Method and apparatus for evaluating discomfort from chromatic flicker

Abstract

To provide a method and apparatus for evaluating discomfort from chromatic flicker, configured to evaluate visual discomfort.SOLUTION: A method includes: a chromaticity storage step (Steps S1, S2) which acquires multiple pieces of image data in a row in a chronological order, and sequentially stores, for each pixel, chromaticity from each image data; a detection step (Steps S4, S10) which compares the stored chromaticity for each pixel and detects distances between the chromaticity, as color differences; and an evaluation step (Steps S3, S5, S7, S9, S11, S12) which evaluates visual discomfort on the basis of the chromaticity and the color differences. The evaluation step evaluates that the image data causes discomfort in the case where the chromaticity stored in the chromaticity storage step is highly saturated red and where color differences detected in a range beyond a predetermined area exceed a predetermined color difference more frequently than a predetermined frequency or number of time, or in the case where the chromaticity is not highly saturated red and where the color differences detected in the range beyond the predetermined area exceed the predetermined color difference more frequently than the predetermined frequency.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a method for evaluating the discomfort of colored flicker and a discomfort evaluation device.

Background Art

[0002] It is known that flickering (flicker) caused by changes in light brightness and color sometimes causes discomfort and may induce eye fatigue, headache, dizziness, etc. Such discomfort caused by visual information is called visual discomfort, and for people with visual hypersensitivity, there is also a risk of causing photosensitive seizures accompanied by spasms (see, for example, Non-Patent Document 1). In fact, there are also cases where the flickering of colors and lights in video expression and lighting production has caused photosensitive seizures in viewers (see, for example, Non-Patent Document 2).

[0003] With the remarkable development of video technology, in recent years, with the ability to achieve more vivid and flamboyant expressions, the risk of viewers having photosensitive seizures has increased. In addition, the increased time spent looking at smartphones, gaming devices, personal computers, etc. has also increased the risk of having photosensitive seizures.

[0004] Conventionally, a technique for detecting flicker based on the amount of luminance change in a video signal has been proposed. For example, Patent Document 1 discloses a technique for detecting flicker using the extreme value of the pixel value detected for each pixel of the video signal and information regarding the timing at which the extreme value occurs.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] The invention of Patent Document 1 detects changes in luminance values in pixel units, and detects strong flicker when the magnitude of the luminance difference, the timing at which the luminance difference occurs, and the number of occurrences of the luminance difference exceed predetermined criteria. However, since this method does not include the subjective evaluation of the observer, there is a possibility that flicker that actually causes strong visual discomfort to the observer may not be detected. In addition, flicker that may evoke visual discomfort is not limited to that caused by luminance differences. According to Non-Patent Document 3, flicker due to differences in the appearance of colors (color differences) may also evoke visual discomfort, as it is explained that special attention needs to be paid to the blinking of "bright red" in particular. In a technique for detecting flicker due to luminance differences such as Patent Document 1, there is a possibility that blinking due to color differences, that is, chromatic flicker, which causes strong visual discomfort to the observer, may not be detected. In addition, regarding "bright red" in Non-Patent Document 3, there is a problem that only the criteria based on luminance values are described, and the criteria based on chromaticity values are not described.

[0008] The technology disclosed herein has been made in view of such points, and an object thereof is to provide an evaluation method and an evaluation apparatus that detect flicker based on chromaticity and color difference that could not be detected by conventional technologies and evaluate whether or not it gives a strong visual discomfort to an observer.

Means for Solving the Problems

[0009] The inventor of the present application developed an unpleasantness evaluation method and an evaluation apparatus for chromatic flicker by clarifying the relationship between chromaticity and color difference and unpleasantness in chromatic flicker.

[0010] This disclosure is A method for evaluating visual discomfort given by a detection target in which at least one of hue and chroma changes over time, A chromaticity memory step of continuously acquiring a plurality of image data of the detection target along a time series and sequentially storing chromaticity for each pixel from each of the image data, A detection step of comparing the sequentially stored chromaticities for each pixel and detecting the distance between the chromaticities as a color difference, An evaluation step of evaluating the visual discomfort of the detection target based on the chromaticity and the color difference, and The evaluation step is When the chromaticity stored in the chromaticity memory step is high-chroma red within a predetermined chromaticity range, and the color difference detected in a range exceeding a predetermined area exceeds a predetermined frequency or a predetermined number of times and exceeds a predetermined color difference, or When the chromaticity stored in the chromaticity memory step is not high-chroma red within a predetermined chromaticity range, and the color difference detected in a range exceeding a predetermined area exceeds a predetermined frequency and exceeds a predetermined color difference, The detection target is evaluated as causing discomfort.

