Indication device

Abstract

Improve the quality of the display. [Solution] The display device 10 comprises a display panel 11 having a display surface 11DS, an image display unit 13 that displays an image on the display surface 11DS based on grayscale information contained in image data supplied from an external source, an illumination device 12 having a plurality of light sources 15 that irradiate the display panel 11 with light for display, a light source drive unit 19 that drives the plurality of light sources 15 based on brightness information contained in the image data, an illuminance sensor 50 that detects ambient light and outputs a detection signal corresponding to the detected amount of ambient light, and a control unit 30. The control unit 30 corrects the brightness information based on the detection signal and controls the light source drive unit 19 to drive the plurality of light sources 15 based on the corrected brightness information, and also corrects the grayscale information based on the detection signal and controls the image display unit 13 to display an image based on the corrected grayscale information.

Description

Technical Field

[0004] , , , , , ,

[0003] , , ,

[0001] The technology disclosed in this specification relates to a display device with improved display quality.

Background Art

[0002] Conventionally, as an example of a display device, the one described in Patent Document 1 below is known. Patent Document 1 describes an image processing device (image processing IC) that processes a signal for displaying an image on a display device. The image processing IC described in Patent Document 1 includes a luminance correction unit that performs luminance correction on an input image to generate an output image, a luminance average value calculation unit that calculates the luminance average value of the output image, a luminance average value calculation unit that calculates the luminance average value of the input image, a selector, a difference calculation unit that calculates the difference between the luminance average values, a duty value calculation unit that determines a duty value based on the luminance average value or the difference value, a register that stores a table used for determining the duty value, a duty value calculation unit that calculates the duty value of an input PWM signal, and a cooperative processing unit that inputs a plurality of control signals indicating the duty value and determines the duty value of the output PWM signal based on the duty values indicated by both control signals.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The image processing apparatus described in Patent Document 1 above generates output image data by applying a predetermined brightness conversion process to input image data and displays video according to the output image data. However, this brightness conversion process does not reflect the detection signal detected by the illuminance sensor. Therefore, if video is displayed using the backlight that reflects the detection signal detected by the illuminance sensor, there is a risk that the displayed video will have a different color tone than intended, resulting in poor display quality.

[0005] The technologies described herein were developed based on the circumstances described above and aim to improve the quality of labeling. [Means for solving the problem]

[0006] (1) A display device relating to the technology described herein includes a display panel having a display surface, an image display unit that displays an image on the display surface based on grayscale information contained in image data supplied from an external source, an illumination device having a plurality of light sources that irradiates the display panel with light for display, a light source drive unit that drives the plurality of light sources based on brightness information contained in the image data, an illuminance sensor that detects ambient light and outputs a detection signal corresponding to the detected amount of ambient light, and a control unit, wherein the control unit corrects the brightness information based on the detection signal and controls the light source drive unit to drive the plurality of light sources based on the corrected brightness information, and corrects the grayscale information based on the detection signal and controls the image display unit to display the image based on the corrected grayscale information.

[0007] (2) In addition to (1) above, the control unit may control the image display unit to display the image in the first region included in the display surface based on the corrected gradation information, and in the second region other than the first region based on the uncorrected gradation information, and the light source drive unit may drive the first light source that overlaps with the first region among the plurality of light sources based on the corrected brightness information, and drive the second light sources other than the first light source based on the uncorrected brightness information.

[0008] (3) In addition to (1) or (2) above, the control unit of the display device may also include: a correction unit for correcting the brightness information and the grayscale information; a drive signal generation unit for generating a drive signal for driving the light source based on the brightness information corrected by the correction unit and outputting the drive signal to the light source drive unit; and an image signal generation unit for generating an image signal for displaying the image on the display surface based on the grayscale information corrected by the correction unit and outputting the image signal to the image display unit.

[0009] (4) In addition to any of (1) to (3) above, the control unit has a memory that stores a first data table containing multiple correction coefficients and detection signals related to the brightness information, and a second data table containing multiple image data, gradation information, and brightness information, wherein in the first data table the correction coefficients are associated with the detection signals, and in the second data table the gradation information and brightness information are associated with the image data, and the image data includes hue H, saturation S and brightness L in the HSL color space, and the brightness information is The control unit may, by referring to the first data table, extract the correction coefficient associated with the detection signal output from the illuminance sensor, and correct the luminance information by multiplying the extracted correction coefficient with the luminance information. It may also, by referring to the second data table, extract the image data containing the hue H and saturation S included in the image data supplied from an external source, and the luminance L that matches the corrected luminance information, as the corrected image data, and extract the gradation information associated with the corrected image data as the corrected gradation information. [Effects of the Invention]

[0010] The technology described herein can improve the quality of the display. [Brief explanation of the drawing]

