Projection display device and control method for projection display device

Abstract

This shifts the projection position of the panel pixels and suppresses display problems when overdriving. [Solution] The amount of overdrive correction is set and adjusted by a first correction, a second correction, and a third correction. The first correction is a correction that brings the optical response integral value of G from a unit period f1 to a unit period f2 closer to the optical response integral value of R during the same period. The second correction is a correction that improves the falling edge characteristics of the optical response, specifically a correction that results in an optical response with a larger change than the change from the first value to the second value of the gradation level. The third correction is a correction that corrects the discrepancy between the optical response integral values ​​of R and G caused by the second correction.

Description

Technical Field

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[0001] The present invention relates to a projection display device and a control method for a projection display device.

Background Art

[0002] In a liquid crystal projector using a liquid crystal panel, in order to pseudo-increase the resolution, a technique of shifting the projection position of panel pixels projected onto a screen or the like by an optical path shift element is known (see, for example, Patent Document 1). Specifically, this technique is a technique in which one frame period is divided into a plurality of unit periods, and the projection position is shifted so as to be different for each unit period. By this technique, it is possible to make the user perceive that more pixels are projected than the number of panel pixels of the liquid crystal panel.

[0003] In a liquid crystal panel, a blurring phenomenon occurs due to insufficient optical responsiveness to electrical changes. In order to reduce this blurring phenomenon, a technique of determining the gradation data supplied to the liquid crystal panel according to the combination before and after the change of the gradation data, that is, a technique called overdrive is known (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004] <00000​​​​​​​​​​​​​​​​​[Means for solving the problem]

[0006] A projection display device according to one aspect of the present disclosure includes: a first liquid crystal panel having a first liquid crystal element, to which first color light is incident and modulated and emitted as first image light; a second liquid crystal panel having a second liquid crystal element, to which second color light different from the first color light is incident and modulated and emitted as second image light, and the optical response of the second liquid crystal element is slower than the optical response of the first liquid crystal element to voltage changes; a synthesis optical system that combines the first image light and the second image light and emits them as composite light; and the composite light The system includes an optical path shift element that shifts the optical axis in each unit period of a frame period, which includes a first unit period that is temporally earlier and a second unit period that is temporally later; a first liquid crystal panel; a second liquid crystal panel; and a display control device that controls the optical path shift element, wherein the display control device supplies a first data signal to the first liquid crystal element in each unit period included in the frame period, based on the gradation level of the first color light from the pixel data; and based on the gradation level of the second color light from the pixel data... The second data signal is supplied to the second liquid crystal element, and when the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the second color light changes from a first value in the first unit period to a second value in the second unit period, the second data signal in the second unit period is first corrected so that the integral value of the optical response of the second liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first and second data signals in the second unit period are second corrected so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first and second data signals in the first unit period are third corrected so that the integral value of the optical response of the first liquid crystal element in the first and second unit periods approaches the integral value of the optical response of the second liquid crystal element.

[0007] A control method for a projection display device according to one aspect of the present disclosure includes: a first liquid crystal panel having a first liquid crystal element, to which first color light is incident and modulated and emitted as first image light; a second liquid crystal panel having a second liquid crystal element, to which second color light different from the first color light is incident and modulated and emitted as second image light, and the optical response of the second liquid crystal element is slower than the optical response of the first liquid crystal element to voltage changes; a synthesis optical system that synthesizes the first image light and the second image light and emits them as synthesized light; and the optical axis of the synthesized light is set to a first unit period earlier in time and A control method for a projection display device comprising: an optical path shift element that shifts in each unit period of a frame period including a second unit period that is later in time; a first data signal based on the gradation level of the first color light from the pixel data is supplied to the first liquid crystal element in each unit period included in the frame period; and a second data signal based on the gradation level of the second color light from the pixel data is supplied to the second liquid crystal element, wherein the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the second color light When the tuning level changes from the first value in the first unit period to the second value in the second unit period, the second data signal in the second unit period is first corrected so that the integral value of the optical response of the second liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first and second data signals in the second unit period are second corrected so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first and second data signals in the first unit period are third corrected so that the integral value of the optical response of the first liquid crystal element in the first and second unit periods approaches the integral value of the optical response of the second liquid crystal element. The third corrected first data signal is supplied to the first liquid crystal element in the first unit period, the first and third corrected second data signal is supplied to the second liquid crystal element, and the second corrected first data signal is supplied to the first liquid crystal element in the second unit period.The first and third corrected second data signals are supplied to the second liquid crystal element. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing a projection-type display device according to an embodiment. [Figure 2] This block diagram shows the electrical configuration of a projection-type display device. [Figure 3] This is a block diagram showing the configuration of a correction circuit for a projection-type display device. [Figure 4] This is a diagram illustrating the conversion table in the correction circuit. [Figure 5] This block diagram shows the electrical configuration of a liquid crystal panel in a projection display device. [Figure 6] This figure shows the equivalent circuit of a pixel circuit in a liquid crystal panel. [Figure 7] This figure shows the relationship between the duration of one frame and the unit period in a projection-type display device. [Figure 8] This diagram shows the number of image pixels represented by a panel pixel during one frame period. [Figure 9] This figure shows the trajectory of the projection position due to the optical path shift element. [Figure 10] This is a diagram to explain the display malfunction. [Figure 11] This is an explanatory diagram of integrated light quantity in RGB. [Figure 12] This is an explanatory diagram for matching the accumulated light intensity using RGB values. [Figure 13] This is an explanatory diagram for adjusting the correction value using the accumulated light intensity during the falloff. [Figure 14] This is an explanatory diagram for adjusting the correction value using the accumulated light intensity at startup. [Figure 15] This flowchart shows the operation of determining the correction value of the conversion table in the embodiment. [Figure 16] This figure shows the trajectory of the projection position by the optical path shift element in a modified example. [Modes for carrying out the invention]

[0009] The projection display device according to the embodiment will be described below with reference to the drawings. Note that the dimensions and scale of each part in each drawing have been appropriately changed from the actual ones. Furthermore, the embodiments described below are preferred examples and are subject to various technically preferred limitations, but the scope of this disclosure is not limited to these forms unless otherwise stated in the following description.

