JP2017053960A - Liquid crystal driving device, image display device, and liquid crystal driving program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction in image quality due to disclination.SOLUTION: A liquid crystal driving device 303 creates first output frame image data and first low gray-level frame image data with respect to first input frame image data, out of input frame image data to be input thereto in a row, creates second output frame image data and second low gray-level frame image data with respect to second input frame image data, and sequentially controls application of first and second voltages to pixels of a liquid crystal element in each of a plurality of sub frame periods in one frame period, on the basis of the frame image data, so as to cause the pixels to form gray levels. When pieces of pixel data located at pixel positions corresponding to each other in the first and second input frame image data have the same gray level, pieces of pixel data located at pixel positions corresponding to each other in the first and second output frame image data have different gray levels. The difference in gray level is 20% or less of the higher gray level.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a liquid crystal driving device that drives a liquid crystal element by a digital driving method.

  Liquid crystal elements include transmissive liquid crystal elements such as TN (Twisted Nematic) elements and reflective liquid crystal elements such as VAN (Vertical Alignment Nematic) elements. The driving method of these liquid crystal elements includes an analog driving method in which brightness is controlled by changing a voltage applied to the liquid crystal layer according to the gradation, and voltage application by binarizing the voltage applied to the liquid crystal layer. There is a digital drive system that controls brightness by changing time. In this digital driving method, one frame period is divided into a plurality of subframe periods on the time axis, and a predetermined voltage is applied (on) and non-applied (off) to the pixel for each subframe, thereby controlling the pixel. There is a sub-frame driving method for displaying gradation.

  Here, a general subframe driving method will be described. FIG. 15 shows an example in which one frame period is divided into a plurality of subframe periods (bit length). The numerical value described on each subframe indicates a time weight within one frame period of the subframe. Here, as an example, a case where 64 gradations are expressed is shown. In the description here, the period of time weight 1 + 2 + 4 + 8 + 16 is referred to as an A subframe period, and the subframe period of time weight 32 is referred to as a B subframe period. Further, the subframe period in which the predetermined voltage is turned on is referred to as an on period, and the subframe period in which the predetermined voltage is turned off is referred to as an off period.

  FIG. 16 shows all gradation data corresponding to the subframe division example shown in FIG. The vertical axis represents gradation and the horizontal axis represents one frame period. In the drawing, the white subframe period indicates an on period in which the pixels are in a white display state, and the black subframe period indicates an off period in which the pixels are in a black display state. According to the gradation data, two gradations (hereinafter referred to as adjacent gradations) adjacent to two adjacent pixels (hereinafter referred to as adjacent pixels) on the liquid crystal element, for example, 32 gradations and 33 gradations are displayed. In this case, the A subframe period is an on period for 32 gradations and an off period for 33 gradations. The B subframe period is an off period for 32 gradations and an on period for 33 gradations.

  In this way, when an on-period and an off-period overlap in time in an adjacent pixel, that is, when a predetermined voltage is applied to one of the adjacent pixels and not applied to the other in the same period, so-called disclination occurs. Occurring and the brightness of the pixels on the on-period side decreases. FIG. 17 shows an image of brightness reduction due to disclination. The vertical direction indicates the gradation, and the shading indicates the brightness of the display. When there is no disclination, smooth shading is expressed, but in adjacent gradations (32 gradations and 33 gradations in this case) where the on period and the off period overlap in adjacent pixels, due to the influence of disclination The brightness decreases and dark lines appear.

  Patent Document 1 discloses a drive circuit that generates a plurality of divided subframe periods by dividing one or a plurality of long subframe periods into a period equal to a period of a short subframe. Further, in the driving circuit of Patent Document 1, when the phase of each bit of the gradation data corresponding to the adjacent pixel is different, the gradation is maintained and the bit array of the gradation data corresponding to one pixel is maintained. On the other hand, correction is performed so as to approach the bit array of gradation data corresponding to the other pixel. As a result, compared to a case where a long subframe period is not divided, a subframe period in which an ON period and an OFF period overlap in adjacent pixels (hereinafter referred to as an ON / OFF adjacent period) can be shortened.

JP2013-050681A

  However, in the method disclosed in Patent Document 1, since the shortest time of the on / off adjacent period in the adjacent pixel is long, a decrease in brightness due to disclination cannot be ignored. Moreover, since the ON / OFF adjacent period in the adjacent pixel is long, the amount of decrease in brightness due to disclination increases according to the response speed of the liquid crystal molecules.

  FIG. 18 shows all gradation data disclosed in Patent Document 1. The A subframe period corresponds to a time weight of 1 + 2 + 4 + 8, and the B subframe period is divided into a plurality of divided subframe periods 1SF (SF is a subframe) to 10SF corresponding to a time weight of 8, respectively. One divided subframe period is 0.69 ms. In this gradation data, the shortest time of the on / off adjacent period in the adjacent pixel is 1.39 ms corresponding to two divided subframe periods. Therefore, a decrease in brightness (that is, a dark line) due to disclination is conspicuous.

  The present invention provides a liquid crystal driving device and an image display device using the liquid crystal driving device, which can reduce the deterioration of image quality such as dark lines due to disclination.

  A liquid crystal driving device according to one aspect of the present invention drives a liquid crystal element. The apparatus generates first output frame image data for first input frame image data out of continuously input frame image data, and has a gradation higher than that of the first output frame image data. 1st low gradation frame image data is generated, second output frame image data is generated for the second input frame image data, and the gradation is lower than that of the second output frame image data. Data generating means for generating second low gradation frame image data, first output frame image data, first low gradation frame image data, second output frame image data, and second low gradation frame Based on each of the image data, the first voltage indication for the pixels of the liquid crystal element in each of a plurality of subframe periods included in one frame period. When having a driving means for forming a gradation to the pixel by controlling the application of less than the first voltage second voltage. Then, when the pixel data at the corresponding pixel positions in the first and second input frame image data have the same gradation, the pixel data at the corresponding pixel positions in the first and second output frame image data The gradations are different from each other, and the difference between the gradations is 20% or less of the higher gradation of these gradations.

  Note that an image display device having the liquid crystal driving device and the liquid crystal element also constitutes another aspect of the present invention.

  A liquid crystal drive program according to another aspect of the present invention is a computer program that causes a computer to drive a liquid crystal element based on an input image. The program causes a computer to generate first output frame image data for first input frame image data out of continuously input frame image data, and from the first output frame image data. The first low-gradation frame image data having a lower gradation is generated, the second output frame image data is generated for the second input frame image data, and the second output frame image data is higher than the second output frame image data. Second low gradation frame image data having a low tone is generated. Further, the computer sequentially transmits one frame based on each of the first output frame image data, the first low gradation frame image data, the second output frame image data, and the second low gradation frame image data. By controlling the application of the first voltage to the pixel of the liquid crystal element and the application of the second voltage lower than the first voltage in each of the plurality of subframe periods included in the period, gradation is formed in the pixel. Then, when the pixel data at the corresponding pixel positions in the first and second input frame image data have the same gradation, the pixel data at the corresponding pixel positions in the first and second output frame image data The gradations are different from each other, and the difference between the gradations is 20% or less of the higher gradation of these gradations.

