Liquid crystal display device, method for controlling liquid crystal display device, and electronic apparatus

Abstract

To suppress a domain while suppressing blurring of black.SOLUTION: The present invention adds a first correction to pixel data constituting video data on the basis of the grayscale level of grayscale data of panel pixels surrounding pixel data, and detects a boundary where a bright panel pixel whose grayscale level designated by pixel data corrected by first correction is higher than or equal to a first threshold and a dark panel pixel which is lower than or equal to a second threshold are adjacent to each other. The present invention further brings the grayscale level designated by the pixel data of the first bright panel pixel corrected by first correction closer to the first threshold when there is a first boundary where the grayscale level designated by the pixel data of the bright panel pixel corrected by first correction, out of the bright panel pixel pertaining to the detected boundary, is higher than or equal to a third threshold, makes second correction for bringing the grayscale level designated by the pixel data of the first dark panel pixel corrected by first correction to the second threshold, and then supplies a data signal corresponding to the corrected grayscale level to the panel pixel in the first bright panel pixel and the first dark panel pixel adjacent to each other across the first boundary.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal display device, a method for controlling a liquid crystal display device, and electronic equipment. [Background technology]

[0002] As LCD panels have become smaller and higher definition in recent years, the gap between pixel electrodes has become narrower, and the influence of the electric field generated between adjacent pixel electrodes, i.e., the electric field parallel to the substrate surface (lateral electric field), cannot be ignored. Specifically, the lateral electric field causes poor alignment of the liquid crystal, i.e., domains, which are visually recognized as display defects. For this reason, when it is expected that the horizontal electric field will become strong and cause display defects due to domains, a technique has been proposed in which the video data supplied from a higher-level device is corrected to reduce the difference in voltage applied to adjacent pixel electrodes. This type of correction is sometimes called domain correction (see, for example, the description in Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-170235 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above technique has a problem in that when domain correction is performed, a phenomenon known as black floating occurs. [Means for solving the problem]

[0005] In order to solve the above problem, a projection type display device according to one aspect of the present disclosure includes a liquid crystal panel having panel pixels and a display control circuit that controls the liquid crystal panel, wherein video data is composed of pixel data corresponding to the panel pixels, the pixel data specifying the gradation levels of the panel pixels, the display control circuit performing a first correction on each pixel data that constitutes the video data based on the gradation levels of the gradation data of panel pixels surrounding each pixel data, and classifying the gradation levels specified by the first corrected pixel data as bright panel pixels whose gradation levels are equal to or higher than a first threshold value and dark panel pixels whose gradation levels are equal to or lower than a second threshold value. and a first boundary where the gradation level specified by the pixel data of the first corrected bright panel pixel is equal to or higher than a third threshold value among the bright panel pixels associated with the detected boundary, a second correction is performed on a first bright panel pixel and a first dark panel pixel adjacent to each other across the first boundary, in which the gradation level specified by the pixel data of the first corrected first bright panel pixel approaches the first threshold value and the gradation level specified by the pixel data of the first corrected first dark panel pixel approaches the second threshold value, and a data signal corresponding to the corrected gradation level is supplied to the panel pixels.

[0006] In order to solve the above problem, a projection-type display device according to another aspect of the present disclosure includes a liquid crystal panel having panel pixels and a display control circuit that controls the liquid crystal panel, wherein video data is composed of pixel data corresponding to the panel pixels, and the pixel data specifies the gradation levels of the panel pixels; the display control circuit detects boundaries between adjacent bright panel pixels whose gradation levels specified by the pixel data that make up the video data are equal to or greater than a first threshold and adjacent dark panel pixels whose gradation levels are equal to or less than a second threshold; the display control circuit detects first and second boundaries; when the first boundary is defined as the dark panel pixel adjacent to a greater number of bright panel pixels than the dark panel pixels and the second boundary is defined as the dark panel pixel adjacent to a lesser number of bright panel pixels than the dark panel pixels, the display control circuit makes a correction amount for the pixel data of the bright panel pixels associated with the first boundary smaller than a correction amount for the pixel data of the bright panel pixels associated with the second boundary, and makes a correction amount for the pixel data of the dark panel pixels associated with the first boundary larger than a correction amount for the pixel data of the dark panel pixels associated with the second boundary.

