WO2010015867A1

WO2010015867A1 - Apparatus for generating a three-dimensional view, and a method and 3d-glasses therefor

Info

Publication number: WO2010015867A1
Application number: PCT/HU2009/000069
Authority: WO
Inventors: Dániel RÁTAI
Original assignee: 3D For All Számítástechnikai Fejlesztö Kft.
Priority date: 2008-08-07
Filing date: 2009-07-31
Publication date: 2010-02-11
Also published as: EP2366253A1; HUP0800501A2; HU0800501D0; WO2010015868A1

Abstract

According to a first aspect, the invention relates to an apparatus for generating a three- dimensional view, wherein visual information corresponding to a first perspective and visual information corresponding to a second perspective comprise at least a first and a second spectral component. The apparatus comprises - an image-forming device (10), for alternatingly displaying the first spectral component of the first perspective, the second spectral component of the second perspective, the second spectral component of the first perspective, and the first spectral component of the second perspective, and - a perspective-separating device (11) comprising a first part (11a) separating the displayed spectral components of the first perspective for a first eye and a second part (11 b) separating the displayed spectral components of the second perspective for a second eye, which perspective-separating device (11) is controlled synchronously with the image-forming device (10). According to further aspects, the invention relates to a method and 3D-glasses for the apparatus.

Description

- -

APPARATUS FOR GENERATING A THREE-DIMENSIONAL VIEW, AND A METHOD AND 3D-GLASSES THEREFOR

TECHNICAL FIELD

The present invention relates to an apparatus for generating three- dimensional view, as well as to a method and 3D-glasses necessary therefor, which are based on color-separation theory for generating stereo images, nevertheless, enable production of a three-dimensional view without color-limitation.

BACKGROUND ART

The object of 3D image visualization is to enable the users to sense spatial shapes as reality. Three-dimensional effect may be achieved by conveying separate images to the left and right eyes, in the same way as the eyes sense the spatial shapes from their respective different positions. For generating and sensing this double-image (so-called stereo image), several technologies have so far been developed. In the simplest case, the image is displayed on a conventional monitor for the two eyes simultaneously and the three-dimensional effect can be sensed by means of special glasses. There are, however, sophisticated and extremely expensive monitors as well, which do not require the use of the aforementioned glasses or any other auxiliary device, since the monitor itself provides the three- dimensional view.

One of the simplest and most widely used solutions is provided by the systems based on the separation of images appearing in the same place. These systems are based on the theory that the images for both the right and the left eyes are displayed on one display simultaneously, which two images are then separated by special, so-called 3D-glasses, in a way that through the left lens only the image displayed for the left eye and through the right lens only the image displayed for the right eye is allowed to pass.

It is the essence of all known 3D visualizations based on color-separation theory, that images of different color are generated for the left and the right eye respectively, and the two different color images are separated by colored lenses. For this purpose, red and blue (or cyan, which is the mixture of blue and green) lenses are generally used. Through the red lens only the red light, while through the blue lens only the blue light can pass (anaglyph glasses). It is the advantage of color-separation-type systems, that they are extremely inexpensive, their disadvantage being, however, that 10-15 minute use thereof may already be harmful to the eyes, moreover, that three- dimensional view is not provided thereby without color limitation.

Light-polarization-type systems are essentially based on generating images of different polarity for the left and the right eyes, and the two images of different polarity are separated by polarizing lenses. Contrary to the color separation-type systems, light-polarizing-type systems are capable of reproducing entirely realistic color images. Although the manufacturing costs of such glasses are relatively low, the monitor generating the two-directionally polarized stereo images is relatively expensive, and therefore this solution is primarily used in 3D movie theatres.

Systems using so-called shutter-glasses operate in a manner that the respective images for the left and the right eye are displayed alternatingly, and the shutter-glasses alternatingly block one eye after the other, synchronously with the alternating images. Shutter-glasses have lenses adapted to switch between a blocked state and a transparent state at a high frequency. Similar to the light- polarizing-type system, a shutter-type system is also capable to reproduce entirely realistic color images. Such a system is advantageous due to its relatively low price and to the fact that - unlike in light-polarizing-type systems - a conventional tube monitor is sufficient enough for use as display therein. It is a disadvantage of the shutter-glasses that the left and right eyes are blocked alternatingly, thereby causing flicker of the image seen through the glasses.

Flicker is greatly dependent upon the difference in illumination power between the individual states. In case of alternating black and white states, flicker is significantly more intense in case of the two tones of color of similar illuminating power. Therefore, solutions have been provided, wherein the two states of the glasses are not comprised of a full block and a full transparency, but of two colors that are used by anaglyph glasses as well. The given perspectives are separated for the eyes by means of polarization. In this case, the above two disadvantages of the anaglyph glasses are not encountered, i.e. the generated illusion is limited in color, and the image is sensed in different colors by the two eyes of the user, which would cause harmful health effects on a long term use. The image will have no color limitation, as the two states of the glasses are of complementary colors, that is, the colors unable to pass through in one period will be able to pass through in the next period. The images are seen in the same color by the two eyes. Flicker will also drastically decrease, as the image is not fully blocked at any moment, and the contrast of illumination power between the flicker states decreases to the minimum. By way of example, such solutions are disclosed in patent documents US 4,641 ,178, US 4,995,718, US 5,564,810 and US 5,742,333. These solutions are generally referred to as polarized color multiplexing solutions.

