JP2010272934A - Color balance adjustment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color balance adjustment device which appropriately corrects and adjusts R, G, B values of pixels photographed by an imaging apparatus through a front glass or an optical filter, etc. <P>SOLUTION: The color balance adjustment device 1 is provided with: a color temperature calculation means 2 which calculates a color temperature index value T<SP>*</SP>for every pixel, based on the R, G, B values of respective pixels of an image input from the imaging device 10; a discrimination means 3 which determines whether each pixel is a colorless pixel or a chromatic color pixel, based on the R, G, B values of each pixel; and an adjustment means 4 which calculates correction values for the R, G, B values based on the color temperature index value T<SP>*</SP>by using the relation according to whether each pixel is the colorless pixel or the chromatic color pixel following relation between the color temperature index value T<SP>*</SP>established beforehand in mutually different mode for the colorless pixel and the chromatic color pixel, and correction values, and makes adjustment of the R, G, B values for every pixel, following the correction values. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a color balance adjustment device, and more particularly, to a color balance adjustment device that adjusts R, G, and B primary color signal values of each pixel in an image captured by an imaging device.

  2. Description of the Related Art Conventionally, in an imaging apparatus that electrically captures an image using an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), normally, white captured under a certain light source has no color bias. A process of adjusting the balance of the primary color signals of R (red), G (green), and B (blue) so that an image is captured in white, that is, a white balance adjustment process is performed.

  At that time, the color imaged by each pixel of the imaging device is expressed as a color temperature using the temperature of the black body corresponding to the color of light emitted from the black body (complete radiator) at a certain temperature. It is well known that In general, the R, G, and B values of the pixels that image white are shown in the black body radiation locus, that is, the distribution on the chromaticity diagram of the light emitted from the black body at each color temperature. , B values are calculated, and R, G, and B values are adjusted for each pixel based on the correction amounts.

  Further, in Patent Document 1, photometric processing is performed to calculate chromaticity coordinates and the like from the spectral energy distribution of light dispersed for each wavelength by the prism diffraction grating, and the deviation of the chromaticity coordinates from the black body radiation locus is allowed. It has been proposed to adjust the white balance based on the color temperature when it is within the range.

  Further, in Patent Document 2, the values of R, G, and B are once converted into tristimulus values X, Y, and Z in the CIE (1931) XYZ color system defined by the International Lighting Commission, and color conversion is performed. It has been proposed to perform white balance adjustment processing by returning the color-converted X, Y, and Z to the values of R, G, and B again.

  On the other hand, in the process of adjusting the R, G, and B values of the pixels that image chromatic colors such as red, green, and blue other than white, gray, and black, that is, the color balance adjustment process, the white balance as described above is usually used. In many cases, the R, G, and B values are adjusted by directly applying the correction amount in the adjustment process to the chromatic color.

JP 2006-54678 A Japanese Patent No. 3105633

  By the way, in these conventional white balance adjustment processing and color balance adjustment processing, the R, G, and B sensitivities specific to the imaging apparatus are adjusted in advance, and the balance of R, G, and B is almost uniform. Is the premise. Therefore, it has been possible to calculate the correction amount in consideration of only the color temperature.

  However, if the image pickup device is equipped with an optical filter such as an infrared cut filter or a polarization filter, or if the image pickup device is attached to the interior of the vehicle and the front of the vehicle is imaged through a windshield or the like, it is unique to the image pickup device. Even if the R, G, and B sensitivities are adjusted in advance, the balance of R, G, and B is lost when, for example, a white object is imaged as a subject due to the influence of an optical filter, windshield, etc. There is.

  Therefore, as in the conventional color balance adjustment process described above, when adjusting the R, G, and B values of pixels that have captured chromatic colors such as red, green, and blue, the correction amount in the white balance adjustment process remains unchanged. If applied, the balance of R, G, and B is lost due to the influence of an optical filter, a windshield, etc., and there is a possibility that proper color balance adjustment cannot be performed.

  However, even in such a camera system, if an achromatic color such as white or gray and a chromatic color such as red, green, or blue cannot be accurately adjusted and imaged, the subject is based on the image captured thereby. The problem arises that the color of the camera is mistakenly recognized. For example, when an image pickup apparatus is mounted on a vehicle and a signal is detected, there may be a problem that the color of the red signal cannot be recognized as red. Further, for example, when the imaging apparatus is mounted on a robot or the like that autonomously acts, there may arise a problem that the robot or the like erroneously recognizes the color of the subject and cannot accurately recognize the subject.

  In the following, the white balance adjustment for the achromatic color and the color balance adjustment for the chromatic color are collectively expressed as color balance adjustment.

  The present invention has been made in view of such circumstances, and appropriately corrects the R, G, and B values of each pixel of an image captured by an imaging device via a windshield, an optical filter, or the like. It is an object of the present invention to provide a color balance adjusting device that can be adjusted.

