JP6335483B2 - Correction method, correction device, and program - Google Patents

Description

The present invention relates to a correction method , a correction device , and a program.

  In recent years, the display quality of display devices such as TV monitors, PC monitors, and various business monitors has been greatly improved. The color reproduction accuracy of display devices is also progressing so that a wider range of colors can be reproduced with higher fidelity. For example, as standards based on the CIE XYZ color model, the Adobe-RGB standard, the DCI-P3 standard, and the like, which have higher color reproduction accuracy than the sRGB standard, have been proposed. Such high-precision color reproduction is maintained by measuring a display performance of the display device precisely and performing a process called calibration for finely adjusting the display device so that correct color display is performed.

Research on the mechanism of human vision is also progressing, and knowledge about higher-dimensional visual functions not included in the above XYZ color model has been obtained.
For example, the reflected light spectrum of an object under ambient light changes according to the change in the ambient light spectral distribution, but humans correct the change (change in the reflected light spectrum) and the same object is the same. It has a visual function called color adaptation that recognizes the color of the image. Due to chromatic adaptation, humans may recognize the colors as the same color even if they have different chromaticity coordinates in the XYZ color model. Specifically, human beings recognize that the XYZ color model is the same color even if the chromaticity coordinates are different in the XYZ color model due to the chromatic adaptation according to the change of the ambient light. Conversely, due to chromatic adaptation, humans may recognize different colors even if the chromaticity coordinates are the same in the XYZ color model.
New color models that incorporate such human visual characteristics have also been proposed. Specifically, a color model called CIE CAM has been proposed.

Therefore, by performing calibration in consideration of the use environment of the display device (user's visual environment), the user can recognize (perceive) a color with higher fidelity (a color intended by the creator of the image data). It is expected that it will be possible to display.
Such a calibration method is disclosed in Patent Document 1, for example.

JP 2006-349835 A

  When performing calibration in consideration of chromatic adaptation, it is necessary to acquire information on the visual environment. For example, in the above-described color model called CIE CAM, it is necessary to set “white” (hereinafter referred to as “reference white”) as a reference for color adaptation using information on the visual environment. As calibration in consideration of chromatic adaptation, calibration is performed such that a display color deviation (perceptual deviation) with respect to the reference white becomes a desired value.

In Patent Document 1, white paper is set so that ambient light strikes during calibration, and reflected light obtained by reflecting the ambient light on the white paper is measured using a colorimeter. The measured reflected light color is used as the reference white color. As the colorimeter, a measuring device that measures the luminance and chromaticity of a single measurement point is used.
Therefore, in the conventional method, every time calibration is performed, the work of measuring the reflected light reflected by the white paper must be performed, and the work for calibration (work for obtaining information on the visual environment) is complicated. It is.

  Moreover, if the technique disclosed in Patent Document 1 is used, a change in perceived color (color perceived by the user) due to a change in ambient light can be reduced. However, the color of the screen perceived by the user depends not only on ambient light, but also on the color of an object (an object around the screen) that enters the user's eyes when the user looks at the screen. Specifically, the color of the screen perceived by the user is considered to be determined by the color of an object that enters the user's eyes when the user looks at the screen. However, in the conventional method, the color of an object that enters the eye when the user looks at the screen is not considered, and calibration is performed based on the color of the reflected light of the white paper. Therefore, in the conventional method, when the color (color tone) of an object entering the eyes when the user looks at the screen is different from that of white paper, calibration may not be performed with high accuracy.

  An object of the present invention is to provide a technique capable of easily and accurately performing display color calibration of a display device.

The first aspect of the present invention is:
A correction method for correcting a display image displayed in a display area ,
In a state in which the display image is displayed on the display area, an image acquisition step of acquiring a captured image region is photographed including a periphery of the display area and the display area,
From the captured image, a first color is an inner color of the display region, a color acquiring the second color, which is the color of the surrounding of the display region,
A determining step of determining a target color of the first color based on the second color;
A correction step of correcting each pixel value of the display image by a difference between a pixel value indicating the first color and a pixel value indicating the target color;
I have a,
In the determining step, the second color is used as a reference white color, and the target color is determined so that a color appearance when the display image is viewed under the reference white color satisfies a predetermined condition. The correction method is characterized by the following.

The second aspect of the present invention is:
A correction device for correcting a display image displayed in a display area ,
In a state in which the display image is displayed on the display area, an image obtaining unit for obtaining a captured image region including the periphery of the display region and the display region is captured,
From the captured image, a first color is an inner color of the display region, a color acquisition means for acquiring the second color, which is the color of the surrounding of the display region,
Determining means for determining a target color of the first color based on the second color;
Correction means for correcting each pixel value of the display image by a difference between a pixel value indicating the first color and a pixel value indicating the target color;
I have a,
The determination unit uses the second color as a reference white color and determines the target color so that a color appearance when the display image is viewed under the reference white color satisfies a predetermined condition. The correction apparatus is characterized by the above.

According to a third aspect of the present invention, the computer executes each step of the correction method described above .
It is because of the program.

  According to the present invention, the display color of the display device can be calibrated with high accuracy and ease.

