Display device

Abstract

To provide a display device capable of optimizing uniformization processing of luminance according to an input image and a surrounding situation.SOLUTION: A display device includes a display panel including a display area in which a plurality of pixels are arranged in a first direction and a second direction intersecting the first direction, a light source configured to emit light in the second direction from a side surface of the display panel extending in the first direction, and a signal processing circuit configured to generate an input gradation value corresponding to the plurality of pixels based on an input image and output, according to brightness of the input image, one of a first gradation value that is the input gradation value and a second gradation value obtained by multiplying the input gradation value by a correction coefficient of 1 or less corresponding to attenuation of light propagating in the display panel.SELECTED DRAWING: Figure 11

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a display device configured so that the background on the other side of the display panel can be seen from one side of the panel. The display device in Patent Document 1 is a so-called transparent display, and includes a display panel having a liquid crystal layer containing polymer dispersed liquid crystal, and a light source disposed opposite the side of the display panel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-160254 Summary of the Invention [Problem to be solved by the invention]

[0004] In the display device of Patent Document 1, elements such as switching elements and electrodes are arranged on the display panel. Light incident from the side of the display panel is partially consumed as it propagates through the display panel, and the amount of light decreases as it propagates through the display panel. This causes a brightness gradient within the display surface. For this reason, it is conceivable to equalize the brightness within the display surface by multiplying the grayscale value of each pixel within the display surface by a coefficient corresponding to the brightness gradient, but this would result in a decrease in brightness across the entire display surface regardless of the input image or surrounding conditions.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a display device that can optimize brightness uniformity processing according to the input image and the surrounding conditions. [Means for solving the problem]

[0006] A display device according to one embodiment of the present disclosure includes a display panel having a display area in which a plurality of pixels are arranged in a first direction and a second direction intersecting the first direction; a light source that irradiates light in the second direction from a side of the display panel extending in the first direction; and a signal processing circuit that generates input gradation values ​​corresponding to the plurality of pixels based on an input image, and outputs either a first gradation value that is the input gradation value or a second gradation value that is the input gradation value multiplied by a correction coefficient of 1 or less that corresponds to the attenuation of light propagating within the display panel, depending on the brightness of the input image. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an example of a block configuration of a display device according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of the configuration of the display panel according to the first embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of the display panel. [Figure 4] FIG. 4 is a timing chart showing an image display period during which an input image is displayed. [Figure 5] FIG. 5 is an explanatory diagram showing the relationship between the voltage applied to the polymer dispersed liquid crystal and the degree of scattering of light. [Figure 6A] FIG. 6A is a conceptual diagram illustrating the relationship between light propagating within a display panel and light emitted to the outside. [Figure 6B] FIG. 6B is a conceptual diagram illustrating the relationship between light propagating within the display panel and light emitted to the outside. [Figure 7A] FIG. 7A is a diagram showing a first image display example on the display device according to the first embodiment. [Figure 7B] FIG. 7B is a diagram showing a first image display example on the display device according to the first embodiment. [Figure 7C] FIG. 7C is a diagram showing a first image display example on the display device according to the first embodiment. [Figure 8A] FIG. 8A is a diagram showing gradation values ​​in the first image display example shown in FIGS. 7A, 7B, and 7C. [Figure 8B] FIG. 8B is a diagram showing an in-plane luminance distribution in the first image display example shown in FIGS. 7A, 7B, and 7C. [Figure 9A] FIG. 9A is a diagram showing a second image display example on the display device according to the first embodiment. [Figure 9B] FIG. 9B is a diagram showing a second image display example on the display device according to the first embodiment. [Figure 9C] FIG. 9C is a diagram showing a second image display example on the display device according to the first embodiment. [Figure 10A] FIG. 10A is a diagram showing gradation values ​​in the second image display example shown in FIGS. 9A, 9B, and 9C. [Figure 10B] FIG. 10B is a diagram showing an in-plane luminance distribution in the second image display example shown in FIGS. 9A, 9B, and 9C. [Figure 11] FIG. 11 is a flowchart showing an example of the tone value generation process according to the first embodiment. [Figure 12A] FIG. 12A is a diagram showing the relationship between the input image level and the correction parameter. [Figure 12B] FIG. 12B is a diagram showing the relationship between the input image level and the correction coefficient. [Figure 13] FIG. 13 is a flowchart showing an example of tone value generation processing according to a modified example of the first embodiment. [Figure 14] FIG. 14 is a schematic diagram showing an example of a block configuration of a display device according to the second embodiment. [Figure 15] FIG. 15 is a flowchart showing an example of a tone value generation process according to the second embodiment. [Figure 16] FIG. 16 is a flowchart showing an example of a gradation value generation process according to a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Modes (embodiments) for carrying out the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially identical. Furthermore, the components described below can be combined as appropriate. Furthermore, the disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the disclosure are naturally included within the scope of the present disclosure. Furthermore, for clarity of explanation, the drawings may schematically depict the width, thickness, shape, etc. of each part compared to the actual embodiment. However, these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this specification and each figure, elements similar to those described above with reference to the previous figures may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0009] (Embodiment 1) Fig. 1 is a schematic diagram showing an example of a block configuration of a display device according to embodiment 1. Fig. 2 is a schematic diagram showing an example of a configuration of a display panel according to embodiment 1. The display device 1 according to embodiment 1 has, as its main block configuration, a signal processing circuit 20, a display panel 40, and a light source 60. The display panel 40 has a signal output circuit 31 and a scanning circuit 32. In the present disclosure, the display panel 40 is an active matrix color liquid crystal display panel driven by a so-called field sequential color (FSC) method.