[0010] Figure 1 shows the optical configuration of a projection-type display device 1 according to an embodiment. As shown in the figure, the projection-type display device 1 includes transmissive liquid crystal panels 100R, 100G, and 100B. Inside the projection-type display device 1 is a light source unit 2102 consisting of a white light source such as a laser. The projected light emitted from the light source unit 2102 is separated into three primary colors, red (R), green (G), and blue (B), by three mirrors 2106 and two dichroic mirrors 2108 arranged inside. Of these, the R light is incident on the liquid crystal panel 100R, the G light on the liquid crystal panel 100G, and the B light on the liquid crystal panel 100B. Furthermore, since the optical path B is longer than the optical paths R and G, it is necessary to prevent losses in the optical path B. For this reason, the optical path B is provided with a relay lens system 2121 consisting of an incident lens 2122, a relay lens 2123, and an exit lens 2124.

[0011] The liquid crystal panel 100R has multiple pixel circuits, as described later. Each of the multiple pixel circuits includes a liquid crystal element. The liquid crystal elements of the liquid crystal panel 100R are driven based on a data signal corresponding to R, and their transmittance is proportional to the voltage of the data signal. Therefore, by individually controlling the transmittance of the liquid crystal elements based on the data signal corresponding to R, a transmitted image of R is generated in the liquid crystal panel 100R. Similarly, in the liquid crystal panel 100G, a transmitted image of G is generated based on the data signal corresponding to G, and in the liquid crystal panel 100B, a transmitted image of B is generated based on the data signal corresponding to B.

[0012] The transmitted images of each color respectively generated by the liquid crystal panels 100R, 100G, and 100B are incident on the dichroic prism 2112 from three directions. In the dichroic prism 2112, the R and B lights are refracted at 90 degrees, while the G light travels straight. Therefore, the dichroic prism 2112 synthesizes the images of each color. The synthesized image by the dichroic prism 2112 is incident on the projection lens 2114 through the optical path shift element 230. The projection lens 2114 enlarges and projects the synthesized image passing through the optical path shift element 230 onto the screen Scr which is the projection surface.

[0013] The optical path shift element 230 shifts the optical path of the light (projection light) emitted from the dichroic prism 2112. Specifically, the optical path shift element 230 shifts the position of the synthesized image to be projected in the left - right direction or / and the up - down direction with respect to the screen Scr which is the projection surface.

[0014] Note that the transmitted images by the liquid crystal panels 100R and 100B are projected after being reflected by the dichroic prism 2112, while the transmitted image by the liquid crystal panel 100G travels straight and is projected. Therefore, the transmitted images of the liquid crystal panels 100R and 100B have a left - right reversed relationship with respect to the transmitted image of the liquid crystal panel 100G.

[0015] FIG. 2 is a block diagram showing the electrical configuration of the projection display device 1. As shown in the figure, the projection display device 1 includes a display control device 20, liquid crystal panels 100R, 100G, and 100B, an optical path shift element 230, and a light source unit 2102.

[0016] Video data Vid_in is supplied from a host device or other higher - level device (not shown) in synchronization with the synchronization signal Sync. The video data Vid_in specifies the gradation levels of the pixels constituting one frame period of the video, for example, 8 bits for each of RGB.

[0017] In addition, the pixels of the image specified by the video data Vid_in are referred to as video pixels, and the data that specifies the gradation level of the video pixels is referred to as video pixel data. However, video pixels and video pixel data are sometimes explained without making a particular distinction. Furthermore, the pixels of the image before or after synthesis by the liquid crystal panel 100R, 100G, or 100B are referred to as panel pixels. Panel pixels that are shifted by the optical path shift element 230 and projected onto the screen Scr are referred to as projected pixels, and the position from which the panel pixels are projected is referred to as the projection position.

[0018] In the liquid crystal panels 100R, 100G, and 100B, the panel pixels are arranged in a matrix when viewed in a planar view. In the embodiment, the arrangement of video pixels specified in the video data Vid_in is, for example, twice as large in the vertical direction and twice as large in the horizontal direction compared to the arrangement of panel pixels in the liquid crystal panels 100R, 100G, or 100B.

[0019] In this embodiment, the color image projected onto the screen Scr is represented by combining the transmitted images of the liquid crystal panels 100R, 100G, and 100B. Therefore, the smallest unit of the color image can be divided into a red subpixel from liquid crystal panel 100R, a green subpixel from liquid crystal panel 100G, and a blue subpixel from liquid crystal panel 100B. However, in cases where it is not necessary to specify the color of the subpixels in liquid crystal panels 100R, 100G, and 100B, or when only brightness and darkness are relevant, it is not necessary to refer to them as subpixels. Therefore, in this explanation, the display units in liquid crystal panels 100R, 100G, and 100B will also be referred to as panel pixels.

[0020] The synchronization signal Sync includes a vertical synchronization signal that instructs the start of vertical scanning of the video data Vid_in, a horizontal synchronization signal that instructs the start of horizontal scanning, and a clock signal that indicates the timing of one video pixel in the video data Vid_in.

[0021] The display control device 20 includes a processing circuit 21, and correction circuits 22R, 22G, and 22B. Based on the synchronization signal Sync, the processing circuit 21 controls the correction circuits 22R, 22G, 22B, the liquid crystal panels 100R, 100G, 100B, and the optical path shift element 230 for each unit period f1 to f4, which will be described later. The optical path shift element 230 shifts the projection position according to the control signal output from the processing circuit 21.

[0022] Figure 3 is a block diagram showing the configuration of the correction circuits 22R, 22G, and 22B. The correction circuit 22R includes a buffer 220R, a delay unit 222R, a conversion table 224R, an adder 226R, and a DA conversion unit 228R.