The figure which shows an example of the use condition of the display apparatus which concerns on Example 1. FIG. The figure which shows an example of a mode when performing the calibration which concerns on Example 1. FIG. The figure which shows an example of the picked-up image which concerns on Example 1. FIG. The figure which shows an example of the 1st detection process which concerns on Example 1, and a 2nd detection process. 1 is a block diagram illustrating an example of a configuration of a calibration apparatus according to a first embodiment. The figure which shows an example of the emission spectrum of the sub pixel which concerns on Example 1. FIG. The figure which shows the spectrum of D65 standard light source of CIE The figure which shows the spectrum of CIE F10 standard light source The figure which shows an example of the spectral reflectance characteristic of the wall surface concerning Example 2 The figure which shows an example of a mode when performing the calibration which concerns on Example 3. FIG. FIG. 10 is a diagram illustrating an example of a captured image according to the third embodiment. The figure which shows an example of the 2nd detection process which concerns on Example 3. FIG.

<Example 1>
Hereinafter, a calibration apparatus and a calibration method according to the first embodiment of the present invention will be described. The calibration device according to the present embodiment calibrates the display color of the display device.
FIG. 1 is a diagram illustrating an example of a usage state of the display device according to the present embodiment.
In the example of FIG. 1, the display device 100 is arranged on a desk with the wall surface 200 as the back. Therefore, when the user of the display device 100 views the screen of the display device 100, not only the screen of the display device 100 but also the wall surface 200 that is the background of the display device 100 can be seen by the user. The display device 100 and the wall surface 200 are illuminated by an illumination light source 300.
In this embodiment, for simplicity, the wall surface 200 has simple reflection characteristics. Specifically, the color of the wall surface 200 is white, and the wall surface 200 has a completely flat (constant) spectral reflectance in the visible light region. Further, it is assumed that the spectral reflectance of the wall surface 200 is 100%, and the light from the illumination light source 300 is completely diffusely reflected by the wall surface 200.

FIG. 2 is a diagram illustrating an example of a state when the display color of the display device 100 according to the present embodiment is calibrated.
As shown in FIG. 2, in this embodiment, when calibration is performed, a test color patch 101-a is displayed on the screen (display surface) 101 of the display device 100. The test color patch 101-a is an image for calibration, and is a reference image having a first predetermined color.
Then, the screen 101 is photographed by the digital camera 400 in a state where the test color patch 101-a is displayed. The digital camera 400 is used as a colorimeter when performing calibration. The digital camera 400 includes an image sensor having a plurality of pixels therein, and is arranged such that an image of a region including the screen 101 and the periphery of the display device 100 is formed on the image sensor. That is, the digital camera 400 is arranged so that an area including the screen 101 and the periphery of the display device 100 is photographed. FIG. 3 is a diagram illustrating an example of a captured image captured by the digital camera 400. In the example of FIG. 3, the display device 100 is shown in the center of the photographed image 401, and the test color patch 101-a is displayed on the screen 101. In addition, the periphery of the display device 100 is also reflected in the captured image 401. Specifically, the wall surface 200 that is the background of the display device 100 is shown.
Thereafter, desired measurement data is acquired by processing the captured image (captured image), and calibration is performed based on the acquired measurement data.

In the present embodiment, when calibration is performed, a plurality of test color patches having different colors and brightness are sequentially displayed on the screen. Then, for each of the plurality of test color patches, it is determined whether or not the color (photographed color) of the photographed test color patch matches the target color. If the shooting color does not match the target color, a correction value (a correction value for correcting the pixel value indicating the color of the test color patch) that matches the shooting color with the target color is determined and stored. The above process is performed for all the test color patches, thereby completing the calibration.
When using the display device after calibration has been performed, the optimum correction value (display) is selected from the stored correction values for each pixel value of the image (display image) input to the calibration device. Correction value corresponding to the pixel value of the display image) is read out and applied to the pixel value of the display image. The correction value is applied to the pixel value after being appropriately subjected to arithmetic processing as necessary. Then, the display image after correction (the display image after the process of applying the correction value) is displayed on the display device 100.
A plurality of test color patches may be displayed simultaneously. A stripe image composed of a plurality of reference images having different colors and brightness may be displayed.

When chromatic adaptation is not considered, one target color may be used for each test color patch regardless of the viewing environment. However, when considering chromatic adaptation, the color perceived when the user looks at the screen (perceived color) changes depending on the viewing environment, and thus a target color corresponding to the viewing environment must be used. Chromatic adaptation is a visual function in which the same object is recognized as the same color by correcting the change in the reflected light spectrum of the object in accordance with the change in the spectral distribution of the ambient light. Due to chromatic adaptation, humans may recognize the colors as the same color even if they have different chromaticity coordinates in the XYZ color model. Conversely, due to chromatic adaptation, humans may recognize different colors even if the chromaticity coordinates are the same in the XYZ color model.
In consideration of chromatic adaptation, the color of the screen perceived by the user is considered to be determined by the color of an object (an object around the screen) that enters the user's eyes when the user looks at the screen. Therefore, in this embodiment, the target color is determined based on the color of an object (an object around the screen) that enters the user's eyes when the user looks at the screen. Thereby, the display color of the display device can be calibrated with high accuracy.

FIG. 5 is a block diagram illustrating an example of the configuration of the calibration apparatus according to the present embodiment.
Hereinafter, the operation of each functional unit shown in FIG. 5 will be described along the calibration flow.
In this embodiment, an example in which the calibration apparatus is a separate apparatus from the display apparatus 100 will be described. However, the calibration apparatus may be incorporated in the display apparatus 100.