[0010] The display panel 40 is driven and controlled based on signals from the signal processing circuit 20. In the present disclosure, the display panel 40 is a liquid crystal display panel in which polymer dispersed liquid crystal (PDLC) (hereinafter also simply referred to as "liquid crystal") is sealed between opposing substrates. A light source 60 illuminates the display panel 40 from behind. The display panel 40 displays an image using signals from the signal processing circuit 20 and light from the light source 60.

[0011] 2, the display panel 40 has a display area 41 in which a plurality of pixels Pix are arranged in an X direction (first direction) and a Y direction (second direction). The Y direction (second direction) is a direction that intersects with the X direction (first direction). More specifically, in the example shown in FIG. 1, the Y direction (second direction) is a direction that is perpendicular to the X direction (first direction).

[0012] 3 is a schematic cross-sectional view of a display panel 40. As shown in FIG. 3, the display panel 40 includes an array substrate 110, a counter substrate 120, and a liquid crystal layer 150.

[0013] The array substrate 110 has a first light-transmitting base material 119 made of, for example, glass. The first light-transmitting base material 119 may be made of a resin such as polyethylene terephthalate as long as it is light-transmitting. Pixel electrodes PE are provided on the first light-transmitting base material 119. The pixel electrodes PE are made of a light-transmitting conductive material such as ITO (Indium Tin Oxide).

[0014] The counter substrate 120 has a second light-transmitting base material 129 made of, for example, glass. The second light-transmitting base material 129 may be made of a resin such as polyethylene terephthalate as long as it is light-transmitting. A common electrode CE is provided on the second light-transmitting base material 129. The common electrode CE is made of a light-transmitting conductive material such as ITO.

[0015] The counter substrate 120 faces the array substrate 110 in the Z direction (third direction) perpendicular to the surface of the array substrate 110. The polymer dispersed liquid crystal LC of the liquid crystal layer 150 shown in FIG.

[0016] The array substrate 1110 is provided with a first alignment film AL1. The counter substrate 120 is provided with a second alignment film AL2. When the alignment films are subjected to alignment treatment, for example, the alignment direction of the first alignment film AL1 is aligned to one side of the X direction (first direction), and the alignment direction of the second alignment film AL2 is aligned to the other side of the X direction (first direction). The first alignment film AL1 and the second alignment film AL2 may be, for example, vertical alignment films, or may be alignment films aligned in the X direction (first direction) in which a plurality of light-emitting sections 62 (described later) are arranged. The alignment treatment is performed by a rubbing treatment or a photo-alignment treatment.

[0017] The pixel electrodes PE are provided corresponding to the plurality of pixels Pix. Each pixel electrode PE is connected to one of the source or drain of the switching element of each pixel Pix. The other of the source or drain of the switching element is connected to a signal line DTL. The gate of the switching element is connected to a scanning line SCL.

[0018] The switching element is a switching element using a semiconductor, such as a thin film transistor (TFT). Examples of the thin film transistor include a bottom gate transistor and a top gate transistor. Although a single gate thin film transistor is exemplified as the switching element, a double gate transistor may also be used.

[0019] The signal processing circuit 20 outputs various signals for controlling the operations of the signal output circuit 31, the scanning circuit 32, and the light source control circuit 61 in response to an external input signal.

[0020] In the present disclosure, the signal processing circuit 20 generates pixel gradation values ​​corresponding to the input image IS for each of the plurality of pixels Pix in the display area 41.

[0021] The scanning circuit 32 sequentially supplies drive signals to the pixels Pix arranged in the Y direction (second direction) via the scanning lines SCL arranged in the Y direction (second direction). In the present disclosure, the number of scanning lines SCL is set to N (N is a natural number).

[0022] The signal output circuit 31 outputs pixel gradation values ​​corresponding to a plurality of pixels Pix connected to a scanning line SCL to which a drive signal is supplied from a scanning circuit 32 via signal lines DTL arranged in the X direction (first direction). In the present disclosure, the number of signal lines DTL is set to M (M is a natural number).

