Projection type display device

Abstract

Provided is a projection-type display device. The purpose of the present invention is to suppress a reduction in display quality caused by poor orientation when a projection position is shifted by an optical path shift element. A liquid crystal display device includes: a liquid crystal panel having panel pixels; an optical path shift element that shifts the projection position of the projection pixel, for example, for each of four unit periods; and a display control circuit that controls the liquid crystal panel and the optical path shift element. The display control circuit supplies a data signal corresponding to a gradation level specified by video pixel data constituting video data to the panel pixels for each unit period, and controls a projection position for each unit period with respect to an optical path shift element, the optical path shift element being configured to shift the projection position for each unit period, and the optical path shift element being configured to shift the projection position for each unit period. The projection position is shifted to a target projection position as a target after crossing the target projection position.

Description

Technical Field

[0001] The present invention relates to a projection display device. Background Art

[0002] In a liquid crystal projector using a liquid crystal panel, in order to approximately improve the resolution, a technique is known in which a light path shifting element is used to shift the projection position of panel pixels projected onto a screen or the like (for example, refer to Patent Document 1). Specifically, this technique is as follows: One frame period is divided into a plurality of unit periods, and the projection position is shifted in a different manner for each unit period. By this technique, it is possible to make a user feel as if more pixels than the number of panel pixels of the liquid crystal panel are projected.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-39995

[0004] In recent years, with the development of miniaturization and high definition of liquid crystal panels, when the gap between pixel electrodes becomes narrow, due to the electric field generated between adjacent pixel electrodes, the alignment of liquid crystals deteriorates, which is visually recognized as a display defect.

[0005] When the projection position is shifted using a light path shifting element, such a display defect caused by alignment deterioration is elongated in the shifting direction and visually recognized, so there is a problem that the reduction in display quality becomes significant. Summary of the Invention

[0006] In order to solve the above problems, a projection display device according to one aspect of the present disclosure includes: a liquid crystal panel having panel pixels; a light path shifting element that shifts the light path of projection light so that the projection position of projection pixels displayed using the projection light changes for each unit period, where each unit period is each unit period from the first unit period to the k-th unit period included in one frame period, and k is an integer of 2 or more; and a display control circuit that controls the liquid crystal panel and the light path shifting element. The display control circuit supplies a data signal corresponding to the gray level specified by the image pixel data constituting the image data to the panel pixels for each unit period, and controls the projection position for each unit period for the light path shifting element. The light path shifting element shifts the projection position to the target projection position after passing the target projection position for each unit period. Brief Description of the Drawings

[0007] Figure 1 It is a diagram showing a projection display device according to the first embodiment.

[0008] Figure 2 It is a block diagram showing the structure of a projection display device.

[0009] Figure 3 It is a perspective view showing the structure of a liquid crystal panel in a projection display device.

[0010] Figure 4 It is a cross-sectional view showing the structure of a liquid crystal panel.

[0011] Figure 5 It is a block diagram showing the electrical structure of a liquid crystal panel.

[0012] Figure 6 It is a diagram showing the structure of a pixel circuit in a liquid crystal panel.

[0013] Figure 7 It is a diagram showing the relationship between one frame period and a unit period in a projection display device.

[0014] Figure 8 It is a diagram showing the image pixels represented by one panel pixel during one frame period.

[0015] Figure 9 It is a diagram showing the locus of the projection position based on an optical path shifting element in the first embodiment.

[0016] Figure 10 It is a diagram showing the locus of the projection position based on an optical path shifting element in a comparative example.

[0017] Figure 11 It is a diagram showing the control content for an optical path shifting element and a light source unit within one frame period.

[0018] Figure 12 It is a diagram showing the relationship between image pixels, panel pixels, and projection positions during one frame period in a projection display device.

[0019] Figure 13 It is a diagram showing an example of the arrangement in image pixels.

[0020] Figure 14 It is a diagram showing the generation state of domains.

[0021] Figure 15 It is a diagram showing an example of the display based on panel pixels that is actually visually confirmed.

[0022] Figure 16 It is a diagram for explaining the display visually confirmed in a comparative example.

[0023] Figure 17 It is a diagram for explaining the display visually confirmed in the first embodiment.

[0024] Figure 18 This is a diagram showing the trajectory of the projection position based on the optical path shifting element in the second embodiment.

[0025] Figure 19 This is a diagram showing the trajectory of the projection position based on the optical path shifting element in the third embodiment.

[0026] Reference Numeral Explanation

[0027] 1: Projection display device; 100R, 100G, 100B: Liquid crystal panels; 110: Pixel circuit; 118: Pixel electrode; 120: Liquid crystal element; 20: Display control circuit; 21: Processing circuit; 22R, 22G, 22B: Conversion circuits; 230: Optical path shifting element; 2102: Light source unit. Detailed Embodiment

[0028] Hereinafter, the projection display device according to the embodiment will be described with reference to the drawings. In addition, in each drawing, the dimensions and scales of each part are appropriately different from the actual dimensions and scales. In addition, the following-described embodiments are preferred specific examples, and thus various technically preferred limitations are added. However, as long as there is no description specifically limiting the gist of the present disclosure in the following description, the scope of the present disclosure is not limited to these embodiments.

[0029] Figure 1 This is a diagram showing the optical structure of the projection display device 1 according to the embodiment. As shown in the figure, the projection display device 1 includes liquid crystal panels 100R, 100G, and 100B. Inside the projection display device 1, a light source unit 2102 composed of a white light source such as a laser is provided. The projection light emitted from the light source unit 2102 is separated into three primary colors of red (R), green (G), and blue (B) by three reflecting mirrors 2106 and two dichroic mirrors 2108 arranged inside. Among them, R light is incident on the liquid crystal panel 100R, G light is incident on the liquid crystal panel 100G, and B light is incident on the liquid crystal panel 100B.

