improving the quality of power consumed by increasing the intensity of the light source when determining the density according to the density. In the present embodiment, the maximum value that the increased intensity can have is determined by the control unit, such that the image quality of the boosting-image quality relationship characteristic in which the image quality of the image is improved as the intensity of the light source is increased exceeds the predetermined reference The increase in the intensity of the light source corresponds to the increase in the intensity of the light source, which is the highest improvement rate of the image quality. Here, the maximum value that the increased intensity may have may be a value that falls within a range of 50% to 70% of the currently set intensity, preferably 60%.

In another embodiment according to the present invention, the controller determines the increased intensity based on the maximum value of the image quality, which is increased as the intensity of the light source is increased. In the present embodiment, the maximum value that the increased intensity determined by the control unit can have is an increase in the intensity of the light source in the boosting-image quality relationship characteristic in which the image quality of the image is improved by increasing the intensity of the light source Corresponds to an increase in the intensity of the light source that is no longer improved or that the increase in image quality enhancement begins to fall below the predefined threshold.

According to an embodiment of the present invention, when the high luminance pixel values are equal to or more than a predetermined ratio among the pixel values of the unit image, the controller performs correction to reduce the determined increase width, The backlight may be controlled so that the intensity is applied or the current set intensity may be maintained without reflecting the determined increased width. Here, the high luminance pixel values are values equal to or greater than a predetermined ratio of the maximum value that the pixel in the unit image can have, and the predetermined ratio may be a predetermined reference value in a range of 90% or more and less than 100%. In the present embodiment, when the densified state of the grasped distribution characteristic centered on the reference value in the interval of the middle brightness among the plurality of intervals is not reflected, and when the densified degree is grasped, Corrected intensity may not be corrected or applied to the backlight.

In one embodiment of the present invention, the control unit corrects the determined increased width when the current unit image is brighter than the previous unit image in the temporally continuous unit images, Is corrected in such a manner that the width to be increased is further reduced as compared with when the width is small.

According to an embodiment of the present invention, when the ratio of the dark portion values corresponding to the predetermined reference value or less among the pixel values of the unit image is more than a limited ratio, The correction is made so as to reduce the determined increasing width, but is corrected in such a manner that the increased width is further reduced as compared with when the ratio of the arm portions is large.

According to an embodiment of the present invention, the controller may further increase the determined increased width based on whether the identified spatial frequency of the pixel values of the unit image belongs to a designated frequency band Or decreasing the intensity of the backlight to be applied to the backlight.

According to an embodiment of the present invention, the controller may calculate a first increase in accordance with the density of densities by applying a first scheme, calculate a second increase in accordance with the density of densities by applying the first increase, A value obtained by summing up the first increment and the second increment by the ratio allocated to each is determined as the increment. Here, the first scheme is a scheme for determining the intensity of a light source based on efficiency of power enhancement by increasing the intensity of the light source, and the second scheme may increase the intensity of the light source The intensity of the light source is determined based on the maximum value of the image quality that is improved according to the image quality. In the present embodiment, the ratio assigned to the first increase and the second increase may be set to the same or different values based on the user's selection or the physical display characteristics of the panel to determine the increased width Lt; / RTI >

In an embodiment according to the present invention, the control unit determines whether to increase or decrease the intensity of the light source more or less than the currently set intensity, based on the brightness of the unit image When determined, the width to be increased is determined based on the degree of densification. In the present embodiment, when the brightness of the unit image indicates a predetermined reference value or less, the backlight is controlled so that the intensity of the light source is reduced more than the currently set intensity and the reduced intensity is applied, The intensity of the light source is determined in such a manner that the decreasing width becomes larger when the inclination degree is smaller than when it is greater or when the brightness characteristic value of the unit image is smaller. Here, the inclination is an average of individual hardness (gradient) obtained for the pixel values of the unit image, and the individual hardness is obtained by dividing the difference between the pixel values of any two pixels by the distance between the pixels And the brightness characteristic value is calculated from a boundary pixel value in which the cumulative number of pixel values distributed starting from a maximum value that the pixel can have, out of the pixel values of the unit image, And is a value having a characteristic proportional to the size of the boundary pixel value. If the brightness of the unit image is greater than or equal to a predetermined reference value and the degree of density is lower than a predefined threshold, the intensity of the currently set light source is maintained for the unit image without increasing or decreasing. In addition, in the present embodiment, the control unit may be configured to reduce the intensity of the light source to be inputted, rather than to increase the intensity of the light source, based on the selection information supplied from the user Or to make the intensity of the light source increase or decrease.

According to another aspect of the present invention, there is provided a method of adjusting intensity of a light source required to visually represent a video signal, including: a step of determining a distribution characteristic of pixel values of an input unit image; Wherein each pixel value in the unit image is provided to an area of a display panel to be output as a visual signal, based on the density of the acquired distribution characteristic in at least one of the plurality of intervals divided for the range, And a step of controlling the display panel so that the intensity of the determined light source is applied to an area where the unit image on the display panel is displayed . In the step 2, when the density is high, the width that is greater than the currently set intensity is determined to be larger than when the density is low.

In the above-described apparatus, method, and various embodiments, the pixel value refers to the luminance calculated from the values of the respective color elements constituting the color with respect to one pixel, Refers to a value corresponding to one element. The unit image is an image corresponding to a certain frame or field in a continuous image, or corresponds to a block of a partial area divided in one image.

At least one embodiment of the present invention described in detail above with reference to the present invention or the drawings attached hereto is to understand characteristics of an input image and to maximize dimming accordingly, thereby greatly reducing power consumption. Specifically, based on how the bright pixel values are distributed in the image, a relatively small distribution dims the dimming for the image, and if the distribution is heavily dimmed, the optimal dimming for a given image . As a result, the present invention maximally reduces power consumption within a range that minimizes deterioration of image quality.

In the embodiment according to the present invention, the power consumption is reduced by 5 to 10% in the global dimming under the criterion of maintaining the picture quality of 38 to 40 dB in the PSNR (Peak Signal-to-Noise Ratio) When local dimming and dimming for each color element (R, G, B) are applied, the power consumption can be reduced about 4 times and 5 times as compared with the case of global dimming.

In addition, the embodiment of the present invention for controlling the brightness of the backlight by determining the boosting intensity according to the characteristics of the image improves the image quality optimized for the image characteristics while reducing the power consumption compared to improving the image quality by boosting the backlight uniformly . In a simulation for a display device having arbitrarily selected physical characteristics, assuming that the consumed power for displaying images without boosting at all is 100, the intensity of the light source uniformly increases by 1.5 times for the same images (About 50% of the boosting intensity), 150% of the power is consumed, but when the boosting intensity is dynamically selected in the range of 0 to 80% depending on the image characteristic, the average power consumption is about 125% Respectively. Therefore, it is confirmed through simulations that the power consumption is reduced by about 16.7% under the same condition, compared with the uniformly boosting method for improving the image quality.

In the case of an image having a specific pixel value distribution characteristic, boosting is instantaneously performed by 80%, thereby improving the image quality, while consuming less power as compared with the conventional uniform boosting. Thus, the image according to the embodiment of the present invention By boosting according to the characteristics, the degree of enhancement of picture quality as a whole can be felt even more greatly.

Further, power consumption is further consumed due to boosting of the backlight, but power consumption is reduced by dimming. Therefore, when both the dimming and boosting methods according to the present invention are applied, compared with maintaining the original brightness of the backlight, The image quality is improved without distorting the image quality without increasing the power consumption.

FIG. 1A is a view for explaining a saturation phenomenon that occurs when the input pixel value is compensated for in the dimming of the backlight,
FIG. 1B is a diagram schematically illustrating a principle of improving the image quality of a displayed image as the backlight is boosted more than the current brightness,
FIG. 2 is an example of a simplified configuration of a display device to which a backlight dimming method according to an image characteristic is applied, according to an embodiment of the present invention,
Figure 3 is a diagram schematically showing that an individual hardness (slope) is calculated for any two pixels included in a given unit image, in accordance with an embodiment of the present invention,
Figures 4A and 4B are diagrams each schematically showing that a slope is calculated for a given unit image, in accordance with embodiments of the present invention,
5 is a diagram showing that a brightness characteristic value for a given unit image is calculated according to a saturation tolerance according to an embodiment of the present invention,
6 shows an example of a rule for determining a dimming intensity for a unit image based on a brightness characteristic value and an inclination obtained for a given unit image according to an embodiment of the present invention,
Figure 7 illustrates a method for selectively applying a determination of dimming intensity according to a brightness characteristic value and an inclination to a given unit image, based on the homogenousness of the unit image, in accordance with an embodiment of the present invention Lt; / RTI > is an exemplary flow chart,
8 illustrates an example of a rule for correcting dimming intensity based on a change in brightness between image images displayed temporally adjacent in accordance with an embodiment of the present invention,
9A is a graph illustrating respective successive distribution characteristic samples used to grasp the type of distribution characteristics of a given unit image, according to an embodiment of the present invention,
FIG. 9B is a diagram illustrating representative values used in order to grasp the density of pixel values of a given unit image by intervals according to an exemplary embodiment of the present invention, and FIG.
FIG. 9C is a diagram illustrating an example in which pixel values of a unit image are densely or discretely distributed around a representative value in a corresponding section,
FIG. 10 is a table illustrating the distribution ratio standard value of each section for several samples used for grasping the type of the distribution characteristic of a given unit image according to another embodiment of the present invention,
FIG. 11 is a diagram for explaining schematically a method for determining a boosting intensity to be applied to a pixel value distribution characteristic of a given unit image based on characteristics of image quality enhancement versus a boosting ratio, according to an embodiment of the present invention. Fig.
12 is a graph showing an example of a rule for correcting a determined boosting intensity based on a ratio of pixel values corresponding to a dark portion below a predetermined brightness in a given unit image according to an embodiment of the present invention. This is an example table.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

2 is an example of a configuration of a display device to which a backlight dimming method according to an image characteristic is applied, according to an embodiment of the present invention. The device illustrated in FIG. 2 may be a television, a monitor, a notebook, a large billboard, a digital sign or a mobile device having an LCD or a Quantum Dot display, such as a smart phone, A quantum dot display can be included in any device to which a means of visualizing the image to the user has been added. Therefore, the scope of the claims of the present invention should not be excluded from the reason that the name of a product or commodity which is generally called is different.

