Projection type display device

Abstract

To prevent display unevenness.SOLUTION: A display control circuit supplies a data signal corresponding to a gradation level designated by pixel data constituting video data, to a panel pixel for every unit period f-1 to unit period f-4, and controls the shift of a light path for a light path shift element for every unit period f-1 to unit period f-4. The light path shift element shifts a light path by 1.0 pixel or more of the panel pixel, from the unit period f-4 to the unit period f-1, for example, of the unit periods f-1 to unit period f-4, and in the up-and-down direction, for example, of the left-and-right direction or the up-and-down direction in which projection pixels are arranged side by side. In part or all of a period during which the light path is shifted, light source is turned off or dimmed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] A technology for artificially increasing the resolution by using a light path shift element is known in a projection display device that projects image light created by a liquid crystal panel or the like onto a screen, etc. In detail, in a projection display device, one frame period is divided into a plurality of unit periods, and the projection position of one panel pixel on the liquid crystal panel is shifted for each of the plurality of unit periods, and in each unit period, a gray scale level specified by video pixel data is individually expressed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-139968 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above technique has a problem in that, when viewed over one frame period, display unevenness caused by the shift in projection position is visible, resulting in a decrease in display quality. [Means for solving the problem]

[0005] In order to solve the above-described problems, a projection display device according to one aspect of the present disclosure includes: a light source that emits light; a liquid crystal panel having panel pixels to which the light emitted from the light source is incident; a light path shift element that shifts an optical path of the projection light from the panel pixels and projects the projection pixels as projection pixels; the light path shift element that shifts the optical path of the projection light so as to change the position of the projection pixel for each of k unit periods from a first unit period to a kth unit period (k is an integer of 2 or more) included in one frame period; and a display control circuit that controls the light source, the liquid crystal panel, and the light path shift element, The display control circuit supplies a data signal corresponding to a gradation level specified by pixel data constituting video data to the panel pixels for each unit period, and controls the light path shift element to shift the light path for each unit period, and the light path shift element shifts the light path of the projection light by one or more panel pixels in at least one of a first direction in which the projection pixels are arranged or a second direction in which the positions of the projection pixels are arranged, during at least one of the unit periods, and turns off or dims the light source for part or all of the period in which the light path is shifted. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a diagram showing a projection display device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a first projection display device. [Figure 3] 1 is a diagram showing the relationship between the arrangement of video pixels and the arrangement of panel pixels in a projection display device. [Figure 4] FIG. 1 is a diagram showing the relationship between one frame period and a unit period in a projection display device. [Figure 5] FIG. 10 is a diagram showing projection positions in one frame period. [Figure 6] FIG. 10 is a diagram illustrating a control signal to a light path shift element and a lamp unit. [Figure 7] FIG. 1 is a perspective view showing a configuration of a liquid crystal panel in a projection display device. [Figure 8] FIG. 2 is a cross-sectional view showing the structure of a liquid crystal panel. [Figure 9] FIG. 2 is a block diagram showing the electrical configuration of a liquid crystal panel. [Figure 10] FIG. 2 is a diagram showing the configuration of a pixel circuit in a liquid crystal panel. [Figure 11] FIG. 2 is a diagram showing the relationship between video pixels, panel pixels, and projection positions in one frame period. [Figure 12] FIG. 10 is a diagram showing the projection position in one frame period of the projection display device according to the second embodiment. [Figure 13] FIG. 10 is a diagram illustrating a control signal to a light path shift element and a lamp unit. [Figure 14] FIG. 10 is a diagram showing the relationship between two frame periods and a unit period in a projection display device according to a third embodiment. [Figure 15] FIG. 2 is a diagram showing a projection position of a projection display device. [Figure 16] FIG. 10 is a diagram illustrating a control signal to a light path shift element and a lamp unit. [Figure 17] FIG. 10 is a diagram showing the projection position of a projection display device according to a fourth embodiment. [Figure 18] FIG. 10 is a diagram illustrating a control signal to a light path shift element and a lamp unit. [Figure 19] FIG. 10 is a diagram showing a projection position of a projection display device according to a comparative example. [Figure 20] 10A and 10B are diagrams for explaining degradation of display quality in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Projection display devices according to embodiments will be described below with reference to the drawings. In each drawing, the dimensions and scale of each part are appropriately different from those of the actual device. The embodiments described below are preferred examples, and therefore various technically preferable limitations are applied. However, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0008] 1 is a diagram showing the optical configuration of a projection display device 1 according to a first 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 lamp unit 2102, three mirrors 2106, and two dichroic mirrors 2108 are provided. The lamp unit 2102 emits white light using an LED or laser light source. The white light emitted from the lamp unit 2102 is separated by two dichroic mirrors 2108 into the three primary colors of red (R), green (G), and blue (B). 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.

[0009] Since the optical path of B is longer than the optical paths of R and G, it is necessary to prevent loss in the optical path of B. For this reason, a relay lens system 2121 consisting of an input lens 2122, a relay lens 2123, and an output lens 2124 is provided in the optical path of B.

[0010] The liquid crystal panel 100R has a plurality of pixel circuits, as will be described later. Each of the plurality of 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 exhibit a transmittance according to the voltage of the data signal. Therefore, an R transmission image is generated in the liquid crystal panel 100R by individually controlling the transmittance of the liquid crystal elements based on the data signal corresponding to R. Similarly, a G transmission image is generated in the liquid crystal panel 100G based on the data signal corresponding to G, and a B transmission image is generated in the liquid crystal panel 100B based on the data signal corresponding to B.