[0007] In order to solve the above-described problems, a control method for a projection-type display device according to another aspect of the present disclosure is a control method for a liquid crystal display device including a liquid crystal panel having panel pixels and a display control circuit that controls the liquid crystal panel, wherein video data is composed of pixel data corresponding to the panel pixels, and the pixel data specifies a gradation level of the panel pixels, and the display control circuit performs a first correction on each pixel data that constitutes the video data based on the gradation levels of gradation data of panel pixels surrounding each pixel data, and determines whether the gradation level specified by the first-corrected pixel data is equal to or greater than a first threshold value, and whether the panel pixels are bright panel pixels. A boundary between an adjacent dark panel pixel and a bright panel pixel having a gradation level equal to or lower than a threshold is detected, and if there is a first boundary among the bright panel pixels associated with the detected boundary where the gradation level specified by the pixel data of the first corrected bright panel pixel is equal to or higher than a third threshold, a second correction is performed on the first bright panel pixel and the first dark panel pixel adjacent to each other across the first boundary, bringing the gradation level specified by the pixel data of the first corrected first bright panel pixel closer to the first threshold and bringing the gradation level specified by the pixel data of the first corrected first dark panel pixel closer to the second threshold, and a data signal corresponding to the corrected gradation level is supplied to the panel pixel. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a projection display device to which a liquid crystal panel according to an embodiment is applied. [Figure 2] FIG. 1 is a block diagram showing a configuration of a projection display device. [Figure 3] FIG. 1 is a perspective view showing a configuration of a liquid crystal panel in a projection display device. [Figure 4] FIG. 2 is a cross-sectional view showing the structure of a liquid crystal panel. [Figure 5] FIG. 2 is a block diagram showing the electrical configuration of a liquid crystal panel. [Figure 6] FIG. 2 is a diagram showing the configuration of a pixel circuit in a liquid crystal panel. [Figure 7] FIG. 10 is a diagram showing an example of the VT characteristic of a liquid crystal element. [Figure 8]FIG. 2 is a diagram illustrating domains in a liquid crystal panel. [Figure 9] FIG. 2 is a diagram illustrating an example of a processing circuit according to an embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a coefficient matrix of a filter processing circuit in the processing circuit. [Figure 11] FIG. 10 is a diagram illustrating an example of a change in gradation level. [Figure 12] FIG. 10 is a diagram illustrating an example of a change in gradation level. [Figure 13] FIG. 10 is a diagram illustrating an example of a change in gradation level. [Figure 14] 10 is a flowchart showing the operation of the processing circuit. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, liquid crystal display devices according to embodiments will be described with reference to the drawings. In each drawing, the dimensions and scale of each part are appropriately different from those of the actual device. Furthermore, the embodiments described below are preferred specific 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.

[0010] FIG. 1 is a diagram showing the optical configuration of a projection display device 1 that uses a liquid crystal panel according to an embodiment. As shown in the figure, the projection display device 1 includes liquid crystal panels 100R, 100G, and 100B. A lamp unit 2102 made up of a white light source such as a halogen lamp is provided inside the projection display device 1. Projection light emitted from the lamp unit 2102 is separated into three primary colors, red (R), green (G), and blue (B), by three mirrors 2106 and two dichroic mirrors 2108 disposed inside the projection display device 1. Of these, the R light enters the liquid crystal panel 100R, the G light enters the liquid crystal panel 100G, and the B light enters the liquid crystal panel 100B. 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.

[0011] The liquid crystal panel 100R has pixel circuits arranged in a matrix, as will be described later. In the pixel circuits, the transmittance of light emitted from the liquid crystal elements is controlled based on a data signal corresponding to R. That is, in the liquid crystal panel 100R, the light emitted from the liquid crystal elements functions as the smallest unit of an image. Through this control, the liquid crystal panel 100R generates an R transmission image based on the data signal corresponding to R. Similarly, the liquid crystal panel 100G generates a G transmission image based on the data signal corresponding to G, and the liquid crystal panel 100B generates a B transmission image based on the data signal corresponding to B.

[0012] 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 formed by the dichroic prism 2112 is incident on the projection lens 2114. The projection lens 2114 enlarges and projects the combined image formed by the dichroic prism 2112 onto the screen Scr.

[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 in a left-right inverted relationship with respect 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 and the above-mentioned liquid crystal panels 100R, 100G, and 100B.

[0015] Video data Vid_in is supplied to the display control circuit 20 in synchronization with a synchronization signal Sync from a higher-level device such as a host device (not shown). The video data Vid_in is data representing an image to be displayed on the projection display device 1, and more specifically, specifies the gradation level of the pixels of the image, 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 pixel data, but in some cases, no distinction is made between video pixels and pixel data. Furthermore, pixels before or after synthesis by the liquid crystal panels 100R, 100G, or 100B are referred to as panel pixels. When video pixels and panel pixels correspond one-to-one, as in this embodiment, there is no need to distinguish between video pixels and panel pixels. 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 pixel of video data.

[0017] In this embodiment, the color image projected onto the screen Scr is expressed by superimposing the transmitted images of the liquid crystal panels 100R, 100G, and 100B. Therefore, the pixel, which is the smallest unit of a color image, can be divided into a red panel pixel of the liquid crystal panel 100R, a green panel pixel of the liquid crystal panel 100G, and a blue panel pixel of the liquid crystal panel 100B. Strictly speaking, the red panel pixel, green panel pixel, and blue panel pixel should be referred to as sub-pixels, but in this description they will be referred to as panel pixels as described above.

[0018] The display control circuit 20 includes a control circuit 21, and processing circuits 22R, 22G, and 22B. The control circuit 21 generates a control signal Ctr for controlling the liquid crystal panels 100R, 100G, and 100B. The processing circuits 22R, 22G, and 22B will be described in detail later, but the processing circuit 22R processes R component video data Va_R out of the video data Vid_in, converts it into an analog data signal Vid_R, and supplies it to the liquid crystal panel 100R. Similarly, the processing circuit 22G processes the G component video data Va_G of the video data Vid_in, converts it into an analog data signal Vid_G, and supplies it to the liquid crystal panel 100G. The processing circuit 22B processes the B component video data Va_B of the video data Vid_in, converts it into an analog data signal Vid_B, and supplies it to the liquid crystal panel 100B.

