WO2012098888A1 - Dispositif de visualisation d'image et procédé de commande pour dispositif de visualisation d'image - Google Patents

Dispositif de visualisation d'image et procédé de commande pour dispositif de visualisation d'image Download PDF

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Publication number
WO2012098888A1
WO2012098888A1 PCT/JP2012/000300 JP2012000300W WO2012098888A1 WO 2012098888 A1 WO2012098888 A1 WO 2012098888A1 JP 2012000300 W JP2012000300 W JP 2012000300W WO 2012098888 A1 WO2012098888 A1 WO 2012098888A1
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Prior art keywords
code
subfield
gradation
gradation value
rule
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PCT/JP2012/000300
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English (en)
Japanese (ja)
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広史 本田
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パナソニック株式会社
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2018—Display of intermediate tones by time modulation using two or more time intervals
    • G09G3/2022—Display of intermediate tones by time modulation using two or more time intervals using sub-frames
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2044—Display of intermediate tones using dithering
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2044—Display of intermediate tones using dithering
    • G09G3/2051—Display of intermediate tones using dithering with use of a spatial dither pattern
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2059—Display of intermediate tones using error diffusion
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/28—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels
    • G09G3/288—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/06—Details of flat display driving waveforms
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0261—Improving the quality of display appearance in the context of movement of objects on the screen or movement of the observer relative to the screen

Definitions

  • the present invention relates to an image display device that displays an image in an image display region by combining binary control of light emission and non-light emission in a light emitting element that constitutes a pixel, and a driving method of the image display device.
  • a plasma display panel (hereinafter abbreviated as “panel”) is a typical image display device that displays an image in an image display area by combining binary control of light emission and non-light emission in a light emitting element constituting a pixel. is there.
  • a large number of discharge cells which are light-emitting elements constituting pixels, are formed between a front substrate and a rear substrate that are arranged to face each other.
  • a plurality of pairs of display electrodes composed of a pair of scan electrodes and sustain electrodes are formed on the front glass substrate in parallel with each other.
  • a dielectric layer and a protective layer are formed so as to cover the display electrode pairs.
  • the back substrate has a plurality of parallel data electrodes formed on the glass substrate on the back side, a dielectric layer is formed so as to cover the data electrodes, and a plurality of barrier ribs are formed thereon in parallel with the data electrodes. ing. And the fluorescent substance layer is formed in the surface of a dielectric material layer, and the side surface of a partition.
  • the front substrate and the rear substrate are arranged opposite to each other and sealed so that the display electrode pair and the data electrode are three-dimensionally crossed.
  • a discharge gas containing xenon at a partial pressure ratio of 5% is sealed, and a discharge cell is formed in a portion where the display electrode pair and the data electrode face each other.
  • ultraviolet rays are generated by gas discharge in each discharge cell, and the phosphors of each color of red (R), green (G) and blue (B) are excited and emitted by the ultraviolet rays. Display an image.
  • a subfield method is generally used as a method for displaying an image in an image display region by combining binary control of light emission and non-light emission in a light emitting element.
  • each discharge cell In the subfield method, one field is divided into a plurality of subfields having different emission luminances.
  • each discharge cell light emission / non-light emission of each subfield is controlled by a combination according to a desired gradation value.
  • each discharge cell emits light with the emission luminance of one field set to a desired gradation value, and an image composed of various combinations of gradation values is displayed in the image display area of the panel.
  • each subfield has an address period and a sustain period.
  • the scan pulse is sequentially applied to the scan electrodes, and the address pulse is selectively applied to the data electrodes based on the image signal to be displayed.
  • an address discharge is generated between the scan electrode and the data electrode of the discharge cell to emit light, and a wall charge is formed in the discharge cell (hereinafter, these operations are also collectively referred to as “address”). ).
  • the number of sustain pulses based on the gradation weights determined for each subfield is alternately applied to the display electrode pairs composed of the scan electrodes and the sustain electrodes.
  • a sustain discharge is generated in the discharge cell that has generated the address discharge, and the phosphor layer of the discharge cell emits light (hereinafter referred to as “lighting” that the discharge cell emits light by the sustain discharge, and “non-emitting”). Also written as “lit”.)
  • each discharge cell is made to emit light with the luminance according to the gradation weight.
  • each discharge cell of the panel is caused to emit light with a luminance corresponding to the gradation value of the image signal, and an image is displayed in the image display area of the panel.
  • the plasma display device has an image signal processing circuit.
  • the image signal processing circuit converts an image signal (hereinafter simply referred to as “image signal”) input to the plasma display device into a subfield code indicating lighting / non-lighting for each subfield in each discharge cell.
  • the image signal processing circuit has a conversion table composed of a plurality of subfield codes.
  • one subfield code is associated with one gradation value. That is, when one gradation value is input, the conversion table outputs one subfield code associated with the gradation value.
  • the conversion table is stored in a semiconductor storage element such as a ROM and provided in the image signal processing circuit. Then, using the conversion table, the image signal processing circuit converts each gradation value of the image signal into a subfield code (data indicating light emission / non-light emission for each subfield) corresponding to each gradation value. Output to the circuit.
  • the number of gradation values that can be displayed on the panel is determined by the number of subfield codes constituting the conversion table. If the number of subfield codes constituting the conversion table is large, the number of gradation values that can be displayed on the panel increases, and if the number of subfield codes constituting the conversion table is small, the number of gradation values that can be displayed on the panel. Decrease.
  • the number of gradation values that can be displayed on the panel is related to the power consumption of the plasma display device, and the number of gradation values that can be displayed on the panel is relatively reduced when the power consumption is reduced. Therefore, the subfield codes constituting the conversion table are generally determined in consideration of the power consumption of the plasma display device, the smoothness of the image that can be displayed on the panel, and the like.
  • the gradation values that cannot be displayed on the panel increase. For example, if the conversion table includes the subfield code of gradation value “7” and gradation value “9” and does not include the subfield code of gradation value “8”, the gradation value “8” is displayed on the panel. "Cannot be displayed. However, gradation values that cannot be displayed on the panel can be displayed on the panel in a pseudo manner by using a generally known method such as a dither method or an error diffusion method.
  • this moving image pseudo contour changes according to the number of subfield codes constituting the conversion table, and when the number of subfield codes constituting the conversion table increases, the moving image pseudo contour is likely to occur. .
  • the plasma display device it is desirable to display the image with a smooth gradation change by increasing the gradation values that can be displayed on the panel as much as possible, while reducing the moving image pseudo contour as much as possible.
  • the plasma display device includes a plurality of conversion tables having different numbers and types of subfield codes constituting the conversion table, and the plurality of conversion tables. Has been disclosed (for example, see Patent Document 1).
  • a plasma display device includes a plurality of conversion tables. Then, a minimum value and an average value of the image signal are obtained, and a threshold value is calculated from the minimum value and the average value. Then, one conversion table is selected from a plurality of conversion tables based on this threshold value. Then, the image signal is converted into a subfield code based on the selected conversion table.
  • the number of conversion tables to be provided in the plasma display device is very large as compared with the conventional plasma display device. For this reason, it is difficult to configure an image signal processing circuit having such a large number of conversion tables and selecting an optimum one from a large number of conversion tables according to various conditions. It is coming.
  • the plasma display device includes a plurality of electrode driving circuits for driving each electrode, and the driving voltage waveforms necessary for displaying an image on the panel are respectively displayed using the plurality of electrode driving circuits. Apply to electrode.
  • the plurality of electrode drive circuits include a data electrode drive circuit for driving the data electrodes.
  • the data electrode driving circuit applies a write pulse for a write operation to each of the plurality of data electrodes according to the image signal. Therefore, the data electrode driving circuit is generally configured using a dedicated integrated circuit (IC) for generating an address pulse.
  • IC integrated circuit
  • the data electrode viewed from the data electrode driving circuit is a capacitive load having a stray capacitance between adjacent data electrodes, a stray capacitance between the scan electrodes, and a stray capacitance between the sustain electrodes. Therefore, in order to apply a drive voltage waveform to the data electrode, the data electrode drive circuit must charge and discharge this capacitor, and power consumption for that purpose is required.
  • a plurality of subfields having gradation weights constitute one field, and each of the plurality of subfields is expressed using a subfield code indicating a combination of light emission and non-light emission in each of the plurality of subfields.
  • This is an image display device that controls the light emission and non-light emission, displays a gradation value based on an image signal on each of a plurality of pixels constituting the image display area, and displays an image in the image display area.
  • This image display device includes an image signal processing circuit that outputs a display code that is a subfield code for displaying a gradation value based on an image signal on a pixel.
  • the image signal processing circuit includes a base code generation unit, a rule generation unit, a rule addition unit, an upper and lower code generation unit, and a display code selection unit.
  • the base code generation unit has a gradation value that is larger than the gradation value of the image signal at the target pixel and has the closest gradation value to the gradation value of the image signal at the target pixel, from among a plurality of basic subfield codes.
  • the field code is selected as the upper gradation base code.
  • the rule generation unit generates a first rule for generating a new subfield code by changing the light-emitting subfield in the upper gradation base code to a non-light-emitting subfield based on the image signal at the target pixel. .
  • a rule addition part produces
  • the upper / lower code generation unit applies the first rule and the second rule to the upper gradation base code, and generates a pixel of interest that is larger than the gradation value of the image signal in the pixel of interest from among the newly generated subfield codes.
  • the subfield code having the gradation value closest to the gradation value of the image signal at is selected as the upper gradation code, and the gradation value of the image signal at the target pixel is equal to or lower than the gradation value of the image signal at the target pixel.
  • the subfield code having the closest gradation value is selected as the lower gradation code.
  • the display code selection unit calculates a gradation value to be displayed on the target pixel by adding a predetermined value to the gradation value of the image signal in the target pixel, and sets the target pixel of the upper gradation code and the lower gradation code. One having a gradation value closer to the gradation value to be displayed is selected as a display code.
  • the conversion from the image signal to the subfield code can be performed by calculation using the calculation circuit. Therefore, even in an image display device that needs to cope with high functionality and multi-function, it is not necessary to provide a huge number of conversion tables for converting image signals into subfield codes. That is, it is not necessary to configure the image signal processing circuit so as to select an optimal one from a vast number of conversion tables according to various conditions. Furthermore, power consumption can be suppressed while preventing deterioration in image display quality in the image display device.
  • a signal generated based on the estimated power consumption in the image display device is used as a predetermined control signal.
  • the plurality of basic subfield codes described above are all subfields having the largest gradation weight among the subfields that emit light, and all having a gradation weight smaller than that subfield.
  • This is a sub-field code in which the sub-field emits light.
  • the predetermined value described above is an error generated by error diffusion processing and a dither value generated by dither processing.
