Display-irregularity-correction base data generation method for display device, program, and production method for display device

Abstract

The purpose of the present invention is to correct light-emission wavelength shifts at sub-pixels to further eliminate irregularities at a display device. Provided is a display-irregularity-correction base data generation method whereby an image of light from a display device (110) that has a plurality of sub-pixels that emit primary colors is captured at an imaging apparatus (102) to generate correction base data that is to be used to correct display irregularities at the display device. The imaging apparatus includes an optical filter (106) at which transmittance varies monotonically relative to variation in wavelength near a prescribed wavelength for transmitted light, an imaging optical system (104), and a photoelectric conversion element and converts light that has entered the photoelectric conversion element to an electrical output signal. The method involves allowing light from each of the sub-pixels of a specific primary color to pass through the optical filter to obtain respective first output signal values, identifying a light-emission wavelength shift from a prescribed wavelength for the light-emission wavelength of each of the sub-pixels from the corresponding first output signal value, and generating the correction base data that is to be used to correct display irregularities at the display device on the basis of the light-emission wavelength shifts.

Description

Method for Generating Display Unevenness Correction Base Data for Display Device, Program, and Method for Producing Display Device

[0001] The disclosed technology relates to a method for generating display unevenness correction base data, a program, and a method for manufacturing a display device.

[0002] A display device emits colors from a plurality of sub-pixels. Since the light emission modes of each of the plurality of sub-pixels may be different, an image displayed on the display device may not be able to faithfully reproduce an input image signal input to the display device.

[0003] In a high-resolution display panel, there is a problem that the display brightness varies within the screen of the display and unevenness is displayed. In order to eliminate such unevenness based on the variation in brightness, for example, by using a driver circuit with a de-unevenness function, correction may be applied to the image signal to perform de-unevenness (unevenness correction).

[0004] Conventionally, an image quality adjustment device for suppressing display unevenness of a display using a liquid crystal panel is known. That is, an image correction data generation system including signal generation means for supplying a signal for outputting an image to a display panel, imaging means for photographing an output image displayed on the display panel, and control means connected to the signal generation means and the imaging means is known.

[0005] In the above conventional system, the control means includes instruction means for outputting an instruction for supplying a signal value common to the entire surface of the display panel to the signal generation means, image acquisition means for acquiring output image data from the imaging means, and band-pass filter means for calculating band-pass data obtained by removing high-frequency components and low-frequency components from the output image data by performing band-pass filtering for separating only intermediate frequency components from the output image data, and correction data generation means for outputting an image correction table corresponding to the band-pass data (see, for example, Patent Document 1).

[0006] Japanese Unexamined Patent Application Publication No. 2013-250570

[0007] The disclosed technology aims to further eliminate unevenness in display devices compared to conventional technologies by providing a technology that corrects unevenness caused by shifts in emission color due to subpixel emission wavelength shifts.

[0008] The present invention provides a method for generating display unevenness correction base data used when correcting display unevenness in a display device, comprising: an optical filter whose transmittance changes monotonically with respect to changes in wavelengths near a specific wavelength of transmitted light; an imaging optical system; and a photoelectric conversion element, wherein an imaging device is prepared that converts light that enters the photoelectric conversion element into an electrical output signal, and the imaging device captures light from a display device having a plurality of subpixels that emit primary colors, and the method for generating display unevenness correction base data used when correcting display unevenness in the display device, comprising: obtaining a first value of the output signal by transmitting light from each of the plurality of subpixels of a specific primary color through the optical filter; identifying the emission wavelength shift of each of the plurality of subpixels from a predetermined wavelength from the corresponding first value of the output signal; and generating correction base data used when correcting display unevenness in the display device based on the emission wavelength shift. In addition, the present invention provides a method for producing a display device that corrects display unevenness based on correction base data used when correcting display unevenness of a display device obtained by imaging the light from a display device having a plurality of subpixels that emit primary colors with the imaging device, wherein the imaging device includes an optical filter whose transmittance changes monotonically with respect to changes in wavelengths near a specific wavelength of transmitted light, an imaging optical system, and a photoelectric conversion element, and an imaging device is prepared to convert light that enters the photoelectric conversion element into an electrical output signal, the method for producing a display device that corrects display unevenness of a display device, wherein the imaging device captures light from the display device having a plurality of subpixels that emit primary colors, and the method comprises: obtaining a first value of the output signal by transmitting light from each of the plurality of subpixels of a specific primary color through the optical filter; identifying the emission wavelength shift of each of the plurality of subpixels from a predetermined wavelength from the corresponding first value of the output signal; generating correction base data used when correcting display unevenness of the display device based on the emission wavelength shift; and storing the correction base data in the storage unit of the display device.

[0009] According to the disclosed technology, by providing a technique to correct unevenness caused by the shift in emission color due to the emission wavelength shift of subpixels, it is possible to further eliminate unevenness in display devices compared to conventional technologies.