[0011] [Figure 1] Schematic side view of a liquid crystal display device according to Embodiment 1 [Figure 2] Cross-sectional view showing the liquid crystal panel and backlight device constituting the liquid crystal display device according to Embodiment 1 [Figure 3] Plan view of the LED substrate included in the backlight device according to Embodiment 1 [Figure 4] Plan view showing the pixel arrangement of the liquid crystal panel according to Embodiment 1 [Figure 5]Plan view showing the relationship between the dimming area and the LEDs in the display area of ​​the liquid crystal panel according to Embodiment 1. [Figure 6] Plan view showing a unit pixel included in the dimming region according to Embodiment 1 [Figure 7] Block diagram showing the electrical configuration of the liquid crystal display device according to Embodiment 1 [Figure 8] Plan view showing the relationship between the first and second regions included in the display area according to Embodiment 1 and the first and second LEDs. [Figure 9] Figure showing the first data table according to Embodiment 1 [Figure 10] Figure showing the second data table according to Embodiment 1 [Figure 11] Flowchart showing the correction process by the control unit according to Embodiment 1 [Modes for carrying out the invention]

[0012] <Embodiment 1> Embodiment 1 will be explained with reference to Figures 1 to 11. In this embodiment, a liquid crystal display device (display device) 10 is used as an example. Note that parts of each drawing show the X, Y, and Z axes, and each axis is drawn so that it corresponds to the direction shown in each drawing. Also, the upper side shown in Figures 1 and 2 is the front side, and the lower side is the back side.

[0013] As shown in Figure 1, the liquid crystal display device 10 comprises a liquid crystal panel (display panel) 11 for displaying images, and a backlight device (illumination device) 12 positioned on the back side (rear side) of the liquid crystal panel 11 for illuminating the liquid crystal panel 11 with light for display. The liquid crystal panel 11 and the backlight device 12 are held together by a predetermined holding member in a stacked state, front and back.

[0014] As shown in Figure 2, the liquid crystal panel 11 is positioned on the front side (light-emitting side) relative to the backlight device 12. The liquid crystal panel 11 has a pair of substrates 11A and 11B that are bonded together, and a liquid crystal layer (not shown) sealed between the pair of substrates 11A and 11B. Of the pair of substrates 11A and 11B, the front side is the opposing substrate 11A, and the back side is the array substrate 11B. Alignment films are provided on the inner surfaces of the opposing substrate 11A and the array substrate 11B. In addition, a pair of polarizing plates 11C are attached to the outer surfaces of the opposing substrate 11A and the array substrate 11B, respectively.

[0015] As shown in FIG. 2, in the liquid crystal panel 11, the central side portion of the display surface 11DS is a display area AA where an image is displayed. In the liquid crystal panel 11, the outer peripheral side portion surrounding the display area AA of the display surface 11DS is a non-display area NAA where an image is not displayed. The array substrate 11B is larger than the counter substrate 11A, and a protruding portion 11B1 is formed such that a part of the array substrate 11B protrudes laterally with respect to the counter substrate 11A. The protruding portion 11B1 is exposed without being covered by the counter substrate 11A. The entire area of the protruding portion 11B1 is the non-display area NAA, and a driver (image display unit) 13 for supplying various signals and a flexible substrate 14 are mounted thereon. The driver 13 is composed of an LSI chip having a drive circuit inside, and processes various signals transmitted by the flexible substrate 14. The driver 13 supplies the processed signals (including image signals) to the liquid crystal panel 11. The driver 13 is mounted on the protruding portion 11B1 of the array substrate 11B by COG (Chip On Glass). The flexible substrate 14 is configured such that a plurality of wiring patterns are formed on a base material made of a synthetic resin material (e.g., polyimide-based resin, etc.) having insulation and flexibility. One end side of the flexible substrate 14 is connected to the protruding portion 11B1 of the array substrate 11B, and the other end side is connected to a control substrate 18 described later. Various signals supplied from the control substrate 18 are transmitted to the liquid crystal panel 11 through the flexible substrate 14, and are output to the display area AA after being processed by the driver 13 in the non-display area NAA. Note that the control substrate 18 is arranged so as to overlap the backlight device 12 on the back side (opposite side to the liquid crystal panel 11).

[0016] As shown in FIG. 2, the backlight device 12 is of a so-called direct - type, and the main surface (light - emitting main surface) that emits light faces the main surface on the back side of the liquid crystal panel 11. Among the light - emitting main surfaces of the backlight device 12, the central - side portion that overlaps with the display area AA of the liquid crystal panel 11 when viewed in a plane is defined as the light - emitting area that emits light. Among the light - emitting main surfaces of the backlight device 12, the outer - peripheral - side portion that overlaps with the non - display area NAA of the liquid crystal panel 11 when viewed in a plane is defined as a non - light - emitting area that hardly emits light. The backlight device 12 includes at least an LED (Light Emitting Diode) 15 as a light source, an LED substrate (light - source substrate) 16 provided with a plurality of LEDs 15, and an optical member 17 that imparts an optical effect to the light emitted from the LED 15.

[0017] As shown in FIG. 2, the LED 15 is surface - mounted on the LED substrate 16. The LED 15 is of a so - called top - surface - emitting type in which the light - emitting surface 15A that emits light faces the side opposite to the LED substrate 16 side (front side, optical member 17 side). The optical axis of the LED 15 coincides with the Z - axis direction. Here, the "optical axis" refers to the axis that coincides with the traveling direction of the light with the highest emission intensity (peak) among the emitted lights of the LED 15. In the present embodiment, as the LED 15, a white LED that emits white light presenting white as a whole is used.