First, when image data of a test color patch is input to the calibration device as display image data (display image data), the display image data is sent to the data correction unit 2 and the target color determination unit 6. The data correction unit 2 outputs the display image data to the display device 100 without correcting the display image data. As a result, the test color patch is displayed on the screen 101 of the display device 100.
Note that the data correction unit 2 may perform correction using the correction value stored at the previous calibration on the display image data which is the image data of the test color patch. Then, the corrected image data may be output to the display device 100. In this case, the test color patch after correction using the correction value saved at the previous calibration is displayed on the screen 101.
Note that the image data of the test color patch may be input from the outside, or may be recorded in advance in the calibration apparatus.
When calibration is not performed, the display image data is sent to the data correction unit 2, corrected using the correction value stored at the previous (immediately preceding) calibration, and output to the display device 100. The

  The digital camera 400 generates image data (captured image data) of a captured image by capturing an area including the screen 101 and the periphery of the display device 100 in a state where the test color patch is displayed on the screen 101. . Then, the digital camera 400 outputs the captured image data to the area determination unit 5.

The area determination unit 5 displays the screen 101 and the display device 1 while the test color patch is displayed.
Captured image data obtained by capturing an area including around 00 is acquired from the digital camera 400 (image acquisition process).
Then, the area determination unit 5 acquires, as display color information, the first color that is the color (photographing color) inside the screen 101 from the photographed image, and the first color that is the surrounding color (photographing color) of the display device 100. The second color is acquired as visual environment information (color acquisition process).
In the present embodiment, the area determination unit 5 detects an area of the screen 101 from a captured image area by performing an image recognition process for detecting a pattern from an image (first detection process). Then, the area determination unit 5 acquires the color inside the area (area of the screen 101) detected by the first detection process as display color information. Specifically, the color of the test color patch displayed on the screen 101 is acquired as display color information. In this embodiment, the test color patch is displayed in a predetermined area of the screen 101. Therefore, the area of the test color patch can be determined based on the detection result of the first detection process.
Similarly, the area determination unit 5 detects an area around the display device 100 from the area of the captured image by performing an image recognition process (second detection process). Then, the area determination unit 5 acquires the color inside the region (region around the display device 100) detected in the second detection process as the visual environment information. Specifically, the average color of the area detected by the second detection process (average value of the shooting color) is acquired as the visual environment information.
Thereafter, the area determination unit 5 outputs the display color information to the comparison unit 7 and outputs the visual environment information to the target color determination unit 6.
Note that the image acquisition process, the color acquisition process, the first detection color, and the second detection process may be performed by different functional units.

FIG. 4 is a diagram illustrating an example of the first detection process and the second detection process.
In the present embodiment, captured image data captured in a state where the first predetermined pattern indicating the area of the screen 101 is displayed on the screen 101 is acquired. Then, the first predetermined pattern is detected from the captured image by the image recognition process, and the region indicated by the first predetermined pattern is detected as the region of the screen 101. In the example of FIG. 4, captured image data captured in a state where the patterns 101-b are displayed at the four corners of the area of the screen 101 is acquired. Then, an area 401-1 surrounded by a line connecting the four corner patterns 101-b is detected as an area of the screen 101.
In the present embodiment, the display device 100 includes a frame member 102 that surrounds the screen 101. Then, the region of the frame member 102 is detected from the captured image by the image recognition process, and the region outside the region of the frame member 102 is detected as a region around the display device 100. In the example of FIG. 4, the upper and left side regions 401-2 of the frame member 102 are detected as regions around the display device 100.

The first predetermined pattern is not limited to the four patterns 101-b. For example, the first predetermined pattern may be a rectangular pattern, or may be four straight lines indicating the upper, lower, left, and right sides of the screen 101.
Note that the area around the display device 100 is not limited to the area 401-2. For example, areas on the top, bottom, left, and right sides of the frame member 102 may be detected as areas around the display device 100. In addition, at least one of the upper, lower, left, and right sides of the frame member 102 may be detected as an area around the display device 100. However, in the lower area of the frame member 102, an object of a color that is not easily seen when viewing the screen (a stand of the display device 100, a desk on which the display device 100 is placed, or a desk placed on the desk) Small items, etc.). Since the color of such an object does not significantly affect chromatic adaptation, it does not need to be considered. Rather, it is preferable not to consider the color of such an object because it may not be possible to obtain highly accurate visual environment information. On the other hand, in the upper left and right side areas of the frame member 102, there are objects of color (such as walls) that often appear when the screen is viewed. Since the color of such an object greatly affects chromatic adaptation, it is preferable to consider it.

The target color determination unit 6 is based on the pixel value of the display image data input to the calibration apparatus and the visual environment information output from the area determination unit 5, and the target of display color information (first color). Determine the color. In the present embodiment, the color in which the change in the appearance of the color of the display image due to the change in the visual environment (visual environment information) is suppressed is determined as the target color. Specifically, the second color, which is the visual environment information, is used as the reference white color, and the appearance of the color when the display image (test color patch) is viewed under the reference white color satisfies a predetermined condition. The target color is determined so as to satisfy. Thereby, the display color optimal for the visual environment of the display apparatus 100 can be determined as the target color.
The target color determination unit 6 outputs the determined target color to the comparison unit 7.
In this embodiment, an example in which the target color is determined using the pixel value of the display image data will be described. However, when the pixel value of the display image data is determined in advance, only visual environment information is used. The target color can also be determined. For example, when the pixel value of the display image data is determined in advance, a function or table indicating the correspondence relationship between the visual environment information and the target color can be prepared in advance. Then, the target color can be determined from the visual environment information output from the area determination unit 5 using such a function or table.