  According to the present invention, it is possible to reduce the degradation of image quality due to disclination by shifting the occurrence position of disclination when driving the liquid crystal element based on each of the first and second output frame image data. Can do. In addition, the visibility of the moving image can be improved by inserting driving of the liquid crystal element by the first and second low gradation frame image data.

1 is a diagram illustrating an optical configuration of a liquid crystal projector that is Embodiment 1 of the present invention. FIG. FIG. 3 is a cross-sectional view of a liquid crystal element used in the projector according to the embodiment. The figure which shows the some sub-frame period in 1 frame period in an Example. The figure which shows the gradation data of the A sub-frame period in an Example. The figure which shows all the gradation data in an Example. The figure which shows the pixel line in an Example. The figure which shows the response characteristic of the liquid crystal when switching from the all-white display to a monochrome display in an Example. The figure which shows the response characteristic of the brightness when switching from the all-white display in the Example to a monochrome display. The figure which shows the response characteristic of the liquid crystal when switching from the all-black display in the Example to a monochrome display. The figure showing the response characteristic of the brightness at the time of switching from black to black and white display in the embodiment The block diagram which shows the structure of the liquid crystal driver in an Example. The figure which shows the 1st and 2nd output frame image data and all black frame image data in an Example. The figure which shows the frame image displayed sequentially on a liquid crystal element in an Example. FIG. 4 is another diagram showing frame images sequentially displayed on the liquid crystal elements in the embodiment. The figure which shows the several sub-frame period in 1 frame period in the past. The figure which shows the conventional all gradation data. The figure which shows the disclination at the time of driving a liquid crystal element according to the gradation data of FIG. The figure which shows all the gradation data of patent document 1. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an optical configuration of a liquid crystal projector as an image display apparatus that is Embodiment 1 of the present invention. In this embodiment, a projector will be described as an example of an image display device using a liquid crystal element. However, the image display device includes an image display device using a liquid crystal element other than the projector, such as a direct-view monitor.

  The liquid crystal driver 303 corresponds to a liquid crystal driving device. The liquid crystal driver 303 includes a video input unit (image acquisition unit) 303a that acquires an input video signal (input image) from an external device (not shown), and a floor that will be described later according to the gradation (input gradation) of the input video signal. And a driving circuit unit (driving unit) 303b that generates a pixel driving signal corresponding to the tone data. The pixel drive signal is generated for each color of red, green, and blue, and the pixel drive signal for each color is input to the red liquid crystal element 3R, the green liquid crystal element 3G, and the blue liquid crystal element 3B. As a result, the red liquid crystal element 3R, the green liquid crystal element 3G, and the blue liquid crystal element 3B are driven independently of each other. The red liquid crystal element 3R, the green liquid crystal element 3G, and the blue liquid crystal element 3B are vertical alignment mode reflective liquid crystal elements.

  The illumination optical system 301 causes white light from a light source (discharge lamp or the like) to enter the dichroic mirror 305 with the polarization direction aligned. The dichroic mirror 305 reflects magenta light and transmits green light. The magenta light reflected by the dichroic mirror 305 is incident on the blue cross color polarizer 311, where half-wave retardation is given only to the blue light, thereby generating blue light and red light whose polarization directions are orthogonal to each other. . Blue light and red light enter the polarization beam splitter 310, and the blue light passes through the polarization separation film of the polarization beam splitter 310 and is guided to the blue liquid crystal element 3B. The red color component is reflected by the polarization separation film and guided to the red liquid crystal element 3R.

  On the other hand, the green light transmitted through the dichroic mirror 305 passes through the dummy glass 306 for correcting the optical path length, enters the polarization beam splitter 307, is reflected by the polarization separation film, and is guided to the green liquid crystal element 3G. .

  Each liquid crystal element (3R, 3G, 3B) modulates and reflects incident light according to the modulation state of each pixel. The red light modulated by the red liquid crystal element 3R passes through the polarization separation film of the polarization beam splitter 310 and enters the red cross color polarizer 312 where half-wave retardation is given. Then, the red light enters the polarization beam splitter 308, is reflected by the polarization separation film, and travels toward the projection optical system 304.

  The blue light modulated by the blue liquid crystal element 3B is reflected by the polarization separation film of the polarization beam splitter 310, passes through the red cross color polarizer 312 as it is, and enters the polarization beam splitter 308 to enter the polarization separation film. Is reflected toward the projection optical system 304. The green light modulated by the green liquid crystal element 3G passes through the polarization separation film of the polarization beam splitter 307, passes through the dummy glass 309 for correcting the optical path length, enters the polarization beam splitter 308, and the polarization separation thereof. The light passes through the film and travels toward the projection optical system 304. Thus, red light, green light, and blue light that have been color-combined enter the projection optical system 304. Then, the color light after color synthesis is enlarged and projected onto a projection surface 313 such as a screen by the projection optical system 304.

  In this embodiment, the case of using a reflective liquid crystal element is described, but a transmissive liquid crystal element may be used.

  FIG. 2 shows a cross-sectional structure of the reflective liquid crystal elements (3R, 3G, 3B). Reference numeral 101 denotes an AR coating film, 102 denotes a glass substrate, 103 denotes a common electrode, 104 denotes an alignment film, 105 denotes a liquid crystal layer, 106 denotes an alignment film, 107 denotes a pixel electrode, and 108 denotes a Si substrate.

  The liquid crystal driver 303 shown in FIG. 1 drives each pixel by the above-described subframe driving method. That is, one frame period is divided into a plurality of subframe periods on the time axis, and on (applied) and off (non-applied) of a predetermined voltage for the pixel is controlled for each subframe period according to the gradation data. A gradation is formed (displayed) on the pixel. One frame period is a period during which one frame image is displayed on the liquid crystal element. In this embodiment, the liquid crystal element is driven at 120 Hz, and one frame period is set to 8.33 ms. The turning on and off of the predetermined voltage can be paraphrased as application of the first voltage (predetermined voltage) and application of the second voltage lower than the first voltage.

  Hereinafter, the setting of the subframe period and the gradation data in the liquid crystal driver 303 will be described. The liquid crystal driver 303 may be configured by a computer, and the setting of the following subframe period and on / off of a predetermined voltage for each subframe period may be controlled according to a liquid crystal driving program as a computer program.