[0011] According to the discomfort evaluation method of the present disclosure, it is possible to detect chromatic flicker that may cause discomfort based on the time change of color, and to evaluate the discomfort of the detection target.

[0012] The present disclosure further relates to a device for evaluating the discomfort of chromatic flicker that visually evaluates the discomfort given by a detection target whose at least one of hue and chroma changes over time, a chromaticity storage unit that continuously acquires a plurality of image data of the detection target in time series and sequentially stores chromaticity from the image data for each pixel; a detection unit that compares the sequentially stored chromaticities for each pixel and detects the distance between the chromaticities as a color difference; and an evaluation unit that evaluates visual discomfort based on the chromaticity and the color difference. The evaluation unit evaluates the detection target as causing discomfort when the chromaticity stored in the chromaticity storage unit is high-chroma red within a predetermined chromaticity range and the color difference detected in a range exceeding a predetermined area exceeds a predetermined color difference more than a predetermined frequency or a predetermined number of times, or evaluates the detection target as causing discomfort when the chromaticity stored in the chromaticity storage unit is not high-chroma red within a predetermined chromaticity range and the color difference detected in a range exceeding a predetermined area exceeds a predetermined color difference more than a predetermined frequency. It is characterized by evaluating the detection target as causing discomfort.

[0013] In the evaluation method and evaluation device of the present disclosure, the chromaticity is preferably the a * a * b * chromaticity in the a * b * chromaticity system. This is because the L * a * b * chromaticity system is one of the homogeneous color spaces (uniform color spaces) close to human perception and is most commonly used to represent color differences.

[0014] With this configuration, it is possible to detect chromaticity and color difference that are more correlated with discomfort and obtain more reliable results.

Advantages of the Invention

[0015] As described above, according to the present disclosure, it is possible to provide an evaluation method and an evaluation apparatus that detect chromatic flicker that could not be detected by conventional techniques and evaluate whether or not it gives a visual discomfort. By predicting the discomfort caused by the evaluation target, it becomes possible to prevent symptoms such as discomfort caused by visual information, headache, dizziness, and photosensitive epilepsy attacks, and it is possible to contribute to the improvement of the safety of visual content.

Brief Description of Drawings

[0016]

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Embodiments for Carrying Out the Invention

[0017] Hereinafter, the method and apparatus for evaluating discomfort of chromatic flicker of the present disclosure will be described in detail.

[0018] The method and apparatus for evaluating discomfort of chromatic flicker of the present disclosure evaluate the discomfort visually given from a detection target in which at least one of hue and saturation changes with time.

[0019] The detection target may be any object as long as it is an object that can visually recognize that at least one of hue and saturation is changing with time. For example, it includes images, pictures, videos, etc. projected on a monitor, a TV screen, a screen, a wall, etc. and lighting.

[0020] The evaluation method includes the following steps. 1) A chromaticity storage step of continuously acquiring a plurality of image data of the detection target along a time series and sequentially storing chromaticity for each pixel from each of the image data. 2) A detection step of comparing the sequentially stored chromaticities for each pixel and detecting the distance between chromaticities as a color difference. 3) An evaluation step of evaluating the visual discomfort of the detection target based on the chromaticity and the color difference.

[0021] Specifically, the chromaticity memory step is executed by measuring the detection target with, for example, a color luminance meter or a spectral radiance meter. The chromaticity to be memorized is, for example, the chromaticity represented by the XYZ color space system. Preferably, it is the chromaticity in the L * a * b * a in the color space system * b * chromaticity. This is because the L * a * b * color space system is one of the homogeneous color spaces (uniform color spaces) close to human sensation and is most frequently used to represent color differences. The measurement of chromaticity may be performed on the whole or a part of the acquired image.