[0019] The liquid crystal panel 100R, 100G or 100B and a processing circuit that supplies data signals to the liquid crystal panel constitute a liquid crystal display device.

[0020] Next, the liquid crystal panels 100R, 100G, and 100B will be described. The liquid crystal panels 100R, 100G, and 100B have a common structure, with the only difference being the color of the light incident thereon, i.e., the wavelength. Therefore, when describing the liquid crystal panels 100R, 100G, and 100B generally without specifying the color, they will be referred to as 100.

[0021] FIG. 3 is a diagram showing a main part of the liquid crystal panel 100, and FIG. 4 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.

[0022] 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. 3, 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.

[0023] 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).

[0024] 5 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.

[0025] 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 in the horizontal X direction in the figure, and a plurality of data lines 14 are provided extending in the vertical Y direction and are 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.

[0026] 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.

[0027] 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 processing circuits 22R, 22G, or 22B for one row, and outputs them via the data line 14 to the pixel circuit 110 located on the scanning line 12 during the period when the scanning signal to the scanning line 12 is at H level.

[0028] FIG. 6 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 is approximately square in plan view.

[0029] 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 X direction, which is the extension direction of the scanning lines 12, and the Y 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 the X direction and the Y direction.

[0030] 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.

[0031] 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 having a 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 is approximately square in a plan view, the shape of the pixel formed by the liquid crystal panel 100 is also approximately 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.

[0032] The operation of supplying data signals to the pixel electrodes 118 of the liquid crystal elements 120 is executed in the order of the first, second, third, ..., mth rows during each horizontal scanning period. 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.

[0033] Here, the domains in the liquid crystal panel 100 will be described.

[0034] FIG. 7 is a diagram showing an example of the applied voltage-transmittance characteristics (VT characteristics) of the liquid crystal element 120 in the normally black mode. In the normally black mode, a high gradation level is specified, and in panel pixels (bright panel pixels) with high transmittance, a high voltage is applied to the liquid crystal element 120. On the other hand, a low gradation level is specified, and in panel pixels (dark panel pixels) with low transmittance, a low voltage is applied to the liquid crystal element 120.

[0035] For convenience, the bright panel pixel and the dark panel pixel are defined as follows. A bright panel pixel is a panel pixel whose transmittance is Trh when the voltage applied to the liquid crystal element 120 is VH or higher. A dark panel pixel is a panel pixel whose transmittance is Trl when the voltage applied to the liquid crystal element 120 is VL or lower. Here, for VH and VL, VH>VL are in a relationship.

[0036] When the voltage applied to the liquid crystal element 120 is VH, the gradation level specified by the pixel data of the panel pixel is a first threshold value, which will be described later. When the voltage applied to the liquid crystal element 120 is VL, the gradation level specified by the pixel data of the panel pixel is a second threshold value, which will be described later. In other words, when the gradation level is equal to or higher than the first threshold, the voltage applied to the liquid crystal element 120 becomes equal to or higher than VH, and the panel pixel of the liquid crystal element 120 becomes a bright panel pixel. When the gradation level is equal to or lower than the second threshold, the voltage applied to the liquid crystal element 120 becomes equal to or lower than VL, and the panel pixel of the liquid crystal element 120 becomes a dark panel pixel.

[0037] As shown in Figure 8, in liquid crystal panel 100, when panel pixel L with high transmittance, i.e., a high voltage applied to liquid crystal element 120, and panel pixel D with low transmittance, i.e., a low voltage applied to liquid crystal element 120, are adjacent to each other, the voltage difference between the pixel electrodes 118 becomes large, the lateral electric field generated in the direction along the substrate surface becomes large, and the orientation of liquid crystal molecules becomes disordered near the boundary Edg between the two panel pixels, i.e., a domain is likely to occur. Generally, the greater the voltage difference between pixel electrodes 118, the greater the degree of domains that occur near the boundary between two adjacent panel pixels. Panel pixels in which domains occur do not have a transmittance that corresponds to the grayscale level, which can cause a decrease in display quality.

[0038] Therefore, if we are only concerned with suppressing display defects caused by domains, when it is expected that panel pixel L with a high applied voltage and panel pixel D with a low applied voltage are adjacent to each other, it should be sufficient to make corrections to reduce the lateral electric field generated in pixel electrode 118 of panel pixel L and pixel electrode 118 of panel pixel D.

[0039] With such a simple correction, the same processing is performed for both the boundary where there are more bright panel pixels L than dark panel pixels D and the boundary where there are more dark panel pixels D than bright panel pixels L, resulting in the following problems: That is, in the case of a boundary where there are more dark panel pixels D than bright panel pixels L, applying too strong a correction can result in a trade-off such as floating black, so the amount of correction must be reduced to avoid affecting the overall display quality. On the other hand, reducing the amount of correction also poses the problem of weakening the correction for boundaries where there are more bright panel pixels L than dark panel pixels D. Here, the term "floating black" refers to a phenomenon in which a panel pixel becomes brighter than the transmittance specified by the gradation level, and the pixel appears as if it is floating black.