[0023] The light source 60 includes a plurality of light-emitting units 62. The light source 60 is connected to a light source control circuit 61. The light source 60 is called a side light source, and emits light from a side surface of the display panel 40 extending in the X direction (first direction). The light emitted from the light source 60 propagates within the display panel 40 in the Y direction (second direction).

[0024] The light-emitting unit 62 includes a first light-emitting body 63R that emits light of a first color (e.g., red), a second light-emitting body 63G that emits light of a second color (e.g., green), and a third light-emitting body 63B that emits light of a third color (e.g., blue). Each light-emitting body is, for example, an LED (Light Emitting Diode), but is not limited to this and may be, for example, a CCFL (Cold Cathode Fluorescent Lamp).

[0025] Each light emitter is connected to a light source control circuit 61. Based on a light source control signal from the signal processing circuit 20, the light source control circuit 61 controls each of the first light emitter 63R, the second light emitter 63G, and the third light emitter 63B to emit light in a time-division manner.

[0026] FIG. 3 is a timing chart showing an image display period during which an input image is displayed.

[0027] In a display device 1 that performs display output using the FSC method, the image display period FP of one frame in which an input image IS is displayed is time-divided into a first sub-frame period RF, a second sub-frame period GF, and a third sub-frame period BF, as shown in Figure 3.

[0028] During the vertical scanning period GateScan (first period) of the first sub-frame period RF, the scanning circuit 32 shifts the output target of the drive signal GATE, and the signal output circuit 31 outputs pixel gradation values ​​corresponding to the first color (e.g., red) of the input image IS to each of the multiple pixels Pix connected to the scanning line SCL to which the drive signal GATE is supplied from the scanning circuit 32.

[0029] In the subsequent light emission period RON (second period), the light source control circuit 61 turns on the first light emitter 63R. The first light of a first color (for example, red) emitted from the first light emitter 63R propagates through the display panel 40, and in the liquid crystal layer corresponding to each pixel Pix, the first light is scattered and emitted to the outside in an amount corresponding to the pixel gradation value of the first color supplied to each pixel Pix.

[0030] During the vertical scanning period GateScan (first period) of the second sub-frame period GF, the scanning circuit 32 transitions the output target of the drive signal GATE, and the signal output circuit 31 outputs pixel gradation values ​​corresponding to the second color (e.g., green) of the input image IS to each of the multiple pixels Pix connected to the scanning line SCL to which the drive signal GATE is supplied from the scanning circuit 32.

[0031] In the subsequent light emission period GON (second period), the light source control circuit 61 turns on the second light emitter 63G. The second light of a second color (e.g., green) emitted from the second light emitter 63G propagates through the display panel 40, and in the liquid crystal layer corresponding to each pixel Pix, the second light is scattered and emitted to the outside in an amount corresponding to the pixel gradation value of the second color supplied to each pixel Pix.

[0032] During the vertical scanning period GateScan (first period) of the third sub-frame period BF, the scanning circuit 32 shifts the output target of the drive signal GATE, and the signal output circuit 31 outputs pixel gradation values ​​corresponding to the third color (e.g., blue) of the input image IS to each of the multiple pixels Pix connected to the scanning line SCL to which the drive signal GATE is supplied from the scanning circuit 32.

[0033] In the subsequent light emission period BON (second period), the light source control circuit 61 turns on the third light emitter 63B. The third light of a third color (for example, blue) emitted from the third light emitter 63B propagates through the display panel 40, and in the liquid crystal layer corresponding to each pixel Pix, the third light is scattered and emitted to the outside in an amount corresponding to the pixel gradation value of the third color supplied to each pixel Pix.

[0034] As a result, one frame of the input image IS is visually recognized by the user.

[0035] In the FSC display device 1 described above, due to the afterimage phenomenon that occurs due to the limitations of the temporal resolution of the human eye, an image that is a composite (mixture) of three colors, namely, a first color (red (R)), a second color (green (G)), and a third color (blue (B)), is perceived. Furthermore, in the FSC display device 1, there is no need to provide a color filter for each pixel Pix, so the light transmittance in the display area 41 can be increased.

[0036] Fig. 5 is an explanatory diagram showing the relationship between the voltage applied to the polymer dispersed liquid crystal and the degree of light scattering. In Fig. 5, the horizontal axis represents the potential difference generated between the pixel electrode PE and the common electrode CE, and the vertical axis represents the degree of light scattering of the polymer dispersed liquid crystal in the pixel Pix.

[0037] 5, the degree of light scattering in the pixel Pix changes depending on the potential difference between the pixel electrode PE and the common electrode CE. In a region where the potential difference between the pixel electrode PE and the common electrode CE is close to 0 and in a region where the potential difference between the pixel electrode PE and the common electrode CE is close to the saturation voltage Vsat, the rate of change in the degree of light scattering in the pixel Pix becomes small.

[0038] In the present disclosure, the potential difference between the pixel electrode PE and the common electrode CE is controlled within a voltage range Vdr in which the degree of light scattering in the pixel Pix changes linearly with changes in the potential difference between the pixel electrode PE and the common electrode CE.

