Patent Application
20240071271
The present application is based on, and claims priority from JP Application Serial Number 2022-137622, filed Aug. 31, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety.
The present disclosure relates to a projection-type display apparatus.
With regard to a projection-type display apparatus that projects image light generated by a liquid crystal panel or the like onto a screen or the like, a technique is known that artificially increases resolution by an optical path shifting element. More specifically, in the projection-type display apparatus, a projection position of one panel pixel in the liquid crystal panel is shifted for each of a plurality of unit periods in one frame period, when expressing a plurality of pixel data in video data (see JP-A-2020-107984, for example).
However, with the technique described above, there is a problem in that the display quality deteriorates when a specific display pattern appears, as a still image, in an image designated by the video data. In light of such circumstances as described above, an advantage of an aspect of the present disclosure is to provide a technique for suppressing deterioration in display quality even when a specific display pattern appears in an image designated by video data.
In order to solve the problem described above, a projection-type display apparatus according to an aspect of the present disclosure includes a liquid crystal panel including a panel pixel, an optical path shifting element configured to shift a position of a projected pixel projected from the panel pixel in each of n unit periods from a first unit period to an n-th unit period included in one frame period, n being an integer of two or greater, and a display control circuit configured to control the liquid crystal panel and the optical path shifting element, in which the display control circuit supplies a data signal corresponding to pixel data constituting video data, to the panel pixel in each of the unit periods, controls the shift of the position of the projected pixel with respect to the optical path shifting element in each of the unit periods, supplies, to the liquid crystal panel, the data signal corresponding to the same pixel data and controls the position of the projected pixel to be at a same position in each of an initial first unit period of the n unit periods in a first frame period and an initial first unit period of the n unit periods in a second frame period subsequent to the first frame period, and controls the optical path shifting element to cause a shift direction from the position of the projected pixel before the shift to the position of the projected pixel after the shift from a second unit period to the n-th unit period of the first frame period to be opposite to the shift direction from the position of the projected pixel before the shift to the position of the projected pixel after the shift from the second unit period to the n-th unit period of the second frame period.
An electro-optical device according to embodiments will be described below with reference to the accompanying drawings. Note that in each of the drawings, dimensions and scale of each part are made different from actual ones as appropriate. Further, embodiments described below are suitable specific examples, and various technically preferable limitations are applied, but the scope of the disclosure is not limited to these embodiments unless they are specifically described in the following description as limiting the disclosure.
Note that since an optical path of B is longer than each of optical paths of R and G, it is necessary to prevent a loss in the B optical path. Thus, a relay lens system 2121 including an incidence lens 2122, a relay lens 2123, and an emission lens 2124 is provided at the B optical path.
The liquid crystal panel 100R includes a plurality of pixel circuits. Each of the plurality of pixel circuits includes a liquid crystal element. As described below, by the liquid crystal element of the liquid crystal panel 100R being driven based on a data signal corresponding to R, the liquid crystal panel 100R comes to have a transmittance corresponding to the data signal. Thus, in the liquid crystal panel 100R, a transmitted image of R is generated by individually controlling the transmittance of the liquid crystal element. Similarly, in the liquid crystal panel 100G, a transmitted image of G is generated based on a data signal corresponding to G, and in the liquid crystal panel 100B, a transmitted image of B is generated based on a data-signal corresponding to B.
The transmitted images of each of the colors generated by the liquid crystal panels 100R, 100G, and 100B, respectively, are incident on a dichroic prism 2112 from three directions. At the dichroic prism 2112, the light of R and the light of B are refracted at 90 degrees, whereas the light of G travels in a straight line. Thus, the dichroic prism 2112 combines the images of the respective colors. A composite image generated by the dichroic prism 2112 is incident on a projection lens 2114 via an optical path shifting element 230.
The projection lens 2114 enlarges and projects the composite image transmitted through the optical path shifting element 230, onto a screen Scr.
The optical path shifting element 230 shifts the composite image emitted from the dichroic prism 2112. More specifically, the optical path shifting element 230 shifts the image projected onto the screen Scr in the left-right direction and/or in the downward direction with respect to a projection surface.
Note that, while the transmitted images by the liquid crystal panels 100R and 100B are projected after being reflected by the dichroic prism 2112, the transmitted image by the liquid crystal panel 100G travels in a straight line and is projected. Thus, the respective transmitted images of the liquid crystal panels 100R and 100B are laterally inverted with respect to the transmitted image of the liquid crystal panel 100G.
For convenience of description, with the projection surface of the screen Scr viewed from the projection-type display apparatus 1, the left-right direction is defined as an X-axis and the up-down direction is defined as a Y-axis. Note that, of the left-right directions along the X-axis, the right direction is referred to as an X direction, and the left direction is referred to as a direction opposite to the X direction. Further, of the up-down directions along the Y-axis, the downward direction is referred to as a Y direction, and the upward direction is referred to as a direction opposite to the Y direction. The projection direction of the projection-type display apparatus 1 is defined as a Z direction.
Note that, in the first embodiment, the Y-axis is an example of a first axis, and the X-axis is an example of a second axis.