  • the present invention also comprises a plurality of subfields using a subfield code indicating a combination of light emission and non-light emission in each of the plurality of subfields, with a plurality of subfields having gradation weights defined.
  • Method for driving an image display apparatus for controlling each light emission and non-light emission of each of the image display, displaying a gradation value based on an image signal on each of a plurality of pixels constituting the image display area, and displaying an image on the image display area It is.
  • This driving method is a subfield having a gradation value that is larger than the gradation value of the image signal in the pixel of interest and closest to the gradation value of the image signal in the pixel of interest, among a plurality of basic subfield codes.
  • Step and new generation by applying the first rule and the second rule to the upper tone base code A sub-field code having a gradation value larger than the gradation value of the image signal at the target pixel and closest to the gradation value of the image signal at the target pixel is selected as the upper gradation code Selecting a sub-field code having a gradation value that is equal to or lower than the gradation value of the image signal at the target pixel as the lower gradation code, and the gradation of the image signal at the target pixel; A step of calculating a gradation value to be displayed on the target pixel by adding a predetermined value to the value, and a gradation value closer to the gradation value to be displayed on the target pixel among the upper gradation code and the lower gradation code Selecting a display code as a display code which is a subfield code for displaying a gradation value based on an image signal on a target pixel.
  • the conversion from the image signal to the subfield code can be performed by calculation using the calculation circuit. Therefore, even in an image display device that needs to cope with high functionality and multi-function, it is not necessary to provide a huge number of conversion tables for converting image signals into subfield codes. That is, it is not necessary to configure the image signal processing circuit so as to select an optimal one from a vast number of conversion tables according to various conditions. Furthermore, power consumption can be suppressed while preventing deterioration in image display quality in the image display device.
  • a signal generated based on the estimated power consumption in the image display device is used as the predetermined control signal.
  • FIG. 1 is an exploded perspective view showing a structure of a panel used in an image display apparatus according to an embodiment of the present invention.
  • FIG. 2 is an electrode array diagram of a panel used in the image display apparatus according to the embodiment of the present invention.
  • FIG. 3 is a diagram schematically showing drive voltage waveforms applied to the respective electrodes of the panel used in the image display device according to the embodiment of the present invention.
  • FIG. 4 is a diagram showing an example of a code set when one field is composed of eight subfields.
  • FIG. 5 is a diagram schematically showing an example of a circuit block constituting the image display device according to the embodiment of the present invention.
  • FIG. 1 is an exploded perspective view showing a structure of a panel used in an image display apparatus according to an embodiment of the present invention.
  • FIG. 2 is an electrode array diagram of a panel used in the image display apparatus according to the embodiment of the present invention.
  • FIG. 3 is a diagram schematically showing drive voltage waveforms applied to the respective electrodes of the panel used
  • FIG. 6 is a diagram schematically showing an example of a circuit block constituting the image signal processing circuit of the image display apparatus according to the embodiment of the present invention.
  • FIG. 7A is a diagram showing an example of a base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 7B is a diagram showing another example of the base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 7C is a diagram illustrating another example of the base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 8 is a diagram schematically showing an example of a circuit block constituting the rule adding unit of the image display device according to the embodiment of the present invention.
  • FIG. 7A is a diagram showing an example of a base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 7B is a diagram showing another example of the base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 7C is a
  • FIG. 9A is a diagram illustrating an example of an intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 9B is a diagram showing another example of the intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 9C is a diagram showing another example of the intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 9D illustrates an intermediate code generated in the intermediate code generation unit based on the first rule generated in the rule generation unit of the image display device and the second rule generated in the rule addition unit according to the embodiment of the present invention. It is a figure which shows an example of a code set.
  • FIG. 9A is a diagram illustrating an example of an intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 9B is a diagram showing another example of the intermediate code set generated by the intermediate code generation unit of the image display
  • FIG. 9E illustrates an intermediate code generated in the intermediate code generation unit based on the first rule generated in the rule generation unit of the image display apparatus and the second rule generated in the rule addition unit according to the embodiment of the present invention. It is a figure which shows another example of a code set.
  • FIG. 10A is a diagram showing an example of a dither pattern used in the image display device in one embodiment of the present invention.
  • FIG. 10B is a diagram showing another example of the dither pattern used in the image display device according to the embodiment of the present invention.
  • FIG. 11 is a diagram showing the error diffusion coefficient of the error diffusion unit of the image display device according to the embodiment of the present invention.
  • FIG. 12 is a flowchart showing the operation of the image signal processing circuit of the image display device according to the embodiment of the present invention.
  • FIG. 1 is an exploded perspective view showing the structure of panel 10 used in the image display apparatus according to the embodiment of the present invention.
  • a plurality of display electrode pairs 14 each including a scanning electrode 12 and a sustaining electrode 13 are formed on a glass front substrate 11.
  • a dielectric layer 15 is formed so as to cover the scan electrode 12 and the sustain electrode 13, and a protective layer 16 is formed on the dielectric layer 15.
  • This protective layer 16 has been used as a panel material in order to lower the discharge start voltage in the discharge cell, and has a large secondary electron emission coefficient and durability when neon (Ne) and xenon (Xe) gas is sealed. It is made of a material mainly composed of magnesium oxide (MgO).
  • the protective layer 16 may be composed of a single layer or may be composed of a plurality of layers. Moreover, the structure which particle
  • a plurality of data electrodes 22 are formed on the rear substrate 21, a dielectric layer 23 is formed so as to cover the data electrodes 22, and a grid-like partition wall 24 is further formed thereon.
  • a phosphor layer 25R that emits red (R)
  • a phosphor layer 25G that emits green (G)
  • a phosphor layer 25B that emits blue (B).
  • the phosphor layer 25R, the phosphor layer 25G, and the phosphor layer 25B are collectively referred to as a phosphor layer 25.
  • the front substrate 11 and the rear substrate 21 are arranged to face each other so that the display electrode pair 14 and the data electrode 22 intersect each other with a minute space therebetween, and a discharge space is provided in the gap between the front substrate 11 and the rear substrate 21.
  • the outer peripheral part is sealed with sealing materials, such as glass frit.
  • sealing materials such as glass frit.
  • a mixed gas of neon and xenon is sealed in the discharge space as a discharge gas.
  • the discharge space is partitioned into a plurality of sections by the barrier ribs 24, and discharge cells, which are light-emitting elements constituting the pixels, are formed at the intersections between the display electrode pairs 14 and the data electrodes 22.
  • one pixel is composed of three consecutive discharge cells arranged in the direction in which the display electrode pair 14 extends.
  • the three discharge cells are a discharge cell having a phosphor layer 25R and emitting red (R) (red discharge cell), and a discharge cell having a phosphor layer 25G and emitting green (G) (green). And a discharge cell having a phosphor layer 25B and emitting blue (B) light (blue discharge cell).
  • the structure of the panel 10 is not limited to the above-described structure, and may be, for example, provided with a stripe-shaped partition wall.
  • FIG. 2 is an electrode array diagram of panel 10 used in the plasma display device according to one embodiment of the present invention.
  • the panel 10 includes n scan electrodes SC1 to SCn (scan electrode 12 in FIG. 1) extended in the horizontal direction (row direction and line direction) and n sustain electrodes SU1 to SUn (FIG. 1).
  • the sustain electrodes 13) are arranged, and m data electrodes D1 to Dm (data electrodes 22 in FIG. 1) extending in the vertical direction (column direction) are arranged.
  • m discharge cells are formed on one pair of display electrodes 14 and m / 3 pixels are formed.
  • the plasma display device in the present embodiment drives the panel 10 by the subfield method.
  • the subfield method one field of an image signal is divided into a plurality of subfields on the time axis, and a gradation weight is set for each subfield. Therefore, each field has a plurality of subfields having different gradation weights.
  • Each subfield has an initialization period, an address period, and a sustain period. Based on the image signal, light emission / non-light emission of each discharge cell is controlled for each subfield. That is, a plurality of gradations based on the image signal are displayed on the panel 10 by combining the light-emitting subfield and the non-light-emitting subfield based on the image signal.
  • an initializing operation is performed in which initializing discharge is generated in the discharge cells and wall charges necessary for the address discharge in the subsequent address period are formed on each electrode.
  • Initialization operation includes “forced initialization operation” that forcibly generates an initializing discharge in all discharge cells regardless of the operation of the immediately preceding subfield and an addressing discharge that occurs in the addressing period of the immediately preceding subfield.
  • the forced initializing operation the rising ramp waveform voltage and the falling ramp waveform voltage are applied to the scan electrode 12 to generate an initializing discharge in the discharge cell.
  • the forced initializing operation is performed in all discharge cells in the initializing period of one subfield, and all the discharge cells are selected in the initializing period of the other subfield. Perform initialization.
  • force initialization period the initialization period in which the forced initialization operation is performed
  • subfield having the forced initialization period is referred to as “forced initialization subfield”.
  • An initialization period for performing the selective initialization operation is referred to as a “selective initialization period”
  • a subfield having the selective initialization period is referred to as a “selective initialization subfield”.
  • subfield SF1 is a forced initialization subfield
  • the other subfields are selected initialization subfields.
  • the present invention is not limited to the above-described subfields as subfields for forced initialization subfields and subfields for selective initialization subfields.
  • the structure which switches a subfield structure based on an image signal etc. may be sufficient.
  • a scan pulse is applied to the scan electrode 12 and an address pulse is selectively applied to the data electrode 22 to selectively generate an address discharge in the discharge cells to emit light. Then, an address operation is performed to form wall charges in the discharge cells for generating a sustain discharge in the subsequent sustain period.
  • sustain pulses of the number obtained by multiplying the gradation weight set in each subfield by a predetermined proportional constant are alternately applied to the scan electrode 12 and the sustain electrode 13 to generate an address discharge in the immediately preceding address period.
  • a sustain discharge is generated in the discharged discharge cell, and a sustain operation for emitting light from the discharge cell is performed.
  • This proportionality constant is a luminance multiple.
  • the gradation weight represents the ratio of the magnitude of the luminance displayed in each subfield, and the number of sustain pulses corresponding to the gradation weight is generated in the sustain period in each subfield. Therefore, for example, the subfield with the gradation weight “8” emits light with a luminance about eight times that of the subfield with the gradation weight “1”, and about four times as high as the subfield with the gradation weight “2”. Emits light. Therefore, for example, if the subfield with the gradation weight “8” and the subfield with the gradation weight “2” are emitted, the discharge cell can emit light with a luminance corresponding to the gradation value “10”.
  • each discharge cell emits light with various gradation values by selectively emitting light in each subfield by controlling light emission / non-light emission of each discharge cell for each subfield in a combination according to the image signal. That is, a gradation value corresponding to an image signal can be displayed on each discharge cell, and an image based on the image signal can be displayed on the panel 10.