[0023] Buffer 220R first stores the R component video data Va_R from the video data Vid_in, and then reads out the video data corresponding to the unit period specified by the processing circuit 21 and outputs it. The video data read out from buffer 220R corresponding to the unit period is denoted as V_R(f).

[0024] The delay unit 222R delays the video data Va_R(f) by a time equivalent to one unit period and outputs it as video data Va_R(f-1). Therefore, when a certain panel pixel represents a certain video pixel in the video data Va_R(f), the video data Va_R(f-1) will represent the video pixel that the panel pixel represented one unit period earlier, that is, the video pixel that was represented before the change.

[0025] The conversion table 224R is, for example, a two-dimensional table that takes as input the gradation level of a video pixel indicated by the video data Va_R(f) and the gradation level of a video pixel indicated by the video data Va_R(f-1) from one unit period ago, and outputs an overdrive correction amount Am_R corresponding to those two gradation levels.

[0026] Figure 4 shows an example of conversion table 224R. In conversion table 224R, the correction amount Am_R is pre-formatted and stored in a table corresponding to two tonal levels. Then, the correction amount Am_R corresponding to the two tonal levels is read out and output. Of the two grayscale levels, one is the image data Va_R(f), i.e., the grayscale level of the image pixel in the current unit period, and the other is the image data Va_R(f-1), i.e., the grayscale level of the image pixel in the unit period one unit period prior to the current unit period.

[0027] In this embodiment, the gradation level is specified using 8 bits, resulting in 256 possibilities. When this is matched to each of the two gradation levels, the correction amount Am_R becomes 65536 (=256 × 256). Furthermore, if the correction amount Am_R has 65,536 possible values, not only will the conversion table 224R become very large, but it will also take time to determine the correction amount Am_R corresponding to the two grayscale levels. For this reason, the conversion table 224R may be configured to store the correction amount Am_R according to the combination for each band of grayscale levels.

[0028] The summing unit 226R adds a correction amount Am_R to the gradation level of the video pixels indicated by the video data Va_R(f), and supplies the summing result to the DA conversion unit 228R. The DA conversion unit 228R converts the summation result into an analog voltage data signal Vid_R and supplies the data signal Vid_R to the liquid crystal panel 100R. In this way, the correction circuit 22R overdrives the R component video data Va_R(f), converts it into an analog voltage data signal Vid_R, and supplies it to the liquid crystal panel 100R.

[0029] Similarly, the correction circuit 22G includes a buffer 220G, a delay unit 222G, a conversion table 224G, an adder 226G, and a DA conversion unit 228G. The correction circuit 22G corrects the G component video data Va_G(f) with a correction amount Am_G based on the video data Va_G(f) and the video data Va_G(f-1) before the change, converts it into an analog voltage data signal Vid_G, and supplies it to the liquid crystal panel 100G. The correction circuit 22B includes a buffer 220B, a delay unit 222B, a conversion table 224B, an adder 226B, and a DA conversion unit 228B. The correction circuit 22B corrects the B component video data Va_B(f) with a correction amount Am_B based on the video data Va_B(f) and the video data Va_B(f-1) before the change, converts it into an analog voltage data signal Vid_B, and supplies it to the liquid crystal panel 100B. The settings for the correction amounts Am_R, Am_G, and Am_B will be described later.

[0030] Next, the liquid crystal panels 100R, 100G, and 100B will be generally described as liquid crystal panel 100 without specifying their colors.

[0031] Figure 5 is a block diagram showing the electrical configuration of the liquid crystal panel 100. The liquid crystal panel 100 is provided with a scan line drive circuit 130 and a data line drive circuit 140 around the periphery of the display area 10.

[0032] In the display area 10 of the liquid crystal panel 100, the pixel circuits 110 are arranged in a matrix. More specifically, in the display area 10, multiple scan lines 12 are provided extending horizontally in the figure, and multiple data lines 14 are provided extending vertically in the figure, maintaining electrical isolation from the scan lines 12. The pixel circuits 110 are then arranged in a matrix corresponding to the intersections of the multiple scan lines 12 and the multiple data lines 14.

[0033] If the number of scan lines 12 is m and the number of data lines 14 is n, the pixel circuits 110 are arranged in a matrix with m rows and n columns. Both m and n are integers greater than or equal to 2. In the scan lines 12 and pixel circuits 110, the rows of the matrix are sometimes referred to as rows 1, 2, 3, ..., m in the diagram from top to bottom. Similarly, in the data lines 14 and pixel circuits 110, the columns of the matrix are sometimes referred to as columns 1, 2, 3, ..., n in the diagram from left to right.

[0034] The scan line drive circuit 130 selects scan lines 12 one by one in the order of, for example, the 1st, 2nd, 3rd, ..., mth row, according to the control of the display control device 20, and sets the scan signal to the selected scan line 12 to the H level. The scan line drive circuit 130 also sets the scan signal to the scan lines 12 other than the selected scan line 12 to the L level. The data line drive circuit 140 latches one line of data signals supplied from the video processing circuit 22 according to the control of the display control device 20, and outputs it via the data line 14 to the pixel circuit 110 located on the scan line 12 during the period when the scan signal to the scan line 12 is at a high level.

[0035] Figure 6 shows the equivalent circuits of the pixel circuits 110, consisting of four 2x2 grids corresponding to the intersections of two adjacent scan lines 12 and two adjacent data lines 14. As shown in the figure, the pixel circuit 110 includes a transistor 116 and a liquid crystal element 120. The transistor 116 is, for example, an n-channel thin-film transistor. In the pixel circuit 110, the gate node of the transistor 116 is connected to the scan line 12, its source node is connected to the data line 14, and its drain node is connected to a pixel electrode 118 which is approximately square in plan view.