[0022] The XYZ color space system is a way of representing colors that was approved as a standard color space system by the International Commission on Illumination (CIE) in 1931. Since colors are represented by the color mixture ratio (X + Y + Z = 1), the value of Z is determined if the values of X and Y are determined. When representing a color using xy chromaticity coordinate values, it can be expressed by xyY values that combine the xy values indicating hue and chroma and the Y value indicating luminance. The conversion from xyY values to XYZ values uses the following formulas (1), (2), and (3).

[0023]

Equation

[0024] L * a * b * The color space system is a color space system based on the XYZ color space system. It is one of the homogeneous color spaces (uniform color spaces) close to human sensation, standardized by the International Commission on Illumination in 1976, and is most frequently used to represent color differences. Since the color differences distinguishable by humans vary depending on the color region in the XYZ color space system, the L * a * b * color space system is the one that has been standardized so that the color differences distinguishable by humans do not vary depending on the color region. L *a * b * When expressing color using a color space system, a represents the perceptual chromaticity * b * value, and L represents the lightness * It can be expressed by values. a * b * values represent hue and chroma. L * a * b * To obtain the a and b values, first use a color luminance meter or a spectral radiance meter to measure the xy chromaticity coordinate values and the luminance (corresponding to Y, unit: cd / m 2 ). Apply the above formulas (1), (2), and (3) to the xyY to obtain the XYZ values. Depending on the color luminance meter or spectral radiance meter used, the XYZ values may be given.

[0025] There is also a conversion formula for calculating the XYZ values from the RGB values, but when the XYZ values can be measured with a luminance meter, more accurate values can be obtained.

[0026] Apply the following formulas (4), (5), and (6) to the XYZ values to obtain the L * a * b * values. Xn, Yn, and Zn represent the XYZ values of the reference white respectively.

[0027]

Equation

[0028] The function f is defined as in the following formula (7).

[0029]

Equation

[0030] For example, take the coordinates of white as the reference value for achromatic colors, and the distance from there as the chroma. The chroma is represented by C * as shown in the following formula (8). The longer the distance from the reference value, the higher the chroma.

[0031]

Equation

[0032] For example, the color difference between two colors may be a ΔE value approximated to the shape of the color discrimination region of the human eye. ΔE 00 is obtained from the CIE DE2000 color difference formula and is defined as in the following formula (9) (G. Sharma, W. Wu, and E. N. Dalal, The CIEDE2000 color-difference formula: Implementation notes, supplementary test data, and mathematical observations, Color Research & Application, 30-1 (2005), 21-30.). Formula (9) is based on the lightness difference ΔL 00 、chroma difference ΔC * 、and hue difference ΔH * 、and is obtained by adding corrections with the weighting coefficients SL, SC, SH and the parameter coefficients kL, kC, kH. *

[0033]

Equation

[0034] In the detection step, the color difference for each pixel between a plurality of image data that are temporally continuous is calculated as a color difference using the above-described calculation formula. In the evaluation step, the visual discomfort of the detection target is evaluated based on the chromaticity and the color difference. In the evaluation step, when the chromaticity is a highly saturated red within a predetermined range and the color difference detected in a range exceeding a predetermined area exceeds a predetermined color difference at a predetermined frequency or a predetermined number of times, the evaluation is made such that the discomfort is greater than when the highly saturated red is not included. However, when the chromaticity is not a highly saturated red within a predetermined range and the color difference detected in a range exceeding a predetermined area exceeds a predetermined color difference at a predetermined frequency, the evaluation is made such that the discomfort is as large as when the highly saturated red is included.

[0035] ​ The color difference determined to cause discomfort may be detected, for example, if it occurs at a frequency of two or more times per second, or even if it occurs less than two times per second but repeats four or more times and occurs in an area exceeding 17 degrees in all directions of the viewing angle. The viewing angle is the angle formed by the object projected onto the eye and is also called the visual field angle formed by the object of view. As shown in the following formula (10), the viewing angle A (unit: [degree]) is calculated from the distance to the object of view (observation distance D) and the size s of the object of view. In formula (10), "arctan" represents the inverse tangent.