  • one pixel includes three consecutive discharge cells arranged in the direction in which the display electrode pair 14 extends, that is, a red discharge cell, a green discharge cell, and a blue discharge.
  • a red discharge cell is also referred to as a “red pixel”, a green discharge cell as a “green pixel”, and a blue discharge cell as a “blue pixel”.
  • FIG. 3 is a diagram schematically showing drive voltage waveforms applied to the respective electrodes of panel 10 used in the plasma display device according to one embodiment of the present invention.
  • FIG. 3 shows data electrode D1 to data electrode Dm, scan electrode SC1 that performs the address operation first in the address period, scan electrode SCn that performs the address operation last in the address period (for example, scan electrode SC1080), sustain electrode SU1 to The drive voltage waveform applied to each of the sustain electrodes SUn is shown.
  • Scan electrode SCi, sustain electrode SUi, and data electrode Dk in the following represent electrodes selected based on image data (data indicating light emission / non-light emission for each subfield) from among the electrodes.
  • FIG. 3 shows a subfield SF1 that is a forced initialization subfield, and a subfield SF2 and a subfield SF3 that are selective initialization subfields.
  • the subfield SF1, the subfield SF2, and the subfield SF3 have different waveform shapes of the drive voltage applied to the scan electrode 12 in the initialization period.
  • each subfield except subfield SF1 is a selective initialization subfield, and substantially the same drive voltage waveform in each period except the number of sustain pulses. Is generated.
  • the voltage 0 (V) is applied to the data electrode D1 to the data electrode Dm and the sustain electrode SU1 to the sustain electrode SUn.
  • a voltage Vi1 is applied to scan electrode SC1 through scan electrode SCn after voltage 0 (V) is applied, and a ramp waveform voltage that gradually rises from voltage Vi1 to voltage Vi2 (hereinafter referred to as an “upward ramp waveform voltage”). ) Is applied.
  • voltage Vi1 is set to a voltage lower than the discharge start voltage for sustain electrode SU1 to sustain electrode SUn
  • voltage Vi2 is set to a voltage exceeding the discharge start voltage for sustain electrode SU1 to sustain electrode SUn.
  • the wall voltage on the electrode represents a voltage generated by wall charges accumulated on the dielectric layer covering the electrode, the protective layer, the phosphor layer, and the like.
  • the positive voltage Ve is applied to the sustain electrodes SU1 to SUn, and the voltage 0 (V) is applied to the data electrodes D1 to Dm.
  • a scan waveform SC1 to scan electrode SCn are applied with a ramp waveform voltage that gently falls from voltage Vi3 to negative voltage Vi4 (hereinafter referred to as “down ramp waveform voltage”).
  • Voltage Vi3 is set to a voltage lower than the discharge start voltage with respect to sustain electrode SU1 through sustain electrode SUn
  • voltage Vi4 is set to a voltage exceeding the discharge start voltage with respect to sustain electrode SU1 through sustain electrode SUn.
  • the above voltage waveform is a forced initializing waveform that generates an initializing discharge in the discharge cell regardless of the operation of the immediately preceding subfield.
  • the operation for applying the forced initialization waveform to the scan electrode 12 is the forced initialization operation.
  • the forced initialization operation in the initialization period Ti1 of the forced initialization subfield ends.
  • initializing discharge is forcibly generated in all the discharge cells in the image display area of the panel 10.
  • voltage Ve is applied to sustain electrode SU1 through sustain electrode SUn
  • voltage 0 (V) is applied to data electrode D1 through data electrode Dm
  • scan electrode SC1 through scan electrode SCn are applied. Applies a voltage Vc.
  • a negative scan pulse having a negative voltage Va is applied to the first (first row) scan electrode SC1 in terms of arrangement.
  • a positive address pulse of a positive voltage Vd is applied to the data electrode Dk of the discharge cell that should emit light in the first row of the data electrodes D1 to Dm.
  • sustain electrode SU1 since voltage Ve is applied to sustain electrode SU1 through sustain electrode SUn, sustain electrode SU1 in a region intersecting data electrode Dk is induced by a discharge generated between data electrode Dk and scan electrode SC1. Discharge also occurs between scan electrode SC1 and scan electrode SC1. Thus, address discharge is generated in the discharge cells (discharge cells to emit light) to which the scan pulse voltage Va and the address pulse voltage Vd are simultaneously applied.
  • a positive wall voltage is accumulated on the scan electrode SC1
  • a negative wall voltage is accumulated on the sustain electrode SU1
  • a negative wall voltage is also accumulated on the data electrode Dk.
  • the address operation in the discharge cells in the first row is completed.
  • the discharge cell having the data electrode Dh to which the address pulse is not applied the data electrode Dh is the data electrode D1 to the data electrode Dm excluding the data electrode Dk
  • the intersection of the data electrode Dh and the scan electrode SC1 Since the voltage of the portion does not exceed the discharge start voltage, the address discharge does not occur, and the wall voltage after the end of the initialization period Ti1 is maintained.
  • a scan pulse of the voltage Va is applied to the second (second row) scan electrode SC2 from the top, and the voltage Vd is applied to the data electrode Dk corresponding to the discharge cell to emit light in the second row. Apply the write pulse.
  • address discharge occurs in the discharge cells in the second row to which the scan pulse and address pulse are simultaneously applied.
  • the address operation in the discharge cells in the second row is performed.
  • voltage Ve applied to sustain electrode SU1 through sustain electrode SUn in the second half of initialization period Ti1 and voltage Ve applied to sustain electrode SU1 through sustain electrode SUn in address period Tw1 may have different voltage values. .
  • the voltage 0 (V) is applied to the sustain electrodes SU1 to SUn. Then, sustain pulse of positive voltage Vs is applied to scan electrode SC1 through scan electrode SCn.
  • the voltage difference between the scan electrode SCi and the sustain electrode SUi exceeds the discharge start voltage, and is maintained between the scan electrode SCi and the sustain electrode SUi. Discharge occurs.
  • the phosphor layer 25 of the discharge cell in which the sustain discharge has occurred emits light by the ultraviolet rays generated by the sustain discharge.
  • a negative wall voltage is accumulated on scan electrode SCi
  • a positive wall voltage is accumulated on sustain electrode SUi.
  • a positive wall voltage is also accumulated on the data electrode Dk.
  • the sustain discharge does not occur in the discharge cells in which the address discharge has not occurred in the address period Tw1.
  • the sustain pulses of the number obtained by multiplying the gradation weight by a predetermined luminance multiple are alternately applied to scan electrode SC1 through scan electrode SCn and sustain electrode SU1 through sustain electrode SUn.
  • the discharge cells that have generated the address discharge in the address period generate the sustain discharges the number of times corresponding to the gradation weight, and emit light with the luminance corresponding to the gradation weight.
  • scan electrode SC1 to scan are performed while voltage 0 (V) is applied to sustain electrode SU1 to sustain electrode SUn and data electrode D1 to data electrode Dm.
  • An upward ramp waveform voltage that gradually rises from voltage 0 (V) to voltage Vr is applied to electrode SCn.
  • the sustain of the discharge cell that has generated the sustain discharge is maintained while the rising ramp waveform voltage applied to scan electrode SC1 through scan electrode SCn exceeds the discharge start voltage.
  • a weak discharge (erase discharge) is continuously generated between the electrode SUi and the scan electrode SCi.
  • the charged particles generated by this weak discharge are accumulated as wall charges on the sustain electrode SUi and the scan electrode SCi so as to reduce the voltage difference between the sustain electrode SUi and the scan electrode SCi.
  • the wall voltage on scan electrode SCi and the wall voltage on sustain electrode SUi are weakened while the positive wall voltage on data electrode Dk remains.
  • unnecessary wall charges in the discharge cell are erased.
  • the voltage 0 (V) is applied to the data electrodes D1 to Dm, and the positive voltage Ve is applied to the sustain electrodes SU1 to SUn.
  • Scan electrode SC1 to scan electrode SCn decrease from a voltage lower than the discharge start voltage (for example, voltage 0 (V)) toward negative voltage Vi4 at the same gradient as the downward ramp waveform voltage generated in initialization period Ti1. Apply a downward ramp waveform voltage.
  • the voltage Vi4 is set to a voltage exceeding the discharge start voltage.
  • the negative wall voltage on scan electrode SCi and the positive wall voltage on sustain electrode SUi are weakened.
  • an excessive portion of the positive wall voltage on the data electrode Dk is discharged.
  • the wall voltage in the discharge cell is adjusted to a wall voltage suitable for the address operation in the address period Tw2.
  • the voltage waveform described above is a selective initialization waveform in which an initializing discharge is selectively generated in a discharge cell that has performed an address operation in the address period (here, address period Tw1) of the immediately preceding subfield.
  • the operation of applying the selective initialization waveform to the scan electrode 12 is the selective initialization operation.
  • the same drive voltage waveform as that in the address period Tw1 of the subfield SF1 is applied to each electrode.
  • the number of sustain pulses corresponding to the gradation weights are alternately applied to the scan electrodes SC1 to SCn and the sustain electrodes SU1 to SUn.
  • each subfield after subfield SF3 the same drive voltage waveform as in subfield SF2 is applied to each electrode except for the number of sustain pulses generated in the sustain period.
  • Voltage Vc ⁇ 60 (V)
  • voltage Va ⁇ 200 (V)
  • voltage Vs 200 (V)
  • voltage Vr 200 (V)
  • voltage Ve 130 (V)
  • voltage Vd 70 (V)
  • the gradient of the rising ramp waveform voltage generated in the initialization period Ti1 is about 1.3 V / ⁇ sec
  • the gradient of the rising ramp waveform voltage generated in each sustain period is about 10 V / ⁇ sec.
  • the gradient of the generated downward ramp waveform voltage is about ⁇ 1.5 V / ⁇ sec.
  • the specific numerical values such as the voltage value and the gradient described above are merely examples, and the present invention is not limited to the numerical values described above for each voltage value and the gradient.
  • Each voltage value, gradient, and the like are preferably set optimally based on the discharge characteristics of the panel and the specifications of the plasma display device.
  • subfield SF1 is a forced initialization subfield for performing a forced initialization operation
  • other subfields are a selective initialization subfield for performing a selective initialization operation
  • the present invention is not limited to this configuration.
  • the subfield SF1 may be a selective initialization subfield and other subfields may be forced initialization subfields, or a plurality of subfields may be forced initialization subfields.
  • one field is composed of a plurality of subfields in which gradation weights are determined in advance. Then, by combining a subfield that is lit (lighting subfield) and a subfield that is not lit (non-lighting subfield), each discharge cell emits light with a light emission luminance corresponding to the magnitude of the gradation value based on the image signal. .