It is the disadvantage of all known art, that extremely sophisticated image generating devices are required therefor, moreover, that they are incapable of displaying three-dimensional view in case of simple everyday displays. A further drawback is that the known solutions do not provide for possible filtering of the ghost image generated by color switching, nor can they be used in case of monitors refreshing images by an image dot sequence. Another known deficiency lies in that 3D solutions are less likely applicable in the case of LCDs or with displays of similar refresh mode, moreover they cause intense flicker.

DESCRIPTION OF THE INVENTION

The object of the present invention is to provide an apparatus and a method for generating a three-dimensional view as well as 3D-glasses therefor, lacking the disadvantages of the prior art and implementable of relatively simple elements at low costs. A further object of the present invention is to provide an apparatus, a method and 3D-glasses implementable of simple elements and at low costs resulting in less flicker and suitable for use in displays refreshing by image dots, for example LCD (e.g. TFT) monitors.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary preferred embodiments of the present invention are described hereunder on the basis of drawings, where

Fig. 1 is schematic view of an apparatus according to the invention,

Fig. 2 is a control time-diagram of the apparatus elements according to the invention,

Fig. 3 is a schematic view of another apparatus according to the invention,

Fig. 4 is a control time-diagram of the elements of the apparatus according to Fig. 3,

Fig. 5 is a schematic view of a third apparatus according to the invention,

Fig. 6 is a control time-diagram of the elements of the apparatus according to Fig. 5,

Fig. 7 is a schematic view of a third apparatus according to the invention comprising passive 3D-glasses,

Fig. 8 is a time-lapse and impact diagram of the total block phase, - A -

Fig. 9 is a block-diagram of a ghost image filter according to the invention, and

Fig. 10 is a block-diagram of a ghost image filter according to another embodiment of the invention.

MODES FOR CARRYING OUT THE INVENTION

It is the idea of the present invention, therefore, to display visual information corresponding to a first perspective and visual information corresponding to a second perspective by means of an apparatus for producing three-dimensional view, where the visual information of the perspectives comprise at least a first and a second spectral component - preferably color-components. The apparatus comprises an image- forming device for alternatingly displaying the first spectral component of the first perspective, the second spectral component of the second perspective, the second spectral component of the first perspective and the first spectral component of the second perspective. In a preferred embodiment, the spectral components are displayed independently, that is, one spectral component of one perspective is displayed only at a time. In order to avoid flicker, the perspectives are preferably displayed in the display sequence alternatingly. Other embodiments also enable alternate display of an image comprising the first spectral component of the first perspective and the second spectral component of the second perspective, and an image comprising the second spectral component of the first perspective and the first spectral component of the second perspective. The aforementioned embodiment, by way of example, is preferably applicable for projectors displaying colors in succession, while the latter is preferably applicable for LCD monitors.

The apparatus according to the present invention has a perspective-separating device comprising a first part separating the displayed spectral components of the first perspective for the first eye and a second part separating the displayed spectral components of the second perspective for the second eye, which perspective- separating device is controlled synchronously with the image-forming device.

Perspective separation may be performed by conventional shutter-glasses, however, polarization separation may be advantageously applied, as well. In this case, the light exiting the image-forming device is polarized, the spectral components for the eyes are separated by the first and second parts of the perspective-separating device by means of polarization, and the perspective-separating device comprises a polarization-rotating device operated synchronously with the image-forming device for separating for the specific eyes. Monitors generate the displayed image by means of three colors. These are the red, the green and the blue. Anaglyph, i.e. color-separation glasses may use any color combination, where the two lenses do not include identical colors. The most widely used anaglyph glasses are the red-cyan. The red lens allows the light of the red pixels of the monitor to pass through, while cyan allows the green and blue pixels. This has three advantages. Namely, the first being, that all three basic colors reach - and hence are perceived by - the eye. The second being, that the two colors are situated in the opposite ends of the spectrum scale of light, thereby enabling more simple and better quality separation of the images than in the case of green and a complementer color thereof. The third benefit is that the difference in illumination power detectable by the human eye is less between the two eyes than in the case of the other, yellow-blue, solution having all the above-described advantages. The solution according to the present invention requires the same basic principles in terms of color choice: i.e. the two colors together should comprise all three basic colors, should provide the best separation of images, and should have between the two colors the lowest possible illumination contrast detectable by the human eye; for the same reasons, the ideal choice of color in respect of the glasses according to the present invention is also red- cyan, which will be applied in the description hereunder as well, nevertheless, the invention is also applicable to other colors, that is, to other spectral components of the visible spectrum.

The apparatus according to the present invention serves to provide a three- dimensional view, where the visual information corresponding to a first perspective and the visual information corresponding to a second perspective comprise at least a first and a second spectral component, preferably red and cyan components.

By means of the image-forming device 10 - preferably an LCD monitor - depicted in Fig. 1, images of the first spectral component of the first perspective and the second spectral component of the second perspective and images of the second spectral component of the first perspective and the first spectral component of the second perspective are displayed alternatingly.

According to the present invention, a perspective-separating device 11 is used comprising a first part 11a separating for the first eye the displayed spectral components of the first perspective - preferably by way of polarization - and a second part 11b separating for the second eye the displayed spectral components of the second perspective - also preferably by way of polarization. Both parts 11a, 11b of the perspective-separating device 10 according to a preferred embodiment of the present invention comprise a first polarizing filter PR effecting the first spectral component, by way of example this is the red (red) polarizing filter, and a second polarizing filter PC affecting the second spectral component, which is preferably the cyan (cyan) polarizing filter. The second polarizing filter PC has a direction of polarization different from that of the first polarizing filter PR according to the drawing, e.g. preferably perpendicular to the direction of polarization thereof. Furthermore, the perspective-separating device 11 comprises a polarization-rotating device 12 operated synchronously with the image-forming device 10, separating the perspectives for the specific eyes and switching the polarization of the light exiting the image-forming device 10 between the directions of polarization of the first and the second polarizing filters PR, PC, alternatingly.