[0010] Figure 1 is a diagram showing an example of the hardware configuration of an embodiment. Figure 2 is a diagram showing a part of a display including an light-emitting element. Figure 3 is a flowchart showing the processing of an embodiment. Figure 4 is a flowchart illustrating one embodiment of emission wavelength shift. Figure 5 is a flowchart illustrating another embodiment of emission wavelength shift. Figures 6A and 6B are flowcharts showing the process of treating multiple subpixels as a single unit and generating correction base data for emission wavelength shift. Figure 7 is a graph showing the emission wavelength shift and light intensity of multiple blue light-emitting elements with different emission characteristics. Figure 8 is a graph showing the characteristics of a long-pass filter. Figure 9 is a graph showing the relationship between the long-pass filter and the emission wavelength shift of a blue light-emitting element. Figure 10 is a graph showing the relationship between the peak wavelength of a light-emitting element and the Ratio value. Figure 11 is a graph showing the transmission characteristics of a filter with three cut-on or cut-off wavelengths. Figure 12 is a diagram showing an example where a collection of four pixels of light-emitting elements is treated as a single processing target. Figure 13 is a diagram showing the relationship between the emission wavelength shift of a blue light-emitting element and the change in coordinates in the CIE 1931 color space diagram. Figure 14 is an enlarged view of Figure 13. Figure 15 is a diagram illustrating the processing of an embodiment. Figure 16 is a diagram showing details of Figure 15. Figure 17 is a graph showing the change in color gamut when the emission wavelengths of three blue subpixels included in the display are shifted. Figure 18A is a hardware configuration diagram of an embodiment. Figure 18B is a hardware configuration diagram of a display. Figure 19A is a diagram plotting the light intensity of three subpixels present in a single pixel in XYZ space. Figure 19B is a diagram plotting the light intensity of the three subpixels shown in Figure 19A and the light intensity of a target subpixel in XYZ space. Figure 20 is a diagram illustrating the detailed processing of the uniformity correction unit.

[0011] In recent years, displays composed of subpixels that emit primary colors, such as microLEDs, have attracted attention. Compared to liquid crystal displays and organic EL displays, these displays have superior characteristics such as high brightness, high resolution, fast response, low power consumption, and long lifespan.

[0012] However, these displays have a problem: the emission wavelength of individual light-emitting devices, or subpixels, shifts. When the emission wavelength of subpixels shifts, it can be seen by the human eye as image unevenness on the display. Such image unevenness can lead to a decrease in image quality and a shortened lifespan of the entire display device.

[0013] Figure 17 is a graph showing the change in color gamut when the emission wavelengths of the three blue subpixels in the display are shifted. For simplicity, we will assume that the emission wavelengths of the green and red subpixels are not shifted.

[0014] Figure 17 shows the human-perceived color gamut 1300 in the xy coordinate space of the CIE 1931 color space diagram. For the sake of simplicity, the following explanation assumes that there is no wavelength shift in the red subpixel R and green subpixel G of the display, but that there is a wavelength shift in the blue subpixel B. The case where there is further wavelength shift in the red subpixel R and green subpixel G will be discussed later. The ideal color gamut of a certain display is shown as the color gamut RGB0.

[0015] In Figure 17, one subpixel undergoes an emission wavelength shift, forming the RGB1 color gamut. Another subpixel also undergoes an emission wavelength shift, forming the RGB2 color gamut. Since these RGB1 and RGB2 color gamuts have different color gamuts than the RGB0 color gamut, they can display different colors. This wavelength shift of the blue subpixel B causes color unevenness in the display, which is also perceived by the human eye.

[0016] Therefore, in the embodiments shown below, the RGB color gamut is a common color gamut that can represent colors in any of the RGB0, RGB1, and RGB2 color gamuts. t This paper discloses a method to reduce display inconsistencies by setting a common color gamut for each pixel of the display. Note: The color gamut is RGB. t This can be defined by specifying the color gamut that can be represented by any subpixel, taking into account the characteristics of all subpixels. Note that considering the characteristics of all subpixels, the color gamut is RGB. t If the color gamut becomes small, consider, for example, 90% of all subpixels to determine the RGB color gamut. t You may define it as the RGB color gamut, considering all subpixels. t Alternatively, one could compare the current color gamut to an ideal color gamut and define a color gamut by interpolating the two. The degree of interpolation can be predetermined using empirical rules.

[0017] It should be noted that Figure 17 is exaggerated for the sake of clarity and that it only illustrates the wavelength shift of the blue subpixel B. The actual change in color gamut due to the wavelength shift of subpixels is generally smaller. Figure 1 shows an example of the hardware configuration of the embodiment.

[0018] A display 110 having a display screen 112 is installed. A camera 102 images the display 110 through a lens 104. A computer (Figure 18A) processes the imaging signal obtained from a photoelectric conversion element (image sensor) built into the camera 102. The display screen 112 is equipped with light-emitting elements such as micro-LEDs (Figure 2). The display 110 may also include a driver circuit (Figures 18B, 1850) that processes the image signal and provides it to the micro-LEDs. The driver circuit may include a computer and / or semiconductor circuit that operates with hardware logic and / or software. An optical filter 106 is used to detect the emission wavelength shift of subpixels. The characteristics of this optical filter 106 will be described later.

[0019] Furthermore, the optical filter 106 may be installed in a way that allows it to be physically moved, so that the camera 102 can also capture images of light with the optical filter 106 removed. The optical filter 106 may be installed on the entire surface of the lens 104, or it may be installed at any position in the optical system including the lens 104. Figure 2 shows a part of the display 110 including the light-emitting element 200.

[0020] The light-emitting element 200 has a plurality of pixels 210. Each pixel 210 includes a red subpixel R212, a green subpixel G214, and a blue subpixel B216. In this specification, the red, green, and blue colors emitted by these subpixels are referred to as primary colors. It should be noted that while the term primary colors is generally used to refer to the colors red, blue, and green, primary colors do not define specific wavelengths, and the wavelengths of primary colors may differ depending on the display.

[0021] Figure 2 shows an example with three subpixels, but the number of colors is not limited to three, and there may be two, four, or other subpixels instead of necessarily three. Figure 3 is a flowchart of the process in the embodiment. Each step will be described below.