[0018] As shown in FIGS. 2 and 3, the LED substrate 16 has a plate - like or film - like shape with a main surface parallel to the main surface of the liquid crystal panel 11. On the main surface facing the front side of the pair of main surfaces of the LED substrate 16, a plurality of LEDs 15 are surface - mounted, and this is the mounting surface. The LEDs 15 are arranged in plural at positions spaced apart in the X - axis direction and the Y - axis direction within the main surface on the front side of the LED substrate 16. The arrangement of the plurality of LEDs 15 may be a matrix arrangement or a staggered arrangement. The LED substrate 16 is connected to the control substrate 18 via a connection member such as an FPC (Flexible Printed Circuit). A drive signal for driving the LED 15 is supplied to the LED substrate 16 from the control substrate 18 via the connection member.

[0019] As shown in Figure 2, the optical component 17 is in the form of a plate or sheet having main surfaces parallel to the main surfaces of the liquid crystal panel 11 and the LED substrate 16. The optical component 17 is positioned on the front side of the LED 15 with a gap in the Z-axis direction. The optical component 17 has the function of imparting a predetermined optical effect to the light emitted from the LED 15 and directing it toward the liquid crystal panel 11. In Figure 2, three optical components 17 are stacked on top of each other. The three optical components 17 include a diffuser plate, a prism sheet, and a diffusion sheet. The diffuser plate and diffusion sheet have the function of diffusing and emitting incident light. The prism sheet has the function of focusing and emitting incident light.

[0020] Next, the configuration of the display area AA in the array substrate 11B constituting the liquid crystal panel 11 will be explained using Figure 4. As shown in Figure 4, at least TFTs (transistors, switching elements) 20 and pixel electrodes 21 are provided on the inner surface of the display area AA of the array substrate 11B. Multiple TFTs 20 and pixel electrodes 21 are arranged in a matrix (arrangement) with spacing along the X-axis and Y-axis directions. Around these TFTs 20 and pixel electrodes 21, gate wiring (scanning wiring) 22 and source wiring (image wiring, signal wiring) 23 are arranged orthogonally (intersecting) with each other. Multiple gate wirings 22 extend along the X-axis direction, with spacing along the Y-axis direction. Scanning signals are supplied to multiple gate wirings 22 from the driver 13 or a circuit section provided on the array substrate 11B. Multiple source wirings 23 extend along the Y-axis direction, with spacing along the X-axis direction. Image signals including grayscale information are supplied to multiple source wirings 23 from the driver 13. The TFT 20 includes a gate electrode 20A connected to the gate wiring 22, a source electrode 20B connected to the source wiring 23, a drain electrode 20C connected to the pixel electrode 21, and a semiconductor portion 20D made of semiconductor material connected to the source electrode 20B and the drain electrode 20C. The TFT 20 is driven based on a scanning signal supplied to the gate electrode 20A by the gate wiring 22. This scanning signal contains a potential higher than the threshold voltage of the TFT 20. As a result, a channel region is created in the semiconductor portion 20D, allowing charge to move between the source electrode 20B and the drain electrode 20C through the channel region. Therefore, the potential related to the image signal supplied to the source electrode 20B by the source wiring 23 is supplied to the drain electrode 20C via the semiconductor portion 20D. Consequently, the pixel electrode 21 is charged with the potential related to the image signal. The pixel electrode 21 is located in a region surrounded by the gate wiring 22 and the source wiring 23, and its planar shape is, for example, a vertically elongated, approximately rectangular shape. Furthermore, the display area AA of the opposing substrate 11A is provided with multiple color filters at positions that are opposite to each pixel electrode 21 on the array substrate 11B.The color filter, together with the opposing pixel electrode 21, constitutes a unit pixel, which will be described later, and is a display unit. Note that on both substrates 11A and 11B, an alignment film (not shown) is formed on the innermost surface (uppermost layer) in contact with the liquid crystal layer to orient the liquid crystal molecules contained in the liquid crystal layer.

[0021] Furthermore, the array substrate 11B may be provided with a common electrode superimposed on all pixel electrodes 21 via an insulating film. The orientation state of liquid crystal molecules contained in the liquid crystal layer can be controlled by utilizing the electric field generated between the common electrode and each pixel electrode 21. When a common electrode is provided on the array substrate 11B, the display mode of the liquid crystal panel 11 is set to IPS (In-Plane Switching) mode or FFS (Fringe Field Switching) mode, etc. On the other hand, a counter electrode may be provided on the inner surface side of the opposing substrate 11A, superimposed on all pixel electrodes 21 via a liquid crystal layer or alignment film. The orientation state of liquid crystal molecules contained in the liquid crystal layer can be controlled by utilizing the electric field generated between the counter electrode and each pixel electrode 21. When a counter electrode is provided on the opposing substrate 11A, the display mode of the liquid crystal panel 11 is set to IPS (In-Plane Switching) mode or FFS (Fringe Field Switching) mode, etc. It may also be set to VA (Vertical Alignment) mode or TN (Twisted Nematic) mode, etc.