  FIG. 3 shows the division of one frame period into a plurality of subframe periods (bit lengths) in this embodiment. The numerical value described on each subframe indicates a time weight within one frame period of the subframe. In this embodiment, 96 gradations are expressed. In the description here, the period having the time weight of 1 + 2 + 4 + 8 is referred to as the A subframe period (first period), and the bit indicating the gradation expressed in the A subframe period is referred to as the lower bit. In addition, 10 subframe periods with a time weight of 8 are collectively referred to as a B subframe period (second period), and a bit indicating a gradation expressed in binary in the B subframe period is referred to as an upper bit. The time weight 1 corresponds to 0.087 ms, and the time weight 8 corresponds to 0.69 ms.

  Further, a subframe period in which the predetermined voltage is turned on (a first voltage is applied) is referred to as an on period, and a subframe period in which the predetermined voltage is turned off (a second voltage is applied) is referred to as an off period.

  FIG. 4 shows the gradation data in the A subframe period shown in FIG. The vertical axis represents gradation and the horizontal axis represents one frame period. In the A subframe period, 16 gradations are expressed. In the figure, the white sub-frame period indicates an ON period in which the above-described predetermined voltage is applied so that the pixel is in a white display state, and the black sub-frame period is OFF so that the pixel is in a black display state. Indicates the off period.

  FIG. 5 shows gradation data in the A and B subframe periods (lower and upper bits) in the present embodiment. This gradation data is gradation data for expressing 96 gradations as all gradations. In this gradation data, an A subframe period (lower bit) is arranged at the time center of one frame period, and a B subframe period (upper bit) is divided into 1SF to 5SF and 6SF to 10SF before and after that. Has been placed. That is, the B subframe period is divided into two, and each B subframe period includes two or more subframe periods.

  According to this gradation data, when displaying adjacent gradations that are two gradations adjacent to each other, for example, 48 gradations and 49 gradations, to adjacent pixels that are two adjacent pixels in the liquid crystal element, the A sub The frame period is an on period for 48 gradations and an off period for 49 gradations. In the 48 gradations, 1SF, 4SF, 5SF, 6SF, 7SF, and 10SF in the B subframe period are off periods, and 2SF, 3SF, 8SF, and 9SF are on periods. On the other hand, for 49 gradations, 1SF, 5SF, 6SF, and 10SF in the B subframe period are off periods, and 2SF, 3SF, 4SF, 7SF, 8SF, and 9SF are on periods. When such an adjacent gradation is displayed on an adjacent pixel, an ON / OFF adjacent period in which the ON period and the OFF period overlap is generated in the adjacent pixel. Specifically, when 48 gradations and 49 gradations are displayed on adjacent pixels, 4SF and 7SF in the B subframe period are on / off adjacent periods.

  Here, the gradation data of the present embodiment is compared with the conventional gradation data shown in FIG. In the grayscale data in FIG. 18, the B subframe period continues as a unit after the A subframe period, but in the grayscale data of this embodiment shown in FIG. 5, the B subframe period is divided before and after the A subframe period. Are arranged. For example, paying attention to 48 and 49 gradations, in FIG. 18, 5SF and 6SF in the B subframe period are on / off adjacent periods, and 16 on / off adjacent periods continue as time weights. . This is the same for the other adjacent gradations, ie, 16 gradation and 17 gradation, 32 gradation and 33 gradation, 64 gradation and 65 gradation, 80 gradation and 81 gradation, and the like. On the other hand, in this embodiment shown in FIG. 5, in any of the above adjacent gradations, the ON / OFF adjacent period continues in the B subframe period as one time subframe of 8 as a time weight. The period is (= 0.69 ms). A plurality (two) of ON / OFF adjacent periods, which are one subframe period, are separated from each other across the A subframe period.

  Next, the effect obtained by distributing the ON / OFF adjacent periods in a distributed manner as in this embodiment will be described.

  First, as shown in FIG. 6, when the pixels arranged in a matrix form are switched from the all-white display state to the monochrome display state in which white and black are alternately displayed for each pixel line, and from the all-black display state to the monochrome display state. The response characteristics of the liquid crystal when switching to the display state will be described. The 4 × 4 pixels shown in FIG. 6 are arranged in a matrix with a pixel pitch of 8 μm. In the all white display state, both the pixels of the A pixel line and the pixels of the B pixel line in FIG. 6 display white. In the monochrome display state, the pixels of the A pixel line are switched from the white display state to the black display state, and the pixels of the B pixel line are maintained in the white display state.

  FIG. 7 shows the response characteristics of the liquid crystal. The horizontal axis indicates the position of the pixel, and the vertical axis indicates the brightness at each pixel (however, the ratio when white is 1). 0 to 8 μm on the horizontal axis represents pixels of the A pixel line shown in FIG. 6, and 8 to 16 μm represents pixels of the B pixel line. The plurality of curves indicate the brightness for each elapsed time (0.3 ms, 0.6 ms, 1.0 ms, 1.3 ms) when the switching point from the all white display state to the black and white display state is set to 0 ms.

  As described above, the pixels of the A pixel line are switched from the white display state to the black display state. However, the pixels of the A pixel line are relatively uniformly bright without being affected by disclination because of the pretilt angle direction in the liquid crystal. Changes (darkens). On the other hand, in the pixels of the B pixel line, disclination does not occur in the all white display state. However, the brightness curve gradually becomes distorted as time passes under the influence of disclination after the black-and-white display state is reached, and darkens in the vicinity of 12 μm to 16 μm (dark lines appear).

  In general, the gamma curve (gamma characteristic) that determines the drive gradation of a liquid crystal element relative to the input gradation shows the response characteristics when changing the gradation while displaying the same gradation on the entire surface of the liquid crystal element where no disclination occurs. Created as a premise. For this reason, when a liquid crystal element is driven using such a gamma curve, disclination occurs in a monochrome display state, and it is possible to obtain a brightness lower than the original brightness corresponding to the gamma curve.

  FIG. 8 shows changes in brightness depending on the presence or absence of disclination when the liquid crystal element is switched from the all white display state to the black and white display state. The horizontal axis represents the elapsed time from the switching point, and the vertical axis represents the change in the integrated value of the total brightness (hereinafter simply referred to as brightness) of the pixels of the A and B pixel lines. The brightness is shown as a ratio when the all white display state is 1. When disclination occurs (“with disclination”), the brightness of the pixel of the A pixel line changes with a characteristic close to the response characteristic shown in the vicinity of 1 to 6 μm in FIG. The brightness of the pixels is in a state where white is displayed with 100% brightness. As the time elapses thereafter, the amount of decrease in brightness when disclination occurs is larger than the amount of decrease in brightness when no disclination occurs (“no disclination”). It will become.

  On the other hand, when switching from the all black display state to the black and white display, both the pixel of the A pixel line and the pixel of the B pixel line shown in FIG. 6 are changed from the black display state to the B pixel while the pixels of the A pixel line are kept in the black display state. The line pixels are set to the white display state. FIG. 9 shows the response characteristics of the liquid crystal at this time. The horizontal axis indicates the position of the pixel, and the vertical axis indicates the brightness at each pixel (however, the ratio when white is 1). 0 to 8 μm on the horizontal axis represents pixels of the A pixel line shown in FIG. 6, and 8 to 16 μm represents pixels of the B pixel line. The plurality of curves indicate the brightness for each elapsed time (0.3 ms, 0.6 ms, 1.0 ms, 1.3 ms) when the switching time from the all black display state to the black and white display state is set to 0 ms.