[0022] [Step S302] Without using the optical filter 106, correction base data for brightness correction may be generated to correct display unevenness in the display device so that the brightness of multiple subpixels approaches a predetermined value. If the characteristics of multiple subpixels are substantially the same, it can be estimated that the brightness of each subpixel will be constant without brightness correction. In this case, step S302 may be omitted.

[0023] [Step S304] With respect to a specific primary color subpixel, the light from each of the multiple subpixels is transmitted through the optical filter 106 to obtain a first value of the output signal.

[0024] From among the multiple subpixels present across the entire display, a subpixel corresponding to one color is made to emit light. The output signal of the photodetector corresponding to each subpixel is acquired sequentially.

[0025] [Step S306] For each of the multiple subpixels, the emission wavelength shift of each of the multiple subpixels from a predetermined wavelength is determined from the first value of the output signal from the photoelectric conversion element. The principle of measuring the emission wavelength shift will be described later.

[0026] [Step S308] Based on the emission wavelength shift, correction base data is generated which is used to correct display unevenness in the display device. The method for correcting display unevenness based on the emission wavelength shift and the method for using the correction base data will be described later. The above series of steps may be performed for different specified brightness levels. Brightness can be specified by specifying a predetermined display gradation. Figure 4 is a flowchart illustrating one embodiment of the emission wavelength shift. Each step will be described below. [Step S400] This step is the step to start a more detailed process of step S306. [Step S402] A second value of the output signal for light transmitted through the imaging optical system is obtained without using an optical filter. [Step S404] For each of the plurality of subpixels, the ratio (Ratio) of the first value to the second value is calculated.

[0027] This ratio allows us to estimate the degree of emission wavelength shift for each of multiple subpixels. Emission wavelength shift refers to the degree to which the emission wavelength is distorted compared to a predetermined wavelength. From this ratio, for example, the position of the emission color of a subpixel in the xy coordinate space of a CIE 1931 color space diagram can be determined. The details of this will be described later. By processing this ratio, the emission wavelength shift can be estimated without directly measuring it, thereby simplifying and speeding up the processing.

[0028] Furthermore, instead of using the value of the subpixel with the largest emission wavelength shift, a value less than the emission wavelength shift amount, for example, 80% of that emission wavelength shift value, may be adopted. In this way, unevenness caused by emission wavelength shift can be eliminated without drastically degrading the display quality of the image display. The extent to which a value less than the maximum emission wavelength shift is adopted should be determined according to the degree of human sensitivity to emission wavelength shift, the characteristics of the display and the light-emitting device mounted on the display, the color whose emission wavelength is shifted, etc. [Step S406] The process returns to step S306. Figure 5 is a flowchart illustrating another embodiment of emission wavelength shift. Each step is described below.

[0029] [Step S500] This step is to start the more detailed processing of step S306.

[0030] [Step S502] For each of the primary colors R, G, and B, the emission wavelength shift is determined for multiple subpixels used to emit light of the same primary color.

[0031] Other methods for determining the wavelength shift may be used besides the process shown in Figure 4. That is, the wavelength may be measured directly, or the x and y coordinates in the color space may be determined. [Step S504] The process returns to step S306.

[0032] Figures 6A and 6B are flowcharts showing the process of generating correction base data for emission wavelength shift by treating multiple subpixels as a single unit. Each step is described below. The process in Figure 6A is described below. [Step S600] This step is the step to start a more detailed process of step S306. [Step S602] The emission wavelength shift is identified with respect to the set of subpixels in the subregion where multiple subpixels are arranged.

[0033] Instead of applying the process to each individual pixel, the emission wavelength shift may be determined for a set of subpixels contained within a set of pixels (e.g., 4x4 pixels).

[0034] This process allows us to obtain the average emission wavelength shift of multiple subpixels. In addition, this simplifies and / or speeds up the overall processing. The method for handling multiple subpixels may involve handling a spatial set of multiple subpixels, or it may involve treating the brightness of each subpixel output in time series from the image sensor that images each subpixel as a set in a predetermined time domain. [Step S604] Return to step S306. The processing of Figure 6B is described below. [Step S610] This step starts the more detailed processing of step S308. [Step S612] Correction base data is generated with respect to the set of subpixels to correct the display unevenness of the display device. [Step S614] Return to step S308.

[0035] However, when multiple subpixels are treated as a single unit in this way, it may not be possible to accurately correct the emission wavelength shift of the subpixels. Nevertheless, it is desirable to determine how many pixels (subpixels) to target, taking into account the sensitivity of the human eye to emission wavelength shifts, depending on the characteristics of the display and the light-emitting device mounted on the display, the shifted color, etc. In addition, the display device can be produced by storing the correction base data obtained in the above embodiment in the memory of the display device. Figure 7 is a graph showing the emission wavelength shift and light intensity of multiple blue light-emitting elements with different emission characteristics.

[0036] Spectrum 704 is the spectrum at the standard value (peak wavelength = 460 nm). Spectra 702 and Spectrum 706 on the left and right are the spectra when the peak wavelength is shifted by ±10 nm. Figure 13 shows the relationship between the emission wavelength shift (or ratio value) of the blue light-emitting element and the change in coordinates in the CIE 1931 color space diagram. Figure 14 is an enlarged view of Figure 13. In Figures 13 and 14, the human-perceived color gamut 1300 is shown.

[0037] As shown in Figure 7, when the peak wavelength of light emission from a blue light-emitting element changes, the chromaticity (for example, the coordinate values ​​in the x and y coordinate space of the CIE 1931 color space diagram) also changes. In the CIE 1931 color space diagram, as the peak wavelength increases, the chromaticity shifts to the upper left, and as the peak wavelength decreases, the chromaticity shifts to the lower right.