[0036] The liquid crystal panel 100 has a configuration in which an element substrate on which transistors 116 and pixel electrodes 118 are formed and a counter substrate on which common electrodes 108 are formed face each other, with the electrode formation surfaces facing each other, and the liquid crystal 105 is sealed inside. Therefore, for each pixel circuit 110, a liquid crystal element 120 is formed in which liquid crystal 105 is sandwiched between a pixel electrode 118 and a common electrode 108. Furthermore, the voltage LCcom is applied to the common electrode 108.

[0037] A storage capacitor 109 is provided in parallel with the liquid crystal element 120. One end of the storage capacitor 109 is connected to the pixel electrode 118, and the other end is connected to the capacitance line 107. A voltage constant over time, for example, the same voltage LCcom as the voltage applied to the common electrode 108, is applied to the capacitance line 107. The pixel circuit 110 is arranged in a matrix shape across the horizontal direction, which is the direction in which the scan lines 12 extend, and the vertical direction, which is the direction in which the data lines 14 extend. Therefore, the pixel electrodes 118 included in the pixel circuit 110 are also arranged across both the vertical and horizontal directions.

[0038] When the scanning signal reaches the H level on scan line 12, the transistor 116 of the pixel circuit 110, which is provided in conjunction with that scan line 12, turns ON. When transistor 116 is ON, the data line 14 and the pixel electrode 118 are electrically connected, so the data signal supplied to the data line 14 reaches the pixel electrode 118 via the ON transistor 116. When scan line 12 reaches the L level, transistor 116 turns OFF, but the voltage of the data signal that reached the pixel electrode 118 is maintained by the capacitive and storage capacitance 109 of the liquid crystal element 120.

[0039] In the liquid crystal element 120, the orientation of the liquid crystal molecules changes in response to the electric field generated by the pixel electrode 118 and the common electrode 108. Therefore, the liquid crystal element 120 has a transmittance corresponding to the effective value of the applied voltage. Furthermore, the region in the liquid crystal element 120 that functions as a panel pixel, that is, the region whose transmittance corresponds to the effective value of the voltage, is the region where the pixel electrode 118 and the common electrode 108 overlap when the liquid crystal panel 100 is viewed from above. Since the pixel electrode 118 is square when viewed from above, the shape of the pixel in the liquid crystal panel 100 is also square. Furthermore, in this embodiment, the liquid crystal 105 is a VA (Vertical Alignment) type, and operates in a normally black mode where the transmittance is lowest when the applied voltage to the liquid crystal element 120 is zero, and the transmittance increases as the applied voltage increases.

[0040] The operation of supplying data signals to the pixel electrodes 118 of the liquid crystal element 120 is performed in the order of row 1, 2, 3, ..., m row for each unit period. As a result, a voltage corresponding to the data signal is maintained in each of the liquid crystal elements 120 of the pixel circuit 110 arranged in m rows and n columns, so that each liquid crystal element 120 reaches the desired transmittance, and a transmitted image of the corresponding color is generated by the liquid crystal elements 120 arranged in m rows and n columns. In this way, the transmission image is generated for each RGB channel, and the resulting color image, created by combining the RGB channels, is projected onto the screen (Scr). The data signals Vid_R, Vid_G, and Vid_B, which are output in response to a certain unit period, correspond to the RGB components of the video data corresponding to that unit period. Therefore, a composite color image corresponding to the projection position is projected at that projection position during that unit period.

[0041] Figure 7 shows the relationship between frame duration and unit duration in the projection display device 1 according to this embodiment. As shown in the figure, in this embodiment, one frame (1F) duration is divided into four unit durations. For convenience in distinguishing the four unit durations, they are assigned the designations f1, f2, f3, and f4 in order of time. Note that one frame period is the period during which one frame of the image, indicated by the video data Vid_in from the host device, is supplied. If the frequency of the vertical synchronization signal included in the synchronization signal Sync is 60Hz, then one period is 16.7 milliseconds. In this case, the length of each unit period is 4.17 milliseconds, which is 1 / 4 the length of one frame period.

[0042] In this embodiment, the projection position is changed every unit period f1 to f4, and at each projection position, an image with the image resolution specified by the video data Vid_in reduced to 1 / 4 is made visible to the user. In other words, an image with four times the resolution of the composite image produced by the liquid crystal panels 100R, 100G, and 100B is effectively made visible to the user.

[0043] Next, we will explain the relationship between the image pixels whose gradation level is specified in the image data Vid_in, the panel pixels of the liquid crystal panel 100, and the projection position of the optical path shift element 230. As mentioned above, the optical path shift element 230 shifts the projection pixels synthesized by the dichroic prism 2112, but for convenience, the amount of this shift is converted to the size of the panel pixels projected onto the screen Scr.

[0044] The left column in Figure 8 shows a portion of the image pixel array represented by the video data Vid_in. The right column in Figure 8 shows a portion of the panel pixels that are related to the image pixel array in the left column.

[0045] In the image pixel arrangement shown in Figure 8, for convenience, the image pixels are assigned codes A0-A4 in the first row, B0-B4 in the second row, C0-C4 in the third row, and D0-D4 in the fourth row, respectively, in order to distinguish them. Furthermore, in the panel pixel array, for convenience, the pixels are assigned codes a1 and a2 to the first row and b1 and b2 to the second row, respectively, in order to distinguish them.

[0046] Figure 9 shows which projection position each panel pixel of the liquid crystal panel 100 displays for the video pixel indicated by the video data Vid_in. More specifically, Figure 9 shows which projection position each panel pixel a1 in Figure 8 displays for each unit period f1 to f4. In a unit period f1, panel pixel a1 represents image pixel A1 at the projection position P11 corresponding to image pixel A1. For the sake of explanation, the projection position corresponding to image pixel A1 is referred to as the reference position. Furthermore, for a panel pixel to represent an image pixel, it means that the liquid crystal element 120 of the panel pixel has a transmittance corresponding to the gradation level of the image pixel.