[0036]

Number

[0037] The threshold value of the magnitude of the color difference determined to cause discomfort may be set such that the ΔE 00 value is 45. However, one of the two colors used for calculating the color difference shall be a highly saturated red. The highly saturated red that may cause discomfort is, for example, a * value greater than 50, and a b * value greater than 50, and a red having a chroma with a C * value greater than 70. The chroma of the red determined to cause discomfort may be set as a predetermined chroma as a threshold value in advance. When one of the two colors used for calculating the color difference does not include a highly saturated red that may cause discomfort, the threshold value of the magnitude of the color difference determined to cause discomfort may be set such that the ΔE 00 value is 80.

[0038] The present invention can be implemented as a device for evaluating the discomfort of chromatic flicker that evaluates the discomfort visually given from a detection target whose at least one of hue and chroma changes with time.

[0039] [Device for Evaluating Discomfort of Chromatic Flicker] FIG. 1 is a block diagram showing an example of the configuration of the discomfort evaluation apparatus of the present invention. The discomfort evaluation apparatus 1 continuously acquires image data of a detection target in time series, calculates the difference in chromaticity between the image data as a color difference, and evaluates visual discomfort based on the chromaticity and the color difference. As shown in FIG. 1, the control unit 11, the detection unit 12, the storage unit 13, the evaluation unit 14, and the display unit 15 are provided.

[0040] The control unit 11 includes, for example, one or more arithmetic processing units such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit), reads out and executes the chromaticity, color difference, and stored programs recorded in the storage unit 13, and performs various control processes for the discomfort evaluation apparatus 1. The detection unit 12 continuously acquires a plurality of image data of the detection target in time series and detects the chromaticity from each image data.

[0041] The detection unit 12 is, for example, a color luminance meter or a spectral radiance meter, and detects the chromaticity by measuring the detection target. The chromaticity detected by the detection unit 12 is stored in the storage unit 13 and output to the evaluation unit 14.

[0042] The storage unit 13 is a storage medium that stores information necessary for realizing the functions of the discomfort evaluation apparatus 1, calculation programs, and the like. For example, semiconductor elements such as RAM and ROM, hard disks, and the like. The storage unit 13 stores, for example, the chromaticity detected by the detection unit 12, the threshold value of the chroma of red that may cause discomfort, the threshold value of the color difference that may cause discomfort, and the like. A chromaticity storage unit that continuously acquires a plurality of image data in time series and sequentially stores the chromaticity for each pixel from the image data is included in the storage unit 13.

[0043] The evaluation unit 14 calculates the color difference between pixels in a plurality of image data that are serially continuous over time as the color difference, and evaluates the visual discomfort based on the color difference. When the image data includes highly saturated red with a chromaticity value within a predetermined chromaticity range, if the color difference generated in a range exceeding a predetermined area exceeds a predetermined frequency or a predetermined number of times and is greater than a predetermined color difference, the evaluation unit 14 evaluates that the discomfort caused by the colored flicker is greater than when highly saturated red is not included. "Highly saturated red with a chromaticity value within a predetermined chromaticity range" means, for example, red having a value of a * greater than 50, and a value of b * in a range greater than 50, and having a chroma value of C * greater than 70. "Predetermined frequency" means, for example, two or more times per second. "Range exceeding a predetermined area" means, for example, a viewing angle of 17 degrees or more. "Predetermined number of times" means, for example, four or more times. "Predetermined color difference" means, for example, a ΔE 00 value of 45. The evaluation unit 14, for example, compares the chroma of the red detected by the detection unit 12 with the threshold of the red stored in the storage unit 13. When red with a chroma exceeding the threshold is detected, and the color difference calculated from the chromaticity detected by the detection unit 12 is compared with the threshold of the color difference stored in the storage unit 13, and the calculated color difference exceeds the threshold, the evaluation unit 14 evaluates that the evaluation target may cause discomfort. However, even when the image data does not include highly saturated red with a chromaticity value within a predetermined chromaticity range, if the color difference generated in a range exceeding a predetermined area exceeds a predetermined frequency and is greater than a predetermined color difference, the evaluation unit 14 evaluates that the discomfort caused by the colored flicker is as large as when highly saturated red is included. In this case, "range exceeding a predetermined area" means, for example, a viewing angle of 17 degrees or more. "Predetermined frequency" means, for example, two or more times per second. "Predetermined color difference" means, for example, a ΔE 00It is preferably set to a value larger than the threshold value of the color difference when the value is 80 and highly saturated red is included. The evaluation unit 14 compares, for example, the color difference calculated from the chromaticity detected by the detection unit 12 with the threshold value of the color difference stored in the evaluation unit 14, and evaluates that there is a possibility that the evaluation target gives discomfort when the calculated color difference exceeds the threshold value.

