Field sequential liquid crystal display

Abstract

To suppress the occurrence of color cracking. [Solution] A field sequential liquid crystal display device according to one embodiment includes a display panel having a display area in which a plurality of pixels are arranged in a matrix, a light source that irradiates light toward the display panel and includes a first-color light emitter, a second-color light emitter, and a third-color light emitter, and a signal processing circuit that controls the operation for displaying an image corresponding to an image signal in the display area, wherein one frame period for displaying one image in the display area includes a first subframe period for writing the first-color image signal, a second subframe period for writing the second-color image signal, and a third subframe period for writing the third-color image signal, and the signal processing circuit controls the light source in each subframe period to light up the corresponding color light emitter as the primary color light emitter and light up the other color light emitters as secondary color light emitters.

Description

Technical Field

[0001] Embodiments of the present invention relate to a field sequential liquid crystal display device.

Background Art

[0002] As a driving method of a liquid crystal display device, field sequential driving (backlight lighting scan method) is known. In a liquid crystal display device employing field sequential driving, color display is realized by changing the color of illumination for each of a plurality of sub-frame periods included in one frame period.

[0003] However, in a liquid crystal display device employing field sequential driving, color breakup (so-called color bleeding) may occur when the line of sight is moved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, the problem to be solved by the present invention is to provide a field sequential liquid crystal display device capable of suppressing the occurrence of color bleeding.

Means for Solving the Problems

[0006] A field sequential liquid crystal display device according to one embodiment includes a display panel having a display area in which a plurality of pixels are arranged in a matrix, a light source that irradiates light toward the display panel and includes a first-color light emitter, a second-color light emitter, and a third-color light emitter, and a signal processing circuit that controls the operation for displaying an image corresponding to an image signal in the display area. One frame period for displaying one image in the display area includes a first subframe period for writing the first-color image signal, a second subframe period for writing the second-color image signal, and a third subframe period for writing the third-color image signal. The signal processing circuit controls the light source in each subframe period to light up the corresponding color light emitter as the primary color light emitter and to light up the other color light emitters as secondary color light emitters. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the appearance of a head-mounted display equipped with a field sequential liquid crystal display device according to one embodiment. [Figure 2] Figure 2 is a plan view showing a main configuration example of a head-mounted display equipped with a field sequential liquid crystal display device according to the same embodiment. [Figure 3] Figure 3 is a cross-sectional view of AA in Figure 2. [Figure 4] Figure 4 shows an example configuration of a field sequential liquid crystal display device according to the same embodiment. [Figure 5] Figure 5 is a schematic diagram showing an example of the configuration of a display panel in a field sequential liquid crystal display device according to the same embodiment. [Figure 6] Figure 6 is a timing chart showing an example of the display operation during one frame period of a field sequential liquid crystal display device according to a comparative example. [Figure 7] Figure 7 is an xy chromaticity diagram showing the chromaticity of each pixel during one frame period of the field sequential liquid crystal display device according to the same embodiment. [Figure 8]Figure 8 is a timing chart showing an example of the display operation during one frame period of a field sequential liquid crystal display device according to the same embodiment. [Figure 9] Figure 9 is a schematic diagram illustrating the relationship between the image displayed on the field sequential liquid crystal display device according to the first modified example and the concentration area detected by the gaze detection sensor. [Figure 10] Figure 10 is an xy chromaticity diagram showing the chromaticity of each pixel during one frame period of a field sequential liquid crystal display device according to the first modified example. [Figure 11] Figure 11 shows an example of the light source configuration of a field sequential liquid crystal display device according to the second modified example. [Figure 12] Figure 12 shows an example of the light source configuration of a field sequential liquid crystal display device according to the second modified example. [Figure 13] Figure 13 is a schematic diagram showing an image displayed on a field sequential liquid crystal display device according to the second modified example. [Figure 14] Figure 14 is an xy chromaticity diagram showing the chromaticity of each pixel during one frame period of a field sequential liquid crystal display device according to the second modified example. [Modes for carrying out the invention]

[0008] The embodiments will be described below with reference to the drawings. It should be noted that the disclosure is merely an example, and the invention is not limited by the contents described in the embodiments below. Modifications that a person skilled in the art can easily apply are naturally included within the scope of the disclosure. In order to make the explanation clearer, the size, shape, etc. of each part may be schematically represented in the drawings with modifications from the actual embodiments. In some cases, the same reference numerals may be used for corresponding elements in multiple drawings, and detailed explanations may be omitted.

[0009] Figure 1 is a perspective view showing an example of the appearance of a head-mounted display 1 equipped with a field-sequential liquid crystal display device DSP according to one embodiment. The head-mounted display 1 is used to provide, for example, VR (Virtual Reality), AR (Augmented Reality), and MR (Mixed Reality) to the user wearing the head-mounted display 1.

[0010] The head-mounted display 1 includes, for example, a liquid crystal display (LCD) display DSPR for the right eye and an LCD display DSPL for the left eye. When the user wears the head-mounted display 1 on their head, the LCD display DSPR is positioned in front of the user's right eye, and the LCD display DSPL is positioned in front of the user's left eye. The LCD display DSPR is configured substantially the same as the LCD display DSPL. In the following description, the LCD display DSPR and the LCD display DSPL may be collectively referred to as the LCD display DSP.

[0011] The head-mounted display 1 is connected to an information processing device (not shown) via, for example, a cable or wireless communication. The head-mounted display 1 receives image signals from the information processing device to display images on a liquid crystal display device (DSP). The head-mounted display 1 may operate by receiving power from, for example, the information processing device, or it may operate using its own power supply.

[0012] Figure 2 is a plan view showing an example of the main configuration of the head-mounted display 1. In subsequent drawings, mutually orthogonal X, Y, and Z axes are indicated where necessary to facilitate understanding. The direction along the X axis is referred to as the first direction X, the direction along the Y axis as the second direction Y, and the direction along the Z axis as the third direction Z. The first direction X and the second direction Y are parallel to the substrates constituting the liquid crystal display devices DSPR and DSPL, while the third direction Z corresponds to the thickness direction of the liquid crystal display devices DSPR and DSPL. The plane defined by the X and Y axes is referred to as the XY plane.