In order to solve the above problem, the first invention provides:
In a color balance adjustment device for an image taken by an imaging device,
Color temperature calculation means for calculating a color temperature index value for each pixel based on the R, G, and B values of each pixel of the image input from the imaging device;
Determination means for determining whether each pixel is an achromatic pixel or a chromatic pixel based on the R, G, and B values of each pixel of the image;
According to the relationship between the color temperature index value and the correction amount preset in different manners for the achromatic pixel and the chromatic pixel, each pixel is an achromatic pixel or a chromatic color pixel. The correction amount for the R, G, and B values based on the color temperature index value is calculated using the relationship depending on whether the pixel is a pixel, and the R, G, and B values for each pixel are calculated according to the correction amount. Adjusting means for adjusting; and
It is characterized by providing.

  According to a second aspect of the present invention, in the color balance adjusting device according to the first aspect, the correction amount of the R, G, and B values for the achromatic pixel is a spectral sensitivity of the imaging device under the condition of imaging white. For each color temperature index value among the theoretical values of the R, G, B relative intensities for each color temperature index value when a value obtained by multiplying the characteristic and the relative intensity by black body radiation is integrated in a predetermined wavelength range Further, the color temperature index value is set as the reciprocal of the ratio of the theoretical values calculated based on the theoretical value having the second largest relative intensity.

  According to a third aspect of the present invention, in the color balance adjustment device according to the second aspect of the invention, the adjustment means is a pixel in which R, G, and B values are all equal among the pixels determined as achromatic pixels by the determination means. Is excluded from the adjustment target of the R, G, and B values by the correction amount, and the R, G, and B values are adjusted by the correction amount for the other pixels.

  A fourth invention is the color balance adjustment device according to any one of the first to third inventions, wherein the correction amounts of the R, G, and B values for the chromatic color pixels are determined by spectral sensitivity characteristics of the imaging device. The R, G, and B for each color temperature index value when the values obtained by multiplying the spectral sensitivity characteristics of the imaging device and the relative intensity by black body radiation are integrated in the wavelength range where the sensitivity is high for each of R, G, and B. The correction value for the color temperature calculated by dividing the respective theoretical values of the R, G, B relative intensities at the reference color temperature by the respective theoretical values of the relative intensity of B, and the R for each color temperature index value R calculated as the reciprocal of the ratio of the theoretical values calculated based on the theoretical value having the second largest relative intensity for each color temperature index value among the theoretical values of the relative intensities of G, B, and B Correction for G, B When, characterized in that it is set for each color temperature index value as a value obtained by multiplying the.

  According to a fifth aspect of the present invention, in the color balance adjusting apparatus according to the fourth aspect of the invention, the wavelength ranges of high sensitivity for each of R, G, and B in the spectral sensitivity characteristics of the imaging device are the same wavelength widths for R, G, and B. It is set as a wavelength range of

  According to a sixth aspect of the present invention, in the color balance adjusting device according to the fourth or fifth aspect of the invention, the adjusting means includes the R, G, and B values for the pixels determined to be chromatic pixels by the determining means. Only the largest color component is to be adjusted, and when the difference between the largest color component value and the smallest color component value is equal to or greater than a predetermined first threshold value, the value of the largest color component is set to the largest color component value If the difference is less than or equal to a second threshold set to a value smaller than the predetermined first threshold, the value of the largest color component is not adjusted and the difference is When the value is between the first threshold value and the second threshold value, a value obtained by linearly interpolating the correction amount according to the difference is multiplied by the value of the largest color component, and R, G, B The value of is adjusted.

  According to a seventh invention, in the color balance adjusting device according to any one of the first to sixth inventions, the determination means is based on | R−G | based on the R, G, and B values of each pixel of the image. , | R−B |, | B−G | satisfy the condition that each is equal to or less than a predetermined threshold value, it is determined that the pixel is an achromatic pixel, and in other cases, the pixel is a chromatic color. It is characterized by determining that the pixel is a pixel.

  According to the first invention, after determining whether the pixel is an achromatic pixel or a chromatic pixel based on the R, G, and B values of each pixel of the image captured by the imaging device Therefore, the pixel is an achromatic pixel or a chromatic pixel according to the relationship between the color temperature index value and the correction amount that are preset in different manners for the achromatic pixel and the chromatic pixel. Depending on the above, the above relationship is properly used, that is, for example, the reference table for achromatic color and the table for chromatic color are used separately, and the correction amount for the R, G, B values is calculated based on the color temperature index value. The R, G, and B values for each pixel are adjusted according to the correction amount.

  Therefore, it is possible to appropriately adjust the R, G, and B values of a pixel depending on whether the pixel is a pixel in which an achromatic subject is imaged or a pixel in which a chromatic subject is imaged. Even in a camera system in which a transmission member such as a windshield and a protective plate of a vehicle, an optical filter such as an infrared cut filter or a polarization filter, and the like are interposed in front of the imaging device, R of each pixel of the image captured by the imaging device , G and B can be accurately corrected and adjusted.