Video data Vid-in is supplied from a higher-level device such as a host device (not illustrated) in synchronization with a synchronization signal Sync. The video data Vid-in designates a gray scale level of a pixel in an image to be displayed for each of RGB, for example, by 8 bits.
Note that the pixel in the image designated by the video data Vid-in is referred to as a video pixel, data of the video pixel is referred to as pixel data, and the pixel in the composite image by the liquid crystal panels 100R, 100G, and 100B is referred to as a panel pixel. Further, the position of the panel pixel shifted by the optical path shifting element 230 and projected onto the screen Scr is referred to as a projection position.
In the composite image of the liquid crystal panels 100R, 100G, and 100B, the panel pixels are arrayed in a matrix in the vertical and lateral directions. In this embodiment, the array of the video pixels whose gray scale levels are designated by the video data Vid-in is twice as large as the array of the panel pixels combined by the liquid crystal panels 100R, 100G, or 100B, in both the vertical direction and the lateral direction.
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. Thus, the pixel, which is the minimum unit of the color image, can be divided into a red sub-pixel by the liquid crystal panel 100R, a green sub-pixel by the liquid crystal panel 100G, and a blue sub-pixel by the liquid crystal panel 100B. However, when there is no need to specify the colors of the sub-pixels in the liquid crystal panels 100R, 100G, and 100B, or, for example, when handling only the brightness as a problem, the sub-pixels do not need to be referred to as sub-pixels. Therefore, in the description herein, the panel pixel is also used as a display unit of the liquid crystal panels 100R, 100G, and 100B.
The synchronization signal Sync includes a vertical synchronization signal that instructs a start of vertical scanning of the video data Vid-in, a horizontal synchronization signal that instructs a start of horizontal scanning, and a clock signal that indicates a timing for one video pixel.
The display control circuit 20 includes a processing circuit 22, and conversion circuits 23R, 23G, and 23B.
The processing circuit 22 accumulates the video data Vid-in from the higher-level device for one or two or more frame periods, then reads the pixel data of the video pixel corresponding to the projection position by the optical path shifting element 230, and outputs the pixel data for each of RGB components. Note that, of pixel data V output from the processing circuit 22, the R component is referred to as pixel data Vad_R, the G component is referred to as pixel data Vad_G, and the B component is referred to as pixel data Vad_B.
In the projection-type display apparatus 1, the projection position changes for each unit period obtained by dividing one frame period into four, but eight of the projection positions can be set in eight unit periods in two consecutive frame periods. However, in this embodiment, the number of projection positions in the eight unit periods is set to be seven, as will be described below.
Each of the unit periods is a period for causing a user to visually recognize an image, achieved by reducing the resolution of an image for one frame period designated by the video data Vid-in to one fourth of the original resolution, as the composite image by the liquid crystal panels 100R, 100G, and 100B.
The processing circuit 22 controls the projection position by the optical path shifting element 230 in each unit period. More specifically, with respect to the optical path shifting element 230, the processing circuit 22 controls a shift in a direction along the X-axis using a control signal P_x, and controls a shift in a direction along the Y-axis using a control signal P_y.
Note that the projection position for each unit period, and which of the video pixels, designated by the video data Vid-id in correspondence to each of the projection positions, is expressed by the panel pixel will be described later in more detail.
Further, the processing circuit 22 also generates a control signal Ctr for controlling the liquid crystal panels 100R, 100G, and 100B for each unit period.
The conversion circuit 23R converts the pixel data Vad_R into a data signal Vid R of an analog voltage, and supplies it to the liquid crystal panel 100R. The conversion circuit 23G converts the pixel data Vad_G into a data signal Vid G of an analog voltage, and supplies it to the liquid crystal panel 100G. The conversion circuit 23B converts the pixel data Vad_B into a data signal Vid B of an analog voltage, and supplies it to the liquid crystal panel 100B.
Next, the liquid crystal panels 100R, 100G, and 100B will be described. The liquid crystal panels 100R, 100G, and 100B only differ in the color of incident light, that is, the wavelength, and otherwise have the same structure. Thus, the liquid crystal panels 100R, 100G, and 100B will be generally described below using a reference numeral 100 without specifying the color.
As illustrated in these drawings, in the liquid crystal panel 100, an element substrate 100a on which pixel electrodes 118 are provided and a counter substrate 100b on which a common electrode 108 is provided are bonded to each other by a seal material 90, so that electrode-formed surfaces thereof face each other with a constant gap therebetween, and liquid crystal 105 is sealed in the gap.
As the element substrate 100a and the counter substrate 100b, transmissive substrates such as glass or quartz substrates are used. As illustrated in
On the surface of the element substrate 100a facing the counter substrate 100b, the pixel electrodes 118 are formed by patterning a transparent conductive layer such as indium tin oxide (ITO), for example.
Further, various elements other than the electrodes are provided on the facing surface of the element substrate 100a and the facing surface of the counter substrate 100b, but are not illustrated in the drawings.