2, the display device includes a display panel 14 for visually displaying an image to a user, a characteristic analyzer 11 for analyzing characteristics of an input image, A signal conversion section 12 for converting the output signal of the display panel 14 into a signal for visual display and a signal input section for receiving a signal from a user such as a remote controller, a key set, An input control unit 15 for converting input image data into image data and converting the image data into appropriate input data based on image characteristics obtained by the characteristic analyzing unit 11; The dimming control value or the boosting control value for boosting is calculated and the boosting is performed according to the dimming or boosting control value according to the calculated dimming control value And a control unit (10) for performing the control operations of the respective components. In this specification, the dimming control value and the boosting control value are collectively referred to as a 'light source control value' when necessary.

The display panel 14 provides a light source for visual display and displays the brightness of the light source for the corresponding region (whole or partial region) according to the light source control value applied by the control unit 10 A liquid crystal panel 14b for visually displaying an image by adjusting the transmissivity of each color element according to a driving signal applied to each pixel with respect to the adjustable backlight 14a and the light source of the backlight 14a, .

The signal converting unit 12 includes an image processing unit 12a for appropriately processing each pixel data of the input image, converting the pixel data into a color signal for visual representation on the liquid crystal panel 14b, And a liquid crystal driving unit 12b for converting the converted color signal into a driving signal corresponding to a visual expression system of the display panel 14. [

The input image may be a frame or a field of a video signal received in various manners. The received video signal may be, for example, a signal received or tuned from a terrestrial or satellite antenna or cable, an RF signal of a specific communication band, a video signal provided by another device, or an RGB component signal , And for each signal type, a previous processing unit that demodulates and / or decodes or properly converts the signal may be included in the front end of the apparatus of FIG.

Also, the input image may be one of a set of consecutively input images, not a single frame of a moving image.

Hereinafter, a method of adjusting the backlight dimming for the image based on the image characteristic according to an embodiment of the present invention will be described in detail first.

When an image is input from the outside to the apparatus of FIG. 2, the characteristic analyzing unit 11 grasps the characteristics of the input image. Character recognition of the input image may be started by an instruction of the control unit 10 according to the input of the user through the input control unit 15. [ The image characteristic recognized by the characteristic analyzer 11 includes a brightness characteristic value and a slope of the image. Here, the 'gradient' refers to the difference (valDif) (always positive value) between the pixel values, as exemplified in FIG. 3, for both pixels arbitrarily selected in the pixels belonging to a given image or in a specified manner Means a value obtained by dividing a pixel value (hereinafter referred to as a pixel value) by a distance pxDis (e.g., the number of mutually spaced pixels) between pixels (referred to as 'individual hardness') 31. The 'pixel value' used to obtain the individual hardness may be a luminance of a given pixel or a value of any color element in each color element (R, G, B).

4A, the characteristic analyzing unit 11 may obtain the individual hardness between immediately adjacent pixels (in this case, for example, the distance pxDis between pixels is 1) As shown in Fig. 4B, it is also possible to obtain individual hardnesses between pixels having different distances not adjacent to each other (in this case, for example, the distance pxDis between pixels is 2 or more). 4A and 4B show that the individual hardness is obtained only between the pixels located at the upper, lower, right, and left sides. However, in another embodiment according to the present invention, the present invention is not limited to the upper, It is also possible to obtain the individual hardnesses between the pixels located mutually diagonally and obtain the gradient of the image.

In order to grasp a brightness characteristic value of a given image, the characteristic analyzer 11 first calculates the values (Rv, Gv, Bv) of color elements of each pixel by a specified expression, for example, (1) and obtains the luminance (Y) from the distribution characteristics of the luminance values of the obtained pixels.

Y = 0.299 x Rv + 0.587 x Gv + 0.144 x Bv Equation [1]

Then, the brightness level corresponding to the saturation degree set by the control unit 10 is searched for the distribution characteristic. The saturation tolerance is determined by the physical display characteristic of the display panel 14 or the input information of the user through the input control unit 15 and is set in the control unit 10. 5, for the unit image having the arbitrary pixel value distribution characteristic 50, the characteristic analyzing unit 11 determines whether or not the cumulative number of pixel values distributed starting from the maximum brightness (LuMax) (A value within the range of 0 to 255 in the case of an 8-bit pixel value) corresponding to the set saturation degree (for example, 5%, 10%, 15%, etc.) Then, a value obtained by subtracting the ratio (delta in FIG. 5) of maximum brightness (LuMax) that the arbitrary pixel can have such brightness level 501 as 1, i.e., 1 - (502). Since the ratio δ includes many pixels in a range in which the unit image is close to the maximum brightness and in other words the value becomes smaller as the bright pixels are densely distributed in the maximum brightness, 1 &le; as a brightness characteristic value 502 in order to increase the value in such a case that the brightness characteristic value 502 is close to the implication meaning of the brightness characteristic value 502. [ Or 1 /? (? Can not have a value of 0), which becomes larger as the? Is smaller, as the brightness characteristic value. Of course, the brightness characteristic value having such an attribute can also be selected through other methods. For example, in the pixel value distribution characteristic 50 of the unit image, the brightness level at which the cumulative distribution number starts from the pixel value 0 and becomes '100% - the set saturation degree' can be grasped as the brightness characteristic value.

In an embodiment of the present invention, the controller 10 may reflect the distribution characteristic of the pixel values belonging to the saturation tolerance in the unit image to the brightness characteristic value obtained in the above manner, have. For example, the range of pixel values 503 belonging to the saturation tolerance is divided into Ns sub-intervals, and the weights (? _K , k = 1, 2,. ., N _S ) are separately applied to the brightness characteristic values (for example, 1-delta or 1 / delta) obtained in the first place, thereby calculating the final brightness characteristic value. For example, when the relative distribution ratio of the pixel values of each sub-section to the total number of pixels is pR _k (k = 1, 2, .., N _S ), the final brightness characteristic value (fBrPval) It can be obtained in the same manner as in [2].

fBrPval =

/ Saturation tolerance [2]

Here, α _k > α _{k + 1} (α _k is a weight assigned to a sub-section brighter than α _{k + 1} ), and α ₁ + α ₂ + +? _Ns = Ns, and iBrPval is the brightness characteristic value (for example, 1-? or 1 /?) obtained primarily.

Equation [2] applies a relatively larger weight to the subdivision to ensure that the distribution of the lighter subdivision is more reflected in the calculation of the final brightness value. The reason is that, even in the unit images having the same brightness characteristic value, the image in which the pixel values belonging to the saturation tolerance are biased toward the bright side is more affected by the picture quality than the non-uniform dimming intensity. Accordingly, when the pixel values belonging to the saturation tolerance are divided into subdivisions and their distributions are grasped, and when they are shifted to the bright side, the brightness characteristic value is calculated to be larger than that when not, Let the dimming intensity be determined a little more weakly.

As described above, when the characteristic analysis of the input image is completed, the characteristic analyzer 11 transmits information about the analyzed characteristic, that is, the brightness characteristic value and the gradient to the controller 10.

According to another embodiment of the present invention, an input image is divided into blocks of a predetermined size, and the brightness characteristic value and the gradient are determined for each of the divided blocks, And provide the identified characteristic information to the control unit 10 together with the information.

In this specification, the term " unitary image " is used collectively to refer to all of a given image, for example, one frame or field of a moving image, and blocks divided for the image.

When the characteristic information of the unit image, that is, the brightness characteristic value and the slope degree are received, the control unit 10 determines the degree of dimming of the unit image based on the characteristic information, that is, the brightness to be decreased in the brightness of the currently set backlight 5 shows that the controller 10 determines the degree of dimming, that is, the dimming intensity (hereinafter, referred to as 'dimming intensity'). For example, the dimming intensity is set to 0.2, (= 1 -0.2)), as shown in the following table.

(DmI _k , k = 1, 2, 3) assigned to each section of the slope and the brightness characteristic value divided into the sections with respect to the values that can be taken as exemplified in Fig. 6 and the exemplary values Q ) Is a mere example. The dimming intensity reference value (DmI _k , k = 1, 2, 3) of each section is _calculated by dividing the maximum value of the dimming intensity that can be obtained with respect to the brightness characteristic value belonging to the corresponding section, Quot;) < / RTI >

In the example of FIG. 6, the brightness characteristic value and the gradient are divided into three sections. Depending on whether a given unit image belongs to a certain zone (an intersection area of the interval with respect to the brightness characteristic value and an interval area of the gradient) The dimming intensity (= Q x DmI _k ) is determined by multiplying the dimming intensity reference value DmI _k by the coefficient Q assigned to the zone (the length of each arrow in Fig. 6 indicates the dimming intensity determined accordingly). ), But of course, the intervals for each characteristic may be applied in greater numbers. Also, the brightness characteristic value and the inclination degree need not always be divided into the same number of sections. Also, as illustrated in FIG. 6, the dimming intensity may be determined as a continuous variable without dividing the brightness characteristic value and the slope into discontinuous sections.

In the case of the brightness characteristic value, as shown in FIG. 6, the dimming intensity is determined to be weaker than when the value is small. The large brightness characteristic value means that, as shown in the example of FIG. 5, Since the pixel values corresponding to the acceptability are distributed by being shifted to the maximum brightness side (LuMax), the dimming intensity should be weaker than when the brightness characteristic value is smaller, so that the pixel values above the saturation tolerance rate are saturated It is possible to prevent it.