The LCD monitor outputs polarized light. The image on the monitor is thus generated so that when the lens of the left eye is red and the right one is cyan, the red pixels on the monitor display the image intended for the left eye and the green and blue pixels display the image intended for the right eye. When the lenses of the eyes are switched, the same applies in reverse.

By switching the lenses' state in the monitor frequency after each state, every color will reach the eyes, and thereby 3D-glasses without color-limitation will be obtained, having significantly less flicker than in the case of shutter-glasses. Also, the lenses can be inverted less frequently, by way of example every half-a-minute, or minute. In this way, the glasses will have no flicker whatsoever, but will be limited in color similarly to anaglyph glasses, nevertheless, providing less strain on the eyes as the colors are not distorted statically in one direction and the eyes get a chance to regenerate.

The operation of the polarizing filters effecting the individual spectral components (colors) is as follows. Every polarizing filter has a corresponding function, representing its efficiency to polarize light rays of given frequency. In most cases, this efficiency is the highest within the light frequency range detectable by the human eye. The glasses according to the present invention use polarizing filters polarizing not the entire, but only part - preferably the red and cyan light - of the spectrum detectable by the human eye. This polarizing filter, for example, in case of red light polarization, will let the full cyan spectrum through, while only half of the red spectrum can pass through due to the polarization. The light transmission of the theoretically perfect, red-light polarizing filter PR is 100% in the cyan spectrum and 50% in the red spectrum, and has a mildly cyan color on the face of it. In the case of two polarizing filters positioned crosswise, where one of the polarizing filters polarizes the red light and the other one the full visible spectrum, the light transmission in the cyan spectrum will be 50%, while that in the red spectrum will be 0%. The very opposite of this applies to cyan light polarizing filter PC.

In Fig. 1, the first polarizing filter PR in the first part 11a of the perspective- separating device 11 is arranged with a direction of polarization parallel to that of the first polarizing filter PR is arranged in the second part 11b, and the polarization-rotating device 12 operates in a counter-phase mode as depicted in Fig. 2 with regard to the first and second parts 11a, 11b. Indeed, the contrary is also conceivable, where the approppriate polarizing filters are arranged in the parts of the perspective-separating device 11 with directions of polarization perpendicular to one another; in which case the polarization-rotating device 12 operates at an identical phase relative to the two parts 11a, 11b.

According to the present invention, one or more LCD sheets are preferably used as the polarization-rotating device 12. In power-off mode, the LCD sheets rotate the polarization plane by 90°, while in power-on mode, i.e. incidental to electric power, they allow the light to pass through without rotation. By positioning an LCD sheet between two polarizing filters positioned in an appropriate angle an LCD shutter will be obtained, which is capable of blocking or passing through light incidental to electric power. If polarized light of the full visible light spectrum is projected onto an LCD sheet, and red- and cyan-spectrum polarizing filters having directions of polarization perpendicular to one another are arranged on the back side of the sheet, a panel will be obtained which is switchable between red and cyan light incidental to electric power.

The three-dimensional view according to the present invention can be obtained by means of one LCD panel (or by means of one LCD panel per each eye), however, switchings preferably comprise a phase blocking the display for both eyes. For this purpose, light passes through two polarization-rotating elements LCD1 , LCD2, preferably two LCD sheets, in the polarization-rotating device 12. Its advantages will be mentioned in connection with Fig. 8 herebelow.

The polarization-rotating elements LCD1 , LCD2 sandwich the first and second polarizing filters PR, PC as seen in Fig. 1 , and after the second polarization-rotating element LCD2 in the direction of light propagation a further polarizing filter PF effecting both spectral components or preferably the full spectrum, is arranged having identical direction of polarization with that of one of the polarizing filters PR, PC.

A control diagram regarding the apparatus depicted in Fig. 1 is demonstrated in Fig. 2. For the purposes of perspective separation, the polarization-rotating elements LCD1, LCD2 are to be operated in counter-phase due to identical arrangement (polarizing filter orientation) of parts 11a, 11b. In the top zone, the control of the image- forming device 10 (DISPLAY), preferably an LCD monitor, is depicted, wherein REDieft+CYANright and CYAN|_eft+RED_right images are displayed alternatingly; marked in the Fig. by R+C and C+R states. The indicated time period T is the frequency of the monitor.

The intermediate zone depicts the control of the polarization-rotating elements LCD1, LCD2 arranged in part 11a, while the lower zone depicts the control of the polarization-rotating elements LCD1 , LCD2 arranged in part 11b. The sequence represented by part 11a corresponding to the left eye can be seen in the upper zone of part 11a, where R indicates the red images, B indicates the black images and C indicates the cyan images. The sequence represented by part 11b comprises red and cyan images in counter-phase, therefore, by means of the demonstrated control the perspective-separating function is implemented. In this case, the lens may have three states: red, cyan and black.