[0030] In addition, since the optical path of B is longer than the optical paths of R and G, it is necessary to prevent losses in the optical path of B. Therefore, a relay lens system 2121 composed of an incident lens 2122, a relay lens 2123, and an exit lens 2124 is provided on the optical path of B.

[0031] The liquid crystal panel 100R has a plurality of pixel circuits as described later. Each of the plurality of pixel circuits includes a liquid crystal element. The liquid crystal element of the liquid crystal panel 100R is driven based on the data signal corresponding to R and becomes a transmittance corresponding to the voltage of the data signal.

[0032] Therefore, by independently controlling the transmittance of the liquid crystal elements based on the data signals 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.

[0033] 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 light of R and B is refracted by 90 degrees. On the other hand, the light of G travels straight. Therefore, the dichroic prism 2112 synthesizes the images of each color. The synthesized image based on the dichroic prism 2112 is incident on the projection lens 2114 via the optical path shifting element 230.

[0034] The projection lens 2114 magnifies and projects the synthesized image that has passed through the optical path shifting element 230 onto the screen Scr as the projection surface.

[0035] The optical path shifting element 230 shifts the optical path of the light (projection light) emitted from the dichroic prism 2112. Specifically, the optical path shifting element 230 shifts the position of the projected synthesized image in the left - right direction and / or the up - down direction with respect to the projection surface.

[0036] In addition, the transmitted images based on the liquid crystal panels 100R and 100B are projected after being reflected by the dichroic prism 2112, while the transmitted image based on the liquid crystal panel 100G is projected straight. Therefore, the transmitted images based on the liquid crystal panels 100R and 100B are in a left - right reversed relationship with respect to the transmitted image of the liquid crystal panel 100G.

[0037] Figure 2 FIG. is a block diagram showing the electrical structure of the projection display device 1. As shown in the figure, the projection display device 1 includes a display control circuit 20, liquid crystal panels 100R, 100G, and 100B, an optical path shifting element 230, and a light source unit 2102.

[0038] Video data Vid_in is supplied from an upper device such as a host device (not shown) in synchronization with the synchronization signal Sync. The video data Vid_in designates the gray levels of the pixels during one frame period of the image, for example, 8 - bit for each RGB.

[0039] In addition, the pixels of the image specified by the video data Vid_in are marked as video pixels, and the data specifying the gray levels of the video pixels are marked as video pixel data. However, there are times when the video pixels and the video pixel data are not particularly distinguished in the description. Further, the pixels of the image before or after synthesis based on the liquid crystal panels 100R, 100G, or 100B are marked as panel pixels. The panel pixels shifted by the optical path shifting element 230 and projected onto the screen Scr are marked as projected pixels, and the position where the panel pixels are projected is marked as the projection position.

[0040] In the liquid crystal panels 100R, 100G, and 100B, the panel pixels are arranged in a matrix pattern when viewed from above. In the embodiment, the arrangement of the video pixels specified by the video data Vid_in is, for example, twice as large in the vertical direction and twice as large in the horizontal direction as the arrangement of the panel pixels based on the liquid crystal panels 100R, 100G, or 100B.

[0041] In the embodiment, the color image projected onto the screen Scr is represented by synthesizing 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 sub-pixel based on the liquid crystal panel 100R, a green sub-pixel based on the liquid crystal panel 100G, and a blue sub-pixel based on the liquid crystal panel 100B. However, regarding the sub-pixels in the liquid crystal panels 100R, 100G, and 100B, in cases where a specific color is not required or only brightness and darkness are the issues, etc., it is not necessary to specifically refer to them as sub-pixels. Therefore, in this specification, the display unit in the liquid crystal panels 100R, 100G, and 100B is also referred to as a panel pixel.

[0042] The synchronization signal Sync includes a vertical synchronization signal indicating the start of the vertical scan of the video data Vid_in, a horizontal synchronization signal indicating the start of the horizontal scan, and a clock signal representing the timing of the amount of one video pixel in the video data Vid_in.

[0043] The display control circuit 20 includes a processing circuit 21 and conversion circuits 22R, 22G, and 22B.

[0044] Based on the synchronization signal Sync, the processing circuit 21 controls the conversion circuits 22R, 22G, 22B, the liquid crystal panels 100R, 100G, 100B, the optical path shifting element 230, and the light source unit 2102 during each of the unit periods f1 to f4 described later.

[0045] The optical path shifting element 230 shifts the projection position according to the control signals P_x and P_y output from the processing circuit 21.

[0046] The light source unit 2102 changes the intensity of the emitted light in accordance with the control signal Lgt output from the processing circuit 21.

[0047] In the video data Vid_in supplied from the host device, the R component is labeled as video data Va_R, the G component is labeled as video data Va_G, and the B component is labeled as video data Va_B. After temporarily storing in the internal buffer of the conversion circuit 22R the amount of video data Va_R supplied from the host device for one or more frames, the conversion circuit 22R reads out the video data corresponding to the unit period, converts it into a data signal Vid_R of an analog voltage, and supplies it to the liquid crystal panel 100R. The conversion circuits 22G and 22B are the same as the conversion circuit 22R except that the color components of the video data to be converted are different. That is, the conversion circuit 22G converts the video data corresponding to the unit period of the video data Va_G into a data signal Vid_G of an analog voltage and supplies it to the liquid crystal panel 100G, and the conversion circuit 22B converts the video data corresponding to the unit period of the video data Va_B into a data signal Vid_B of an analog voltage and supplies it to the liquid crystal panel 100B.

[0048] Next, the liquid crystal panels 100R, 100G, and 100B will be described. Regarding the liquid crystal panels 100R, 100G, and 100B, only the color of the incident light, i.e., the wavelength, is different, and they are common in structure. Therefore, for the liquid crystal panels 100R, 100G, and 100B, a general description will be given as the liquid crystal panel 100 without specifying the color.

[0049] Figure 3 is a perspective view showing the liquid crystal panel 100, Figure 4 is a cross-sectional view obtained by cutting along the H-h line in Figure 3 in.

