Image display control device, image display system, and image display control method

Abstract

This device detects abnormalities in the brightness control unit, which controls the brightness of multiple light sources, and is installed in an image display control device. [Solution] The image display control device includes: a brightness control unit that generates backlight control information used to control multiple light sources included in the backlight based on first image information indicating an input image; a pixel compensation unit that corrects the pixel values ​​included in the first image information based on the brightness of the multiple light sources to generate second image information indicating an output image; a first statistical acquisition unit that acquires first statistical data of the pixel values ​​included in the first image information; a second statistical acquisition unit that acquires second statistical data of the brightness values ​​of each light source included in the backlight control information; and an abnormality detection unit that detects an abnormality in the backlight control information generation process in the brightness control unit when the second statistical data does not fall within the range between the upper and lower limits determined by the first statistical data and no switching of image content has occurred.

Description

Technical Field

[0001] The present invention relates to an image display control device, an image display system, and an image display control method.

Background Art

[0002] Recently, in an image display control device for displaying on a display device having a backlight in which a plurality of light sources are arranged in an array, local dimming for adjusting the luminance of each light source according to the luminance of an input image is known. By local dimming, it becomes possible to improve the contrast ratio while reducing power consumption.

[0003] A backlight unit including a plurality of LED elements capable of independently controlling the light emission amount and a plurality of optical sensors for detecting the light emission luminance of each LED element is known. In this type of backlight unit, when any one of the optical sensors fails, the luminance of the LED element corresponding to the failed optical sensor is estimated using another optical sensor instead of the failed optical sensor (see, for example, Patent Document 1).

[0004] When any one of a plurality of light emitting regions included in a light source for illuminating a liquid crystal panel fails, a method of moving an image of a display region corresponding to the failed light emitting region to a display region corresponding to a normal light emitting region is known (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] For example, an image display control device that performs local dimming has a brightness control unit that adjusts the brightness of multiple light sources according to the brightness of the input image, and a pixel compensation unit that adjusts the brightness of the image according to the brightness of the adjusted light sources. If an abnormality occurs in the brightness control unit, the brightness or color of the image displayed on the display device may change.

[0007] For example, some abnormalities in the brightness control unit can be detected by CRC (Cyclic Redundancy Check) checks, which detect abnormalities in communication between the brightness control unit and the driver that drives the light source. However, if, for example, an image (video) is displayed while each light source is still emitting light, it is difficult to verify the validity of whether the brightness output value from the brightness control unit to the driver is normal. For example, it is possible to determine abnormalities in the brightness output value by implementing the same circuit in parallel and comparing the two outputs. However, in this case, the circuit size increases, and the cost of the image display control device increases.

[0008] The present invention has been made in view of the above points, and aims to detect an abnormality in a brightness control unit that controls the brightness of multiple light sources, which is mounted on an image display control device having a local dimming function. [Means for solving the problem]

[0009] In one aspect of the present invention, the image display control device is an image display control device having a local dimming function, and includes: a brightness control unit that generates backlight control information used to control a plurality of light sources included in a backlight based on first image information indicating an input image; a pixel compensation unit that generates second image information indicating an output image by correcting the pixel values ​​included in the first image information based on the brightness of the plurality of light sources; a first statistical acquisition unit that acquires first statistical data of the pixel values ​​included in the first image information; a second statistical acquisition unit that acquires second statistical data of the brightness values ​​of each light source included in the backlight control information; and an abnormality detection unit that detects an abnormality in the backlight control information generation process in the brightness control unit when the second statistical data does not fall within the range between the upper and lower limits determined by the first statistical data and no switching of image content has occurred. [Effects of the Invention]

[0010] According to the disclosed technology, it is possible to detect abnormalities in a brightness control unit that controls the brightness of multiple light sources, which is mounted on an image display control device having a local dimming function. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing an example of an image display system in the first embodiment. [Figure 2] Figure 1 is a block diagram showing an example of a display controller. [Figure 3] This block diagram shows an example of the local dimming section in Figure 2. [Figure 4] This figure shows an example of controlling the brightness of the backlight using the brightness control unit shown in Figure 3. [Figure 5] This figure shows an example of generating a luminance distribution using the luminance distribution calculation unit in Figure 3. [Figure 6] This figure shows an example of how the RGB correction unit in Figure 3 corrects the brightness of an image. [Figure 7]It is a diagram showing an example of the statistical information acquired by the input color statistics acquisition unit and the output luminance statistics acquisition unit in FIG. 3. [Figure 8] It is a diagram showing an example of a threshold value used for determination of an abnormality of the luminance control unit in FIG. 3. [Figure 9] It is a flowchart showing an example of a process for determining an abnormality of the luminance control unit by the processor in FIG. 3. [Figure 10] It is a flowchart showing an example of the process of step S80 in FIG. 9. [Figure 11] It is a block diagram showing an example of a display controller in the second embodiment. [Figure 12] It is a block diagram showing an example of an input color statistics acquisition unit, an output luminance statistics acquisition unit, and an output color statistics acquisition unit connected to the local dimming unit in FIG. 11. [Figure 13] It is a diagram showing an example of the statistical data acquired by the input color statistics acquisition unit, the output luminance statistics acquisition unit, and the output color statistics acquisition unit in FIG. 12. [Figure 14] It is a diagram showing an example of a threshold value used for determination of an abnormality of the luminance control unit in FIG. 12. [Figure 15] It is a flowchart showing an example of a process for determining an abnormality of the luminance control unit by the processor in FIG. 12.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments will be described with reference to the drawings. In the following description, image data may sometimes be simply referred to as an image.

[0013] (First Embodiment) FIG. 1 is a block diagram showing an example of an image display system in the first embodiment. The image display system 1 shown in FIG. 1 includes a head unit 10, a serializer 20, a deserializer 30, and a display controller 40, and a display device 70 including a display 50 and a backlight 60.