Another preferred embodiment of the present invention is depicted in Fig. 3, wherein polarization-rotating elements LCD1 , LCD2 sandwich one polarizing filter PR, and the other polarizing filter PC is arranged in the direction of light propagation after the second polarization-rotating element LCD2. Polarization-rotating device in this preferred embodiment is also comprised of two LCD sheets per eye. The control of this preferred embodiment is demonstrated in Fig. 4. In this case, the lens may have four states: red, cyan, black and transparent (this latter is not generated during the operation, but may be practical in power-off state).

Yet a further possible embodiment is drafted in Fig. 5, the control of which is demonstrated in Fig. 6. The advantage of this embodiment is that the first polarization- rotating element LCD1 may also be a so-called pi-cell LCD, having better switch parameters. In this case, the polarization-rotating elements LCD1 , LCD2 are arranged in the direction of the light propagation before the first and second polarizing filters PR, PC, sandwiching a further polarizing filter PF effecting both spectral components and having identical direction of polarization to that of one of the polarizing filters PR, PC. From the embodiments 1, 3, and 5, it is advisable to choose for the purposes of a given application the one, wherein the quality of polarizing filters and LCD panels provide higher standard operation. The advantage of the embodiment depicted in Fig. 1 is its higher separation efficiency, however, during operation the background for the user alternates between red and cyan colors. The embodiment according to Fig. 3 has weaker separation, but a static background. The embodiment according to Fig. 5 is similar to the embodiment depicted in Fig. 1 , however, with the difference that the total block phase is switched by the polarization-rotating element LCD1 - which can also be a rapid pi-cell LCD - and the polarization-rotating element LCD2 has more time to switch during the total block phase. The embodiment depicted in Fig. 1 does not require such a high switch speed as in the case of polarization-rotating element LCD1 of the embodiment according to Fig. 5. The decision between the embodiments in a given application is based on the efficiency of separation, possible compensation of incomplete separation, external light conditions of the application, and switch speed of the LCD sheets.

In the embodiments depicted in Figs. 1 , 3 and 5, therefore, the image-forming device 10 is an LCD monitor emitting by itself polarized light, and the perspective- separating device 1 is arranged in the form of active 3D-glasses. In case of using non- polarizing monitors for implementation of the system, the monitor is to be equipped with polarizing filter or a separate polarizing filter is to be placed in front of the lenses.

It is a significant aspect of a preferred embodiment of the present invention therefore, that it comprises a polarization-rotating device 12, which receives polarized light from the image-forming device 10 and alternatingly switches the polarization thereof. In other words, this means that the external polarizing filter has been removed from the polarization-type active 3D-glasses according to the prior art and has been repositioned onto the display (in case of LCD monitors this is already a given fact). In this way, during the operation of the active 3D-glasses, there are image transitions on the display only, while the background is stable (possibly alternatingly switching between red-cyan colors). In this way, the sense of flicker significantly decreases.

The 3D-glasses without external front polarizing filter are applicable as passive glasses as well; in which solution the left and right parts of the glasses are to be brought into opposite states. This is particularly advisable when the glasses are intended for universal, i.e. active and passive use as well. On the contrary, the polarization-rotating device 12 may be arranged in a way shown in Fig. 7 at the image-forming device 10 - by way of example at the projector - in which case the first and second parts 11a, 11b of the perspective separator device 11 may be arranged in the form of passive 3D-glasses.

By means of colored polarizing filters, therefore, passive glasses can be obtained. For this purpose, a monitor capable of alternating the directions of polarization is to be generated. In case of linear polarizing filter, the two polarized states of the monitor are perpendicular to one another. In both lenses of the passive glasses, red and cyan polarizing filters PR, PC are arranged perpendicular to one another, and the left lens is perpendicular to the right lens, thus the red polarizing filter PR of the left lens is parallel to the cyan polarizing filter PC of the right lens. In this arrangement, in one polarization state of the monitor the left lens is cyan and the right one is red, while in the other polarization state of the monitor the left lens is red and the right lens is cyan.

Such a monitor can be created by way of projection, which practically requires an LCD sheet to be put in front of a DLP projector. If the image is produced by means of a projector 13 in accordance with the above described mode, and the LCD panel is controlled synchronously with the projector 13, and an umbrella 14 maintaining polarization is used, the desired display will be created. By means of this solution, a simple 85 Hz DLP projector can produce image quality similar to that of the most professional projectors designed especially for 3D.

The invention is applicable in case of LCD projectors as well. With LCD projectors, the total block phase may also be required. In this case, another LCD sheet as well as another polarizing filter may be placed in front of the projector and the original LCD sheet. This additional LCD sheet may block the projector image incidental to electric power, thereby achieving the total block phase. In this case, the glasses may have three states: left is red, right is cyan; left is cyan, right is red; left is black, right is black.

In case the use of passive glasses is desired, but without projector display, or with projector, projecting the image onto depolarization canvas from the back, then an LCD sheet covering the entire display may be used for producing image polarizing in alternate directions. In this case, it is also possible, that one or two LCD sheets are used depending on whether total block phase is required. In case of DLP projectors, the present invention may be used according to another preferred embodiment. The spectral components in the embodiments mentioned so far were made up of the red and cyan color components of the visual information, and during the display of one image, the spectral components were displayed simultaneously. In case of DLP projectors, the image is displayed so that in one image-display period the colors, i.e. the spectral components R, G, B, are displayed in succession. First, a red, then a green and in the end a blue color image is displayed, nevertheless, due to the high frequency our eyes sense them simultaneously. It is the essence of this embodiment of the invention, that shutter- glasses or glasses according to other, aforementioned invention, the states of the glasses are switched several times within one image display period. By way of example, it is advantageous if the states of the glasses are switched three times within one image-display period. In such a case, flicker drastically decreases, since frequency is increased threefold, and every color of the image will reach the eyes within two display periods indeed. In this case, the image is to be generated for the left and the right eye, and then sent to the projector in such a way that the different color components of the colored image should display different perspectives according to the states of the glasses. Operation of the embodiment is demonstrated in Table 1.