[0050] As shown in these figures, in the liquid crystal panel 100, the element substrate 100a provided with the pixel electrode 118 and the counter substrate 100b provided with the common electrode 108 maintain a certain gap, and are bonded using a sealing material 90 in such a manner that the electrode formation surfaces face each other, and liquid crystal 105 is sealed in this gap.

[0051] As the element substrate 100a and the counter substrate 100b, substrates having light transmissivity such as glass and quartz are used respectively. As Figure 3 shown, one side of the element substrate 100a protrudes from the counter substrate 100b. In this protruding area, a plurality of terminals 106 are provided horizontally in the figure. One end of an FPC (Flexible Printed Circuits) substrate (not shown) is connected to the plurality of terminals 106. In addition, the other end of this FPC substrate is connected to the display control circuit 20 and is supplied with the above various signals.

[0052] On the surface of the element substrate 100a facing the counter substrate 100b, the pixel electrode 118 is formed, for example, by patterning a conductive layer having transparency such as ITO (Indium Tin Oxide).

[0053] In addition, although not particularly illustrated, on the counter substrate 100b (or the element substrate 100a), a microlens is provided for each panel pixel in order to efficiently send a large amount of light into the opening portion that becomes the panel pixel. With this structure, the light bounced by the light-shielding portion is sent into the opening portion of the microlens, so that the utilization efficiency of light can be improved.

[0054] Figure 5 It is a block diagram showing the electrical structure of the liquid crystal panel 100. In the liquid crystal panel 100, a scan line driving circuit 130 and a data line driving circuit 140 are provided at the periphery of the display area 10.

[0055] In the display area 10 of the liquid crystal panel 100, the pixel circuits 110 are arranged in a matrix. Specifically, in the display area 10, a plurality of scan lines 12 are provided extending horizontally in the figure, and in addition, a plurality of data lines 14 extend vertically and are provided so as to be electrically insulated from each other with respect to the scan lines 12. Moreover, corresponding to the intersections of the plurality of scan lines 12 and the plurality of data lines 14, the pixel circuits 110 are arranged in a matrix.

[0056] When the number of scan lines 12 is set to m and the number of data lines 14 is set to n, the pixel circuits 110 are arranged in a matrix in a vertical m-row × horizontal n-column manner. Both m and n are integers of 2 or more. In the scan lines 12 and the pixel circuits 110, in order to distinguish the rows of the matrix, they are sometimes referred to as the 1st, 2nd, 3rd,..., (m - 1)th, and mth rows in order from the top in the figure. Similarly, in the data lines 14 and the pixel circuits 110, in order to distinguish the columns of the matrix, they are sometimes referred to as the 1st, 2nd, 3rd,..., (n - 1)th, and nth columns in order from the left in the figure.

[0057] The scan line driving circuit 130 sequentially selects the scan lines 12 one by one, for example, in the order of the 1st, 2nd, 3rd,..., mth rows, according to the control performed by the display control circuit 20, and sets the scan signal for the selected scan line 12 to the H level. In addition, the scan line driving circuit 130 sets the scan signals for the scan lines 12 other than the selected scan line 12 to the L level.

[0058] The data line driving circuit 140 latches the data signal supplied from the corresponding color circuit among the conversion circuits 22R, 22G, or 22B for one row, and outputs it to the pixel circuit 110 located on the scan line 12 via the data line 14 during the period when the scan signal for the scan line 12 becomes the H level.

[0059] Figure 6 FIG. 1 is an equivalent circuit diagram showing a total of four pixel circuits 110 arranged in two vertical rows and two horizontal columns corresponding to the intersections of two adjacent scan lines 12 and two adjacent data lines 14.

[0060] 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. On the other hand, the source node of the transistor 116 is connected to the data line 14, and the drain node of the transistor 116 is connected to a pixel electrode 118 which is square-shaped in plan view.

[0061] A common electrode 108 is provided for all pixels in a manner opposed to the pixel electrode 118. A voltage LCcom is applied to the common electrode 108. Further, the liquid crystal 105 is sandwiched between the pixel electrode 118 and the common electrode 108 as described above. Thus, for each pixel circuit 110, a liquid crystal element 120 is formed in which the liquid crystal 105 is sandwiched between the pixel electrode 118 and the common electrode 108.

[0062] In addition, 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 a capacitor line 107. A voltage that is constant over time is applied to the capacitor line 107, for example, the same voltage LCcom as the voltage applied to the common electrode 108. Since the pixel circuits 110 are arranged in a matrix in the extending direction of the scan lines 12 (i.e., horizontally) and in the extending direction of the data lines 14 (i.e., vertically), the pixel electrodes 118 included in the pixel circuits 110 are also arranged both vertically and horizontally.

[0063] In the scan line 12 in which the scan signal is at the H level, the transistor 116 of the pixel circuit 110 provided corresponding to the scan line 12 is turned on. Due to the on-state of the transistor 116, the data line 14 and the pixel electrode 118 are electrically connected. Therefore, the data signal supplied to the data line 14 reaches the pixel electrode 118 via the turned-on transistor 116. When the scan line 12 is at the L level, the transistor 116 is turned off, but the voltage of the data signal that has reached the pixel electrode 118 is held by the capacitance of the liquid crystal element 120 and the storage capacitor 109.

[0064] As is well known, in the liquid crystal element 120, the orientation of the liquid crystal molecules changes according 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.

[0065] In addition, in the liquid crystal element 120, the region that functions as a panel pixel, that is, the region where the transmittance corresponds to the effective value of the voltage, is the region where the pixel electrode 118 overlaps with the common electrode 108 when the element substrate 100a and the counter substrate 100b are viewed from above. Since the pixel electrode 118 is square when viewed from above, the shape of the pixels of the liquid crystal panel 100 is also square.

[0066] In addition, in the present embodiment, the liquid crystal 105 is a VA (Vertical Alignment) mode, which is a normally black mode in which the transmittance is the lowest when the applied voltage applied to the liquid crystal element 120 is zero, and the transmittance increases as the applied voltage increases.