[0011] The transmitted images of each color 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 light are refracted at 90 degrees, while the G light travels straight. Therefore, the dichroic prism 2112 combines the images of each color. The combined image by the dichroic prism 2112 is incident on the projection lens 2114 via the optical path shift element 230. The projection lens 2114 enlarges and projects the composite image that has passed through the optical path shift element 230 onto the screen Scr.

[0012] The light path shift element 230 shifts the light path of the light emitted from the dichroic prism 2112. In detail, the light path shift element 230 shifts the composite image projected onto the screen Scr in the left-right direction and / or the up-down direction with respect to the projection surface.

[0013] The transmitted images by the liquid crystal panels 100R and 100B are projected after being reflected by the dichroic prism 2112, whereas the transmitted image by the liquid crystal panel 100G is projected in a straight line. Therefore, the transmitted images by the liquid crystal panels 100R and 100B are left-right inverted relative to the transmitted image by the liquid crystal panel 100G.

[0014] 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 circuit 20, liquid crystal panels 100R, 100G, and 100B, a light path shift element 230, and a lamp unit 2102.

[0015] Video data Vid-in is supplied from a host device or other higher-level device (not shown) in synchronization with a synchronization signal Sync. The video data Vid-in specifies the gradation levels of the pixels that make up one frame period of video, for example, by 8 bits for each RGB.

[0016] Note that the pixels of an image specified by the video data Vid-in are referred to as video pixels, and the data specifying the gradation levels of the video pixels are referred to as video pixel data, but in some cases, no distinction is made between video pixels and video pixel data. Furthermore, the pixels of an image before or after composition by the liquid crystal panel 100R, 100G, or 100B are referred to as panel pixels. The position of the panel pixel shifted by the light path shift element 230 and projected onto the screen Scr is referred to as the projection position. In the liquid crystal panels 100R, 100G, and 100B, the panel pixels are arranged in a matrix in a plan view. In the embodiment, the arrangement of the video pixels specified by the video data Vid-in is, for example, twice as large vertically and twice as large horizontally as the arrangement of the panel pixels of the liquid crystal panels 100R, 100G, or 100B.

[0017] In this embodiment, a color image projected onto the screen Scr is expressed by combining the transmitted images of the liquid crystal panels 100R, 100G, and 100B. Therefore, the smallest unit of a color image can be divided into a red subpixel of the liquid crystal panel 100R, a green subpixel of the liquid crystal panel 100G, and a blue subpixel of the liquid crystal panel 100B. However, when it is not necessary to specify the color of the subpixels of the liquid crystal panels 100R, 100G, and 100B, or when only brightness is an issue, there is no need to refer to them as subpixels. Therefore, in this description, the display units of the liquid crystal panels 100R, 100G, and 100B will also be referred to as panel pixels.

[0018] 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.

[0019] The display control circuit 20 includes a processing circuit 21, and conversion circuits 22R, 22G, and 22B. The processing circuit 21 controls the conversion circuits 22R, 22G, and 22B, the liquid crystal panels 100R, 100G, and 100B, the light path shift element 230, and the lamp unit 2102 for each unit period f-1 to f-4 based on the synchronization signal Sync. The light path shift element 230 shifts the projection position in accordance with the control signals P_x and P_y supplied from the processing circuit 21. The lamp unit 2102 turns on or off the emitted light in accordance with the control signal Lmp supplied from the processing circuit 21.

[0020] In this embodiment, the lamp unit 2102 turns off the emitted light in accordance with the control of the processing circuit 21, but it may be configured to dim the light instead of turning it off. That is, the lamp unit 2102 may be configured to switch between a first state in which the light is turned on and the second state in which the light is dimmer than the first state.

[0021] Of the video data Vid-in supplied from the higher-level device, the R component is represented as video data Va_R, the G component as video data Va_G, and the B component as video data Va_B.

[0022] The conversion circuit 22R temporarily stores the video data Va-R supplied from the higher-level device in an internal buffer for one or more frame periods, then reads out the video data corresponding to the unit period, converts it into an analog voltage data signal Vid_R, and supplies it to the liquid crystal panel 100R. Conversion circuits 22G and 22B differ from conversion circuit 22R only in the color components of the video data to be converted, but otherwise share the same characteristics as conversion circuit 22R. That is, conversion circuit 22G converts video data Va-G corresponding to a unit period into an analog voltage data signal Vid_G and supplies it to liquid crystal panel 100G, while conversion circuit 22B converts video data Va-B corresponding to a unit period into an analog voltage data signal Vid_B and supplies it to liquid crystal panel 100B.

[0023] FIG. 3 is a diagram for explaining the correspondence between video pixels and panel pixels in the projection display device 1. As shown in FIG. In detail, in Figure 3, the left column is a diagram showing a portion of the arrangement of video pixels indicated by the video data Vid-in, and the right column is a diagram showing a portion of the panel pixels corresponding to the arrangement of the video pixels in the left column.

[0024] In the array in the left column, in order to distinguish between the video pixels in the image represented by the video data Vid-in, the following codes are conveniently assigned to the first row: A0 to A5, B0 to B5, C0 to C5, D0 to D5, E0 to E5, and F0 to F6. Similarly, in the array in the right column of Fig. 3, in order to distinguish between the panel pixels, the following codes are conveniently assigned to the first row: a1 and a2, and b2 and b3, respectively.

[0025] 4 is a diagram illustrating the relationship between a frame period and a unit period in the projection display device 1 according to the first embodiment. As shown in the diagram, in this embodiment, one frame (F) period is divided into four unit periods in terms of time. For convenience, the four unit periods are assigned symbols f-1, f-2, f-3, and f-4 in chronological order to distinguish them from one another.