In addition to the method of determining the dimming intensity shown in FIG. 6 as an example, the smaller the slope (51) and the smaller the brightness characteristic value (52) (the smaller the brightness characteristic value is, Or less than a certain brightness), and as long as the basic principle of dimming is adhered to, the various different decision schemes mentioned above may be implemented with different values than those illustrated in FIG. The present invention is not limited thereto. As clearly shown in the example of Fig. 6, the basic rule is naturally applied even under conditions where any one of the characteristic values is the same. That is, even if the brightness characteristic values of a plurality of unit images are the same, dimming is made more intense for a unit image having a small degree of inclination than for a unit image having a large degree of inclination, and for a unit image having a small brightness characteristic value, The way to increase dimming over this larger unit image is of course the above basic rule that must be observed.

When the dimming intensity is determined using any one of the various dimming intensity determination methods in which the basic rule is observed, the controller 10 determines a compensation coefficient corresponding to the dimming intensity, 12a. That is, if the determined dimming intensity is 0.2 (reduced to 80% of the currently set backlight brightness), a compensation coefficient of 1.25 (= 1 / 0.8) is set in the image processor 12a. The set backlight brightness may be a maximum brightness of the backlight 14a or may be a brightness specified according to a currently set video display mode (e.g., sharpness mode, standard mode, movie mode, sports mode, etc.) .

If the given unit image is for a block divided from one image, identification information (for example, position information on the frame) for the unit image is also notified. When such a compensation coefficient is set, the image processing unit 12a uses pixel values of a currently given unit image (image of a frame or a block) using its compensation coefficient (for example, by multiplying) . Of course, the output pixel values thus converted are converted into signals for adjusting the light transmittance of the corresponding pixels of the liquid crystal panel 14b corresponding to the respective pixel values by the display driver 12b.

The control unit 10 controls the brightness of a backlight region for supplying a light source to the entire or a partial area of the liquid crystal panel 14b in which the unit image is displayed so that the determined dimming intensity is applied. To the backlight 14a.

When the dimming intensity determined on the basis of the brightness characteristic value and the slope is applied according to the principle and the technical idea of the present invention and the compensation of the corresponding unit image is performed by the image processing unit 12a, Some pixel values in the unit image are saturated. However, for a given unit image, since the dimming intensity has been determined taking into account the slope in addition to the brightness characteristic value, a small gradient characteristic image and a small brightness characteristic value (in which the relatively bright pixel values are before the pixel value (Having a characteristic of shifting in a darker direction when viewed in the full range), the image having such a characteristic has a problem in that a relatively bright pixel value in the corresponding image is saturated, It is difficult for the user to intuitively experience such image quality loss. Therefore, in the case of an image of such a characteristic, the effect of reducing power consumption due to dimming is largely achieved, while at the same time reducing the light leakage phenomenon, in contrast to a slight decrease in image quality.

Even if the unit image having a large brightness characteristic value has a small slope, the image quality is relatively lowered due to the small slope even if the dimming is relatively strong as compared with the case where the slope is large. It is possible to obtain the same benefit (power consumption and light leakage reduction) that the dimming is strong even for the image.

In one embodiment of the present invention, as described above, the dimming intensity determined according to the brightness characteristic value and the inclination of a given unit image is adjusted by the inertia coefficient, for example, by multiplying the determined dimming intensity by the tolerability coefficient And the final dimming intensity may be applied to the brightness control of the backlight 14a.

The tolerance factor is basically a value of 1 (in this case, tolerance is not applied), but tolerance is applied according to the type and display method of the display panel 14, in which the input unit image is visually displayed It may be set to a non-1 value. For example, as to whether the display device is a TV or a monitor, or whether the display method is based on a LED light source or a quantum dot light source, The tolerance factor is predetermined and used corresponding to each of these types. For example, if the image quality degradation is a sensitive type, the affinity coefficient is a value smaller than 1 (when the dimming intensity is slightly decreased), and if the image quality degradation is insensitive, (If the previously determined dimming intensity is slightly increased). The user sensitivity to the image quality degradation for each type of display, display mode, and the like may be determined through experiments on each type, display mode, and the like.

In another embodiment according to the present invention, instead of correcting the determined dimming intensity, the previously described saturation tolerance may be changed and set according to the dependence coefficient determined for various schemes and types. For example, if the saturation tolerance should be set to be smaller than 1, the saturation tolerance may be set to a smaller value, and when the tolerance factor should be set to be larger than 1, the saturation tolerance may be set to a larger value have. Of course, in this embodiment, the inertia coefficient does not need to be set and used in the control unit 10. [ Alternatively, both the coefficient of inertia and the saturation tolerance may be set and used. In this case, the coefficient of inertia is used to correct the dimming intensity as described above, and the saturation tolerance can be used depending on the value of the settability coefficient. That is, as described above, the value of saturation tolerance can be designated in a manner inversely proportional to the coefficient of inertia, and can be used to grasp the brightness characteristic value.

In one embodiment according to the present invention, as described above, the dimming intensity determined based on the brightness characteristic value and the gradient of a given unit image may be selectively applied. In the present embodiment, when the dimming intensity determined by the brightness characteristic value and the gradient is not applied, the dimming intensity determined based on the maximum pixel value in a given unit image is applied. For example, if the maximum pixel value in a given unit image is 0.8, for example 0.8, the dimming intensity is determined to be 80% of the currently set backlight brightness.

In this embodiment in which the dimming intensity determined by the brightness characteristic value and the gradient of the image is selectively used, the algorithm illustrated in FIG. 7 is applied. Hereinafter, a method of determining the dimming intensity according to the algorithm illustrated in FIG. 7 will be described in detail do.

First, the control unit 10 determines whether a given unit image to determine the current dimming intensity has a homogenous characteristic (S601). In an exemplary embodiment of the present invention, it is determined whether a unit image has a homogeneous characteristic, and a distribution of pixel values in the unit image is a predetermined ratio of the range that pixel values can have, for example, 5% or 10% Based on whether it is concentrated within a section having a width. That is, when the pixel value is limited to a range of 5% when the pixel value has a range of 0 to 255, the pixel values in the unit image are all pV _Bot ~ 'pV _Bot + 12' (12 = 255 × 5% In the case where the pV _Bot is limited within the range of 10% within the interval of the pV _Bot , it is distributed within the interval of pV _Bot ~ 'pV _Bot +25' (25 = 255 × 10%) , The corresponding unit image is determined to have homogeneous characteristics. The distribution characteristic of the pixel values of a given unit image is grasped by the characteristic analyzer 11 and then the grasped distribution characteristic is transmitted to the controller 10 to be used for discrimination of the homogeneity characteristic.

In another embodiment according to the present invention, when the size of a given unit image is equal to or smaller than the predetermined number of pixels, the control unit 10 regards the unit image as having a homogeneous characteristic. For example, when a given unit image is a block having a size of 8x8 or 16x16, it is determined to have homogeneous characteristics. This is because, in an image corresponding to one frame of a video signal, a block of a small area, which is a size divided for image processing, generally has homogeneous image quality characteristics. In the present embodiment, when the characteristic analyzed and transmitted by the characteristic analyzer 11 is for a divided block of a predetermined size or smaller, the controller 10 does not consider the distribution of pixel values in the unit image It is judged that it has homogeneous characteristics.

If it is determined that the given unit image has no homogeneous characteristic, the control unit 10 determines the dimming intensity on the basis of the brightness characteristic value and the gradient of the image of the unit image in the manner described above, And is applied to dimming (S603).

If it is determined that the image has uniform characteristics, the controller 10 determines the dimming intensity based on the brightness characteristic value and the slope for the corresponding unit image, The dimming intensity is determined based on the pixel value (S602). Then, in step S610, it is determined which of the two dimming intensities is less, i.e., which of the dimming intensities is less, and which diminishes the brightness of the current backlight. , S612) to dim all or some of the area of the backlight 14a that will provide the light source for that unit image, with the selected dimming intensity, i.e., a relatively lower dimming intensity.

In one embodiment of the present invention, the dimming intensity determined according to any one of the methods described above may be corrected and applied to the brightness control of the backlight 14a. In the case of applying the correction, the degree of correction is determined based on the degree of brightness change between the unit images (for example, each frame of the moving image) which should be continuously displayed temporally. More specifically, if the change in brightness between consecutive images is large, the dimming intensity determined for the current unit image is greatly reduced or set to zero. If the brightness change is small, the determined dimming intensity is reduced to a minimum or the determined intensity is decreased It is left as it is. This is because, if the dimming intensity determined when the change in brightness between the unit images is large, the degree of the change is further increased, and the phenomenon of flickering of the image display screen may appear. Of course, the determined dimming intensity can be corrected only when the change in brightness of the current unit image with respect to the previous unit image becomes dark. That is, if the change in brightness between the units of temporal proximity is brighter than the previous unit image, the determined dimming intensity is applied without correction.

On the other hand, the degree of brightness change is determined based on the difference of APL (Average Picture Level) between temporally adjacent unit images, as in Equation [3].

APL ratio = (APL of current UI - APL of previous UI) / APL maximum value [3]

Here, UI is a unit image, and APL is an average value of pixel values (luminance, or values for one color element among color elements) of the corresponding unit image.

The control unit 10 receives the APL for each input unit image from the characteristic analyzer 11 and corrects the dimming intensity determined for the current unit image. 9A is a table showing one example of a rule for correcting (i.e., decreasing) the dimming intensity according to the present embodiment. 9A, if the APL of the current unit image is smaller than the APL of the previous unit image and the difference is in the range of 5 to 10% of the maximum value of APL (for example, 255), the determined dimming intensity (10%). For example, if the determined dimming intensity is a value that reduces by 20% from the current brightness of the backlight, the dimming intensity is corrected to a value that reduces 10% of the value, i.e., 18% , The brightness of the backlight is slightly increased according to the determined dimming intensity.