  As described above, the pixels of the B pixel line are switched from the black display state to the white display state, but the pixels of the B pixel line are gradually affected with the disclination after the white display state and gradually. The brightness curve becomes distorted. And it becomes dark especially in the vicinity of 12 μm to 16 μm (dark lines appear). Also, the irregular shape of the brightness curve becomes more prominent with the passage of time.

  As described above, the gamma curve (gamma characteristic) that determines the drive gradation of the liquid crystal element relative to the input gradation generally changes the gradation while displaying the same gradation on the entire surface of the liquid crystal element where no disclination occurs. It is created on the assumption of the response characteristics when For this reason, when a liquid crystal element is driven using such a gamma curve, disclination occurs in a monochrome display state, and it is possible to obtain a brightness lower than the original brightness corresponding to the gamma curve.

  FIG. 10 shows changes in brightness depending on the presence or absence of disclination when the liquid crystal element is switched from the all black display state to the black and white display state. The abscissa represents the elapsed time from the switching point, and the ordinate represents the integrated value of the total brightness of the pixels of the A and B pixel lines (hereinafter simply referred to as brightness and the ratio when the all white display state is 1). ). As for the brightness when disclination does not occur (“no disclination”), the pixels in the A pixel line are always in the black display state, and the pixels in the B pixel line are switched from the black display state to the white display state. It shows the change in brightness as you go. On the other hand, when disclination occurs (“with disclination”), it indicates a change in the integrated value of the sum of the brightness of the pixels of the A pixel line and the B pixel line shown in FIG. .

In FIG. 10, when disclination occurs, the amount of increase in brightness over time is smaller than when disclination does not occur. That is, the longer the disclination occurs after switching from the all black display state to the black and white display state, the darker the disclination does not occur.
Next, a case where 48 gradations are displayed on the pixels of the A pixel line and 49 gradations are displayed on the pixels of the B pixel line based on the conventional gradation data shown in FIG. When this gradation data is used, the period in which the disclination occurs is a B subframe period in which the A pixel line pixel is in the black display state and the B pixel line pixel is in the white display state. 5SF and 6SF. 4SF before 5SF is a period in which both the pixels of the A pixel line and the B pixel line pixels are in the white display state, and no disclination occurs.

  The response characteristics of the liquid crystal from 5SF to 6SF are characteristics corresponding to “with disclination” in FIG. Since 4SF is in an all-white display state, 100% brightness is output, and disclination occurs during 1.39 ms from the start of 5SF to the end of 6SF. 8 corresponds to 0 ms, and the end of 6SF corresponds to 1.39 ms. At this time, the brightness decreases to 0.27 from 0.5 when no disclination occurs. As described above, on the basis of the gamma characteristic created on the premise of the same gradation on the entire surface, the ratio becomes as dark as 54% (= 0.27 / 0.5) from 5SF to 6SF at which disclination occurs.

  On the other hand, in this embodiment, 48 gradations are displayed on the pixel (second pixel) of the A pixel line by the gradation data shown in FIG. 5, and 49 gradations are displayed on the pixel (first pixel) of the B pixel line. A case of displaying is described. The period in which the disclination occurs when using this gradation data is 4SF and 7SF in the B subframe period in which the pixels of the A pixel line and the pixels of the B pixel line are in the disclination occurrence display state. 3SF before 4SF is a period in which both the pixels of the A pixel line and the pixels of the B pixel line are in the white display state and no disclination occurs.

  The response characteristic of the liquid crystal at 4SF is a characteristic corresponding to “with disclination” in FIG. Since 3SF is in an all-white display state, 100% brightness is output, and disclination occurs during 0.69 ms of 4SF. Therefore, the start time of 4SF corresponds to 0 ms in FIG. The end time corresponds to 0.69 ms. At this time, the brightness decreases only to 0.65 compared to 0.7 when no disclination occurs.

  Further, the response characteristic of the liquid crystal at 7SF, which is a sub-frame period in which another disclination occurs, is a characteristic corresponding to “with disclination” in FIG. In 6SF, since the display is all black, the brightness is 0%, and disclination occurs during 0.69 ms of 7SF. Therefore, the start time of 7SF corresponds to 0 ms in FIG. 10 and the end time of 7SF is reached. Corresponds to 0.69 ms. At this time, the brightness decreases only to 0.18, compared to 0.25 when no disclination occurs.

  The sum of brightness when disclination does not occur between 4SF and 7SF is 0.95 (= 0.70 + 0.25), whereas the sum of brightness when disclination occurs is 0.83 (= 0.65 + 0.18). When the gamma characteristic created on the premise of the same gradation on the entire surface is used as a reference, the display becomes dark only up to 87% (= 0.83 / 0.95) in the disclination occurrence display state. That is, according to the present embodiment, it is possible to suppress a decrease in brightness.

  Next, a case where other adjacent gradations are displayed will be described. First, a case where 16 gradations are displayed on the pixels of the A pixel line shown in FIG. 6 and 17 gradations are displayed on the pixels of the B pixel line based on the conventional gradation data shown in FIG. 18 will be described. When this gradation data is used, the period in which the disclination occurs is a B subframe period in which the A pixel line pixel is in the black display state and the B pixel line pixel is in the white display state. 1SF and 2SF.

  The response characteristics of the liquid crystal from 1SF to 2SF are characteristics corresponding to “with disclination” in FIG. Disclination occurs during 1.39 ms from the start of 1SF to the end of 2SF. Therefore, the start time of 1SF corresponds to 0 ms in FIG. 10, and the end time of 2SF corresponds to 1.39 ms. At this time, the brightness decreases to 0.27 from 0.5 when no disclination occurs. As described in the first embodiment, on the basis of the gamma characteristic created on the premise of the same gradation on the entire surface, the ratio is 54% (= 0.27 / 0.5) from 1SF to 2SF where disclination occurs. It becomes darker.

  On the other hand, in the present embodiment, 16 gradations are displayed on the pixel (second pixel) of the A pixel line by the gradation data shown in FIG. 5, and 17 gradations are displayed on the pixel (first pixel) of the B pixel line. A case of displaying is described. The period in which the disclination occurs when using this gradation data is 3SF and 8SF in the B subframe period in which the pixels in the A pixel line and the pixels in the B pixel line are in the disclination occurrence display state. In 2SF before 3SF, both the pixels of the A pixel line and the pixels of the B pixel line are in a black display state, and disclination does not occur. The response characteristic of the liquid crystal at 3SF is a characteristic corresponding to “with disclination” in FIG. Since 2SF is in an all black display state, the brightness is 0%, and disclination occurs during 0.69 ms of 3SF. Therefore, the start time of 3SF corresponds to 0 ms in FIG. 10 and the end of 3SF. Corresponds to 0.69 ms. At this time, the brightness decreases only to 0.18, compared to 0.25 when no disclination occurs.