[0047] In a unit period f2, panel pixel a1 represents image pixel A2 at projection position P12, which is shifted 0.5 pixels to the right of the reference projection position P11. During a unit period f3, panel pixel a1 represents image pixel B2 at projection position P13, which is shifted 0.5 pixels downwards from projection position P12. During a unit period f4, panel pixel a1 represents image pixel B1 at projection position P14, which is shifted 0.5 pixels to the left of projection position P13. After a unit period f4, the projection position returns to the reference position P11, which is shifted 0.5 pixels upward from the projection position P14 during the unit period f3.

[0048] Incidentally, the electro-optic responses of the color-specific liquid crystal panels 100R, 100G, and 100B are not uniform; in reality, they differ due to various factors. These factors include differences in temperature due to differences in the amount of light incident on the liquid crystal panel 100, differences in the cell gap, and differences in transmittance due to the wavelength of the light incident on the liquid crystal panel 100.

[0049] Display defects such as trailing lines and color distortion occur due to inconsistent electro-optical responses in the LCD panels 100R, 100G, and 100B. Therefore, we will first explain how to suppress these display defects.

[0050] Figure 11 shows the optical response of the liquid crystal element 120 of panel pixel a1, separated by RGB, when the panel pixel a1 represents the image pixels A1, A2, B2, and B1 shown in Figure 10.

[0051] In Figure 10, image pixels A1 and B2 are "white," where both RGB values ​​are at the highest gradation level, while image pixels A2 and B1 are "black," where both RGB values ​​are at the lowest gradation level. Furthermore, in this example, the cell gap widens in the order of LCD panel 100R, LCD panel 100B, and LCD panel 100G. Therefore, the voltage applied in accordance with the highest grayscale level increases in the order of liquid crystal panel 100R, liquid crystal panel 100B, and liquid crystal panel 100G, according to the cell gap.

[0052] Note that in this figure, as in Figures 12 to 14, the maximum transmittance of liquid crystal panel 100R is normalized to 100% and the minimum transmittance to 0%. Therefore, transmittances higher than the maximum transmittance of liquid crystal panel 100R may exceed 100%, and transmittances lower than the minimum transmittance of liquid crystal panel 100R may fall below 0% (negative value).

[0053] The transmittance of the liquid crystal element 120 is equivalent to the integral value of transmittance per unit time in the human eye. In this embodiment, the panel pixels represent the gradation level of the image pixels for each unit period, but here, since we are looking at the change in gradation level over two unit periods, the unit time for calculating the integral value is set to two unit periods. Note that the transmittance of the liquid crystal element 120 of R when the highest gradation level is reached in unit period f1 and the lowest gradation level is reached in unit period f2 can be considered as the integrated light quantity (optical response integral value) indicated by hatching in the figure.

[0054] In the example shown in the figure, the optical response of liquid crystal panels 100G and 100B is slower than that of liquid crystal panel 100R. As a result, the transmittance at the highest grayscale level in liquid crystal panels 100G and 100B is lower than that at the highest grayscale level in liquid crystal panel 100R. Therefore, when LCD panels 100R, 100G, and 100B are combined, the actual transmittances in RGB differ, resulting in a color that does not become "white" through additive color mixing. More specifically, because the transmittance of LCD panel 100G and 100B is lower than that of LCD panel 100R, the resulting color appears reddish. This phenomenon also occurs with relatively light "gray."

[0055] To suppress the reddish tint, as shown in Figure 12, the applied voltage at the highest grayscale level is corrected by overdrive in the liquid crystal panels 100G and 100B. Specifically, the cumulative light amount of the transmittance in R is corrected to be equal to the cumulative light amount of the transmittance in G, and also corrected to be equal to the cumulative light amount of the transmittance in B (first correction). In other words, the correction amount Am_G for liquid crystal panel 100G and the correction amount Am_B for liquid crystal panel 100B are determined using liquid crystal panel 100R as a reference. This first correction reduces color tinting when attempting to display "white" or a relatively light "gray" in the embodiment.

[0056] If the liquid crystal 105 uses the VA method described above, the optical response when changing from a bright state with high transmittance to a dark state with low transmittance, i.e., during the falling edge, is slower than the optical response when changing from a dark state with high transmittance to a bright state, i.e., during the rising edge. Therefore, if the applied voltage is increased in the liquid crystal panels 100G and 100B when changing from a dark state to a bright state in order to suppress the "white" coloration, the fall-off characteristics in a unit period f2 deteriorate, as shown in Figure 12. This deterioration in the fall-off characteristics in a unit period f2 also applies to the liquid crystal panel 100R, which has not undergone the first correction. As a result, as shown in the right column of Figure 10, a phenomenon occurs where panel pixels a1 that should be perceived as "black" in a unit period f2 appear brighter than "black" along the shift direction. This phenomenon is sometimes called the tail phenomenon because the bright area appears to leave a tail along the shift direction. Furthermore, the trailing effect also occurs over a unit period of f4.

[0057] The cause of the trailing effect is the slow fall-off characteristic of the optical response. Therefore, as shown in Figure 13, when changing from a light state to a dark state, the correction amount is adjusted for each of the RGB components so that the voltage change is greater than the change from the voltage in the light state to the voltage in the dark state (second correction). This second correction improves the fall-off characteristic of the optical response.

[0058] If only the fall-off characteristics of the optical response are improved by the second correction, the integrated light amount of transmittance will decrease. If this decrease differs for each RGB channel, color fringing will occur again. Therefore, the rise-off characteristics of the optical response are corrected by the next correction. In other words, as shown in Figure 14, the correction amount is readjusted for each of the RGB components so that when changing from a dark state to a bright state, the voltage change is greater than the change in voltage from the dark state to the bright state, so that the integral values ​​of the transmittance are the same for RGB (third correction). This third correction suppresses the color fringing in the state where the optical response at the fall time has been improved. Furthermore, in the third correction, the reference time used to determine the integral value of the transmittance is two unit periods, as mentioned above, because it is necessary to consider the repetition of image pixels.