  For this reason, even in such a camera system, it is possible to accurately adjust an achromatic color such as white or gray and a chromatic color such as red, green or blue, and based on the captured image. Thus, the color of the subject can be accurately recognized. For example, when an imaging device is mounted on a vehicle, a robot that acts autonomously, or the like to detect a subject, it is possible to accurately detect the subject and accurately detect the subject. .

  According to the second aspect of the invention, the correction amount of the R, G, and B values for the achromatic color pixel is the second relative intensity among the theoretical values of the R, G, and B relative intensity for each color temperature index value. Is set as the reciprocal of the ratio of each theoretical value calculated with a large theoretical value as a reference, the correction amount of the R, G, and B values for the achromatic pixel is the largest theoretical value or the smallest relative value. It is possible to accurately prevent a bias to a specific color component by being dragged by a theoretical value, and it is possible to exhibit the effects of the above-described inventions more accurately.

  According to the third invention, for example, when a white member or the like is imaged without being colored by a transmission member or an optical filter interposed in front of the imaging device, such as a windshield of a vehicle or an infrared cut filter. Since the values of R, G, and B that are output from a pixel that has captured an achromatic subject are the same, the values of R, G, and B that are output from the pixel are all equal. For example, it can be determined that the pixel is an image of an achromatic color such as white or gray, and no adjustment is required.

  Therefore, in addition to the effects of the inventions described above, the adjustment processing of the R, G, and B values can be lightened by excluding pixels whose output values of R, G, and B are all equal from the adjustment target. And the processing can be performed at higher speed.

  According to the fourth aspect of the present invention, according to the relationship between the color temperature index value set in advance in a manner different from the manner for the achromatic color pixel and the correction amount, the chromatic color pixel corresponds to the chromatic color pixel. By adjusting, it is possible to accurately correct and adjust the R, G, and B values of the chromatic color pixels, and the effects of the respective inventions can be exhibited more accurately.

  According to the fifth aspect of the present invention, it is possible to accurately calculate the correction amounts of the R, G, and B values for the chromatic color pixels without being biased toward the specific color component, and the adjustment for the chromatic color pixels can be accurately performed. Can be performed. Therefore, the effects of the above inventions can be more accurately exhibited.

  According to the sixth aspect of the invention, when a specific color component is large among the R, G, and B values of the chromatic color pixel, the color component is adjusted, and the R, G, and B of the chromatic color pixel are adjusted. In the case of a color that does not have a large difference in value and is close to an achromatic color, no adjustment is performed, and in the middle, the correction amount is corrected by linear interpolation or the like. By adjusting the R, G, and B values of the chromatic color pixels in this way, it becomes possible to more accurately adjust the chromatic color pixels, and the effects of the above-described inventions can be exhibited more accurately. It becomes possible.

  According to the seventh aspect of the invention, for example, when a white member or the like is imaged without being colored by a transmission member or an optical filter interposed in front of the imaging device, such as a windshield of a vehicle or an infrared cut filter. The values of R, G, and B that are output from pixels that image an achromatic subject are the same. Therefore, if the pixel is determined to be an achromatic pixel when the condition that each of the values | R−G | is equal to or less than a predetermined threshold is satisfied, the achromatic pixel and the chromatic color can be determined. It is possible to discriminate the pixel accurately and simply, and the effects of the inventions described above can be more accurately exhibited.

It is a block diagram which shows the structure of the color balance adjustment apparatus etc. which concern on this embodiment. It is a figure showing the black-body radiation locus calculated with the model type concerning this embodiment. It is a figure explaining the perpendicular corresponding to the point corresponding to R, G, B of a pixel, and the black body radiation locus drawn from the point. It is a figure showing each theoretical value of the relative intensity of R, G, B depending on the color temperature calculated by the model formula concerning this embodiment, when white is imaged. It is a figure showing the ratio with respect to the theoretical value with the 2nd largest relative intensity of each theoretical value calculated based on each theoretical value of FIG. It is a figure showing a part of each correction amount of the value of R, G, B with respect to the achromatic pixel calculated from the ratio of each theoretical value of FIG. It is a figure showing the spectral sensitivity characteristic etc. with respect to the wavelength of an imaging device containing a windshield etc. It is a figure showing each theoretical value of the relative intensity of R, G, and B depending on the color temperature calculated by the model formula concerning this embodiment using Input (lambda) set about R. It is a figure which represents together each theoretical value of the relative intensity of R, G, and B respectively calculated by the model formula concerning this embodiment using each Input (lambda). FIG. 10 is a diagram illustrating a part of correction amounts of R, G, and B values for chromatic pixels calculated from the theoretical values and the like of FIG. 9.