In the display region 10 of the liquid crystal panel 100, pixel circuits 110 are arrayed in a matrix. More specifically, in the display region 10, a plurality of scanning lines 12 are provided extending in the lateral direction in the drawing, and a plurality of data lines 14 are provided extending in the vertical direction, while the data lines 14 are electrically insulated from the scanning lines 12. The pixel circuits 110 are provided in a matrix so as to correspond to the intersections between the plurality of scanning lines 12 and the plurality of data lines 14.
When the number of the scanning lines 12 is m and the number of the data lines 14 is n, the pixel circuits 110 are arrayed in a matrix of m rows and n columns. m and n are each an integer of 2 or greater. With respect to the scanning lines 12 and the pixel circuits 110, in order to distinguish the rows of the matrix from each other, the rows may be referred as a 1st, 2nd, 3rd . . . (m−1)-th, and m-th row in ascending order from the top in the drawing. Similarly, with respect to the data lines 14 and the pixel circuits 110, in order to distinguish the columns of the matrix from each other, the columns may be referred as a 1st, 2nd, 3rd . . . (n−1)-th, and n-th column in ascending order from the left in the drawing.
The scanning line drive circuit 130 selects the scanning lines 12 one by one, for example, in order of the 1st, 2nd, 3rd . . . and m-th rows under the control of the display control circuit 20, and sets a scanning signal to the selected scanning line 12 to the H level. Note that the scanning line drive circuit 130 sets the scanning signals to the scanning lines 12 other than the selected scanning line 12, to the L level.
The data line drive circuit 140 latches one row of the data signals supplied from the circuit of the corresponding color, that is, from one of processing circuits 220R, 220G, or 220B, and in a period in which the scanning signal to the scanning line 12 is set to the H level, outputs the data signal to the pixel circuit 110 located at that scanning line 12 via the data line 14.
As illustrated in the drawing, 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, a gate node of the transistor 116 is coupled to the scanning line 12, a source node thereof is coupled to the data line 14, and a drain node thereof is coupled to the pixel electrode 118 having a square shape in plan view.
The common electrode 108 is provided commonly for all of the pixels, so as to face the pixel electrodes 118. A voltage LCcom is applied to the common electrode 108. The liquid crystal 105 is interposed between the pixel electrodes 118 and the common electrode 108, as described above. Thus, the liquid crystal element 120, in which the liquid crystal 105 is interposed between the pixel electrodes 118 and the common electrode 108, is formed for each of the pixel circuits 110.
Further, a storage capacitor 109 is provided in parallel with the liquid crystal element 120. One end of the storage capacitor 109 is coupled to the pixel electrode 118, while the other end thereof is coupled to a capacitor line 107. A temporally constant voltage, for example, the same voltage LCcom as the voltage applied to the common electrode 108, is applied to the capacitor line 107. Since the pixel circuits 110 are arrayed in the matrix in the lateral direction, which is the extending direction of the scanning lines 12, and in the vertical direction, which is the extending direction of the data lines 14, the pixel electrodes 118 included in the pixel circuits 110 are also arrayed in the lateral direction and the vertical direction.
In the scanning line 12 in which the scanning signal is set to the H level, the transistor 116 of the pixel circuit 110 provided corresponding to that scanning line 12 is turned on. Since the data line 14 and the pixel electrode 118 are electrically coupled to each other as a result of the transistor 116 being turned on, the data signal supplied to the data line 14 reaches the pixel electrode 118 through the transistor 116 that has been turned on. When the scanning line 12 is set to the L level, the transistor 116 is turned off, but the voltage of the data signal, which has reached the pixel electrode 118, is retained by capacitive properties of the liquid crystal element 120 and the storage capacitor 109.
As is well known, in the liquid crystal element 120, the liquid crystal molecular alignment changes in accordance with the electric field generated by the pixel electrode 118 and the common electrode 108. Thus, the liquid crystal element 120 has a transmittance corresponding to the effective value of the applied voltage.
Note that a region functioning as the pixel in the liquid crystal element 120, that is, a region having the transmittance corresponding to the effective value of the voltage is a region in which the pixel electrode 118 and the common electrode 108 overlap each other when the element substrate 100a and the counter substrate 100b are viewed in plan view. Since the pixel electrode 118 has a square shape in plan view, the shape of the pixel of the liquid crystal panel 100 is also a square shape.
Further, in this embodiment, it is assumed that the normally black mode is employed in which the transmittance increases as the voltage applied to the liquid crystal element 120 increases.
An operation of supplying the data signal to the pixel electrode 118 of the liquid crystal element 120 is performed in order of the 1st, 2nd, 3rd . . . and m-th rows in one unit period. As a result, a voltage corresponding to the data signal is retained in each of the liquid crystal elements 120 of the pixel circuits 110 arrayed in m rows and n columns, each of the liquid crystal element 120 comes to have a target transmittance, and the transmitted image of the corresponding color is generated by the liquid crystal elements 120 arrayed in m rows and n columns.
In this way, the transmitted image is generated for each of RGB, and the color image obtained by combining RGB is projected onto the screen Scr.
The pixel data Vad_R, Vad_G, and Vad_B of the video pixel output from the processing circuit 22 corresponding to one unit period are the pixel data of the video pixel corresponding to that unit period. Thus, in that unit period, a color composite image corresponding to a projection position is projected at that projection position.