[0022] In the liquid crystal display device 10 with the above configuration, as shown in Figure 2, planar light emitted from multiple LEDs 15 provided in the backlight device 12 is irradiated onto the main surface on the back side of the liquid crystal panel 11. In the liquid crystal panel 11, when scanning signals are sequentially supplied to multiple gate wirings 22, multiple TFTs 20 connected to each gate wiring 22 are driven sequentially. When image signals are sequentially supplied to multiple source wirings 23 in synchronization with the timing of the supply of scanning signals to each gate wiring 22, the pixel electrodes 21 connected to the driven TFTs 20 are charged to the potential related to the image signal. The orientation state of the liquid crystal molecules is controlled according to the electric field generated between each pixel electrode 21 and a common electrode or counter electrode, thereby controlling the amount of transmitted light in the liquid crystal panel 11 for each unit pixel. As a result, a predetermined image is displayed in the display area AA of the liquid crystal panel 11.

[0023] In the liquid crystal display device 10 according to this embodiment, so-called local dimming control is performed. Local dimming control is a method of improving the contrast ratio of the displayed image by adjusting the amount of light emitted by a plurality of LEDs 15 provided in the backlight device 12 according to the brightness of the image displayed in the display area AA of the liquid crystal panel 11. Specifically, for example, if the image displayed in the display area AA of the liquid crystal panel 11 includes both bright and dark areas, the amount of light emitted by the LED 15 that supplies light to the bright areas is increased, and the amount of light emitted by the LED 15 that supplies light to the dark areas is decreased or made non-emitting. In order to perform such local dimming control, as shown in Figure 5, the display area AA is first divided into a plurality of dimming areas (segment areas, divided areas) DA. The dimming areas DA are arranged in a matrix in multiples along the X-axis and Y-axis directions within the main surface of the liquid crystal panel 11. Each of the multiple dimming areas DA is illuminated by light from a plurality of LEDs 15 provided in the backlight device 12. In this embodiment, light from one LED 15 is mainly emitted to each dimming area DA. More specifically, although a dimming region DA can be illuminated by light from multiple LEDs 15, the light from one LED 15, which is positioned in a specific location relative to the dimming region DA, accounts for the dominant proportion of the total illumination light for the dimming region DA. Specifically, the dimming region DA is rectangular in shape when viewed in a plane, and the light from one LED 15 positioned near its center is primarily used to illuminate the dimming region DA. In other words, the dimming region DA is configured to include the area that overlaps with the LED 15 and its surrounding area. Thus, in this embodiment, multiple LEDs 15 are individually associated with multiple dimming regions DA, and local dimming control is achieved by controlling the driving of the unit pixels belonging to each dimming region DA and each LED 15 associated with each dimming region DA.

[0024] As shown in Figures 5 and 6, multiple unit pixels are arranged in the dimming region DA. The unit pixels will be explained in detail. First, the color filter provided in the display region AA of the opposing substrate 11A consists of three colors, R (red), G (green), and B (blue), arranged repeatedly in a predetermined order along the X-axis. Each color filter is a strip extending along the Y-axis. These three color filters, together with the pixel electrode 21, constitute the unit pixels: the red pixel RPX, the green pixel GPX, and the blue pixel BPX. In Figure 6, the colors exhibited by each unit pixel are represented by the letters "R," "G," and "B." The three unit pixels, the red pixel RPX, the green pixel GPX, and the blue pixel BPX, constitute a display pixel DPX capable of displaying a predetermined gradation of color. In the dimming region DA, multiple display pixels DPX are arranged in a matrix along the X-axis and Y-axis. In the display region AA of the opposing substrate 11A, light-shielding sections (black matrices) are provided to prevent color mixing by separating each color filter.

[0025] Next, the electrical configuration of the liquid crystal display device 10 will be explained using Figure 7. As shown in Figure 7, the liquid crystal display device 10 includes a control unit 30 that controls the driving of the liquid crystal panel 11 and the backlight device 12, an interface unit 40, and an illuminance sensor 50. The interface unit 40 allows the user of the liquid crystal display device 10 to input desired information to the liquid crystal display device 10. The illuminance sensor 50 can detect ambient light present around the liquid crystal display device 10 and can output a detection signal corresponding to the detected amount of ambient light. The control unit 30 can perform local dimming control based on the detection signal from the illuminance sensor 50. Furthermore, various settings related to local dimming control by the control unit 30 can be changed and adjusted as appropriate by the user of the liquid crystal display device 10 via the interface unit 40. The control unit 30 is provided on the control board 18 shown in Figure 2.

[0026] As shown in Figure 7, the control unit 30 includes an image processing unit 31, a CPU 32, a correction unit 33, a memory 34, an image signal generation unit 35, and a drive signal generation unit 36. The image processing unit 31 processes video signals (image data) supplied from an external host system (external power source) and outputs the processed video signals to the correction unit 33 and the image signal generation unit 35. The processed video signals output from the image processing unit 31 include display gradation information, which is gradation information relating to the image actually displayed in the display area AA. Display gradation information will be explained in detail later. The CPU 32 can control the operation of the correction unit 33. When an instruction is input to the interface unit 40 by the user, the CPU 32 controls the operation of the correction unit 33 based on that instruction. The instructions input to the interface unit 40 may be, for example, as shown in Figure 8, "For a specific area of ​​the display area AA (hereinafter referred to as the first area A1), local dimming control shall be performed, and for the other areas (hereinafter referred to as the second area A2), local dimming control shall not be performed." More specifically, for example, when the liquid crystal display device 10 is used as an indicator in a passenger car, the interface unit 40 designates the area that displays safety-important information (e.g., warning displays) as the first area A1, and the area that displays other information (e.g., information of lower importance than the first area A1) as the second area A2. The first area A1 and the second area A2 shown in Figure 8 each contain multiple dimming areas DA shown in Figure 5. In addition to specifying the first area A1 and the second area A2 in this way by the interface unit 40, it is also possible to set them as default settings in advance during the manufacturing stage.