[0040] In FIG. 8, the bright panel pixel L and the dark panel pixel D are used for the purpose of explanation only, and are unrelated to the bright panel pixel Lp and the dark panel pixel Dp described in the explanation of FIG.

[0041] In this embodiment, in order to suppress domains while suppressing floating black, the processing circuits 22R, 22G, and 22B perform the following corrections. Note that the processing circuits 22R, 22G, and 22B perform the same corrections, so the processing circuit 22R will be used as a representative here.

[0042] As a first process, the processing circuit 22R smoothes the gradation levels of pixels specified by pixel data of the R component video data Va_R in the video data Vid_in. Note that smoothing the gradation levels refers to a process of reducing the difference in gradation levels between adjacent panel pixels. As the second process, the processing circuit 22R detects, after smoothing, a boundary where a bright panel pixel having a gradation level equal to or higher than a first threshold and a dark panel pixel having a gradation level equal to or lower than a second threshold are adjacent in the X direction or the Y direction. In the third process, the processing circuit 22R determines whether the gradation level of the detected bright panel pixel associated with the boundary is equal to or greater than a third threshold value. The panel pixel associated with the boundary refers to a bright panel pixel or a dark panel pixel adjacent to each other across the boundary. As a fourth process, if the gradation level of the bright panel pixel related to the detected boundary is equal to or higher than the third threshold, the processing circuit 22R performs a correction to bring the gradation level of the bright panel pixel related to the boundary closer to the first threshold and the gradation level of the dark panel pixel related to the boundary closer to the second threshold.

[0043] On the other hand, if the gradation levels of the panel pixels not related to the boundary and the bright panel pixels related to the boundary are less than the third threshold, the processing circuit 22R outputs the smoothed gradation levels of the panel pixels related to the boundary as is as the fifth processing. The processing circuit 22R converts the grayscale levels that have been subjected to the fourth or fifth processing into an analog data signal Vid_R as a sixth processing, and supplies the analog data signal Vid_R to the liquid crystal panel 100R.

[0044] The processing circuit 22G also converts the G component video data Va_G into an analog data signal Vid_G through a similar process and supplies it to the liquid crystal panel 100G. The processing circuit 22B also converts the B component video data Va_B into an analog data signal Vid_B through a similar process and supplies it to the liquid crystal panel 100B. The third threshold will be described later with reference to FIG. 12 or FIG.

[0045] Next, specific examples of the processing circuits 22R, 22G, and 22B that perform such correction will be described.

[0046] FIG. 9 is a block diagram showing the configuration of the processing circuits 22R, 22G, and 22B. As shown in this diagram, the processing circuit 22R includes a low-pass filter 221R and a correction circuit 223R. The low-pass filter 221R smoothes the gradation level specified by the pixel data constituting the R-component video data Va_R of the video data Vid_in, i.e., executes the first process described above. The smoothing of the gradation levels is performed by using a filter coefficient matrix such as that shown in FIG.

[0047] The coefficient matrix of the filter shown in Figure 10 means that when focusing on a single video image in the array of video pixels that make up the video data Va_R, if the gradation level of the focused video pixel is higher than the gradation levels of the surrounding video pixels, the gradation level of the focused video pixel is multiplied by the coefficient shown in the thick frame to lower it, and the gradation levels of the video pixels located around the focused video pixel are increased by an amount corresponding to the multiplication by a coefficient depending on their position.

[0048] Note that the coefficients in the filter coefficient matrix in Figure 10 are merely an example, and this is an example in which the difference "0.9" (=1-0.1) generated by multiplication of the coefficients shown in bold frames is distributed to 48 surrounding image pixels according to the distance from the image pixel of interest.

[0049] In FIG. 9, the correction circuit 223R executes the second to sixth processes and supplies the data signal Vid_R to the liquid crystal panel 100R.

[0050] Next, specific examples of the first to fifth processes will be described.

[0051] FIG. 11 is a diagram showing the relationship between the voltage applied to the liquid crystal element 120 and the gradation level of, for example, six consecutive panel pixels in the X direction, among the panel pixels whose gradation levels are specified by the pixel data constituting the R component video data Va_R. The vertical axis of the graph represents the applied voltage and grayscale level of the liquid crystal element 120. Note that the linearity between the applied voltage and grayscale level of the liquid crystal element 120 is actually different. Furthermore, in the figure, squares represent panel pixels, and the density of the panel pixels represents the transmittance when the applied voltage shown in the figure is applied to the liquid crystal element 120.

[0052] The examples in the left and right columns of FIG. 11 are both examples in which a dark panel pixel whose gradation level is equal to or less than the first threshold value Th1 and a dark panel pixel whose gradation level is equal to or less than the second threshold value Th2 are adjacent to each other. The left column of the figure shows a case where a greater number of bright panel pixels Lp1 to Lp5 than the dark panel pixel Dpa are adjacent to the dark panel pixel Dpa in order along the X direction. Although not shown in the figure, a panel pixel to the left of the dark panel pixel Dpa is located to the left of the dark panel pixel Dpa, to which a gradation level that is not less than the first threshold value and not more than the second threshold value is assigned. Therefore, no boundary is formed between the dark panel pixel Dpa and its left adjacent panel pixel.