  • subfield code a combination of a lighting subfield and a non-lighting subfield
  • code set a set of a plurality of subfield codes
  • a subfield code is selected from a plurality of subfield codes constituting a code set according to a gradation value. Then, light emission / non-light emission of each subfield is controlled based on the subfield code, and the discharge cell is caused to emit light with a luminance corresponding to the magnitude of the gradation value, and an image is displayed on the panel 10.
  • the gradation value when displaying black (the gradation value when no sustain discharge occurs) is assumed to be “0”.
  • a gradation value corresponding to the gradation weight “N” is expressed as a gradation value “N”.
  • the gradation value displayed by the discharge cells that emit light only in the subfield SF1 having the gradation weight “1” is the gradation value “1”.
  • FIG. 4 is a diagram showing an example of a code set when one field is composed of eight subfields.
  • the numerical value shown immediately below the notation indicating each subfield represents the gradation weight of each subfield.
  • FIG. 4 includes eight subfields SF1 to SF8 in one field, and each subfield is “1”, “2”, “3”, “5”, “8”, respectively. ”,“ 13 ”,“ 21 ”, and“ 34 ”indicate code sets having gradation weights.
  • the light emitting subfield is indicated by “1”
  • the non-light emitting subfield is indicated by a blank
  • the leftmost column indicates the gradation value to be displayed in each subfield code.
  • the subfield code corresponding to the gradation value “2” is “01000000”.
  • subfield code data 0 or 1 is arranged in the order of subfield SF1, subfield SF2, subfield SF3, subfield SF4, subfield SF5, subfield SF6, subfield SF7, and subfield SF8 from the left.
  • binary numerical values shown as subfield codes are arranged in the order of subfield SF1, subfield SF2, subfield SF3,.
  • the subfield code corresponding to the gradation value “14” is “11101000”. Accordingly, in the discharge cell displaying the gradation value “14”, the subfield SF1, the subfield SF2, the subfield SF3, and the subfield SF5 emit light.
  • FIG. 5 is a diagram schematically showing an example of a circuit block constituting the image display device 30 according to the embodiment of the present invention.
  • the image display device 30 includes a panel 10 and a drive circuit that drives the panel 10.
  • the drive circuit includes an image signal processing circuit 31, a data electrode drive circuit 32, a scan electrode drive circuit 33, a sustain electrode drive circuit 34, a timing generation circuit 35, and a power supply circuit (not shown) that supplies necessary power to each circuit block. It has.
  • the image signals input to the image signal processing circuit 31 are a red image signal, a green image signal, and a blue image signal. Based on the red image signal, the green image signal, and the blue image signal, the image signal processing circuit 31 sets each gradation value of red, green, and blue (a gradation value expressed by one field) to each discharge cell. To do.
  • the input image signal includes a luminance signal (Y signal) and a saturation signal (C signal, or RY signal and BY signal, or u signal and v signal, etc.).
  • a red image signal, a green image signal, and a blue image signal are calculated based on the luminance signal and the saturation signal, and then, each gradation value of red, green, and blue is set in each discharge cell.
  • the red, green, and blue gradation values set for each discharge cell are subfield codes indicating lighting / non-lighting for each subfield (light emission / non-light emission corresponds to digital signals “1” and “0”).
  • the subfield code is output as a display code. That is, the image signal processing circuit 31 converts the red image signal, the green image signal, and the blue image signal into a red display code, a green display code, and a blue display code and outputs the converted signals.
  • the image signal processing circuit 31 does not convert an image signal into a subfield code using a conversion table, but converts the image signal into a subfield code by a logical operation. Details of this will be described later.
  • the timing generation circuit 35 generates various timing signals for controlling the operation of each circuit block based on the horizontal synchronization signal and the vertical synchronization signal.
  • the generated timing signal is supplied to each circuit block (data electrode drive circuit 32, scan electrode drive circuit 33, sustain electrode drive circuit 34, image signal processing circuit 31, etc.).
  • Scan electrode drive circuit 33 includes a ramp waveform generation unit, a sustain pulse generation unit, and a scan pulse generation unit (not shown in FIG. 5), and generates a drive voltage waveform based on a timing signal supplied from timing generation circuit 35. Then, the voltage is applied to each of scan electrode SC1 to scan electrode SCn.
  • the ramp waveform generator generates a forced initialization waveform and a selective initialization waveform to be applied to scan electrode SC1 through scan electrode SCn during the initialization period based on the timing signal.
  • the sustain pulse generator generates a sustain pulse to be applied to scan electrode SC1 through scan electrode SCn during the sustain period based on the timing signal.
  • the scan pulse generator includes a plurality of scan electrode drive ICs (scan ICs), and generates scan pulses to be applied to scan electrode SC1 through scan electrode SCn during the address period based on the timing signal.
  • Sustain electrode drive circuit 34 includes a sustain pulse generation unit and a circuit (not shown in FIG. 5) for generating voltage Ve, and generates and maintains a drive voltage waveform based on the timing signal supplied from timing generation circuit 35.
  • the voltage is applied to each of electrode SU1 through sustain electrode SUn.
  • a sustain pulse is generated based on the timing signal and applied to sustain electrode SU1 through sustain electrode SUn.
  • voltage Ve is generated based on the timing signal and applied to sustain electrode SU1 through sustain electrode SUn.
  • the data electrode drive circuit 32 includes the same number of switch circuits 36 as the data electrodes 22. In this embodiment, since the number of data electrodes 22 is “m”, the data electrode drive circuit 32 includes m switch circuits 36 (switch circuit 36 (1) to switch circuit 36 (m)). Each of the m switch circuits 36 (1) to 36 (m) corresponds to each of the m data electrodes D1 to Dm.
  • the data electrode drive circuit 32 generates an address pulse corresponding to each of the data electrodes D1 to Dm based on the display code of each color output from the image signal processing circuit 31 and the timing signal supplied from the timing generation circuit 35. .
  • the data electrode drive circuit 32 then writes a write pulse (write pulse voltage Vd or 0 (V) from the switch circuit 36 (1) to the switch circuit 36 (m) to the data electrode D1 to the data electrode Dm during the write period. )) Is applied.
  • the dedicated IC In order for the dedicated IC to operate normally, it is necessary to keep the power consumption, temperature, etc. within the predetermined range as the standard for the dedicated IC. For example, if the power consumption exceeds a predetermined upper limit of power consumption (allowable power loss), the dedicated IC may cause an abnormal operation. Therefore, in the image display device 30, the data electrode drive circuit 32 needs to operate so that the power consumption of the dedicated IC does not exceed a predetermined upper limit.
  • the display code is generated so as to reduce the power consumption of the data electrode driving circuit 32 while preventing the image display quality in the image display device 30 from deteriorating. Details of generation of the display code will be described later.
  • the object of the image signal processing circuit 31 in the present embodiment is to reduce the power consumption of the data electrode driving circuit 32 while preventing the image display quality in the image display device 30 from being deteriorated.
  • the image signal processing circuit 31 reduces the number of subfield codes used for displaying an image. Then, the image signal processing circuit 31 generates a second rule to be described later in order to reduce the number of subfield codes used for image display.
  • FIG. 6 is a diagram schematically showing an example of a circuit block constituting the image signal processing circuit 31 of the image display device 30 according to the embodiment of the present invention.
  • the image signal processing circuit 31 includes an attribute detection unit 41, a base code generation unit 50, a rule generation unit 61, a rule addition unit 62, an upper and lower code generation unit 70, and a display code selection unit 80.
  • the attribute detection unit 41 specifies the relationship between the image signal and the position of the pixel displaying the image signal.
  • the time differentiation of the image signal corresponding to each pixel determines whether each pixel is in the moving image area or the still image area. Detect if there is any.
  • a change in brightness is detected by spatial differentiation of the image signal (detecting a change in the image signal between adjacent pixels), and it is detected whether or not each pixel corresponds to the contour portion of the image. Then, those detection results are output as attributes of the image signal corresponding to each pixel.
  • a subfield code that is basic in subsequent signal processing is referred to as a “basic code”, and a code set including the base code is referred to as a “basic code set”.
  • the base code is a subfield code generated by lighting one by one or two in order from the subfield having the smallest gradation weight. Therefore, the base code is a subfield code in which a subfield having the largest gradation weight among the subfields to emit light and all subfields having a gradation weight smaller than that subfield emit light.
  • the base code generation unit 50 converts the tone value (hereinafter referred to as “input tone”) of the image signal input to the image signal processing circuit 31 from the base code set including a plurality of base codes. Based on the above, select “upper tone base code”.
  • the upper tone base code is a base code having a tone value larger than the input tone and having a tone value closest to the input tone. Accordingly, in the upper gradation base code, the subfield having the largest gradation weight among the lighting subfields and all subfields having the gradation weight smaller than that subfield are the lighting subfields.
  • the base code generation unit 50 selects a base code having a gradation value larger than the input gradation and closest to the input gradation, and outputs it as an upper gradation base code.
  • FIG. 7A is a diagram illustrating an example of a base code set used in the image display device 30 according to an embodiment of the present invention.
  • FIG. 7B is a diagram showing another example of the base code set used in the image display device 30 according to the embodiment of the present invention.
  • FIG. 7C is a diagram showing another example of the base code set used in the image display device 30 according to the embodiment of the present invention.
  • the light-emitting subfield is “1”
  • the non-light-emitting subfield is blank
  • each subfield code (base) is displayed in the second column from the left.
  • Code) represents the gradation value to be displayed.
  • the numerical value written immediately below the notation indicating each subfield in each base code set represents the gradation weight of each subfield.
  • the base code having the smallest gradation value is set to “1”, and the order in which the gradation values are assigned in order from the smallest is shown. Therefore, the numerical value indicated by this order is a numerical value indicating how small the gradation value of each basic code is among the basic codes included in the basic code set. That is, the numerical value indicated by this order represents the order Ns of the gradation values of the base code described later.
  • FIG. 7A shows an example of a base code set often used in the NTSC standard.
  • the base code set shown in FIG. 7A is composed of 8 subfields, and each subfield is “1”, “2”, “3”, “5”, “ It has gradation weights of “8”, “13”, “21”, and “34”.
  • the first subfield (subfield SF1) of one field is set to the subfield having the smallest gradation weight, and thereafter, the subfields are arranged so that the gradation weight is sequentially increased. . And it is set as a lighting subfield one by one in an order from the subfield with the smallest gradation weight. Therefore, the number of base codes included in this base code set is (the number of subfields constituting one field + 1). For example, in the example of the base code set shown in FIG. 7A, the number of base codes is nine.
  • FIG. 7B shows an example of a base code set often used in the PAL standard.