As described above, the video pixels in the video data Vid-in are arrayed in 2m rows and 2n columns, which are twice as large in both the vertical direction and the lateral direction compared with the m rows and n columns in which the panel pixels are arrayed in the liquid crystal panels 100R, 100G, and 100B.
In other words, the array of the panel pixels is half the size of the array of the video pixels in both the vertical direction and the lateral direction. Thus, in this embodiment, in one frame period, one panel pixel is shifted at a total of four positions, namely, two positions in the vertical direction times two positions in the lateral direction, so that the one panel pixel is visually recognized as if it is indicating four of the video pixels designated by the video data Vid-in.
However, in a configuration in which the video pixels are expressed by simply shifting one panel pixel to the four positions in one frame period, the display quality may deteriorate as described below. Thus, in this embodiment, the projection position of one panel pixel is shifted in each of eight unit periods over two frame periods, and further, the direction in which the projection position is shifted for each of the unit periods in an odd-numbered frame period and the direction in which the projection position is shifted for each of the unit periods in an even-numbered frame period are set to be opposite to each other.
The odd-numbered frame period is divided into four unit periods. In order to distinguish the four unit periods in the odd-numbered frame period from each other, reference signs f1-1, f1-2, f1-3, and f1-4 are assigned in a chronological order for convenience. Similarly, the even-numbered frame period is divided into four unit periods. In order to distinguish the four unit periods in the even-numbered frame period, reference signs f2-1, f2-2, f2-3, and f2-4 are assigned in the chronological order for convenience.
Note that the number of unit periods included in each of the odd-numbered frame period and the even-numbered frame period, which is “4” in this case, is an example of an integer n of 2 or greater. Further, the odd-numbered frame period is an example of a first frame period, and the even-numbered frame period is an example of a second frame period. The unit periods f1-1 and f2-1 are examples of a first unit period, the unit periods f1-2 and f2-2 are examples of a second unit period, the unit periods f1-3 and f2-3 are examples of a third unit period, and the unit periods f1-4 and f2-4 are examples of a fourth unit period.
One frame period is a period in which one frame of the image designated by the video data Vid-in from the higher-level device is supplied. When the frequency of the vertical synchronization signal included in the synchronization signal Sync is 60 Hz, one frame period is 16.7 milliseconds corresponding to one cycle. In this case, the length of each of the unit periods is ¼ of the length of one frame period, which is 4.17 milliseconds.
The optical path shifting element 230 shifts the image projected onto the screen Scr in the X-axis and the Y-axis with respect to the projection surface. For convenience, an amount of the shift will be described in terms of the size of the pixel projected onto the screen Scr, that is, the size of the panel pixel.
Each of the control signals P_x and P_y has a level of one of three values of +A, 0, and −A, except for during a rear-end period of each of the unit periods f1-1 to f1-4 and f2-1 to f2-4. The levels of the control signals P_x and P_y change in the rear end period. The rear end period is a period corresponding to a vertical scanning flyback period.
Note that the level of the control signal P_x or P_y may be constant over two consecutive unit periods.
For convenience of description, the projection position in the period, other than the rear end period, of the unit period f1-1 in the odd-numbered frame period, that is, the projection position in the period in which the levels of the control signals P_x and P_y are 0 is set as a reference position.
When the level of the control signal P_x is +A, the optical path shifting element 230 shifts the projection position from the reference position by half of the panel pixel in the X direction, and when the level of the control signal P_x is −A, the optical path shifting element 230 shifts the projection position from the reference position by half of the panel pixel in the direction opposite to the X direction.
When the level of the control signal P_y is +A, the optical path shifting element 230 shifts the projection position from the reference position by half of the panel pixel in the Y direction, and when the level of the control signal P_y is −A, the optical path shifting element 230 shifts the projection position from the reference position by half of the panel pixel in the direction opposite to the Y direction.
Thus, for example, when the level of the control signal P_x is +A and the level of the control signal P_y is +A, the optical path shifting element 230 shifts the projection position from the reference position by half of the panel pixel in each of the X direction and the Y direction.
Note that the arrow illustrated in the rear end period of each of the unit periods in
Further, the shift of the projection position by the optical path shifting element 230 may not be performed according to the levels of the control signals P_x and P_y, and may be accompanied by a time delay.
Next, a description will be made as to which video pixel among the video pixels of the video data Vid-in is expressed by the panel pixel of the liquid crystal panel 100 in the odd-numbered frame period and the even-numbered frame period.
Note that a panel pixel expressing a video pixel means that the panel pixel is in a state of having a transmittance designated by the pixel data corresponding to that video pixel.
The left field in
Note that, in the left field of
In the right field of
Thus, for example, the shift direction from the projected pixel before the shift toward the projected pixel after the shift from the unit period f1-2 to the unit period f1-3 of the odd-numbered frame period is opposite to the shift direction from the projected pixel before the shift toward the projected pixel after the shift from the unit period f2-2 to the unit period f2-3 of the even-numbered frame period. Further, for example, the shift direction from the projected pixel before the shift toward the projected pixel after the shift from the unit period f1-3 to the unit period f1-4 of the odd-numbered frame period is also opposite to the shift direction from the projected pixel before the shift toward the projected pixel after the shift from the unit period f2-3 to the unit period f2-4 of the even-numbered frame period.