[0014] The head unit 10 generates an image to be displayed on the display 50. Also, the head unit 10 outputs the image data 10a and the control information 10b corresponding to the generated image to the serializer 20. For example, the control information 10b includes information used for controlling the display of an image on the display 50. For example, the image data 10a may include an overlay image such as an icon overlaid on the original image.

[0015] The serializer 20 converts the image data 10a and the control information 10b output from the head unit 10 into serial data 20a. The serializer 20 transmits the serial data 20a obtained by the conversion to the deserialzier 30 via a single video link (transmission line). Although not particularly limited, the transmission and reception of the serial data 20a via the video link are performed using an interface such as LVDS (Low Voltage Differential Signaling) or APIX (Automotive Pixel Link: registered trademark).

[0016] The deserialzier 30 converts the serial data 20a received via the video link into image data 30a and control information 30b. The image data 30a and the control information 30b respectively correspond to the original image data 10a and the control information 10b output by the head unit 10. The deserialzier 30 outputs the image data 30a and the control information 30b obtained by the conversion to the display controller 40.

[0017] Based on the image data 30a and the control information 30b received from the deserialzier 30, the display controller 40 outputs information 40a including image data indicating the image to be displayed on the display 50 to the display 50. Also, based on the image data 30a and the control information 30b, the display controller 40 outputs information 40b for controlling the luminance of the backlight 60 to the backlight 60. The display controller 40 is an example of an image display control device.

[0018] Although not particularly limited, the image data input to the display controller 40 and the image data output from the display controller 40 include pixel values ​​of red (R) pixels, green (G) pixels, and blue (B) pixels that represent the RGB color space.

[0019] The display 50 is, for example, a liquid crystal display including a liquid crystal shutter that adjusts the transmittance of light emitted from the backlight 60 and a color filter that receives the light transmitted through the liquid crystal shutter. Note that the display 50 may be a display other than a liquid crystal display, as long as it allows for adjustment of the transmittance of light emitted from the backlight 60. The display 50 is an example of a display unit.

[0020] The backlight 60 includes multiple LED (Light Emitting Diode) light sources arranged in a matrix and is positioned opposite the image display surface of the display 50. Hereinafter, the light illumination zones corresponding to each LED light source in the display 50 will be referred to as LED zones. Note that the backlight 60 may have other light sources with adjustable brightness instead of multiple LED light sources arranged in a matrix.

[0021] For example, the image display system 1 may be mounted in a vehicle. In this case, the display device 70 may be used, for example, to display the instrument cluster on the instrument panel or the center information display (CID). Alternatively, the display device 70 may be used as a head-up display that projects an image onto the windshield.

[0022] The image display system 1 installed in the vehicle is designed to meet the requirements of ASIL (Automotive Safety Integrity Level). The image display system 1, which is equipped with a backlight and local dimming function, is not limited to in-vehicle applications and may be used in other image display systems such as digital signage.

[0023] For example, the display controller 40 performs local dimming, which adjusts the brightness of multiple LED backlights independently of each other according to the brightness (e.g., pixel value) of the image displayed on the display 50. In addition, the display controller 40 performs compensation control during local dimming to suppress the increase in brightness of the surrounding image due to light leaking around the position opposite the lit LED backlight. Local dimming can improve the reproduction of black in the image displayed on the display 50 while suppressing the power consumption of the backlight 60.

[0024] Figure 2 is a block diagram showing an example of the display controller 40 in Figure 1. The display controller 40 is, for example, a semiconductor integrated circuit and has a display engine 200, a memory 300, and a processor 400 that are interconnected via a bus 500.

[0025] The display engine 200 includes an image input unit 210, a memory 220, a warping unit 230, an input color statistics acquisition unit 240, a local dimming unit 250, an output brightness statistics acquisition unit 260, an image output unit 270, and a register interface 280. The local dimming unit 250 includes a brightness control unit 251 and a pixel compensation unit 252. For example, each element of the display engine 200 operates based on control from the processor 400. The display engine 200 processes image data representing the RGB color space, although this is not particularly limited.

[0026] The image input unit 210 receives image data (for example, input images in frame units) transmitted from the deserializer 30 in Figure 1 and stores the received image data in the memory 220. The warping unit 230 uses the image data stored in the memory 220 to perform distortion correction processing to display a distortion-free image on the display 50 in Figure 1. The warping unit 230 outputs the distortion-corrected input image data VIN to the local dimming unit 250.

[0027] The input color statistics acquisition unit 240 sequentially acquires the average input video luminance AIVB, which is the average of the pixel values ​​for one screen (one frame) contained in the input image data VIN input from the warping unit 230 to the local dimming unit 250. For example, the input color statistics acquisition unit 240 acquires the average input video luminance AIVB by calculation. The average input video luminance AIVB is an example of first statistical data. The input image data VIN is an example of first image information, and the input color statistics acquisition unit 240 is an example of a first statistical acquisition unit.

[0028] The input color statistics acquisition unit 240 outputs the acquired average input video luminance AIVB to the processor 400 via the register interface 280 and the bus 500. The input color statistics acquisition unit 240 may also have a storage unit such as a buffer that holds the average input video luminance AIVB. In this case, the average input video luminance AIVB held in the storage unit may be read by the processor 400.

[0029] The display controller 40 has a local dimming function. Specifically, the brightness control unit 251 of the local dimming unit 250 generates a backlight control signal BLCNT that adjusts the brightness of the backlight 60 in Figure 1 based on the input image data VIN, and outputs the generated backlight control signal BLCNT to the backlight 60.

[0030] Furthermore, the brightness control unit 251 outputs brightness information LINF, which indicates the brightness of each of the multiple LED light sources of the backlight 60, to the output brightness statistics acquisition unit 260. For example, the brightness information LINF may contain the same information as the information contained in the backlight control signal BLCNT, which indicates the brightness of each of the multiple LED light sources, or it may be the backlight control signal BLCNT itself. The method of adjusting the brightness of the backlight 60 by the brightness control unit 251 is explained in Figure 4. The brightness information LINF and the backlight control signal BLCNT are examples of backlight control information.