  • one field is composed of 12 subfields, and each subfield is “1”, “2”, “4”, “9”, “9” in order from the subfield SF1. It has gradation weights of “18”, “36”, “65”, “5”, “7”, “15”, “33”, “60”.
  • the base code set shown in FIG. 7B has two subfield groups.
  • the first subfield group is composed of subfields SF1 to SF7, and the second subfield group is composed of subfields SF8 to SF12.
  • Each subfield group has the first subfield of each subfield group (subfield SF1 and subfield SF8 in the example shown in FIG. 7B) as the subfield having the smallest gradation weight in each subfield group. Thereafter, the subfields are arranged so that the gradation weights are sequentially increased. In each subfield group, one or two lighting subfields are set in order from the subfield having the smallest gradation weight. Therefore, the number of base codes included in this base code set is equal to or less than (the number of subfields constituting one field + 1). For example, in the example of the base code set shown in FIG. 7B, the number of base codes is 10.
  • FIG. 7C shows an example of a base code set used in a 3D display device (stereoscopic display device).
  • one field is composed of five subfields, and each subfield is “1”, “16”, “8”, “4”, “ 2 "gradation weight.
  • the first subfield (subfield SF1) of one field is the subfield having the smallest gradation weight
  • the second subfield (subfield SF2) is the subfield having the largest gradation weight.
  • the subfields are arranged so that the gradation weights are sequentially reduced. And it is set as a lighting subfield one by one in an order from the subfield with the smallest gradation weight. Therefore, the number of base codes included in this base code set is (the number of subfields constituting one field + 1). For example, in the example of the base code set shown in FIG. 7C, the number of base codes is 6.
  • the image display device 30 in the present embodiment generates a new code set based on the base code set as described above, and converts the input gradation into a subfield code using the code set.
  • the base code generation unit 50 includes a base code storage unit 52 and a base code selection unit 54.
  • the base code storage unit 52 stores a base code set and gradation values of a plurality of base codes constituting the base code set. Each base code and each gradation value of the base code are stored in the base code storage unit 52 in association with each other.
  • the base code selection unit 54 compares each tone value of the base code constituting the base code set with the input tone. Then, a base code having a gradation value larger than the input gradation and closest to the input gradation is selected. Then, the selected base code is output as an upper gradation base code.
  • a new subcode not included in the base code set is obtained.
  • the rule generation unit 61 generates a first rule for generating this new subfield code.
  • the rule generation unit 61 generates a base code based on the image signal and the attribute (attribute associated with the image signal) detected by the attribute detection unit 41 in order to increase the number of subfield codes used for image display.
  • a first rule is generated when changing the lighting subfield in the upper gradation base code selected in the section 50 to the non-lighting subfield.
  • the first rule generated by the rule generation unit 61 defines a rule for changing the lighting subfield in the upper gradation base code to the non-lighting subfield.
  • the rule generated by the rule generation unit 61 restricts subfields to be changed from lighting to non-lighting in the upper gradation base code. This is because the gradation value of the new subfield code created by changing the lighting subfield to the non-lighting subfield in the upper gradation base code is smaller than the upper gradation base code. This is in order not to fall below.
  • the upper gradation base code allows unlimited subfields to change from lighting to non-lighting, all lighting subfields become non-lighting subfields, and subfield codes with a gradation value of “0” are generated. This is because there is a possibility that it may occur.
  • the first rule is generated so that the subfield code generated based on the rule has the next gradation value.
  • the “lower gradation base code” is a base code having a gradation value that is equal to or lower than the input gradation and closest to the input gradation.
  • the first rule generated by the rule generation unit 61 includes one or more of the following three rules. 1) A rule for setting the first subfield to be changed from the lighting subfield to the non-lighting subfield. 2) A rule for setting the second subfield to be changed from the lighting subfield to the non-lighting subfield. 3) A rule for setting a sub-field that prohibits non-lighting.
  • the rule adding unit 62 generates a second rule.
  • the second rule is provided to suppress the power consumption of the data electrode driving circuit 32 while preventing the image display quality in the image display device 30 from deteriorating.
  • the power consumption of the data electrode drive circuit 32 changes according to the number of subfield codes constituting the conversion table. As the number of subfield codes constituting the conversion table increases, the power consumption of the data electrode drive circuit 32 tends to increase. Conversely, if the number of subfield codes constituting the conversion table is reduced, the power consumption of the data electrode drive circuit 32 can be reduced.
  • the rule adding unit 62 generates a second rule based on a predetermined control signal (hereinafter referred to as “power control signal Cnt”) generated in a power estimation unit (not shown).
  • the second rule is a rule for limiting the upper limit of the number of subfield codes that can be generated based on the first rule generated by the rule generation unit 61, and prohibiting it from being turned off is prohibited. This is a rule for subfields. As the number of subfields prohibited from being turned off increases, the number of subfields newly generated from the upper gradation base code decreases, and the power consumption of the data electrode driving circuit 32 is further suppressed.
  • a power estimation unit (not shown) estimates power consumption in the image display device 30 based on an image signal, temperature, and the like. Then, the power estimation unit decreases the numerical value of the power control signal Cnt if the estimated value of power consumption is large, and increases the numerical value of the power control signal Cnt if the estimated value of power consumption is small, and outputs the power control signal Cnt. To do.
  • the method for estimating the power consumption in the power estimation unit may be a generally known power estimation method. For example, if the design of an image is detected, the estimated power consumption is increased if the design is fine, and the estimated power consumption is decreased if the design is small. A method of increasing the value or a method of increasing the estimated value of power consumption when the temperature of the image display device 30 rises may be used.
  • the power control signal Cnt is a real number equal to or greater than “0” and is continuously changed according to the change of the image signal.
  • the power control signal Cnt is not limited to this.
  • the number of intermediate codes that can be generated by the intermediate code generation unit 72 described later increases or decreases in accordance with the increase or decrease of the value of the power control signal Cnt. If the value of the power control signal Cnt decreases, the number of intermediate codes that can be generated by the intermediate code generation unit 72 decreases, and if the value of the power control signal Cnt increases, it can be generated by the intermediate code generation unit 72. The number of intermediate codes increases.
  • the maximum power consumption of the data electrode drive circuit 32 is relatively large. If the value of the power control signal Cnt is relatively small, the maximum value of power consumption of the data electrode driving circuit 32 is relatively reduced.
  • FIG. 8 is a diagram schematically showing an example of a circuit block constituting the rule adding unit 62 of the image display device 30 according to the embodiment of the present invention.
  • the rule adding unit 62 includes a random number generator 91, an adder 92, a decimal truncator 93, a subtracter 94, and a selector 95.
  • the random number generator 91 generates a random number rnd between “0” and less than “1”.
  • the adder 92 adds the power control signal Cnt and the random number rnd.
  • the decimal truncator 93 truncates the decimal part of the numerical value output from the adder 92 and outputs the integer part.
  • the INT (x) described above is a function that obtains only the integer part by truncating the decimal part of x. Max (x, y) is a function for obtaining the larger one (including the case where x and y are equal).
  • the order Ns of gradation values of the base code is a numerical value representing the smallest order of the gradation value of the base code of interest in the base code included in the base code set. Accordingly, the base code of the order Ns indicates that the gradation value is the Nsth smallest in the base code set. For example, in the base code set shown in FIG. 7A, the order Ns of the base code “11111100” with the gradation value “32” is “7”.
  • the selector 95 selects a base code having the Np-th smallest gradation value from the base code set, and outputs it to the intermediate code generation unit 72.
  • the lighting subfield in the base code selected in this way is a subfield that is prohibited from being turned off.
  • This rule is the second rule in the present embodiment.
  • the lighting subfields are subfield SF1 and subfield SF2. Therefore, in the second rule generated at this time, the subfields that are prohibited from being turned off are the subfield SF1 and the subfield SF2.
  • the lighting subfields are subfields SF1 to SF5. Therefore, in the second rule generated at this time, the subfields prohibited from being turned off are subfield SF1 to subfield SF5.
  • lighting subfields are subfields SF1 to SF3, subfield SF8, and subfield SF9. Therefore, in the second rule generated at this time, the subfields that are prohibited from being turned off are subfield SF1, subfield SF3, subfield SF8, and subfield SF9.
  • the second rule generated by the rule adding unit 62 has a gradation value smaller than the base code generated by the base code generating unit 50 and is selected by the selector 95. This is a rule for prohibiting unlit subfields that are lit in the base code.
  • the upper / lower code generation unit 70 applies the first rule generated by the rule generation unit 61 and the second rule generated by the rule addition unit 62 to the upper gradation base code output from the base code generation unit 50.
  • the upper gradation code and the lower gradation code are generated.
  • the upper gradation code has a gradation value that is larger than the input gradation and closest to the input gradation among the subfield codes that can be newly generated based on the first rule and the second rule. It is a subfield code.
  • the lower gradation code is a sub-field code that can be newly generated based on the first rule and the second rule. It is a subfield code having.
  • the upper / lower code generation unit 70 includes an intermediate code generation unit 72 and an upper / lower code selection unit 74.
  • the intermediate code generation unit 72 sets the lighting subfield in the upper gradation base code to the non-lighting subfield. Change to generate a new subfield code.
  • the newly generated subfield code is referred to as “intermediate code”.
  • a set obtained by adding the original upper tone base code to these intermediate codes is referred to as an “intermediate code set”.
  • the intermediate code is a subfield code used when displaying an image on panel 10. Therefore, each discharge cell of panel 10 emits light with a luminance of a gradation value based on the intermediate code.
  • FIG. 9A is a diagram illustrating an example of an intermediate code set generated by the intermediate code generation unit 72 of the image display device 30 according to the embodiment of the present invention.
  • FIG. 9B is a diagram illustrating another example of the intermediate code set generated by the intermediate code generation unit 72 of the image display device 30 according to the embodiment of the present invention.
  • FIG. 9C is a diagram illustrating another example of the intermediate code set generated by the intermediate code generation unit 72 of the image display device 30 according to the embodiment of the present invention.
  • the light-emitting subfield is “1”
  • the non-light-emitting subfield is blank
  • the second column from the left is the subfield code (intermediate code).
  • Code represents the gradation value to be displayed.
  • the numerical value written immediately below the notation indicating each subfield in each intermediate code set represents the gradation weight of each subfield.
  • one field includes eight subfields, and each subfield is “1”, “2”, and “3” in order from the subfield SF1. , “5”, “8”, “13”, “21”, “34”.
  • FIG. 9A as an example of the intermediate code set, “1) Rules for setting the first subfield to be changed from the lighting subfield to the non-lighting subfield” are shown in the gradation shown in FIG. 7A.