The comparison unit 7 compares the first color, which is the display color information output from the area determination unit 5, with the target color output from the target color determination unit 6.
If the first color does not match the target color, the correction value is determined by the correction value determination unit 8. Then, the obtained correction value is sent from the correction value determination unit 8 to the data correction unit 2, and the image data of the test color patch is corrected using the obtained correction value. As a result, the display color of the test color patch is corrected. Thereafter, a series of processing from the photographing by the digital camera 400 to the comparison by the comparison unit 7 is performed again.
If the first color matches the target color, the calibration is terminated. At this time, if a correction value is obtained, the obtained correction value is stored in the correction value storage unit 9 as a correction value suitable for the pixel value of the test color patch.

  Note that the functional units shown in FIG. 5 do not necessarily have to exist as individual hardware. The function of each functional unit only needs to be realized in a series of calibration operations.

A method for determining the correction value will be specifically described.
Hereinafter, it is assumed that each pixel of the display device 100 includes a red subpixel (R), a green subpixel (G), and a blue subpixel (R). Further, the image data (subpixel value) given to each subpixel is a value of 8 bits (0 to 255), and the emission intensity of each subpixel increases linearly with the increase of the subpixel value. . When the subpixel value is 255, the spectrum shown in FIG. 6 is obtained as the spectrum (light emission spectrum) of the light beam emitted from each subpixel. The horizontal axis in FIG. 6 indicates the wavelength, and the vertical axis indicates the emission intensity.
In this embodiment, the CIECAM02 standard is adopted as a color model incorporating human visual characteristics that adapt to the visual environment, and processing that considers chromatic adaptation is performed in accordance with the CIECAM02 standard.
As described above, the calibration is generally performed for a plurality of pixel values having different colors and brightness, but an example in which calibration is performed for one pixel value will be described. Specifically, an example in which calibration is performed for pixel values of a color corresponding to LightSkin in a commonly used Gretag Macbeth color chart will be described.

First, several processes are performed in advance so that the calibration can be performed smoothly, and the predetermined conditions described above are recorded in the calibration apparatus. For example, when the calibration apparatus is shipped from the factory, predetermined conditions are determined and recorded in the calibration apparatus (a storage unit (not shown) included in the calibration apparatus). In the present embodiment, values of J (Lightness), C (Chroma), and h (Hue), which are relative color attributes, are used as predetermined conditions in the calibration. J, C, and h are “chromaticity coordinates according to the CIECAM02 standard” and “chromaticity coordinates representing“ appearance ”in consideration of chromatic adaptation.” J, C, and h are calibration coordinates. J, C, and h are determined for each of a plurality of pixel values (colors) of a plurality of test color patches.

For example, for LightSkin, J, C, and h are determined by the following method.
For LightSkin, x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] are defined as standard chromaticity coordinates under standard illumination (D65). FIG. 7 shows the spectrum of the CIE D65 standard light source. The standard chromaticity coordinates relating to LightSkin are chromaticity coordinates of a display color perceived as LightSkin under standard illumination (D65).
Then, J, C, and h related to LightSkin are determined (calculated) using the light source color of the D65 standard light source as the reference white color. In this example, it is assumed that 58.1643 is obtained as J regarding LightSkin, 21.1202 is obtained as C, and 34.171 is obtained as h.
Note that the reference white color used when determining J, C, and h is not limited to the light source color of the D65 standard light source.
Note that the values of J, C, and h may vary depending on the standard white color, parameters used in the CIECAM02 standard, and the like.

In the present embodiment, in order to perform calibration more smoothly, a plurality of pixel values to be calibrated are calibrated in association with the predetermined conditions (J, C, and h). Pre-recorded on the device. For example, for LightSkin, a pixel value that is perceived as a LightSkin color under standard illumination (D65) is recorded. Specifically, based on the display characteristics of the display device 100 (correspondence between subpixel values and emission spectra of subpixels), standard chromaticity coordinates x = 0.377, y = 0.345, and Y = A pixel value indicating a color of 35.8 [cd / m ² ] is determined (calculated). In this embodiment, it is assumed that 128 is obtained as the red subpixel value (R value), 64 is obtained as the green subpixel value (G value), and 46 is obtained as the blue subpixel value (B value). In the calibration, the pixel values (R value, G value, and B value) are used as default values (reference pixel values before correction).

A specific example of the operation at the time of calibration will be described below.
Below, the example in the case of calibrating about LightSkin is demonstrated.
Hereinafter, an example in which the spectrum of the indoor illumination light source 300 is not the above-described D65 but the spectrum of the CIE F10 standard light source will be described. FIG. 8 shows the spectrum of the CIE F10 standard light source.
As described above, in this embodiment, the color of the wall surface 200 is white, and the wall surface 200 has a completely flat (constant) spectral reflectance in the visible light region. Further, it is assumed that the spectral reflectance of the wall surface 200 is 100%, and the light from the illumination light source 300 is completely diffusely reflected by the wall surface 200.
Below, the example in case the illumination intensity of the illumination light source 300 with respect to the wall surface 200 used as the background of the display apparatus 100 is 314 [lux] is demonstrated. When the illuminance of the illumination light source 300 with respect to the wall surface 200 is 314 [lux], the brightness of the reflected light from the wall surface 200 is 100 [cd / m ² ].

Under such a visual environment, the area determination unit 5 acquires x = 0.3461, y = 0.3588, and luminance = 100 [cd / m ² ] as visual environment information.