[0026] One frame period is the period during which one frame of an image represented by video data Vid-in is supplied from a higher-level device, and is 16.7 milliseconds, or one cycle, when the frequency of the vertical synchronization signal included in the synchronization signal Sync is 60 Hz. In this case, the length of each unit period is 4.17 milliseconds, which is 1 / 4 of the length of one frame period.

[0027] In this embodiment, the processing circuit 21 controls the light path shift element 230 so that the projection position changes for each unit period f-1 to f-4. In one unit period, the user views an image in which the resolution of an image in one frame period specified by video data Vid-in is reduced to 1 / 4 as a composite image produced by liquid crystal panels 100R, 100G, and 100B. In the following description, when the liquid crystal panels 100R, 100G, and 100B are generally described without specifying the color, they will be denoted by the reference numeral 100.

[0028] 5 is a diagram showing the relationship between image pixels represented by one panel pixel for each of unit periods f-1 to f-4. In other words, the diagram shows the projection positions for unit periods f-1 to f-4.

[0029] Note that a panel pixel "expresses" a certain video pixel means that the liquid crystal element 120 of the panel pixel is in a state where it has a transmittance corresponding to the gradation level (video pixel data) of the video pixel. For convenience, in the figure, two rows and two columns of video pixels are enclosed in a thick frame. The light path shift element 230 shifts the image projected onto the screen Scr in the vertical and horizontal directions toward the projection surface. For convenience, the amount of shift will be explained in terms of the size of the pixels projected onto the screen Scr, i.e., the size of the panel pixels.

[0030] The projection position in unit period f-1 is the reference position. In unit period f-2, the projection position is shifted from the reference position in unit period f-1 by 0.5 panel pixels to the right and by 0.5 panel pixels downward in the figure. In other words, the projection position shifts diagonally downward to the right. In unit period f-3, the projection position is shifted 0.5 pixel to the left from the projection position in unit period f-2. In unit period f-4, the projection position is shifted 0.5 panel pixel to the right and 0.5 panel pixel downward from the projection position in unit period f-3. That is, the projection position shifts diagonally downward to the left. After unit period f-4, the projection position is shifted 0.5 panel pixel to the right and 1.0 panel pixel upward from the projection position in unit period f-4, returning to the reference position.

[0031] FIG. 6 is a diagram showing waveforms of the control signals P_x and P_y to the light path shift element 230 when the panel pixels represent the image pixels as shown in FIG. In the first embodiment, the control signal P_x takes one of three levels: −0.5 A, 0, or +0.5 A, except for the trailing end periods of the unit periods f-1 to f-4. The control signal P_y takes one of three levels: 0, +0.5 A, or +1.0 A, except for the trailing end periods of the unit periods f-1 to f-4. The levels of the control signals P_x and P_y change during the trailing edge period. The trailing edge period is a period following the vertical scanning effective period in which the first to mth scanning lines 12 are selected during a unit period, and corresponds to the vertical scanning blanking period. The level of the control signal P_x or P_y may be constant across two consecutive unit periods.

[0032] In FIG. 6, the arrows shown in the rear end period of each unit period indicate the direction in which the projection position shifts when the levels of the control signals P_x and P_y change in that rear end period.

[0033] Next, liquid crystal panels 100R, 100G, and 100B will be described. Liquid crystal panels 100R, 100G, and 100B have a common structure, with the only difference being the color, or wavelength, of the light incident on them. Therefore, liquid crystal panels 100R, 100G, and 100B will be generally described as liquid crystal panel 100, without specifying the color.

[0034] FIG. 7 is a perspective view showing the liquid crystal panel 100, and FIG. 8 is a cross-sectional view taken along line Hh in FIG. As shown in these figures, in the liquid crystal panel 100, an element substrate 100a on which a pixel electrode 118 is provided and an opposing substrate 100b on which a common electrode 108 is provided are bonded together with a sealing material 90 so that the electrode forming surfaces face each other while maintaining a certain gap, and liquid crystal 105 is sealed in this gap.

[0035] The element substrate 100a and the counter substrate 100b are each made of a light-transmitting substrate such as glass or quartz. As shown in FIG. 7, one side of the element substrate 100a extends beyond the counter substrate 100b. A plurality of terminals 106 are provided in this extending area along the horizontal direction in the figure. One end of an FPC (Flexible Printed Circuits) substrate (not shown) is connected to the plurality of terminals 106. The other end of the FPC substrate is connected to the display control circuit 20, and the various signals described above are supplied.

[0036] On the surface of the element substrate 100a facing the counter substrate 100b, pixel electrodes 118 are formed by patterning a transparent conductive layer made of, for example, ITO (Indium Tin Oxide). Furthermore, although not shown, the counter substrate 100b (or the element substrate 100a) is provided with a microlens (not shown) for each panel pixel in order to efficiently send a large amount of light to the openings that become the panel pixels. With this configuration, light that would have been repelled by the light-shielding portion is sent to the openings of the microlens, thereby improving the light utilization efficiency.

[0037] 9 is a block diagram showing the electrical configuration of the liquid crystal panel 100. The liquid crystal panel 100 has a scanning line driving circuit 130 and a data line driving circuit 140 provided on the periphery of the display area 10.

[0038] In the display region 10 of the liquid crystal panel 100, pixel circuits 110 are arranged in a matrix. More specifically, in the display region 10, a plurality of scanning lines 12 are provided extending horizontally in the drawing, and a plurality of data lines 14 are provided extending vertically and electrically insulated from the scanning lines 12. The pixel circuits 110 are provided in a matrix corresponding to the intersections of the plurality of scanning lines 12 and the plurality of data lines 14.