[0013] The head-mounted display 1 includes, for example, a housing 51, an interface 53, a multi-axis sensor 54, a line-of-sight detection sensor 55, liquid crystal display device DSPs (liquid crystal display device DSPR, liquid crystal display device DSPL), a signal processing circuit 20, and the like. Since the liquid crystal display device DSPs are arranged in front of the user's left and right eyes, they have an optical system (not shown) for forming an image on the user's eyes.

[0014] The housing 51 holds each of the other components included in the head-mounted display 1. For example, the housing 51 holds the liquid crystal display device DSPR and the liquid crystal display device DSPL in a state where they are arranged at a predetermined interval. In the example shown in FIG. 2, a partition 51a is provided between the liquid crystal display device DSPR and the liquid crystal display device DSPL, but the partition 51a may not be provided.

[0015] The liquid crystal display device DSPR and the liquid crystal display device DSPL are liquid crystal display devices provided so as to be independently operable. Each liquid crystal display device DSP includes a display panel, a light source, etc. that operate according to the control of the signal processing circuit 20.

[0016] The interface 53 is a connection part to which various cables can be connected. Specifically, the interface 53 is, for example, an interface that integrates an HDMI (registered trademark) (High Definition Multimedia Interface) interface and a USB (Universal Serial Bus). For example, a cable for communicating with the above-described information processing device is connected to the interface 53. The interface 53 is connected to each liquid crystal display device DSP, the multi-axis sensor 54, and the signal processing circuit 20 via a substrate 57 described later.

[0017] The multi-axis sensor 54 is a sensor for detecting the movement of the head-mounted display 1. The multi-axis sensor 54 can detect the movement of the user when the head-mounted display 1 is worn on the user's head.

[0018] The gaze detection sensor 55 tracks the user's gaze using eye-tracking technology and detects the area where the user's gaze is concentrated. The method for detecting the gaze position by the gaze detection sensor 55 may be any method. This embodiment is not limited by the specific configuration of the gaze detection sensor 55 or the gaze detection method.

[0019] The signal processing circuit 20 controls the operation for displaying images corresponding to image signals from the information processing device on each liquid crystal display device (DSP). More details will be described later.

[0020] Figure 3 is a cross-sectional view of AA in Figure 2 in the XZ plane defined by the first direction X and the third direction Z.

[0021] Each liquid crystal display DSP includes a display panel 40, a light source 60, and the like, as described above.

[0022] The display panel 40 displays an image using signals from the signal processing circuit 20 and light from the light source 60. The display panel 40 has two substrates (a first substrate and a second substrate) and a liquid crystal sealed between the two substrates. The liquid crystal contains liquid crystal molecules whose orientation changes according to the potential of the pixel electrode 11, which will be described later. The display panel 40 controls the transmittance of light incident on the liquid crystal by changing the orientation of the liquid crystal molecules contained in the liquid crystal. The liquid crystal is, for example, a liquid crystal with positive dielectric anisotropy (positive-type liquid crystal), a liquid crystal with negative dielectric anisotropy (negative-type liquid crystal), and a polymer-dispersed liquid crystal.

[0023] The light source 60 emits light from the back toward the display panel 40. The light source 60 comprises a light emitter of a first color (e.g., red), a light emitter of a second color (e.g., green), and a light emitter of a third color (e.g., blue).

[0024] The circuit board 57 of the head-mounted display 1 is equipped with the signal processing circuit 20 and the multi-axis sensor 54 described above. Each liquid crystal display DSP is connected to the signal processing circuit 20 and the multi-axis sensor 54 via the circuit board 57.

[0025] Figure 4 shows an example of the configuration of a liquid crystal display device DSP according to this embodiment. The liquid crystal display device DSP includes a signal processing circuit 20, a display panel 40, a signal output circuit 31, a scanning circuit 32, a light source 60, a light source control circuit 61, and the like.

[0026] The signal processing circuit 20 receives a sequential number of image signals from the information processing device, corresponding to the frame rate. The frame rate indicates the number of frame images displayed in a predetermined time (for example, 1 second). The signal processing circuit 20 also receives a sequential signal from the gaze detection sensor 55 indicating the detection result of the user's gaze position.

[0027] The signal processing circuit 20 outputs various signals to the signal output circuit 31, the scanning circuit 32, and the light source control circuit 61 to control the operation timing according to the input image signal. More detailed functions of the signal processing circuit 20 will be described later.

[0028] The display panel 40 displays an image in response to a signal from the signal processing circuit 20. The display panel 40 has a display area 41 in which multiple pixels PX are arranged in a matrix in a first direction X (row direction) and a second direction Y (column direction). Hereinafter, multiple pixels PX arranged in the first direction X will be referred to as a "pixel row". The example in Figure 4 shows the case where pixel rows PX1 to PXn, each containing multiple pixels PX arranged in the first direction X, are arranged in the second direction Y. Note that n is an integer of 2 or more.

[0029] Details of the signal output circuit 31, scanning circuit 32, and light source control circuit 61 will be described later, along with the explanation in Figure 5.

[0030] Figure 5 is a schematic diagram showing an example configuration of the display panel 40. As described above, the display panel 40 has a plurality of pixels PX arranged in a matrix. Each pixel PX includes a switching element 12 and a pixel electrode 11. The switching element 12 is connected to the scan line GL and the signal line DTL. The switching element 12 is, for example, a thin-film transistor (TFT). The pixel electrode 11 is electrically connected to the signal line DTL via the switching element 12.

[0031] In the example shown in Figure 5, multiple signal lines DTL are aligned along one of the pixel PX alignment directions (first direction X). The signal lines DTL extend along the other of the pixel PX alignment directions (second direction Y). The signal lines DTL are shared by switching elements 12 included in each of the multiple pixels PX aligned along the second direction Y.