[0039] Specifically, the voltage applied to the pixel electrode PE is controlled so that the voltage range Vdr is such that the potential difference between the pixel electrode PE and the common electrode CE changes linearly when the gradation value applied to the pixel Pix is ​​changed. This allows a voltage that causes the potential difference between the pixel electrode PE and the common electrode CE to change linearly in response to changes in the gradation value to be applied to the pixel electrode PE, and the degree of light scattering in the pixel Pix can be changed linearly in response to changes in the gradation value supplied to the pixel Pix.

[0040] 6A and 6B are conceptual diagrams illustrating the relationship between light propagating within the display panel and light emitted to the outside. In Figures 6A and 6B, the thickness of the white arrows indicates the amount of light emitted from the light source 60 and propagating within the display panel 40, and the thickness of the black arrows indicates the amount of light scattered according to the gradation value of the pixel Pix and emitted to the outside.

[0041] 6A illustrates an example in which the gradation values ​​of pixels Pix aligned in the Y direction (second direction) are the same value (GV). The light emitted from the light source 60 is consumed by light scattering by the polymer dispersed liquid crystal, and the amount of light propagating within the display panel 40 gradually decreases. Accordingly, the amount of light emitted to the outside from each pixel Pix gradually decreases.

[0042] 6B illustrates an example in which the gradation value GV of the same value shown in FIG. 6A is multiplied by a correction coefficient P(n) of 1 or less corresponding to the attenuation of light propagating within the display panel 40, and the corrected gradation value GV(n) is supplied to pixels Pix aligned in the Y direction (second direction). In the present disclosure, the correction coefficient P(n) is expressed by the following equation (1), where N is the total number of pixels Pix aligned in the Y direction (second direction), in other words, the pixels aligned in the propagation direction of light emitted from the light source 60, L is the target luminance at the maximum input gradation, T is the amount of light incident on the display panel 40 from the light source 60, and S is a correction parameter.

[0043] P(n)=L / [T×S (n-1) ]···(1)

[0044] In the present disclosure, the correction parameter S can be set within the range of 0 < S ≤ Sf, where Sf is a value for equalizing the in-plane luminance in the display area 41. By setting the correction parameter S to an intermediate value Sv within this range, the average value of the in-plane luminance in the display area 41 can be changed.

[0045] FIGS. 7A, 7B, and 7C are diagrams showing a first image display example in the display device according to Embodiment 1. FIGS. 7A, 7B, and 7C show image display examples in which the input gradation value of all pixels Pix in the display area 41 is the maximum gradation value (for example, "255").

[0046] FIG. 7A shows an image display example in which the input gradation value is output to the display panel 40. FIG. 7B shows an image display example in which the gradation value corrected by setting the correction parameter Sf is output to the display panel 40. FIG. 7C shows an image display example in which the gradation value corrected by setting a correction parameter Sv smaller than the correction parameter Sf is output to the display panel 40.

[0047] FIG. 8A is a diagram showing the gradation values in the first image display example shown in FIGS. 7A, 7B, and 7C. The broken line shown in FIG. 8A indicates the gradation value in the image display example in which the input gradation value is output to the display panel 40. The solid line shown in FIG. 8A indicates the gradation value in the image display example in which the gradation value corrected by setting the correction parameter Sf is output to the display panel 40. The alternate long and short dash line shown in FIG. 8A indicates the gradation value in the image display example in which the gradation value corrected by setting a correction parameter Sv smaller than the correction parameter Sf is output to the display panel 40.

[0048] 8B is a diagram showing the in-plane luminance distribution in the first image display example shown in FIGS. 7A, 7B, and 7C. The dashed line in FIG. 8B indicates the in-plane luminance distribution in the image display example in which input gradation values ​​are output to the display panel 40. The solid line in FIG. 8B indicates the in-plane luminance distribution in the image display example in which gradation values ​​corrected by setting the correction parameter Sf are output to the display panel 40. The dashed-dotted line in FIG. 8B indicates the in-plane luminance distribution in the image display example in which gradation values ​​corrected by setting a correction parameter Sv smaller than the correction parameter Sf are output to the display panel 40. Note that in FIG. 8B, the target luminance after correction at the maximum input gradation is normalized to 1.

[0049] 9A, 9B, and 9C are diagrams showing a second image display example in the display device according to embodiment 1. 9A, 9B, and 9C show an image display example in which the input gradation value of pixels Pix included in the area of ​​lines n1 to n2 in display area 41 is the maximum gradation value (e.g., "255"), and the input gradation value of pixels Pix included in other areas is "0."

[0050] Fig. 9A shows an example of an image display in which input gradation values ​​are output to the display panel 40. Fig. 9B shows an example of an image display in which gradation values ​​corrected by setting a correction parameter Sf are output to the display panel 40. Fig. 9C shows an example of an image display in which gradation values ​​corrected by setting a correction parameter Sv that is smaller than the correction parameter Sf are output to the display panel 40.