[0044] The display unit 15 is a display device such as a liquid crystal display, and displays the image data detected by the detection unit 12 and the evaluation result in the evaluation unit 14. The display unit 15 can, for example, display, in the temporal change of the detection target, which position and range of which image data may cause discomfort, or the intensity of discomfort quantitatively.

[0045] FIG. 2 is a flowchart showing an example of the evaluation executed in the discomfort evaluation device of the present invention. Based on FIG. 2, an example of the processing content executed by the discomfort evaluation device will be described. The evaluation executed in the discomfort evaluation device of the present invention does not necessarily have to be in the order of the flowchart shown in FIG. 2, and not all steps are essential. Also, the threshold values described in the selection process of FIG. 2 are examples and are not limited thereto. First, in step S1, the detection unit 12 such as a color luminance meter or a spectral radiance meter measures the evaluation target to acquire a plurality of image data of the evaluation target. Then, in step S2, the detection unit 12 calculates the chromaticity from each of the acquired plurality of image data, and the calculated chromaticity is sequentially stored for each pixel. The above chromaticity storage step corresponds to steps S1 and S2.

[0046] Subsequently, in step S3, the evaluation unit 14 compares and evaluates the calculated chromaticity with the threshold value of red stored in the storage unit 13. When red with a chromaticity exceeding the predetermined threshold value is detected (when the evaluation in step S3 is YES), the process proceeds to the next step S4. The threshold value of red is, for example, a * value 50, b * value 50, and C * value 70.

[0047] Subsequently, as a detection process, the evaluation unit 14 calculates a color difference from the chromaticity between the image data stored in the storage unit 13 (step S4).

[0048] In step S5, the evaluation unit 14 compares the calculated color difference with the threshold value of the color difference stored in the storage unit 13. If the calculated color difference does not exceed a predetermined area stored in the storage unit 13 (when the evaluation in step S5 is NO), the evaluation unit 14 outputs an evaluation result that the evaluation target "has no risk of causing discomfort" (step S6). For example, the predetermined area is 17 degrees of visual angle, and the threshold value of the color difference is 45.

[0049] On the other hand, if the calculated color difference exceeds the threshold value within a range where it exceeds the predetermined area stored in the storage unit 13 (when the evaluation in step S5 is YES), the evaluation unit 14 proceeds to the next step S7.

[0050] Subsequently, in step S7, the evaluation unit 14 compares the calculated color difference with the threshold value of the color difference stored in the storage unit 13. If the occurrence frequency of the calculated color difference exceeds the threshold value at a predetermined frequency stored in the storage unit 13 (when the evaluation in step S7 is YES), the evaluation unit 14 outputs an evaluation result that the evaluation target "has a risk of causing discomfort" (step S8). For example, the predetermined occurrence frequency is 2 times or more per second, and the threshold value of the color difference is 45.

[0051] On the other hand, if the occurrence frequency of the calculated color difference does not exceed the threshold value at the predetermined frequency stored in the storage unit 13 (when the evaluation in step S7 is NO), the process proceeds to the next step S9.

[0052] Subsequently, in step S9, the evaluation unit 14 compares the calculated color difference with the threshold value of the color difference stored in the storage unit 13. If the number of occurrences of the calculated color difference is equal to or less than a predetermined number stored in the storage unit 13 (when the evaluation in step 9 is NO), the evaluation unit 14 outputs an evaluation result that the evaluation target "has no risk of causing discomfort" (step S6). For example, the predetermined number of occurrences is 4 times, and the threshold value of the color difference is 45.