[0038] Figure 14 shows the details of the change in chromaticity with respect to the peak wavelength. These figures show the variation in chromaticity in the CIE 1931 color space when the peak wavelength changes within the range of 460 ± 10 nm. Since this variation is approximately constant in the design of the light-emitting element, the chromaticity curve 1302 in Figure 14 can be determined by measuring the relationship between the peak wavelength and the chromaticity in the CIE 1931 color space for multiple light-emitting elements manufactured with the same design in advance.

[0039] In other words, chromaticity curve 1302 is a curve that shows the change in chromaticity when the peak wavelength of a certain blue light-emitting element changes within the range of 460 ± 10 nm. It should be noted that different chromaticity curves may be obtained for light-emitting elements with different designs.

[0040] In Figure 14, point ○1414 indicates the coordinate of the chromaticity at a peak wavelength of 460 + 10 nm. Point *1416 indicates the coordinate of the chromaticity at a peak wavelength of 460. Point ×1418 indicates the coordinate of the chromaticity at a peak wavelength of 460 - 10 nm. Also, ・ indicates the coordinate of the chromaticity at various peak wavelengths within the range of 460 ± 10 nm. Figure 8 is a graph showing the characteristics of a long-pass filter.

[0041] An ideal long-pass filter allows light longer than a certain wavelength to pass through and blocks light shorter than a certain wavelength. Figure 8 shows an example of a filter used. This figure shows the transmittance against wavelength. This long-pass filter allows light longer than 460 nm to pass through and blocks almost all light shorter than 460 nm (the transition width is about 20 nm). It is desirable that the cut-on wavelength be designed to roughly match the peak wavelength of a standard blue light-emitting element. Figure 9 is a graph showing the relationship between the long-pass filter and the emission wavelength shift of the blue light-emitting element.

[0042] It is desirable to design the characteristic curve of the long-pass filter such that the center of the steep cut-on increase curve of the long-pass filter 800 corresponds to the peak frequency of a standard blue light-emitting element of 460 nm. The amount of light that passes through this long-pass filter and reaches the camera's photodetector will change according to the variation in the peak frequency of the blue light-emitting element. An example of measuring the variation in the peak frequency of a blue light-emitting element is shown below.

[0043] Using this filter, the blue light-emitting element is photographed using camera 102 under two different conditions: without the filter and with the filter. Let L1 be the brightness when photographed without the filter, and L2 be the brightness when photographed with the filter. Calculate the ratio (Ratio) of L1 to L2. The ratio (Ratio) is as follows: Ratio = L2 / L1. The value of Ratio changes depending on the peak wavelength. The longer the peak wavelength, the larger the Ratio, and the shorter the peak wavelength, the smaller the Ratio. Figure 10 is a graph showing the relationship between the peak wavelength of the light-emitting element and the Ratio value of 1000.

[0044] The graph shows the range of 460 ± 40 nm to make the changes easier to understand. In reality, it is rare for the peak wavelength to vary this much; typically, the variation is around 460 ± 10 nm. By sampling multiple blue light-emitting elements and creating this graph in advance, the peak wavelength can be determined from a Ratio value of 1000.

[0045] In addition, by sampling multiple blue light-emitting elements and creating the chromaticity curve 1302 shown in Figure 14 in advance, the chromaticity can be determined from a Ratio value of 1000.

[0046] Furthermore, assuming that the brightness of the light-emitting element is approximately constant when a constant driving power is applied, the brightness of the blue light-emitting element without a filter can be assumed to be constant. Based on this assumption, the measurement without a filter may be omitted. In this case, the peak wavelength and / or chromaticity can be directly determined from the output of the photoelectric conversion element in the camera 102 when a filter is present, rather than from the Ratio value of 1000.

[0047] The above explanation used the peak wavelength of a blue light-emitting element as an example. Needless to say, this explanation can also be applied to the peak wavelength shift of light-emitting elements of other colors (red, green). Furthermore, applying this explanation to light-emitting elements of other colors (red, green) should be easily done by those skilled in the art, based on the above explanation. Figure 11 is a graph showing the transmission characteristics of a filter 1100 with three cut-on or cut-off wavelengths.

[0048] This filter 1100 has steep slopes 1102, 1104, and 1106. By designing the filter so that the wavelength of the central part of each steep slope matches the ideal peak wavelengths of blue, green, and red, the peak wavelengths and / or chromaticity of blue, green, and red light-emitting elements can be estimated with a single filter. Needless to say, the estimation method is the same as the one used for the blue light-emitting element. Examples of ideal peak wavelengths for blue B, green G, and red R light-emitting elements are as follows: B = 460 nm, G = 530 nm, R = 620 nm. Figure 12 shows an example where a collection of light-emitting elements 1202, which consists of 16 pixels 210 of the light-emitting element 200, is treated as a single processing target.

[0049] By processing the set of light-emitting elements 1202, the average emission wavelength shift of multiple subpixels can be obtained. Furthermore, this simplifies and / or speeds up the overall processing.

[0050] The number of light-emitting elements included in a set of multiple light-emitting elements is not limited to 16. It should be noted that when dealing with a set of multiple light-emitting elements, it is conceivable that the removal of unevenness due to emission wavelength shift may not be sufficient. Considering the sensitivity of the human eye to emission wavelength shift, it is desirable to determine the number of pixels (subpixels) to target, the characteristics of the display and the light-emitting devices mounted on the display, the shifted color, etc., when deciding on the number of light-emitting elements included in the set. Figure 15 is a diagram illustrating the processing of the embodiment. Figure 16 is a diagram showing details of Figure 15. The details of the processing of this embodiment are described below.