[0059] The correction amount Am_R stored in conversion table 224R, the correction amount Am_G stored in conversion table 224G, and the correction amount Am_B stored in conversion table 224B are set, adjusted, etc., after product installation but before factory shipment.

[0060] Figure 15 is a flowchart showing the operation of setting and adjusting the correction amounts Am_R, Am_G, and Am_B. First, data signals corresponding to the period before the gradation level changes and data signals corresponding to the period after the gradation level changes are alternately supplied to the liquid crystal panel 100R at time intervals corresponding to a unit period to detect the optical response of the transmittance and calculate the integrated light amount of the transmittance (Step Sa1). The gradation level before the change is one of "0" to "255", and the gradation level after the change is one of "0" to "255", so there are 65,536 possible combinations. The integrated light amount of the transmittance corresponding to each of these combinations is calculated. Furthermore, when detecting the optical response of the liquid crystal panel 100R, data signals corresponding to the lowest grayscale level are supplied to the liquid crystal panels 100G and 100B to prevent interference with the detection of the optical response of RG.

[0061] Next, the optical response of the transmittance is detected for the liquid crystal panels 100G and 100B in the same manner, and the integrated light quantity of said transmittance is calculated (step Sa2). In detail, for the liquid crystal panel 100G, a data signal corresponding to the state before the change in grayscale level and a data signal corresponding to the state after the change in grayscale level are supplied alternately at time intervals corresponding to a unit period, the optical response of the transmittance is detected, and the integrated light amount of that transmittance is calculated. There are 65,536 possible combinations of grayscale levels before and after the change, and the integrated light amount of transmittance corresponding to each of these combinations is calculated. Furthermore, when detecting the optical response of LCD panel 100G, data signals corresponding to the lowest grayscale level are supplied to LCD panels 100R and 100B to prevent interference with the detection of the optical response of G.

[0062] Similarly, for the liquid crystal panel 100B, the optical response is detected for each combination of gradation level changes, and the integrated value of the transmittance corresponding to each combination is calculated (step Sa2). When detecting the optical response for the liquid crystal panel 100B, data signals corresponding to the lowest gradation level are supplied to the liquid crystal panels 100R and 100G to avoid affecting the detection of the optical response of B.

[0063] Next, for the liquid crystal panel 100G, a correction amount Am_G is set so that the integrated transmittance value for a given combination of grayscale levels matches the integrated value calculated for the same combination of grayscale levels on the liquid crystal panel 100R. This setting of the correction amount Am_G is performed for each combination of grayscale levels. Similarly, for the liquid crystal panel 100B, the correction amount Am_B is set so that the integrated transmittance value for a given combination of grayscale levels matches the integrated value calculated for the same combination of grayscale levels in the liquid crystal panel 100R. This setting of the correction amount Am_B is performed for each combination of grayscale levels (step Sa3). This sets the correction amounts Am_G and Am_B for the first correction.

[0064] Next, among the combinations of grayscale levels in the LCD panel 100G, the correction amounts Am_G and Am_B corresponding to the combinations that reduce the grayscale level are adjusted to prevent streaking. For the LCD panel 100R, the correction amount Am_R corresponding to the combination that reduces the grayscale level is set to prevent streaking (step Sa4). This sets the correction amount Am_R for the second correction, and adjusts the correction amounts Am_G and Am_B.

[0065] Next, among the combinations of gradation levels in the LCD panel 100G, the correction amounts Am_G and Am_B corresponding to the combinations that increase the gradation level are adjusted to eliminate color fringing (step Sa5). For LCD panel 100R, the correction amount Am_R corresponding to the combination that increases the gradation level is adjusted to eliminate color fringing. This adjusts the correction amounts Am_R, Am_G, and Am_B for the third correction. The correction amount Am_R, adjusted up to the third correction, is stored in conversion table 224R, the similarly adjusted correction amount Am_G is stored in conversion table 224G, and the similarly adjusted correction amount Am_B is stored in conversion table 224B.

[0066] According to this embodiment, when the projection position of the panel pixels is shifted by the optical path shift element 230 and overdrive is applied, display defects such as so-called trailing or color distortion can be suppressed.

[0067] In the embodiments described above, various modifications or applications are possible as follows.

[0068] In this embodiment, the projection position is shifted by 0.5 pixels in the upward, downward, left, or right direction by the optical path shift element 230 for each unit period, converted to panel pixels. However, the following modified example may also be used.

[0069] Figure 16 shows, in a modified example, which projection position the panel pixels use to display the image pixels. As shown in Figure 16, in a unit period f1, panel pixel a1 in Figure 8 represents image pixel A1 at projection position P21, which is the reference position corresponding to the image pixel A1. During a unit period f2, panel pixel a1 represents image pixel B3 at projection position P22, which is shifted 1.0 pixel to the right and 0.5 pixels downward from projection position P21. During a unit period f3, panel pixel a1 represents image pixel D2 at projection position P23, which is shifted 0.5 pixels to the left and 1.0 pixel downwards from projection position P22. In a unit period f4, panel pixel a1 represents image pixel C0 at projection position P24, which is shifted 1.0 pixel to the right and 0.5 pixels upward from projection position P23. After a unit period f4, the projection position returns to the reference position P21, which is shifted 0.5 pixels to the right and 1.0 pixel upward from the projection position P24.

[0070] In the liquid crystal panel 100, microlenses are sometimes provided for each liquid crystal element 120 to improve the light-gathering efficiency of the light incident on the liquid crystal element 120. When microlenses are provided, the projected panel pixels are brightest in the center and become dimmer towards the periphery. In such cases, in the shift path shown in Figure 9, display unevenness may occur due to the uneven distribution of areas where the projection position due to the shift overlaps, with some areas having a large amount and others having a small amount. In contrast, in the modified shift path, the shift amount per unit period is 1.0 pixel or more in panel pixels, which is longer than the path in Figure 9. Therefore, according to the modified path, areas where the projection position overlaps due to the shift are less likely to be unevenly distributed, thus suppressing the occurrence of display unevenness caused by the above uneven distribution.