In the target color determination unit 6, the display color perceived as LightSkin is determined as the target color by back calculation according to CIECAM02. Specifically, when x = 0.3461, y = 0.3588, and luminance = 100 [cd / m ² ] as a reference white, J = 58.1643, C = 21.1202, And the chromaticity coordinate of the color which satisfy | fills h = 34.171 is determined (calculated) as the target color regarding LightSkin.
The reference white color used here is different from the light source color of the D65 standard light source. Therefore, a chromaticity coordinate different from the standard chromaticity coordinate of LightSkin is obtained as a chromaticity coordinate (target color) that satisfies J = 58.1643, C = 21.1202, and h = 34.171. Specifically, x = 0.4065, y = 0.3650, and Y = 36.11 [cd / m ² ] are obtained as the target colors for LightSkin.

  In this embodiment, a predetermined condition corresponding to the pixel value is determined from the pixel value of the display image data input to the calibration apparatus and used. For example, when the pixel values of the display image data are R values = 128, G values = 64, and B values = 46, it is determined that the pixel values are LightSkin pixel values. Then, J = 58.1643, C = 21.1202, and h = 34.171 which are predetermined conditions corresponding to LightSkin are selected and used.

As described above, in this embodiment, the display image data input to the calibration apparatus is displayed without correction during calibration. In other words, the LightSkin test color patch (the test color patch having pixel values of R value = 128, G value = 64, and B value = 46) is displayed without correction.
The area determination unit 5 further obtains display color information that is the display color of the LightSkin test color patch. Under the visual environment described above, x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] are displayed as display color information that is the display color of the test color patch of LightSkin. To be acquired.

The comparison unit 7 compares the display color information with the target color. Here, the display color information x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] are the target colors x = 0.4065, y = 0.350, And Y = 36.11 [cd / m ² ] is different. Therefore, the correction value is determined by the correction value determination unit 8.

The correction value determination unit 8 determines (calculates) a pixel value indicating the target color from the target colors x = 0.4065, y = 0.3650, and Y = 36.11 [cd / m ² ]. The Further, a pixel value indicating the first color is determined from x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] which are display color information (first color). Is done. Then, the difference between the two obtained pixel values is determined as a correction value. Here, it is assumed that +15 is obtained as ΔR which is a correction value of R value, −1 is obtained as ΔG which is a correction value of G value, and −10 is obtained as ΔB which is a correction value of B value.

The correction value may be calculated using a function indicating the correspondence relationship between the two pixel values and the correction value, or may be determined using a table indicating such a correspondence relationship. Further, the correction value may be determined using information (table or function) indicating a correspondence relationship between the target color and the display color information x, y, and Y and the correction value. That is, the correction value may be determined using a function or a table that inputs x, y, and Y of the target color and display color information and outputs the correction value. In this embodiment, the example in which the correction value to be added to the pixel value is determined has been described. However, a correction value (correction coefficient) to be multiplied by the pixel value may be determined.

  The obtained correction value is sent to the data correction unit 2, and default display image data (display image data input to the calibration apparatus) is corrected. Then, a series of processes from photographing by the digital camera 400 to comparison by the comparison unit 7 are repeated until the display color information matches the target color. When the display color information matches the target color, the calibration for LightSkin is completed. At this time, when the correction value is obtained, the correction value determination unit 8 saves the correction value as the correction value corresponding to the pixel value of LightSkin (default pixel value) as the last obtained correction value. Store in part 9.

  By using the correction value, it is possible to reduce changes in the perceived color of the display image due to changes in the viewing environment. Specifically, it is possible to reduce the variation from the perceived color under the visual environment considered when determining the predetermined condition.

It is considered that the user perceives a color adapted to the surrounding color of the display device as the color of the display image. In particular, when there is a large region of the same color around the display image display device, such a color is highly likely to be perceived.
According to this embodiment, the target color is determined based on the surrounding color (photographing color) of the display device, and calibration is performed so that the display color matches the target color. As described above, in this embodiment, calibration is performed in consideration of the surrounding color of the display device, so that calibration can be performed with high accuracy. Specifically, by performing calibration in consideration of the surrounding color of the display device, not only the change in the perceived color due to the change of the illumination light source that illuminates the display device, but also the change of the object existing around the display device The change in the perceived color due to can also be reduced. For example, it is possible to reduce a change in perceived color due to the wallpaper pasted on the wall surface on the back side of the display device being replaced with a wallpaper having a color different from that before the replacement.
Further, in this embodiment, it is possible to acquire a reference white color by a simple process of acquiring a color from a photographed image, and it is possible to save the trouble of preparing a white paper for each calibration. . As a result, in the present embodiment, calibration can be easily performed.

<Example 2>
The calibration apparatus and calibration method according to Example 2 of the present invention will be described below.
Since the operation of each functional unit is the same as that in the first embodiment, only a specific example of processing will be described below.

In the present embodiment, D65 is used as an indoor illumination light source, but the reflection characteristics of the wall surface 200 are different from those of the first embodiment. The reflection characteristics of the wall surface 200 are not particularly limited, but in this embodiment, an example in which the wall surface 200 has a yellowish color (color tone) will be described. In this embodiment, the color of the wall surface 200 is referred to as “Light Yellow”. FIG. 9 shows the spectral reflectance characteristics of the wall surface 200 according to this example.
When the wall surface 200 has the spectral reflectance characteristics shown in FIG. 9, if the illuminance of the illumination light source 300 with respect to the wall surface 200 is set to 319 [lux] (a value slightly higher than that of the first embodiment), the brightness of the reflected light from the wall surface 200 is 100 [cd / m ² ].