If the APL ratio falls within the range of 0% to -5%, the control unit 10 can adjust the dimming intensity to a predetermined value without correction It is applied to the brightness control of the backlight 14a. As mentioned above, when applying the criterion according to the table exemplified in Fig. 9A, even when the APL ratio is positive, the determined dimming intensity is applied to the brightness control of the backlight 14a without correction .

In one embodiment of the present invention, the dimming intensity determined according to any one of the methods described above is corrected based on the contrast sensitivity, and then the brightness control of the backlight 14a is performed It can also be applied. In the present embodiment, the characteristic analyzer 11 obtains a spatial frequency of pixel values belonging to the saturation intensities in a given unit image, and transmits the spatial frequency to the controller 11. Then, the controller 10 confirms whether the transmitted spatial frequency belongs to a band sensitive to the contrast change, and if so, reduces the dimming intensity determined previously and then applies the backlight 14a. More specifically, if the transmitted spatial frequency does not belong to the sensitive band designated to the controller 10, the correction is not made for the determined dimming intensity, and if the transmitted frequency is within the sensitive band, So that the determined dimming intensity is further reduced to be applied to the backlight 14a. That is, as the diminishing brightness change width approaches the center frequency, it decreases. This is to minimize such influence when the contrast sensitivity of the pixel values to be saturated by the dimming is high, since the influence of the image quality due to the dimming is relatively greater than when the contrast sensitivity is high.

In an embodiment according to the present invention, when the spatial frequency obtained for a given unit image is spaced by more than the reference bandwidth from a band susceptible to contrast change, the determined dimming intensity may be increased based on the frequency difference. That is, the brightness of the backlight 14a is made darker than when the obtained spatial frequency does not differ by more than the reference bandwidth. In this case, the greater the frequency difference, the greater the dimming intensity determined.

Heretofore, various methods for adaptively dimming the backlight according to the characteristics of the image have been described in detail. In the following, various methods according to the present invention, in which the backlight is adaptively boosted according to the given image characteristics, will be described in detail.

When the method of adaptively boosting the backlight according to the image characteristic is performed, the characteristic analyzing unit 11 of the apparatus illustrated in FIG. 2 grasps the distribution characteristic of the pixel values of the input unit image. At this time, the distribution characteristic to be grasped is information that allows the user to know how many pixel values exist for each value within a range that the pixel value can have, or what the relative ratio between the numbers is. The characteristic analyzing unit 11 transmits the distribution characteristic of the pixel values that the analyzing unit 11 grasps to a given unit image to the control unit 10.

The control unit 10 compares the distribution characteristic transmitted from the characteristic analysis unit 11 with a continuous distribution characteristic sample stored in advance. FIG. 9A schematically shows some examples of the continuous distribution characteristic samples stored in the control unit 10 as a graph. The continuous distribution characteristic samples exemplified in Fig. 9A satisfy each of the requirements described below in the distribution of the pixel values, and some of the input unit images are suitable for boosting (three in this embodiment) These are the distribution criteria chosen to distinguish them by type. Therefore, it should be understood that any distribution characteristic that is somewhat different from the one illustrated in FIG. 9A may be used as a continuous distribution characteristic sample in embodiments embodying the principles and concepts of the present invention, provided that the following requirements are met.

The first continuous distribution characteristic sample 81 illustrated in FIG. 9A satisfies the requirement that the pixel values corresponding to the bright portion are distributed relatively heavily. For example, when the range of values a pixel can have is divided into three sections (a list portion, a middle portion, and a dark portion), the first continuous distribution characteristic sample 81 has pixel values (For example, 40% or more of the total) in the first embodiment. A distribution characteristic sample having this characteristic is abbreviated as a 'bias sample'.

The second continuous distribution characteristic sample 82 has a characteristic in which the pixel values of the middle portion corresponding to the intermediate brightness satisfy the requirement of the largest distribution (for example, 40% or more) relative to the other intervals. The specimen of this characteristic is abbreviated as 'specimen of medium piece'.

The third continuous distribution characteristic sample 83 satisfies the requirement that the pixel values corresponding to the dark portions are distributed most in the intervals and more pixel values are distributed in the list than in the middle portion. The pixel values corresponding to the dark portion are, for example, more than 40%, and at the same time, the pixel values corresponding to the bright portion must exist more than the pixel values of the dark portion. A sample having such a characteristic is abbreviated as a 'sample of both sides'.

In a preferred embodiment of the present invention, the principle of the present invention is applied by dividing a range of values that a pixel can have into a plurality of sections and dividing them into a list part and a dark part. However, in the concrete implementation of the principle of the present invention, uniform division is not necessarily required. That is, the concept of boosting based on the distribution characteristic of the image according to the present invention can be applied even if the divided sections have different sizes.

The shape of each graph illustrated in FIG. 9A is merely an example, and as described above, other graphs (or distribution tables representing the shapes) that are somewhat different from the illustrated distribution types Can be stored in the controller 10 as a continuous distribution characteristic sample and can be used for determining the boosting intensity according to the distribution characteristic of the input unit image, that is, the brightness increase of the backlight, which will be described later.

The control unit 10 compares the distribution characteristic transmitted from the characteristic analysis unit 11 with a continuous distribution characteristic sample stored in the control unit 10 and calculates a distribution according to a difference in the number of distributions (or ratios) The separation is obtained in the same manner as the following equation [4].

Distribution spacing =

/ Total number of pixels in unit image [4]

Here, N _S (p) and N _R (p) represent the input distribution characteristic and the number (or ratio) of pixels having the pixel value p in the selected continuous distribution characteristic sample, respectively.

In Equation [4], absolute values are used to make the differences in the numbers or the ratios in the positive distributions compared to the arbitrary pixel values as positive numbers, but the absolute values are not taken, Any formula that makes the difference positive can be used. In addition, Equation [4] is only one example of finding differences in distribution, and one of various known methods that can quantify the difference in the pixel value distribution can be used instead of Equation [4] Of course.

The control unit 10 calculates the distribution distri- bution of each of the continuous distribution characteristic samples 81, 82, and 83 stored therein by the distribution characteristic, and then, Or less.

If there is more than one distribution spacing that does not exceed the limit value (which means that the distribution characteristic of the input unit image is more or less similar to the shape of the predetermined distribution characteristic sample) Obtains the pixel value concentration of the unit image within the representative interval designated by the distribution characteristic sample in which the distribution degree of the value is calculated. Here, the representative section refers to a section in which a relatively large number of pixel values are distributed in comparison with other sections in each of the above-described requirements, and is separately designated for each sample as illustrated in FIG. 9A, In the distribution characteristic sample 83 according to the third requirement, two representative intervals 83a and 83b are designated.

The control unit 10 uses a representative value designated for the representative section to obtain a pixel value concentration degree (hereinafter, abbreviated as 'concentration degree') within a designated representative interval. 9B, in the case of the three sections (arm section, middle section, and list section), for example, when the middle section corresponds to the representative section, the representative value is the middle value within the range (82a) When the value 84 corresponds to the representative section 83a, the value 84 is shifted to a lighter value in the middle 85a of the range (an assumption is made that the pixel value is 8 bits, (Any value within the range of 45 to 60), and when the list corresponds to a representative interval (81a, 83b), any value 86 shifted to the darker side in the middle (86a) For example, any value within the range of 195 to 210, assuming 8 bits).

Of course, a representative value for a corresponding interval may be designated in a manner different from the above example. For example, when the representative section is dark, the representative value may be used as a value shifted from the medium value to the dark side, and when the representative section is a list, the representative value may be used as a value shifted from the middle value to the bright side. The representative value designated for the representative section 81a of the named sample 81 and the representative value designated for the list side representative section 83b of the sampled example 83 may be different values.

Also, as mentioned above, according to the embodiment, since each section divided into the dark part, the bright part, and the like may have different sizes, the representative value can be appropriately selected according to the pixel value range belonging to the corresponding section.

Hereinafter, a method of obtaining the degree of concentration in the representative section of the input unit image using the representative value designated for each representative section will be described in detail.

If it is determined that the distribution characteristic of the input unit image is more similar to the out-of-sample sample 81 or the middle-piece sample 82 than a certain degree from the distribution distri- bution calculated as described above, It is determined how densely the pixel values of the image are within the representative interval 81a or 82a determined for the sample determined to be similar. To determine the degree of density, the concentration (cR) is calculated according to the following equation [5].

cR =

Equation [5]

Here, pN _sect is the number of pixel values distributed within the representative interval in the unit image, p _i represents the value of an individual pixel distributed within the representative interval, and p _Rep is a representative value assigned to the representative interval.

9C, the concentration cR calculated by the equation [5] is calculated by multiplying the designated representative value of the pixel values belonging to the currently considered representative section 880 among the pixel values of the input unit image Is the inverse of the sum of the distance difference (i.e., the pixel value difference) with the pixel value 881 divided by the number of pixels having the value in the representative interval (pN _sect ). In other words, the reciprocal of the average distance of the pixel values belonging to the considered representative interval from the designated representative value is the concentration (cR).

If the spaced average distance is short (i.e., smaller), it means that the pixel values of the unit image within the representative interval are densely packed around the designated representative value 881 (87a in the distribution graphs 87a and 87b in FIG. 9C) , And when the average distance is long (that is, when it is large), it means that it is relatively discrete distribution (87b among the distribution graphs 87a and 87b in FIG. 9C) centered on the representative value 881. That is, the average distance from the designated representative value reflects the density of the distribution centered on the representative value.

In another embodiment according to the present invention, in order to grasp the degree of crowding in the interval of pixel values, there are a method of obtaining the deviation or variance of various known methods without obtaining the average distance from the representative value as described above, One method or a plurality of methods selected from the methods of obtaining the characteristics of the first and second embodiments may be combined and used.