[0027] As shown in Figure 7, when the CPU 32 receives a detection signal output from the illuminance sensor 50, it controls the operation of the correction unit 33 based on the detection signal. The correction unit 33, controlled by the CPU 32, is capable of correcting the processed video signal output from the image processing unit 31. Local dimming control is realized by the correction of the video signal by the correction unit 33. When correcting a processed video signal, the correction unit 33 can use information stored in the memory 34. The specific correction process by the correction unit 33 will be explained in detail later. The memory 34 stores information such as the data tables DT1 and DT2 shown in Figures 9 and 10. The contents of the data tables DT1 and DT2 will be explained in detail later. The image signal generation unit 35 generates an image signal based on instructions from the correction unit 33 and outputs it to a timing controller (not shown). The image signal is supplied to the driver 13 of the liquid crystal panel 11 at a predetermined timing by the timing controller. The drive signal generation unit 36 ​​generates a drive signal to drive the LEDs 15 based on instructions from the correction unit 33 and outputs it to the LED drive circuit (light source drive unit) 19 provided in the backlight device 12. The drive signal generated by the drive signal generation unit 36 ​​is, for example, a PWM (Pulse Width Modulation) signal. The PWM signal includes an ON period (lighting period) and an OFF period (off period), and the light emission of the LEDs 15 is controlled so that the amount of light emitted corresponds to the duty cycle ratio, which is the time ratio of the ON period to the OFF period. The LED drive circuit 19 drives each LED 15 based on the input drive signal and lights them up to a predetermined amount of light emitted.

[0028] The specific correction processing performed by the control unit 30 will be explained using Figures 9 to 11. As shown in Figure 11, the CPU 32 determines whether or not a detection signal has been input from the illuminance sensor 50 (step S10). If the result of the determination in step S10 is NO, the CPU 32 returns to step S10 and determines again whether or not a detection signal has been input. If the result of the determination in step S10 is YES, the CPU 32 refers to the first data table DT1 of the memory 34 shown in Figure 9 (step S11). Here, the first data table DT1 will be explained. As shown in Figure 9, the first data table DT1 contains the detection signals DS1 to DSN and the correction coefficients C1 to CN associated with the detection signals DS1 to DSN. Note that in Figure 9, the numbers "1 to N" are appended to the end of each code of the detection signals DS1 to DSN and the correction coefficients C1 to CN, which represent the number of each code, and "N" is a natural number. Furthermore, the codes assigned to the first data table DT1 are merely for convenience, and the actual data written to the first data table DT1 can be changed as appropriate to codes other than those shown in the diagram. The numerical values ​​of the correction coefficients C1 to CN are either "1", "a number less than 1", or "a number greater than 1". The correction coefficients whose numerical value is "1" are linked to the detection signal output when the amount of ambient light detected by the illuminance sensor 50 is within a predetermined reference range. This reference range for ambient light is the range in which a sufficiently good image can be viewed without local dimming control when displaying on the liquid crystal panel 11. The correction coefficients whose numerical value is "a number less than 1" are linked to the detection signal output when the amount of ambient light detected by the illuminance sensor 50 falls below a predetermined reference range. The correction coefficients whose numerical value is "a number greater than 1" are linked to the detection signal output when the amount of ambient light detected by the illuminance sensor 50 exceeds a predetermined reference range.

[0029] In step S11, the CPU 32, as shown in Figure 11, refers to the first data table DT1 shown in Figure 9 and causes the correction unit 33 to extract the correction coefficient associated with the input detection signal. Next, the CPU 32 refers to the second data table DT2 of the memory 34 shown in Figure 10 (step S12). The second data table DT2 will now be described. As shown in Figure 10, the second data table DT2 contains grayscale information (R1, G1, B1) ~ (RN, GN, BN), luminance information Br1 ~ BrN, and display grayscale information (r1, g1, b1) ~ (rN, gN, bN), (h1, s1, l1) ~ (hN, sN, lN). Of these, the display gradation information (r1,g1,b1)~(rN,gN,bN) and (h1,s1,l1)~(hN,sN,lN) are the numerical values ​​of the RGB color space and HSL color space in the image actually displayed on the liquid crystal panel 11. Specifically, in the display gradation information (r1,g1,b1)~(rN,gN,bN), "r" is the red gradation value in the RGB color space of the image displayed on the liquid crystal panel 11, "g" is the green gradation value in the RGB color space of the image displayed on the liquid crystal panel 11, and "b" is the blue gradation value in the RGB color space of the image displayed on the liquid crystal panel 11. In the display gradation information (h1,s1,l1)~(hN,sN,lN), "h" represents the hue H in the HSL color space of the image displayed on the liquid crystal panel 11, "s" represents the saturation S in the HSL color space of the image displayed on the liquid crystal panel 11, and "l" represents the lightness L in the HSL color space of the image displayed on the liquid crystal panel 11. In the display gradation information shown in Figure 10, the "R,G,B" column represents the RGB color space, and the "H,S,L" column represents the HSL color space.