[0031] The pixel compensation unit 252 of the local dimming unit 250 corrects the pixel values ​​(e.g., brightness values) of the input image data VIN based on the brightness of the backlight 60 adjusted by the brightness control unit 251, and outputs them to the image output unit 270 as output image data VOUT. Output image data VOUT is an example of second image information. For example, the pixel compensation unit 252 corrects the pixel values ​​in areas where the brightness of the backlight 60 is high by making them relatively smaller, and the pixel values ​​in areas where the brightness of the backlight 60 is low by making them relatively larger. At this time, the pixel compensation unit 252 corrects the pixel values ​​while taking into account the light leakage to the surroundings of each LED light source. The image correction method by the local dimming unit 250 is explained in Figures 5 and 6.

[0032] The output luminance statistics acquisition unit 260 sequentially acquires the luminance information LINF output from the local dimming unit 250 for each screen (each frame). The output luminance statistics acquisition unit 260 acquires the average backlight luminance ABB, which is the average luminance of each LED light source included in the luminance information LINF. For example, the output luminance statistics acquisition unit 260 acquires the average backlight luminance ABB by calculation. The average backlight luminance ABB is an example of second statistical data. The output color statistics acquisition unit 290 is an example of a second statistical acquisition unit.

[0033] The output brightness statistics acquisition unit 260 outputs the acquired average backlight brightness ABB to the processor 400 via the register interface 280 and the bus 500. The output brightness statistics acquisition unit 260 may also have a storage unit such as a buffer that holds the average backlight brightness ABB. In this case, the average backlight brightness held in the storage unit may be read by the processor 400.

[0034] The image output unit 270 transmits the output image data VOUT (for example, an output image in frame units) received from the local dimming unit 250 to the display 50 in Figure 1, causing the display 50 to display the image.

[0035] Memory 300 holds, for example, an image display control program executed by the processor 400 and data used by the image display control program. The processor 400 is a controller such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). For example, the processor 400 controls the operation of the display controller 40 by executing the image display control program.

[0036] Furthermore, the processor 400, for example, by executing an image display control program, detects an abnormality in the brightness control unit 251 based on the average input video brightness AIVB acquired by the input color statistics acquisition unit 240 and the average backlight brightness ABB acquired by the output brightness statistics acquisition unit 260. In the processor 400, the function unit for detecting an abnormality in the brightness control unit 251 is an example of an abnormality detection unit. The processor 400 can be made to facilitate or difficult to detect abnormalities based on threshold information received from outside the processor 400. The threshold information may be supplied from outside the image display system 1.

[0037] Furthermore, if the processor 400 has not acquired either or both of the average input video brightness AIVB from the input color statistics acquisition unit 240 and the average backlight brightness ABB from the output brightness statistics acquisition unit 260, it will suppress the abnormality detection process of the brightness control unit 251. The abnormality detection process of the brightness control unit 251 is explained in Figures 7 to 10.

[0038] Figure 3 is a block diagram showing an example of the local dimming unit 250 in Figure 2. In Figure 3, the register interface 280 and bus 500 shown in Figure 2 are omitted. The pixel compensation unit 252 of the local dimming unit 250 includes a brightness distribution calculation unit 253, an RGB correction unit 254, and a saturation processing unit 255.

[0039] The luminance distribution calculation unit 253 receives luminance information LINF, which indicates the luminance of each LED light source, and LSF (Lighting Spread Function), which is the luminance distribution function when only one LED light source is lit, from the luminance control unit 251. Based on the luminance information LINF and the luminance distribution function LSF, the luminance distribution calculation unit 253 generates a luminance distribution of the backlight 60 that takes into account the light leakage to the surroundings for each LED light source, and outputs information indicating the generated luminance distribution to the RGB correction unit 254. For example, the luminance distribution generated by the luminance distribution calculation unit 253 shows the distribution of the luminance values ​​of the backlight 60 for each of the pixels of the display 50, and is shown as a value greater than 0 and less than or equal to 1. Here, the lower the luminance value of the luminance distribution, the closer it is to 0, and the higher it is, the closer it is to 1.

[0040] The RGB correction unit calculates the pixel value gain to be applied to each pixel of the display 50 based on the luminance distribution (luminance value) using equation (1). From equation (1), the minimum gain is 1, and the maximum gain is infinity. Here, infinity is the maximum value that can be represented by the number of bits representing the gain. Gain = 1 / luminance distribution ... (1)

[0041] Furthermore, the RGB correction unit 254 uses equations (2-1), (2-2), and (2-3) to calculate a correction value for each color component pixel value by multiplying the pixel value of each color component of each pixel included in the input image data VIN by the gain calculated in equation (1). The symbol R in equation (2-1) represents the pixel value of a red pixel. The symbol G in equation (2-2) represents the pixel value of a green pixel. The symbol B in equation (2-3) represents the pixel value of a blue pixel. R = R × Gain ... (2-1) G = G × Gain ... (2-2) B = B × Gain ... (2-3)

[0042] For example, the pixel values ​​for each color component of the input image data VIN are normalized to be between 0 and 1. Therefore, when the image input unit 210 in Figure 2 receives 8-bit image data (0 to 255) for each pixel, the maximum value 255 becomes 1 in the input image data VIN. The RGB correction unit 254 outputs the calculated correction value of the pixel value as image data VC to the saturation processing unit 255.

[0043] For example, each pixel value of image data VC is represented by 12 bits, with a minimum value of 0 and a maximum value of 4095. Note that each pixel value of image data VC may also be represented by a number of bits other than 12 (e.g., 10 bits or 14 bits). Furthermore, if each pixel value of input image data VIN is represented by 8 bits (from 0 to 255), each pixel value of image data VC may be represented by 20 bits (from 0 to 1048576).

[0044] The saturation processing unit 255 sets the largest pixel value of the image data VC to 1 and normalizes the other pixel values ​​to be between 0 and 1, thereby generating the output image data VOUT. The saturation processing unit 255 outputs the generated output image data VOUT to the display 50.