The reason for taking the reciprocal of the average value of the distances in obtaining the concentration (cR) is to make a variable indicating a characteristic that the higher the degree of density densification around the representative value becomes (882), the greater the value. However, it is not necessary. This will be briefly mentioned later.

If the distribution of the input unit images calculated for both samples 83 is less than the predetermined threshold value (that is, if the distribution characteristics of the unit images are similar to the sample 83 of more than a certain degree) The control unit 10 compares the concentration (cR _D , cR _B ) of each unit of the unit image with respect to each of the two representative intervals 83a and 83b specified in the sample 83 on both sides according to equation [5] I ask. The weighting factors cR _D and cR _B are obtained by the weighting factors cR _d and cR _B , respectively, to obtain the concentration (cR =? _D x cR _D +? _B x cR _B , where? _D +? _B = 1). In obtaining the degree of concentration from the degree of concentration in both sections, the weight value (? _D ) of the ratio reflecting the section concentration degree (cR _D ) calculated for the arm side representative section (83a) ) has a value greater than the weight (β _B) of a ratio reflecting the interval concentration (cR _B) can be calculated for. This is because the density of the pixel values in the dark-side representative section 83a is more reflected in the degree of concentration.

When the degree of concentration cR is obtained as described above, the control unit 10 determines the boosting control value based on the degree of concentration. When the degree of concentration is large (that is, the higher the density of pixel values in the representative period is ), The boosting control value is determined according to the rule that the boosting control value becomes a larger value. For example, a method of linearly or non-linearly proportional to the obtained concentration, or a method of stepwise increasing can be applied to determination of the boosting control value. Of course, if the concentration cR is lower than a predetermined threshold (in other words, if the density within the considered representative interval is less than an appropriate level), the controller 10 may determine the boosting control value to be 0 have. That is, the current brightness can be maintained without boosting the backlight for the unit image. This is because, in the case of a unit image having a distribution characteristic in which such a degree of concentration is obtained, power is further consumed by boosting, but there is little effect of image quality improvement or image quality is likely to be distorted.

As mentioned above, the average distance from the representative value, which indicates the degree of density of pixel values in the representative section, can be applied as the degree of concentration without taking a reciprocal number. Of course, in this case, the boosting control value is determined according to the rule that the boosting control value becomes larger as the concentration becomes smaller. Even if this method is applied, the basic principle of the present invention in which the boosting control value is determined to be a larger value as the density of the image pixel values in the representative section is higher (i.e., the backlight brightness is further increased) do.

When there are two or more distributed characteristic samples for which a value lower than a predetermined threshold is found, the control unit (10) (F_cR) is obtained by interpolating the degree of concentration obtained for the representative section (or the plurality of representative sections) in each sample as shown in the following equation [6] to determine the final concentration (f_cR) Value may be determined.

f_cR =

Equation [6]

Here, M is the number of distribution characteristics sampled below the threshold value, cR _i is the concentration obtained for the representative section (or representative sections) of each distribution characteristic sample, and δ _i is the reflection coefficient δ ₁ +隆₂ + .. + 隆_M = 1.

Although the reflection coefficients (? _I ) may have the same value (that is, the final concentration can be obtained by uniformly reflecting each concentration), the reflection coefficient (? _I ) may have different values depending on the obtained distribution spacing. In the latter case, the control unit 10 determines whether or not the reflection coefficient calculated on the degree of concentration obtained on the basis of the distribution characteristic sample (i.e., the distribution characteristic of the input unit image having a similar distribution characteristic) in which the relatively small distribution is obtained It is used to calculate the final concentration by dynamically allocating it to be a large value.

According to another embodiment of the present invention, when distribution distances from a plurality of continuous distribution characteristic samples prepared in advance to an input unit image are obtained, distribution characteristic samples in which a value lower than a predetermined threshold value is obtained, If there is a distribution characteristic, the degree of concentration of the unit image is obtained for each representative section (or representative sections) in each distribution characteristic sample, and the boosting control value is obtained according to the above-described rule for each obtained concentration degree. The final boosting control value may be obtained by interpolating each boosting control value and applied to the brightness of the backlight 14a. Of course, the method of obtaining the final boosting control value from each boosting control value can be performed in the same manner as in Equation [6]. In other words, the concentration variable can be replaced by the boosting control variable in Equation [6].

In another embodiment according to the present invention, the above-described distribution distri- bution may be obtained from the difference between the reference ratio and the numerical reference ratio, which is divided into the reference intervals. 10 is a diagram illustrating an example of each of the section distribution characteristics 90 that can be used to calculate the distribution spacing in the present embodiment. The section 90 has a reference ratio This figure is presented. These numbers are, of course, exemplary only, and other values may be used. However, even if the distribution characteristic samples using different values as the reference ratios, the requirement for the pixel value distribution as mentioned in the description of the example of Fig. 9A must be met.

10, the control unit 10 divides the distribution characteristics transmitted from the characteristic analyzing unit 11 by a predetermined interval and calculates a distribution ratio of each interval , And then calculates the difference from the reference ratio of the corresponding interval to each of the samples 90 of the interval distribution characteristic 90. (Of course, appropriate calculation is added if necessary to obtain a positive value for this difference.) The difference The distribution spacing is obtained by summing. As described above, when the distribution spacing is obtained for each of the interval distribution characteristic samples 90, the representative interval (or representative intervals) of the input unit image is calculated in consideration of the angular distribution of the angular distribution, The degree of compactness is determined, and the boosting control value is determined accordingly. Of course, the representative values in the representative interval in each of the interval distribution characteristic samples illustrated in FIG. 10 are determined as illustrated in FIG. 9B and used to obtain the concentration.

In the embodiments according to the present invention described above, it was confirmed that the distribution characteristic of the unit image is similar to the distribution characteristic sample before the concentration of the input unit image is obtained. That is, as described above, a representative interval (or a representative interval) for determining the degree of concentration of a pixel value of a unit image on the basis of the distribution distri- bution Representative sections) were selected.

In another embodiment according to the present invention, the boosting control value for a unit image can be determined without obtaining the distribution spacing. In this embodiment, the control section 10 is provided with a continuous distribution characteristic criterion. The continuous distribution characteristic criterion that is provided in advance is selected from among the distribution characteristics that satisfy the above-described requirements for the continuous distribution characteristic sample and at the same time, image quality improvement is most conspicuous by boosting. The continuous distribution characteristic reference chart, like the distribution characteristic sample illustrated in FIG. 9A, is a diagram showing the distribution of pixel values distributed in the list, the distribution centered on the middle portion, Each is specified for the biased form.

However, as described above, as the degree of density in the representative interval in which the pixel values are relatively more widely distributed in the pixel value distribution is higher, the image quality is remarkably improved by the boosting. Therefore, , Unlike the distribution characteristic samples illustrated in FIG. 9A, the distribution of the pixel values has a very dense form with arbitrary representative values within the biased representative interval.

The control unit 10 calculates a distribution characteristic of each unit of the continuous distribution characteristic standard according to the following equation [7] with respect to the distribution characteristic of the unit image transmitted from the characteristic analysis unit 11, To calculate the boosting fitness.

Boost Fit =

Equation [7]

Where SECT_N is the number of periods of uniform or unequal size (eg, list, middle, and dark portions) divided for the selected continuous distribution characteristic criteria, SECT (i) _INIT, SECT (i) _MAX, and The pDIST (i) sequentially calculates the minimum pixel value in the corresponding interval (i-th interval), the maximum pixel value in the interval, and the distance between the minimum pixel value and the maximum pixel value in the interval For property criteria, if each interval is divided equally, this value will have the same value for each interval). N _S (p) and N _OD (p) represent the input distribution characteristic and the number (or ratio) of pixels having the pixel value p in the selected continuous distribution characteristic reference, respectively. Finally, μ _i is the weight applied to the interval, and satisfies the relation μ ₁ + μ ₂ + .. + μ _{SECT_N} = 1.

In [7], the mean value of the differences between the distributions of the pixel values of the inputted unit image and the selected continuous distribution characteristic criterion is obtained for each of the divided intervals of the pixel value distribution of the inputted unit image, the weight is calculated on the reciprocal of the average value, And the result of the operation obtained for the section is added to obtain the boosting fitness. Equation [7] is only one example of finding the boosting fitness by dividing by intervals, and the difference between the distributions of the intervals is obtained, and the weights are applied to the difference between the intervals to obtain the final distribution difference (i.e., the boosting fitness) The method may be used instead of Equation [7].

In Equation [7], the smaller the denominator is, the smaller the denominator becomes, the smaller the difference between the distribution characteristics of the input unit image and the distribution characteristic criterion is, the larger the value of Boosting Fit obtained by Equation [7] becomes . Accordingly, the similarity of the distribution characteristic of the input image to the predetermined distribution characteristic criterion results in a higher value of the boosting suitability.

In an embodiment according to the present invention, in Equation [7], the weight (mu _i ) may not be used. That is, the average of the differences of the distribution numbers obtained for the respective intervals may be reflected at the same ratio to obtain the boosting fitness.

In another embodiment according to the present invention, the weighting factor ( _i ) may be applied to calculate the boosting fitness by designating different weights for each interval. In the present embodiment, for the representative interval designated for the distribution characteristic criterion to be compared, a weight value that is larger than the weight value assigned for the other interval is allocated and used. This is to reflect the difference in the number of distributions in the representative section more greatly when the boosting fitness is obtained. As a specific example, assuming that the entire range of the pixel value is divided into three sections, in the case of the distribution characteristic reference specified for the distribution form concentrated on the list and the distribution characteristic standard designated for the distribution form concentrated on the middle portion, The weight for the interval may be set to 0.6, and the remaining interval may be allocated to 0.2. In the case of the distribution characteristic criterion specified for a distribution type that is more concentrated in the dark portion than in the dark portion, the ratio is 0.5 for the representative portion of the dark portion, 0.35 for the representative portion of the list, and 0.15 for the remaining portion It is possible.