[0051] Fig. 10A is a diagram showing gradation values ​​in the second image display example shown in Fig. 9A, Fig. 9B, and Fig. 9C. The dashed line shown in Fig. 10A indicates gradation values ​​in an image display example in which input gradation values ​​are output to the display panel 40. The solid line shown in Fig. 10A indicates gradation values ​​in an image display example in which gradation values ​​corrected by setting a correction parameter Sf are output to the display panel 40. The dashed-dotted line shown in Fig. 10A indicates gradation values ​​in an image display example in which gradation values ​​corrected by setting a correction parameter Sv that is smaller than the correction parameter Sf are output to the display panel 40.

[0052] 10B is a diagram showing the in-plane luminance distribution in the second image display example shown in FIGS. 9A, 9B, and 9C. The dashed line in FIG. 10B indicates the in-plane luminance distribution in the image display example in which input gradation values ​​are output to the display panel 40. The solid line in FIG. 10B indicates the in-plane luminance distribution in the image display example in which gradation values ​​corrected by setting the correction parameter Sf are output to the display panel 40. The dashed-dotted line in FIG. 10B indicates the in-plane luminance distribution in the image display example in which gradation values ​​corrected by setting a correction parameter Sv smaller than the correction parameter Sf are output to the display panel 40. Note that in FIG. 10B, the target luminance after correction at the maximum input gradation is normalized to 1.

[0053] When the input grayscale value is output to the display panel 40, a brightness gradient occurs due to a decrease in the amount of light propagating within the display panel 40. On the other hand, if the image has locally high brightness and a relatively low average brightness (dark), a high-contrast image display is obtained.

[0054] In contrast, when the correction parameter Sf is set and the corrected gradation value is output to the display panel 40, the in-plane luminance average value decreases within the display area 41. On the other hand, the in-plane luminance distribution is flat, and it is possible to equalize the in-plane luminance of an image with a relatively high average luminance (bright).

[0055] Furthermore, when a correction parameter Sv smaller than the correction parameter Sf is set and a corrected gradation value is output to the display panel 40, the correction coefficient P(n) calculated by the above formula (1) may be 1 or greater. However, in the present disclosure, the correction coefficient P(n) is set to 1 or less. Specifically, FIGS. 8A and 8B illustrate an example in which the correction coefficient P(n) calculated by the above formula (1) is 1 or greater when n≧n0. In this example, the correction coefficient P(n≧n0) by which the input gradation value of pixel Pix included in an area of ​​n0 lines or more is multiplied is set to 1. This makes it possible to increase the average in-plane luminance value within the display area 41, as indicated by the dashed dotted line in FIG. 8B.

[0056] In the present disclosure, the signal processing circuit 20 controls the gradation value to be output to the display panel 40 in accordance with the relative brightness of the input image IS. A specific example of gradation value control in the display device 1 according to the first embodiment will be described below.

[0057] FIG. 11 is a flowchart showing an example of the tone value generation process according to the first embodiment.

[0058] In the gradation value generation process shown in FIG. 11, the signal processing circuit 20 generates input gradation values ​​corresponding to multiple pixels Pix in the display area 41 based on the input image IS (step ST101), and calculates an input image level PLv that defines the brightness of the input image IS using the following equations (2) to (5) (step ST102).

[0059] Specifically, the signal processing circuit 20 calculates the average value GVRave of the input gradation values ​​of the first color (for example, red) included in the input image IS using the following equation (2):<m,n> indicates the input gradation value of the first color corresponding to the pixel Pix in the mth column and the nth row.

[0060]

number

[0061] Furthermore, the signal processing circuit 20 calculates the average value GVGave of the input gradation values ​​of the second color (for example, green) included in the input image IS using the following equation (3):<m,n> indicates the input gradation value of the second color corresponding to the pixel Pix in the mth column and the nth row.

[0062]

number

[0063] Furthermore, the signal processing circuit 20 calculates the average value GVBave of the input gradation values ​​of a third color (for example, blue) included in the input image IS using the following equation (4):<m,n> indicates the input gradation value of the third color corresponding to the pixel Pix in the mth column and the nth row.

[0064]

number

[0065] The following formula (5) shows a function in which the minimum value of the average values ​​GVRave, GVGave, and GVBave is set as the input image level PLv.

[0066] PLv=Min(GVRave,GVGave,GVBave)...(5)

[0067] Next, the signal processing circuit 20 determines whether the calculated input image level PLv is less than a predetermined threshold PLvth (step ST103), and if the input image level PLv is less than the predetermined threshold PLvth (step ST103; Yes), it outputs the input gradation value generated in step ST101 to the display panel 40 as the first gradation value (step ST104), and returns to the processing of step ST101.