[0067] The operation of supplying the data signal to the pixel electrode 118 of the liquid crystal element 120 is performed for each horizontal scan period in the order of the first, second, third,..., m-th rows during the effective vertical scan periods of the unit periods f1 to f4. As a result, the liquid crystal elements 120 of the pixel circuits 110 arranged in m rows and n columns respectively hold the voltages corresponding to the data signals, and each liquid crystal element 120 becomes the target transmittance. Through the liquid crystal elements 120 arranged in m rows and n columns, a transmitted image of the corresponding color is generated.

[0068] In this way, the generation of the transmitted image is performed for each RGB, and the color image after synthesizing RGB is projected onto the screen Scr.

[0069] The data signals Vid_R, Vid_G, and Vid_B output corresponding to a certain unit period correspond to the RGB components of the video data corresponding to the unit period. Therefore, the color composite image corresponding to the projection position during the unit period is projected at the projection position.

[0070] Figure 7 FIG. is a diagram showing the relationship between one frame period and the unit period in the projection type display device 1 according to the embodiment. As shown in the figure, in the present embodiment, one frame (1F) period is divided into four unit periods. For the sake of easy distinction of the four unit periods, as labels, f1, f2, f3, and f4 are given in chronological order.

[0071] In addition, one frame period refers to the period for supplying one frame amount of the image represented by the video data Vid_in from the upper device. When the frequency of the vertical synchronization signal included in the synchronization signal Sync is 60 Hz, it is one cycle, that is, 16.7 milliseconds. In this case, the length of each unit period is 1 / 4 of the length of one frame period, that is, 4.17 milliseconds.

[0072] In the present embodiment, the projection position is changed for each unit period f1 to f4, and at each projection position, the user visually confirms an image in which the image resolution specified by the video data Vid_in is reduced to 1 / 4. In other words, an image having a resolution four times that of the combined image of the liquid crystal panels 100R, 100G, and 100B is approximately visually confirmed by the user.

[0073] The unit period f1 is divided into an effective vertical scanning period f1a and a vertical retrace period f1b. Among them, the effective vertical scanning period f1a is a period during which the scanning lines 12 from the first row to the m-th row are sequentially horizontally scanned, and the vertical retrace period f1b is a preparation period for horizontally scanning from the final m-th row to the first row, and is a period obtained by removing the effective vertical scanning period f1a from the unit period f1.

[0074] Similarly, the unit period f2 is divided into an effective vertical scanning period f2a and a vertical retrace period f2b, the unit period f3 is divided into an effective vertical scanning period f3a and a vertical retrace period f3b, and the unit period f4 is divided into an effective vertical scanning period f4a and a vertical retrace period f4b.

[0075] Figure 8 It is a diagram showing the correspondence between video pixels and panel pixels.

[0076] In the figure, the left column is a diagram showing a part of the arrangement of video pixels represented by the video data Vid_in, and the right column is a diagram showing the arrangement corresponding to the arrangement of the video pixels in the left column among the panel pixels.

[0077] In addition, labels are respectively assigned to the video pixels in the left column and the panel pixels in the right column for distinction.

[0078] If the labels are described in detail, the pixels in which the last two digits in the label of the video pixel are the same as the last two digits in the label of the panel pixel correspond to each other. For example, the video pixels A11, B11, C11, and D11 correspond to the panel pixel p11.

[0079] In addition, the first letters A, B, C, and D in the label of the video pixel mean that they are sequentially displayed in the unit periods f1, f2, f3, and f4 in the corresponding panel pixel. For example, the video pixel D11 is displayed by the panel pixel p11 within the unit period f4. In other words, the panel pixel p11 sequentially displays the video pixels A11, B11, C11, and D11 as shown by the arrows within the unit periods f1, f2, f3, and f4. <{}

[0080] When a certain image pixel is "represented" by a panel pixel, it means that the liquid crystal element 120 of the panel pixel has a transmittance corresponding to the gray level (image pixel data) of the image pixel.

[0081] Figure 9 This is a diagram showing the trajectory of the projection position shifted by the optical path shifting element 230 in the first embodiment. For convenience, the projection position Ps1a within the effective vertical scanning period f1a of the unit period f1 is used as a reference.

[0082] In this embodiment, the projection position stays at the reference position Ps1a within the effective vertical scanning period f1a, starts to shift upward with the start of the vertical retrace period f1b, and reaches the position Ps1b which is one pixel away from the panel pixel from the position Ps1a. After that, before the start of the effective vertical scanning period f2a, the projection position reverses downward from the position Ps1b and shifts to the position Ps2a which is 0.5 pixels away from the panel pixel from the position Ps1b.

[0083] The projection position stays at the position Ps2a within the effective vertical scanning period f2a, starts to shift rightward with the start of the vertical retrace period f2b, and reaches the position Ps2b which is one pixel away from the panel pixel from the position Ps2a. After that, before the start of the effective vertical scanning period f3a, the projection position reverses leftward from the position Ps2b and shifts to the position Ps3a which is 0.5 pixels away from the panel pixel from the position Ps2b.

[0084] The projection position stays at the position Ps3a within the effective vertical scanning period f3a, starts to shift downward with the start of the vertical retrace period f3b, and reaches the position Ps3b which is one pixel away from the panel pixel from the position Ps3a. After that, before the start of the effective vertical scanning period f4a, the projection position reverses upward from the position Ps3b and shifts to the position Ps4a which is 0.5 pixels away from the panel pixel from the position Ps3b.

[0085] The projection position stays at the position Ps4a within the effective vertical scanning period f4a, starts to shift leftward with the start of the vertical retrace period f4b, and reaches the position Ps4b which is one pixel away from the panel pixel from the position Ps4a. After that, before the start of the effective vertical scanning period f1a, the projection position reverses rightward from the position Ps4b and returns to the position Ps1a which is 0.5 pixels away from the panel pixel from the position Ps4b.