[0053] On the other hand, when the number of occurrences of the calculated color difference exceeds a predetermined number stored in the storage unit 13 (when the evaluation in step S9 is YES), the evaluation unit 14 outputs an evaluation result that the evaluation target "may cause discomfort" (step S8).

[0054] In step S3, the evaluation unit 14 compares and evaluates the calculated chromaticity with the red threshold value stored in the storage unit 13. When no red color with a chroma exceeding the predetermined threshold value is detected (when the evaluation in step S3 is NO), it proceeds to the next step S10.

[0055] As a detection process, the evaluation unit 14 calculates a color difference from the chromaticity between the image data stored in the storage unit 13 (step S10).

[0056] Subsequently, in step S11, the evaluation unit 14 compares the calculated color difference with the color difference threshold value stored in the storage unit 13. When the calculated color difference does not exceed a predetermined area stored in the storage unit 13 (when the evaluation in step S11 is NO), it outputs an evaluation result that the evaluation target "has no risk of causing discomfort" (step S6). For example, the predetermined area is 17 degrees of the viewing angle, and the color difference threshold value is 80.

[0057] On the other hand, when the calculated color difference exceeds the threshold value within a range exceeding a predetermined area stored in the storage unit 13 (when the evaluation in step S11 is YES), it proceeds to the next step S12.

[0058] Subsequently, in step S12, the evaluation unit 14 compares the calculated color difference with the color difference threshold value stored in the storage unit 13. When the occurrence frequency of the calculated color difference does not exceed the threshold value at a predetermined frequency stored in the storage unit 13 (when the evaluation in step S12 is NO), it outputs an evaluation result that the evaluation target "has no risk of causing discomfort" (step S6). For example, the predetermined occurrence frequency is 2 times or more per second, and the color difference threshold value is 80.

[0059] On the other hand, when the calculated occurrence frequency of the color difference exceeds the threshold at the predetermined frequency stored in the storage unit 13 (when the evaluation in step S12 is YES), an evaluation result that the evaluation target "may cause discomfort" is output (step S8).

[0060] As described above, depending on whether or not highly saturated red is included (YES or NO in step S3), the threshold of the color difference (ΔE 00 ) that is determined to cause discomfort is preferably set to different values. The threshold of the color difference when highly saturated red is not included is preferably set to a larger value than the threshold of the color difference when highly saturated red is included. Note that the above evaluation process corresponds to steps S3, S5, S7, and S9, S11, S12.

[0061] Examples of the output means for the evaluation result include, but are not limited to, display on the display unit 15. The evaluation result may not only indicate the presence or absence of the possibility of causing discomfort, but also quantitatively indicate the intensity of the discomfort.

[0062] By predicting the discomfort caused by the evaluation target with the discomfort evaluation device having the above-described configuration, it is possible to prevent symptoms such as discomfort, headache, dizziness, and photosensitive epilepsy attacks caused by visual information, and contribute to improving the safety of visual content.

[0063] [Experimental Results] The following describes an example of discomfort evaluation. First, the most saturated colors (colors on the color gamut of a computer display) of the three main hues (red, green, blue) and their intermediate colors (yellow, magenta, cyan) in the RGB color space system were used, and a chromatic flicker was generated in which two of these colors were combined and the two colors alternated, switching every second. The RGB color space system is a color space system that expresses colors using the three primary colors of light (red, green, blue), and this color space system is often basically used in computer processing. The two colors that make up the chromatic flicker were switched at a frequency of once per second and presented on a computer display. The presentation time was 4 seconds. The size of the chromatic flicker was 17 degrees square in visual angle. Fig. 3 shows an example of the chromatic flicker to be evaluated. Using a spectral radiance meter for the stimulus, the chromaticity of the chromatic flicker presented on the computer display was measured. On the other hand, observers (9 males and 16 females) were asked to evaluate the discomfort caused by the chromatic flicker presented to them. A 10-point rating scale (1: not at all uncomfortable ~ 10: very uncomfortable) was used for the evaluation. The rating scale method is a method of rating the degree of discomfort on an equally spaced scale and is often used as a technique for measuring visual discomfort.