  Embodiments of a color balance adjusting device according to the present invention will be described below with reference to the drawings.

  In the following, the case where the color balance adjusting device 1 and the imaging device 10 are mounted on a vehicle will be described. However, the present invention is not limited to this, and for example, a camera mounted on a robot that acts autonomously, etc. It can be used for color balance adjustment of an image picked up by.

  The color balance adjusting apparatus 1 according to the present embodiment is configured by a computer in which a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, and the like are connected to a bus. As shown in FIG. 1, a color temperature calculation unit 2, a determination unit 3, and an adjustment unit 4 are provided.

  In addition, the color balance adjustment device 1 is configured to adjust the color balance of R (red), G (green), and B (blue) of each pixel of an image captured by the imaging device 10. Hereinafter, before describing the units 2 to 4 of the color balance adjusting device 1, the imaging device 10 and the like will be described.

  In this embodiment, the imaging apparatus 10 is a monocular imaging apparatus such as a camera in which an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is incorporated. It is also possible to configure so that the processing according to the present invention is performed on one or a plurality of images captured by one or a plurality of imaging devices.

  Although illustration is omitted, in the present embodiment, the imaging device 10 is installed, for example, in the vicinity of a rearview mirror inside the windshield of the vehicle, images the front of the vehicle, and lanes marked on the road surface (passing prohibited) A continuous line or a broken line marked on a road surface such as a lane marking that divides a line or a roadside zone and a roadway), vehicles such as preceding vehicles, pedestrians, signals, and the like are imaged.

  Further, the imaging device 10 is provided with an imaging lens including a focus lens and a zoom lens (not shown), an aperture, a shutter, and the like, and an optical filter such as an infrared cut filter or a polarization filter is mounted as necessary. Has been. Further, the imaging device 10 captures an image at a certain sampling period, and the image is photoelectrically converted into light of each color of R (red), G (green), and B (blue) by an image sensor such as a CCD. Thus, R, G, and B analog values for each pixel are output.

  The conversion unit 11 is configured by an A / D converter or the like, and when R, G, and B analog values for each pixel are input from the imaging device 10, the R, G, and B analog values are converted into digital values, respectively. The image is converted to and output to the image correction unit 12. The image correction unit 12 performs image correction such as deviation, noise removal, luminance correction, and the like on the transmitted analog values of R, G, and B, and R, G, and B for each of the corrected pixels. Is output to the color balance adjusting apparatus 1.

The color temperature calculation unit 2 of the color balance adjustment device 1 calculates the color temperature index value T ^* for each pixel based on the R, G, and B values of each pixel of the image input from the imaging device 10. It has become.

Hereinafter, first, a model formula, a theoretical value, and a chromaticity diagram used for calculating the color temperature index value T ^* based on the values of R, G, and B by the color temperature calculation unit 2 will be described. In this embodiment, the color temperature calculation unit 2 calculates the color temperature index value from the actual R, G, and B values of each pixel based on the chromaticity diagram obtained from the model formula and the theoretical value, as will be described later. T ^* is calculated. This model formula is well known.

First, the following equation (1) is the theory of the relative intensities of R, G, and B output from the imaging device 10 when imaging is performed by the imaging device 10 such as a CCD camera via a vehicle windshield or the like. This is a model formula for calculating values (model values) I _R , I _G and I _B.

  Here, Ω represents an integration range for the wavelength λ, and is integrated in the wavelength region including the visible light region. For example, when an infrared cut filter that cuts off transmission of infrared light having a wavelength of 750 nm or more is used, integration is performed in a wavelength range of 750 nm or less. Ftglass (λ) is a function representing the transmission characteristics of the windshield of the vehicle on which the imaging device 10 is mounted, and OPTfilter (λ) is a function representing the transmission characteristics of an optical filter such as an infrared cut filter.

[R (λ), g (λ), b (λ)] are functions for R, G, and B representing spectral sensitivity characteristics of a CCD image sensor or the like used in the imaging apparatus 10, and M (λ) represented by the equation (2) is an equation representing the relative intensity due to black body radiation. C ₁ and C ₂ in the above formula (2) are respectively
C ₁ = 3.7418 × 10 ⁻¹⁶ [Wm ² ]
C ₂ = 1.4388 × 10 ⁻² [mK]
T represents the color temperature [K].

Input (λ) is a function that represents the spectral characteristics of incident light. When the incident light is white, Input (λ) is a function that gives 1 to all wavelengths λ. Is a chromatic color of each color such as red, green, and blue, a function having a characteristic for each wavelength region is used. Then, by appropriately changing Input (λ) for each color, the theoretical value I of the relative intensities of R, G, and B output from the imaging device 10 when light of each color enters each pixel of the imaging device 10. _{R 1} , I _G , and I _B are calculated according to the above equation (1).