[0051] By measuring the peak wavelength of a blue subpixel, the brightness of the red and green subpixels present in the pixel containing that subpixel is adjusted to appropriately blend red and green with blue, thereby adjusting the chromaticity of the blue apex in the color gamut.

[0052] The purpose of adjusting the chromaticity of each vertex in the color gamut is to eliminate variations in the chromaticity of light-emitting elements and maintain a consistent color gamut at each pixel. One method of adjusting chromaticity to unify the color gamut is, for example, to change the brightness of the red and green light-emitting elements in addition to the blue ones, thereby bringing the chromaticity of blue closer to the chromaticity of the blue vertex in the unified color gamut. The adjustment of the chromaticity of the blue vertex in the unified color gamut has already been explained using Figure 17.

[0053] Figures 15 and 16 show a method for adjusting the chromaticity of the blue apex in a unified color gamut by changing the brightness of red and green light-emitting elements. Figures 15 and 16 show the relationship between the x and y coordinates of the red and green light-emitting elements and the x and y coordinates of the blue light-emitting element.

[0054] The x and y coordinates of the blue light-emitting element are determined from its peak wavelength. The x and y coordinates of the red and green light-emitting elements can also be determined in advance from their peak wavelengths, similar to the case of the blue light-emitting element.

[0055] Assume that the chromaticity of the emitted color of the blue light-emitting element of a certain display 110 varies between chromaticity 1512 and chromaticity 1514. For example, if the emitted colors of red and green light-emitting elements are mixed with the emitted color of a blue light-emitting element with chromaticity 1514, the chromaticity shifts to chromaticity 1530 inside the triangle. Mix the emitted colors of red and green light-emitting elements so that the blue vertex of the triangle of the color gamut has x and y coordinates of chromaticity 1530. For simplicity, assume that there is no change in the chromaticity of the red and green light-emitting elements.

[0056] Within the triangle of a unified color gamut are the chromaticities when red, green, and blue light-emitting elements are mixed in various proportions. The chromaticity 1530 at the blue vertex of the unified color gamut is preferably within the chromaticity of all the color gamut triangles formed at each pixel of the display 110 in order to eliminate variations in chromaticity due to variations in the peak wavelength of the blue light-emitting elements.

[0057] Then, in order to obtain the target chromaticity within a unified color gamut, the brightness of the blue, red, and green light-emitting elements is calculated for each pixel. The calculation method utilizes the fact that the chromaticity of any point within the triangle represented by the color gamut can be expressed as the centroid of the chromaticity of the red, green, and blue light-emitting elements.

[0058] The centroid is the equilibrium point when mass is placed at the vertices of a triangle. Mass can be replaced with luminance. The position of the centroid can be expressed as the ratio of the distances from the vertices of the triangle. For example, the midpoint of the chromaticity of red and blue light-emitting elements has a centroid at a position where red:blue = 1:1. A point where the ratio of the luminances of the chromaticity of red and blue light-emitting elements is 4:1 also has a centroid at a position where red:blue = 4:1. Similarly, the position of the centroid of the chromaticity of red, green, and blue light-emitting elements can be expressed as the ratio of the luminances of red:green:blue. For example, when the centroid of the chromaticity of red, green, and blue light-emitting elements is red:green:blue = 1:2:3, the chromaticity is the sum of the chromaticity of the red light-emitting element multiplied by 1 / 6 of its luminance, the chromaticity of the green light-emitting element multiplied by 2 / 6 of its luminance, and the chromaticity of the blue light-emitting element multiplied by 3 / 6 of its luminance.

[0059] In this way, the position of the centroid corresponding to the target chromaticity can be determined, and by changing the brightness of the red and green light-emitting elements according to the ratio, the chromaticity can be adjusted to obtain the target chromaticity.

[0060] In this way, after the target chromaticity has been determined, it is desirable to perform brightness correction again. That is, after adjusting the chromaticity, brightness correction is performed last. The purpose of brightness correction is to maintain a constant brightness without changing the chromaticity. Brightness correction can be performed by adjusting the brightness by equally changing the brightness of the red, green, and blue light-emitting elements.

[0061] To adjust the brightness, first calculate the sum of the brightness values ​​of the red, green, and blue light-emitting elements after adjusting the chromaticity. This sum corresponds to the brightness displayed on the camera's light-receiving element. Next, equally change the brightness values ​​of the red, green, and blue light-emitting elements to achieve a predetermined brightness. For example, if the predetermined brightness is twice the sum of the adjusted brightness values, then the brightness values ​​of the red, green, and blue light-emitting elements should each be doubled. In this way, brightness can be adjusted without changing the chromaticity.

[0062] To correct the brightness, for example, one can pre-measure the relationship between the drive current (or drive voltage) of the red, green, and blue light-emitting elements, their brightness, and the magnitude of the output signal output by the camera's photodetector.

[0063] The following example shows how to calculate the VR and VG mixtures of red and green emission colors for the blue subpixel's emission color so that each pixel forms a unified color gamut triangle. The luminance is the sum of the XYZ values ​​as defined by the CIE 1931 standard. For simplicity, the original blue luminance B before changing the blue luminance is assumed to be 1.

[0064] Let (Rx, Ry) be the xy coordinates of the chromaticity of the red subpixel in the CIE 1931 color space diagram, which were measured in advance, and (Gx, Gy) be the xy coordinates of the chromaticity of the green subpixel. Then, let (Bx, By) be the xy coordinates of the chromaticity of the blue subpixel. And, let (Tx, Ty) be the xy coordinates of the blue vertex of the unified color gamut triangle.