[0086] Figure 10This is a diagram showing the locus of the projection position shifted by the optical path shifting element 230 in a comparative example relative to the first embodiment. In the comparative example, the projection position stays at the reference position Ps1a during the effective vertical scanning period f1a, and is shifted to the position Ps2a before the start of the effective vertical scanning period f2a. The projection position stays at the position Ps2a during the effective vertical scanning period f2a, and is shifted to the position Ps3a before the start of the effective vertical scanning period f3a, and proceeds similarly hereinafter, and returns to the position Ps1a before the start of the effective vertical scanning period f1a.

[0087] That is, in the comparative example, the projection position, for example, directly shifts from the position Ps1a to the position Ps2a from the end of the effective vertical scanning period f1a to before the start of the effective vertical scanning period f2a, without following an extra path such as the position Ps1b.

[0088] In other words, in the first embodiment, it is configured relative to the comparative example that, for example, from the end of the effective vertical scanning period f1a to before the start of the effective vertical scanning period f2a, an overshoot occurs where the projection position exceeds the position Ps2a from the position Ps1a and then returns to the position Ps2a.

[0089] In addition, the positions Ps1a, Ps2a, Ps3a, and Ps4a are the target projection positions during the effective vertical scanning periods f1a, f2a, f3a, and f4a in sequence.

[0090] Figure 11 This is a diagram showing Figure 10 an example of the waveforms of the control signals P_x, P_y, and Lgt for depicting the locus of the projection position shown.

[0091] The optical path shifting element 230 shifts the projection position in the left - right direction and / or the up - down direction relative to the projection surface. Specifically, the optical path shifting element 230 shifts the projection position to the right by a distance corresponding to the amount of increase in the level of the control signal P_x, and shifts the projection position to the left by a distance corresponding to the amount of decrease in the level of the control signal P_x. In addition, the optical path shifting element 230 shifts the projection position upward by a distance corresponding to the amount of increase in the level of the control signal P_y, and shifts the projection position downward by a distance corresponding to the amount of decrease in the level of the control signal P_y. Further, the optical path shifting element 230 sets the projection position to the reference position Ps1a when the levels of the control signals P_x and P_y are both 0, and sets the shift distance of the projection position to 0.5 pixel amount in the panel pixels when the levels of the control signals P_x and P_y change by A.

[0092] For example, if the level of the control signal P_x is 0 and the level of the control signal P_y is +2A, the optical path shifting element 230 shifts the projection position to a position Ps1b which is one pixel above the panel pixel from the reference position Ps1a.

[0093] If the level of the control signal Lgt is high, the light source unit 2102 emits light with a relatively high intensity. If the level of the control signal Lgt is low, the light source unit 2102 emits light with a relatively low intensity. Specifically, when the level of the control signal Lgt is 1.0c as a standard, if the level of the control signal Lgt is 1.2c, the light source unit 2102 emits light with an intensity higher than the standard.

[0094] Figure 12 It is a diagram showing the relationship among the image pixels, panel pixels, and projection positions within one frame period.

[0095] During the effective vertical scanning period f1a of the unit period f1, the projection position is the reference position Ps1a. The panel pixels p11, p12, p13, p21, p22, and p23 sequentially display the shaded image pixels A11, A12, A13, A21, A22, and A23 at the position Ps1a. After that, the projection position shifts to the position Ps2a via the position Ps1b during the vertical retrace period f1b.

[0096] During the effective vertical scanning period f2a of the unit period f2, the panel pixels p11, p12, p13, p21, p22, and p23 sequentially display the shaded image pixels B11, B12, B13, B21, B22, and B23 at the position Ps2a. After that, the projection position shifts to the position Ps3a via the position Ps2b during the vertical retrace period f2b.

[0097] During the effective vertical scanning period f3a of the unit period f3, the panel pixels p11, p12, p13, p21, p22, and p23 sequentially display the shaded image pixels C11, C12, C13, C21, C22, and C23 at the position Ps3a. After that, the projection position shifts to the position Ps4a via the position Ps3b during the vertical retrace period f3b.

[0098] During the effective vertical scanning period f4a of the unit period f4, the panel pixels p11, p12, p13, p21, p22, and p23 sequentially display the shaded image pixels D11, D12, D13, D21, D22, and D23 at the position Ps4a. After that, the projection position returns to the position Ps1a via the position Ps4b during the vertical retrace period f4b.

[0099] In the liquid crystal panel 100, the transmittance of the panel pixels is determined by the alignment (tilt angle) of liquid crystal molecules as follows, that is, the alignment (tilt angle) of liquid crystal molecules corresponding to the magnitude of the voltage difference determined by the pixel electrode 118 and the common electrode 108, that is, the magnitude of the electric field in the direction perpendicular to the substrate surface (longitudinal electric field).

[0100] However, when a dark panel pixel with a low transmittance is adjacent to a bright panel pixel with a high transmittance, the voltage difference between the pixel electrodes 118 becomes larger, and in a region including the boundary of two pixels when viewed from above, an electric field in the direction along the substrate surface (transverse electric field) is generated.

[0101] Therefore, the alignment of liquid crystal molecules determined only by the longitudinal electric field is disturbed due to the influence of the transverse electric field, and as a result, alignment defects, so-called domains, are generated. Generally, the larger the voltage difference between the pixel electrodes 118, that is, the larger the difference in gray levels, the greater the degree of alignment defects near the boundary of two adjacent panel pixels.

[0102] In a region where the alignment of liquid crystal molecules is disturbed, if it is in the normally black mode, the transmittance decreases and thus it becomes darker. However, since the dark panel pixel is originally in a dark state, even if the alignment of liquid crystal molecules is disturbed, it is difficult to be visually recognized as a reduction in display quality. In other words, although alignment defects generated due to the adjacency of a bright panel pixel and a dark panel pixel occur in both the dark panel pixel and the bright panel pixel across the boundary, the reduction in display quality accompanying the alignment defects is visually recognized as a local reduction in transmittance in the bright panel pixel.