[0032] Multiple scan lines GL are aligned along the second direction Y. The scan lines GL extend along the first direction X. The scan lines GL are shared by the switching elements 12 included in each of the multiple pixels PX aligned along the first direction X. In the example shown in Figure 5, the switching elements 12 included in each of the multiple pixels PX in pixel row PX1 are connected to the scan line G1. Similarly, the switching elements 12 included in each of the multiple pixels PX in pixel row PXn are connected to the scan line Gn. The same applies to the switching elements 12 included in each of the multiple pixels PX in other pixel rows and the scan lines GL. The number of scan lines GL in the display area 41 of the display panel 40 is the same as the number of pixel rows in the display area 41.

[0033] The scanning circuit 32 is electrically connected to the display panel 40 by scan lines GL. The scanning circuit 32 turns on (conducts) the switching element 12 connected to each of the multiple scan lines GL by outputting a drive signal to each of the scan lines GL. Specifically, the scanning circuit 32 scans multiple pixel rows PX1 to PXn by shifting the scan lines GL that output the drive signal, for example, from scan line G1 to scan line Gn.

[0034] The signal output circuit 31 is electrically connected to the display panel 40 by the signal line DTL. The signal output circuit 31 outputs an image signal to the signal line DTL. The image signal output to the signal line DTL is supplied to the pixel electrode 11 connected to the switching element 12 during the period when the switching element 12 is ON based on the drive signal output to the scan line GL. When an image signal is supplied to the pixel electrode 11, a voltage corresponding to the image signal is applied to the pixel electrode 11, and the light transmittance of the pixel PX including the pixel electrode 11 (more specifically, the liquid crystal portion overlapping the pixel PX) changes. In the following description, supplying an image signal to the pixel electrode 11 of a certain pixel PX and applying a voltage to the pixel electrode 11 may be referred to as writing an image signal to the pixel PX.

[0035] The light source 60 is located on the back of the display panel 40. The display panel 40 is illuminated by shining light in a direction toward it. The light source 60 has a plurality of light-emitting modules 62. Each of the plurality of light-emitting modules 62 includes a light emitter 63R that emits a first color of light, a light emitter 63G that emits a second color of light, and a light emitter 63B that emits a third color of light. The plurality of light-emitting modules 62 emit the first, second, and third colors of light, respectively, under the control of the light source control circuit 61.

[0036] The light source control circuit 61 controls the operation of light emitters 63R, 63G, and 63B based on the light source control signal from the signal processing circuit 20. The light source control signal is a signal that includes information on the amount of light (luminance) of the light-emitting module 62, which is set according to the input grayscale value to the pixel PX. For example, when a dark image is displayed, the amount of light of the light-emitting module 62 is set low. When a bright image is displayed, the amount of light of the light-emitting module 62 is set high.

[0037] In this embodiment, the light source control circuit 61 sequentially drives each light-emitting element 63R, 63G, and 63B in a field sequential manner. In the field sequential manner, during one frame period, image signals corresponding to the first, second, and third colors are sequentially written in a time-division manner, and the light-emitting elements of the colors corresponding to the written image signals are sequentially lit. Because the human eye has limitations in temporal resolution, afterimages occur when multi-color images are displayed in time division. The field sequential manner utilizes these afterimages to allow humans to recognize an image in which three colors have been combined.

[0038] Next, a comparative example of this embodiment will be described. Figure 6 is a timing chart showing an example of the display operation of a liquid crystal display device DSP according to the comparative example during a one-frame period F. Note that one-frame period F is the period for supplying (writing) the image signal corresponding to one frame image to each pixel PX.

[0039] In the comparative example, one frame period F has subframe periods SR, SG, and SB. In each subframe period SR, SG, and SB, an image signal corresponding to a different color gradation value is written. For example, suppose that the image signal of the first frame for a given pixel PX is represented by RGB gradation values, and (R,G,B)=(r1,g1,b1). r1 is the gradation value of the first color (red) in the input signal containing information indicating the RGB gradation values. g1 is the gradation value of the second color (green) in the input signal containing information indicating the RGB gradation values. b1 is the gradation value of the third color (blue) in the input signal containing information indicating the RGB gradation values.

[0040] In this case, during subframe period SR, an image signal corresponding to the grayscale value "r1" is written to a predetermined pixel PX. Similarly, during subframe period SG, an image signal corresponding to the grayscale value "g1" is written to a predetermined pixel PX. Furthermore, during subframe period SB, an image signal corresponding to the grayscale value "b1" is written to a predetermined pixel PX. This writing of image signals during each subframe period is performed individually for each of the multiple pixel PXs. The RGB grayscale values ​​in the image signal for each pixel PX depend on the content of the displayed image. Note that ST1, ST2, and ST3 in the figure indicate the timing of outputting drive signals to scan lines G1 to Gn (i.e., the timing of driving pixel rows PX1 to PXn). In the following explanation, an image signal corresponding to a grayscale value of a certain color will simply be referred to as the image signal of that color.

[0041] In the example shown in Figure 6, each subframe period SR, SG, and SB includes a scanning period for writing the corresponding color image signal to the pixels and an illumination period for lighting up the light-emitting element corresponding to the color of the written image signal.

[0042] More specifically, the subframe period SR includes a scanning period SPR in which multiple pixel rows included in the display area 41 are scanned to write an image signal corresponding to the gradation value of the first color, and an illumination period LR in which the light-emitting element 63R of the first color included in the light source 60 is lit. More specifically, the scanning period SPR can be described as the period in which drive signals are supplied to multiple pixel rows included in the display area 41 by the scanning circuit 32, and image signals corresponding to the gradation value of the first color are written to those multiple pixel rows by the signal output circuit 31.