[0030] The gradation information (R1, G1, B1) to (RN, GN, BN) shown in Figure 10 are the gradation values ​​of the image signals applied to the unit pixels RPX, GPX, and BPX of each color in the liquid crystal panel 11 via the TFT 20 and source wiring 23. Specifically, in the gradation information (R1, G1, B1) to (RN, GN, BN), "R" is the gradation value of the image signal applied to the red pixel RPX, "G" is the gradation value of the image signal applied to the green pixel GPX, and "B" is the gradation value of the image signal applied to the blue pixel BPX. The luminance information Br1 to BrN are the brightness of each LED 15 in the backlight device 12. The relationship is said to correspond to the luminance L in the HSL color space, which is represented by "l" in the display gradation information (h1, s1, l1) to (hN, sN, lN). Note that in Figure 10, the numbers "1 to N" are appended to the end of each code for grayscale information (R1, G1, B1) ~ (RN, GN, BN) and display grayscale information (r1, g1, b1) ~ (rN, gN, bN), (h1, s1, l1) ~ (hN, sN, lN). This indicates the number of each code, where "N" is a natural number. Specifically, for 8-bit grayscale, "N" would be "256," meaning there would be approximately 16.77 million grayscale and display grayscale data entries. Furthermore, the codes appended to the second data table DT2 are merely for convenience; the actual data written to the second data table DT2 can be changed to codes other than those shown in the figure.

[0031] In step S12, as shown in Figure 11, the CPU 32 refers to the second data table DT2 and instructs the correction unit 33 to multiply the luminance L included in the display gradation information by a correction coefficient to calculate corrected luminance information. For example, as shown in Figure 8, if the first area A1 is specified by the interface unit 40 described above, the CPU 32 instructs the correction unit 33 to multiply the luminance L included in the display gradation information related to the image displayed in the first area A1 by a correction coefficient to calculate corrected luminance information, but does not calculate corrected luminance information for the image displayed in the second area A2. Specifically, if the original display gradation information in the first region A1 (processed video signal processed by the image processing unit 31) has RGB color space (R, G, B) values ​​of (15, 143, 58) and HSL color space (H, S, L) values ​​of (140, 207, 79), and the correction coefficient is "2", then the corrected luminance information value will be "158", which is twice the luminance L value (79). As shown in Figure 10, the gradation information associated with the original display gradation information is (RNa, GNb, BNc).

[0032] Subsequently, as shown in Figure 11, the CPU 32 refers to the second data table DT2 and instructs the correction unit 33 to extract display gradation information for the first region A1, including hue H, saturation S, and luminance L that matches the corrected luminance information (step S13). In the above example, display gradation information is extracted in which the values ​​of each HSL color space (H, S, L) are (140, 207, 158). Subsequently, the CPU 32 refers to the second data table DT2 and instructs the correction unit 33 to extract gradation information associated with the extracted display gradation information for the first region A1 (step S14). In the above example, gradation information (RNd, GNe, BNf) associated with the display gradation information in the second data table DT2 in which the values ​​of each HSL color space (H, S, L) are (140, 207, 158) is extracted. Subsequently, the CPU 32 controls the correction unit 33 to cause the image signal generation unit 35 to generate an image signal based on the extracted gradation information, and the drive signal generation unit 36 ​​to generate a drive signal based on the corrected brightness information (step S15).

[0033] Specifically, as shown in Figure 8, the image signal generation unit 35 generates each image signal such that the gradation value of the image signal assigned to the red pixel RPX located in the first region A1 becomes "RNd" included in the corrected display gradation information, the gradation value of the image signal assigned to the green pixel GPX located in the first region A1 becomes "GNe" included in the corrected display gradation information, and the gradation value of the image signal assigned to the blue pixel BPX located in the first region A1 becomes "BNf" included in the corrected display gradation information. On the other hand, the image signal generation unit 35 generates each image signal such that the gradation value of the image signal assigned to the red pixel RPX located in the second region A2 becomes "RNa" included in the original (uncorrected) display gradation information, the gradation value of the image signal assigned to the green pixel GPX located in the first region A1 becomes "GNb" included in the original display gradation information, and the gradation value of the image signal assigned to the blue pixel BPX located in the first region A1 becomes "BNc" included in the original display gradation information. As shown in Figure 8, the drive signal generation unit 36 ​​generates a PWM signal with an adjusted duty cycle to provide corrected brightness information to the first LED (first light source) 15α, which is superimposed on the first region A1, among the multiple LEDs 15. On the other hand, the drive signal generation unit 36 ​​generates a PWM signal with a duty cycle that represents the brightness L included in the original display gradation information, i.e., uncorrected brightness information, to provide a drive signal to the second LED (second light source) 15β, which is superimposed on the second region A2, among the multiple LEDs 15.

[0034] Here, if, in the example described above, the output image data is generated by applying a predetermined brightness conversion process to the input image data as in the conventional method, the gradation values ​​of the RGB color space (R, G, B) of the corrected display gradation information will be (25, 237, 96), and the values ​​of the HSL color space (H, S, L) will be (140, 217, 130). In other words, with the conventional brightness conversion process, both the hue H and saturation S are different from the original display gradation information (hue H is 140, saturation S is 207), so the color of the image that is actually displayed is different from the original, resulting in poor display quality. In contrast, according to this embodiment, both the hue H and saturation S in the corrected display gradation information match the original display gradation information, so the color of the image that is actually displayed is the original, and thus high display quality can be obtained.