[0071] In this embodiment, the liquid crystal panel 100 is transmissive, but it may also be reflective.

[0072] In the embodiments, the configuration is such that one frame period is divided into four unit periods, but the number of divisions of one frame period is not limited to "4". Specifically, one frame period may be composed of "2" unit periods, or it may be composed of "3" or "5" or more unit periods.

[0073] From the forms exemplified above, for example, the following aspects can be understood.

[0074] A projection display device according to one embodiment 1 includes a first liquid crystal panel having a first liquid crystal element, into which first color light is incident and modulated and emitted as first image light; a second liquid crystal panel having a second liquid crystal element, into which second color light different from the first color light is incident and modulated and emitted as second image light, and the optical response of the second liquid crystal element is slower than the optical response of the first liquid crystal element to voltage changes; a synthesis optical system that combines the first image light and the second image light and emits them as composite light; and the composite light The system includes an optical path shift element that shifts the optical axis in each unit period of a frame period, which includes a first unit period that is temporally earlier and a second unit period that is temporally later; a first liquid crystal panel; a second liquid crystal panel; and a display control device that controls the optical path shift element, wherein the display control device supplies a first data signal to the first liquid crystal element in each unit period included in the frame period, based on the gradation level of the first color light from the pixel data; and based on the gradation level of the second color light from the pixel data... The second data signal is supplied to the second liquid crystal element, and when the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the second color light changes from a first value in the first unit period to a second value in the second unit period, the second data signal in the second unit period is first corrected so that the integral value of the optical response of the second liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first and second data signals in the second unit period are second corrected so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first and second data signals in the first unit period are third corrected so that the integral value of the optical response of the first liquid crystal element in the first and second unit periods approaches the integral value of the optical response of the second liquid crystal element.

[0075] According to the projection display device of Embodiment 1, in a configuration in which image light emitted from liquid crystal panels with different optical responses is combined and projected, the resolution can be artificially increased by shifting the optical axis with an optical path shift element, and so-called trailing and color fringing that occur when the decrease in optical response is compensated for by overdrive can be suppressed. Note that R (red) light is an example of "first color light," and G (green) light is an example of "second color light." Liquid crystal panel 100R is an example of "first liquid crystal panel," and the liquid crystal element 120 of said liquid crystal panel 100R is an example of "first liquid crystal element," and liquid crystal panel 100G is an example of "second liquid crystal panel," and the liquid crystal element 120 of said liquid crystal panel 100G is an example of "second liquid crystal element." Unit period f1 is an example of "first unit period," and unit period f2 is an example of "second unit period." Data signal Vid_R is an example of "first data signal," and data signal Vid_G is an example of "second data signal."

[0076] A projection display device according to a specific embodiment 2 of embodiment 1 includes a third liquid crystal panel having a third liquid crystal element, to which third color light is incident, modulated and emitted as third image light, and the optical response of the third liquid crystal element is slower than the optical response to voltage changes in the first liquid crystal element, the composite optical system combines the first image light and the second image light with the third image light, and the display control device supplies a third data signal to the third liquid crystal element in each unit period, based on the gradation level of the third color light from the pixel data, the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the third color light changes from the first value in the first unit period to the previous value in the second unit period When the value changes to the second value, the third data signal in the second unit period is first corrected so that the integral value of the optical response of the third liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first data signal and the third data signal in the second unit period are second corrected so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first data signal and the third data signal in the first unit period are third corrected so that the integral value of the optical response of the first liquid crystal element in the first unit period and the integral value of the optical response of the third liquid crystal element approach each other.

[0077] According to the projection display device of embodiment 2, color display becomes possible by combining the first color light, the second color light, and the third color light. Note that B (blue) light is an example of "third color light," liquid crystal panel 100B is an example of "third liquid crystal panel," liquid crystal element 120 of the liquid crystal panel 100B is an example of "third liquid crystal element," and data signal Vid_B is an example of "third data signal."

[0078] In a projection display device according to another specific embodiment 3 of embodiment 1, the amount by which the optical path shift element shifts the optical axis from the first unit period to the second unit period is the distance of half a pixel of the pitch in the panel pixels projected by the composite light. According to the projection-type display device of embodiment 3, the amount by which the optical path shift element shifts the optical axis for each unit period can be suppressed.

[0079] In a projection display device according to another specific embodiment 4 of embodiment 1, the amount by which the optical path shift element shifts the optical axis from the first unit period to the second unit period is a distance exceeding one pixel of the pitch in the panel pixels projected by the composite light. According to the projection display device of embodiment 4, since the shift distance is long, it is possible to suppress display unevenness caused by the uneven distribution of areas where the projection position due to the shift overlaps with areas where it overlaps with areas where it overlaps with areas where it does not.