[0043] Similarly, the subframe period SG includes a scanning period SPG in which multiple pixel rows in the display area 41 are scanned to write an image signal corresponding to the gradation value of the second color, and an illumination period LG in which the second color light-emitting element 63G in the light source 60 is lit. The subframe period SB also includes a scanning period SPB in which multiple pixel rows in the display area 41 are scanned to write an image signal corresponding to the gradation value of the third color, and an illumination period LB in which the third color light-emitting element 63B in the light source 60 is lit.

[0044] Furthermore, the order in which the image signals are written during a single frame period F is not limited to the order of the first color, second color, and third color; any order is acceptable.

[0045] Thus, in the field sequential method, a single pixel PX can display color by time-division lighting up light-emitting elements of different colors for each subframe period. Specifically, the field sequential method utilizes the afterimage of the human eye, superimposing an image of a different color onto the afterimage of an image of a certain color, thereby allowing humans to perceive a color image. However, for example, if the user moves their gaze after the first color image is displayed, the afterimage of the first color image moves with the user's gaze. As a result, the afterimage of the first color image and the second color image to be displayed next may become misaligned, which can cause a phenomenon where the colors are not mixed correctly (so-called color splitting).

[0046] Therefore, in this embodiment, during each subframe period, control is performed to not only light up the light-emitting element corresponding to the color of the written image signal, but also to light up light-emitting elements of colors that do not correspond to the image being displayed, depending on the content of the displayed image. The display control in this embodiment will be described in detail below.

[0047] First, the signal processing circuit 20 calculates the chromaticity (chromaticity value) of each pixel PX based on the RGB gradation values ​​of the image signal that is to be written to each pixel PX during a frame period F (i.e., the image signal input from the information processing device).

[0048] The signal processing circuit 20 identifies, from among the calculated chromaticities of each pixel PX, the first chromaticity that most closely approximates the chromaticity of the first color (red) light emitter 63R, the second chromaticity that most closely approximates the chromaticity of the second color (green) light emitter 63G, and the third chromaticity that most closely approximates the chromaticity of the third color (blue) light emitter 63B.

[0049] Furthermore, if the signal processing circuit 20 finds that the calculated chromaticity of each pixel PX includes a chromaticity that matches the chromaticity of the first-color light-emitting element 63R, it identifies that chromaticity as the first chromaticity. Similarly, if the signal processing circuit 20 finds that the calculated chromaticity of each pixel PX includes a chromaticity that matches the chromaticity of the second-color light-emitting element 63G, it identifies that chromaticity as the second chromaticity. In addition, if the signal processing circuit 20 finds that the calculated chromaticity of each pixel PX includes a chromaticity that matches the chromaticity of the third-color light-emitting element 63B, it identifies that chromaticity as the third chromaticity.

[0050] In the xy chromaticity diagram of the CIE1931 color space, when the calculated chromaticity of each pixel PX is represented, as shown in Figure 7, a triangle Tr1 is formed with the xy coordinates P1, which is the closest xy coordinate to the xy coordinate PR corresponding to the chromaticity of the first color emitter 63R, corresponding to the first chromaticity; the xy coordinate P2, which is the closest xy coordinate to the xy coordinate PG corresponding to the chromaticity of the second color emitter 63G, corresponding to the second chromaticity; and the xy coordinate P3, which is the closest xy coordinate to the xy coordinate PB corresponding to the chromaticity of the third color emitter 63B, corresponding to the third chromaticity. All the xy coordinates corresponding to the calculated chromaticity of each pixel PX are contained within this triangle Tr1.

[0051] The signal processing circuit 20 controls the first, second, and third chromaticities corresponding to the vertices P1, P2, and P3 of the triangle Tr1 described above to be the illumination chromaticities of the light-emitting module 62 during each subframe period SR, SG, and SB.

[0052] More specifically, during the subframe period SR, the signal processing circuit 20 sets the light intensity of the primary color emitter 63R, the secondary color emitter 63G, and the third color emitter 63B so that the illumination chromaticity of the light-emitting module 62 becomes the primary chromaticity. It then outputs a light source control signal to the light source control circuit 61, which includes information on the light intensity of each emitter 63R, 63G, and 63B.

[0053] Similarly, during the subframe period SG, the signal processing circuit 20 sets the light intensity of the second-color light emitter 63G, which is the primary color, and the light intensity of the third-color light emitter 63B and the first-color light emitter 63R, respectively, so that the illumination chromaticity of the light-emitting module 62 becomes the second chromaticity, and outputs a light source control signal to the light source control circuit 61, which includes information on the light intensity of each light emitter 63R, 63G, and 63B.

[0054] Furthermore, during the subframe period SB, the signal processing circuit 20 sets the light intensity of the third-color light emitter 63B, which is the primary color, and the light intensity of the first-color light emitter 63R and the second-color light emitter 63G, respectively, so that the illumination chromaticity of the light-emitting module 62 becomes the third chromaticity, and outputs a light source control signal to the light source control circuit 61, which includes information on the light intensity of each light emitter 63R, 63G, and 63B.

[0055] Furthermore, the signal processing circuit 20 controls the illumination chromaticity of the light-emitting module 62 as described above, corrects the image signal written to each pixel PX during each subframe period SR, SG, and SB, and outputs the corrected image signal to the signal output circuit 31.

[0056] For example, the signal processing circuit 20 corrects the image signal to be written to each pixel PX during the scanning period SPR included in the subframe period SR, based on the illumination chromaticity (i.e., the first chromaticity described above) of the light-emitting module 62 that is illuminated during the illumination period LR included in the subframe period SR, and outputs the corrected image signal to the signal output circuit 31.

[0057] Similarly, the signal processing circuit 20 corrects the image signal to be written to each pixel PX during the scanning period SPG included in the subframe period SG, based on the illumination chromaticity (i.e., the second chromaticity described above) of the light-emitting module 62 that is illuminated during the illumination period LG included in the subframe period SG, and outputs the corrected image signal to the signal output circuit 31.

[0058] Furthermore, the signal processing circuit 20 corrects the image signal to be written to each pixel PX during the scanning period SPB included in the subframe period SB, based on the illumination chromaticity (i.e., the third chromaticity described above) of the light-emitting module 62 that is illuminated during the illumination period LB included in the subframe period SB, and outputs the corrected image signal to the signal output circuit 31.