[0053] The right column of the figure shows a case where a greater number of dark panel pixels Dp1 to Dp5 than the bright panel pixel Lpa are adjacent to the bright panel pixel Lpa in the X direction. Although not shown in the figure, to the left of the bright panel pixel Lpa is a panel pixel to which a gradation level that is not less than the first threshold value and not more than the second threshold value is assigned. Therefore, no boundary is formed between the bright panel pixel Lpa and its left adjacent panel pixel.

[0054] Fig. 12 is a diagram showing the results of smoothing, by low-pass filter 221R, the gradation levels specified by the pixel data shown in Fig. 11. In detail, the left column of Fig. 12 shows the results of smoothing the gradation levels shown in the left column of Fig. 11, and the right column of Fig. 12 shows the results of smoothing the gradation levels shown in the right column of Fig. 11.

[0055] 12, the gradation level of the dark panel pixel Dpa is processed to be brighter, and the bright panel pixels Lp1 to Lp5 are processed to be darker the closer they are to the dark panel pixel Dpa. Note that this example is an example in which the gradation levels of the bright panel pixels Lp1 to Lp3, which are closest to the dark panel pixel Dpa, among the bright panel pixels Lp1 to Lp5, are processed to be darker. 12, the gradation level of the bright panel pixel Lpa is processed to become darker, and the dark panel pixels Dp1 to Dp5 are processed to become brighter as they become closer to the bright panel pixel Lpa. Note that this example is an example in which the gradation levels of the dark panel pixels Dp1 to Dp3 that are closer to the bright panel pixel Lpa, among the dark panel pixels Dp1 to Dp5, are processed to become brighter.

[0056] 12, gradation level L1 is the gradation level of a bright panel pixel Lp1 adjacent to a dark panel pixel Dpa after smoothing. In detail, gradation level L1 is the gradation level of a bright panel pixel Lp1 after smoothing when the boundary between the dark panel pixel Dpa and the bright panel pixel Lp1 is formed and the number of bright panel pixels following the bright panel pixel Lp1 is greater than the number of dark panel pixels Dpa. Furthermore, the gradation level L2 is the gradation level of the bright panel pixel Lpa adjacent to the dark panel pixel Dp1 after smoothing. More specifically, the gradation level L2 is the gradation level of the bright panel pixel Lpa after smoothing when the boundary between the bright panel pixel Lpa and the dark panel pixel Dp1 is formed and the dark panel pixel Dp1 is followed by a number of dark panel pixels greater than the number of the bright panel pixel Lpa. The gradation level L2 is lower than the gradation level L1 because the dark panel pixel Dp1 is adjacent to the bright panel pixel Lpa, and further the dark panel pixel Dp1 is followed by the dark panel pixels Dp2 and onward, which means that the effect of smoothing is strong.

[0057] The third threshold value Th3 is set to a range equal to or less than the gradation level L1 and higher than the gradation level L2. Note that this range does not include the gradation level L2. This range is indicated by hatching in FIGS. 12 and 13.

[0058] FIG. 13 is a diagram showing examples of the third process, the fourth process, and the fifth process, and the processing target is the smoothed gradation level shown in FIG. In the left column of Fig. 12, the gradation level of the bright panel pixel Lp1 associated with the boundary is determined to be equal to or greater than the third threshold value Th3 by the third process, and therefore the fourth process is executed. In detail, as the fourth process, as shown in the left column of Fig. 13, the gradation level of the dark panel pixel Dpa associated with the boundary is corrected to approach the second threshold value Th2, and the gradation levels of the bright panel pixel Lp1 associated with the boundary and the bright panel pixels Lp2 and Lp3, which have been processed to have darker gradation levels by smoothing, are corrected to approach the first threshold value Th1.

[0059] In contrast, in the right column of Fig. 12, the gradation level of the bright panel pixel Lpa associated with the boundary is determined to be equal to or greater than the third threshold value Th3 by the third process, so the fourth process is not performed and the fifth process is performed. More specifically, in the fifth process, the smoothed gradation level is output as is, as shown in the left column of Fig. 13. That is, the left column of Fig. 13 is the same as the left column of Fig. 12. The target of the fifth process is the bright panel pixel Lpa related to the boundary, and includes pixel data of the bright panel pixel Lpa and dark panel pixels Dp1 to Dp3 whose gradation level is not equal to or greater than the third threshold Th3, as well as pixel data of panel pixels that are not detected as a boundary in the second process.

[0060] According to this embodiment, when bright panel pixels and dark panel pixels are adjacent to each other and there are more bright panel pixels than dark panel pixels, domain correction is performed to reduce the horizontal electric field between the bright panel pixels and the dark panel pixels, but when there are more dark panel pixels than bright panel pixels, domain correction is not performed. Therefore, it is possible to effectively suppress domains while suppressing black floating and display contradiction.