  • rule 1 This “1) rule for setting the first subfield to be changed from a lighting subfield to a non-lighting subfield” is a rule that “one of the lighting subfields is changed to a non-lighting subfield”. (Hereinafter referred to as “rule 1”).
  • the subfield code “11111000” obtained by changing the subfield SF6 to the non-lighting subfield is equal to the base code (order .6) of the gradation value “19” illustrated in FIG. 7A. Accordingly, five subfield codes excluding the subfield code “11111000” are newly generated intermediate codes.
  • FIG. 9B as an example of the intermediate code set, in addition to the above-described rule 1, “2) a rule for setting the second subfield to be changed from the lighting subfield to the non-lighting subfield” is shown in FIG.
  • Rule 2 for setting the second subfield to be changed from the lighting subfield to the non-lighting subfield is “the subfield code having the smallest gradation value among the newly generated intermediate codes”.
  • the sub-field SF2 is a non-lighting sub-field ”(hereinafter referred to as“ rule 2 ”).
  • FIG. 9C as an example of the intermediate code set, in addition to the above-described rule 1, “3) a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “A” a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “A” a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “A” a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “ An intermediate code set generated by applying to the base code “11111100” of “32” is shown.
  • rule for setting a subfield that prohibits non-lighting is a rule that “subfield SF1 and subfield SF2 are prohibited from being non-lighting subfield” (hereinafter “rule”). 3 ”).
  • sub-field code in which sub-field SF1 or sub-field SF2 is a non-lighting sub-field has a sub-field code “10111100” with a gradation value “30” and a gradation value “ 31 ”is a sub-field code“ 01111100 ”.
  • the subfield codes having the gradation value “30” and the gradation value “31” are excluded from the intermediate code set.
  • rule 1 and rule 3 are used as the first rule.
  • rule 2 may be added to the first rule.
  • the image display device 30 displays an image with relatively low power consumption, or when an image with relatively little occurrence of moving image pseudo contour is displayed, the number of intermediate codes generated can be increased. It is. Then, by increasing the number of intermediate codes generated, an image can be displayed with a smoother gradation change.
  • the intermediate code generation unit 72 sets the lighting subfield in the upper gradation base code to the non-lighting sub-field based on the first rule generated by the rule generation unit 61 and the second rule generated by the rule addition unit 62. Change to field to generate intermediate code and generate intermediate code set.
  • FIGS. 9A, 9B, and 9C show an example in which an intermediate code set is generated based only on the first rule. An example of generating an intermediate code set based on the second rule in addition to the first rule will be described later.
  • the intermediate code generation unit 72 applies the first rule generated by the rule generation unit 61 to the upper gradation base code output from the base code generation unit 50 to generate an intermediate code, Generate an intermediate code set.
  • the intermediate code generation unit 72 generates an intermediate code from the upper gradation base code based on the first rule generated by the rule generation unit 61 and the second rule generated by the rule addition unit 62, and the intermediate code
  • FIG. 9D shows the intermediate code generation unit 72 based on the first rule generated by the rule generation unit 61 of the image display device 30 and the second rule generated by the rule addition unit 62 in the embodiment of the present invention. It is a figure which shows an example of the intermediate
  • FIG. 9E shows the intermediate code generation unit 72 based on the first rule generated by the rule generation unit 61 of the image display device 30 and the second rule generated by the rule addition unit 62 of the image display device 30 according to the embodiment of the present invention. It is a figure which shows another example of the intermediate code set produced
  • the base code generation unit 50 selects the base code having the gradation value “32” based on the input gradation as the upper gradation base code from the base code set shown in FIG. 7A, and the first rule is , Rule 1 “Change any one of the lighting subfields to a non-lighting subfield”.
  • the intermediate code generation unit 72 generates the code set shown in FIG. 9A based on the input gradation and the first rule. Shows an intermediate code set generated by applying the second rule.
  • the subfield code in which any of the subfield SF1, the subfield SF2, and the subfield SF3 is not lit is “11011100” with the gradation value “29” and the gradation value “30”. "10111100” and "01111100” of the gradation value "31”. Therefore, these subfield codes violate the second rule.
  • the subfield codes in which any one of the subfields SF1 to SF4 is not lit are “11101100” with the gradation value “27” and “11011100” with the gradation value “29”.
  • the subfield code of “11110100” of the gradation value “24” excluding the gradation value “27”, the gradation value “29”, the gradation value “30”, and the gradation value “31” is the first field code.
  • the intermediate code is newly generated based on the rule and the second rule. Thus, the intermediate code set shown in FIG. 9E is obtained.
  • the random number rnd is added to the power control signal Cnt, so that the output Np of the rule adding unit 62 is The probability is “2” or “1” according to the magnitude of the power control signal Cnt. If the power control signal Cnt is a numerical value close to “2”, the probability that the output Np is “2” is high, and if the power control signal Cnt is a numerical value close to “1”, the probability that the output Np is “1”. Becomes higher.
  • the output Np of the rule adding unit 62 is “2”
  • the intermediate code set shown in FIG. 9D is obtained
  • the intermediate code set shown in FIG. 9E is obtained. Therefore, if the power control signal Cnt is a numerical value close to “2”, there is a high probability that two subfield codes of gradation value “24” and gradation value “27” are newly generated as intermediate codes, If the power control signal Cnt is a numerical value close to “1”, the probability that only one subfield code having the gradation value “24” as the intermediate code is newly generated becomes high.
  • the intermediate code generation unit 72 uses the first rule generated by the rule generation unit 61 and the second rule generated by the rule addition unit 62 based on the upper gradation base code output from the base code generation unit 50. By applying the above rule, an intermediate code is generated and an intermediate code set is generated.
  • the number of intermediate codes generated by the intermediate code generation unit 72 continuously changes based on the power control signal Cnt.
  • the upper / lower code selection unit 74 compares each gradation value of the subfield code constituting the intermediate code set generated by the intermediate code generation unit 72 with the input gradation. Then, the upper / lower code selection unit 74 selects a subfield code having a gradation value larger than the input gradation and closest to the input gradation, and outputs it as an upper gradation code. In addition, the upper / lower code selection unit 74 selects a subfield code having a gradation value equal to or lower than the input gradation and closest to the input gradation, and outputs it as a lower gradation code.
  • the display code selection unit 80 calculates a gradation value to be displayed on the target pixel by adding a predetermined value to the input gradation. Then, the display code selection unit 80 selects one of the upper gradation code and the lower gradation code that has a gradation value closer to the gradation value to be displayed on the target pixel, and outputs it as a display code.
  • the pixel of interest is a pixel that is a target of calculation of a gradation value at that time.
  • the above-described predetermined value added to the input gradation is an error diffused by the error diffusion process and a dither value calculated by the dither process. Therefore, the display code selection unit 80 adds the error and the dither value to the input gradation to calculate the gradation value to be displayed on the target pixel, and selects the target pixel from the upper gradation code and the lower gradation code. The one having a gradation value closer to the gradation value to be displayed is selected as a display code. Further, the display code selection unit 80 calculates the difference between the gradation value to be displayed on the target pixel and the gradation value of the display code, and diffuses the difference as an error to surrounding pixels.
  • the display code selection unit 80 includes a dither selection unit 82, an error diffusion unit 84, and a display code determination unit 86.
  • the dither selection unit 82 stores a plurality of dither patterns. Then, one dither pattern is selected from a plurality of stored dither patterns based on the image signal and the attribute detected by the attribute detection unit 41.
  • the dither selection unit 82 selects a dither element corresponding to the position of the pixel from the selected dither pattern based on the position of the pixel displaying the image signal. Further, the dither selection unit 82 calculates the dither value by multiplying the selected dither element by the difference between the gradation value of the upper gradation code and the gradation value of the lower gradation code.
  • FIG. 10A is a diagram illustrating an example of a dither pattern used in the image display device 30 according to an embodiment of the present invention.
  • FIG. 10B is a diagram showing another example of the dither pattern used in the image display device 30 according to the embodiment of the present invention.
  • one column represents one pixel.
  • FIG. 10A shows the simplest binary dither.
  • “+0.25” and “ ⁇ 0.25” are arranged in a checkered pattern as dither elements.
  • FIG. 10B is a diagram showing an example of quaternary dither. In FIG. 10B, dither elements “+0.375”, “+0.125”, “ ⁇ 0.375” and “ ⁇ 0.125” are arranged.
  • the error diffusion unit 84 outputs an error to be added to the target pixel to the display code determination unit 86 and diffuses the error output from the display code determination unit 86 to the peripheral pixels of the target pixel.
  • the dither selection unit 82 stores, for example, the two types of dither patterns shown in FIGS. 10A and 10B, and selects either one of the dither patterns based on the image signal and the attribute detected by the attribute detection unit 41. .
  • the dither pattern shown in FIG. 10A is selected, the dither element is either “+0.25” or “ ⁇ 0.25”.
  • the dither element shown in FIG. 10B is selected, the dither element is “+0”. .375 ”,“ +0.125 ”,“ ⁇ 0.375 ”, and“ ⁇ 0.125 ”.
  • the dither selection unit 82 selects any one of these dither elements based on the position of the pixel displaying the image signal. Further, the dither value is calculated by multiplying the selected dither element by the difference between the tone value of the upper tone code and the tone value of the lower tone code. The calculated dither value is added to the input gradation in the display code selection unit 80.
  • FIG. 11 is a diagram showing error diffusion coefficients of the error diffusion unit 84 of the image display device 30 according to the embodiment of the present invention.
  • one column represents one pixel.
  • the middle column in FIG. 11 represents a pixel (target pixel) that is a target of error diffusion processing.
  • the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged at the upper left of the target pixel by the diffusion coefficient k1 to the target pixel. Further, the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged on the target pixel by the diffusion coefficient k2 to the target pixel. Further, the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged at the upper right of the target pixel by the diffusion coefficient k3 to the target pixel. Further, the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged on the left of the target pixel by the diffusion coefficient k4 to the target pixel.
  • the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k4 to the pixel arranged on the right side of the target pixel. Further, the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k3 to the pixel arranged at the lower left of the target pixel. Further, the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k2 to the pixel arranged below the target pixel. Further, the error diffusion unit 84 diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k1 to the pixel arranged at the lower right of the target pixel.
  • which diffusion coefficient is selected is determined using a random number generated by a random number generator (not shown).
  • the display code determination section 86 Based on the input gradation, the dither value output from the dither selection section 82, and the error output from the error diffusion section 84, the display code determination section 86 converts the display code actually used for image display into the upper gradation code. Alternatively, it is determined as one of the lower gradation codes.
  • the display code determination unit 86 calculates a gradation value to be displayed on the target pixel by adding the dither value and the error to the input gradation.
  • the display code is selected as the display code.