  In addition, the response characteristic of the liquid crystal at 8SF, which is a subframe period in which another disclination occurs, is also a characteristic corresponding to “with disclination” in FIG. In 7SF, since the display is all black, the brightness is 0%, and disclination occurs during 0.69 ms of 8SF. Therefore, the start time of 8SF corresponds to 0 ms in FIG. 10 and the end time of 8SF is reached. Corresponds to 0.69 ms. At this time, the brightness decreases only to 0.18, compared to 0.25 when no disclination occurs.

  The sum of brightness when disclination does not occur between 3SF and 8SF is 0.50 (= 0.25 + 0.25), whereas the sum of brightness when disclination occurs is 0.36 (= 0.18 + 0.18). When the gamma characteristic created on the premise of the same gradation on the entire surface is used as a reference, in the disclination occurrence display state, the ratio becomes dark only up to 72% (= 0.36 / 0.50). That is, according to the present embodiment, it is possible to suppress a decrease in brightness.

  As described above, in this embodiment, a plurality of ON / OFF adjacent periods that are in a disclination display state when displaying adjacent gradations are provided apart (distributed) within one frame period. The continuous on / off adjacent period is shortened. That is, the display state of the disclination occurrence in the adjacent pixels is shifted to another display state before the brightness decrease due to the disclination becomes large. As a result, it is possible to suppress a decrease in brightness due to disclination so that the dark line is not noticeable, and an image with good image quality can be displayed.

  The occurrence of disclination can be suppressed by the liquid crystal element driving method described above (hereinafter referred to as the first driving method). However, in order to make dark lines due to disclination inconspicuous, the following driving method (hereinafter referred to as the second driving method) is also used in this embodiment.

  FIG. 11 shows an internal configuration of the liquid crystal driver 303. The scaler 400 corresponds to the video input unit 303a shown in FIG. 1, and takes in an input video signal via a receiver IC (not shown) such as DVI or HDMI (registered trademark). Scaler 400 down-converts or up-converts the input video signal by the scaling function and outputs input image data in a predetermined image format. The input image data is composed of a plurality of continuous input frame image data.

  The drive circuit unit 303b sequentially receives the input frame image data from the scaler 400, and drives each pixel of the liquid crystal element 3 (three liquid crystal elements 3R, 3G, 3B shown in FIG. 1). A pixel drive signal for displaying a tone is generated. The drive circuit unit 303b includes a double speed circuit 411, a gain circuit 412, a VTγ circuit 413, a color unevenness circuit 414, and a PWM circuit 415.

  The double speed circuit 411 writes each input frame image data to the frame memory 420 and generates a plurality of frame image data for one input frame image data. In this embodiment, when the input frequency is 60 Hz, two frame image data are generated at a period corresponding to 120 Hz. In the following description, one of these two frame image data is referred to as ODD (odd number) input frame data, and the other is referred to as EVEN (even number) input frame data. These ODD and EVEN input frame data are the same image data as the input frame image data.

  The gain circuit 412 multiplies the ODD input frame data and the EVEN input frame data from the double speed circuit 411 (multiplies the gain coefficient). Thereby, ODD output frame data and EVEN output frame data as output frame image data are generated. The gain circuit 412 can make the gain applied to the ODD input frame data and the EVEN input frame data different from each other. The double speed circuit 411 and the gain circuit 412 constitute image data generating means.

  Here, by setting a gain (third gain) applied to one of the ODD and EVEN input frame data to 0, black is displayed on all pixels of the liquid crystal element 3 (a black scale having the same gradation in all pixels). All black frame image data can be generated. Thereby, what is called black insertion can be performed and the visibility of a moving image can be improved. However, if black insertion is performed, a change in brightness in the frame period may be noticeable as flicker. For this reason, the third gain applied to one of the ODD and EVEN input frame data is not 0, but is a low gain of 50% or less of the higher gain of the first and second gains described later. Thereby, the visibility of a moving image can be improved, suppressing a flicker. A driving method in which a bright frame image and a dark frame image are alternately displayed by applying a non-zero gain to one of ODD and EVEN input frame data in this way is called light / dark driving.

  In the following description, the one obtained as a result of applying the third gain (0 or low gain) to the ODD or EVEN input frame data among the ODD and EVEN output frame data is referred to as low gradation frame image data. On the other hand, the one obtained as a result of applying the first or second gain described later to the ODD or EVEN input frame data is referred to as output frame image data.

  In this way, the double speed circuit 411 generates ODD and EVEN input frame data for the first input frame image data among the input frame image data that are continuously input. Then, the gain circuit 412 applies a first gain to one of the ODD and EVEN input frame data, and applies a third gain to the other. Thus, first output frame image data as output frame image data and first low gradation frame image data as low gradation frame image data are generated. In addition, the double speed circuit 411 generates ODD and EVEN input frame data for second input frame image data continuous to the first input frame image data among the input frame image data continuously input. Then, the gain circuit 412 applies a second gain to one of the ODD and EVEN input frame data, and applies a third gain to the other. Thus, second output frame image data as output frame image data and second low gradation frame image data as low gradation frame image data are generated.

  Thereafter, the input frame image data continuously input to the double speed circuit 411 is also referred to as first and second input frame image data. That is, the first and second input frame image data are repeatedly input to the double speed circuit 411 alternately. As a result, the gain circuit 412 repeatedly generates the first output frame image data and the first low gradation frame image data, and the second output frame image data and the second low gradation frame image data alternately. .

  The VTγ circuit 413 performs gradation characteristics that change according to the response characteristics of the liquid crystal of the liquid crystal element 3 for each output frame image data from the gain circuit 412 (and also for each low gradation frame image data as necessary). Γ correction is performed so as to obtain necessary optical characteristics.

  The color unevenness circuit 414 applies to each output frame image data after the γ correction from the VTγ circuit 413 (and also to each low gradation frame image data if necessary), and the optical system of the projector including the liquid crystal panel 3. The color unevenness that occurs in step 1 is corrected.

  The PWM circuit (driving means) 415 drives the liquid crystal element 3 by the sub-frame driving method described above based on each output frame image data and each low gradation frame image data from the color unevenness correction circuit 115.

  Next, the operation of the gain circuit 412 will be specifically described. For example, a case where 48 gradations and 49 gradations adjacent to each other in the liquid crystal element 3 are displayed will be described. Here, a case will be described in which the above-described black insertion is performed by applying 0 as the third gain to EVEN input frame data. Pixel data of two adjacent pixel positions corresponding to the adjacent pixels in the ODD input frame data sequentially input to the gain circuit 412 (that is, adjacent pixel positions corresponding to each other between the first and second input frame image data) is It has 48 and 49 gradations. In the following description, the pixel data at the adjacent pixel position in each frame image data is referred to as adjacent pixel data.