[0045] Figure 4 shows an example of controlling the brightness of the backlight 60 by the brightness control unit 251 in Figure 3. For example, the brightness control unit 251 determines the maximum pixel value ZMAX and the average pixel value ZAVE for each region corresponding to the LED zone of the backlight 60 in the input image data VIN corresponding to the input image. Here, the maximum value ZMAX and the average value ZAVE are determined from the pixel values ​​of the red, green, and blue pixels corresponding to each LED zone, with the maximum value being "1" and the minimum value being "0".

[0046] The brightness control unit 251 then uses equation (3) to calculate the brightness for each LED zone, outputs a backlight control signal BLCNT indicating the calculated brightness to the backlight 60, and outputs brightness information LINF to the pixel compensation unit 252 and the output brightness statistics acquisition unit 260. In equation (3), the symbol α is a parameter for adjusting the brightness, and is set to, for example, 0 or more and 1 or less. For example, if the brightness adjustment parameter α is 0.5, the maximum value ZMAX and the average value ZAVE are mixed by 50% each. For example, the brightness adjustment parameter α may be set by the user using the image display system 1, or it may be set externally. Brightness of each LED zone = α × ZMAX + (1 - α) × ZAVE ... (3)

[0047] Figure 5 shows an example of generating a luminance distribution using the luminance distribution calculation unit 253 in Figure 3. Since the light emitted from each LED light source spreads to adjacent LED zones, the luminance distribution is determined by taking into account the spread (blooming) of light. The luminance distribution calculation unit 253 obtains the luminance distribution by convolution and integration of the luminance information LINF for each LED zone of the backlight 60 and the luminance distribution function LSF.

[0048] In the equation shown in Figure 5, the sign x represents the horizontal coordinate that identifies the LED zone, and the sign y represents the vertical coordinate that identifies the LED zone. bl(x', y') represents the luminance of each LED zone, and lsf(x-x', y-y') represents the luminance distribution function LSF. The brackets in Figure 5 show an image of how the luminance distribution is obtained by convolution integral when two LED light sources are lit and the other LED light source is off.

[0049] Figure 6 shows an example of correcting the brightness of an image using the RGB correction unit 254 in Figure 3. When the input image data VIN is output as output image data VOUT without being corrected according to the brightness distribution, the brightness of the image displayed on the display 50 will be the product of the brightness of the input image and the brightness of the backlight, so an image with the correct brightness will not be displayed.

[0050] Therefore, the RGB correction unit 254 uses equation (1) to calculate the gain for each pixel (each of RGB) of the input image data VIN, and multiplies the pixel value of the input image data VIN by the calculated gain to correct the pixel value and offset the brightness of the backlight 60. This makes it possible to correctly set the brightness of the image displayed on the display 50 using light from the backlight 60, in which the brightness of the LED light source is individually adjusted according to the brightness of the image.

[0051] In the pixel value saturation processing by the saturation processing unit 255 in Figure 3, the maximum value Vmax of all pixel values ​​included in the image data VC is set to 1, which is the pixel value of the output image data VOUT.

[0052] Figure 7 shows an example of statistical information acquired by the input color statistics acquisition unit 240 and the output luminance statistics acquisition unit 260 in Figure 3.

[0053] The input color statistics acquisition unit 240 calculates the maximum pixel value MAX (the maximum value among the pixel values ​​of red, green, and blue pixels) for each pixel of the input image data VIN in each frame. Then, the input color statistics acquisition unit 240 calculates the average input video luminance AIVB by dividing the sum of the maximum values ​​MAX of all pixels by the total number of pixels. Figure 7 shows an example of the calculation by the input color statistics acquisition unit 240 when the number of pixels is "4" (2 horizontal pixels, 2 vertical pixels).

[0054] The output luminance statistics acquisition unit 260 acquires the luminance (set luminance) of each LED light source of the backlight 60 based on the luminance information LINF received from the luminance control unit 251. The output luminance statistics acquisition unit 260 obtains the average backlight luminance ABB by dividing the sum of the acquired luminances of each LED light source by the total number of LED light sources. Figure 7 shows an example of the calculation by the output luminance statistics acquisition unit 260 when there are 10 LED light sources (5 horizontal and 2 vertical).

[0055] Figure 8 shows an example of thresholds used to determine abnormalities in the brightness control unit 251 of Figure 3. The processor 400 determines whether there are any abnormalities in the brightness of the backlight 60 for each input image data VIN of one frame. For example, the processor 400 determines an upper threshold and a lower threshold, which are the range of normal brightness of the backlight 60, based on the average input video brightness AIVB of the target frame acquired by the input color statistics acquisition unit 240. The upper threshold is an example of an upper limit value, and the lower threshold is an example of a lower limit value.

[0056] For example, in the pixel region corresponding to an LED zone, which is the illumination zone of a single LED light source, if the pixel value of at least one pixel is "1" (i.e., white), then the maximum value ZMAX in equation (3) becomes "1". In equation (3), if the maximum value ZMAX is "1" and the brightness adjustment parameter α is greater than "0", then the brightness of the LED zone calculated by equation (3) is higher than the average value ZAVE of the pixel region corresponding to the LED zone, and thus represents the upper limit. Therefore, by applying this condition (ZMAX="1") to equation (3) and using the average input video brightness AIVB instead of the average value ZAVE of the pixel region corresponding to the LED zone in equation (3), the upper limit threshold is calculated by equation (4). Upper threshold = α + (1 - α) × AIVB ... (4)

[0057] Furthermore, the luminance of each LED zone shown in equation (3) becomes the average value ZAVE when the luminance adjustment parameter α is "0". Therefore, by applying this condition (α="0") to equation (3) and using the average input video luminance AIVB instead of the average value ZAVE of the pixel values ​​corresponding to the LED zones in equation (3), the lower threshold can be determined by equation (5). Lower threshold = AIVB ...(5)

[0058] For example, if α = 0.5 and the average input video brightness AIVB of the frame to be judged = 0.5, the upper threshold is 0.75 from equation (4), and the lower threshold is 0.5 from equation (5).