  In the present invention, an achromatic color means a color having only a so-called lightness such as white, gray (gray), black, etc., and a chromatic color means a so-called color such as red, green, or blue. A color that has lightness, hue, and saturation. In addition, the model expression expressed by the above expression (1) is as follows. The transmission characteristic Ftglass (λ) of the vehicle windshield, the transmission characteristic OPTfilter (λ) of the optical filter attached to the camera lens, and the CCD image sensor. The spectral sensitivity characteristics [r (λ), g (λ), b (λ)] such as the above are advantageous in that each characteristic unique to the camera system can be reflected.

Here, a function when white is imaged, that is, Input (λ) = 1, is substituted for the input (λ) of the model expression expressed by the above formula (1), and the calculated theoretical value I _R , I _G, chromaticities from _{I B I B / I R,} calculates the _I B / I _G. Then, when plotting on a chromaticity diagram with chromaticity I _B / I _{R on} the horizontal axis and chromaticity I _B / I _G on the vertical axis, the black body radiation locus in the camera system as described above is, for example, FIG. As shown, the color temperature T is obtained as a parameter.

In the present embodiment, the color temperature calculation unit 2 calculates the color temperature index value T ^* from the R, G, and B values of each pixel of the actually captured image based on the chromaticity diagram illustrated in FIG. It comes to calculate. The chromaticity diagram is calculated in advance, and a table corresponding to the chromaticity diagram is stored in advance in a storage unit such as a ROM of the color balance adjusting apparatus 1.

Chromaticity R, G, which is the ratio from _{B / R ≒ I B / I} R of _{B, B / G ≒ I B} / I G holds. Therefore, the color temperature calculation means 2 reads the chromaticity diagram shown in FIG. 2 from the ROM or the like, calculates the values of B / R and B / G from the R, G, and B values of each pixel of the image, Plot on the degree diagram (see black circle in FIG. 3).

  If the plotted point is on the black body radiation locus, the color temperature T at that point can be estimated as the color temperature T of the pixel. In addition, as shown in FIG. 3, when the plotted point is plotted at a position away from the black body radiation locus, a perpendicular line is drawn from the plotted point to the black body radiation locus, The color temperature T at the intersection with the perpendicular can be estimated as the color temperature T of the pixel.

In the present embodiment, the color temperature calculation unit 2 calculates the color temperature T estimated in this way as the color temperature index value T ^* for the pixel. Further, the color temperature calculation unit 2 calculates the color temperature index value T ^* for each pixel of the image.

  The determination unit 3 determines whether each pixel is an achromatic pixel or a chromatic pixel based on the R, G, and B values of each pixel of the image.

Specifically, in this embodiment, the determination unit 3 determines that the pixel is an achromatic pixel when the R, G, and B values of the pixel satisfy the following expressions (3) to (5) at the same time. In other cases, that is, when the R, G, and B values of a pixel do not satisfy any one of the following formulas (3) to (5), it is determined that the pixel is a chromatic pixel It is supposed to be.
| RG | ≦ Tha (3)
| R−B | ≦ Thb (4)
| BG | ≦ Thc (5)

  The threshold values Tha, Thb, and Thc in the above expressions (3) to (5) may be the same value or different values. In the present embodiment, when the R, G, and B values of the pixels are digital values of 256 gradations, for example, 0 to 255, the thresholds Tha to Thc are set to 20, for example.

  The conditions for determining that the pixel is a chromatic pixel are the transmission characteristics of a transmission member that transmits light, such as a windshield and a protective plate, the transmission characteristics of an optical filter to be mounted, and a CCD image sensor. These are set as appropriate according to the characteristics unique to the camera system such as the spectral sensitivity characteristics of the imaging apparatus 10.

The adjustment unit 4 calculates a correction amount for correcting the R, G, and B values of the pixel based on the color temperature index value T ^* for each pixel calculated by the color temperature calculation unit 2, and the R The R, G, and B values are adjusted for each pixel in accordance with the correction amount of the, G, and B values.

In this case, in the present invention, the relationship between the color temperature index value T ^* and the correction amount is set in advance depending on whether each pixel is an achromatic pixel or a chromatic pixel, The adjusting means 4 uses the above relationship to be used depending on whether each pixel is an achromatic pixel or a chromatic pixel, and refers to each achromatic or chromatic color table to be described later. Is calculated.

First, the relationship between the color temperature index value T ^* and the correction amount in the case where the pixel color is an achromatic color, that is, a color having only lightness such as white, gray, and black, is expressed by the above equation (1). In the model equation represented, the value is set in advance based on theoretical values I _R , I _G , and I _B calculated by substituting Input (λ) = 1 when imaging white.