  The gain circuit 412 multiplies the ODD input frame data generated for the first input frame image data by the double speed circuit 411 with a first gain to generate first output frame image data. Also, the gain circuit 412 applies a second gain different from the first gain to the ODD input frame data generated for the second input frame image data by the double speed circuit 411, and outputs the second output frame image. Is generated. Here, pixel data at pixel positions corresponding to each other between the first and second input frame image data have the same gradation.

  In FIG. 12A, in the Nth and N + 2th frames, the first gain applied to the ODD input frame data generated for the first input frame image data is 1.0 times (100%). The example which produced | generated the 1st output frame image data (1st) is shown. In this example, in the (N + 1) th and (N + 3) th frames, the second gain applied to the ODD input frame data generated for the second input frame image data is set to 0.9 times (90%) and the second output is set. Frame image data (2nd) is generated. Thereby, the gradation of the adjacent pixel data in the first output frame image data (1st) output from the gain circuit 412 becomes 48 and 49, and the adjacent pixel data in the second output frame image data (2nd) The gradation is 43 and 44 (rounded off after the decimal point). All black frame image data (shown as 3rd in the figure) is inserted between the first output frame image data (1st) and the second output frame image data (2nd).

  In this way, the liquid crystal element 3 has the first output frame image data, all black frame image data (first low gradation frame image data), second output frame image data, and all black frame image data (first black frame image data). 2 low gradation frame image data). That is, the adjacent pixels of the liquid crystal element 3 are 48 gradations and 49 gradations in the N frame, 0 gradations and 0 gradations in the N + 1 frame, 43 gradations and 44 gradations in the N + 1 frame, and 0 in the N + 2 frame. Gradation and 0 gradation are displayed, and in subsequent frames, these gradations are displayed cyclically in this order.

  Note that the gain circuit 412 is configured so that the sum of the first and second gains is the same for the first and second input frame image data (that is, ODD input frame data) that are repeatedly input. The generation of the second output frame image data is repeated. The sum of the first and second gains here is 100% + 90% = 190%.

  FIG. 13A shows a case where the liquid crystal element 3 is sequentially driven by the first and second output frame image data and all black frame image data generated without applying different gains to the ODD input frame data. A display image (projected image by a projector) is shown. In the figure, the display image when the liquid crystal element 3 is driven by the first output frame image data is shown as a 1st frame, and the display image when the liquid crystal element 3 is driven by the second output frame image data is shown as a 2nd frame. ing. Further, the display image when the liquid crystal element 3 is driven by the all black frame image data is shown as a 3rd frame. FIG. 13C shows a display image that should be originally displayed.

  In FIG. 13A, both the first and second output frame image data have 0 to 64 gradations from the upper end to the lower end. On the rightmost side of the figure, an image visually recognized by an observer who continuously observes the 1st and 2nd frames (and 3rd frames) is shown. Since the pixel data of all the pixel positions corresponding to each other in the first and second output frame image data have the same gradation, the 1st frame and the 2nd frame are the same image. As a result, in both the 1st and 2nd frames, dark lines due to disclination appear at positions such as 16-17 gradation, 32-33 gradation, and 48-49 gradation. In the figure, dark lines are shown dark for the sake of clarity, but since the liquid crystal element 3 is actually driven by the first driving method described above, only dark lines appear. However, the observer can visually recognize it as a dark line.

  FIG. 13B shows the liquid crystal element 3 based on the first and second output frame image data and all black frame image data generated by applying different gains (100% and 90%) to the ODD input frame data. The 1st, 2nd, and 3rd frames in the case of sequentially driving are shown. The first output frame image data has 0 to 64 gradations corresponding to a gain of 100% from the upper end to the lower end. On the other hand, the second output frame image data has 0 to 58 gradations corresponding to a gain of 90% from the upper end to the lower end. As a result, the position of the dark line due to disclination on the 1st frame and the position of the dark line on the 2nd frame are different (shifted) from each other. For example, the position of the dark line (48-49 gradation position) a on the 1st frame is shifted from the position b of the dark line on the 2nd frame. Therefore, in the image visually recognized by the observer shown on the rightmost side of the figure, the dark line becomes approximately ½ dark by averaging the 1st frame and the 2nd frame. As a result, dark lines can be made less noticeable than when only the liquid crystal element 3 is driven by the first driving method.

  FIGS. 14A and 14B show examples of specific display images. FIG. 14C shows a display image that should be originally displayed. FIG. 14A shows the 1st frame and 2nd when the liquid crystal element 3 is sequentially driven by the first and second output frame image data generated without applying different gains to the ODD input frame data by the gain circuit 412. Indicates a frame. In addition, an image visually recognized by the observer is shown on the leftmost side of the figure. Since the position of the dark line by the disclination in the 1st frame and the 2nd frame is the same, the dark line is conspicuous to some extent in the visually recognized image.

  On the other hand, FIG. 14B shows the liquid crystal element 3 based on the first and second output frame image data generated by applying different gains (100% and 90%) to the ODD input frame data by the gain circuit 412. 1st frame and 2nd frame in the case of driving sequentially. The brightest gradation on the outside is 64 in the 1st frame and 58 in the 2nd frame. The position of the dark line due to disclination on the 1st frame and the position of the dark line on the 2nd frame are shifted from each other. For this reason, in the visual image shown on the leftmost side of the figure, the dark line is almost inconspicuous by averaging the 1st frame and the 2nd frame.

  As described above, in the second driving method, the pixel data at the corresponding pixel positions in the first and second input frame image data have the same gradation. At this time, the first and second output frame image data are generated so that the pixel data at the corresponding pixel positions have different gradations, and the liquid crystal element 3 is generated by the first and second output frame image data. Drive. Thereby, the position of the dark line in the 1st and 2nd frames displayed can be shifted from each other, and the dark line can be made inconspicuous in the visually recognized image. Moreover, driving by the first and second low gradation frame image data is inserted between the driving of the liquid crystal element 3 by the first and second output frame image data. Thereby, the visibility of a moving image can also be improved.

  In some cases, the second input frame image data includes a region that moves with respect to the first input frame image data. In this case, all the first and second input frame image data correspond to each other. The pixel data at the pixel positions to be processed do not necessarily have the same gradation. However, even in this case, if the pixel data at the corresponding pixel positions in the area that is stationary between the first and second input frame image data have the same gradation, the second data is not included in the area. A driving method can be applied.