[0059] The processor 400 then determines that the brightness control unit 251 is abnormal (black circle, NG) if the average backlight brightness ABB is not within the range between the upper and lower thresholds of the average input video brightness AIVB for the frame under judgment. For example, an abnormality in the brightness control unit 251 occurs due to an abnormality in the generation process of brightness information LINF and backlight control signal BLCNT. On the other hand, the processor 400 determines that the brightness control unit 251 is normal (white circle, OK) if the average backlight brightness ABB in the average input video brightness AIVB for the frame under judgment is within the range between the upper and lower thresholds.

[0060] Figure 9 is a flowchart showing an example of the process by which the processor 400 in Figure 3 determines an abnormality in the brightness control unit 251. In other words, Figure 9 shows an example of an image display control method by the processor 400 and an image display control program executed by the processor 400. The flow shown in Figure 9 starts, for example, when the image display system 1 is started or the display controller 40 is started. Note that the processing from step S10 to step S70 is performed frame by frame.

[0061] First, in step S10, the processor 400 causes the image input unit 210 to acquire frame image data. Next, in step S20, the processor 400 causes the input color statistics acquisition unit 240 to acquire the average input video luminance AIVB of the input image data VIN.

[0062] Next, in step S30, the processor 400 determines the upper and lower thresholds of the average backlight brightness ABB based on the average input video brightness AIVB acquired in step S20. After step S10, in step S40, the processor 400 causes the output brightness statistics acquisition unit 260 to acquire the average backlight brightness ABB.

[0063] After steps S30 and S40, in step S60, the processor 400 determines whether the average backlight brightness ABB obtained in step S40 falls within the range of the upper and lower threshold values ​​determined in step S30. If the average backlight brightness ABB falls within the range of the upper and lower threshold values, the processor 400 determines that the brightness control unit 251 is normal and returns to step S10. If the average backlight brightness ABB does not fall within the range of the upper and lower threshold values, the processor 400 determines that the brightness control unit 251 is abnormal and proceeds to step S70.

[0064] In step S70, the processor 400 determines whether the content of the image to be displayed on the display 50 has been switched. If the content has been switched, the processor 400 determines that the content switch has caused an increase in the deviation amount of one or both of the average input video brightness AIVB and the average backlight brightness ABB, and that an abnormality has been detected in the brightness control unit 251.

[0065] Then, the processor 400 returns to step S10. That is, if the image content is switched, the processor 400 also suppresses the abnormality detection process of the brightness control unit 251 even if the average backlight brightness ABB is not within the range of the upper and lower thresholds. If the content is not switched, the processor 400 determines that an abnormality has occurred in the brightness control unit 251 and moves the process to step S80.

[0066] In step S80, the processor 400 performs the processing required when an abnormality is detected in the brightness control unit 251, and then terminates the process shown in Figure 9. An example of step S80 is shown in Figure 10.

[0067] If the processor 400 determines that content switching has occurred in step S70, it may, for at least one frame, skip the abnormality determination in step S60 and return to step S10, assuming that the brightness control unit 251 is functioning normally.

[0068] Furthermore, the processor 400 may suppress the detection process for detecting an abnormality in the brightness control unit 251 in step S60 for at least one frame period when the image display system 1 or the display controller 40 is started up. The processor 400 may then return to step S10 without performing the determination in step S60, assuming that the brightness control unit 251 is normal. This makes it possible to prevent the false detection of an abnormality in the brightness control unit 251 due to image distortion during content switching or when the device is started up.

[0069] Figure 10 is a flowchart showing an example of the processing in step S80 of Figure 9. First, in step S81, the processor 400 stops the pixel value correction operation by the pixel compensation unit 252. Then, the processor 400 bypasses the pixel compensation unit 252 and outputs the input image data VIN as output image data VOUT to the display 50. This prevents the RGB correction unit 254 from generating image data VC using an incorrect luminance distribution when the luminance information LINF is not normal due to a malfunction in the luminance control unit 251 and the luminance distribution calculation unit 253 cannot generate a normal luminance distribution.

[0070] Next, in step S82, the processor 400 stops dimming by the local dimming unit 250 and lights up all the LED light sources of the backlight 60, setting the backlight 60 to a preset brightness (for example, maximum brightness). In other words, the processor 400 lights up all the LED light sources at a predetermined brightness regardless of the operation of the brightness control unit 251. This makes it possible to display an image on the display 50 without reducing the brightness if the abnormality of the brightness control unit 251 is due to a decrease in brightness.

[0071] Next, in step S83, the processor 400 determines whether or not the display of an icon indicating an abnormality in the brightness control unit 251 is permitted. If the display of the icon indicating an abnormality is permitted, the processor 400 proceeds to step S84. If the display of the icon indicating an abnormality is not permitted, the processor 400 terminates the process shown in Figure 10.

[0072] In step S84, the processor 400 displays an icon indicating an error on the display 50 and terminates the process shown in Figure 10. In step S84, the processor 400 may directly control the display 50 and use the OSD (On Screen Display) function of the display 50 to display an icon indicating an error. Alternatively, the processor 400 may input image data indicating an icon to the image input unit 210, or overwrite the area of ​​the memory 220 that holds image data with icon data to display an icon indicating an error on the display 50.

[0073] In this embodiment, based on the input image data VIN input to the pixel compensation unit 252 and the brightness information LINF output from the brightness control unit 251, it is possible to detect abnormalities in the brightness control unit 251 that could not be detected in the conventional method.

[0074] The processor 400 determines upper and lower threshold values ​​for the average backlight brightness ABB used to determine abnormalities in the brightness control unit 251, based on the average input video brightness AIVB of the input image data VIN input to the local dimming unit 250. This allows the upper and lower threshold values ​​for detecting abnormalities in the brightness control unit 251 to be appropriately set according to the characteristics of the image represented by the input image data VIN for each frame. As a result, the accuracy of detecting abnormalities in the brightness control unit 251 can be improved.

[0075] The processor 400 refrains from detecting abnormalities in the brightness control unit 251 for at least one frame period when switching content or starting up the display controller 40, etc. This prevents the false detection of abnormalities in the brightness control unit 251 due to image distortion during content switching or startup.