[0059] The image signal input from the information processing device to the signal processing circuit 20 is based on the assumption that, for example, focusing on the subframe period SR, the illumination chromaticity of the light-emitting module 62 illuminated during the illumination period LR corresponds to the chromaticity of the first color (that is, the image signal is based on the assumption that only the light-emitting element 63R of the first color is illuminated during the illumination period LR). Therefore, when a voltage corresponding to the image signal is applied to the pixel electrode 11, the transmittance of the liquid crystal becomes unsuitable for the light-emitting module 62 illuminated at the first chromaticity. For this reason, as described above, the signal processing circuit 20 corrects the image signal based on the illumination chromaticity (first chromaticity) of the light-emitting module 62 illuminated during the illumination period LR, and outputs the corrected image signal to the signal output circuit 31, thereby making the transmittance of the liquid crystal suitable for when the light-emitting module 62 is illuminated at the first chromaticity.

[0060] Figure 8 is a timing chart showing an example of the display operation of the liquid crystal display device DSP according to this embodiment during a single frame period F. In Figure 8, ST1, ST2, and ST3 indicate the timing for outputting drive signals to scan lines G1 to Gn (i.e., the timing for driving pixel rows PX1 to PXn), similar to the comparative example described above.

[0061] In this embodiment, each subframe period SR, SG, and SB includes a scanning period for writing the corresponding color image signal to the pixels, and an illumination period in which the light-emitting element corresponding to the color of the written image signal is lit as the primary color light-emitting element, and the light-emitting elements corresponding to the other colors are lit as secondary color light-emitting elements.

[0062] More specifically, the subframe period SR includes the scanning period SPR and the illumination period LR. During the scanning period SPR, multiple pixel rows included in the display area 41 are scanned to write image signals corresponding to the gradation values ​​of the first color. Meanwhile, during the illumination period LR, the first-color light emitter 63R, which is the primary color, is illuminated, and the second-color light emitter 63G and the third-color light emitter 63B, which are secondary colors, are illuminated, so that the illumination chromaticity of the light-emitting module 62 becomes the first chromaticity described above. Since the first chromaticity is an approximation of the first color, as shown in Figure 8, the light intensity LUR1 of the first-color light emitter 63R, which is the primary color, is higher than the light intensity LUG1 of the second-color light emitter 63G and the light intensity LUB1 of the third-color light emitter 63B.

[0063] Similarly, the subframe period SG includes the scanning period SPG and the illumination period LG. During the scanning period SPG, multiple pixel rows included in the display area 41 are scanned to write image signals corresponding to the gradation values ​​of the second color. Meanwhile, during the illumination period LG, the second-color light emitter 63G, which is the primary color, is illuminated, and the third-color light emitter 63B and the first-color light emitter 63R, which are secondary colors, are illuminated, so that the illumination chromaticity of the light-emitting module 62 becomes the second chromaticity described above. Since the second chromaticity is an approximation of the second color, as shown in Figure 8, the light intensity LUG2 of the second-color light emitter 63G, which is the primary color, is higher than the light intensity LUB2 of the third-color light emitter 63B, which is secondary color, and the light intensity LUR2 of the first-color light emitter 63R.

[0064] Furthermore, the subframe period SB includes the scanning period SPB and the illumination period LB. During the scanning period SPB, multiple pixel rows included in the display area 41 are scanned in order to write image signals corresponding to the grayscale values ​​of the third color. Meanwhile, during the illumination period LB, the third-color light emitter 63B, which is the primary color, is illuminated, and the first-color light emitter 63R and the second-color light emitter 63G, which are secondary colors, are illuminated, so that the illumination chromaticity of the light-emitting module 62 becomes the third-color chromaticity described above. Note that since the third-color chromaticity is an approximation of the third color, as shown in Figure 8, the light intensity LUB3 of the third-color light emitter 63B, which is the primary color, is higher than the light intensity LUR3 of the first-color light emitter 63R, which is the secondary color, and the light intensity LUG3 of the second-color light emitter 63G.

[0065] Furthermore, the order in which the image signals are written during a single frame period F is not limited to the order of the first color, second color, and third color; any order is acceptable.

[0066] According to the display operation of this embodiment described above, compared to the comparative example described above, where only the first color light-emitting element 63R is lit during the lighting period LR included in subframe period SR, only the second color light-emitting element 63G is lit during the lighting period LG included in subframe period SG, and only the third color light-emitting element 63B is lit during the lighting period LB included in subframe period SB, the color purity of the light-emitting module 62 that is lit during the lighting periods LR, LG, and LB included in each subframe period SR, SG, and SB can be reduced, and as a result, the occurrence of color cracking can be suppressed.

[0067] (First variation) Next, a first modified example will be described. In the first modified example, the signal processing circuit 20 differs from the embodiment described above in that, when determining the first, second, and third chromaticity, it does not calculate the chromaticity using the image signals written to all pixels PX, but rather uses only the image signals written to pixels PX near the user's gaze position detected by the gaze detection sensor 55 (hereinafter referred to as target pixels PX).

[0068] For example, consider a case where the image I1 shown in Figure 9 is displayed on the display panel 40, and the gaze detection sensor 55 detects a concentration area r1 as the area where the user's gaze is concentrated. In this case, the signal processing circuit 20 calculates the chromaticity of the target pixel PX based on the RGB gradation values ​​of the image signal to be written to the target pixel PX included in the concentration area r1 during a 1-frame period F. The signal processing circuit 20 then identifies the first chromaticity that best approximates the chromaticity of the first color (red) light emitter 63R, the second chromaticity that best approximates the chromaticity of the second color (green) light emitter 63G, and the third chromaticity that best approximates the chromaticity of the third color (blue) light emitter 63B from the calculated chromaticities of the target pixel PX.