For convenience, the projection position in the unit period f1-1 of the odd-numbered frame period is set as the reference position. As illustrated in
In the rear end period (vertical flyback period) of the unit period f1-1, the optical path shifting element 230 shifts the projection position from the reference position in the unit period f1-1 indicated by the dashed line, in the upward direction in the drawing (direction opposite to the Y direction) by 0.5 panel pixels. In the next unit period f1-2, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels B11, B21, B31, B12, B22, B32, respectively.
In the rear end period of the unit period f1-2, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f1-2 indicated by the dashed line, in the left direction in the drawing (direction opposite to the X direction) by 0.5 panel pixels. In the next unit period f1-3, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels A11, A21, A31, A12, A22, and A32, respectively.
In the rear end period of the unit period f1-3, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f1-3 indicated by the dashed line, in the downward direction in the drawing (Y direction) by 0.5 panel pixels. In the next unit period f1-4, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels D11, D21, D31, D12, D22, and D32, respectively.
In the rear end period of the unit period f1-4, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f1-4 indicated by the dashed line, in the right direction in the drawing (X direction) by 0.5 panel pixels, thereby returning the projection position to the reference position. In the first unit period f2-1 in the even-numbered frame period, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels C11, C21, C31, C12, C22, and C32, respectively. In other words, a video pixel expressed by one panel pixel in the unit period 1-1 is the same as a video pixel expressed by the panel pixel in the unit period 2-1.
In the rear end period of the unit period f2-1, the optical path shifting element 230 shifts the projection position from the reference position in the unit period f2-1 indicated by the dashed line, in the downward direction in the drawing (Y direction) by 0.5 panel pixels. In the next unit period f2-2, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels B12, B22, B32, B13, B23, and B33, respectively.
In the rear end period of the unit period f2-2, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f2-2 indicated by the dashed line, in the right direction in the drawing (X direction) by 0.5 panel pixels. Further, in the unit period f2-3, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels A22, A32, A42, A23, A33, and A42, respectively.
In the rear end period of the unit period f2-3, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f2-3 indicated by the dashed line, in the upward direction in the drawing (direction opposite to the Y direction) by 0.5 panel pixels. In the next unit period f2-4, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels D21, D31, D41, D22, D32, and D42, respectively.
In the rear end period of the unit period f2-4, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f2-4 indicated by the dashed line, in the left direction in the drawing (direction opposite to the X direction) by 0.5 panel pixels, thereby returning the projection position to the reference position.
In this embodiment, even when a specific pattern appears in the video image designated by the video data Vid-in, deterioration in display quality is suppressed. This point will be described next.
Note that, when the specific pattern is the still image, the video pixels in the odd-numbered frame period are the same as those in the even-numbered frame period. The “white video pixel” herein is a video pixel in which the highest (or nearly highest) gray scale level is designated for each of the three primary colors of red, green, and blue. Further, the “black video pixel” referred to here is a video pixel in which the lowest (or nearly lowest) gray scale level is designated for each of the three primary colors of red, green, and blue.
Note that, in
In
Before referring to that deterioration in display quality is suppressed in the first embodiment, a first comparative example will be described.
In the first embodiment, the frame periods are distinguished between the odd-numbered frame period and the even-numbered frame period, and the 2 times 2 video pixels expressed by one panel pixel are different between the odd-numbered frame period and the even-numbered frame period. In the first comparative example, the frame periods are not distinguished between the odd-numbered frame period and the even-numbered frame period. Thus, in the first comparative example, a configuration is adopted in which a single frame period is divided into four unit periods, and one panel pixel expresses 2 times 2 video pixels in each of the four unit periods. In other words, the first comparative example has a configuration in which only one of the odd-numbered frame period or the even-numbered frame period is employed in the first embodiment. Here, the first comparative example includes only the odd-numbered frame period for the sake of convenience. In the first comparative example, for example, the panel pixel p22 expresses the video pixel C22 in the unit period f1-1, the video pixel B22 in the unit period f1-2, the video pixel C22 in the unit period f1-3, and the video pixel D22 in the unit period f1-4.
The upper field in
The lower field in
In this case, as illustrated in the lower field in
In the first embodiment, the visibility of the projected pixel displayed in black at the rate of four times per eight unit periods is equivalent to the visibility of the projected pixel displayed in black at the rate of twice per four unit periods in the first comparative example. Further, in the first embodiment, the visibility of the projected pixel displayed in black at the rate of twice per eight unit periods is equivalent to the visibility of the projected pixel displayed in black at the rate of once per four unit periods in the first comparative example. Thus, in the first comparative example and the first embodiment, there is no difference in the visibility of the projected pixels displayed in black.
However, in the first comparative example, the projected pixel displayed in gray, which is generated at the rate of once per four unit periods, appears at the same position in the next frame period. Thus, the projected pixel displayed in gray appears twice at the same position, every eight unit periods.