Table 1 If, for example, the shutter is a lower frequency one, it may also be advantageous if the states of the glasses are switched with every second color-change. This is demonstrated in Table 2.

Table 2

A DLP projector system can be implemented by means of active or passive glasses as well. In an active case, conventional shutter-glasses may be applied, or any other arrangement already described above having the front polarizing filter arranged on the image-forming device. In a passive case, conventional polarizing filter glasses may be applied as well. In such a case, an active polarizing filter is to be placed in front of the projector alternatingly switching the directions of polarization. By way of example, this could be an LCD panel or a mechanic device equipped with polarizing filter.

Red-cyan color combination is not advantageously used together with DLP projector - in case of control by conventional shutter-glasses - as it merely results in offsetting the flicker by one-third of a period, however, flicker remaining the same. This is demonstrated in Table 3 below.

Table 3

In addition to the above-described solutions for reducing flicker, offsetting the control of the glasses according to Table 4 would provide a further solution.

Table 4

Yet another solution for color filtering, would be provided by the use of other colors according to Table 5 below.

Table 5

Linear and circular polarizing filters can be used in case of passive as well as active 3D-glasses. With regard to active glasses it is to be considered, however, that LCD monitors emit linearly polarized light. In circularly polarized passive glasses, red and cyan polarizing filters polarized in opposite directions are to be placed in the left and right lenses in a way that the red polarizing filter of the left lens is to polarize parallel to the direction of the cyan polarizing filter of the right lens, and the cyan polarizing filter of the left lens is to polarize in the same direction with that of the red polarizing filter of the right lens.

LCD monitors operate at a lower refresh frequency than CRT monitors, therefore, more flicker may be sensed by the use of 3D-glasses. In addition, further flicker is caused in the known art by the fact that 3D-glasses generally flicker the entire field of vision, including areas outside the display area as well. A significant aspect of the present invention lies in the fact that disturbing effects of flicker are reduced in such a way that 3D-glasses cause image switching on the image-forming device 10, i.e. preferably on the LCD monitor only, whilst the other areas of the field of vision remain static. This can be achieved essentially by repositioning the polarizing filter from the side of the 3D-glasses of the known art - in which both sides of the LCD sheet are arranged with polarizing filter - facing the image-forming device 10 to the image- forming device 10 itself (LCD monitors with polarized light emission do not require this polarizing filter). This preferred arrangement is characteristic of each and every embodiments of the present invention and has proved extremely beneficial in practical use.

Inserting the aforementioned total block phase in the operating sequence in between the image frame transitions is advantageous when the two images are seen together for a while in the course of image refresh. By way of example, in the case of LCD monitors refresh is made per image dots, that is, the image dots of the previous image are transposed by the new image dots. Therefore, on LCD monitors some image is always visible on the screen of the display.

As a result, by using conventional shutter-glasses and synchron control together with an LCD monitor, it will cause good image in the upper part of the monitor, i.e. the left eye will see the image intended for the left eye and the right eye will see the image intended for the right eye, while towards the lower part of the monitor will gradually become transposed, and adequate stereo image is seen in the uppermost few lines of the monitor only. The control electronics according to the present invention therefore, not only performs the change of the states of the left and right eyes, but also applies a total block phase as demonstrated in Figs. 2, 4, 6 and 8, wherein both eyes are blocked. While the display - or most of it - is being refreshed on the monitor, the control of the 3D-glasses 25 turns the total block on, thereby the area in which the user does not see a stereo image may be reduced to a few lines of the display. By offsetting the synchronization pace, these few lines can be distributed along the display top and bottom.

In case of color multiplexing, the total block phase can be achieved by applying an additional LCD panel per eye and by appropriate control thereof, as described above.

The first row of Fig. 8 shows the cycle wherein the left eye is red (R) and the right eye is cyan (C). The 3D-glasses 25 are in R+C state in the phase between the first two monitor-representations, then after the next image begins to refresh in the essential mid-range part of the monitor, the 3D-glasses 25 switch to the total block phase. This way, the view as seen in the right-hand side of the figure is provided for the user, wherein stereo image is visible in the essential part of the image, and only in the less frequently used top and bottom parts is the reverse stereo image displayed. The last row of the figure demonstrates the results of the next cycle and block.

The total block phase also comprises a part of the present invention, and can be used not only in polarization color-multiplexing solutions, but also in systems comprising other similar problems, e.g. with simple shutter-glasses or with shutter- glasses without front polarizing filter as described above.

According to the present invention a dynamic total block phase control may also be implemented. By increasing the total block phase, the area having good stereo image quality will increase, however, the visible illumination power will decrease. Together with the reduced visible illumination power, flicker will also decrease. There is indeed always an optimal total block rate. It is therefore advisable to apply a software control relative to this rate. By way of example, if on the whole a lighter image is displayed on the display, which would cause more flicker, and would be visible if darker as well, then e.g. the rate of total block could be increased in order to find an optimal solution compromising the new situation. As the illumination power of the monitor cannot be controlled by software or in a very complex way only, the above dynamic control may provide an efficient solution to this problem as well. Another setting option may be that of the position of the total block phase. In a basic case, blocking is performed during the refresh of the mid-range image lines of the LCD screen. Blocking may also be performed while the image lines determined on the LCD screen on the basis of the displayed visual information are being refreshed. In this case, if - for any reason - it is more important to have good spatial view in the upmost part of the display than in the bottom, the total block phase can be offset towards the top of the monitor.