[0035] As described above, the liquid crystal display device (display device) 10 of this embodiment comprises a liquid crystal panel (display panel) 11 having a display surface 11DS, a driver (image display unit) 13 that displays an image on the display surface 11DS based on gradation information contained in display gradation information (image data) supplied from an external source, a backlight device (illumination device) 12 having a plurality of LEDs (light sources) 15 that irradiate the liquid crystal panel 11 with light for display, an LED drive circuit (light source drive unit) 19 that drives the plurality of LEDs 15 based on brightness information contained in the display gradation information, an illuminance sensor 50 that detects ambient light and outputs a detection signal corresponding to the detected amount of ambient light, and a control unit 30. The control unit 30 corrects the brightness information based on the detection signal and controls the LED drive circuit 19 to drive the plurality of LEDs 15 based on the corrected brightness information, and also corrects the gradation information based on the detection signal and controls the driver 13 to display an image based on the corrected gradation information.

[0036] When ambient light is detected by the illuminance sensor 50, the illuminance sensor 50 outputs a detection signal corresponding to the detected amount of ambient light. Based on the detection signal output from the illuminance sensor 50, the control unit 30 corrects the brightness information and grayscale information included in the display grayscale information supplied from an external source. The LED drive circuit 19 is controlled by the control unit 30 to drive the LED 15 based on the corrected brightness information. The driver 13 is controlled by the control unit 30 to display an image on the display surface 11DS based on the corrected grayscale information. In this way, the amount of light emitted by the LED 15 driven by the LED drive circuit 19 and the image displayed on the display surface 11DS each reflect the detection signal detected by the illuminance sensor 50, so that the actual display grayscale in the image is closer to the original display grayscale compared to conventional systems. This improves the display quality.

[0037] Furthermore, the control unit 30 controls the driver 13 to display an image based on corrected gradation information for the first region A1 included in the display surface 11DS, and to display an image based on uncorrected gradation information for the second region A2 other than the first region A1. The control unit 30 also controls the LED drive circuit 19 to drive the first LED (first light source) 15α, which is superimposed on the first region A1, based on corrected brightness information, and the second LED (second light source) 15β, which is other than the first LED 15α, based on uncorrected brightness information. For example, if the display surface 11DS includes a region where an important image is displayed, that region is designated as the first region A1, and any region where an image of lower importance than the first region A1 is displayed is designated as the second region A2. In the first region A1, an image based on gradation information corrected by the driver 13 is displayed, and the first LED 15α, which is superimposed on the first region A1, is driven by the LED drive circuit 19 based on corrected brightness information. As a result, the images displayed in the first area A1 reflect the detection signals detected by the illuminance sensor 50, thereby improving the visibility of important images. Although the images displayed in the second area A2 do not reflect the detection signals detected by the illuminance sensor 50, this is not a significant problem as these images are of lower importance compared to those displayed in the first area A1.

[0038] The control unit 30 also includes a correction unit 33 that corrects brightness information and gradation information, a drive signal generation unit 36 ​​that generates a drive signal for driving the LED 15 based on the brightness information corrected by the correction unit 33 and outputs the drive signal to the LED drive circuit 19, and an image signal generation unit 35 that generates an image signal for displaying an image on the display surface 11DS based on the gradation information corrected by the correction unit 33 and outputs the image signal to the driver 13. The correction unit 33 corrects the brightness information and gradation information included in the display gradation information based on the detection signal output from the illuminance sensor 50. The drive signal generation unit 36 ​​generates a drive signal for driving the LED 15 based on the brightness information corrected by the correction unit 33 and outputs it to the LED drive circuit 19. The LED drive circuit 19 drives the LED 15 with the drive signal output from the drive signal generation unit 36. The image signal generation unit 35 generates an image signal for displaying an image on the display surface 11DS based on the gradation information corrected by the correction unit 33 and outputs it to the driver 13. The driver 13 displays an image on the display surface 11DS using the image signal output from the image signal generation unit 35. In this way, by including the correction unit 33, the drive signal generation unit 36, and the image signal generation unit 35 in the control unit 30, the detection signal detected by the illuminance sensor 50 can be reflected in the light emission amount of the LED 15 and the image displayed on the display surface 11DS, respectively.

[0039] Furthermore, the control unit 30 has a memory 34 that stores a first data table DT1 containing multiple correction coefficients and detection signals related to brightness information, and a second data table DT2 containing multiple display gradation information, gradation information, and brightness information. In the first data table DT1, correction coefficients are associated with detection signals, and in the second data table DT2, gradation information and brightness information are associated with display gradation information, and the display gradation information includes hue H, saturation S, and brightness L of the HSL color space, and the brightness information matches the brightness L. The control unit 30, by referring to the first data table DT1, extracts a correction coefficient associated with the detection signal output from the illuminance sensor 50, and corrects the luminance information by multiplying the extracted correction coefficient with the luminance information. It also refers to the second data table DT2, extracts display gradation information including the hue H and saturation S contained in the display gradation information supplied from an external source, and the luminance L that matches the corrected luminance information, as corrected display gradation information, and extracts the gradation information associated with the corrected display gradation information as corrected gradation information. In this way, the control unit 30 can easily correct the luminance information and gradation information by referring to the first data table DT1 and the second data table DT2 stored in the memory 34.