[0061] The first process is an example of a “first correction,” and the fourth process is an example of a “second correction.” The boundary between the dark panel pixel Dpa and the light panel pixel Lp1 is an example of a “first boundary,” and the boundary between the light panel pixel Lpa and the dark panel pixel Dp1 is an example of a “second boundary.”

[0062] The processing contents of the processing circuits 22R, 22G, and 22B in the embodiment can be conceptualized as a display control method. Note that the processing circuits 22R, 22G, and 22B only differ in the color components of the video data to be processed, and the processing contents themselves are the same. For this reason, the processing contents of the processing circuits 22R, 22G, and 22B will be described representatively for the processing circuit 22R.

[0063] FIG. 14 is a flowchart showing the display control method. First, the processing circuit 22R accumulates the R component video data Va_R, for example, for one frame, and smoothes the gradation level of the pixel specified by the pixel data (step S10).

[0064] Next, after smoothing, the processing circuit 22R detects a boundary between a bright panel pixel whose gradation level is equal to or greater than the first threshold and a dark panel pixel whose gradation level is equal to or less than the second threshold in the X direction or the Y direction (step S12). If no boundary is detected (the detection result in step S12 is "No"), the processing circuit 22R skips the processing procedure to step S18.

[0065] If a boundary is detected (the detection result in step S12 is "Yes"), the processing circuit 22R further determines whether the gradation level of the bright panel pixel associated with the detected boundary is equal to or greater than a third threshold value Th3 (step S14). If the gradation level of the bright panel pixel associated with the detected boundary is not equal to or greater than the third threshold value Th3 (the determination result in step S14 is "No"), the processing circuit 22R skips to step S18.

[0066] If the gradation level of the bright panel pixel associated with the detected boundary is equal to or greater than the third threshold value Th3 (if the judgment result of step S14 is "Yes"), the processing circuit 22R performs a correction to bring the gradation level of the bright panel pixel associated with the detected boundary closer to the first threshold value and the gradation level of the dark panel pixel associated with the boundary closer to the second threshold value (step S16).

[0067] On the other hand, if the gradation levels of the panel pixels not related to the boundary and the bright panel pixels related to the boundary are less than the third threshold Th3, the processing circuit 22R outputs the smoothed gradation levels of the panel pixels related to the boundary as they are without performing any correction (step S18). Note that if the processing circuit 22R detects multiple boundaries in one frame of video data Vid_in, it performs the processes of steps S14, S16 and S18 for all of the boundaries.

[0068] The processing circuit 22R converts the gradation level corrected in step S16 or the gradation level output as is in step S18 into an analog data signal Vid_R and supplies it to the liquid crystal panel 100R (step S20).

[0069] The processing circuit 22G also converts the video data Va_G into an analog data signal Vid_G through a similar process and supplies it to the liquid crystal panel 100G. The processing circuit 22B also converts the video data Va_B into an analog data signal Vid_B through a similar process and supplies it to the liquid crystal panel 100B.

[0070] For example, in the processing circuit 22R, the smoothing by the low-pass filter 221R and the correction processing by the correction circuit 223R can be conceptualized as an integrated process without being distinguished from each other. That is, the processing circuit 22R: Detecting a boundary between adjacent bright panel pixels Lp, whose pixel data constituting the video data Va_R has a gradation level equal to or greater than a first threshold value Th1, and dark panel pixels Dp, whose pixel data has a gradation level equal to or less than a second threshold value Th2; At the boundary, a first boundary where a dark panel pixel Dp and a number of consecutive light panel pixels Lp greater than the number of the dark panel pixels Dp are adjacent to each other; a second boundary where a dark panel pixel Dp and a number of consecutive light panel pixels Lp less than the number of the dark panel pixels Dp are adjacent to each other; If detected, a correction amount for the pixel data of the light panel pixel Lp associated with the first boundary is set to be smaller than a correction amount for the pixel data of the light panel pixel Lp associated with the second boundary; The correction amount for the pixel data of the dark panel pixels Dp associated with the first boundary is made larger than the correction amount for the pixel data of the dark panel pixels Dp associated with the second boundary. This is the structure.

[0071] 14 has been exemplified as a display control method for the processing circuits 22R, 22G, and 22B, but the processing from step S10 onwards may be changed as follows: Although the case of the processing circuit 22R will be described as an example, similar processing may also be performed for the processing circuits 22G and 22B. For the pixels smoothed in step S10, a boundary between a bright panel pixel whose gradation level is greater than the third threshold value Th3 and a dark panel pixel whose gradation level is less than the third threshold value Th3, adjacent to each other in the X direction or Y direction, is detected. If the detection result shows that no boundary is detected, processing circuit 22R skips the processing procedure and outputs the smoothed gradation level as is. When a boundary is detected, the processing circuit 22R determines whether the bright pixels of the pixels constituting the boundary are equal to or greater than a first threshold value Th1. If the bright pixels constituting the boundary are equal to or greater than the first threshold value Th1, the processing circuit 22R determines whether the dark pixels constituting the boundary are equal to or less than a second threshold value Th2. If the dark pixels constituting the boundary are equal to or less than the second threshold value Th2, the processing circuit 22R corrects the bright pixels constituting the boundary to approach the first threshold value Th1 and corrects the dark pixels constituting the boundary to approach the second threshold value Th2, and outputs the corrected gradation level. If the dark pixels constituting the boundary are greater than the second threshold value Th2, the processing circuit 22R corrects the bright pixels constituting the boundary to approach the first threshold value Th1, does not correct the dark pixels constituting the boundary, and outputs the corrected gradation level. If the bright pixels that make up the boundary are smaller than the first threshold Th1, it is determined whether the dark pixels that make up the boundary are equal to or smaller than the second threshold Th2. If the dark pixels that make up the boundary are equal to or smaller than the second threshold Th2, the bright pixels that make up the boundary are not corrected, but the dark pixels that make up the boundary are corrected to approach the second threshold Th2, and the processing circuit 22R outputs the corrected gradation level. If the dark pixels that make up the boundary are larger than the second threshold Th2, the processing circuit 22R skips the processing step and outputs the smoothed gradation level as is.