[0069] In the xy chromaticity diagram of the CIE1931 color space, when the calculated chromaticity of the target pixel PX is represented, a triangle Tr2 is formed as shown in Figure 10, with the xy coordinate P11 corresponding to the first chromaticity, which is the xy coordinate closest to the xy coordinate PR corresponding to the chromaticity of the first color emitter 63R; the xy coordinate P12 corresponding to the second chromaticity, which is the xy coordinate closest to the xy coordinate PG corresponding to the chromaticity of the second color emitter 63G; and the xy coordinate P13 corresponding to the third chromaticity, which is the xy coordinate closest to the xy coordinate PB corresponding to the chromaticity of the third color emitter 63B. All of the calculated xy coordinates corresponding to the chromaticity of the target pixel PX are contained within this triangle Tr2. Depending on the content of the image displayed in the concentration area r1 where the user's gaze is focused, the triangle Tr2 corresponding to the chromaticity of the target pixel PX is expected to be significantly smaller than the triangle Tr1 (see Figure 7) corresponding to the chromaticity of all pixels PX.

[0070] The signal processing circuit 20 controls the first, second, and third chromaticities corresponding to the vertices P11, P12, and P13 of the triangle Tr2 described above to be the illumination chromaticities of the light-emitting module 62 during each subframe period SR, SG, and SB. Since this control by the signal processing circuit 20 is the same as in the embodiment described above, a detailed explanation is omitted here.

[0071] The signal processing circuit 20 controls the illumination chromaticity of the light-emitting module 62 as described above, corrects the image signal written to each pixel PX during each subframe period SR, SG, and SB, and outputs the corrected image signal to the signal output circuit 31. Since this control of the signal processing circuit 20 is the same as in the embodiment described above, a detailed explanation is omitted here.

[0072] The liquid crystal display DSP according to the first modified example detects the user's gaze and determines the illumination chromaticity of the light-emitting module 62 using only the image signal written to the target pixel PX located near the detected user's gaze position. This makes it possible to further reduce the color purity of the light-emitting module 62 illuminated during illumination periods LR, LG, and LB included in each subframe period SR, SG, and SB, respectively, compared to the embodiment described above, thereby suppressing the occurrence of color cracking.

[0073] (Second variation) Next, a second modified example will be described. In the second modified example, we assume that the light source 60 has the configuration shown in Figures 11 and 12.

[0074] Figure 11 shows a simplified XY plane diagram of the light source 60. The light source 60 has a plurality of light-emitting modules 62 arranged in a matrix. The plurality of light-emitting modules 62 are provided in segments SG, for example, which include m pixels PX (m≧1) arranged along a first direction X and l pixels PX (l≧1) arranged along a second direction Y, and are arranged at equal intervals from each other. The light-emitting modules 62 shown in Figure 10 are, for example, RGB independently lit LEDs. The light source 60 can control the chromaticity of each light-emitting module 62.

[0075] Figure 12 shows a simplified diagram of the XZ plane of the light source 60. The light source 60 has an optical sheet 64 in addition to a plurality of light-emitting modules 62. The optical sheet 64 is placed, for example, between the light-emitting modules 62 and the display panel 40 so that the display panel 40 can be evenly illuminated by the light from the plurality of light-emitting modules 62.

[0076] The signal processing circuit 20 calculates the chromaticity of m × l pixels PX for each segment based on the RGB gradation values ​​of the image signal to be written to each m × l pixel PX in the frame period F. From the chromaticity of the m × l pixels PX, the signal processing circuit 20 identifies the first chromaticity that best approximates the chromaticity of the first color (red) light emitter 63R, the second chromaticity that best approximates the chromaticity of the second color (green) light emitter 63G, and the third chromaticity that best approximates the chromaticity of the third color (blue) light emitter 63B.

[0077] For example, when the image I1 shown in Figure 13 is displayed on the display panel 40, and the chromaticity of the m × l pixels PX included in segment SG1 is calculated as described above, a triangle Tr3 is formed in the CIE1931 color space xy chromaticity diagram, as shown in Figure 14. The triangle Tr3 has as its vertices the xy coordinate P21 corresponding to the first chromaticity, which is the xy coordinate closest to the xy coordinate PR corresponding to the chromaticity of the first light emitter 63R; the xy coordinate P22 corresponding to the second chromaticity, which is the xy coordinate closest to the xy coordinate PG corresponding to the chromaticity of the second light emitter 63G; and the xy coordinate P23 corresponding to the third chromaticity, which is the xy coordinate closest to the xy coordinate PB corresponding to the chromaticity of the third light emitter 63B. All of the xy coordinates corresponding to the chromaticity of the m × l pixels PX included in segment SG1 are contained within this triangle Tr3. Since the m × l pixels PX contained in segment SG1 are pixels that represent the "sun" in image I1 shown in Figure 13, triangle Tr3 is formed at a position close to the xy coordinate PR corresponding to the chromaticity of the first color (red) emitter 63R.

[0078] Furthermore, when the image I1 shown in Figure 13 is displayed on the display panel 40, and the chromaticity of the m × l pixels PX included in segment SG2 is calculated as described above, a triangle Tr4 is formed in the xy chromaticity diagram of the CIE1931 color space, as shown in Figure 14. The triangle Tr4 has as its vertices the xy coordinate P31 corresponding to the first chromaticity, which is the xy coordinate closest to the xy coordinate PR corresponding to the chromaticity of the first color emitter 63R; the xy coordinate P32 corresponding to the second chromaticity, which is the xy coordinate closest to the xy coordinate PG corresponding to the chromaticity of the second color emitter 63G; and the xy coordinate P33 corresponding to the third chromaticity, which is the xy coordinate closest to the xy coordinate PB corresponding to the chromaticity of the third color emitter 63B. All of the xy coordinates corresponding to the chromaticity of the m × l pixels PX included in segment SG2 are contained within this triangle Tr4. Since the m × l pixels PX contained in segment SG2 are pixels that represent the "tree leaves" in image I1 shown in Figure 13, triangle Tr4 is formed at a position close to the xy coordinate PG corresponding to the chromaticity of the second color (green) emitter 63G.