[0039] If the number of scanning lines 12 is m and the number of data lines 14 is n, the pixel circuits 110 are arranged in a matrix of m rows and n columns. Both m and n are integers greater than or equal to 2. To distinguish between the rows of the matrix in the scanning lines 12 and the pixel circuits 110, they may be referred to as 1, 2, 3, ..., (m-1), m rows from top to bottom in the drawings. Similarly, to distinguish between the columns of the matrix in the data lines 14 and the pixel circuits 110, they may be referred to as 1, 2, 3, ..., (n-1), n ​​columns from left to right in the drawings.

[0040] The scanning line driving circuit 130 selects the scanning lines 12 one by one in the order of, for example, the 1st, 2nd, 3rd, ..., mth rows in accordance with the control of the display control circuit 20, and sets the scanning signal to the selected scanning line 12 to H level. Note that the scanning line driving circuit 130 sets the scanning signals to the scanning lines 12 other than the selected scanning line 12 to L level. The data line driving circuit 140 latches the data signals supplied from the corresponding color circuit among the conversion circuits 22R, 22G, or 22B for one row, and outputs them via the data line 14 to the pixel circuit 110 located on that scanning line 12 during the period when the scanning signal to that scanning line 12 is at H level.

[0041] FIG. 10 is a diagram showing an equivalent circuit of four pixel circuits 110 arranged in two rows and two columns corresponding to the intersections of two adjacent scanning 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 a scan line 12, the source node is connected to a data line 14, and the drain node is connected to a pixel electrode 118 that has a square shape in a plan view.

[0042] A common electrode 108 is provided in common to all pixels so as to face the pixel electrode 118. A voltage LCcom is applied to the common electrode 108. As described above, the liquid crystal 105 is sandwiched between the pixel electrode 118 and the common electrode 108. Therefore, 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. Furthermore, a storage capacitor 109 is provided in parallel to the liquid crystal element 120. One end of the storage capacitor 109 is connected to a pixel electrode 118, and the other end is connected to a capacitance line 107. A time-constant voltage, for example, a voltage LCcom that is the same as the voltage applied to the common electrode 108, is applied to the capacitance line 107. The pixel circuits 110 are arranged in a matrix in the horizontal direction, which is the extension direction of the scanning lines 12, and in the vertical direction, which is the extension direction of the data lines 14, and therefore the pixel electrodes 118 included in the pixel circuits 110 are also arranged in both the vertical and horizontal directions.

[0043] When the scanning signal for a scanning line 12 becomes high, the transistor 116 of the pixel circuit 110 provided corresponding to that scanning line 12 is turned on. When the transistor 116 is turned on, the data line 14 and the pixel electrode 118 are electrically connected, and the data signal supplied to the data line 14 reaches the pixel electrode 118 via the transistor 116 that is turned on. When the scanning line 12 becomes low, the transistor 116 is turned off, but the voltage of the data signal that reaches the pixel electrode 118 is held by the capacitance of the liquid crystal element 120 and the storage capacitor 109.

[0044] As is well known, 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 that corresponds to the effective value of the applied voltage. In addition, the region of the liquid crystal element 120 that functions as a panel pixel, i.e., the region that exhibits transmittance according 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 in a plan view. Since the pixel electrode 118 has a square shape in a plan view, the shape of the pixel formed by the liquid crystal panel 100 is also square. In addition, in this embodiment, the liquid crystal 105 is of a VA (Vertical Alignment) type, and is in a normally black mode in which the transmittance is at its lowest when the voltage applied to the liquid crystal element 120 is zero, and the transmittance increases as the applied voltage increases.

[0045] The operation of supplying data signals to the pixel electrodes 118 of the liquid crystal elements 120 is executed in the order of the 1st, 2nd, 3rd, ..., mth rows in each unit period f-1 to f-4. As a result, a voltage corresponding to the data signal is held in each of the liquid crystal elements 120 of the pixel circuits 110 arranged in m rows and n columns, each liquid crystal element 120 has the target 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, a transmission image is generated for each of the R, G, and B colors, and a color image obtained by combining the R, G, and B colors is projected onto the screen Scr. The data signals Vid_R, Vid_G, and Vid_B output in a unit period correspond to the RGB components of the video data corresponding to that unit period, so that a composite image of a color corresponding to the projection position is projected at that projection position in that unit period.

[0046] Next, how the image pixels are visually recognized by the user through the panel pixels in the projection display device 1 according to this embodiment will be described.

[0047] Fig. 11 is a diagram showing which video pixels are represented at which projection positions by panel pixels in the projection display device 1. In detail, Fig. 11 is a diagram showing at which projection positions four panel pixels a1, a2, b1, and b2 in the right column of Fig. 3 represent the video pixels in the left column of Fig. 3 during unit periods f-1 to f-4. Note that the bold frame in the right column of Fig. 11 indicates panel pixel b2. Also, the hatching in the left column of Fig. 11 indicates video pixels represented by panel pixels a1, a2, b1, and b2, and among these, the bold frame indicates the video pixel represented by panel pixel b2.

[0048] 11, in unit period f-1, panel pixels a1, a2, b1, and b2 represent hatched image pixels A1, A3, C1, and C3, respectively. The arrow pointing diagonally upward to the right of the panel pixels in unit period f-1 indicates a shift from their projection positions in unit period f-4 of the previous frame.

[0049] When the rear end period of the unit period f-1 is reached, the light path shift element 230 shifts the projection position from the reference position indicated by the dashed line f-1 by 0.5 panel pixels to the right and 0.5 panel pixels downward in the figure. In the next unit period f-2, panel pixels a1, a2, b1 and b2 sequentially represent hatched video pixels B2, B4, D2 and D4, respectively.