On the other hand, in the first embodiment, the projected pixel displayed in gray, which is generated at the rate of once per eight unit periods, appears at different positions. For this reason, the projected pixel displayed in gray appears once every eight unit periods, at a different position each time. In other words, in the first embodiment, since the projected pixels displayed in gray, which are the transition portions, are displayed in a more dispersed manner compared with the first comparative example, it is possible to suppress deterioration in display quality when the specific pattern is displayed.
In the first embodiment, when the specific pattern is displayed, it is possible to suppress deterioration in display quality and reduce flickering. However, before referring to this point, a second comparative example will be described.
In the first embodiment, as illustrated in
As illustrated in
The second comparative example and the first embodiment are the same in that the panel pixel p11 expresses the video pixels C11, B11, A11, and D11 in this order in the unit periods f1-1 to f1-4 of the odd-numbered frame period. In the second comparative example, as illustrated in the upper field in
Here, when focusing on the video pixels B11 and B12 among the video pixels expressed by the panel pixel p11, in the second comparative example, the panel pixel p11 expresses the video pixel B11 in the second unit period f1-2 in the odd-numbered frame period, and expresses the video pixel B12 in the fourth unit period f2-4 in the next even-numbered frame period. Thus, after the panel pixel p11 expresses the video pixel B11, six unit periods elapse before the panel pixel p11 expresses the video pixel B12. Subsequently, two unit periods elapse before the panel pixel p11 expresses the video pixel B11 once again. Thereafter, this process is repeated. Therefore, in the second comparative example, the time interval between when the video pixel B11 is expressed by the panel pixel p11 and when the video pixel B12 is expressed by the panel pixel p11 is not uniform.
In the case of the still image, the video pixels B11 and B12 are highly correlated with each other in terms of the gray scale level. Therefore, if the time interval between when the video pixel B11 is expressed by the panel pixel p11 and when the video pixel B12 is expressed by the panel pixel p11 is not uniform, flickering, that is, blinking is likely to be visually recognized. Video pixels expressed in such a manner, namely, expressed at the non-uniform time intervals are all the video pixels except for the video pixels expressed in the unit period f1-1 of the odd-numbered frame period and in the unit period f2-1 of the even-numbered frame period, and correspond to three quarters (¾) of all the video pixels.
On the other hand, in the first embodiment, the panel pixel p11 expresses the video pixel B11 in the second unit period f1-2 in the odd-numbered frame period, and expresses the video pixel B12 in the second unit period f2-2 in the even-numbered frame period. Thus, after the panel pixel p11 expresses the video pixel B11, four unit periods elapse before the panel pixel p11 expresses the video pixel B12.
Subsequently, two unit periods elapse before the panel pixel p11 expresses the video pixel B11 once again. Thereafter, this process is repeated. Thus, in the first embodiment, the time interval between when the video pixel B11 is expressed by the panel pixel p11 and when the video pixel B12 is expressed by the panel pixel p11 becomes uniform. In the first embodiment, with respect to the other video pixels expressed by the panel pixel p11 including C11, A11/A22, and D11/D21 as well, the time interval becomes uniform in a similar manner. In other words, in the first embodiment, all of the video pixels are expressed at the uniform time intervals. Therefore, in the first embodiment, it is possible to reduce flickering as compared with the second comparative example.
Next, the projection-type display apparatus 1 according to a second embodiment will be described. The second embodiment is different from the first embodiment in that the orders in which the video pixels are expressed by the panel pixels are changed both in the unit periods f1-1 to f1-4 of the odd-numbered frame period and the unit periods f2-1 to f2-4 of the even-numbered frame period, and the shift directions of the projection position are also changed in accordance with the orders.
Although the waveforms of the control signals P_x and P_y supplied to the optical path shifting element 230 are different from the waveforms illustrated in
As illustrated in
In other words, in the odd-numbered frame period, the panel pixel p11 expresses the 2 times 2 video pixels included in the frame Bk1 in the order of firstly the video pixel C11, secondly the video pixel A11 positioned diagonally to the video pixel C11, thirdly the video pixel B11 positioned adjacent to the video pixel C11 in the X direction, and fourthly the video pixel D11 positioned diagonally to the video pixel B11.
Therefore, also in the second embodiment, the order in which the panel pixel p11 expresses the video pixels in the frame Bk1 and the order in which the panel pixel p11 express the video pixels in the frame Bk2 have a point symmetry relationship with respect to the video pixel C11 as in the first embodiment.
As illustrated in
In the rear end period of the unit period f1-1, the optical path shifting element 230 shifts the projection position from the reference position in the unit period f1-1 indicated by the dashed line, in the diagonally upper left direction in the drawing. Note that the diagonally upper left direction herein is a composite direction obtained by making the shifts by 0.5 panel pixels in the direction opposite to the X direction, and by 0.5 panel pixels in the direction opposite to the Y direction. Further, a diagonally upper left axis, specifically, an axis obtained by rotating the Y-axis in the counterclockwise direction by 45 degrees is an example of a third axis.
In the next unit period f1-2, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched image pixels A11, A21, A31, A12, A22, and A32, respectively.