A significant aspect of the present invention is therefore the 3D-glasses for the image-forming device 10 displaying visual information corresponding to a first perspective and visual information corresponding to a second perspective alternatingly in time, the operation of which image-forming device 10 comprises such image refresh period wherein visual information corresponding to both perspectives is at least partially visible, and the 3D-glasses are arranged so as to block the view at least in a part of the image refresh period. A general deficiency of the known 3D-glasses is related to the fact that separation of the two images for the two eyes is imperfect, that is, the image intended for the right eye can be seen to a certain degree by the left eye and vica versa (ghost image). As a result thereof beginner users often do not sense the 3D effect and even with advance users the distance, in which virtual objects emerge from the plane of the monitor, in a way that it is perceived by the user in space, decreases. The more ghosting there is in the image, the worse of a quality the view becomes, and the less likely the brain will be "deceivable", that is, the more likely it will see the shape in the plane of the display. The ghost image filter according to the present invention hinders the image intended for the right eye to migrate into the left eye, or the contrary, thereby 3D effect is more easily generated and more definite spatial contrast may be perceived.

The rate of ghosting depends on the quality of 3D display system and the operating theory thereof. By means of decreasing or eliminating ghosting will not only provide better image quality but also will enable the use of less expensive, lower quality 3D display for a given task.

The ghost image filter according to the present invention operates in such a way that it combines the image generated for one eye with a reduced intensity negative (inverse) of the image generated for the other eye, displaying it as such. Accordingly to the images intended for one eye a reduced intensity replica of the inverse image of the other eye is added. The intensity of the inverse image component shall be set so as to completely compensate the appearing ghost image.

Fig. 9 demonstrates a block diagram of the exemplary ghost image filter 20 for interleaved 3D. The ghost image filter 20 is arranged so as to be interposed between the computer and the monitor, nevertheless the ghost image filter function may be arranged on e.g. the video card as well, moreover, such images may be generated by the software itself.

The received and transmitted vertical synchron signals are indicated by VSI_N and VS_0UT signals, while the horizontal synchron signals are indicted by HS|_N and HS_0UT signals. The RGB signals arriving at the ghost image filter 20 will reach the monitor via a switch unit 21. The incoming R|_N, G_!N and B|_N signals will also be led into an inverter unit 22 generating the inverse of the RGB - by an intensity adjustable by potentiometers 23 - which will be led to the switch unit 21 as well. The ghost image filter 20 is advantageously operational in an interleaved display mode, wherein even and odd lines are controllable separately. In this case, the visual information corresponding to one perspective will preferably be displayed in the even lines, while the visual information corresponding to the other perspective will be displayed in the odd lines by means of the image-forming device 10, and with the help of the ghost image filter 20 the reduced intensity inverse image of the other perspective will be displayed in the image lines of the other perspective simultaneously with the display of the one perspective. Such display of the lines is implemented by the switch unit 21 , which is controlled by horizontal synchron signals.

The active 3D-glasses 25 are preferably controlled by the glasses-control-unit 24 being a part of the ghost filter 20, issuing the CSL control signal relative to the left eye as well as the CSR control signal relative to the right eye on the basis of the horizontal synchron signal. The glasses-control unit 24 may also derive the control from the horizontal synchron signal, which option is indicated by an intermittent line.

The intensity of ghost image filtering is controlled by potentiometers 23. By fine overtuning of the filter, extra three-dimensional effect can be obtained. In the case of LCD monitors, the degree of ghost image filtering is preferably set higher in the top and bottom areas of the display.

Fig. 10 is a block diagram of another preferred embodiment of the ghost image filter. This embodiment is advantageous relative to the above-described color multiplexing 3D-glasses (Figs. 1 , 3 and 5). The additional potentiometers 26 comprised by the embodiment are optional; thereby possible color distortions of the color 3D- glasses can be compensated. In case of color multiplexing solutions, color blocking may possibly effect the various colors differently in the course of color blocking. In case of DLP projectors, color distortion may comprise a problem as well. Theoretically, color corrigation may be achieved by tuning the various setting options of the image-forming device, however, it may also effect the ghost-filtered image, as well as both the eyes. It is advisable, therefore, to arrange a modulating option on the control electronics.

In a given case, the characteristics of the ghost image filter may also be tuned. In ghost image filtering in a basic case the inverse image is generated linearly; certain cases however may require - instead of generating a linear inverse of the original image - that certain pixels of the inverse image be given some weight in view of illumination power. The relevant characteristic curve mainly depends on the parameters of the given display. In the various areas of the display (depending upon the total block phase), the ideal curve may also vary. The desired characteristics may also differ with regard to the various colors, moreover, in an extreme case it may also be possible that e.g. the left eye is ghosting more than the right eye, in which case the respective ideal curve may be different in respect of the two eyes. The curve may be tuned by means of a software or hardware as well.

The ghost image filter can be advantageously calibrated so that both eyes are connected to one eye (e.g. the left lens receives the signal of the right lens as well), then tuning of the ghost image filter is completed in regard to a test image as long as the image does not disappear.

Ghost image filtering is preferably implemented in a way that it is set for the various colors independently, and tuned for the two eyes separately.