[0050] When the rear end period of the unit period f-2 is reached, the light path shift element 230 shifts the projection position by 0.5 panel pixels to the left in the drawing from the projection position indicated by the dashed line f-2. In the next unit period f-3, the panel pixels a1, a2, b1 and b2 sequentially represent the hatched video pixels B1, B3, D1 and D3, respectively.

[0051] At the rear end period of unit period f-3, the light path shift element 230 shifts the projection position from the projection position indicated by the dashed line f-3 by 0.5 panel pixels to the left and 0.5 panel pixels downward in the figure. In the next unit period f-4, the panel pixels a1, a2, b1 and b2 sequentially represent the hatched video pixels C0, C2, E0 and E2, respectively.

[0052] When the rear end period of unit period f-4 is reached, the projection position is shifted by the light path shift element 230 from the projection position indicated by the dashed line f-4 to the right by 0.5 panel pixels and upward by 1.0 panel pixel in the figure, returning to the reference position.

[0053] Before describing the display quality in this embodiment, a description will be given of the degradation in display quality that occurs in a projection display device according to a comparative example.

[0054] FIG. 19 is a diagram showing the relationship between video pixels expressed by one panel pixel in unit periods f-1 to f-4 in a comparative example.

[0055] As in the first embodiment, the projection position in unit period f-1 is the reference position. In unit period f-2, the projection position is shifted by 0.5 panel pixels to the right in the figure from the reference position in unit period f-1. In unit period f-3, the projection position is shifted by 0.5 panel pixels downward from the projection position in unit period f-2. In unit period f-4, the projection position is shifted by 0.5 panel pixels to the left from the projection position in unit period f-3. After unit period f-4, the projection position is shifted by 0.5 pixel upward from the projection position in unit period f-4 and returns to the reference position.

[0056] In the comparative example, video pixels expressed by panel pixels in unit periods f-1 to f-4 will be described. 3 for comparison with the embodiment, panel pixels a1, a2, b1, and b2 sequentially represent video pixels A1, A3, C1, and C3 in unit period f-1. Similarly, panel pixels a1, a2, b1, and b2 sequentially represent video pixels A2, A4, C2, and C4 in unit period f-2, sequentially represent video pixels B2, B4, D2, and D4 in unit period f-3, and sequentially represent video pixels B1, B3, D1, and D3 in unit period f-4.

[0057] FIG. 20 is a diagram illustrating display unevenness in a comparative example. As described above, in the liquid crystal panel 100, a microlens is provided for each panel pixel to improve light utilization efficiency. For this reason, the brightness of the panel pixels is not uniform. If the light path is not shifted, as shown in the left column of FIG. 20, the brightness is higher near the center and becomes darker as you move from the center to the outside. Note that the frame Ppx indicates the outer edge of the panel pixels in the liquid crystal panel 100 at the reference position.

[0058] In the comparative example, the panel pixels viewed in this manner are shifted in sequence from the reference position by 0.5 panel pixels in the following order: right → downward → left → upward, as shown in the right column of Figure 20, during unit periods f-1 to f-4. For this reason, when viewed over one frame period, the bright areas of the panel pixels circulate along the path indicated by the arrows in the figure, resulting in separation into bright areas that are perceived as relatively bright areas and the remaining dark areas. This difference between the bright and dark areas is perceived as display unevenness. This display unevenness is easily visible when displaying a relatively bright still image.

[0059] In the comparative example, the display unevenness that occurs during one frame period is caused by the uneven distribution of areas with high and low overlap due to the shift, since the panel pixels are larger than the video pixels. In the comparative example, the grid-like dark areas that occur during one frame period are particularly dark where the vertical and horizontal lines intersect. Conversely, the optical path of the shift is changed so that the center of a panel pixel that appears bright passes through the dark area. Specifically, at least one or more video pixels represented by a single panel pixel are shifted by one or more panel pixels in the vertical or horizontal direction. More specifically, of the two rows and two columns of video pixels indicated by the bold frame in Figure 3, at least one or more video pixels are represented by panel pixels different from the other video pixels. It was believed that changing the optical path of the shift in this way could eliminate display unevenness, with one frame period considered as one unit.

[0060] However, the amount and direction of shift of the optical path are non-uniform from the projection position in one unit period to the projection position in the next unit period, which causes a problem in that the shift of the optical path causes different display irregularities to be visible.

[0061] Therefore, in the first embodiment, when returning from unit period f-4 to unit period f-1, not only is the optical path shifted upward by 1.0 pixel in panel pixels, but also, as shown in Figure 6, the lamp unit 2102 is turned off when the optical path is shifted.

[0062] In detail, in the first embodiment, the lamp unit 2102 can control whether to emit light by turning on or off the light source. In the first embodiment, when the control signal Lmp is at H level, the lamp unit 2102 is instructed to turn on, and when the control signal Lmp is at L level, the lamp unit 2102 is instructed to turn off. In the first embodiment, the period during which the control signal Lmp becomes L level and the lamp unit 2102 is instructed to turn off is the rear end period of each unit period, i.e., the period during which the light path is shifted by the light path shift element 230.

[0063] In the first embodiment, assume a configuration in which the lamp unit 2102 is not turned off. In this assumed configuration, the projection positions in unit periods f-1, f-2, and f-3 are in a relatively narrow range, resulting in a large overlap and a relatively bright image. In contrast, the projection position in unit period f-4 is farther away than the other projection positions, and the shift amount from unit period f-4 to unit period f-1 is long, resulting in a small overlap with the projection positions in other unit periods and a relatively dark image. In the first embodiment, the lamp unit 2102 is actually turned off when the optical path shifts, thereby reducing display unevenness caused by uneven shift amounts and shift directions. Furthermore, according to the first embodiment, display unevenness caused by uneven distribution of areas with large and small overlaps due to shifts can be reduced.