[0064]

Table 1

[0065] The XYZ values, L * a * b * values, and C * values are shown in Table 1. The conversion formulas (4) to (7) were used for the conversion from the XYZ values to the L * a * b * values. The C * value was obtained using Equation (8). Fig. 4 shows the discomfort caused by the chromatic flicker rated by the observers, classified according to whether one of the two colors is red (YES) or not (NO). The vertical axis indicates the degree of discomfort, and the horizontal axis indicates the color difference (ΔE 00 ). The color difference ΔE 00 value is the L * a * b *It was obtained using Equation (9) based on the values. From Figure 4, when one of the two colors is a * > 50 and b * > 50 and C * > 70, it is a vivid red color, and when the color difference (ΔE 00 ) exceeds 45, it can be seen that a discomfort rating of about 5 or higher, which indicates a moderate level of discomfort, occurs. Figure 5 shows the results of averaging the discomfort ratings shown in Figure 4 for whether one of the two colors is red (YES) or not (NO). The asterisks in Figure 5 are the results of a t-test regarding the difference from the discomfort rating of 5 indicating a moderate level of discomfort. **** indicates that it is significant with p <.0001. From Figure 5, when one of the two colors is a * > 50 and b * > 50 and C * > 70, it is a vivid red color, and when the color difference (ΔE 00 ) exceeds 45, a discomfort of moderate level or higher occurs, while the discomfort for the other two colors is significantly weaker than that of moderate level.

[0066] Subsequently, chromatic flickers of combinations of red and blue, red and green, or green and blue were used, and the saturation of each color was changed in four levels to let observers evaluate discomfort.

[0067]

Table 2

[0068] The XYZ values, L * a * b * values, and C * values obtained by chromaticity measurement are shown in Table 2. The conversion formulas (4) to (7) were used for the conversion from XYZ values to L * a * b * values. C *The value was obtained using Equation (8). Figures 6 to 10 show the discomfort with chromatic flicker evaluated by an observer, when one of the two colors is red and when one of the two colors is not red (the hues of the two colors are green and blue), respectively. Note that Figures 6 to 9 show, for the case where one of the two colors is red, the figures shown for each chroma of red. Figure 6 shows the case of red with a low chroma (C * = 11.31), Figure 7 shows the case of red with a medium chroma (C * = 38.90), Figure 8 shows the case of red with a high chroma (C * = 73.55), and Figure 9 shows the results for the case of red with a very high chroma (C * = 91.93). The vertical axis represents discomfort, and the horizontal axis represents the color difference (ΔE 00 ). When the chromatic flicker contains bright red with a * > 50, b * > 50, and C * > 70, and the color difference (ΔE 00 ) between the two colors exceeds 45, as shown in Figures 8 and 9, discomfort tends to occur at about the same level as or higher than the medium rating value of 5. This tendency was not observed for low-chroma red with C * of 70 or less shown in Figures 6 and 7, or for the case where one of the two colors is not red shown in Figure 10. Figure 11 shows the results of averaging the discomfort rating values shown in Figures 6 to 10 for each case where one of the two colors is red and where one of the two colors is not red (for the case where one of the two colors is red, for each chroma of red). The asterisks in Figure 11 represent the results of a t-test regarding the difference from the rating value of 5 indicating medium discomfort. **** indicates p <.0001, and * indicates p <.05, respectively, showing significance. From Figure 11, it can be seen that when one of the two colors is bright red with a * > 50, b * > 50, and C * > 70, and the color difference (ΔE 00 ) between the two colors exceeds 45, medium or higher discomfort occurs, while the discomfort for the other two colors is significantly weaker than medium.

[0069] Figures 12 to 15 show the discomfort with respect to chromatic flicker evaluated by observers for each of the two-color hues. The two-color hues are red and green, red and blue, and blue and green. The vertical axis represents discomfort, and the horizontal axis represents the color difference (ΔE 00 ). Note that the lightness of the two colors is made equal, and as the red color, in Figure 12, a low-chroma (C * = 11) red color is used, in Figure 13, a medium-chroma (C * = 39) red color is used, in Figure 14, a high-chroma (C * = 74) red color is used, and in Figure 15, a very high-chroma (C * = 92) red color is used. From Figures 12 to 15, even when the lightness of the two colors is equal, when there is a vivid red color with a * > 50 and b * > 50 and C * > 70 is included, and the color difference (ΔE 00 ) between the two colors exceeds 45, a discomfort tendency of about the same level as or higher than the medium rating value of 5 is observed. Therefore, it can be confirmed that the results shown in Figures 4 to 11 are not due to the lightness difference between the two colors.