Ghost image filtering also comprises a part of the present invention, not only in respect of polarizing color-multiplexing solutions, but also applicable in respect of any other systems providing three-dimensional view. With regard to the apparatus and 3D- glasses comprising part of the present invention, implementation of ghost image filtering is of extreme importance since the rotation of the polarization may be incomplete, thereby easily generating ghost image.

Furthermore, the present invention is also applicable in connection with not only 3D display, but also relative to any system, where different visual information are to be displayed for the two eyes or - in a given case - for the eyes of several users.

The invention is not limited to the exemplary embodiments described herein, but shall also include any possible further variations within the scope of the claims.

Claims

1. An apparatus for generating a three-dimensional view, wherein visual information corresponding to a first perspective and visual information corresponding to a second perspective comprise at least a first and a second spectral components, c h a r a c t e r i z e d in that the apparatus comprises

- an image-forming device (10), for alternatingly displaying the first spectral component of the first perspective, the second spectral component of the second perspective, the second spectral component of the first perspective, and the first spectral component of the second perspective, as well as

- perspective-separating device (11) comprising a first part (11a) separating the displayed spectral components of the first perspective for a first eye and a second part (11b) separating the displayed spectral components of the second perspective for a second eye, the perspective-separating device (11) being controlled synchronously with the image-forming device (10).

2. The apparatus according to claim 1 , characterized in that the light exiting the image- forming device (10) is polarized, the first and second parts (11a), (11b) of the perspective-separating device (11) separate the spectral components for the eyes by way of polarization, and the perspective-separating device (11) comprises a polarization-rotating device (12) operated in synchron with the image-forming device (10) for separating the perspectives for the given eyes.

3. The apparatus according to claim 1 or claim 2, characterized in that one of the spectral components of one perspective is displayed only at a time, the perspectives alternating within a display sequence per each display.

4. The apparatus according to claim 3, characterized in that the image-forming device (10) comprises a unit, preferably a DLP projector, displaying the R, G and B basic colors in succession, wherein the spectral components are the basic color components of the visual information.

5. The apparatus according to claim 1 , characterized in that the perspective-separating device (11) is formed as shutter-glasses (25) blocking the eyes alternatingly.

6. The apparatus according to claim 2, characterized in that the image-forming device (10) comprises a static polarizing filter, and the perspective-separating device (11) is formed as active 3D-glasses comprising the polarization-rotating device (12).

7. The apparatus according to claim 2, characterized in that the polarization-rotating device (12) is arranged at the image-forming device (10), and the first and second parts (11a, 11b) of the perspective-separating device (11) are formed as passive 3D- glasses (25).

8. The apparatus according to claim 2, characterized in that

- it comprises an image-forming device (10) for alternatingly displaying an image comprising the first spectral component of the first perspective and the second spectral component of the second perspective, as well as an image comprising the second spectral component of the first perspective and the first spectral component of the second perspective, and the perspective-separating device (11) comprises

- in both parts (11a, 11b) a first polarizing filter (PR) effecting the first spectral component and a second polarizing filter (PC) effecting the second spectral component, which second polarizing filter (PC) has a direction of polarization different from that of the first polarizing filter (PR), wherein the polarization-rotating device (12) alternatingly switches the polarization of the light exiting the image-forming device (10) between the directions of polarization of the first and second polarizing filters (PR, PC).

9. The apparatus according to claim 8, characterized in that

- the direction of polarization of the first and second polarizing filters are perpendicular to one another,

- the first polarizing filter (PR) is arranged in the second part (11b) of the perspective- separating device (11) in a way that its direction of polarization is parallel to that of the first polarizing filter (PR) arranged in the first part (11a), and

- the polarization-rotating device (12) operates in counter-phase with regard to the two parts (11a, 11b).

10. The apparatus according to claim 8, characterized in that - the direction of polarization of the first and second polarizing filters PR, PC are perpendicular to one another,

- the first polarizing filter (PR) is arranged in the second part (11b) of the perspective- separating device (11) in a way that its direction of polarization is perpendicular to that of the first polarizing filter (PR) arranged in the first part (11a), and

- the polarization-rotating device (12) operates in the same phase with regard to the two parts (11a, 11b).

11. The apparatus according to claim 9 or claim 10, characterized in that the switchings comprise a phase which blocks the display for both eyes, and in the polarization- rotating device (12) the light passes through two polarization-rotating elements (LCD1 , LCD2), preferably two LCD sheets.

12. The apparatus according to claim 11, characterized in that the polarization-rotating elements (LCD1 , LCD2) sandwich the first and second polarizing filters (PR PC), and an additional polarizing filter (PF) - effecting both spectral components - is arranged in the direction of light propagation after the second polarization-rotating element (LCD2), and has the same direction of polarization as that of one of the polarizing filters (PR, PC)

13. The apparatus according to claim 11, characterized in that the polarization-rotating elements (LCD1 , LCD2) sandwich one polarizing filter (PR), and the other polarizing filter (PC) is arranged in the direction of light propagation after the second polarization- rotating element (LCD2).

14. The apparatus according to claim 11, characterized in that the polarization-rotating elements (LCD1 , LCD2) are arranged in the direction of light propagation before the first and second polarizing filters (PR, PC), and sandwich an additional polarizing filter (PF) - effecting both spectral components - having the same direction of polarization as that of one of the polarizing filters (PR, PC).