  Here, in the first and second output frame image data, the difference between the gradations of the pixel data at the pixel positions corresponding to each other is 20% or less of the higher gradation of these gradations. It is desirable to do. In other words, the difference between the first and second gains used to generate the first and second output frame image data is 20% of the higher one of these first and second gains. The following is desirable. If the difference between gradations or the difference between the first and second gains exceeds 20%, the change in brightness between the 1st frame and the 2nd frame is noticeable as flicker, which is not preferable. The difference between the gradations is preferably 1% or more of the higher gradation among these gradations. In other words, the difference between the first and second gains is desirably 1% or more of the higher one of the first and second gains. If it is less than 1%, the positions of the dark lines in the 1st and 2nd frames are hardly shifted, and the effect of making the dark lines not sufficiently conspicuous cannot be obtained.

  In the above-described embodiment, the case where two frame image data is generated at a cycle corresponding to 120 Hz with respect to input frame image data input at 60 Hz has been described. However, four frame image data are generated at a cycle corresponding to 240 Hz. It may be generated. In this case, two sets of ODD input frame data and EVEN input frame data are generated. Then, for example, as shown in FIG. 12B, the first output frame image data (100% and 90% gains are respectively applied to the first set of ODD input frame data and the second set of ODD input frame data). 1st) and second output frame image data (2nd). The first set of EVEN input frame data and the second set of EVEN input frame data are each multiplied by a gain of 0 to generate low gradation (all black) frame image data (3rd). Even in this case, the same effect as in FIG. 13B or FIG. 14B can be obtained.

  Further, the gain applied to the first set of ODD input frame data and the second set of ODD input frame data for each piece of continuous input frame image data is not necessarily constant. For example, a gain of 100% and 90% are applied to the first set of ODD input frame data and the second set of ODD input frame data in N frames, respectively. Then, a gain of 97.5% and 92.5% may be applied to the first set of ODD input frame data and the second set of ODD input frame data in the N + 1 frame, respectively. As a result, the four lines whose dark lines are shifted from each other are averaged, so that the dark line has a density of about ¼, so that the dark line can be made more inconspicuous.

Also in this case, the gain circuit 412 has the same sum of the first and second gains for the first and second input frame image data (that is, the ODD input frame data) repeatedly input. Thus, the generation of the first and second output frame image data is repeated. That is,
Sum of first and second gains in N frames = 100% (1st) + 90% (2nd) = 190%
Sum of first and second gains in N + 1 frame = 97.5% (1st) + 92.5% (2nd) = 190%
Set each gain so that.

  Although the case where black insertion is performed has been described so far, the same effect can be obtained even when light / dark driving is performed. When bright / dark driving is performed, the same gain as that for generating the first and second output frame image data when performing the black insertion described above may be set for a bright frame. For dark frames, the low gradation described above may be constant or may be changed for each frame.

In the above embodiment, the case where the first and second output frame image data are generated by applying the first and second gains to the first and second input frame image data, respectively, has been described. However, a first offset is given to the first input frame image data to generate the first output frame image data, and a second offset is given to the second input frame image data. The output frame image data may be generated. In this case, for the same reason that the difference between the first gain and the second gain is 1% or more and 20% or less of the higher gain, the difference between the first and second offsets is the first and second gains. It is desirable that the maximum gradation value that can be set in the output frame image data is 1% or more and 20% or less. Similarly to the sum of the first and second gains, the first and second offset sums are the same for the first and second input frame image data that are repeatedly input. It is desirable to repeat the generation of the second output frame image data.
(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

303 Liquid crystal drivers 3G, 3R, 3B Reflective liquid crystal elements 1SF to 10SF Subframe period 411 Double speed circuit 412 Gain circuit

A liquid crystal driving device according to one aspect of the present invention drives a liquid crystal element. The apparatus generates first output frame image data for first input frame image data out of continuously input frame image data, and has a gradation higher than that of the first output frame image data. 1st low gradation frame image data is generated, second output frame image data is generated for the second input frame image data, and the gradation is lower than that of the second output frame image data. Data generating means for generating second low gradation frame image data, first output frame image data, first low gradation frame image data, second output frame image data, and second low gradation frame Based on each of the image data, the first voltage indication for the pixels of the liquid crystal element in each of a plurality of subframe periods included in one frame period. When having a driving means for forming a gradation to the pixel by controlling the application of less than the first voltage second voltage. The pixel data at the corresponding pixel positions in the first and second output frame image data have different gray levels, and the difference between the gray levels is the higher of the gray levels. It is characterized by being 20% or less.

A liquid crystal drive program according to another aspect of the present invention is a computer program that causes a computer to drive a liquid crystal element based on an input image. The program causes a computer to generate first output frame image data for first input frame image data out of continuously input frame image data, and from the first output frame image data. The first low-gradation frame image data having a lower gradation is generated, the second output frame image data is generated for the second input frame image data, and the second output frame image data is higher than the second output frame image data. Second low gradation frame image data having a low tone is generated. Further, the computer sequentially transmits one frame based on each of the first output frame image data, the first low gradation frame image data, the second output frame image data, and the second low gradation frame image data. By controlling the application of the first voltage to the pixel of the liquid crystal element and the application of the second voltage lower than the first voltage in each of the plurality of subframe periods included in the period, gradation is formed in the pixel. The pixel data at the corresponding pixel positions in the first and second output frame image data have different gray levels, and the difference between the gray levels is the higher of the gray levels. It is characterized by being 20% or less.

A liquid crystal driving device according to one aspect of the present invention drives a liquid crystal element. The apparatus generates first output frame image data for first input frame image data out of continuously input frame image data, and has a gradation higher than that of the first output frame image data. 1st low gradation frame image data is generated, second output frame image data is generated for the second input frame image data, and the gradation is lower than that of the second output frame image data. Image data generating means for generating second low gradation frame image data, first output frame image data, first low gradation frame image data, second output frame image data, and second low gradation Based on each of the frame image data, sequentially, the first voltage for the pixels of the liquid crystal element in each of a plurality of subframe periods included in one frame period And a drive means for forming a gradation to the pixel by controlling the application of the applied and lower than the first voltage second voltage. Then, the image data generation means generates the first output frame image data by multiplying the first input frame image data by the first gain, and the second input frame image data. The second output frame image data is generated by applying a gain, and the difference between the first gain and the second gain is 20% or less of the higher one of the first and second gains. It is characterized by.

A liquid crystal drive program according to another aspect of the present invention is a computer program that causes a computer to drive a liquid crystal element based on an input image. The program causes a computer to generate first output frame image data for first input frame image data out of continuously input frame image data, and from the first output frame image data. The first low-gradation frame image data having a lower gradation is generated, the second output frame image data is generated for the second input frame image data, and the second output frame image data is higher than the second output frame image data. Second low gradation frame image data having a low tone is generated. Further, the computer sequentially transmits one frame based on each of the first output frame image data, the first low gradation frame image data, the second output frame image data, and the second low gradation frame image data. By controlling the application of the first voltage to the pixel of the liquid crystal element and the application of the second voltage lower than the first voltage in each of the plurality of subframe periods included in the period, gradation is formed in the pixel. The step of generating the image data includes generating the first output frame image data by multiplying the first input frame image data by the first gain, and the second input frame image data. The second output frame image data is generated by multiplying the gain of 2, and the difference between the first gain and the second gain is 20% or less of the higher one of the first and second gains. It is characterized by being.