  • the display code determination unit 86 calculates the difference between the gradation value to be displayed on the target pixel and the gradation value of the display code, and outputs the difference to the error diffusion unit 84 as a newly generated error.
  • the image signal processing circuit 31 operates based on the following conditions.
  • the base code set shown in FIG. 7A is used as the base code set.
  • the rules used in the description of FIG. 9A are used. That is, rule 1 “change any one of the lighting subfields to a non-lighting subfield” is used. 3) Based on the attribute accompanying the image signal, “Rule for setting sub-field forbidden to turn off” (rule 3) is added to rule 1. 4) Furthermore, a second rule is generated, a subfield for prohibiting non-lighting based on the power control signal Cnt is set, and used together with the first rule.
  • FIG. 12 is a flowchart showing the operation of the image signal processing circuit 31 of the image display device 30 according to the embodiment of the present invention.
  • the image signal processing circuit 31 executes the following series of steps.
  • Step S41 An image signal corresponding to one pixel (target pixel) is input to the image signal processing circuit 31.
  • the attribute detection unit 41 detects an attribute associated with the image signal.
  • the image signal corresponding to the target pixel has a gradation value (input gradation) of “25”, and the attribute detection unit 41 detects that the attribute associated with the image signal is a moving image and a contour portion.
  • the description will be given on the assumption that it was obtained.
  • Step S50 The base code generation unit 50 selects an upper tone base code corresponding to the image signal.
  • step S50 the sub-field code having a gradation value that is larger than the gradation value of the image signal at the target pixel and closest to the gradation value of the image signal at the target pixel is selected from the plurality of basic sub-field codes.
  • the field code is selected as the upper gradation base code.
  • the base code generation unit 50 compares each tone value of the base code constituting the base code set stored in the base code storage unit 52 with the input tone. Then, a base code having a gradation value larger than the input gradation and closest to the input gradation is selected and output as an upper gradation base code.
  • the base code generation unit 50 selects the base code “11111100” having the gradation value “32” and outputs it as the upper gradation base code.
  • Step S61 The rule generation unit 61 generates a first rule for generating an intermediate code set.
  • step S61 based on the image signal at the target pixel, the first rule for generating a new subfield code by changing the light emitting subfield in the upper gradation base code to the non-light emitting subfield is generated. To do.
  • the rule generation unit 61 performs a basic rule (rule 1) “change any one of the lighting subfields to the non-lighting subfield” if the attribute attached to the image signal is a still image. ) Is generated.
  • the rule generation unit 61 restricts the subfield codes that can be used for displaying the image in order to suppress the moving image pseudo contour.
  • the subfield codes include those that have a high effect of suppressing moving image pseudo contours and those that do not.
  • the base codes shown in FIGS. 7A to 7C are subfield codes that have a high effect of suppressing the moving image pseudo contour.
  • the appearance of the moving image pseudo contour depends on the subfield code that can be used to display the image, and the image is displayed using the subfield code that is highly effective in suppressing the moving image pseudo contour.
  • the moving image pseudo contour can be suppressed.
  • the subfield code that can be used for displaying an image is limited as compared with the case where the suppression of the moving image pseudo contour is unnecessary. This is the reason why the rule generation unit 61 restricts the subfield codes that can be used for image display in order to suppress the moving image pseudo contour.
  • the rule generating unit 61 sets “a subfield that prohibits non-lighting” in the basic rule 1 in order to suppress the moving image pseudo contour. Add “When the rule”.
  • This additional rule is, for example, rule 3 described with reference to FIG. 9C, that “subfield SF1 and subfield SF2 are prohibited from being non-lighting subfields”.
  • the rule generation unit 61 limits the subfield codes that can be used for displaying an image.
  • the first rule generated by the rule generating unit 61 when the attribute associated with the image signal is a moving image is that the attribute associated with the image signal is a still image. (That is, when the image signal at the target pixel is a still image), the first rule generated by the rule generation unit 61 is included.
  • Step S62 The rule adding unit 62 generates a second rule based on the power control signal Cnt.
  • step S62 the rule adding unit 62 performs the following.
  • the adder 92 adds the power control signal Cnt and the random number rnd.
  • the decimal truncator 93 truncates the decimal part of the numerical value output from the adder 92 and outputs the integer part.
  • the subtractor 94 calculates Np from the following formula based on the order Ns of the gradation values of the upper gradation base code in the base code set and the output of the decimal truncator 93.
  • Np Max (1, (Ns ⁇ INT (Cnt + rnd) ⁇ 1))
  • the selector 95 selects a base code having the Npth smallest gradation value from the base code set.
  • the lighting subfield in the selected base code is a subfield that is prohibited from being unlit.
  • the second rule is generated in this way.
  • the base code with the fifth lowest gray scale weight in the base code set shown in FIG. 7A is “11110000” with the gray scale value “11”. Therefore, the rule adding unit 62 generates a second rule that “prohibits each subfield from subfield SF1 to subfield SF4 from being unlit”.
  • Step S72 The intermediate code generation unit 72 generates an intermediate code set.
  • the intermediate code generation unit 72 generates an intermediate code from the upper gradation base code based on the first rule generated by the rule generation unit 61 and the second rule generated by the rule addition unit 62, Generate an intermediate code set.
  • the base code generation unit 50 selects the base code having the gradation value “32” based on the input gradation from the base code set shown in FIG. 7A as the upper gradation base code, and the rule generation unit 61 sets the first code.
  • Rule 1 “Change any one of the lighting subfields to a non-lighting subfield” is generated as a rule of the rule, and the rule adding unit 62 “turns off each subfield from subfield SF1 to subfield SF4. It is assumed that a second rule “prohibit” is generated.
  • the intermediate code generation unit 72 generates the code set shown in FIG. 9A from the upper gradation base code of the gradation value “32” and the first rule. Then, based on the second rule, in the code set shown in FIG. 9A, it is prohibited to turn off each of the subfields from subfield SF1 to subfield SF4.
  • the intermediate code set shown in FIG. 9E is generated.
  • the upper / lower code selection unit 74 selects an upper gradation code and a lower gradation code.
  • step S74 the target pixel larger than the tone value of the image signal in the target pixel is selected from the intermediate code set generated by applying the first rule and the second rule described above to the upper tone base code.
  • the subfield code having the gradation value closest to the gradation value of the image signal at is selected as the upper gradation code, and the gradation value of the image signal at the target pixel is equal to or lower than the gradation value of the image signal at the target pixel
  • the subfield code having the closest gradation value is selected as the lower gradation code.
  • the upper / lower code selection unit 74 compares each gradation value of the subfield code constituting the intermediate code set with the input gradation. Then, a subfield code having a gradation value larger than the input gradation and closest to the input gradation is selected and output as an upper gradation code. Also, a subfield code having a gradation value that is equal to or lower than the input gradation and closest to the input gradation is selected, and is output as a lower gradation code.
  • the subfield code corresponding to the upper gradation code is gradation. This is a subfield code of the value “32”.
  • the subfield code corresponding to the lower gradation code is a subfield code having a gradation value of “24”. Therefore, the upper / lower code selection unit 74 selects the subfield code “11111100” having the gradation value “32” as the upper gradation code, and the subfield code “11110100” having the gradation value “24” as the lower gradation code. ”Is selected.
  • Step S82 The dither selection unit 82 selects a dither element based on the attribute of the image signal.
  • the dither selection unit 82 uses the attribute detected by the image signal and attribute detection unit 41. Based on the above, one of the dither patterns is selected.
  • the dither pattern shown in FIG. 10A is selected. If the attribute attached to the image signal is not a contour portion, the dither pattern shown in FIG. 10B is selected. If the selection unit 82 is set, when the attribute attached to the image signal is a contour portion, the dither selection unit 82 selects the dither pattern shown in FIG. 10A. Then, the dither selection unit 82 selects one of the dither elements set in the dither pattern based on the position of the target pixel. For example, the dither selection unit 82 selects “0.25” as the dither element based on the dither pattern shown in FIG. 10A.
  • Step S83 The dither selector 82 calculates a dither value.
  • the dither selection unit 82 calculates the dither value by multiplying the selected dither element by the difference between the tone value of the upper tone code and the tone value of the lower tone code.
  • the upper gradation code selected in step S74 is the gradation value “32”
  • the gradation value of the lower gradation code selected in step S74 is “24”
  • the dither selected in step S82 If the element is “0.25”, the dither selection unit 82 multiplies the difference “8” between the gradation value of the upper gradation code and the gradation value of the lower gradation code by the dither element “0.25”.
  • the dither value “2.0” is calculated.
  • Step S86 The display code determination unit 86 calculates a gradation value to be displayed on the target pixel.
  • step S86 a predetermined value is added to the gradation value of the image signal at the target pixel to calculate the gradation value to be displayed on the target pixel.
  • the display code determination unit 86 adds the dither value calculated in step S83 to the input gradation, and further adds the error output from the error diffusion unit 84 based on the calculation result in step S88.
  • the gradation value to be displayed on the target pixel is calculated. Therefore, the predetermined value described above is a numerical value obtained by adding the dither value output from the dither selection unit 82 and the error output from the error diffusion unit 84.
  • the input gradation is the gradation value “25”
  • the dither value calculated in step S83 is “2.0”
  • the input gradation is the gradation value “25”
  • the dither value calculated in step S83 is “2.0”
  • the error output from the error diffusion unit 84 based on the calculation result in step S88 is “ +0.4 ”
  • 25 + 2.0 + 0.4 27.4. Therefore, the gradation value to be displayed on the target pixel is “27.4”.
  • Step S87 The display code determining unit 86 determines a display code to be used when displaying the gradation value on the target pixel.
  • step S87 the upper gradation code and the lower gradation code having the gradation value closer to the gradation value to be displayed on the target pixel is selected as the display code.
  • the display code determination unit 86 compares the gradation value to be displayed on the target pixel with the gradation value of the upper gradation code and the gradation value of the lower gradation code. If the gradation value to be displayed on the target pixel is closer to the gradation value of the upper gradation code than the gradation value of the lower gradation code, the display used when displaying the gradation value on the attention pixel Select the upper gradation code as the code and output it. Further, when the gradation value to be displayed on the target pixel is closer to the gradation value of the lower gradation code than the gradation value of the upper gradation code, it is used when displaying the gradation value on the attention pixel. The lower gradation code is selected as the display code and is output.
  • the display code determination unit 86 outputs the lower gradation code “11110100” having the gradation value “24” as the display code.
  • the display code determination unit 86 outputs the lower gradation code “11111100” having the gradation value “32” as the display code.
  • Step S88 The display code determination unit 86 calculates the error and outputs it to the error diffusion unit 84.