Under the visual environment described above, the area determination unit 5 acquires x = 0.3204, y = 0.3398, and luminance = 100 [cd / m ² ] as the visual environment information.

In the target color determination unit 6, when x = 0.3204, y = 0.3398, and luminance = 100 [cd / m ² ] as a reference white, J = 58.1643, C = 21.1. A chromaticity coordinate of a color satisfying 1202 and h = 34.171 is obtained as a target color for LightSkin.
Even if the illumination light source is D65, the color of the wall surface 200 is not white. Therefore, here, a color different from the light source color of the D65 standard light source is used as the reference white. As a result, chromaticity coordinates different from the standard chromaticity coordinates of LightSkin are obtained as chromaticity coordinates (target colors) that satisfy J = 58.1643, C = 21.1202, and h = 34.171. Specifically, x = 0.3840, y = 0.3525, and Y = 35.87 [cd / m ² ] are obtained as target colors for LightSkin.

As in the first embodiment, the area determination unit 5 further acquires display color information that is the display color of the LightSkin test color patch. Under the visual environment described above, x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] are displayed as display color information that is the display color of the test color patch of LightSkin. To be acquired.

The comparison unit 7 compares the display color information with the target color. Here, the display color information x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] are the target colors x = 0.3840, y = 0.3525, And it is different from Y = 35.87 [cd / m ² ]. Therefore, the correction value is determined by the correction value determination unit 8.

The correction value determination unit 8 determines the pixel value indicating the target color from the target colors x = 0.3840, y = 0.3525, and Y = 35.87 [cd / m ² ]. Further, a pixel value indicating the first color is determined from x = 0.377, y = 0.345, and Y = 35.8 [cd / m ² ] which are display color information (first color). Is done. Then, the difference between the two obtained pixel values is determined as a correction value. Here, it is assumed that +2 is obtained as ΔR which is a correction value of R value, −1 is obtained as ΔG which is a correction value of G value, and −4 is obtained as ΔB which is a correction value of B value.

  The obtained correction value is sent to the data correction unit 2, and default display image data (display image data input to the calibration apparatus) is corrected. Then, a series of processes from photographing by the digital camera 400 to comparison by the comparison unit 7 are repeated until the display color information matches the target color. When the display color information matches the target color, the calibration for LightSkin is completed. At this time, when the correction value is obtained, the correction value determination unit 8 saves the correction value as the correction value corresponding to the pixel value of LightSkin (default pixel value) as the last obtained correction value. Store in part 9.

  By using the correction value, it is possible to reduce changes in the perceived color of the display image due to changes in the viewing environment. Specifically, it is possible to reduce the variation from the perceived color under the visual environment considered when determining the predetermined condition.

  As described above, according to the present embodiment, not only the change in the perceived color due to the change in the illumination light source that illuminates the display device, but also the change in the perceived color due to the change in the object existing around the display device is reduced. You can see that

  In the first and second embodiments, the example in which the average color of the area around the display device is acquired as the visual environment information (second color) is described. However, the visual environment information is not limited to this. For example, the visual environment information may be a shooting color that is most often included in the surrounding area of the display device, or an intermediate color of the surrounding area of the display device (an intermediate value of the shooting color included in the surrounding area of the display device) ).

  In the first and second embodiments, the example in which the area indicated by the first predetermined pattern is detected as the screen area and the area outside the frame member area is detected as the area around the display device has been described. However, the region detection method is not limited to this. For example, an area surrounded by the frame member may be detected as a screen area. An area outside the screen area may be detected as an area around the display device.

  In the first and second embodiments, the example in which the screen area and the surrounding area of the display device are detected by the image recognition process has been described. However, the image recognition process may not be performed. For example, the photographed image may be displayed on the screen, and the user may specify the screen area shown in the photographed image and the area around the display device. When the relative positional relationship between the display device and the digital camera is constant, the screen area and the area around the display device can be determined in advance.

  In the first and second embodiments, the example in which the display color information and the visual environment information are acquired based on the detection results of the screen area and the surrounding area of the display device has been described. However, the display color information and the visual environment information are acquired. The method is not limited to this. For example, the captured image may be displayed on the screen, and the user may specify the position for acquiring the display color information (the position in the captured image) and the position for acquiring the visual environment information. Further, when the relative positional relationship between the display device and the digital camera is constant, a position for acquiring display color information and a position for acquiring visual environment information can be determined in advance.

  In addition, although Example 2 demonstrates the example at the time of using D65 as an illumination light source, even if light sources other than D65 are used as an illumination light source, the effect mentioned above is acquired by the process similar to the process mentioned above. . That is, even when a light source other than D65 is used as the indoor illumination light source and the color of the wall surface 200 is not white, the above-described effects can be obtained.

<Example 3>
Hereinafter, a calibration apparatus and a calibration method according to the third embodiment of the present invention will be described.
Hereinafter, differences from the first and second embodiments will be described in detail, and the description of the same processes as those of the first and second embodiments will be omitted.
The calibration apparatus according to the present embodiment has the same configuration as that of Embodiments 1 and 2 (FIG. 5).