[0064] 5, in the first embodiment in which the light path is shifted, the lamp unit 2102 is turned off when the light path is shifted, but the amount of shift of the light path from one unit period to the next unit period is non-uniform. Therefore, there is room for improvement in the display unevenness caused by the non-uniformity of the shift amount. Therefore, a second embodiment will be described, which can further reduce display unevenness caused by non-uniformity in the shift amount than the first embodiment.

[0065] FIG. 12 is a diagram showing the relationship between video pixels expressed by one panel pixel in unit periods f-1 to f-4 in the second embodiment.

[0066] The projection position in unit period f-1 is the reference position. In unit period f-2, the projection position is shifted rightward by 1.0 panel pixel and downward by 0.5 panel pixel in the figure from the reference position of unit period f-1. In unit period f-3, the projection position is shifted leftward by 0.5 panel pixel and downward by 1.0 panel pixel from the projection position of unit period f-2. In unit period f-4, the projection position is shifted leftward by 1.0 panel pixel and upward by 0.5 panel pixel from the projection position of unit period f-3. After unit period f-4, the projection position is shifted leftward by 0.5 panel pixel and upward by 1.0 panel pixel from the projection position of unit period f-4, returning to the reference position.

[0067] FIG. 13 is a diagram showing waveforms of the control signals P_x and P_y to the light path shift element 230 when the panel pixels represent the image pixels as shown in FIG. Although explanations overlapping with those in FIG. 6 will be omitted, in the second embodiment, the control signal P_x takes one of four levels: −0.5A, 0, +0.5A, and +1.0A. If the control signal P_x is +1.0A, the projection position is shifted 1.0 panel pixel to the left from the reference position. Also, in the second embodiment, the control signal P_y takes one of four levels: 0, +0.5A, +1.0A, or +1.5A. If the control signal P_x is +1.5A, the projection position is shifted 1.5 panel pixel downward from the reference position.

[0068] Next, in the second embodiment, video pixels expressed by panel pixels in unit periods f-1 to f-4 will be described. 3 for comparison with the first embodiment, panel pixels a1, a2, b1, and b2 sequentially represent video pixels A1, A3, C1, and C3 in unit period f-1. Similarly, panel pixels a1, a2, b1, and b2 sequentially represent video pixels B3, B5, D3, and D5 in unit period f-2, sequentially represent video pixels D2, D4, F2, and F4 in unit period f-3, and sequentially represent video pixels C0, C2, E0, and E2 in unit period f-4.

[0069] According to the second embodiment, it is possible to suppress display unevenness caused by uneven distribution of areas with a lot of overlap and areas with little overlap due to shifting, as in the first embodiment. According to the second embodiment, like the first embodiment, the lamp unit 2102 is turned off when the optical path shifts, but because the shift amount and the shift change direction are aligned, it is possible to suppress display unevenness caused by unevenness more than in the first embodiment. Furthermore, in the second embodiment, the amount of shift in the optical path is large, so the overlapping range due to the shift is wide and averaged out, which also helps to reduce display unevenness.

[0070] Next, a third embodiment will be described. In the first and second embodiments, the period for shifting the optical path is one frame period, but the present invention is not limited to this configuration. Therefore, a third and fourth embodiment will be described in which the period for shifting the optical path is set to two frame periods.

[0071] FIG. 14 is a diagram illustrating the relationship between two frame periods and a unit period in the projection display device according to the third embodiment. In the third embodiment, one cycle of the light path shift is a two-frame (2F) period, which is conveniently divided into an odd-numbered frame period that is earlier in time and an even-numbered frame period that is later in time. An odd-numbered frame period is divided into four unit periods. For convenience of distinguishing the four unit periods in an odd-numbered frame period, the four unit periods are assigned reference symbols f1-1, f1-2, f1-3, and f1-4 in chronological order. An even-numbered frame period is similarly divided into four unit periods. For convenience of distinguishing the four unit periods in an even-numbered frame period, the four unit periods are assigned reference symbols f2-1, f2-2, f2-3, and f2-4 in chronological order.

[0072] The projection position in unit period f1-1 is the reference position. In unit period f1-2, the projection position is shifted upward by 0.5 panel pixels in the figure from the reference position of unit period f1-1. In unit period f-3, the projection position is shifted leftward by 0.5 panel pixels from the projection position of unit period f1-2. In unit period f-4, the projection position is shifted downward by 0.5 panel pixels from the projection position of unit period f1-3. After unit period f-4, the projection position is shifted rightward by 0.5 panel pixels from the projection position of unit period f1-4 and returns to the reference position. The projection position in unit period f2-1 is the reference position. In unit period f2-2, the projection position is shifted downward by 0.5 panel pixels from the projection position in unit period f2-1. In unit period 2-3, the projection position is shifted rightward by 0.5 panel pixels from the projection position in unit period f2-2. In unit period 2-4, the projection position is shifted upward by 0.5 panel pixels from the projection position in unit period f2-3. After unit period f2-4, the projection position is shifted leftward by 0.5 panel pixels from the projection position in unit period f2-4 and returns to the reference position.

[0073] Fig. 15 is a diagram showing waveforms of the control signals P_x and P_y to the light path shift element 230 when the panel pixels represent the image pixels as shown in Fig. 14. Since the explanation of Fig. 6 overlaps with that of Fig. 6, no further explanation is considered necessary.