[0076] When the processor 400 detects an abnormality in the brightness control unit 251, it stops the pixel value correction operation by the pixel compensation unit 252. This prevents the RGB correction unit 254 from generating image data VC using an incorrect brightness distribution when the brightness information LINF is not normal due to an abnormality in the brightness control unit 251 and the brightness distribution calculation unit 253 cannot generate a normal brightness distribution.

[0077] When an abnormality is detected in the brightness control unit 251, all LED light sources of the backlight 60 are turned on. This allows the image to be displayed on the display 50 without reducing brightness if the abnormality in the brightness control unit 251 is due to a decrease in brightness. In addition, when an abnormality is detected in the brightness control unit 251, an icon indicating the abnormality is displayed on the display 50 to notify the user of the abnormality in the brightness control unit 251. In practice, the icon indicating the abnormality is either a graphic and / or text that allows the user to recognize the abnormality in the display controller 40.

[0078] Furthermore, even if a malfunction occurs in the brightness control unit 251, preventing normal local dimming and resulting in low contrast of the image displayed on the display device 70, the malfunction in the brightness control unit 251 can be detected, and all LED light sources of the backlight 60 can be illuminated. This allows for higher contrast of the image displayed on the display device 70, thereby meeting the ASIL requirements.

[0079] (Second embodiment) Figure 11 is a block diagram showing an example of a display controller in a second embodiment. The same reference numerals are used for elements similar to those in Figure 2, and detailed descriptions are omitted. The display controller 40A shown in Figure 11 is installed, for example, in place of the display controller 40 in the image display system 1 of Figure 1.

[0080] The display controller 40A has a display engine 200A instead of the display engine 200 in Figure 2. The display engine 200A has the same configuration as the display engine 200 in Figure 2, except that it has an output color statistics acquisition unit 290 added to it.

[0081] The output color statistics acquisition unit 290 sequentially acquires the average output video brightness AOVB, which is the average of the pixel values ​​for one screen (one frame) included in the output image data VOUT output from the local dimming unit 250 to the image output unit 270. For example, the output color statistics acquisition unit 290 acquires the average output video brightness AOVB by calculation.

[0082] In this embodiment, the average input video brightness AIVB is an example of the first statistical data. The input color statistics acquisition unit 240 is an example of the first statistical acquisition unit. The average output video brightness AOVB is an example of the second statistical data. The output color statistics acquisition unit 290 is an example of the second statistical acquisition unit. The average backlight brightness ABB is an example of the third statistical data. The output brightness statistics acquisition unit 260 is an example of the third statistical acquisition unit.

[0083] The output color statistics acquisition unit 290 outputs the acquired average output video luminance AOVB to the processor 400 via the register interface 280 and the bus 500. The output color statistics acquisition unit 290 may also have a storage unit such as a buffer that holds the average output video luminance AOVB. In this case, the average output video luminance AOVB held in the storage unit may be read by the processor 400.

[0084] Figure 12 is a block diagram showing an example of an input color statistics acquisition unit 240, an output luminance statistics acquisition unit 260, and an output color statistics acquisition unit 290 connected to the local dimming unit 250 in Figure 11. In Figure 12, the register interface 280 and bus 500 shown in Figure 2 are omitted. Except for the addition of the output color statistics acquisition unit 290, the configuration of the local dimming unit 250, the input color statistics acquisition unit 240, and the output luminance statistics acquisition unit 260, and the connection relationships of each element are the same as in Figure 3.

[0085] The input color statistics acquisition unit 240 acquires the average input video luminance AIVB, which is statistical data of the input image data VIN that has been normalized to a value between 0 and 1. The output color statistics acquisition unit 290 acquires the average output video luminance AOVB, which is statistical data of the output image data VOUT that has been normalized to a value between 0 and 1. As a result, the processor 400 can perform the calculation of the upper and lower threshold limits described later without having to match the scales (number of bits, etc.) of the average input video luminance AIVB and the average output video luminance AOVB with each other.

[0086] Figure 13 shows an example of statistical data acquired by the input color statistics acquisition unit 240, output luminance statistics acquisition unit 260, and output color statistics acquisition unit 290 shown in Figure 12. The statistical data acquired by the input color statistics acquisition unit 240 and output luminance statistics acquisition unit 260 (average input video luminance AIVB and average backlight luminance ABB) are the same as those in Figure 7.

[0087] The output color statistics acquisition unit 290 calculates the maximum pixel value MAX (the maximum value among the pixel values ​​of red pixels, green pixels, and blue pixels) for each pixel of the output image data VOUT of each frame. Then, the output color statistics acquisition unit 290 calculates the average output video brightness AOVB by dividing the sum of the maximum values ​​MAX of all pixels by the total number of pixels.

[0088] Figure 14 shows an example of a threshold used to determine abnormalities in the brightness control unit 251 shown in Figure 12. The processor 400 determines whether there are any abnormalities in the brightness of the backlight 60 for each input image data VIN of one frame.

[0089] As explained in Figure 6, the RGB correction unit 254 corrects the brightness of the image by dividing the input image data VIN by the brightness (brightness distribution) of the backlight 60, thereby canceling out the brightness of the backlight 60, as shown in equation (6). By moving "backlight brightness" on the left side of equation (6) to the right side, equation (7) is obtained. Input image data VIN / Backlight brightness = Output image data VOUT ... (6) Input image data VIN = backlight brightness × output image data VOUT ... (7)

[0090] For example, in equation (7), "input image data VIN" can be approximated by "average input video luminance AIVB" acquired by the input color statistics acquisition unit 240. "Output image data VOUT" can be approximated by "average output video luminance AOVB" acquired by the output color statistics acquisition unit 290. "Backlight luminance" can be approximated by "average backlight luminance ABB" acquired by the output luminance statistics acquisition unit 260. Then, by replacing the terms in equation (7) with the approximated terms, equation (8) is obtained. That is, "average backlight luminance ABB × average output video luminance AOVB" has a value that corresponds to (approximates) "average input video luminance AIVB". Average input video brightness AIVB ≈ Average backlight brightness ABB × Average output video brightness AOVB ... (8)

[0091] In this embodiment, the processor 400 determines an abnormality in the brightness control unit 251 if the "average backlight brightness ABB × average output video brightness AOVB" obtained by the input color statistics acquisition unit 240 does not fall within a predetermined range. The predetermined range is indicated by an upper threshold and a lower threshold. "Average backlight brightness ABB × average output video brightness AOVB" is an example of output statistics data. The upper threshold is an example of an upper limit value, and the lower threshold is an example of a lower limit value.