That is, when the theoretical values I _R , I _G , and I _B of _R , _G , and _B are calculated by substituting Input (λ) = 1 into the above equation (1), it is expressed by the above equation (2). Since M (λ) representing the relative intensity of blackbody radiation depends on the color temperature T, the theoretical values I _R , I _G , and I _B are also calculated as values that depend on the color temperature T, as shown in FIG. . Then, since the color of the pixel is achromatic white and the like are required to be _{I R = I G = I B} . Therefore, correction amounts C _R , C _G , and C _B are calculated for each color temperature T (that is, each color temperature index value T ^* ) so that the theoretical values I _R , I _G , and I _B are aligned. Yes.

At this time, in this embodiment, in consideration of preventing a bias toward a specific color component (that is, R, G, or B), among the theoretical values I _R , I _G , and I _B at each color temperature T, strength is calculated each theoretical value I _R based on the large theoretical _second, I _G, the reciprocal of the ratio of I _B for each color temperature T, R of the reciprocal for the pixel of the achromatic, G, and B values The correction amounts C _R , C _G , and C _B are calculated and set in advance.

Specifically, when the theoretical values I _R , I _G , and I _B calculated by substituting Input (λ) = 1 into the above equation (1) depend on the color temperature T as shown in FIG. If the relative intensity is set to 1, based on the large theoretical the second at each color temperature T, the theoretical values _{I R, I G,} the ratio _r R of _{I B, r G,} r _B each, as shown in FIG. 5 the color Calculated for each temperature T.

The reciprocals of the ratios r _R , r _G , r _B of the theoretical values I _R , I _G , I _B calculated in this way are correction amounts C _R , C _G , C for the values of R, G, B. _B is calculated for each color temperature T as shown in FIG. In consideration of the 6 visibility, as the correction amount _{C R,} C G, although _{C B} not only indicated by a range of color temperatures 3500K～8000K, shown in FIGS. 2 to 5, each theory _{I R, I G,} the correction amount when it is calculated in the range of _{I B} for example color temperature _{2000K~12500K C R, C G, C} B is calculated at the entire range.

In the present embodiment, the correction amounts C _R , C _G , and C _B of the R, G, and B values for the achromatic color pixel calculated for each color temperature T (that is, each color temperature index value T ^* ) in this way. A table (that is, an achromatic color table) is stored in advance in storage means such as a ROM of the color balance adjusting apparatus 1.

When the adjusting unit 4 determines that a certain pixel is an achromatic pixel and the color temperature calculating unit 2 calculates that the color temperature index value of the pixel is T ^* , a table for achromatic color is obtained. The correction amounts C _R , C _G , and C _B for the color temperature index value T ^* are calculated with reference, and the R, G, and B values of the pixel are multiplied by the correction amounts C _R , C _G , and C _B , respectively. The R, G, and B values for each pixel are adjusted.

The correction amount C _R to the table for the achromatic referenced in the color temperature index value T _^*, C _G, if the C _B not associated, for example, in the vicinity of the color temperature index value T ^* color Correction amounts C _R , C _G , and C _{B at the} color temperature index value T ^* are calculated from the correction amounts C _R , C _G , and C _B at the temperature T by linear interpolation or the like.

  Further, as in this embodiment, when the transmissive member is a windshield of a vehicle, and an infrared cut filter or a polarization filter that hardly affects the visible light region is used as an optical filter, that is, so-called white When an image is captured without being colored in a specific color, the values of R, G, and B output from the pixel that captured white are the same value. Therefore, if the values of R, G, and B output from a pixel are all equal, it can be determined that the pixel is an image of an achromatic color such as white or gray.

Therefore, in order to lighten the adjustment processing of the R, G, and B values, the adjustment unit 4 is a pixel in which all of the R, G, and B values are equal among the pixels that are determined to be achromatic pixels by the determination unit 3. the correction amount C _R as described _above, C _G, by C _B R, G, and excluded from the adjustment of the value of B, the correction amount C _R for determining pixel other achromatic pixels _and, C _G, it is possible to configure to perform R by C _B, G, the adjustment of the value of B.

On the other hand, when the pixel is a chromatic pixel, the relationship between the color temperature index value T ^* (color temperature T) and the correction amount (that is, the chromatic color table) is the color when the pixel is an achromatic color. The relationship between the temperature index value T ^* (color temperature T) and the correction amount (that is, the achromatic color table) is preset in a different manner.

In general, in the color balance adjustment when the pixel color is a chromatic color, that is, a color having lightness, hue, and saturation, such as red, green, and blue, it is expressed by the above equation (1). Based on the theoretical values I _R , I _G , I _B calculated by setting a predetermined function as Input (λ) of the model formula and executing the integration of the formula (1) under the Input (λ) Thus, the R, G, and B values of the pixel are adjusted.

  However, in practice, it is not always easy to set an appropriate input (λ). Therefore, in the present embodiment, Input (λ) set corresponding to R, G, and B is set in a simple form.