[0074] In the third embodiment, video pixels represented by panel pixels in unit periods f1-1 to f1-4 in odd-numbered frame periods and unit periods f2-1 to f2-4 in even-numbered frame periods will be described. For convenience, the description will focus on only panel pixels b1 and b2 in FIG.

[0075] Panel pixels b1 and b2 alternately represent video pixels D2 and D4 in unit period f1-1 of the odd-numbered frame period. Similarly, panel pixels b1 and b2 alternately represent video pixels C2 and C4 in unit period f1-2, video pixels C1 and C3 in unit period f1-3, and video pixels D1 and D3 in unit period f1-4. Panel pixels b1 and b2 alternately represent video pixels D2 and D4 in unit period f2-1 of the even-numbered frame period. Similarly, panel pixels b1 and b2 alternately represent video pixels E2 and E4 in unit period f2-2, video pixels E3 and E5 in unit period f2-3, and video pixels D3 and D5 in unit period f2-4.

[0076] According to the third embodiment, the area Led that becomes brighter due to the shift of the unit periods f2-1 to f2-4 in the even frame period overlaps with the area Ded (see FIG. 20) that becomes darker due to the shift of the unit periods f1-1 to f1-4 in the odd frame period. In other words, the area that becomes darker in the even frame period overlaps with the area that becomes brighter in the odd frame period. Therefore, in the third embodiment, the relatively bright areas of the panel pixels due to the shift in the optical path overlap with the dark areas, thereby reducing display unevenness. Furthermore, when the optical path shifts, the lamp unit 2102 is turned off, thereby suppressing display unevenness due to the shift in the optical path.

[0077] The projection display device according to the fourth embodiment is similar to the third embodiment in that the unit periods f1-1 to f1-4 in the odd-numbered frame period and the unit periods f2-1 to f2-4 in the even-numbered frame period are one period of the light path shift.

[0078] In the fourth embodiment, the projection position in unit period f1-1 is also the reference position. In unit period f1-2, the projection position is shifted upward by 0.5 panel pixels in the figure from the reference position of unit period f1-1. In unit period f1-3, the projection position is shifted right by 0.5 panel pixels and downward by 0.5 panel pixels from the projection position of unit period f1-2. In unit period f1-4, the projection position is shifted downward by 0.5 panel pixels from the projection position of unit period f1-3. After unit period f1-4, the projection position is shifted left by 0.5 panel pixels and upward by 0.5 panel pixels from the projection position of unit period f1-4, returning to the reference position.

[0079] The projection position in unit period f2-1 is the reference position. In unit period f2-2, the projection position is shifted downward by 0.5 panel pixels from the projection position in unit period f2-1. In unit period 2-3, the projection position is shifted right by 0.5 panel pixels and upward by 0.5 panel pixels from the projection position in unit period f2-2. In unit period 2-4, the projection position is shifted upward by 0.5 panel pixels from the projection position in unit period f2-3. After unit period f2-4, the projection position is shifted left by 0.5 panel pixels and downward by 0.5 panel pixels from the projection position in unit period f2-4, returning to the reference position.

[0080] Fig. 18 is a diagram showing waveforms of the control signals P_x and P_y to the light path shift element 230 when the panel pixels represent the image pixels as shown in Fig. 17. Since the explanation overlaps with that of Fig. 6, no further explanation is considered necessary.

[0081] In the fourth embodiment, video pixels represented by panel pixels in unit periods f1-1 to f1-4 in odd-numbered frame periods and unit periods f2-1 to f2-4 in even-numbered frame periods will be described. For convenience, the description will focus on only panel pixels b1 and b2 in FIG.

[0082] Panel pixels b1 and b2 alternately represent video pixels D1 and D3 in unit period f1-1 of the odd-numbered frame period. Similarly, panel pixels b1 and b2 alternately represent video pixels C1 and C3 in unit period f1-2, video pixels D2 and D4 in unit period f1-3, and video pixels E2 and E4 in unit period f1-4. Panel pixels b1 and b2 alternately represent video pixels D1 and D3 in unit period f2-1 of the even-numbered frame period. Similarly, panel pixels b1 and b2 alternately represent video pixels E1 and E3 in unit period f2-2, video pixels D2 and D4 in unit period f2-3, and video pixels C2 and C4 in unit period f2-4.

[0083] In the fourth embodiment, unlike the third embodiment, the dark regions in the odd-numbered frame periods and the even-numbered frame periods are parallelograms, and the bright regions are also parallelograms. However, according to the fourth embodiment, the bright regions in the even-numbered frame periods overlap with parts of the dark regions in the odd-numbered frame periods, and the dark regions in the even-numbered frame periods overlap with parts of the bright regions in the odd-numbered frame periods. Therefore, in the fourth embodiment, the relatively bright areas of the panel pixels due to the shift in the optical path overlap with the dark areas, thereby reducing display unevenness. Furthermore, when the optical path shifts, the lamp unit 2102 is turned off, thereby suppressing display unevenness due to the shift in the optical path.

[0084] In the first to fourth embodiments (hereinafter referred to as "embodiments"), various modifications or applications are possible as described below.

[0085] In the embodiment, the liquid crystal panel 100 is of a transmissive type, but it may also be of a reflective type. Furthermore, in the embodiment and the like, the period during which the lamp unit 2102 is turned off (or dimmed) is part of the period during which the light path is shifted, but it may be the entire period during which the light path is shifted.

[0086] In the embodiment and the like, the timing at which the shift of the light path in the light path shift element 230 starts is set to the rear end period corresponding to the vertical scanning period of the unit period, but there may be a time delay. In such a case, for example, the processing circuit 21 may be configured to control the light path shift element in anticipation of the time delay so that the image formed by the liquid crystal panel 100 in the unit period is shifted to the projection position corresponding to the unit period.