[0068] If the input image level PLv is equal to or greater than a predetermined threshold value PLvth (step ST103; No), the signal processing circuit 20 sets a correction parameter S corresponding to the input image level PLv calculated in step ST102 (step ST105), and calculates a correction coefficient P(n) corresponding to the pixel Pix aligned in the propagation direction (Y direction (second direction)) of the light emitted from the light source 60 using the above (1) (step ST106).

[0069] Fig. 12A is a diagram showing the relationship between an input image level and a correction parameter, and Fig. 12B is a diagram showing the relationship between an input image level and a correction coefficient.

[0070] In the example shown in FIG. 12A, the signal processing circuit 20 sets a correction parameter Sf for equalizing the in-plane luminance in the display area 41 in the region where PLv ≧ PLv1, and sets a correction parameter Sv that monotonically decreases as the input image level PLv decreases in the region where PLvth ≦ PLv < PLv1. As a result, as shown in FIG. 12B, the correction coefficient P(n) calculated by the above equation (1) monotonically increases as the input image level PLv decreases in the region where PLvth ≦ PLv < PLv1.

[0071] In addition, in FIG. 12B, as shown by the broken line, in the region where PLvth ≦ PLv ≦ PLv2, the correction coefficient P(n) calculated by the above equation (1) becomes 1 or more. Therefore, an embodiment in which the correction coefficient P(n) is set to 1 in the region where PLvth ≦ PLv ≦ PLv2 is illustrated.

[0072] Returning to FIG. 11, the signal processing circuit 20 executes a tone conversion process of multiplying the input tone value generated in step ST101 by the correction coefficient P(n) calculated in step ST106 (step ST107), outputs the tone value after the tone conversion process to the display panel 40 as a second tone value (step ST108), and returns to the process of step ST101.

[0073] In the tone value generation process in the display device 1 according to the above-described Embodiment 1, for example, when the input image IS is an image with locally high luminance and relatively low (dark) average luminance such as a text display image, it is assumed that the input image level PLv becomes less than the threshold value PLvth in step ST103 (step ST103; Yes). As a result, the input tone value generated in step ST101 is output to the display panel 40 as a first tone value (step ST104), and a high-contrast image display is obtained.

[0074] Also, in the gradation value generation process in the display device 1 according to the above-described Embodiment 1, for example, when the input image IS is an image with a relatively high (bright) average luminance, it is assumed that the input image level PLv becomes equal to or higher than the threshold value PLvth in step ST103 (step ST103; No). Further, for example, when the input image IS is an image with a flat in-plane luminance distribution such as a map display image, it is assumed that the input image level PLv falls in the region of PLv ≧ PLv1 shown in FIG. 12A. Thereby, the gradation value after the gradation conversion processing calculated using the correction parameter Sf for equalizing the in-plane luminance in the display region 41 is output to the display panel 40 as the second gradation value (step ST108), and the in-plane luminance in the display region 41 can be equalized.

[0075] Also, for example, when the input image IS is an image with intermediate luminance and small luminance variation such as a natural image, it is assumed that the input image level PLv falls in the region of PLvth ≦ PLv < PLv1 shown in FIG. 12A. Thereby, the gradation value after the gradation conversion processing calculated using the correction parameter Sv smaller than the correction parameter Sf is output to the display panel 40 as the second gradation value (step ST108), and the average value of the in-plane luminance in the display region 41 can be increased.

[0076] Although an aspect in which the minimum value of the average value of the input gradation values of a plurality of colors included in the input image IS is used as the input image level PLv is illustrated, the present invention is not limited to this. For example, an aspect in which the area ratio of the region where the gradation value is below a predetermined value in the input image IS is adopted as the input image level PLv may be used.

[0077] (Modified Example) FIG. 13 is a flowchart showing an example of the gradation value generation process according to a modified example of Embodiment 1. Here, an aspect of indirectly discriminating the relative brightness according to the attribute of the input image IS and controlling the gradation value output to the display panel 40 will be described. The attribute of the input image IS may be, for example, an aspect added as a label to the input image IS, or an aspect added by image classification processing using machine learning using AI.

[0078] In the gradation value generation process shown in FIG. 13, the signal processing circuit 20 generates input gradation values ​​corresponding to a plurality of pixels Pix in the display area 41 based on the input image IS (step ST201), and acquires the attributes of the input image IS (step ST202).

[0079] Next, the signal processing circuit 20 determines whether the attribute of the input image IS acquired in step ST202 is the first attribute (step ST203). If the attribute of the input image IS is the first attribute (step ST203; Yes), the signal processing circuit 20 outputs the input gradation value generated in step ST201 to the display panel 40 as the first gradation value (step ST204), and returns to the processing of step ST201.

[0080] If the attribute of the input image IS is not the first attribute (step ST203; No), the signal processing circuit 20 then determines whether or not the attribute of the input image IS is the second attribute (step ST205).