In the rear end period of the unit period f1-2, the optical path shift device 230 shifts the projection position from the projection position in the unit period f1-2 indicated by the dashed line, in the right direction in the drawing (X direction) by 0.5 panel pixels. In the next unit period f1-3, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched image pixels B11, B21, B31, B12, B22, B32, respectively.
In the rear end period of the unit period f1-3, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f1-3 indicated by the dashed line, in the diagonally lower left direction in the drawing. Note that the diagonally lower left direction herein is a composite direction obtained by making the shifts by 0.5 panel pixels in the direction opposite to the X direction, and by 0.5 panel pixels in the Y direction. Further, a diagonally lower left axis, specifically, an axis obtained by rotating the Y-axis in the clockwise direction by 45 degrees is an example of a fourth axis. In the next unit period f1-4, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels D11, D21, D31, D12, D22, and D32, respectively.
In the rear end period of the unit period f1-4, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f1-4 indicated by the dashed line, in the right direction in the drawing (X direction) by 0.5 panel pixels, thereby returning the projection position to the reference position. In the first unit period f2-1 in the even-numbered frame period, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels C11, C21, C31, C12, C22, and C32, respectively. In other words, also in the second embodiment, the video pixel expressed by one panel pixel in the unit period 1-1 is the same as the video pixel expressed by the panel pixel in the unit period 2-1 as in the first embodiment.
In the rear end period of the unit period f2-1, the optical path shifting element 230 shifts the projection position from the reference position in the unit period f2-1 indicated by the dashed line, in the diagonally lower right direction in the drawing. Note that the diagonally lower right direction herein is a composite direction obtained by making the shifts by 0.5 panel pixels in the direction opposite to the X direction, and by 0.5 panel pixels in the direction opposite to the Y direction.
In the next unit period f2-2, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched image pixels A22, A32, A42, A23, A33, and A43, respectively.
In the rear end period of the unit period f2-2, the optical path shift device 230 shifts the projection position from the projection position in the unit period f2-2 indicated by the dashed line, in the left direction in the drawing (direction opposite to the X direction) by 0.5 panel pixels. Further, in the next unit period f2-3, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched image pixels B12, B22, B32, B13, B23, and B33, respectively.
In the rear end period of the unit period f2-3, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f2-3 indicated by the dashed line, in the diagonally upper right direction in the drawing. Note that the diagonally upper right direction herein is a composite direction obtained by making the shifts by 0.5 panel pixels in the direction opposite to the X direction, and by 0.5 panel pixels in the direction opposite to the Y direction.
In the next unit period f2-4, the panel pixels p11, p21, p31, p12, p22, and p32 express the hatched video pixels D21, D31, D41, D22, D32, and D42, respectively.
In the rear end period of the unit period f2-4, the optical path shifting element 230 shifts the projection position from the projection position in the unit period f2-4 indicated by the dashed line, in the left direction in the drawing (direction opposite to the X direction) by 0.5 panel pixels, thereby returning the projection position to the reference position.
Next, in the second embodiment, even when the specific pattern appears in the image designated by the video data Vid-in, deterioration in display quality is suppressed. This point will be described next. Note that the specific pattern herein is the still image illustrated in
Note that, in
In
In the first comparative example illustrated in the upper field in
On the other hand, in the second embodiment, as illustrated in
Thus, also in the second embodiment, it is possible to suppress deterioration in display quality when the specific pattern is displayed.
Note that, although, in the second embodiment, two of the projected pixels displayed in gray, which are generated at the rate of once per eight unit periods, are continuously displayed in the Y direction, the display quality is unlikely to deteriorate because gray is a color close to white.
The lower field in
In the second embodiment, the panel pixel p11 sequentially expresses the video pixels C11, A11, B11, and D11 in this order in the unit periods f1-1 to f1-4 of the odd-numbered frame period, and sequentially expresses the video pixels C11, A22, B12, and D21 in this order in the unit periods f2-1 to f2-4 of the even-numbered frame period.
Here, when focusing on the video pixels B11 and B12 among the video pixels expressed by the panel pixel p11, the panel pixel p11 expresses the video pixel B11 in the third unit period f1-3 in the odd-numbered frame period, and expresses the video pixel B12 in the third unit period f2-3 in the even-numbered frame period. Thereafter, this process is repeated. Thus, in the second embodiment, the time interval between when the video pixel B11 is expressed by the panel pixel p11 and when the video pixel B12 is expressed by the panel pixel p11 becomes uniform. In the second embodiment, with respect to the other video pixels expressed by the panel pixel p11 including C11, A11/A22, and D11/D21 as well, the time interval becomes uniform in a similar manner. In other words, in the second embodiment, all of the video pixels are expressed at the uniform time intervals. Thus, in the second embodiment, it is possible to reduce flickering in the same manner as in the first embodiment.
In the first embodiment and the second embodiment described above (hereinafter referred to as “embodiments and the like”), various modifications or applications are possible as described below.
In the embodiments and the like, a configuration is adopted in which one frame period is divided into four unit periods. In other words, when n is the number of unit periods included in one frame period, the description above is given using n=4 as an example. n is not limited to “4”, and may be “2” or greater.