[0087] In the embodiments, one frame period is divided into four unit periods. That is, the number k of unit periods included in one frame period is set to "4" as an example. However, k is not limited to "4." Specifically, the shift amount of the optical path from one unit period to the next may be "2" or "3" as long as it is 1.0 or more panel pixels in the vertical or horizontal direction, or may be an integer of 5 or more.

[0088] For example, in the first embodiment, the shift amount from unit period f-4 to unit period f-1 is larger than the others. In other words, the shift speed from unit period f-4 to unit period f-1 is faster than the others. Therefore, the extinguishing period / dimming amount of the lamp unit 2102, or both, may be controlled according to the shift amount or the shift speed.

[0089] The optical path shift may be switched depending on the type of image represented by the image data Vid-in, for example, line drawing / natural image. For example, the processing circuit 21 may be configured to detect the type of image represented by the image data Vid-in, and if it is a line drawing, switch to the light path shift in the third or fourth embodiment, and if it is a natural image, switch to the light path shift in the second embodiment. Note that the line drawing here refers to an image made up of ruled lines, tables, letters, numbers, etc. in an OA or the like, and in which there is a large change in the gradation level of adjacent image pixels, and the natural image refers to a photograph, painting, etc. This refers to an image in which there is little change in the gray level of adjacent image pixels.

[0090] In the embodiment and the like, the lamp unit 2102 emits white light, which is separated into red (R), green (G), and blue (B) color lights by two dichroic mirrors 2108. However, the present invention is not limited to this configuration, and three lamp units that emit red light, green light, and blue light individually may be provided, and the emitted red light, green light, and blue light may be incident on the liquid crystal panels 100R, 100G, and 100B in that order.

[0091] In this description, the left-right direction is an example of a "first direction," the up-down direction is an example of a "second direction," and the lamp unit 2102 is an example of a "light source." For example, in Fig. 5, the shift amount from unit period f-1 to unit period f-2 is an example of a "first shift amount," and the shift amount from unit period f-4 to unit period f-1 is an example of a "second shift amount." Also, for example, Fig. 11 shows an example in which, among unit periods f-1 to f-4 that make up one frame, the shift amount from unit period f-1 to unit period f-2, the shift amount from unit period f-2 to unit period f-3, the shift amount from unit period f-3 to unit period f-4, and the shift amount from unit period f-4 to unit period f-1 are all the same.

[0092] From the above-described exemplary embodiments, the following aspects can be understood, for example.

[0093] A projection display device according to one aspect 1 includes a light source that emits light, a liquid crystal panel having panel pixels to which the light emitted from the light source is incident, a light path shift element that shifts the optical path of the projection light from the panel pixels and projects the light as a projection pixel, and a light path shift element that shifts the optical path of the projection light so as to change the position of the projection pixel for each of k unit periods from a first unit period to a kth unit period (k is an integer equal to or greater than 2) included in one frame period, and a display control circuit that controls the light source, the liquid crystal panel, and the light path shift element, supplies a data signal corresponding to a gradation level specified by pixel data constituting video data to the panel pixel for each unit period, and controls the light path shift element to shift the light path for each unit period, and the light path shift element shifts the light path of the projection light by one or more panel pixels in at least one of a first direction in which the projection pixels are arranged or a second direction in which the positions of the projection pixels are arranged, during at least one of the unit periods, and turns off or dims the light source for part or all of the period in which the light path is shifted. Display device. According to the projection display device of aspect 1, the light source is turned off or dimmed when the optical path is shifted, thereby reducing display unevenness.

[0094] In a projection display device according to a second specific aspect of the first aspect, the light source is an LED or a laser light source.

[0095] In a projection display device according to a third specific aspect of the first aspect, the shift amount of the optical path for each of the k unit periods includes a first shift amount and a second shift amount different from the first shift amount.

[0096] The shift amount of the optical path in each of the k unit periods is the same. [Explanation of symbols]

[0097] 1... projection type display device, 100, 100R, 100G, 100B... liquid crystal panel, 110... pixel circuit, 118... pixel electrode, 120... liquid crystal element, 20... display control circuit, 21... processing circuit, 22R, 22G, 22B... conversion circuit, 230... light path shift element

Claims

1. a light source that emits light; a liquid crystal panel having panel pixels onto which light emitted from the light source is incident; a light path shift element that shifts the optical path of the projection light from the panel pixel and projects it as a projection pixel; a light path shift element that shifts the optical path of the projection light so as to change the position of the projection pixel for each of k unit periods from a first unit period to a kth unit period (k is an integer of 2 or more) included in one frame period; a display control circuit that controls the light source, the liquid crystal panel, and the light path shift element; Including, The display control circuit includes: supplying a data signal corresponding to a gradation level designated by pixel data constituting video data to the panel pixel for each unit period; controlling the shift of the optical path for the optical path shift element for each unit period; the light path shift element shifts the light path of the projection light in at least one of the unit periods by one or more panel pixels in at least one of a first direction and a second direction in which the positions of the projection pixels are arranged, The light source is turned off or dimmed during part or all of the period during which the optical path is shifted. Projection type display device.

2. The light source is LED or laser light source 2. The projection display device according to claim 1.

3. The shift amount of the optical path for each of the k unit periods includes a first shift amount and a second shift amount different from the first shift amount.

2. The projection display device according to claim 1.

4. The shift amount of the optical path in each of the k unit periods is the same.

2. The projection display device according to claim 1.

Images