[0079] Furthermore, when the image I1 shown in Figure 13 is displayed on the display panel 40, and the chromaticity of the m × l pixels PX included in segment SG3 is calculated as described above, a triangle Tr5 is formed in the xy chromaticity diagram of the CIE1931 color space, as shown in Figure 14. The triangle Tr5 has as its vertices the xy coordinate P41 corresponding to the first chromaticity, which is the xy coordinate closest to the xy coordinate PR corresponding to the chromaticity of the first light emitter 63R; the xy coordinate P42 corresponding to the second chromaticity, which is the xy coordinate closest to the xy coordinate PG corresponding to the chromaticity of the second light emitter 63G; and the xy coordinate P43 corresponding to the third chromaticity, which is the xy coordinate closest to the xy coordinate PB corresponding to the chromaticity of the third light emitter 63B. All of the xy coordinates corresponding to the chromaticity of the m × l pixels PX included in segment SG3 are contained within this triangle Tr5. Since the m × l pixels contained in segment SG3 are the pixels that represent the "sky" in image I1 shown in Figure 13, triangle Tr5 is formed at a position close to the xy coordinate PB corresponding to the chromaticity of the third color (blue) emitter 63B.

[0080] The signal processing circuit 20 controls the first, second, and third chromaticities corresponding to the vertices P21, P22, and P23 of the triangle Tr3 described above to be the illuminated chromaticities of the light-emitting module 62 corresponding to segment SG1 in each subframe period SR, SG, and SB. Similarly, the signal processing circuit 20 controls the first, second, and third chromaticities corresponding to the vertices P31, P32, and P33 of the triangle Tr4 described above to be the illuminated chromaticities of the light-emitting module 62 corresponding to segment SG2 in each subframe period SR, SG, and SB. Furthermore, the signal processing circuit 20 controls the first, second, and third chromaticities corresponding to the vertices P41, P42, and P43 of the triangle Tr5 described above to be the illuminated chromaticities of the light-emitting module 62 corresponding to segment SG3 in each subframe period SR, SG, and SB. Since these controls by the signal processing circuit 20 are the same as in the embodiments described above, a detailed explanation is omitted here.

[0081] The signal processing circuit 20 controls the illumination chromaticity of the light-emitting module 62 corresponding to segment SG1 as described above, and in each subframe period SR, SG, and SB, corrects the image signals written to the m × l pixels PX included in segment SG1, and outputs the corrected image signals to the signal output circuit 31. Similarly, the signal processing circuit 20 controls the illumination chromaticity of the light-emitting module 62 corresponding to segment SG2 as described above, and in each subframe period SR, SG, and SB, corrects the image signals written to the m × l pixels PX included in segment SG2, and outputs the corrected image signals to the signal output circuit 31. Furthermore, the signal processing circuit 20 controls the illumination chromaticity of the light-emitting module 62 corresponding to segment SG3 as described above, and in each subframe period SR, SG, and SB, corrects the image signals written to the m × l pixels PX included in segment SG3, and outputs the corrected image signals to the signal output circuit 31. Since these controls of the signal processing circuit 20 are the same as in the embodiment described above, a detailed explanation is omitted here.

[0082] The liquid crystal display DSP according to the second modified example uses image signals written to m × l pixels PX included in each segment to determine the illumination chromaticity of the light-emitting module 62 corresponding to each segment. This allows for appropriate control of the color purity of the light-emitting module 62 illuminated during illumination periods LR, LG, and LB included in each subframe period SR, SG, and SB, on a segment-by-segment basis, thereby suppressing the occurrence of color cracking.

[0083] Furthermore, the control of the signal processing circuit 20 shown in the above-described embodiment, the first modified example, and the second modified example may be performed only when information indicating that color cracking is likely to occur is received from the information processing device. When information indicating that color cracking is likely to occur is not received from the information processing device, control may be performed using a normal field sequential method, similar to the comparative example, in which only the light-emitting element of the corresponding color (main color) is lit during each subframe period.

[0084] Although the field sequential liquid crystal display DSPs described above in the embodiments, first modification, and second modification were described as liquid crystal display devices used in the head-mounted display 1, they may also be used for other purposes.

[0085] According to the embodiment described above, a field sequential liquid crystal display device capable of suppressing the occurrence of color cracking can be provided.

[0086] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0087] 1...Head-mounted display, 11...Pixel electrode, 12...Switching element, 20...Signal processing circuit, 31...Signal output circuit, 32...Scanning circuit, 40...Display panel, 41...Display area, 53...Interface, 54...Multi-axis sensor, 55...Eye-gaze detection sensor, 57...Substrate, 60...Light source, 61...Light source control circuit, 62...Light-emitting module, 63R, 63G, 63B...Light-emitting element, DSP, DSPR, DSPL...Liquid crystal display device, PX...Pixel, DTL...Signal line, GL...Scan line.

Claims

1. A display panel having a display area in which multiple pixels are arranged in a matrix, A light source is used to illuminate the display panel, and includes a first-color light emitter, a second-color light emitter, and a third-color light emitter. A signal processing circuit that controls the operation for displaying an image corresponding to an image signal in the aforementioned display area, Equipped with, The frame period for displaying one image in the display area includes a first subframe period for writing the first color image signal, a second subframe period for writing the second color image signal, and a third subframe period for writing the third color image signal. The aforementioned signal processing circuit is During each of the aforementioned subframe periods, the light source is controlled to illuminate the light-emitting element of the corresponding color as the primary color light-emitting element, and to illuminate the light-emitting elements of other colors as secondary color light-emitting elements. Field sequential liquid crystal display device.