  Here, in order to investigate the spectral sensitivity characteristics of R, G, and B for each wavelength λ in the camera system of the imaging apparatus 10 such as an actual windshield, an optical filter, and a CCD image sensor. When calculation is performed using the following equation (6), for example, spectral sensitivity characteristics with respect to wavelength λ of R (λ), G (λ), and B (λ) as shown in FIG. 7 are obtained.

  In this embodiment, as described above, an infrared cut filter that cuts off transmission of infrared light of 750 nm or more is used, and light having a wavelength of 750 nm or more is also cut in the spectral sensitivity characteristics of FIG. ing. Looking at the spectral sensitivity characteristics of FIG. 7, R (λ), G (λ), and B (λ) each have a sensitivity peak, and the base spreads from there to the long wavelength side and the short wavelength side. R (λ) is distributed in the long wavelength region, G (λ) is distributed in the medium wavelength region, and B (λ) is distributed in three in the short wavelength region.

  Therefore, in this embodiment, wavelength ranges with high sensitivity are set for R (λ), G (λ), and B (λ). In that case, it sets so that it may divide into the wavelength range of the same wavelength width. In the example of FIG. 7, for example, R (λ) is divided into wavelength ranges of 560 to 750 nm, G (λ) of 465 to 655 nm, and B (λ) of 370 to 560 nm and a wavelength width of 190 nm.

Then, Input (λ) is set as shown in the following equations (7) to (9) corresponding to the wavelength ranges of R (λ), G (λ), and B (λ).
R: Input (λ) = 1 (560 nm ≦ λ ≦ 750 nm)
= 0 (wavelength λ other than the above) (7)
G: Input (λ) = 1 (465 nm ≦ λ ≦ 655 nm)
= 0 (wavelength λ other than above) (8)
B: Input (λ) = 1 (370 nm ≦ λ ≦ 560 nm)
= 0 (wavelength λ other than above) (9)

  That is, each input (λ) is set to 1 in the above-described wavelength ranges set for R, G, and B, and is set to 0 in other wavelength ranges, that is, a so-called rectangular function.

Subsequently, when integration is performed by substituting these Input (λ) into the above equation (1), for example, when calculation is performed using Input (λ) for R, M representing the relative intensity of blackbody radiation. Due to the fact that (λ) depends on the color temperature T as expressed by the above equation (2), the theoretical values I _R , I _G , and I _B depending on the color temperature T as shown in FIG. Calculated. However, FIG. 8 shows the calculation result using Input (λ) for _{R, and} only the theoretical value IR has significant information.

Further, calculation is performed using Input (λ) for G and B, respectively, and similarly, theoretical values I _G and I _B having significant information are calculated. When the theoretical values I _R , I _G , and I _B depending on the color temperatures T calculated using the respective inputs (λ) for _R , _G , and _B are expressed together, they are expressed as shown in the graph of FIG. be able to.

In the present embodiment, correction is performed when the pixel color is an achromatic color using the theoretical values I _R , I _G , and I _B of the relative intensities of R, G, and B for each color temperature T shown in FIG. the amount _{C R,} C G, in the same manner as the calculation of _{C B,} so R when the color of the pixel is chromatic, G, the correction amount _C R to the value of _B, C G, the _{C B} is calculated ing.

Ie, R for each color temperature T calculated as shown in FIG. 9, G, the theoretical value I _R of _B, I _G, among the I _B, the theoretical relative intensity the second largest for each color temperature T The ratio of each theoretical value I _R , I _G , I _B is calculated as a reference, and the correction amount C _R for the R, G, B of the pixel is calculated as the reciprocal of the calculated ratio of each theoretical value I _R , I _G , I _B. C _G and C _B are calculated.

In the present embodiment, when the pixel color is a chromatic color, correction amounts C ^* _R , C ^* _G , and C ^* _B for the color temperature are further calculated.

When the pixel color is chromatic, for example, when the image is captured darkly, such as when it is cloudy, rainy, or shaded, the pixel color is also captured darkly, and what color the pixel color is It becomes difficult to recognize if there is. The correction amounts C ^* _R , C ^* _G , and C ^* _{B with} respect to the color temperature are correction amounts for conversion so that the color of the pixel can be accurately recognized even in such a situation, and the color temperature T (color temperature) the values of R and G and B pixels in the index value ^{T *),} _R 5500K in the state of the reference color temperature, ie 5500K corresponds to white in fine _weather, G _5500K, to convert to approximate the value of _{B 5500K} Is the amount of correction.

That is, the correction amounts C ^* _R , C ^* _G , and C ^* _B for the color temperature are respectively
_{^{C * R = I R5500K / I}} R (T *) ... (10)
_{^{C * G = I G5500K / I}} G (T *) ... (11)
_{^{C * B = I B5500K / I}} B (T *) ... (12)
Is calculated by Note that I _{R5500K and the} like and I _R (T ^* ) and the like are values when the color temperature T in each theoretical value I _{R and the} like calculated as shown in FIG. 9 is ₅₅₀₀ K and T ^* .