[0092] Here, the luminance distribution of the backlight 60 is determined by considering the light diffusion into adjacent LED zones, as explained in Figure 5. The actual luminance of each LED zone of the backlight 60 is higher than the set luminance set for each LED light source because the diffusion from adjacent LED zones is added. In other words, the "average backlight luminance ABB" is smaller than the average value of the actual luminance of the LED zones of the backlight 60 because the diffusion from adjacent LED zones is not taken into account.

[0093] Therefore, the "average backlight brightness ABB × average output video brightness AOVB" in equation (8) does not exceed the product of the actual brightness of the backlight 60 and the output image data VOUT output from the pixel compensation unit 252. Consequently, the upper limit threshold of "average backlight brightness ABB × average output video brightness AOVB" in equation (8) does not exceed the average input video brightness AIVB. Therefore, the "average input video brightness AIVB" itself is set as the upper limit threshold (equation (9)). Upper threshold = Average input video brightness AIVB ... (9)

[0094] The lower threshold of "Average Backlight Brightness ABB × Average Output Video Brightness AOVB" needs to be set considering the blurring from adjacent LED zones, since "Average Backlight Brightness ABB" is smaller than the average actual brightness of the LED zones of the 60 backlights. For this reason, the lower threshold is set to the value obtained by multiplying "Average Input Video Brightness AIVB" by the brightness adjustment parameter β (0 < β < 1) (Equation (10)). The brightness adjustment parameter β is an example of a coefficient that can be multiplied by the average input video brightness AIVB. For example, the brightness adjustment parameter β is set to the ratio A / B of area A and area B shown in Figure 14. Area A is the integral value of brightness without considering light blurring when one LED light source is lit. Area B is the integral value of brightness of the brightness distribution shown in Figure 5, considering light blurring. Lower threshold = Average input video brightness AIVB × β ... (10)

[0095] The "average input video brightness AIVB" in equation (9) and the "average input video brightness AIVB × β" in equation (10) are examples of input statistical data. The processor 400 determines that the brightness control unit 251 is abnormal if the "average backlight brightness ABB × average output video brightness AOVB" of the frame to be judged does not fall within the range between the upper and lower thresholds shown in equations (9) and (10) (black circle, NG). The processor 400 determines that the brightness control unit 251 is normal if the "average backlight brightness ABB × average output video brightness AOVB" of the frame to be judged falls within the range between the upper and lower thresholds shown in equations (9) and (10) (white circle, OK).

[0096] Figure 15 is a flowchart showing an example of the process by which the processor 400 in Figure 12 determines an abnormality in the brightness control unit 251. In other words, Figure 15 shows an example of an image display control method by the processor 400 and an image display control program executed by the processor 400. Detailed explanations of processes similar to those in Figure 9 are omitted. The flow shown in Figure 15 starts, for example, when the image display system 1 is started or the display controller 40 is started. Note that the processes from step S10 to step S70 are performed frame by frame.

[0097] In the flow shown in Figure 15, steps S30A and S60A are performed instead of steps S30 and S60 in Figure 9, respectively. Also, step S50 is added between steps S30A and S60A. The other processes in Figure 15 are the same as those in Figure 9. The process in step S80 is the same as the process shown in Figure 10.

[0098] In step S30A, the processor 400 determines upper and lower threshold values ​​corresponding to the product of the average backlight brightness ABB and the average output video brightness AOVB, based on the average input video brightness AIVB acquired in step S20 and the previously determined brightness adjustment parameter β. Next, in step S50, the processor 400 causes the output color statistics acquisition unit 290 to acquire the average output video brightness AOVB of the output image data VOUT. Note that step S50 may be performed in parallel with steps S20 and S40.

[0099] After steps S40 and S50, in step S60A, the processor 400 calculates the product "ABB × AOVB" of the average backlight brightness ABB and the average output video brightness AOVB obtained in steps S40 and S50. Then, the processor 400 determines whether the calculated product "ABB × AOVB" falls within the range of the upper and lower threshold values ​​obtained in step S30A.

[0100] If the product "ABB × AOVB" falls within the range of the upper and lower thresholds, the processor 400 determines that the brightness control unit 251 is functioning correctly and returns to step S10. If the product "ABB × AOVB" does not fall within the range of the upper and lower thresholds, the processor 400 determines that the brightness control unit 251 is functioning incorrectly and proceeds to step S70. The processing in steps S70 and S80 is the same as the processing in steps S70 and S80 in Figure 9.

[0101] As described above, the same effects as those of the embodiments described can be obtained in this embodiment as well. For example, based on the input image data VIN input to the pixel compensation unit 252, the output image data VOUT output from the pixel compensation unit 252, and the brightness information LINF output from the brightness control unit 251, it is possible to detect an abnormality in the brightness control unit 251 that could not be detected in the conventional method.

[0102] Furthermore, in this embodiment, the processor 400 can determine the upper and lower thresholds without using the brightness adjustment parameter α. This prevents the upper or lower threshold from fluctuating depending on the brightness adjustment parameter α set by the user or the like. As a result, for example, it is possible to suppress the normal range of brightness of the backlight 60 set by the upper and lower thresholds from widening depending on the brightness adjustment parameter α, and to suppress a decrease in the abnormality detection accuracy of the brightness control unit 251.