  • the display code determination unit 86 subtracts the gradation value of the display code from the gradation value to be displayed on the target pixel, and outputs the subtraction result to the error diffusion unit 84 as a newly generated error.
  • the display code determination unit 86 outputs “1.4” as an error to the error diffusion unit 84.
  • the display code determination unit 86 outputs this “ ⁇ 4.6” as an error to the error diffusion unit 84.
  • step S88 When step S88 is completed, the process returns to step S41. In this way, a series of steps from step S41 to step S88 are repeatedly executed.
  • the image signal processing circuit 31 in the present embodiment includes the base code generation unit 50, the rule generation unit 61, the rule addition unit 62, the upper and lower code generation unit 70, and the display code selection unit 80.
  • the base code generation unit 50 selects a base code having a gradation value larger than the input gradation and closest to the input gradation from the base code set, and outputs it as an upper gradation base code.
  • the rule generation unit 61 illuminates the upper gradation base code based on the image signal and the attribute (attribute associated with the image signal) detected by the attribute detection unit 41 in order to generate an intermediate code used for image display.
  • a first rule for changing a subfield to a non-lighting subfield is generated.
  • the rule adding unit 62 generates a second rule that limits the upper limit of the number of subfield codes generated based on the first rule generated by the rule generating unit 61 based on the power control signal Cnt.
  • the upper / lower code generation unit 70 applies the first rule generated by the rule generation unit 61 and the second rule generated by the rule addition unit 62 to the upper gradation base code output from the base code generation unit 50.
  • Generate intermediate code An upper gradation code having a gradation value larger than the input gradation and closest to the input gradation, and a lower gradation code having a gradation value equal to or lower than the input gradation and closest to the input gradation Is selected from the intermediate code and output.
  • the display code selection unit 80 adds an error and a dither value to the input gradation, and calculates a gradation value to be displayed on the target pixel. Then, of the upper gradation code and the lower gradation code, the one having a gradation value closer to the gradation value to be displayed on the target pixel is selected and output as a display code. Further, the display code selection unit 80 calculates a difference between the gradation value to be displayed on the target pixel and the gradation value of the display code, and diffuses the difference as an error to surrounding pixels.
  • conversion from an image signal to a display code can be performed by calculation using an arithmetic circuit. Therefore, even in such an image display apparatus, it is not necessary to provide a huge number of conversion tables, and a minimum necessary table (for example, the base code set shown in FIGS. 7A, 7B, and 7C) and an image signal It is only necessary to provide an arithmetic circuit for converting from to display code.
  • a second rule for setting a subfield that prohibits non-lighting is generated based on the power control signal Cnt and applied to the generation of the display code.
  • the conversion from the image signal to the subfield code can be performed by the logical operation, and the data electrode drive circuit is prevented while preventing the image display quality from being deteriorated.
  • the power consumption in 32 can be suppressed.
  • the value of the power control signal Cnt is approximately equal to the number of intermediate codes that can be generated by the intermediate code generation unit 72. Therefore, the number of intermediate codes generated from a base code having a relatively large gradation value is substantially equal to the number of intermediate codes generated from a base code having a relatively small gradation value. Therefore, in the display image, the smoothness of the gradation in the bright area is almost the same as the smoothness of the gradation in the dark area.
  • the smoothness of gradation in the display image is deteriorated in order from the dark area, and the damage is greatly impaired. Therefore, there is a possibility that the user may recognize a decrease in image display quality in a dark region.
  • the smoothness of the gradation in the bright area and the smoothness of the gradation in the dark area are substantially the same. For this reason, in the display image, it is difficult for the user to recognize that the image display quality is deteriorated in a specific brightness region.
  • the number of intermediate codes generated by the intermediate code generation unit 72 changes continuously based on the power control signal Cnt. Therefore, the change in image display quality when the power control signal Cnt changes continuously is also continuous. Therefore, it is possible to prevent the user from recognizing a sudden change in the image display quality.
  • the dither processing and error diffusion processing are performed after setting the subfield for prohibiting the write operation. Therefore, even in the image display device 30 that selects a display code from an intermediate code set having a limited number of subfield codes and uses it to display an image, it is possible to prevent a decrease in image display quality.
  • the configuration in which the base code generation unit 50 has the base code storage unit 52 and the base code set is stored in advance in the base code storage unit 52 has been described.
  • the present invention is not limited to this configuration.
  • a configuration may be adopted in which a rule for generating a base code is determined in advance and the base code is generated based on the rule.
  • the upper and lower code generation unit 70 selects the upper gradation code and the lower gradation code by the upper and lower code selection unit 74 after the intermediate code set is generated by the intermediate code generation unit 72.
  • the present invention is not limited to this configuration.
  • an intermediate code is generated in order of increasing gradation value, and at the same time, the intermediate code and the input gradation are sequentially compared to select the upper gradation code and the lower gradation code.
  • the present invention is not limited to this configuration.
  • the dither selection unit 82 can be omitted.
  • the error diffusion unit 84 can be omitted.
  • the image display quality may be lowered, so care must be taken.
  • the number of subfields constituting one field, the subfields that are forced initialization subfields, the gradation weights of each subfield, and the like are not limited to the above-described numerical values. Moreover, the structure which switches a subfield structure based on an image signal etc. may be sufficient.
  • the drive voltage waveform shown in FIG. 3 is merely an example in the embodiment of the present invention, and the present invention is not limited to this drive voltage waveform.
  • circuit configurations shown in FIGS. 5, 6, and 8 are merely examples in the embodiment of the present invention, and the present invention is not limited to these circuit configurations.
  • each circuit block shown in the embodiment of the present invention may be configured as an electric circuit that performs each operation shown in the embodiment, or a microcomputer that is programmed to perform the same operation. May be used.
  • the number of subfields constituting one field is not limited to the above number.
  • the number of gradations that can be displayed on the panel 10 can be further increased.
  • the time required for driving panel 10 can be shortened by reducing the number of subfields.
  • one pixel is constituted by discharge cells of three colors of red, green, and blue.
  • a panel in which one pixel is constituted by discharge cells of four colors or more has been described.
  • the specific numerical values shown in the embodiment of the present invention are set based on the characteristics of the panel 10 having a screen size of 50 inches and the number of display electrode pairs 14 of 1024. It is just an example.
  • the present invention is not limited to these numerical values, and each numerical value is desirably set optimally in accordance with panel specifications, panel characteristics, plasma display device specifications, and the like. Each of these numerical values is allowed to vary within a range where the above-described effect can be obtained.
  • the number of subfields constituting one field, the gradation weight of each subfield, and the like are not limited to the values shown in the embodiment of the present invention, and the subfield configuration is based on an image signal or the like. May be configured to switch.
  • the present invention since conversion from an image signal to a subfield code can be performed by calculation, it is not necessary to use a conversion table composed of a large number of subfield codes, and power consumption can be prevented while preventing deterioration in image display quality. Therefore, the present invention is useful as an image display device that displays an image in an image display region by combining binary control of light emission and non-light emission in a light emitting element that constitutes a pixel, and a driving method of the image display device.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Power Engineering (AREA)
  • Plasma & Fusion (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

Selon l'invention, la conversion d'un signal d'image en un code de sous-champ dans un dispositif de visualisation d'image est calculée sans recours à une table de conversion. A cette fin, le dispositif de visualisation d'image comprend une unité de génération de code de base (50), une unité de génération de règles (61), une unité d'ajout de règles (62), une unité de génération de code supérieur/inférieur (70), et une unité de sélection de code d'affichage (80). L'unité de génération de code de base (50) sélectionne un code de base de gradient supérieur à partir d'une pluralité de codes de sous-champ de base. L'unité de génération de règles (61) génère une première règle destinée à générer de nouveaux codes de sous-champ à partir du code de base de gradient supérieur. L'unité d'ajout de règles (62) génère une seconde règle destinée à définir un sous-champ pour empêcher que les codes de sous-champ devant être générés par la première règle ne deviennent non émetteurs, sur la base d'un signal de commande prescrit. L'unité de génération de code supérieur/inférieur (70) génère un code de gradient supérieur et un code de gradient inférieur; et l'unité de sélection de code d'affichage (80) sélectionne un code d'affichage parmi le code de gradient supérieur et le code de gradient inférieur.
PCT/JP2012/000300 2011-01-20 2012-01-19 Dispositif de visualisation d'image et procédé de commande pour dispositif de visualisation d'image WO2012098888A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11231827A (ja) * 1997-07-24 1999-08-27 Matsushita Electric Ind Co Ltd 画像表示装置及び画像評価装置
JP2002023692A (ja) * 2000-07-04 2002-01-23 Matsushita Electric Ind Co Ltd 表示装置および表示方法
JP2003228319A (ja) * 2002-02-01 2003-08-15 Pioneer Electronic Corp ディスプレイパネルの駆動方法
JP2005301273A (ja) * 2004-04-09 2005-10-27 Samsung Electronics Co Ltd ディスプレイ装置及びその制御方法
JP2005321775A (ja) * 2004-05-01 2005-11-17 Samsung Electronics Co Ltd ディスプレー装置
JP2008051949A (ja) * 2006-08-23 2008-03-06 Fujitsu Hitachi Plasma Display Ltd 階調表示処理方法及びプラズマディスプレイ装置
JP2008083564A (ja) * 2006-09-28 2008-04-10 Fujitsu Hitachi Plasma Display Ltd 多階調表示方法及び装置
WO2009139151A1 (fr) * 2008-05-14 2009-11-19 パナソニック株式会社 Dispositif d’écran plasma et procédé de commande d’écran plasma

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11231827A (ja) * 1997-07-24 1999-08-27 Matsushita Electric Ind Co Ltd 画像表示装置及び画像評価装置
JP2002023692A (ja) * 2000-07-04 2002-01-23 Matsushita Electric Ind Co Ltd 表示装置および表示方法
JP2003228319A (ja) * 2002-02-01 2003-08-15 Pioneer Electronic Corp ディスプレイパネルの駆動方法
JP2005301273A (ja) * 2004-04-09 2005-10-27 Samsung Electronics Co Ltd ディスプレイ装置及びその制御方法
JP2005321775A (ja) * 2004-05-01 2005-11-17 Samsung Electronics Co Ltd ディスプレー装置
JP2008051949A (ja) * 2006-08-23 2008-03-06 Fujitsu Hitachi Plasma Display Ltd 階調表示処理方法及びプラズマディスプレイ装置
JP2008083564A (ja) * 2006-09-28 2008-04-10 Fujitsu Hitachi Plasma Display Ltd 多階調表示方法及び装置
WO2009139151A1 (fr) * 2008-05-14 2009-11-19 パナソニック株式会社 Dispositif d’écran plasma et procédé de commande d’écran plasma

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