The control unit 10 selects a boosting fitness value having the largest value among the boosting fitness values obtained by comparing each of the continuous distribution characteristic criteria. Then, the boosting control value is determined based on the selected boosting fitness, and the boosting control value is determined according to the rule that the boosting control value becomes larger than when the boosting fitness is small.

Each continuous distribution characteristic standard stored in the control unit 10 has a strong characteristic that the pixel values in the representative interval in which the pixel values are most significantly included in the image, (I.e., the value of the boosting fitness is large) in the pixel value distribution, the distribution characteristics of the input unit images are also compared with the distribution characteristics Similar to the reference, it means that the pixel values are concentrated around the representative value. Therefore, since the unit image in which the boosting fitness of a large value is obtained is likely to greatly improve the image quality by boosting, the above-described rule is applied.

On the other hand, the controller 10 may determine the boosting control value to be 0 if the boosting fitness calculated as described above is equal to or less than a predetermined threshold value. That is, the current brightness can be maintained without boosting the backlight for the unit image.

In one embodiment of the present invention, the distribution characteristic of the input unit image is determined by selecting one of the largest values among the boosting fits obtained through comparison with each continuous distribution characteristic criterion, , The final boosting fitness to be used for determining the boosting control value may be obtained by interpolating the boosting fitness values. That is, each boosting fitness is multiplied by a weight and then added to obtain a final boosting fitness, and the boosting control value is determined based on the final boosting fitness. The weights computed for each boosting fitness may be the same as each other, but may be different values such that the weight applied to the larger boosting fitness is also a relatively large value.

According to another embodiment of the present invention, when there are two or more boosting fitness values that are equal to or higher than a predetermined reference value, the boosting control value corresponding to each boosting fitness is obtained, and then the boosting control values are interpolated to determine the brightness of the backlight 14a The final boost control value to be applied may be determined.

The boosting control value determined in accordance with any one of the various methods described above may be set such that the intensity of the light source with respect to the corresponding area (all or a part) of the backlight 14a Is set to be brighter than the currently specified value. Therefore, when a large value of boosting control value is set, a brighter light source is provided for display of the unit image than when a small value is set.

Meanwhile, when determining the boosting control value according to the degree of concentration or the boosting fitness calculated as described above, the control unit 10 determines the maximum boosting control value when the concentration or the boosting fitness becomes equal to or higher than a predetermined limit value. The boosting control value is determined according to the following method.

The control unit 10 determines a boosting control value for a unit image having a distribution characteristic in which image quality improvement effect by boosting is most conspicuous, that is, a maximum boosting control value, Function or table. Here, the boosting ratio means a ratio of the brightness when boosted to the brightness currently set in the backlight 14a. 11 is an example of the function 1000 showing the enhancement characteristics of image quality versus the boosting ratio. 11, when the brightness of the backlight is increased, the contrast with respect to the image increases and the image quality is improved. However, at a certain boosting rate, the power consumption is increased by the boosting The contrast is saturated and the image quality is not improved as much as the boost ratio is increased (i.e., the power is consumed more). The function or table showing the characteristics as illustrated in FIG. 11 may be determined according to the characteristics that are grasped or experimentally confirmed with respect to the liquid crystal panel 14b, and may be stored in the controller 10.

The controller 10 determines the maximum boosting control value based on the function 1000 or the table for the boosting-image quality relationship characteristic, which is shown in FIG. 11, showing the relationship of image quality improvement by boosting And can be determined using any one of the following two methods.

The first method is based on the efficiency of the improvement of picture quality of power consumed by boosting. Boosting requires additional power consumption, the first approach is to find the boosting ratio that is the highest or the best improvement in picture quality over the additional power consumption. In order to find the boosting ratio in accordance with this method, the control unit 10 starts at a predetermined maximum boosting ratio (for example, 2.0) and calculates a boosting ratio by a predetermined ratio interval (? BR_D _STEP , From the function 1000 or the table for the boosting-image quality relationship characteristic, for example, by decrementing (step 1010) and decreasing (? IQ_D _STEP ) by how much the image enhancement is decreased. The control unit 10 finds a specific boosting ratio value 1020 which is gradually increased and then decreases (? _K >? _{K + 1} ). As described above, this process is a process of finding the boosting ratio having the highest image enhancement ratio in the section where the image enhancement is higher than the predetermined standard (1001). When the specific boosting ratio value 1020 is found by this method, a value obtained by subtracting 1 from the ratio is determined as the maximum boosting control value. Of course, as described above, when the concentration or the boosting fitness calculated above is within the predetermined limit with respect to the maximum boosting control value thus determined, the adjustment is made according to the above-described rule, that is, to a smaller value to boost the backlight And when it exceeds the limit value, the maximum boosting control value is directly applied to the backlight boosting.

For a general display device employing an LCD or the like, when the first method described above is applied, the boosting ratio at which the power efficiency becomes the highest is generally set at 1.6 (i.e., the boosting intensity is 60% of the current intensity) . Therefore, in the embodiment of the present invention, when the boosting control value is determined based on the power efficiency by boosting, the value is determined to be 1.6 or a value adjacent thereto. That is, the maximum boosting control value is determined by a value that increases the current backlight brightness by, for example, 60% × (1 ± 0.05). When power efficiency by boosting is determined, depending on how the unit width of the boosting ratio is set and tested, power efficiency by boosting may be maximized at a different ratio around 1.6 instead of 1.6. Thus, an increment of one value (a value corresponding to a specific ratio within 50% to 70%) in a range centered on that value, for example, a range of 1.5 to 1.7 in the boosting ratio, May be designated as the maximum boosting control value and applied to the brightness control of the backlight 14a.

The second method of determining the maximum boosting control value is to prioritize image quality enhancement and finds a boosting rate at which image quality is not further improved even if the boosting rate increases, that is, a boosting rate at which the image quality is improved to a maximum value. The human eye does not perceive linearly the increase in brightness measured physically and hardly recognizes the change in brightness when the brightness change exceeds a certain threshold, which is to find the boosting rate so. In order to find this boosting ratio, the control unit 10 starts, as before, starting from a pre-specified maximum boosting ratio (for example, 2.0), as shown in FIG. 11, by a predetermined ratio interval (? BR_D _STEP (1010), thereby decreasing the picture quality improvement, in the function (1000) or table for the boosting-picture quality relationship characteristic. If a point at which the picture quality improvement decreases (or decreases by more than a specified threshold) is found, the boosting ratio value 1030 corresponding to the point immediately before the picture quality improvement is reduced is regarded as the maximum boosting ratio when the picture quality is prioritized, The value obtained by subtracting 1 from the boosting ratio value 1030 is determined as the maximum boosting control value.

Of course, the maximum boosting control value obtained using this second method is also calculated for a given unit image and adjusted according to the selected concentration or boosting fidelity, as in the first method described above. That is, when the degree of concentration or the boosting fitness calculated for a given unit image is within the limits described above, a value adjusted in accordance with the above-described rule in the maximum boosting control value determined as described above, This is applied to the boosting of the backlight.

In one embodiment according to the present invention, as described above, without determining the maximum boosting control value according to the first or second method from the function 1000 or the table for the picture quality enhancement characteristic versus the pre-stored boosting ratio, The maximum boosting control value set by the controller 10 is stored in the controller 10 and may be selectively used for determining the boosting control value according to the calculated concentration or boosting fitness. That is, when the concentration or boosting control value calculated above is greater than or equal to the limit value, the stored maximum boosting control value is used. Otherwise, the boosting control value adjusted to a smaller value is used according to the above-described rule. At this time, when the power efficiency should be prioritized, when the pre-stored maximum boosting control value determined by the first method has priority over image quality improvement, it is determined by the second method, Value is selected and used.

On the other hand, in the embodiment of the present invention, even when the boosting control value determined in the above-described manner has a value larger than 0, that is, even if it is decided to provisionally boost the unit image, May have a special characteristic, it may be verified whether the boosting is to be finally performed. The special characteristic here is that the high luminance pixel values in the unit image, for example, pV _MAX to pxV _MAX (where 0.90?? <1 and pV _MAX is the maximum value the pixel can have) Or 15% or 20% or more of the pixel values belonging to the list in the evenly divided three sections as illustrated in FIG. 10 belong to the high brightness range as shown in the above example . Even if the boosting control value larger than 0 is determined for a given unit image, the control unit 10 does not boost the backlight 14a finally if the unit image has the special characteristics described above. This is because, even if the image of such a characteristic is boosted, not only the human eye can perceive the difference due to the boosting in the high luminance portion but also the brightness is saturated by the boosting, .

In another embodiment according to the present invention, boosting may be performed even when a given unit image has the above-described special characteristics. However, in this case, the determined boosting control value is corrected, that is, decreased and applied. For example, the determined boosting control value can be reduced by 25% or 50% and applied to the boosting of the backlight.

In one embodiment of the present invention, the above-described operation of checking or correcting the application of boosting, even though a boosting control value of greater than zero is determined, Or when the difference in the number of distribution with respect to the distribution characteristic criterion specified for the distribution form biased in the middle portion in reflecting the degree of density of the pixel value in the image 82a is reflected, The determined boosting control value is directly applied to the backlight 14a without being verified for correction or application, and if it is not reflected, verification for boosting application or compensation for the determined boosting control value is performed . As described above, the verification or correction (reduction) of the boosting control value before finally applying the boosting is performed when the ratio of the pixel values belonging to the list in the given unit image is higher than the pixel values in the middle portion Boosting, high luminance pixel values are saturated, and image quality deterioration may occur, in order to eliminate or reduce such a possibility.