[0103] In the first and second embodiments described above, an example was explained in which the upper and lower thresholds are determined in step S30 of Figure 9 or step S30A of Figure 15 based on the pixel values ​​of the input image data VIN input to the local dimming unit 250. However, if the image to be displayed on the display device 70 is predetermined, the upper and lower thresholds may be determined from pixel values ​​acquired in advance corresponding to the image to be displayed. In this case, the upper and lower thresholds corresponding to the image to be displayed are stored in the memory 300 and referenced by the processor 400. In this case, the process of determining the upper and lower thresholds in step S30 of Figure 9 and step S30A of Figure 15 is omitted.

[0104] Furthermore, in the first and second embodiments described above, an example was described in which an upper and lower threshold is determined based on the total pixel values ​​of the input image data VIN input to the local dimming unit 250, and an abnormality in the brightness control unit 251 is detected based on the determined upper and lower thresholds. However, instead of the total pixel values ​​included in the input image data VIN, the upper and lower thresholds may be determined based on the pixel values ​​of a smaller number of pixels obtained by downsampling some of the pixels included in the input image data VIN. In this case, the computational load on the input color statistics acquisition unit 240 and the output color statistics acquisition unit 290 can be reduced, and the computational load on the processor 400 for determining the upper and lower thresholds can be reduced. As a result, an increase in power consumption of the display controllers 40 and 40A can be suppressed.

[0105] Although the present invention has been described above based on various embodiments, the present invention is not limited to the requirements shown in the above embodiments. These points can be modified as long as they do not impair the spirit of the present invention, and can be appropriately determined according to their application. [Explanation of Symbols]

[0106] 1. Image display system 10 Head Units 20 Serializer 30 Deserializer 40, 40A Display Controller 50 displays 60 Backlight 200, 200A Display Engine 210 Image Input Section 220 memory 230 Warping Section 240 Input Color Statistics Acquisition Unit 250 Local dimming section 251 Brightness Control Unit 252 Pixel Compensation Section 253 Brightness Distribution Calculation Unit 254 RGB Correction Section 255 Saturation Processing Unit 260 Output Brightness Statistics Acquisition Unit 270 Image Output Unit 280 Register Interface 290 Output Color Statistics Acquisition Unit 300 memory 400 processors 500 bus ABB Average Backlight Brightness AIVB Average Input Video Brightness AOVB Average Output Video Brightness BLCNT Backlight Control Signal LINF Brightness Information LSF Brightness Distribution Function VC image data VIN input image data VOUT output image data

Claims

1. An image display control device having a local dimming function, A brightness control unit generates backlight control information used to control multiple light sources included in the backlight, based on first image information showing the input image. A pixel compensation unit that corrects the pixel values ​​included in the first image information based on the brightness of the plurality of light sources to generate second image information that shows the output image, A first statistical acquisition unit that acquires first statistical data of pixel values ​​included in the first image information, A second statistical acquisition unit acquires second statistical data of the brightness values ​​of each light source included in the backlight control information, If the second statistical data does not fall within the range between the upper and lower limits determined by the first statistical data, and no switching of image content has occurred, an abnormality detection unit detects an abnormality in the backlight control information generation process in the brightness control unit. An image display control device having

2. The first statistical data is the average value of the brightness of the input image, which is determined based on the pixel values ​​of the first image information. The second statistical data is the average value of the brightness values ​​of each light source included in the backlight control information. The image display control device according to claim 1.

3. The abnormality detection unit suppresses the abnormality detection process of the brightness control unit for at least one frame period when the content of the image to be displayed on the display unit is switched, as indicated by the second image information, or when the image display control device is started. The image display control device according to claim 1.

4. When the abnormality detection unit detects an abnormality in the brightness control unit, it outputs the first image information as the second image information, regardless of the operation of the pixel compensation unit, and lights up the multiple light sources, regardless of the operation of the brightness control unit. The image display control device according to claim 1.

5. An image display control device having a display engine that performs local dimming and a processor that controls the operation of the display engine, The aforementioned display engine is The system receives first image information indicating the image to be displayed on the display unit. The first image information is retained, Based on the first image information, backlight control information is generated for controlling multiple light sources included in the backlight. Based on the brightness of the multiple light sources, the pixel values ​​included in the first image information are corrected to generate second image information showing the output image. First statistical data of pixel values ​​included in the first image information is obtained, Second statistical data of the luminance values ​​of each light source included in the backlight control information is obtained. The second image information is output to the display unit, The processor detects an abnormality in the backlight control information generation process in the display engine if the second statistical data does not fall within the range between the upper and lower limits determined by the first statistical data, and no image content switching has occurred. Image display control device.

6. An image display control device having a local dimming function, A brightness control unit generates backlight control information used to control multiple light sources included in the backlight, based on first image information showing the input image. A pixel compensation unit that corrects the pixel values ​​included in the first image information based on the brightness of the plurality of light sources to generate second image information that shows the output image, A first statistical acquisition unit that acquires first statistical data of the brightness values ​​of each light source included in the backlight control information, If the first statistical data does not fall within the range between the upper and lower limits determined by the displayed image, and no switching of image content has occurred, an abnormality detection unit detects an abnormality in the backlight control information generation process in the brightness control unit. An image display control device having

7. The image display control device according to claim 1, Display unit and The backlight is positioned opposite the display unit, A head unit that generates an image and outputs the first image information indicating the generated image to the image display control device, An image display system having the following features.

8. An image display control method using an image display control device having a local dimming function, The brightness control unit of the image display control device generates backlight control information used to control multiple light sources included in the backlight, based on first image information indicating the input image. The pixel compensation unit of the image display control device corrects the pixel values ​​included in the first image information based on the brightness of the plurality of light sources to generate second image information that shows the output image. The first statistical acquisition unit of the image display control device acquires first statistical data of pixel values ​​included in the first image information. The second statistical acquisition unit of the image display control device acquires second statistical data of the luminance values ​​of each light source included in the backlight control information. The abnormality detection unit of the image display control device detects an abnormality in the backlight control information generation process in the brightness control unit if the second statistical data does not fall within the range between the upper and lower limits determined by the first statistical data, and no switching of image content has occurred. Image display control method.

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