[0065] Step 1) Find the difference between point (Tx, Ty) and point (Bx, By) and set it to (Dx, Dy). The correction base data stored in the ROM 1818 of the display 110 for use when correcting display unevenness may include the characteristics of each subpixel, i.e., the coordinates of each subpixel (Rx, Ry), (Gx, Gy), (Bx, By) and the brightness of each subpixel. Dx = Tx - Rx Dy = Ty - Ry Step 2) Let the mixing amounts of red and green be VR and VG, and set up the following system of equations: Rx × VR + Gx × VG = Dx Ry × VR + Gy × VG = Dy Solve this for VR and VG. VR = (Gy×Dx-Gx×Dy) / (Rx×Gy-Gx×Ry) VG = (Rx×Dy-Ry×Dx) / (Rx×Gy-Gx×Ry) These give us the red and green mixture amounts VR and VG.

[0066] Furthermore, since mixing VR and VG changes the overall brightness, it is desirable to change the values ​​of VR, VG, and B to compensate for this change. The method of changing these values ​​should ideally be to maintain the distribution ratio of the red, green, and blue mixtures (VR, VG, B) while changing the ratio of VR, VG, and B so that 1 = B2 + VR2 + VG2 holds true. B2 = B / (B + VR + VG), VR2 = VR / (B + VR + VG), and VG2 = VG / (B + VR + VG) are calculated to result in B2 + VR2 + VG2 = 1.

[0067] For use in correcting display unevenness, the correction base data stored in the ROM 1818 of the display 110 may include the mixing amounts (VR, VG, VB) of each of the three vertices of the newly defined color gamut.

[0068] Furthermore, the characteristics of light-emitting elements such as micro-LEDs may differ depending on the grayscale at which they emit light. Therefore, the stored correction base data may be stored corresponding to the grayscale of the micro-LED. However, if correction base data is stored for all grayscales, the amount of data to be stored may become too large. In this case, correction base data corresponding to some grayscales may be stored, and the correction base data or actual correction data corresponding to the unstored grayscales may be obtained by interpolating the stored correction base data or calculated correction data.

[0069] Alternatively, the amount of correction base data stored in ROM 1818 can be reduced by compressing the correction base data. Various known data compression methods familiar to those skilled in the art can be used for compression.

[0070] By performing the above process, the color gamut of each pixel becomes consistent. To make each pixel emit the desired color, as explained earlier, the brightness of each subpixel is determined so that the position of the centroid, which is obtained from the brightness of each vertex of the color gamut, becomes the desired chromaticity.

[0071] The mixing ratios of red, green, and blue (VR, VG, VB) (i.e., the mixing ratio of red, green, and blue and the brightness correction value) can be stored in the ROM 1818 of the driver circuit 1850 of the display 110 as correction base data for correcting display unevenness, corresponding to each pixel. The ROM 1818 may also store correction base data corresponding to some of the grayscale levels. In this case, correction base data corresponding to grayscale levels that are not stored may be obtained by interpolating the stored correction base data. Alternatively, compressed correction base data may be stored in the ROM 1818. Note that the correction base data may also be stored in a location other than the display 110 (for example, a computer that provides image data to the display 110).

[0072] For the sake of simplicity, the above embodiment was described by taking the case where wavelength shift occurs in one sub-pixel among a plurality of sub-pixels as an example. The following embodiment will describe the case where wavelength shift occurs in a plurality of sub-pixels of a pixel. FIG. 18A is a hardware configuration diagram of the embodiment.

[0073] The hardware configuration of the embodiment includes a CPU 1801, a ROM 1802 in which the program and data of the present embodiment can be stored, a RAM 1803, a network interface 18018, an input interface 1806, a display interface 1807, an external memory interface 1808, and an output interface 1809. These hardware components are interconnected by a bus 1804.

[0074] The network interface 1805 is connected to a network 1815. The network 1815 includes a wired LAN, a wireless LAN, the Internet, a telephone network, and the like. A camera 102 or the like is connected to the input interface 1806. An output unit 1819 is connected to the output interface 1809. A display 110 is connected to the display interface 1807 via a signal line 1862. The display screen 112 may be realized by a plurality of display devices. A ROM 1818 storing correction base data is connected to the external memory interface 1808 via a signal line 1860. As will also be described in FIG. 18B, it is desirable for the ROM 1818 to be present in the display 110. An external video signal is input to the display 110 via a signal line 1864.

[0075] FIG. 18B is a hardware configuration diagram of the display 110. As shown in FIG. 18B, the display 110 receives an RGB value (R ii , G ii , B ii ) 1862 from the display interface 1807 shown in FIG. 18A or an external video signal (R ii , G ii , B ii ) 1864.

[0076] The received RGB values ​​(R ii , G ii , B ii ) 1862 or external video signal (R ii , G ii , B ii ) 1864 is input to the inverse gamma converter 1872. The inverse gamma converter 1872 converts the RGB values ​​(R ii , G ii , B ii ) 1862 or external video signal (R ii , Gi i , B ii ) 1864 is converted to linear RGB values ​​(R i , G i , B i Convert to ).

[0077] Note that the RGB values ​​(R ii , G ii , B ii The signal from 1862 is used when the camera 102 captures the display of the display 110, and the CPU 1801 calculates and generates correction base data A. After the correction base data A is stored in the ROM 1818 via the signal line 1860 from the external memory interface 1808, the display 110 may be separated from the computer in Figure 18A. The separated display 110 corrects the video signal 1864 and displays an image on the display screen 112 in which the unevenness is not visible (or the unevenness is difficult to see).