[0072] 11 and 12 illustrate an example in which there is one dark panel pixel Dp associated with the boundary, but two or more may be consecutive in the X or Y direction. However, when there are k or more consecutive dark panel pixels Dp associated with the boundary, the number of boundary light panel pixels Lp to be corrected may be (k+1) or more, where k is an integer of 2 or greater. The liquid crystal panel 100 is not limited to a transmissive type, but may be a reflective type.

[0073] From the above-described exemplary embodiments, the following aspects can be understood, for example.

[0074] A liquid crystal display device according to one aspect 1 includes a liquid crystal panel having panel pixels and a display control circuit that controls the liquid crystal panel, wherein video data is composed of pixel data corresponding to the panel pixels, the pixel data specifying the gradation levels of the panel pixels, and the display control circuit performs a first correction on each pixel data that constitutes the video data based on the gradation levels of the gradation data of panel pixels surrounding each pixel data, and determines whether a bright panel pixel, whose gradation level specified by the first corrected pixel data is equal to or higher than a first threshold, is adjacent to a dark panel pixel, whose gradation level is equal to or lower than a second threshold. and if there is a first boundary among the bright panel pixels associated with the detected boundaries where the gradation level specified by the pixel data of the first corrected bright panel pixel is equal to or higher than a third threshold, a second correction is performed on a first bright panel pixel and a first dark panel pixel adjacent to each other across the first boundary, in which the gradation level specified by the pixel data of the first corrected first bright panel pixel approaches the first threshold and the gradation level specified by the pixel data of the first corrected first dark panel pixel approaches the second threshold, and a data signal corresponding to the corrected gradation level is supplied to the panel pixels.

[0075] The liquid crystal display device according to the first aspect can suppress the so-called floating black level and also suppress the occurrence of domains.

[0076] In a liquid crystal display device according to a specific aspect 2 of aspect 1, the display control circuit reduces the difference in gradation levels specified by the pixel data of adjacent panel pixels for each pixel data constituting the video data as the first correction.

[0077] In a liquid crystal display device according to another specific aspect 3 of aspect 1, in addition to the first boundary, the boundaries include a second boundary, and the first boundary is adjacent to the dark panel pixel and a number of bright panel pixels greater than the number of the dark panel pixels, and the second boundary is adjacent to the dark panel pixel and a number of bright panel pixels less than the number of the dark panel pixels, and the third threshold value is a value between the gradation level specified by the pixel data of the bright panel pixel at the first boundary and the gradation level specified by the pixel data of the bright panel pixel at the second boundary.

[0078] In addition, a liquid crystal display device according to another aspect 4 includes a liquid crystal panel having panel pixels and a display control circuit that controls the liquid crystal panel, wherein video data is composed of pixel data corresponding to the panel pixels, and the pixel data specifies the gradation levels of the panel pixels; the display control circuit detects boundaries between adjacent bright panel pixels whose gradation levels specified by the pixel data that make up the video data are equal to or greater than a first threshold and adjacent dark panel pixels whose gradation levels are equal to or less than a second threshold; the display control circuit detects a first boundary and a second boundary; the first boundary is defined as the boundary between the dark panel pixel and a greater number of bright panel pixels than the dark panel pixels, and the second boundary is defined as the boundary between the dark panel pixel and a smaller number of bright panel pixels than the dark panel pixels; and the display control circuit makes the amount of correction made to the pixel data of the bright panel pixels associated with the first boundary smaller than the amount of correction made to the pixel data of the dark panel pixels associated with the first boundary greater than the amount of correction made to the pixel data of the dark panel pixels associated with the second boundary.

[0079] A control method for a liquid crystal display device according to a fifth aspect is a control method for a liquid crystal display device including a liquid crystal panel having panel pixels and a display control circuit that controls the liquid crystal panel, wherein video data is composed of pixel data corresponding to the panel pixels, and the pixel data specifies the gradation levels of the panel pixels, and the display control circuit performs a first correction on each pixel data that constitutes the video data based on the gradation levels of the gradation data of panel pixels surrounding each pixel data, and classifies the gradation levels specified by the first-corrected pixel data as bright panel pixels whose gradation levels are equal to or higher than a first threshold value and dark panel pixels whose gradation levels are equal to or lower than a second threshold value. and a first boundary where the gradation level specified by the pixel data of the first corrected bright panel pixel is equal to or higher than a third threshold value among the bright panel pixels associated with the detected boundary, a second correction is performed on a first bright panel pixel and a first dark panel pixel adjacent to each other across the first boundary, in which the gradation level specified by the pixel data of the first corrected first bright panel pixel approaches the first threshold value and the gradation level specified by the pixel data of the first corrected first dark panel pixel approaches the second threshold value, and a data signal corresponding to the corrected gradation level is supplied to the panel pixels.