15. 3D-glasses for an image-forming device (10) alternatingly displaying an image comprising a first spectral component of a first perspective and a second spectral component of a second perspective, as well as an image comprising a second spectral component of the first perspective and a first spectral component of the second perspective, which image-forming device (10) outputs polarized light, the 3D-glasses (25) comprising a first part (11a) separating the displayed spectral components of the first perspective for the first eye by way of polarization and a second part (11b) separating the displayed spectral components of the second perspective for the second eye by way of polarization, c h a r a c t e r i z e d in that

- it comprises in both parts (11a, 11b) a first polarizing filter (PR) effecting the first spectral component and a second polarizing filter (PC) effecting the second spectral component, which second polarizing filter (PC) has a direction of polarization different from that of the first polarizing filter (PR), and

- a polarization-rotating device (12) is used, which is operated in synchron with the image-forming device (10) for separating the perspectives for the given eyes by alternatingly switching the polarization of the light exiting the image-forming device (10) between the directions of polarization of the first and second polarizing filters (PR, PC)

16. The 3D-glasses according to claim 15, characterized in that

- the directions of polarization of the first and second polarizing filters (PR, PC) are perpendicular to one another,

- the first polarizing filter (PR) is arranged in the second part (11b) with a direction of polarization being parallel to that of the first polarizing filter (PR) arranged in its first part (11a), and

- the polarization-rotating device (12) is operational in counter-phase with regard to the two parts (11a, 11b)

17. The 3D-glasses according to claim 15, characterized in that

- the first polarizing filter (PR) is arranged in the second part (11b) with a direction of polarization being perpendicular to that of the first polarizing filter (PR) arranged in its first part (11a), and

- the polarization-rotating device (12) is operating in the same phase with regard to the two parts (11a, 11b)

18. The 3D-glasses according to claim 16 or claim 17, characterized in that the switchings comprise a phase which blocks the display for both eyes, and wherein the polarization-rotating device (10) is a part of the 3D-glasses and comprises two polarization-rotating elements (LCD1, LCD2), preferably two LCD sheets.

19. The 3D-glasses according to claim 18, characterized in that the polarization- rotating elements (LCD1 , LCD2) sandwich the first and second polarizing filters (PR PC) and an additional polarizing filter (PF) - effecting both spectral components - is arranged in the direction of light propagation after the second polarization-rotating element (LCD2) having the same direction of polarization as that of one of the polarizing filters (PR, PC).

20. The 3D-glasses according to claim 18, characterized in that the polarization- rotating elements (LCD1 , LCD2) sandwich one polarizing filter (PR) and the other polarizing filter (PC) is arranged in the direction of light propagation after the second polarization-rotating element (LCD2).

21. The 3D-glasses according to claim 18, characterized in that the polarization- rotating elements (LCD1 , LCD2) are arranged in the direction of light propagation before the first and second polarizing filters (PR, PC) and are sandwiching an additional polarizing filter (PF) - effecting both spectral components - having the same direction of polarization as that of one of the polarizing filters (PR, PC).

22. The 3D-glasses according to claim 15, characterized in that the spectral components are the red and cyan (blue + green) components of the visual information.

23. A method for generating a three-dimensional view, wherein visual information corresponding to a first perspective and visual information corresponding to a second perspective comprise at least a first and a second spectral component, c h a r a c t e r i z e d in that in the course of the method

- the first spectral component of the first perspective, the second spectral component of the second perspective, the second spectral component of the first perspective, and the first spectral component of the second perspective are displayed altematingly, and - the displayed spectral components of the first perspective is separated for a first eye and the displayed spectral components of the second perspective are separated for a second eye.

24. The method according to claim 23, characterized in that the spectral components are displayed by means of polarized light, and the spectral components for the eyes are separated by way of polarization so that the polarization of the displayed light is switched between two directions of polarization synchronously with the displaying.

25. The method according to claim 23 or 24, characterized in that one spectral component of one perspective is displayed only at a time, the perspectives alternating within a display sequence per each display.

26. The method according to claim 25, characterized in that a unit, preferably a DLP projector, displaying the R, G and B basic colors in succession is used, wherein the spectral components are the basic color components of the visual information.

27. The method according to claim 24, characterized in that

- an image comprising a first spectral component of a first perspective and a second spectral component of a second perspective, as well as an image comprising a second spectral component of the first perspective and a first spectral component of the second perspective are displayed alternatingly,

- a first polarizing filter (PR) effecting the first spectral component and a second polarizing filter (PC) effecting the second spectral component are applied to both eyes, which second polarizing filter (PC) has a direction of polarization different from that of the second polarizing filter (PR), wherein the polarization of the displayed light is switched alternatingly between the directions of polarization of the first and second polarizing filters (PR₁ PC)

28. The method according to claim 27, characterized in that

- the directions of polarization of the first and second polarizing filters (PR, PC) belonging to the same eye are perpendicular to one another, - the first polarizing filter (PR) belonging to one eye is arranged with a direction of polarization being parallel to that of the first polarizing filter (PR) belonging to the other eye, and

- switching is operational in counter-phase with regard to the two eyes.

29. The method according to claim 27, characterized in that

- the directions of polarization of the first and second polarizing filters (PR, PC) belonging to the same eye are perpendicular to one another,

- the first polarizing filter (PR) belonging to one eye is arranged with its direction of polarization being perpendicular to that of the first polarizing filter (PR) belonging to the other eye, and

- switching is operational in the same phase with regard to the two eyes.

30. The method according to claims 28 or 29, characterized in that a phase is included into the switchings, which blocks the display for both eyes.

31. The method according to claim 27, characterized in that the spectral components are the red and cyan components of the visual information.