[0078] The uniformity correction unit 1874 corrects the linear RGB values ​​(R) that have been inversely gamma-converted so that uniformity is not visible on the display screen 112 (or so that uniformity is less visible). i , G i , B i ) is corrected to obtain the corrected linear RGB value (R o , G o , B o The uniformity correction unit 1874 uses multiple correction base data A read from ROM 1818. Correction base data A has multiple values. Details of how to create and use correction base data A will be described later.

[0079] The gamma conversion unit 1876 converts the corrected linear RGB value (R o , G o , B o ) is gamma-converted to output RGB values ​​(R o , G o , B o ) outputs the output RGB values ​​(R o , G o , B o Based on this, each subpixel of the display screen 112 emits light with an appropriate amount of light.

[0080] The specific processing of the inverse gamma conversion unit 1872 is as follows. Note that if the image resolution is m × n, then one screen of video signal contains m × n pixel information. In the following description, the m × n pixel information is usually transmitted as a stream signal in a compressed format. It should be noted that in this specification, we may take up and explain only one of these m × n pixel information. The processing of one pixel information can be similarly applied to the processing of other pixel information. Furthermore, the compression and decompression processing of RGB values ​​will be omitted. Also, although the video signal will be explained using gamma-corrected RGB values ​​as an example, it goes without saying that this embodiment can be similarly applied to image information formats other than RGB values ​​to those skilled in the art.

[0081] Input RGB values ​​(R) received from the image signal ii , G ii , B ii ) is usually gamma corrected, for example R ii By applying inverse gamma correction using the following formula (1), the linear RGB value (R i , G i , B i Convert to ).

[0082] Similarly, G i and B i The same inverse gamma correction process is applied to this as well.

[0083] The unevenness correction unit 1874 corrects the unevenness of the red signal R by performing a three-color mixing process as shown in equation (2) below. o Green light Go and green light B o You can obtain this.

[0084] Figure 19A is a plot of the light intensity of three subpixels present in a single pixel in XYZ space. The red subpixel R p The amount of light is (X rp , Y rp , Z rp It can be represented as ). Green subpixel G p The amount of light is (X gp , Y gp , Z gp ) can be represented as. Blue subpixel B p The amount of light is (X bp , Y bp , Z bp It can be expressed as ).

[0085] Figure 19B is a plot of the light intensity of the three subpixels shown in Figure 19A and the light intensity of the target subpixel in XYZ space.

[0086] The light intensity of a target subpixel is determined by identifying the largest volume tetrahedron among the tetrahedrons that exist in each closed space formed by the coordinates of the three subpixels of each pixel on the display screen in XYZ space and the zero points connected to each other. The light intensity of the three vertices of the identified tetrahedron, excluding the zero point, is then determined. By using the light intensity of these three identified target subpixels for all pixels, a uniform image can be displayed. The color of the blue target subpixel, for example, may be shifted by a certain amount to a darker blue. It is desirable that this shift be to a value that does not cause unevenness to be visible to the human eye. The same applies to the colors of the red and green target subpixels. By fine-tuning the color of the target subpixels in this way, the range of colors that can be represented by the three target subpixels can be increased while keeping the unevenness from being easily visible to the human eye.

[0087] Red target subpixel Rt The amount of light is (X rt , Y rt , Z rt This can be represented as ). Subpixel G of the green target t The amount of light is (X gt , Y gt , Z gt This can be represented as ). Subpixel B of the blue target. t The amount of light is (X bt , Y bt , Z bt ) can be expressed as follows. In this case, the relationship between the light intensity of each subpixel and the light intensity of the target subpixel is as follows: For red, Xrt = Xrp*Arr + Xgp*Arg + Xbp*Arb Yrt = Yrp*Arr + Ygp*Arg + Ybp*Arb Zrt = Zrp*Arr + Zgp*Arg + Zbp*Arb The same equations hold for green and blue, and when these are represented as a matrix, the following equation (3) holds.

[0088] The base data A, which is a transformation matrix that converts the light intensity of each subpixel to the light intensity of the target subpixel, can be obtained from equation (3) by performing the following calculation in equation (4). The base data A, consisting of nine constants obtained by solving equation (4), is pre-stored in ROM 1818, corresponding to all pixels, and by using equation (2) above, the linear RGB value of the light intensity based on any video signal 1864 (R i , G i , B i Given ), the linear RGB value (R) of the light intensity of the target subpixel is given. o , G o , B o ) can be calculated.

[0089] The gamma conversion unit 1876 performs the reverse processing of the inverse gamma conversion unit 1872, which has already been described. Since the specific conversion formulas used in the gamma conversion unit 1876 are the reverse of those used in the inverse gamma conversion unit 1872, they will be omitted.

[0090] FIG. 20 is a diagram for explaining the detailed processing of the unevenness correction unit 1874. The unevenness correction unit 1874 includes nine multipliers 22 and three adders 24. The unevenness correction unit 187 executes the above formula (2) to obtain the linear RGB values (R i , G i , B i ) of the light amount based on the video signal, and outputs the linear RGB values (R o , G o , B o ) of the light amount of the target sub-pixel.

[0091] The processing of the present embodiment described in the specification and drawings may be calculated by hardware logic or may be calculated by a computer based on a program. Alternatively, it is needless to say that the operation of the hardware logic and the operation of the computer by the program may cooperate to perform the calculation.

[0092] Among the above-described plurality of embodiments, a part of one embodiment may be applied to a part of another embodiment. Each flow of the illustrated flowchart can be reordered as long as there is no contradiction. Also, as long as there is no contradiction, one illustrated flow can be executed multiple times at different timings. Also, as long as there is no contradiction, multiple flows can be executed simultaneously. Also, not all steps are essential, and as long as there is no contradiction, some steps may not exist or may not be executed. Also, each step may be executed by an operating system or hardware. Also, the program can be distributed in a state stored in a non-transitory medium. Also, all of the program may be executed by hardware logic instead of sequential processing using a CPU or the like.