[0080] An electronic device according to a sixth aspect includes the liquid crystal display device according to any one of the first to fourth aspects. [Explanation of symbols]

[0081] 1... projection display device, 100R, 100G, 100B... liquid crystal panel, 110... pixel circuit, 118... pixel electrode, 120... liquid crystal element, 20... display control circuit, 22R, 22G, 22B... processing circuit, 221... low-pass filter, 223... correction circuit

Claims

1. a liquid crystal panel having panel pixels; a display control circuit for controlling the liquid crystal panel; Including, video data is composed of pixel data corresponding to the panel pixels, the pixel data specifying the grayscale levels of the panel pixels; The display control circuit includes: performing a first correction on each pixel data constituting the video data based on the gradation level of the gradation data of panel pixels surrounding each pixel data; detecting a boundary between adjacent bright panel pixels whose gradation levels specified by the first corrected pixel data are equal to or greater than a first threshold and dark panel pixels whose gradation levels are equal to or less than a second threshold; Among the bright panel pixels related to the detected boundary, when there is a first boundary where the gradation level specified by the pixel data of the first corrected bright panel pixel is equal to or greater than a third threshold, In a first bright panel pixel and a first dark panel pixel adjacent to each other across the first boundary, performing a second correction to bring the gradation level designated by the pixel data of the first corrected first bright panel pixel closer to the first threshold value and to bring the gradation level designated by the pixel data of the first corrected first dark panel pixel closer to the second threshold value; A data signal corresponding to the corrected gray level is supplied to the panel pixel. LCD display device.

2. The display control circuit includes: As the first correction, For each pixel data constituting the video data, the difference in gray level designated by the pixel data of adjacent panel pixels is reduced. The liquid crystal display device according to claim 1 .

3. The boundaries include a second boundary in addition to the first boundary, The first boundary is the dark panel pixel is adjacent to a greater number of light panel pixels than the dark panel pixels; The second boundary is When the dark panel pixel is adjacent to a number of light panel pixels that is less than the number of the dark panel pixels, The third threshold value is a gradation level specified by pixel data of a bright panel pixel at the first boundary; a gradation level designated by pixel data of a bright panel pixel at the second boundary; is a value between The liquid crystal display device according to claim 1 .

4. a liquid crystal panel having panel pixels; a display control circuit for controlling the liquid crystal panel; Including, video data is composed of pixel data corresponding to the panel pixels, the pixel data specifying the grayscale levels of the panel pixels; The display control circuit includes: Detecting a boundary between adjacent bright panel pixels, the gradation levels of which are specified by pixel data constituting the video data and which are equal to or greater than a first threshold, and dark panel pixels, the gradation levels of which are equal to or less than a second threshold; a first boundary and a second boundary are detected as the boundary; The first boundary is the dark panel pixel is adjacent to a greater number of light panel pixels than the dark panel pixels; The second boundary is When the dark panel pixel is adjacent to a number of light panel pixels that is less than the number of the dark panel pixels, a correction amount for pixel data of the bright panel pixels related to the first boundary is set to be smaller than a correction amount for pixel data of the bright panel pixels related to the second boundary; a correction amount for pixel data of the dark panel pixels related to the first boundary is set to be larger than a correction amount for pixel data of the dark panel pixels related to the second boundary; LCD display device.

5. a liquid crystal panel having panel pixels; a display control circuit for controlling the liquid crystal panel; Including, The video data is composed of pixel data corresponding to the panel pixels, and the pixel data specifies the gray level of the panel pixels. A method for controlling a liquid crystal display device, comprising: The display control circuit includes: A first correction is performed on each pixel data constituting the video data based on the grayscale level of the grayscale data of the panel pixels surrounding each pixel data. detecting a boundary between adjacent bright panel pixels whose gradation levels specified by the first corrected pixel data are equal to or greater than a first threshold and dark panel pixels whose gradation levels are equal to or less than a second threshold; Among the bright panel pixels related to the detected boundary, when there is a first boundary where the gradation level specified by the pixel data of the first corrected bright panel pixel is equal to or greater than a third threshold, In a first bright panel pixel and a first dark panel pixel adjacent to each other across the first boundary, performing a second correction to bring the gradation level designated by the pixel data of the first corrected first bright panel pixel closer to the first threshold value and to bring the gradation level designated by the pixel data of the first corrected first dark panel pixel closer to the second threshold value; A data signal corresponding to the corrected gray level is supplied to the panel pixel. A method for controlling a liquid crystal display device.

6. 5. An electronic device comprising the liquid crystal display device according to claim 1.

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