  In Examples 1 and 2, the average color of the area around the display device is used as the visual environment information. However, in such a method, when a color having a large total area does not exist in a peripheral area of the display device and there are a plurality of colors having a small total area, a color different from a color that greatly affects the perceived color is obtained. It may be acquired as visual environment information. For example, when the display device is not placed close to the wall surface, a color different from the color that greatly affects the perceived color may be acquired as the visual environment information. Even when the wall surface has a color far from the ideal white color, a color different from the color that greatly affects the perceived color may be acquired as the visual environment information. As a result, highly accurate calibration may not be realized. In such a case, more accurate calibration is expected by acquiring the color (photographing color) of an object of a predetermined color as visual environment information and using the color of the predetermined object as a reference white color. The

  Therefore, in this embodiment, the color of the reference object is acquired as visual environment information (second color) from a photographed image taken with the reference object having the second predetermined color around the display device. . That is, the color of the light emitted from the illumination light source and emitted from the reference object is acquired as the viewing environment information. And the 2nd color which is visual environment information is used as standard white. Thereby, when highly accurate calibration cannot be performed by the methods of the first and second embodiments, it is possible to perform calibration with higher accuracy than those of the first and second embodiments.

FIG. 10 is a diagram illustrating an example of a state when the display color of the display device 100 according to the present embodiment is calibrated.
As shown in FIG. 10, in this embodiment, as in the first and second embodiments, the test color patch 101-a is displayed on the screen 101 when performing calibration. Further, the reference object 500 is disposed in the vicinity of the display device 100.
Then, with the test color patch 101-a displayed on the screen 101 and the reference object 500 being disposed in the vicinity of the display device 100, the screen 10 is displayed by the digital camera 400.
1 is photographed. In the digital camera 400, an area including the screen 101 and the reference object 500 is photographed. FIG. 11 is a diagram illustrating an example of a captured image captured by the digital camera 400. In the example of FIG. 11, the display device 100 is shown in the center of the captured image 401, and the test color patch 101-a is displayed on the screen 101. The captured image 401 also includes the reference object 500.
Thereafter, desired measurement data is acquired by processing the captured image (captured image), and calibration is performed based on the acquired measurement data.
In this embodiment, it is assumed that the color of the reference object is white, but the color of the reference object may not be white. However, the color of the reference object is preferably a color close to white (particularly white).

In this embodiment, the visual environment information acquisition method (second detection process) is different from those in the first and second embodiments. In this embodiment, the color (photographing color) of the reference object 500 is acquired as visual environment information. Specifically, the second predetermined pattern indicating the area of the reference object 500 is drawn on the reference object 500, and the area indicated by the second predetermined pattern is the area of the reference object 500 in the second detection process. Detected as In the example of FIG. 12, patterns 501-b are drawn at the four corners of the area of the screen 101, and an area 401-3 surrounded by a line connecting the patterns 501-b at the four corners is detected as the area of the reference object 500. . Thereafter, the average color (average value of the photographing color) of the detected region of the reference object 500 is acquired as the visual environment information.
Note that the second predetermined pattern is not limited to the four patterns 501-b. For example, as long as the second predetermined pattern indicates the region of the reference object 500, the shape and size thereof are not particularly limited.

  Since the processes other than the process of acquiring the visual environment information are the same as those in the first and second embodiments, the description thereof is omitted.

  As described above, according to the present embodiment, the shooting color of the reference object is acquired as the viewing environment information, and calibration is performed using the shooting color of the reference object as the reference white color. Thereby, when highly accurate calibration cannot be performed by the methods of the first and second embodiments, it is possible to perform calibration with higher accuracy than those of the first and second embodiments.

  In the first to third embodiments, the example in which CIECAM02 is used as the color model has been described. However, the color model is not limited to CIECAM02. As long as the color model incorporates human visual characteristics that adapt to the visual environment, processing according to any color model may be performed.

  In the first to third embodiments, the example in which the second color that is the visual environment information is used as the reference white color is described. However, the method of using the visual environment information is not limited to this. The visual environment information may be used in any way as long as the target color can be determined based on the visual environment information. That is, the target color determination method using the visual environment information is not particularly limited. If visual environment information and display color information are acquired from the captured image, a target color is determined based on the visual environment information, and calibration is performed so that the first color that is the display color information matches the target color, The specific processing method is not particularly limited.

  In the first to third embodiments, J, C, and h are used as relative color attributes in consideration of chromatic adaptation, but the attributes are not limited thereto. Further, the predetermined condition may be any condition as long as it represents a color appearance.

In the first to third embodiments, the reference image (test color patch) is displayed and the color of the reference image is acquired as display color information. However, the method of acquiring display color information is not limited to this. For example, an arbitrary image may be displayed without displaying the reference image. Then, any color of the image may be acquired as display color information. In that case, one of a plurality of predetermined conditions (condition corresponding to the pixel value of the arbitrary image) is selected according to the pixel value (default pixel value) of the arbitrary image, and the selected condition May be used.

  In the first to third embodiments, the display color information and the visual environment information are acquired by the same process. However, the display color information acquisition method and the visual environment information acquisition method may be different from each other. . For example, one of the display color information and the visual environment information may be acquired based on the detection result of the region by the image recognition process, and the other of the display color information and the visual environment information may be acquired according to a user operation.

  In the third embodiment, the example in which the average color of the reference object region is acquired as the viewing environment information (second color) has been described. However, the viewing environment information is not limited to this. For example, the visual environment information may be the shooting color most contained in the reference object region, or may be an intermediate color of the reference object region (an intermediate value of the shooting color included in the reference object region). .