[0080] A control method for a projection display device according to Embodiment 5 includes: a first liquid crystal panel having a first liquid crystal element, to which first color light is incident and modulated and emitted as first image light; a second liquid crystal panel having a second liquid crystal element, to which second color light different from the first color light is incident and modulated and emitted as second image light, and the optical response of the second liquid crystal element is slower than the optical response to voltage changes in the first liquid crystal element; a composite optical system that combines the first image light and the second image light and emits them as composite light; and the optical axis of the composite light is set to a first unit period earlier in time and in time A control method for a projection display device comprising an optical path shift element that shifts in each unit period of a frame period including a subsequent second unit period, wherein in each unit period included in the frame period, a first data signal based on the gradation level of the first color light from the pixel data is supplied to the first liquid crystal element, and a second data signal based on the gradation level of the second color light from the pixel data is supplied to the second liquid crystal element, wherein the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the second color light When the bell changes from the first value in the first unit period to the second value in the second unit period, the second data signal in the second unit period is first corrected so that the optical response integral value of the second liquid crystal element from the first unit period to the second unit period approaches the optical response integral value of the first liquid crystal element from the first unit period to the second unit period. The first and second data signals in the second unit period are second corrected so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first and second data signals in the first unit period are third corrected so that the optical response integral values ​​of the first liquid crystal element in the first and second unit periods approach the optical response integral value of the second liquid crystal element. The third corrected first data signal is supplied to the first liquid crystal element in the first unit period, the first and third corrected second data signal is supplied to the second liquid crystal element, and the second corrected first data signal is supplied to the first liquid crystal element in the second unit period.The first and third corrected second data signals are supplied to the second liquid crystal element. [Explanation of Symbols]

[0081] 1...Projection-type display device, 100R, 100G, 100B...Liquid crystal panel, 110...Pixel circuit, 118...Pixel electrode, 120...Liquid crystal element, 20...Display control device, 21...Processing circuit, 22R, 22G, 22B...Correction circuit, 230...Optical path shift element, 2102...Light source unit.

Claims

1. A first liquid crystal panel having a first liquid crystal element, wherein a first color light is incident on the first liquid crystal element, modulated as a first image light, and emitted; A second liquid crystal panel having a second liquid crystal element, wherein a second color light different from the first color light is incident on the second liquid crystal element, modulated and emitted as a second image light, and the optical response of the second liquid crystal element is slower than the optical response of the first liquid crystal element to voltage changes, A combining optical system that combines the first image light and the second image light and emits them as combined light, An optical path shift element that shifts the optical axis of the composite light in each unit period of a frame period, which includes a first unit period that is temporally earlier and a second unit period that is temporally later, A display control device that controls the first liquid crystal panel, the second liquid crystal panel, and the optical path shift element, Equipped with, The aforementioned display control device is In each unit period included in the aforementioned frame period, a first data signal based on the gradation level of the first color light is supplied to the first liquid crystal element from the pixel data, and a second data signal based on the gradation level of the second color light is supplied to the second liquid crystal element from the pixel data. When the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the second color light changes from a first value in the first unit period to a second value in the second unit period, The second data signal in the second unit period is first corrected so that the integral value of the optical response of the second liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first and second data signals in the second unit period are given a second correction so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first data signal and the second data signal in the first unit period are subjected to a third correction so that the optical response integral value of the first liquid crystal element and the optical response integral value of the second liquid crystal element in the first unit period and the second unit period are brought closer together. Projection type display device.

2. A third liquid crystal panel comprising a third liquid crystal element, wherein a third color of light is incident on the third liquid crystal element, modulated and emitted as a third image light, and the optical response of the third liquid crystal element is slower than the optical response of the first liquid crystal element to voltage changes, The aforementioned composite optical system is In addition to the first and second image light, the third image light is combined, The aforementioned display control device is During each of the aforementioned unit periods, a third data signal based on the gradation level of the third color light is supplied to the third liquid crystal element from the pixel data. When the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the third color light changes from a first value in the first unit period to a second value in the second unit period, The third data signal in the second unit period is first corrected so that the integral value of the optical response of the third liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first data signal and the third data signal in the second unit period are given a second correction so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first data signal and the third data signal in the first unit period are subjected to a third correction so that the optical response integral value of the first liquid crystal element in the first unit period and the optical response integral value of the third liquid crystal element in the second unit period are close to each other. The projection display device according to claim 1.

3. The optical path shift element is The amount by which the optical axis is shifted from the first unit period to the second unit period is the distance of half a pixel of the pitch in the panel pixels projected by the composite light. The projection display device according to claim 1.

4. The optical path shift element is The amount by which the optical axis is shifted from the first unit period to the second unit period is a distance exceeding one pixel of the pitch in the panel pixels projected by the composite light. The projection display device according to claim 1.

5. A first liquid crystal panel having a first liquid crystal element, wherein a first color light is incident on the first liquid crystal element, modulated as a first image light, and emitted; A second liquid crystal panel having a second liquid crystal element, wherein a second color light different from the first color light is incident on the second liquid crystal element, modulated and emitted as a second image light, and the optical response of the second liquid crystal element is slower than the optical response of the first liquid crystal element to voltage changes, A combining optical system that combines the first image light and the second image light and emits them as combined light, An optical path shift element that shifts the optical axis of the composite light in each unit period of a frame period, which includes a first unit period that is temporally earlier and a second unit period that is temporally later, Equipped with, In each unit period included in the aforementioned frame period, a first data signal based on the gradation level of the first color light is supplied to the first liquid crystal element from the pixel data, and a second data signal based on the gradation level of the second color light is supplied to the second liquid crystal element from the pixel data. A method for controlling a projection display device, When the gradation level of the first color light changes from a first value in the first unit period to a second value in the second unit period, and the gradation level of the second color light changes from a first value in the first unit period to a second value in the second unit period, The second data signal in the second unit period is first corrected so that the integral value of the optical response of the second liquid crystal element from the first unit period to the second unit period approaches the integral value of the optical response of the first liquid crystal element from the first unit period to the second unit period. The first and second data signals in the second unit period are given a second correction so that the optical response in the second unit period is a larger change than the change from the first value to the second value. The first data signal and the second data signal in the first unit period are subjected to a third correction so that the optical response integral value of the first liquid crystal element and the optical response integral value of the second liquid crystal element in the first unit period and the second unit period are close to each other. In the aforementioned first unit period, The third corrected first data signal is supplied to the first liquid crystal element. The first and third corrected second data signals are supplied to the second liquid crystal element. During the second unit period, The second corrected first data signal is supplied to the first liquid crystal element. The first and third corrected second data signals are supplied to the second liquid crystal element. A method for controlling a projection-type display device.

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