[0070] Figure 16 shows the discomfort with respect to chromatic flicker evaluated by observers for each combination of two colors (for each color difference). Here, the two-color hues are red, green, and blue shown in Table 1. The color difference (ΔE * ) was calculated from the L * a * b 00 values shown in Table 1. The vertical axis represents discomfort, and the horizontal axis represents the number of times the two colors switch in one second. It can be seen that the discomfort of chromatic flicker where the two colors switch at a frequency of more than once per second is about the same level as or stronger than the discomfort of chromatic flicker where the two colors switch at a frequency of once per second. Also, even when one of the two colors is not a vivid red color with a * > 50 and b * > 50 and C * > 70, when the color difference (ΔE 00 ) between the two colors exceeds 80, when the two colors switch at a frequency of two or more times per second, the discomfort is about the same level as or stronger than the medium rating value of 5.

[0071] When the area of a chromatic flicker where two colors switch 1 to 8 times per second exceeds a viewing angle of 17 degrees, it has been confirmed that a discomfort similar to or stronger than that in the case of a viewing angle of 17 degrees occurs.

[0072] When a chromatic flicker where two colors switch once per second was presented 1 to 8 times, it has been confirmed that there is no difference in discomfort for presentation times exceeding 4 times.

Explanation of Signs

[0073] 1 Discomfort evaluation device 11 Control unit 12 Detection unit 13 Memory unit 14 Evaluation unit 15 Display unit

Claims

1. A method for evaluating a visual discomfort caused by a detection object in which at least one of hue and saturation changes over time, comprising the steps of: a chromaticity storage step of acquiring a plurality of image data of the detection target in a time series manner and sequentially storing chromaticity from each of the image data for each pixel; a detection step of comparing the sequentially stored chromaticities for each pixel and detecting a distance between the chromaticities as a color difference; and evaluating a visual discomfort of the detection target based on the chromaticity and the color difference, The evaluation step includes: When the chromaticity stored in the chromaticity storage step is a highly saturated red within a predetermined chromaticity range, and the color difference detected in a range exceeding a predetermined area exceeds a predetermined color difference with a predetermined frequency or a predetermined number of times, or When the chromaticity stored in the chromaticity storage step is not a high saturation red within a predetermined chromaticity range, and the color difference detected in a range exceeding a predetermined area exceeds a predetermined frequency and exceeds a predetermined color difference, A method for evaluating discomfort caused by chromatic flicker, the method comprising: evaluating the detection target as something that causes discomfort.

2. The chromaticity is L * a * b * The method for evaluating discomfort caused by chromatic flicker according to claim 1, wherein the discomfort is evaluated by measuring chromaticity.

3. An apparatus for evaluating discomfort caused by chromatic flicker, which evaluates a visual discomfort caused by a detection target in which at least one of hue and saturation changes over time, comprising: a chromaticity storage unit that continuously acquires a plurality of image data of the detection target in a time series manner and sequentially stores chromaticity from each of the image data for each pixel; a detection unit that compares the sequentially stored chromaticities for each pixel and detects a distance between the chromaticities as a color difference; an evaluation unit that evaluates visual discomfort based on the chromaticity and the color difference, The evaluation unit is When the chromaticity stored in the chromaticity storage unit is a highly saturated red within a predetermined chromaticity range, and the color difference detected in a range exceeding a predetermined area exceeds a predetermined color difference with a predetermined frequency or a predetermined number of times, or When the chromaticity stored in the chromaticity storage unit is not a high-saturation red within a predetermined chromaticity range, and the color difference detected in a range exceeding a predetermined area exceeds a predetermined frequency and exceeds a predetermined color difference, An apparatus for evaluating discomfort caused by chromatic flicker, which evaluates the detection target as something that causes discomfort.

4. The chromaticity is L * a * b * 4. The apparatus for evaluating discomfort caused by chromatic flicker according to claim 3, wherein the discomfort is evaluated by measuring chromaticity.

Images