[0103] Such alignment defects will be described using a specific example.

[0104] Figure 13 is a diagram showing an example of the arrangement of image pixels where alignment defects are likely to be obvious, Figure 14 is a diagram showing the relationship between the panel pixels and the projection positions representing such image pixels.

[0105] In Figure 13 as an example, an arrangement in which a black image pixel with the lowest gray level is adjacent to a white image pixel with the highest gray level is shown. Specifically, it is an example in which the black region is composed of image pixels B11, C11, B12, C12, B13, C13, A11, D11, A12, D12, A13, and D13, and the white region is composed of image pixels B21, C21, B22, C22, B23, C23, A21, D21, A22, D22, A23, and D23.

[0106] When the panel pixels represent such image pixels, as Figure 14As shown, within each unit period f1 to f4, the panel pixels p11, p12, p13 become dark panel pixels, and the panel pixels p21, p22, p23 become bright panel pixels. Therefore, alignment defects occur in the regions Dm sandwiching the boundary, that is, in both these dark panel pixels and bright panel pixels.

[0107] However, the reduction in display quality accompanying the alignment defects is not obvious in the dark panel pixels, and as shown by the shading in the figure, it is visually confirmed in the bright panel pixels p21, p22, p23.

[0108] In addition, the width of the region shown by the shading, that is, the length in the direction perpendicular to the boundary direction between the bright panel pixels and the dark panel pixels, varies depending on the magnitude of the lateral electric field, the duration of the lateral electric field, etc. However, in the figure, for convenience, it is set to the amount of 0.5 pixels in the panel pixels.

[0109] Figure 14 L0 to L7 in [reference] represent the absolute coordinate system in the vertical direction when the projection positions of the panel pixels are shifted by the optical path shifting element 230, and the interval is the amount of 0.5 pixels of the panel pixels. For example, when it is the reference position Ps1a during the effective vertical scan period f1a, it means that the upper edges of the panel pixels p11, p12, p13 are located at the coordinate L2. In addition, the absolute coordinate system refers to the coordinate system in the projection plane that is independent of the shift of the projection position.

[0110] Figure 15 is a diagram showing the actual display state in the panel pixels. In addition, this display state shows the state of the image pixel displaying white with the highest gray level. In addition, this display state fixes the projection position for the sake of explanation.

[0111] In the liquid crystal panel 100, as described above, in order to improve the light utilization efficiency, a microlens is provided for each panel pixel. Therefore, the brightness of the projected panel pixels is uneven. Actually, as shown in the left column of [reference], it becomes brighter near the center and darker as it moves from near the center towards the outside. In addition, the frame Px represents the outer edge of the panel pixel in the liquid crystal panel 100. Figure 15 In the right column of [reference], for the sake of explanation, the brightness of the white display state in the panel pixel is expressed by the line density. The denser the line density, the darker the state shown.

[0112] For the sake of explanation, Figure 15 In the comparative example, it is a structure in which the overshoot of the projection position is not performed. Therefore, in the comparative example, as shown in [reference],

[0113] In the comparative example, it is a structure in which the overshoot of the projection position is not performed. Therefore, in the comparative example, as shown in [reference], Figure 10As shown, the projection positions are shifted in the order of position Ps1a during unit period f1, position Ps2a during unit period f2, position Ps3a during unit period f3, and position Ps4a during unit period f4.

[0114] Here, in Figure 14 the shaded area in the region Dm where orientation defects occur, that is, the area where the display quality deteriorates, is located as follows. Specifically, the shaded area is in the region of coordinates L4 - L5 during unit period f1, in the region of coordinates L3 - L4 during unit period f2, in the region of coordinates L3 - L4 during unit period f3, and in the region of coordinates L4 - L5 during unit period f4. In other words, in the region of coordinates L4 - L5, the display quality deteriorates during two unit periods, and it is a bright panel pixel during the remaining two unit periods, so it is relatively easy to visually confirm this deterioration of the display quality.

[0115] In addition, in the region of coordinates L3 - L4, the display quality deteriorates during two unit periods, but it is a dark panel pixel during the remaining two unit periods. Therefore, even if the display quality deteriorates, it will be buried by the dark panel pixels and is relatively difficult to be visually confirmed as a deterioration of the display quality.

[0116] Figure 16 This situation is shown. Specifically, region K is the region that becomes a dark panel pixel due to black image pixels. Region Dma is the region where, although orientation defects occur, it is difficult to visually confirm the deterioration of the display quality due to dark panel pixels. Region Dmb is the region where it is easy to visually confirm the deterioration of the display quality caused by the occurrence of orientation defects.

[0117] Relative to such a comparative example, in the first embodiment, the projection positions during the effective vertical scanning periods f1a, f2a, f3a, and f4a are the same as those in the comparative example, but during the vertical retrace periods f1b, f2b, f3b, and f4b, the projection positions shift along a trajectory of overshoot.

[0118] Therefore, in Figure 14 the shaded area in the region Dm where orientation defects occur and the display quality deteriorates stays particularly in the region of coordinates L4 - L5 during the effective vertical scanning period f1a, but during the vertical retrace period f1b, due to the overshoot of the trajectory, it is pushed to a position above the region of coordinates L4 - L5 in the figure. Therefore, the period during which the shaded area stays in the region of coordinates L4 - L5 is shorter than that in the comparative example due to the overshoot, so the shaded area is visually recognized as brighter than the comparative example.

[0119] Figure 17This situation is shown. Specifically, the area K is the same as in the comparative example, but the areas Dma and Dmb are shaped such that they are pushed upward in the figure relative to the comparative example.

[0120] In the first embodiment, during the vertical blanking periods f1b, f2b, f3b, and f4b, the intensity of the emitted light from the light source unit 2102 is higher than the intensity of the emitted light during the effective vertical scanning periods f1a, f2a, f3a, and f4a. Therefore, it becomes brighter in a way that compensates for the phenomenon of display dimming caused by poor alignment, and thus the degradation of display quality can be made less obvious.