  In the third embodiment, the example in which the region indicated by the second predetermined pattern is detected as the reference object region has been described. However, the method of detecting the reference object region is not limited to this. For example, the shape of the reference object may be recorded in advance in the calibration apparatus, and an object region having a shape that matches the shape of the reference object may be detected as the reference object region.

  In the third embodiment, the example in which the area of the reference object is detected by the image recognition process has been described. However, the image recognition process may not be performed. For example, the photographed image may be displayed on the screen, and the user may specify the reference object region shown in the photographed image. When the relative positional relationship between the reference object and the digital camera is constant, the reference object region can be determined in advance.

  In the third embodiment, the example in which the visual environment information is acquired based on the detection result of the reference object region has been described. However, the method of acquiring the visual environment information is not limited to this. For example, a captured image may be displayed on the screen, and the position of the reference object may be designated by the user as a position for acquiring visual environment information. In addition, when the relative positional relationship between the reference object and the digital camera is constant, the position where the visual environment information is acquired can be determined in advance.

<Other examples>
The present invention can also be implemented by a system (or a device such as a CPU or MPU) of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device. The present invention can also be implemented by a method comprising steps executed by a computer of a system or apparatus that implements the functions of the above-described embodiments by reading and executing a program recorded in a storage device, for example. . For this purpose, the program is stored in the computer from, for example, various types of recording media that can serve as the storage device (ie, computer-readable recording media that holds data non-temporarily). Provided to. Therefore, the computer (including devices such as CPU and MPU), the method, the program (including program code and program product), and the computer-readable recording medium that holds the program non-temporarily are all present. It is included in the category of the invention.

2 data correction unit 5 area determination unit 6 target color determination unit 7 comparison unit 8 correction value determination unit 9 correction value storage unit

Claims (14)

A correction method for correcting a display image displayed in a display area ,
In a state in which the display image is displayed on the display area, an image acquisition step of acquiring a captured image region is photographed including a periphery of the display area and the display area,
From the captured image, a first color is an inner color of the display region, a color acquiring the second color, which is the color of the surrounding of the display region,
A determining step of determining a target color of the first color based on the second color;
A correction step of correcting each pixel value of the display image by a difference between a pixel value indicating the first color and a pixel value indicating the target color;
I have a,
In the determining step, the second color is used as a reference white color, and the target color is determined so that a color appearance when the display image is viewed under the reference white color satisfies a predetermined condition. A correction method characterized by: The correction method according to claim 1, wherein, in the determining step, a color in which a change in appearance of the color of the display image due to the change in the second color is suppressed is determined as the target color. Wherein the predetermined condition, the correction method according to claim 1 or 2, characterized by being represented by relative color attribute in consideration of chromatic adaptation. In the image acquisition step, a captured image captured in a state where a reference image having a first predetermined color is displayed in the display area is acquired;
Wherein the color acquisition step, the correction method according to any one of claims 1 to 3, characterized in that to obtain the color of the reference image as the first color. In the image acquisition step, a captured image captured in a state where a reference object having a second predetermined color is placed around the display area is acquired;
In the color acquisition step, the correction method according to any one of claims 1 to 4, characterized in that to obtain the color of the reference object as the second color. A first detection step of detecting the display area from the area of the captured image by performing image recognition processing for detecting a pattern from the image;
In the color acquisition step, the correction method according to any one of claims 1 to 5, characterized in that to obtain the inner color of the detected in the first detection step region as the first color. In the image acquisition step to acquire the captured image a first predetermined pattern indicating the display region is captured in a state of being displayed in the display area,
The correction method according to claim 6 , wherein in the first detection step, an area indicated by the first predetermined pattern is detected as the display area . A second detection step of detecting a region around the display region from the region of the captured image by performing image recognition processing for detecting a pattern from the image;
In the color acquisition step, the correction method according to any one of claims 1 to 7, characterized in that to obtain the inner color of the second detected in the detection step region as the second color. There is a frame member surrounding the display area ,
The correction method according to claim 8 , wherein in the second detection step, an area of the frame member is detected from the captured image, and an area outside the area of the frame member is detected. In the image acquisition step, a captured image captured in a state where a reference object having a second predetermined color is placed around the display area is acquired;
A second predetermined pattern indicating a region of the reference object is drawn on the reference object,
The correction method according to claim 8 , wherein in the second detection step, a region indicated by the second predetermined pattern is detected. Wherein the correction step, the correction method according to any one of claims 1 to 10, characterized in that for outputting a display image after correction in Viewing device. Wherein the correction step, claim 1-11, characterized in that said first color correction value for correcting the display image to match the target color is stored in the storage unit The correction method according to Item 1. A correction device for correcting a display image displayed in a display area ,
In a state in which the display image is displayed on the display area, an image obtaining unit for obtaining a captured image region including the periphery of the display region and the display region is captured,
From the captured image, a first color is an inner color of the display region, a color acquisition means for acquiring the second color, which is the color of the surrounding of the display region,
Determining means for determining a target color of the first color based on the second color;
Correction means for correcting each pixel value of the display image by a difference between a pixel value indicating the first color and a pixel value indicating the target color;
I have a,
The determination unit uses the second color as a reference white color and determines the target color so that a color appearance when the display image is viewed under the reference white color satisfies a predetermined condition. A correction device characterized by: Program for executing the steps of the correction method according to the computer in any one of claims 1 to 12.

Images