[0081] If the attribute of the input image IS is the second attribute (step ST205; Yes), the signal processing circuit 20 sets a correction parameter Sf that equalizes the in-plane luminance in the display area 41 (step ST206), and uses the above (1) to calculate a correction coefficient P(n) corresponding to the pixels Pix aligned in the propagation direction of the light emitted from the light source 60 (Y direction (second direction)) (step ST207).

[0082] The signal processing circuit 20 performs a gradation conversion process in which the input gradation value generated in step ST201 is multiplied by the correction coefficient P(n) calculated in step ST207 (step ST208), and outputs the gradation value after the gradation conversion process to the display panel 40 as the second gradation value (step ST209), and returns to the processing of step ST201.

[0083] If the attribute of the input image IS is not the second attribute (step ST205; No), the signal processing circuit 20 sets a correction parameter Sv that is smaller than the correction parameter Sf (step ST210), and calculates the correction coefficient P(n) corresponding to the pixel Pix aligned in the propagation direction (Y direction (second direction)) of the light emitted from the light source 60 using the above (1) (step ST211).

[0084] The signal processing circuit 20 performs a gradation conversion process in which the input gradation value generated in step ST201 is multiplied by the correction coefficient P(n) calculated in step ST211 (step ST212), and outputs the gradation value after the gradation conversion process to the display panel 40 as the second gradation value (step ST213), and then returns to the processing of step ST201.

[0085] In the gradation value generation process in the display device 1 according to the variation of the first embodiment described above, it is assumed that the first attribute is, for example, that the input image IS is an image with locally high luminance and a relatively low (dark) average luminance, such as a text display image (step ST203; Yes). As a result, the input gradation value generated in step ST201 is output to the display panel 40 as the first gradation value (step ST204), and a high-contrast image display is obtained.

[0086] Furthermore, in the gradation value generation process in the display device 1 according to the modification of the first embodiment described above, it is assumed that the second attribute is, for example, that the input image IS is an image with a flat in-plane luminance distribution, such as a map display image, and that the average luminance of the input image IS is relatively high (bright) (step ST205; Yes). As a result, the gradation value after the gradation conversion process calculated using the correction parameter Sf that equalizes the in-plane luminance in the display region 41 is output to the display panel 40 as the second gradation value (step ST209), and the in-plane luminance in the display region 41 can be equalized.

[0087] Furthermore, in the gradation value generation process in the display device 1 according to the modification of the first embodiment described above, for example, when the input image IS is an image with intermediate luminance and small luminance fluctuations, such as a natural image, it is assumed that the attribute of the input image IS is other than the first attribute and the second attribute (step ST205; No). As a result, a gradation value after gradation conversion process calculated using a correction parameter Sv smaller than the correction parameter Sf is output to the display panel 40 as the second gradation value (step ST213). This makes it possible to increase the in-plane average luminance value within the display area 41.

[0088] (Embodiment 2) 14 is a schematic diagram showing an example of a block configuration of a display device according to embodiment 2. The display device 1a according to embodiment 2 further includes an illuminance sensor 51 that measures ambient illuminance, in addition to the configuration of the display device 1 described in embodiment 1.

[0089] 15 is a flowchart showing an example of tone value generation processing according to embodiment 2. Here, processing described in embodiment 1 may be omitted.

[0090] 15, the signal processing circuit 20a generates input grayscale values ​​corresponding to a plurality of pixels Pix in the display area 41 based on the input image IS (step ST101), and determines whether the illuminance Lx acquired by the illuminance sensor 51 is equal to or greater than a predetermined threshold Lxth (step ST001). If the illuminance Lx acquired by the illuminance sensor 51 is equal to or greater than the threshold Lxth (step ST001; Yes), the signal processing circuit 20a outputs the input grayscale values ​​generated in step ST101 to the display panel 40 as first grayscale values ​​(step ST104), and returns to the processing of step ST101.

[0091] If the illuminance Lx acquired by the illuminance sensor 51 is less than the predetermined threshold value Lxth (step ST001; No), the signal processing circuit 20a executes the processes from step ST102 onwards described in the first embodiment.

[0092] In the gradation value generation process in the display device 1a according to the second embodiment described above, if the illuminance Lx acquired by the illuminance sensor 51 is equal to or greater than a predetermined threshold value Lxth (step ST001; Yes), in other words, in a relatively bright environment, the input gradation value generated in step ST101 is output to the display panel 40 as the first gradation value (step ST104). This allows for a high-contrast image display regardless of the brightness of the input image IS.

[0093] (Variation) 16 is a flowchart showing an example of tone value generation processing according to a modified example of embodiment 2. Here, processing described in the modified example of embodiment 1 may be omitted.