[0121] In addition, in this example, the case where black image pixels are arranged on the upper side and white image pixels are arranged on the lower side is described as an example. On the contrary, even when black image pixels are arranged on the lower side and white image pixels are arranged on the upper side, the degradation of display quality caused by poor alignment can be suppressed by the overshoot during the vertical blanking period f3b.

[0122] Furthermore, for example, even when black image pixels are arranged on the right side and white image pixels are arranged on the left side, the degradation of display quality caused by poor alignment can be suppressed by the overshoot during the vertical blanking period f2b. On the contrary, even when black image pixels are arranged on the left side and white image pixels are arranged on the right side, the degradation of display quality caused by poor alignment can be suppressed by the overshoot during the vertical blanking period f4b.

[0123] In addition, in the first embodiment, for example, in the shift from the projection position Ps1a during the effective vertical scanning period f1a of the unit period f1 to the projection position Ps2a during the effective vertical scanning period f2a of the next unit period f2, the position Ps1b is the one with the largest distance from the position Ps1a. Converting this largest distance, it is the amount of 1 pixel in the panel pixels. However, it is not limited to this, and this largest distance can also be longer than the amount of 1 pixel in the panel pixels.

[0124] In the first embodiment, regarding the direction of the projection position overshoot, for example, when shifting from the reference position Ps1a to the position Ps2a, it is only above the position Ps2a, but it is not limited to this. Therefore, the second and third embodiments with changed trajectories of the projection positions with overshoot are described.

[0125] Figure 18 It is a diagram showing the trajectory of the projection position in the second embodiment.

[0126] In the second embodiment, the projection position stays at the reference position Ps1a during the effective vertical scan period f1a, starts to shift upward with the start of the vertical retrace period f1b, and returns to the position Ps2a before the start of the effective vertical scan period f2a via the positions Ps2a, Ps1ba, Ps1bb, and Ps1bc. Specifically, the projection position starts to shift upward with the start of the vertical retrace period f1b, turns left at the position Ps2a, turns upward at the position Ps1ba, turns right at the position Ps1bb, turns downward at the position Ps1bc, and returns to the position Ps2a.

[0127] In addition, the distances from the position Ps2a to the position Ps1ba, from the position Ps1ba to the position Ps1bb, from the position Ps1bb to the position Ps1bc, and from the position Ps1bc to the position Ps2a are each, for example, an amount of 0.5 pixels of the panel pixels.

[0128] Similarly hereinafter, the projection position stays at the position Ps2a during the effective vertical scan period f2a, starts to shift rightward with the start of the vertical retrace period f2b, and returns to the position Ps3a before the start of the effective vertical scan period f3a via the positions Ps3a, Ps2ba, Ps2bb, and Ps2bc.

[0129] The projection position stays at the position Ps3a during the effective vertical scan period f3a, starts to shift downward with the start of the vertical retrace period f3b, and returns to the position Ps4a before the start of the effective vertical scan period f4a via the positions Ps4a, Ps3ba, Ps3bb, and Ps3bc.

[0130] The projection position stays at the position Ps4a during the effective vertical scan period f4a, starts to shift leftward with the start of the vertical retrace period f4b, and returns to the position Ps1a before the start of the effective vertical scan period f1a via the positions Ps1a, Ps4ba, Ps4bb, and Ps4bc.

[0131] In the first embodiment, it is configured that the reduction in display quality caused by the alignment defect generated when black image pixels are arranged on the upper side and white image pixels are arranged on the lower side is reduced by the overshoot above during the vertical retrace period f1b.

[0132] In contrast, in the second embodiment, the reduction in display quality caused by the alignment defect generated when black image pixels are arranged on the upper side and white image pixels are arranged on the lower side is reduced by the overshoot above during the vertical retrace periods f1b, f2b, f3b, and f4b.

[0133] On the contrary, the degradation of the display quality caused by the misalignment generated when black image pixels are arranged on the lower side and white image pixels are arranged on the upper side is reduced by the overshoot on the lower side during the vertical retrace periods f1b, f2b, f3b, and f4b.

[0134] In addition, the degradation of the display quality caused by the misalignment generated when black image pixels are arranged on the right side and white image pixels are arranged on the left side is reduced by the overshoot on the right side during the vertical retrace periods f1b, f2b, f3b, and f4b.

[0135] On the contrary, the degradation of the display quality caused by the misalignment generated when black image pixels are arranged on the left side and white image pixels are arranged on the right side is reduced by the overshoot on the left side during the vertical retrace periods f1b, f2b, f3b, and f4b.

[0136] Thus, in the second embodiment, the degradation of the display quality when black image pixels and white image pixels are arranged vertically or horizontally is reduced during each of the vertical retrace periods f1b, f2b, f3b, and f4b. Therefore, according to the second embodiment, compared with the first embodiment, the degradation of the display quality can be suppressed.

[0137] In addition, in the second embodiment, the trajectories of the overshoots are all clockwise when observed with reference to the positions Ps1a, Ps2a, Ps3a, and Ps4a, but they can also be counterclockwise. In the case where the trajectories of the overshoots are counterclockwise, for example, in the case of the overshoot during the vertical retrace period f1b, the projection position starts to shift upward from the position Ps1a with the start of the vertical retrace period f1b, passes through the positions Ps2a, Ps3a, Ps2ba, and Ps1bc, and returns to the position Ps2a before the start of the effective vertical scanning period f2a.

[0138] Figure 19 It is a diagram showing the trajectory of the projection position in the third embodiment.

[0139] In the third embodiment, the projection position stays at the position Ps1a during the effective vertical scanning period f1a, starts to shift upward with the start of the vertical retrace period f1b, crosses the position Ps2a, passes through Ps1bc, Ps1bb, and Ps1ba, and returns to the position Ps2a before the start of the effective vertical scanning period f2a. Specifically, the projection position starts to shift upward with the start of the vertical retrace period f1b, goes straight without turning at the position Ps2a, turns left at the position Ps1bc, turns downward at the position Ps1bb, turns right at the position Ps1ba, and returns to the position Ps2a.