[0093] The program and method for realizing the above embodiment can be executed by a computer having the hardware configuration shown in FIG. 18A. That is, the program of the embodiment may be implemented as a method for causing a computer to execute. The program may be stored in the ROM 1802 or the RAM 1803 which is a non-temporary storage medium.

[0094] Each embodiment can be implemented as a hardware device with a program installed. In addition, each embodiment can be implemented as a production method for a display device with corrected display unevenness. Furthermore, this embodiment can be applied to a display device using microLEDs. In addition, this embodiment can be applied to various display devices using light-emitting elements, such as organic EL displays (OLED displays), where each subpixel emits light. Furthermore, this embodiment can be applied to a display device in which the emission wavelength shift varies from one light-emitting element to another.

[0095] In this specification, the intensity of light emitted by a light-emitting element is described using the term "luminance," but "luminance" can be replaced with "light intensity," "brightness," or "luminescence luminance." Furthermore, while an example of identifying the characteristics of a subpixel by specifying the shift in the peak wavelength of that subpixel using a filter has been described, it goes without saying that the characteristics of the pixel can also be identified by directly using the ratio of the filter transmission characteristics with and without the filter.

[0096] In the embodiments described above, a filter was used to identify the characteristics of a certain subpixel, but the disclosed techniques are not limited thereto. For example, instead of using a filter, an instrument that directly measures chromaticity in two dimensions (e.g., a two-dimensional colorimeter) or an instrument that directly measures the peak wavelength shift in two dimensions (such as a two-dimensional spectroradiometer) may be used. It goes without saying that "drive voltage" as used herein can be understood as "drive current".

[0097] 102 Camera 104 Lens 106 Optical filter 110 Display 112 Display screen

Claims

1. A method for generating display unevenness correction base data, comprising: an imaging device comprising an optical filter whose transmittance changes monotonically with respect to changes in wavelength near a specific wavelength of transmitted light, an imaging optical system, and a photoelectric conversion element, wherein an imaging device is prepared that converts light that enters the photoelectric conversion element into an electrical output signal, and the imaging device captures light from a display device having a plurality of subpixels that emit primary colors, and generates correction base data used to correct display unevenness of the display device, the method comprising: obtaining a first value of the output signal by transmitting light from each of the plurality of subpixels of a specific primary color through the optical filter; identifying the emission wavelength shift of each of the plurality of subpixels from a predetermined wavelength from the corresponding first value of the output signal; and generating correction base data used to correct display unevenness of the display device based on the emission wavelength shift.

2. The method for generating display uniformity correction base data according to claim 1, comprising: determining the emission wavelength shift, obtaining a second value of the output signal with respect to light transmitted through the imaging optical system without using the optical filter; and calculating the ratio of the first value to the second value for each of the plurality of subpixels.

3. The method for generating display unevenness correction base data according to claim 1, wherein, without using the optical filter, the display unevenness of the display device is corrected so that the brightness of the plurality of subpixels approaches a predetermined value, and this is performed before acquiring the data.

4. The method for generating display uniformity correction base data according to claim 1, wherein the determination of the emission wavelength shift is performed for the plurality of subpixels used for emission of the same primary color among the respective primary colors R, G, and B.

5. The method for generating display unevenness correction base data according to claim 1, wherein identifying the emission wavelength shift includes identifying the emission wavelength shift with respect to a set of subpixels in a subregion where the plurality of subpixels are arranged, and generating the correction base data includes generating correction base data for correcting display unevenness in the display device with respect to the set of subpixels.

6. A program that causes a computer to execute the display unevenness correction base data generation method described in any one of claims 1 to 5.

7. A method for producing a display device that corrects display unevenness based on correction base data used when correcting display unevenness of a display device obtained by imaging light from a display device having a plurality of subpixels that emit primary colors with the imaging device, wherein the imaging device includes an optical filter whose transmittance changes monotonically with respect to changes in wavelengths near a specific wavelength of transmitted light, an imaging optical system, and a photoelectric conversion element, and the imaging device converts light that enters the photoelectric conversion element into an electrical output signal, the method comprising: obtaining a first value of the output signal by transmitting light from each of the plurality of subpixels of a specific primary color through the optical filter; identifying the emission wavelength shift of each of the plurality of subpixels from a predetermined wavelength from the corresponding first value of the output signal; generating correction base data used when correcting display unevenness of the display device based on the emission wavelength shift; and storing the correction base data in the storage unit of the display device.

8. A method for producing the display device according to claim 7, comprising: determining the emission wavelength shift, obtaining a second value of the output signal with respect to light transmitted through the imaging optical system without using the optical filter; and calculating the ratio of the first value to the second value for each of the plurality of subpixels.

9. A method for producing the display device according to claim 7, wherein, without using the optical filter, the display uniformity of the display device is corrected so that the brightness of the plurality of subpixels approaches a predetermined value, and this is performed before obtaining the result.

10. A method for producing the display device according to claim 7, wherein the determination of the emission wavelength shift is performed for a plurality of subpixels used for emission of the same primary color among the respective primary colors R, G, and B.

11. A method for producing the display device according to claim 7, wherein identifying the emission wavelength shift includes identifying the emission wavelength shift with respect to a set of subpixels in a subregion where the plurality of subpixels are arranged, and generating the correction base data includes generating correction base data for correcting display unevenness in the display device with respect to the set of subpixels.

Images