[0094] 16, the signal processing circuit 20a generates input gradation values ​​corresponding to a plurality of pixels Pix in the display area 41 based on the input image IS (step ST201), and determines whether the illuminance Lx acquired by the illuminance sensor 51 is equal to or greater than a predetermined threshold Lxth (step ST001). If the illuminance Lx acquired by the illuminance sensor 51 is equal to or greater than the threshold Lxth (step ST001; Yes), the signal processing circuit 20a outputs the input gradation values ​​generated in step ST201 to the display panel 40 as first gradation values ​​(step ST204), and returns to the processing of step ST201.

[0095] If the illuminance Lx acquired by the illuminance sensor 51 is less than the predetermined threshold value Lxth (step ST001; No), the signal processing circuit 20a executes the processes from step ST202 onwards described in the modification of the first embodiment.

[0096] In the gradation value generation process in the display device 1a according to the modification of the second embodiment described above, if the illuminance Lx acquired by the illuminance sensor 51 is equal to or greater than a predetermined threshold value Lxth (step ST001; Yes), in other words, in a relatively bright environment, the input gradation value generated in step ST201 is output to the display panel 40 as the first gradation value (step ST204). This allows for a high-contrast image display regardless of the attributes of the input image IS.

[0097] Although preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, and various modifications are possible within the scope of the present disclosure. For example, appropriate modifications made within the scope of the present disclosure naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0098] 1,1a Display device 20, 20a Signal processing circuit 31 Signal output circuit 32 Scanning circuit 40 Display Panel 41 Display area 51 Illuminance sensor 60 light source 61 Light source control circuit 62 Light-emitting part 63R First Light-Emitting Body 63G Second Light Source 63B Third Light-Emitting Body 110 Array board 119 First translucent base material 120 Opposing substrate 129 Second translucent base material 150 liquid crystal layer AL1 First alignment layer AL2 Second alignment layer CE common electrode DTL signal line IS Input image LC Polymer dispersed liquid crystal PE pixel electrode Pix SCL scan line

Claims

1. a display panel having a display area in which a plurality of pixels are arranged in a first direction and a second direction intersecting the first direction; a light source that irradiates light in the second direction from a side surface of the display panel that extends in the first direction; a signal processing circuit that generates input gradation values ​​corresponding to the plurality of pixels based on an input image, and outputs, in accordance with the brightness of the input image, either a first gradation value that is the input gradation value or a second gradation value obtained by multiplying the input gradation value by a correction coefficient of 1 or less that corresponds to the attenuation of light propagating within the display panel; Equipped with Display device.

2. The display panel is a liquid crystal panel in which a polymer dispersed liquid crystal is sealed. The display device according to claim 1 .

3. The signal processing circuit setting the correction coefficient according to the brightness of the input image; The display device according to claim 1 .

4. The signal processing circuit monotonically increasing the correction coefficient as the brightness of the input image decreases; The display device according to claim 3 .

5. The signal processing circuit calculating an input image level as the minimum value of the average values ​​of pixel gradation values ​​of each of a plurality of colors included in the input image, and outputting the second gradation value when the input image level is equal to or greater than a predetermined value; The display device according to claim 1 .

6. The signal processing circuit setting the correction coefficient according to the input image level; The display device according to claim 5 .

7. The signal processing circuit monotonically increasing the correction coefficient as the input image level decreases; The display device according to claim 6.

8. The signal processing circuit outputting the first gradation value or the second gradation value according to an attribute of the input image; The display device according to claim 1 .

9. The signal processing circuit setting the correction coefficient according to the attribute of the input image; The display device according to claim 8 .

10. The signal processing circuit When the total number of pixels aligned in the light propagation direction is N, the correction coefficient is P(n) (n is an integer from 1 to N), the target luminance at the maximum input grayscale is L, the amount of light incident on the display panel from the light source is T, and the correction parameter is S, the correction coefficient is calculated using the following formula (1): The display device according to claim 1 . P(n)=L / [T×S （ｎ－１） ]・・・(1)

11. The signal processing circuit setting the correction parameter in accordance with the brightness of the input image; The display device according to claim 10.

12. The signal processing circuit monotonically decreasing the correction parameter as the brightness of the input image decreases; The display device according to claim 11.

13. The signal processing circuit calculating an input image level as the minimum value of the average values ​​of pixel gradation values ​​of each of a plurality of colors included in the input image, and outputting the second gradation value when the input image level is equal to or greater than a predetermined value; The display device according to claim 10.

14. The signal processing circuit setting the correction parameters according to the input image level; The display device according to claim 13.

15. The signal processing circuit monotonically decreasing the correction parameter as the input image level decreases; The display device according to claim 14.

16. The signal processing circuit outputting the first gradation value or the second gradation value according to an attribute of the input image; The display device according to claim 10.

17. The signal processing circuit setting the correction parameters according to the attributes of the input image; The display device according to claim 16.

18. Further provided with an illuminance sensor for measuring ambient illuminance, The signal processing circuit is When the illuminance acquired by the illuminance sensor is equal to or greater than a predetermined value, the first gradation value is output.

18. A display device according to any one of claims 1 to 17.

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