In one embodiment of the present invention, the correction is made in the same manner as the correction according to the APL of the unit image described for the backlight dimming, on the boosting control value determined (or corrected and determined) by the above-described method, It may be applied to the control of the light intensity of the backlight 14a. The rule for correcting the determined boosting control value is the same as the rule described with reference to Fig. That is, if the rate of change in brightness between consecutive images, for example, the ratio of APLs between the two images, is large, the boosting control value determined for the current unit image, i.e., the boosting intensity is greatly reduced, and if the rate of change in brightness is small, . Of course, the correction according to the change in brightness between successive images may be performed only when the brightness of the current unit image with respect to the previous unit image is relatively bright.

In an embodiment according to the present invention, when there are many pixels belonging to the dark portion in a given unit image, correction may be performed to reduce the boosting control value, i.e., the boosting intensity, determined in advance. Since the human eye has the characteristic of recognizing the change in the dark part more sensitively even if the brightness change is the same brightness, when the corresponding part of the dark part boosts a relatively large unit image, the brightness change is relatively large So that image quality distortion can be experienced. Therefore, in order to suppress the occurrence of such image quality distortion phenomenon in the present embodiment, the previously determined boosting intensity is corrected based on the ratio of the dark pixels below the predetermined brightness in a given unit image. FIG. 12 is a table numerically illustrating an example of a correction rule of the boosting intensity that can be applied to the present embodiment.

When applying the correction reference rule illustrated in FIG. 12, the control unit 10 determines whether or not the predetermined brightness (in the case where the brightness is represented by 8 bits , For example, 50), and if the ratio is 38% or more, the boosting control value determined for the unit image is reduced by 20%, and if the ratio is within the range of 25% to 38% 10%, and when it is in the range of 14% to 25%, it is reduced by 5% and then applied to the boosting control of the backlight 14a. If the detected ratio is less than 14%, the intensity of the current light source of the backlight 14a is increased according to the control value without correcting the determined boosting control value.

In an embodiment according to the present invention, the boosting intensity may be corrected according to the spatial frequency, which is one of the image characteristics, as in dimming. In the present embodiment, the characteristic analyzer 11 obtains the spatial frequency of a given unit image and transmits the spatial frequency to the controller 10. Then, the control unit 10 checks whether the transmitted spatial frequency belongs to a band sensitive to a contrast change or how far from the band it is, and, based on the confirmed result, And then applied to the backlight 14a. More specifically, if the transmitted spatial frequency does not belong to the sensitive band designated to the control unit 10, it is directly applied without correction for the determined boosting intensity. If the transmitted spatial frequency belongs to the sensitive band, The closer to the center frequency, the greater the determined boosting intensity is applied to the backlight 14a. When the spatial frequency is separated from the sensitive band by more than a predetermined reference bandwidth, the previously determined boosting intensity may be reduced based on the frequency difference to be applied to the backlight 14a. The reason for this correction is that when the contrast sensitivity of the unit image is high, the image quality due to boosting is relatively larger than when the contrast sensitivity of the unit image is high, so that the image quality can be maximized through such influence.

In an embodiment according to the present invention, unit images of the same spatial frequency within the sensitive band may be increased in size when the intensity of boosting is corrected according to their pixel value distribution. For example, when the pixel values are divided into sub-regions, when the number of pixel values distributed in the bright region is relatively larger, the boosting intensity is increased to a relatively larger value than when the pixel values are not otherwise do. This is because the higher the brightness, the more the image quality is affected by boosting.

As described above, the correction for increasing the boosting intensity as the spatial frequency approaches the contrast sensitive band can be applied to a video output environment in which image quality enhancement should be prioritized. If the situation requires more power saving than image quality improvement, for example, the user may set the image quality preference rather than image quality improvement, or the principles and concepts of the present invention apply, In the case where the display device having the configuration as described is a portable device or the like in which the power consumption is to be reduced as much as possible, correction of the boosting intensity based on the spatial frequency of a given unit image can be performed in the reverse direction as described above. In other words, if the spatial frequency of a given unit image belongs to the contrast sensitive band designated by the controller 10, the closer the center frequency of the band is to the center frequency of the band, the greater the determined boost intensity is applied to the backlight 14a do.

Up to now, several embodiments have been described in which the boosting control value, i.e., the boosting intensity determined according to the pixel value distribution characteristic of a given unit image, is corrected and applied. The correction methods of the above-described boosting intensity do not necessarily have to be selected and applied. In other words, among the several correction methods described above, a plurality of methods may be applied multiply to correct the determined boosting intensity based on the image quality enhancement rate or based on the power efficiency by boosting, depending on the distribution characteristic of the unit image It is possible. That is, assuming that the boosting intensity determined for a given unit image is Bst_I _Init , the ratio corrected by the selected one of the correction methods described above is? 1, and the ratio corrected by the selected other method is? 2 , The boosting intensity is finally determined to be Bst_I _Init x (1 - alpha 1) (1 - alpha 2) or Bst_I _Init x {1- (alpha 1 + alpha 2)} and can be applied to the boosting of the backlight.

As a method that can be applied when determining the boosting control value according to the pixel value distribution characteristic of a given unit image, a first method of determining based on the power efficiency by boosting and a second method of aiming at improving the maximum image quality are described . These two schemes may be used exclusively of one another, that is, only one scheme may be selected and used to control the boosting of the backlight, but may be used in combination with each other. In other words, the first boosting control value is obtained based on the power efficiency and the second boosting control value is obtained based on the maximum image quality improvement with respect to the concentration or the boosting fitness calculated for the given unit image, The optimal boosting control value Op_BstCv may be determined by reflecting a predetermined ratio of the value to the boosting rate of the backlight 14a as shown in Equation [8].

Op_BstCv =? 1 × first boosting control value + δ2 × second boosting control value expression [8]

Here,? 1 +? 2 = 1.

Of course, in this embodiment, at least one of the above-described various correction methods may be applied to the determined optimum boosting control value, and then finally applied to the backlight boosting. Alternatively, each of the corrected boosting control values obtained by applying the appropriate one of the various correction methods described above to the first and second boosting control values may be reflected by the specified angular rates? 1 and? 2, The boosting control value may be calculated.

In one embodiment of the present invention, the values of the reflection ratios delta 1 and delta 2 may be determined according to a preference of a user applied through the input control unit 15 and used. For example, if the user prefers to improve the image quality rather than the power efficiency, the control unit 10 sets the reflection ratio? 1 of the first boosting control value to 0.25, the reflectance ratio? 2 of the second boosting control value, (For example, δ1 = 0.75, δ2 = 0.25) can be determined when power efficiency is preferred rather than image quality improvement.

If the user does not designate a particular preference, the reflection ratio may be set to 0.5, but may be set to a value that is not equal to each other reflecting the physical characteristics of the liquid crystal panel 14b. For example, if the contrast expression capability of the liquid crystal panel 14b is relatively good, the reflectance ratio? 1 of the first boosting control value is set to a value smaller than the reflectance ratio? 2 of the second boosting control value (For example, when the consumed power is to be reduced due to the limited electric energy capacity), the second boosting control value should be less than the reflectance ratio? 2 of the second boosting control value It can also be set to a large value.

The term 'pixel value' used in the present specification may be the luminance of a given pixel or the value of any element in each color element (R, G, B), as mentioned above . Therefore, it is possible to determine the light source control value (i.e., dimming intensity or boosting intensity) with respect to the overall characteristics of the pixel values of a given unit image, that is, the brightness characteristic value and the gradient, , The method of controlling the brightness of the backlight can be applied not only to the luminance by the three primary colors (R, G, B) but also for each element of the three primary colors. Of course, in this embodiment, the brightness characteristic value for the unit image including only the values for the color element is determined from the distribution of the values themselves as described with reference to FIG. 5 to determine the dimming intensity. In this embodiment, of course, a backlight is also provided for each color element, and the controller 10 sets the dimming intensity or the boosting intensity determined in the above-described manner for a unit image of an arbitrary one- It is applied to the corresponding region of the backlight of the corresponding color element. In the case of dimming the backlight, as described above, compensation coefficients corresponding to the dimming intensities of the color elements are determined and notified to the image processing section 12a, and picture quality compensation is performed for the color elements in accordance with dimming Respectively.

Only one of the methods of backlight dimming and boosting based on the image characteristics described so far may be applied to the display device, but both methods may be applied to one display device. In this case, the control unit 10 first determines whether to perform backlight dimming or boosting for a given unit image.

If dimming and boosting are applied together, it is determined whether or not dimming is a suitable unit image for a given unit image based on the brightness information provided from the characteristic analyzer 11, and if not appropriate, 11 based on the distribution characteristics of the pixel values of the unit image provided from the unit pixels. For example, if it is determined that it is appropriate to apply dimming when the brightness, i.e., the brightness, of the unit image is darker than the specified brightness level reference value, for example, 45% of the maximum brightness, At the same time, if the degree of concentration or the boosting fitness calculated for the unit image is equal to or higher than the predetermined threshold value, applying boosting is determined as an appropriate image. Of course, for a unit image which is determined not to be suitable for dimming or boosting, for example, a unit image having a brightness higher than the brightness level reference value and at the same time a concentration or a boosting fitness determined to be lower than the threshold value, So that the intensity of the light source currently set in the light source 14a is maintained.

On the other hand, the dimming intensity for the unit image determined to be suitable for dimming is determined according to the brightness characteristic value or the slope of the unit image, as described above. That is, when the brightness characteristic value is small, the dimming intensity is larger than when it is large, and when the slope is small, the dimming intensity is determined to be larger than when it is large. Also, the intensity of the boost for the unit image determined to be suitable for boosting is determined according to the degree of concentration or the boosting fitness calculated for the unit image as described above. That is, if the concentration or the boosting fitness is large, the boosting intensity is determined to be larger than when it is small.

As described above, when backlight boosting is applied together with dimming, power is additionally consumed by boosting, but power is reduced through dimming. Thus, embodiments of both methods of applying the present invention to both methods of the present invention can improve the image quality of the image through dimming and boosting without consuming a relatively large amount of power, compared with maintaining the original brightness of the backlight.