2. The aforementioned signal processing circuit is Based on the image signal written to each pixel during the aforementioned one-frame period, the chromaticity of each pixel is calculated. From the chromaticity of each pixel calculated above, a first chromaticity that approximates the illumination chromaticity of the first color light-emitting element, a second chromaticity that approximates the illumination chromaticity of the second color light-emitting element, and a third chromaticity that approximates the illumination chromaticity of the third color light-emitting element are identified, respectively. During the first subframe period, the light source is controlled such that the chromaticity of the light source during that period becomes the first chromaticity, by illuminating the first color light source as the primary color light source and illuminating the second color light source and the third color light source as secondary color light sources. During the second subframe period, the light source is controlled such that the illumination chromaticity of the light source during that period becomes the second chromaticity, by illuminating the second color light-emitting element as the primary color light-emitting element, and illuminating the third color light-emitting element and the first color light-emitting element as secondary color light-emitting elements. During the third subframe period, the light source is controlled such that the illumination chromaticity of the light source during that period becomes the third chromaticity, by illuminating the third color light-emitting element as the primary color light-emitting element and illuminating the first color light-emitting element and the second color light-emitting element as secondary color light-emitting elements. The field sequential liquid crystal display device according to claim 1.

3. The aforementioned signal processing circuit is Based on the illumination chromaticity of the light source during the first subframe period, the image signal of the first color to be written during the first subframe period is corrected. Based on the illumination chromaticity of the light source during the second subframe period, the second color image signal to be written during the second subframe period is corrected. Based on the illumination chromaticity of the light source during the third subframe period, the image signal of the third color to be written during the third subframe period is corrected. The field sequential liquid crystal display device according to claim 2.

4. The system further includes a detection sensor that detects a concentration area on the display area where the user's gaze is focused, The aforementioned signal processing circuit is During the aforementioned one-frame period, the chromaticity of each target pixel is calculated based on the image signal written to the multiple target pixels included in the concentrated region. From the chromaticity of each target pixel calculated above, a first chromaticity that approximates the illumination chromaticity of the first color light-emitting element, a second chromaticity that approximates the illumination chromaticity of the second color light-emitting element, and a third chromaticity that approximates the illumination chromaticity of the third color light-emitting element are identified, respectively. During the first subframe period, the light source is controlled such that the chromaticity of the light source during that period becomes the first chromaticity, by illuminating the first color light source as the primary color light source and illuminating the second color light source and the third color light source as secondary color light sources. During the second subframe period, the light source is controlled such that the illumination chromaticity of the light source during that period becomes the second chromaticity, by illuminating the second color light-emitting element as the primary color light-emitting element, and illuminating the third color light-emitting element and the first color light-emitting element as secondary color light-emitting elements. During the third subframe period, the light source is controlled such that the illumination chromaticity of the light source during that period becomes the third chromaticity, by illuminating the third color light-emitting element as the primary color light-emitting element and illuminating the first color light-emitting element and the second color light-emitting element as secondary color light-emitting elements. The field sequential liquid crystal display device according to claim 1.

5. The aforementioned signal processing circuit is Based on the illumination chromaticity of the light source during the first subframe period, the image signal of the first color to be written during the first subframe period is corrected. Based on the illumination chromaticity of the light source during the second subframe period, the second color image signal to be written during the second subframe period is corrected. Based on the illumination chromaticity of the light source during the third subframe period, the image signal of the third color to be written during the third subframe period is corrected. The field sequential liquid crystal display device according to claim 4.

6. The light source includes a plurality of light-emitting modules arranged at equal intervals in segments containing multiple pixels, Each of the light-emitting modules includes a light-emitting element of the first color, a light-emitting element of the second color, and a light-emitting element of the third color. The signal processing circuit, for each segment, During the aforementioned one-frame period, the chromaticity of the multiple pixels included in the segment is calculated based on the image signals written to the multiple pixels included in the segment. From the chromaticity of the multiple pixels calculated above, a first chromaticity that approximates the illumination chromaticity of the first color light-emitting element, a second chromaticity that approximates the illumination chromaticity of the second color light-emitting element, and a third chromaticity that approximates the illumination chromaticity of the third color light-emitting element are identified, respectively. During the first subframe period, the light-emitting module corresponding to the segment is controlled such that the illumination chromaticity of the light-emitting module corresponding to the segment during that subframe period becomes the first chromaticity, by illuminating the light-emitting element of the first color as the primary color light-emitting element and illuminating the light-emitting elements of the second color and the third color as secondary color light-emitting elements. During the second subframe period, the light-emitting module corresponding to the segment is controlled such that the illumination chromaticity of the light-emitting module corresponding to the segment during that period becomes the second chromaticity, by illuminating the second color light-emitting element as the primary color light-emitting element and illuminating the third color light-emitting element and the first color light-emitting element as secondary color light-emitting elements. During the third subframe period, the light-emitting module corresponding to the segment is controlled such that the illumination chromaticity of the light-emitting module corresponding to the segment during that period becomes the third chromaticity, by illuminating the third color light-emitting element as the primary color light-emitting element and illuminating the first color light-emitting element and the second color light-emitting element as secondary color light-emitting elements. The field sequential liquid crystal display device according to claim 1.

7. The signal processing circuit, for each segment, Based on the illumination chromaticity of the light-emitting module corresponding to the segment during the first subframe period, the image signal of the first color to be written to the plurality of pixels included in the segment during the first subframe period is corrected. Based on the illumination chromaticity of the light-emitting module corresponding to the segment during the second subframe period, the second color image signal to be written to the plurality of pixels included in the segment during the second subframe period is corrected. Based on the illumination chromaticity of the light-emitting module corresponding to the segment during the third subframe period, the image signals of the third color to be written to a plurality of pixels included in the segment during the third subframe period are corrected. The field sequential liquid crystal display device according to claim 6.

8. The aforementioned signal processing circuit is When information is received that the image displayed during the aforementioned one-frame period is prone to color distortion, the light source is controlled during each sub-frame period to illuminate the corresponding colored light source as the primary colored light source and to illuminate the light sources of other colors as secondary colored light sources. A field sequential liquid crystal display device according to any one of claims 1 to 7.

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