[0040] <Other Embodiments> The technology disclosed herein is not limited to the embodiments described above in the description and drawings, but also includes, for example, the following embodiments.

[0041] (1) It is also possible to correct the gradation information based on the detection signal from the illuminance sensor 50 across the entire display area AA without performing local dimming control, and to display the image based on the corrected gradation information.

[0042] (2) The specific size of the LED15 as viewed in a plane and the spacing between them as viewed in a plane can be changed as appropriate, in addition to the figures shown in Figure 3. Mini LEDs, micro LEDs, etc. can also be used as LED15.

[0043] (3) In addition to the configuration shown in Figure 5, it is also possible to configure the system so that multiple LEDs 15 are arranged in a single dimming region DA.

[0044] (4) The arrangement of unit pixels can be changed as appropriate, in addition to the arrangement shown in Figure 6.

[0045] (5) The specific electrical configuration of the liquid crystal display device 10 can be changed as appropriate in addition to what is shown in Figure 7.

[0046] (6) The specific ranges of the first region A1 and the second region A2, and the specific number of the first LED 15α and the second LED 15β can be changed as appropriate, in addition to those shown in Figure 8. The specific number of dimming regions DA included in the first region A1 and the second region A2 can be set arbitrarily; for example, it is possible to set the first region A1 to contain only one dimming region DA.

[0047] (7) The specific contents of the first data table DT1 can be changed as appropriate, in addition to what is shown in Figure 9.

[0048] (8) The specific contents of the second data table DT2 can be changed as appropriate, in addition to what is shown in Figure 10.

[0049] (9) The specific processing procedure for the correction process by the correction unit 33 can be modified as appropriate in addition to the procedure shown in Figure 11.

[0050] (10) The color exhibited by a unit pixel may include colors other than red, green, and blue (for example, yellow or colorless / transparent).

[0051] (11) The driver 13 may be mounted on the flexible substrate 14 using COF (Chip On Film) mounting.

[0052] (12) The planar shape of the liquid crystal panel 11 may be a vertically elongated rectangle, square, circle, semicircle, vertically elongated oval, ellipse, trapezoid, etc.

[0053] (13) The liquid crystal display device 10 may be used for purposes other than in vehicles. [Explanation of Symbols]

[0054] 10...Liquid crystal display device (display device), 11...Liquid crystal panel (display panel), 11DS...Display surface, 12...Backlight device (lighting device), 13...Driver (image display unit), 15...LED (light source), 15α...First LED (first light source), 15β...Second LED (second light source), 19...LED drive circuit (light source drive unit), 30...Control unit, 33...Correction unit, 34...Memory, 35...Image signal generation unit, 36...Drive signal generation unit, 50...Illuminance sensor, A1...First area, A2...Second area, DT1...First data table, DT2...Second data table

Claims

1. A display panel having a display surface, An image display unit that displays an image on the display surface based on grayscale information contained in image data supplied from an external source, An illumination device having multiple light sources that irradiates the display panel with light for display, A light source drive unit that drives a plurality of light sources based on brightness information contained in the image data, An illuminance sensor that detects ambient light and outputs a detection signal corresponding to the detected amount of ambient light, It comprises a control unit and, The control unit corrects the brightness information based on the detection signal and controls the light source drive unit to drive a plurality of light sources based on the corrected brightness information, and the display device corrects the grayscale information based on the detection signal and controls the image display unit to display the image based on the corrected grayscale information.

2. The display device according to claim 1, wherein the control unit controls the image display unit to display the image in a first region included in the display surface based on the corrected gradation information, and in a second region other than the first region based on the uncorrected gradation information, and controls the light source drive unit to drive a first light source among the plurality of light sources that overlaps with the first region based on the corrected brightness information, and drives a second light source other than the first light source based on the uncorrected brightness information.

3. The display device according to claim 1 or 2, wherein the control unit comprises a correction unit for correcting the brightness information and the grayscale information, a drive signal generation unit for generating a drive signal for driving the light source based on the brightness information corrected by the correction unit and outputting the drive signal to the light source drive unit, and an image signal generation unit for generating an image signal for displaying the image on the display surface based on the grayscale information corrected by the correction unit and outputting the image signal to the image display unit.

4. The control unit has a memory that stores a first data table containing multiple correction coefficients and detection signals related to the brightness information, and a second data table containing multiple image data, grayscale information, and brightness information. In the first data table, the correction coefficient is associated with the detection signal. In the second data table, the gradation information and the brightness information are associated with the image data, and the image data includes hue H, saturation S, and brightness L of the HSL color space, and the brightness information matches the brightness L. The display device according to claim 1 or 2, wherein the control unit refers to the first data table to extract the correction coefficient associated with the detection signal output from the illuminance sensor, corrects the luminance information by multiplying the extracted correction coefficient with the luminance information, and refers to the second data table to extract the image data including the hue H and saturation S contained in the image data supplied from an external source and the luminance L that matches the corrected luminance information as the corrected image data, and extracts the gradation information associated with the corrected image data as the corrected gradation information.

Images