[0140] That is, in the third embodiment, it is configured that during overshoot, the projection position directly passes through the position during the effective vertical scanning period of the next unit period and then returns to the position during the effective vertical scanning period of the next unit period in the reverse rotation direction compared to the second embodiment.

[0141] Therefore, according to the third embodiment, compared with the first embodiment, it is possible to suppress the degradation of display quality in the same manner as the second embodiment.

[0142] In addition, in the third embodiment, compared with the second embodiment, the projection position during overshoot does not turn but goes straight at positions Ps1a, Ps2a, Ps3a, and Ps4a. In other words, in the third embodiment, the optical path displacement element 230 is not required to have a high-speed response, and the number of times the projection position turns is less compared to the second embodiment, so cost reduction can be expected.

[0143] Furthermore, in the third embodiment, when observing the overshoot trajectory based on positions Ps1a, Ps2a, Ps3a, and Ps4a, it is all counterclockwise, but it can also be clockwise. In the case where the overshoot trajectory is clockwise, for example, if it is an overshoot during the vertical retrace period f1b, the projection position starts to shift upward from position Ps1a along with the start of the vertical retrace period f1b, directly passes through position Ps2a, passes through positions Ps1bc, Ps2ba, and Ps3a, and returns to position Ps2a before the start of the effective vertical scanning period f2a.

[0144] In the above-described first to third embodiments (hereinafter referred to as "embodiments, etc."), various modifications or applications can be made as follows.

[0145] In the embodiments, etc., the liquid crystal panel 100 is a transmissive type, but it can also be a reflective type.

[0146] In the embodiments, etc., it is configured to divide one frame period into four unit periods. That is, it has been described that the number k of unit periods included in one frame period is set to "4".

[0147] k is not limited to "4". Specifically, one frame period can also be composed of "2" unit periods, or can be composed of "3" or "5" or more unit periods.

[0148] In the embodiments, etc., the period of overshoot of the projection position based on the optical path displacement element 230 is not limited to the vertical retrace period. For example, regarding the period of overshoot of the projection position trajectory, it can also start from the middle of the effective vertical scanning period and extend to a part of the back end within the effective vertical scanning period, or can end in the middle of the effective vertical scanning period and extend to a part of the front end within the effective vertical scanning period.

[0149] Regarding the period during which the light emission amount of the light source unit 2102 is larger than the standard, a structure in which it preferably coincides with the period during which the projection position overshoots is preferred.

[0150] According to the methods exemplified above, for example, the following methods are grasped.

[0151] A projection display device according to a first aspect includes: a liquid crystal panel having panel pixels; an optical path shift element that shifts the projection position of projection pixels projected from the panel pixels for each unit period, where each unit period is each of k unit periods from the first unit period to the k-th unit period included in one frame period, and k is an integer of 2 or more; and a display control circuit that controls the liquid crystal panel and the optical path shift element. The display control circuit supplies a data signal corresponding to the gray level specified by the image pixel data constituting the image data to the panel pixels for each unit period, and controls the projection position for each unit period for the optical path shift element. The optical path shift element shifts the projection position to the target projection position after passing over the target projection position for each unit period.

[0152] In the projection display device according to the first aspect, the reduction in display quality caused by alignment defects becomes less obvious.

[0153] In the projection display device according to a specific second aspect of the first aspect, in the shift from the immediately preceding target projection position in the unit period before one unit period to the target projection position in that one unit period, the maximum separation distance from the immediately preceding target projection position is 1 pixel or more in the panel pixels.

[0154] In the projection display device according to a specific third aspect of the second aspect, the optical path shift element shifts the projection position from the immediately preceding target projection position to a position opposite to the target projection position as a reference, and then returns to the target projection position.

[0155] In the projection display device according to a specific fourth aspect of the first aspect, the optical path shift element shifts the projection position from the immediately preceding target projection position, turns at the target projection position, and then returns to the target projection position in a clockwise or counterclockwise manner when observed on the projection surface.

[0156] In the projection display device according to a specific fifth aspect of the first aspect, the optical path shift element shifts the projection position from the immediately preceding target projection position, goes straight at the target projection position, and then returns to the target projection position in a clockwise or counterclockwise manner when observed on the projection surface.

Claims

1. A projection display device, characterized in that, Comprising: A liquid crystal panel having panel pixels; An optical path shift element that shifts the optical path of the projection light so that the projection position of the projection pixels displayed using the projection light projected from the panel pixels is changed for each unit period, where each unit period is each of the k unit periods from the first unit period to the k-th unit period included in one frame period, and k is an integer of 2 or more; and A display control circuit that controls the liquid crystal panel and the optical path shift element, The display control circuit supplies a data signal corresponding to the gray level specified by the image pixel data constituting the image data to the panel pixels for each of the unit periods, and controls the projection position for each of the unit periods with respect to the optical path shift element, The optical path shift element shifts the projection position to the target projection position after passing over the target projection position for each of the unit periods.

2. The projection display device according to claim 1, wherein In the shift from the immediately preceding target projection position in the unit period before a certain unit period to the target projection position in that certain unit period, the maximum separation distance from the immediately preceding target projection position is 1 pixel or more in the panel pixels.

3. The projection display device according to claim 2, wherein The optical path shift element shifts the projection position from the immediately preceding target projection position to a position opposite to the target projection position as a reference, and then returns to the target projection position.

4. The projection display device according to claim 2, wherein The optical path shift element shifts the projection position from the immediately preceding target projection position, turns at the target projection position, and then returns to the target projection position in a clockwise or counterclockwise manner when observed on the projection surface.

5. The projection display device according to claim 2, wherein The optical path shift element shifts the projection position from the immediately preceding target projection position, goes straight at the target projection position, and then returns to the target projection position in a clockwise or counterclockwise manner when observed on the projection surface.

Images