In one embodiment according to the present invention, it may be possible to statistically increase the dimming compared to boosting, or vice versa, for consecutively given images, depending on the user preference. For example, when the user requests a relatively high power saving through the input control unit 15, the controller 10 sets the aforementioned brightness level reference value for discriminating as an image suitable for dimming, By adjusting to a large value, more dimming is statistically made in the display device. In an embodiment of the present invention, when a relatively high power saving is requested, the threshold value for the degree of concentration or boosting fitness at which boosting is performed may be set to a larger value so that the proportion of images boosted is relatively reduced It is possible.

The various schemes described in detail in the above embodiments accompanied by the method of dimming the backlight or the method of boosting according to the characteristics of the image can be properly combined and implemented together as long as they are incompatible with each other.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. , Alteration, substitution, addition, or the like.

10: main control unit 11: characteristic analysis unit
12: Signal conversion section 12a:
12b: display driver 14: display panel
14a: backlight 14b: liquid crystal panel
15:

Claims

An apparatus for visually expressing a video signal,
A backlight providing a light source,
A panel for outputting a visual signal by adjusting a transmittance of the light source according to a gray level value of each input pixel;
An analyzing unit for analyzing a distribution characteristic of the input gray-scale values of the unit image,
A gray level value of each pixel in the unit image is output as a visual signal based on the density of the detected distribution characteristic in at least one of the plurality of intervals divided for the range that the gray level value can have The intensity of the light source provided in the area of the panel is determined to be an intensity that is greater than the currently set intensity and is applied to the backlight and when the density is high, And a control unit configured to apply,
And a signal processing unit configured to convert a gray-scale value of each pixel in the unit image into a signal that can be visually displayed by the panel, and to apply the converted gray-scale value to the panel,
Wherein the control unit controls the density of the grasped distribution characteristic centered on the first reference value and the third reference value in the darkest interval and the brightest interval among the plurality of intervals, A density state of the grasped distribution characteristic centered on a second reference value in a section and a density state of the grasped distribution characteristic centered on the third reference value in the brightest section among the plurality of sections And to grasp the degree of densification from at least one densified state.

delete

The method according to claim 1,
Wherein the control unit includes a first distribution sample in which the gray level values distributed in the brightest interval are largest compared to other intervals and a second distribution sample in which gray level values distributed in the interval of the middle brightness are largest in comparison with other intervals, The gray level values distributed in the darkest interval are the largest and the gray level values distributed in the brightest interval are larger than the interval of the middle brightness, And the disturbance degree from each distribution sample is calculated and the at least one densest state which is to grasp the degree of densification based on the calculated disturbance is selected.

The method according to claim 1,
Wherein the control unit is configured to grasp the degree of densification by reflecting each densified state according to a given ratio when the at least one densest state is a plurality.

5. The method of claim 4,
Wherein the control unit allocates, for the given ratio, a value that is greater than a ratio reflected in a dense state in which dense dense dense dense dense dense dense denominator dense dense dense dense dense dense dense dense dense dense dense dense dense dense dense dense dense dense uniform Wherein the display device is configured to grasp the degree of density.

The method according to claim 1,
Wherein the control unit grasps the degree of compactness based on at least one difference among each of the distribution differences obtained by comparing the obtained distribution characteristics with respect to each of the plurality of distribution criteria provided, The degree of density is higher,
The distribution criterion may include a requirement that grayscale values distributed in the brightest interval among the plurality of intervals be the largest compared to other intervals and that the grayscale values distributed in the interval of the medium brightness among the plurality of intervals are compared with other intervals And the requirement that the gray level values distributed in the darkest interval among the plurality of intervals are larger than those of the other intervals and that the gray level values distributed in the brightest interval are larger than the interval of the middle brightness Respectively. &Lt; / RTI >

The method according to claim 1,
Wherein the control unit determines the increased intensity based on the efficiency of the power of the power consumed by increasing the intensity of the light source when determining the increased intensity according to the density,
In the portion where the image quality of the boosting-image quality characteristic that the image quality of the image increases as the intensity of the light source increases, the maximum value that the increased intensity determined by the controller can have becomes equal to or higher than the predetermined reference, Wherein the enhancement factor corresponds to an increase in the intensity of the light source that has the highest enhancement rate of the image enhancement ratio with respect to the increase rate of the intensity.

8. The method of claim 7,
Wherein the maximum value that the increased intensity can have is a value that falls within a range of 50% to 70% of the currently set intensity.

The method according to claim 1,
Wherein the controller determines the increased intensity based on the specific increase in the intensity of the light based on the improvement in quality when determining the increased intensity according to the density,
The specific increment may be a value that increases the intensity of the light source so that in any boosting-image quality characteristic that the image quality is improved, the image quality is no longer improved even with increasing light source intensity, Of the intensity of the light source.

The method according to claim 1,
The control unit controls the backlight so as to reduce the determined increased width and to apply the increased intensity according to the correction, when the high luminance tone values become the predetermined ratio or more out of the tone values of the unit image Or to maintain the current set strength without reflecting the determined increased width,
Wherein the high brightness gradation values are values equal to or larger than a predetermined ratio of a maximum gradation value that a pixel in the unit image can have, and the predetermined ratio is set in a range of 90% or more and less than 100%.

11. The method of claim 10,
Wherein the control unit corrects the determined increased intensity when the densified state of the detected distribution characteristic is not reflected on the basis of the reference value in the interval of the middle brightness among the plurality of intervals, Or not to the backlight.

The method according to claim 1,
Wherein the control unit corrects the determined increased width when the current unit image is brighter than the previous unit image in the temporally consecutive unit image, wherein the increased width is greater than when the difference is greater than when the difference is greater Wherein the correction is performed in such a manner as to greatly reduce the luminance of the display device.

The method according to claim 1,
Wherein the controller is configured to calculate a correction value for decreasing the determined increased width based on the ratio of the dark portion values when the ratio of the dark portion values corresponding to the predetermined reference value or lower among the gray values of the unit image is more than a limited ratio, And to control the backlight to apply an increased intensity according to the correction,
Wherein the controller corrects the increase in width in such a manner that the width is increased more than when the ratio of the arm portions is large.

The method according to claim 1,
Wherein the controller corrects the increased width by further increasing or decreasing the determined width based on whether the identified spatial frequency belongs to a designated frequency band for the gray values of the unit image, And to cause an intensity increased by the corrected width to be applied to the backlight.

The method according to claim 1,
Wherein the controller calculates the first increase in accordance with the degree of compactness by applying the first method and further applies the second increase in the second method to calculate a second increase according to the degree of compactness, And a value obtained by summing up the sum of the values of the first and second threshold values,
The first method is a method of determining the intensity of the light source based on the efficiency of the power of the power consumed by increasing the intensity of the light source and the second method is a method of increasing the intensity of the light source, Is a method of determining the intensity of the light source based on an increase in the intensity of the light source which is no longer improved or whose image quality enhancement begins to fall below the predetermined threshold,
Wherein the ratio assigned to the first increment and the second increment is used to determine the width to be increased by setting the same or a different value based on the user's selection or the physical display characteristics of the panel Display device.

The method according to claim 1,
Wherein the control unit determines whether to increase or decrease the intensity of the light source more or less than the currently set intensity based on the brightness of the unit image, And to determine the increased width.

17. The method of claim 16,
Wherein the control unit reduces the intensity of the light source more than the currently set intensity when the brightness of the unit image indicates a predetermined reference value or less and controls the backlight so that the reduced intensity is applied,
Wherein the control unit is configured to determine the intensity of the light source in such a manner that the decrease width is larger when the analysis unit recognizes and transmits the unit image when the inclination degree of the unit image is small,
The inclination is an average of individual gradients obtained for the gradation values of the unit image, and the individual gradation is a value obtained by dividing the difference between the gradation values of any two pixels by the distance between the two pixels Of the display device.

17. The method of claim 16,
Wherein the control unit reduces the intensity of the light source more than the currently set intensity when the brightness of the unit image indicates a predetermined reference value or less and controls the backlight so that the reduced intensity is applied,
Wherein the control unit is configured to determine the intensity of the light source in such a manner that the reduction width is larger when the brightness characteristic value of the unit image is smaller when the analysis unit recognizes and transmits the unit image,
Wherein the brightness characteristic value is calculated from a boundary gradation value in which the cumulative number of distributed gradation values starts from a maximum value that a pixel can have among the gradation values of the unit image, And has a characteristic proportional to the magnitude of the boundary tone value.

17. The method of claim 16,
The control unit controls the intensity of the currently set light source to be maintained for the unit image when the brightness of the unit image is equal to or greater than a predetermined reference value and the density is lower than a predetermined threshold . &Lt; / RTI >

17. The method of claim 16,
Wherein the control unit is configured to reduce the intensity of the light source to a smaller value than the case where the intensity of the light source is increased in accordance with the selection information applied by the user, And adjust the reference used to determine whether to increase or decrease the intensity of the light source.

A method of adjusting intensity of a light source required to visually represent a video signal,
A first step of grasping a distribution characteristic of tone values of an input unit image,
A gray level value of each pixel in the unit image is output as a visual signal based on the density of the detected distribution characteristic in at least one of the plurality of intervals divided for the range that the gray level value can have, A second step of determining the intensity of the light source provided in an area of the panel to be an intensity that is greater than a preset intensity, and when the density is high,
And controlling the display panel so that the intensity of the determined light source is applied to an area where the unit image on the display panel is displayed,
The second step may include a density state of the grasped distribution characteristic centering on a first reference value and a third reference value in the darkest interval and the brightest interval among the plurality of intervals, The density state of the grasped distribution characteristic centering on a second reference value in a section of the plurality of sections and the concentrated state of the grasped distribution characteristic centered on the third reference value in the brightest section of the plurality of sections Wherein the intensity of the light source is determined from the at least one dense state of the at least one of the plurality of light sources.