In the embodiments and the like, as the specific pattern, as an example of the still image of the diagonal line formed by the black video pixels and angled at 45 degrees with the white background, the line extending in the upper right direction is used. However, it is also possible to suppress deterioration in display quality in a similar manner, even with a line extending in the upper left direction. Further, even when a diagonal line formed by white video pixels and angled at 45 degrees with a black background is used, it is possible to suppress deterioration in display quality in a similar manner.
In the embodiments and the like, the period in which the levels of the control signals P_x and P_y supplied to the optical path shifting element 230 change is the rear end period corresponding to the vertical scanning flyback period in each of the unit periods f1-1 to f1-4 and f2-1 to f2-4. However, as described above, the shift of the projection position by the optical path shifting element 230 may not be performed according to the levels of the control signals P_x and P_y, but may be accompanied by the time delay. In such a case, the level changes of the control signals P_x and P_y may be started in anticipation of the time delay, so that the image formed by the liquid crystal panel 100 in a unit period is shifted to a projection position corresponding to that unit period, for example.
For example, the following aspects of the present disclosure are understood from the embodiments illustrated above.
A projection-type display apparatus according to an aspect (a first aspect) includes a liquid crystal panel including a panel pixel, an optical path shifting element configured to shift a position of a projected pixel projected from the panel pixel in each of n unit periods from a first unit period to an n-th unit period included in one frame period, n being an integer of two or greater, and a display control circuit configured to control the liquid crystal panel and the optical path shifting element. The display control circuit supplies a data signal corresponding to pixel data constituting video data, to the panel pixel in each of the unit periods, controls the shift of the position of the projected pixel with respect to the optical path shifting element in each of the unit periods, supplies, to the liquid crystal panel, the data signal corresponding to the same pixel data and controls the position of the projected pixel to be at a same position in each of an initial first unit period of the n unit periods in a first frame period and an initial first unit period of the n unit periods in a second frame period subsequent to the first frame period, and controls the optical path shifting element to cause a shift direction from the position of the projected pixel before the shift to the position of the projected pixel after the shift from a second unit period to the n-th unit period of the first frame period to be opposite to the shift direction from the position of the projected pixel before the shift to the position of the projected pixel after the shift from the second unit period to the n-th unit period of the second frame period.
According to the first aspect, even when a specific display pattern appears in an image designated by the video data, deterioration in display quality can be suppressed, and flickering can be made less conspicuous.
In a specific aspect (a second aspect) of the first aspect, the pixel data constituting the video data is arrayed along a first axis and a second axis, and the optical path shifting element shifts the projected pixel in a direction along the first axis or a direction along the second axis in each of the unit periods.
According to the second aspect, since the direction in which the optical path shifting element shifts the projected pixel is the direction along the first axis or the second axis, a shift amount of the projected pixel in each of the unit periods can be made uniform.
In a specific aspect (a third aspect) of the second aspect, n is 4, and the optical path shifting element shifts the position of the projected pixel in one direction along the first axis from the first unit period to the second unit period of the first frame period, in one direction along the second axis from the second unit period to the third unit period of the first frame period, in the other direction along the first axis from the third unit period to the fourth unit period of the first frame period, and in the other direction along the second axis from the fourth unit period of the first frame period to the first unit period of the second frame period.
According to the third aspect, since the projected pixel is positioned at four points in the first frame period, the resolution of the projected image visually recognized by a user is artificially increased so as to be four times larger than the resolution of the liquid crystal panel. Note that, in a fourth aspect, if the four points of the projected pixel in the first frame period are shifted, for example, in the counterclockwise direction, the four points of the projected pixel in the second frame period are shifted in the counterclockwise direction. Further, one direction along an axis means one of two directions along the axis, and the other direction along the axis means the other direction of the two directions along the axis.
In another specific aspect (the fourth aspect) of the first aspect, the pixel data constituting the video data is arrayed along a first axis and a second axis, and in each of the unit periods, the optical path shifting element shifts the position of the projected pixel in a direction along the first axis, a direction along a third axis intersecting the first axis and the second axis, or a direction along a fourth axis intersecting the first axis, the second axis, and the third axis.
According to the fourth aspect, even when the specific pattern appears in the image designated by the video data, deterioration in display quality is suppressed, and flickering can be made less conspicuous. Note that the third axis and the fourth axis are specifically diagonal axes with respect to the first axis or the second axis.
In a specific aspect (a fifth aspect) of the fourth aspect, n is 4, and the optical path shifting element shifts the position of the projected pixel in one direction along the third axis from the first unit period to the second unit period of the first frame period, in one direction along the first axis from the second unit period to the third unit period of the first frame period, in one direction along the fourth axis from the third unit period to the fourth unit period of the first frame period, and in one direction along the first axis from the fourth unit period of the first frame period to the first unit period of the second frame period.
According to the fifth aspect, since the projected pixel is positioned at four points in the first frame period, the resolution of the projected image visually recognized by the user is artificially increased so as to be four times larger than the resolution of the liquid crystal panel.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-137622 | Aug 2022 | JP | national |