FIG. 10 shows changes in brightness depending on the presence or absence of disclination when the liquid crystal element is switched from the all black display state to the black and white display state. The horizontal axis represents elapsed time from the switching time point, and the vertical axis represents the integral value of the total brightness of the pixels of the A and B pixel line (hereinafter, simply referred to as brightness, a ratio of time taken as 1 a all white display state Show). As for the brightness when disclination does not occur (“no disclination”), the pixels in the A pixel line are always in the black display state, and the pixels in the B pixel line are switched from the black display state to the white display state. It shows the change in brightness as you go. On the other hand, when disclination occurs (“with disclination”), it indicates a change in the integrated value of the sum of the brightness of the pixels of the A pixel line and the B pixel line shown in FIG. .

The PWM circuit (driving means) 415 drives the liquid crystal element 3 by the sub-frame driving method described above based on each output frame image data and each low gradation frame image data from the color unevenness correction circuit 414 .

In this way, the liquid crystal element 3 has the first output frame image data, all black frame image data (first low gradation frame image data), second output frame image data, and all black frame image data (first black frame image data). 2 low gradation frame image data). That is, the adjacent pixels of the liquid crystal element 3 displays a 0 gradation and 0 level after displaying 48 gray-scale and 49 gradations N frame, after displaying the 43 tone and 44 gradation N + 1 frame 0 Gradation and 0 gradation are displayed, and in subsequent frames, these gradations are displayed cyclically in this order.

FIGS. 14A and 14B show examples of specific display images. FIG. 14C shows a display image that should be originally displayed. FIG. 14A shows the 1st frame and 2nd when the liquid crystal element 3 is sequentially driven by the first and second output frame image data generated without applying different gains to the ODD input frame data by the gain circuit 412. Indicates a frame. Further, the rightmost side of the figure shows the image to be viewed by an observer. Since the position of the dark line by the disclination in the 1st frame and the 2nd frame is the same, the dark line is conspicuous to some extent in the visually recognized image.

Claims (13)

A liquid crystal driving device for driving a liquid crystal element,
The first output frame image data is generated for the first input frame image data among the input frame image data continuously input, and the first has lower gradation than the first output frame image data. Is generated with respect to the second input frame image data, the second output frame image data is generated, and the second output frame image data has a lower gradation than the second output frame image data. Data generation means for generating gradation frame image data;
One frame period sequentially based on each of the first output frame image data, the first low gradation frame image data, the second output frame image data, and the second low gradation frame image data Driving to form a gradation in the pixel by controlling the application of the first voltage and the application of the second voltage lower than the first voltage to the pixel of the liquid crystal element in each of a plurality of subframe periods included in the pixel Means,
Pixel data at corresponding pixel positions in the first and second output frame image data when the pixel data at corresponding pixel positions in the first and second input frame image data have the same gradation. A liquid crystal driving device characterized in that they have different gradations, and the difference between the gradations is 20% or less of the higher gradation of these gradations. The image data generating means generates the first output frame image data by applying a first gain to the first input frame image data, and generates a first output frame image data with respect to the second input frame image data. Generating the second output frame image data with a gain of 2;
2. The liquid crystal driving device according to claim 1, wherein a difference between the first gain and the second gain is 20% or less of a higher one of the first and second gains. .   The liquid crystal driving device according to claim 2, wherein a difference between the first gain and the second gain is 1% or more of the higher gain.   When the first and second input frame image data are repeatedly input, the image data generating means outputs the first and second outputs so that the sum of the first and second gains is the same. 4. The liquid crystal driving device according to claim 2, wherein the generation of frame image data is repeated. The image data generating means generates the first output frame image data by giving a first offset to the first input frame image data, and generates a first output frame image data with respect to the second input frame image data. Generating the second output frame image data by giving an offset of 2;
2. The difference between the first offset and the second offset is 20% or less of a maximum gradation value that can be set in the first and second output frame image data. The liquid crystal driving device described.   6. The liquid crystal drive according to claim 5, wherein the difference between the first and second offsets is 1% or more of a maximum gradation value that can be set in the first and second output frame image data. apparatus.   When the first and second input frame image data are repeatedly input, the image data generating means outputs the first and second outputs so that the sum of the first and second offsets is the same. 7. The liquid crystal driving device according to claim 5, wherein the generation of frame image data is repeated. The subframe period in which the first voltage is applied to the pixel is an on period, and the subframe period in which the second voltage is applied is an off period. When the sub-frame period that is the on period for the first pixel and the off period for the second pixel among the two pixels is the on / off adjacent period,
The image data generating means applies the first and second pixels to the first and second pixels when the liquid crystal element is driven based on one of the first and second output frame image data. When the on / off adjacent period occurs, the on / off adjacent period does not occur for the first and second pixels when the liquid crystal element is driven based on the other output frame image data. The liquid crystal driving device according to claim 1, wherein a difference between the gradations is given to the first and second output frame image data.   The image data generation means is based on the position where the disclination occurs in the liquid crystal element when the liquid crystal element is driven based on the first output frame image data and the second output frame image data. The difference between the gradations is given to the first and second output frame image data so that a position where the disclination occurs when the liquid crystal element is driven is different from each other. Item 9. The liquid crystal driving device according to any one of Items 1 to 8.   The said 1st and 2nd low gradation frame image data are image data which form the same gradation in all the pixels of the said liquid crystal element, The any one of Claim 1 to 9 characterized by the above-mentioned. Liquid crystal drive device. The image data generation means generates the first and second low gradation frame image data by applying a third gain to the first and second input frame image data,
5. The liquid crystal driving device according to claim 2, wherein the third gain is 50% or less of the higher gain. 6. A liquid crystal element;
An image display device comprising: the liquid crystal driving device according to claim 1. A computer program for causing a computer to drive a liquid crystal element,
In the computer,
The first output frame image data is generated for the first input frame image data among the input frame image data continuously input, and the first has lower gradation than the first output frame image data. Low tone frame image data is generated, second output frame image data is generated for the second input frame image data, and the tone is lower than that of the second output frame image data. Generate gradation frame image data,
One frame period sequentially based on each of the first output frame image data, the first low gradation frame image data, the second output frame image data, and the second low gradation frame image data And controlling the application of the first voltage to the pixel of the liquid crystal element and the application of the second voltage lower than the first voltage in each of the plurality of subframe periods included in the pixel to form a gradation in the pixel,
Pixel data at corresponding pixel positions in the first and second output frame image data when the pixel data at corresponding pixel positions in the first and second input frame image data have the same gradation. A liquid crystal drive program characterized by having different gradations from each other, and the difference between the gradations is 20% or less of the higher gradation of these gradations.