In the present embodiment, the correction amounts C, R, G, and B when the pixel color is chromatic are used as the correction amounts of the R, G, and B values of the pixel when the pixel color is chromatic. C _R C ^* _R , C _G C ^* _G , C _B C ^* _{B obtained} by multiplying _{R 1} , C _G , C _B and correction amounts C ^* _R , C ^* _G , C ^* _B for color temperature are used. It has become.

In the case of the example shown in FIG. 9, the correction amounts C _R C ^* _R , C _G C ^* _G , and C _B C ^* _B of the values of R, G, and B are calculated for each color temperature T as shown in FIG. Is done. Also in FIG. 10, in consideration of viewability, as the correction amount _C R ^C _{* R} and the like not only indicated by a range of color temperatures 3500K～8000K, shown in FIGS. 8 and 9, each theory _{I R, I G,} the correction amount _C R ^C _{* R,} etc. if computed in the range of _{I B} for example color temperatures 2000K~12500K also calculated in their full scope.

The characteristic of the correction amount C _R C ^* _{R with} respect to the color temperature T is that the correction amount C ^* _{R with} respect to the color temperature is compared with the correction amount _CR or the like when the pixel color is achromatic (see FIG. 6). The characteristic curve is curved by the amount multiplied by the same.

In the present embodiment, correction amounts C _R C ^* _R and C _G of R, G, and B values for chromatic pixels calculated for each color temperature T (that is, each color temperature index value T ^* ) as described above. A table of C ^* _G and C _B C ^* _B (that is, a chromatic color table) is stored in advance in storage means such as a ROM of the color balance adjusting apparatus 1.

  Further, in this embodiment, when the adjustment unit 4 determines that a certain pixel is a chromatic color pixel, unlike the case of an achromatic color pixel, the adjustment unit 4 determines that the pixel is a chromatic color pixel. Among the values of R, G, and B, only the largest color component is to be adjusted, and the second largest color component or the smallest color component is not adjusted.

  Hereinafter, a case will be described in which the largest color component is R (that is, R> G and R> B) and B is the smallest color component among the R, G, and B values of the pixel. The same applies when the other color components are maximum or minimum.

  First, according to the difference between the largest color component R and the smallest color component B, the adjustment method is divided into three cases.

[Adjustment 1] When R−B calculated from the R and B values of a pixel is equal to or greater than a first threshold value Th1 set to a large value in advance (ie, R−B ≧ Th1), the pixel is reddish. The adjustment means 4 refers to the chromatic color table, and the R temperature correction amount C _R C ^* _{R when} the color temperature index value of the pixel calculated by the color temperature calculation means 2 is T ^* . Is calculated by multiplying the _R value of the pixel by the correction amount C RC ^* _R to correct the R value.

Note that the first threshold Th1 is set to 100 or the like, for example, when the R, G, and B values of the pixels are digital values of 256 gradations from 0 to 255. Further, when the table for the referenced chromatic correction amount C _R C ^* _R in the color temperature index value T ^* is not associated with, for example, in the color temperature T in the vicinity of the color temperature index value T ^* by linear interpolation or the like from the correction amount _C R ^C _{* R} calculates a correction amount _C R ^C _{* R} in the color temperature index value ^{T *.}

[Adjustment 2] When R−B calculated from the R and B values of a pixel is equal to or smaller than a second threshold value Th2 set to a small value in advance (ie, R−B ≦ Th2), the pixel is not present. In this case, the adjustment unit 4 does not correct the color component R having the largest value. That is, in this case, the correction amount is set to 1 rather than _{^C R C *} R.

If the difference between the largest color component R and the smallest color component B is, for example, 20 or less, the difference between the largest color component R and the second largest color component G, or the smallest value with the second largest color component G. The difference from the color component B is also 20 or less. Therefore, in this embodiment, in order to satisfy the above equations (3) to (5) in such a case, the pixel is determined to be an achromatic pixel by the determination unit 3 as described above, and the adjustment unit 4 adjusts the R, G, and B values of the pixel using the correction amounts C _R , C _G , and C _B of the R, G, and B values for the achromatic pixel.

  On the other hand, in the adjustment 2, the adjustment unit 4 does not correct the color component R having the largest value, and does not adjust the color component G having the second largest value or the color component B having the smallest value. . For this reason, in the present embodiment, a so-called dead zone is provided in a pixel band in which the difference between the largest color component R and the smallest color component B is greater than 20 and less than or equal to the second threshold Th2. ing.

  Therefore, the value of the second threshold Th2 is appropriately set according to how much pixel range such a dead zone is provided. That is, when the dead zone is set to a certain extent, the second threshold Th2 is set to a value such as 25 or 30, for example, and when the dead zone is not provided, the second threshold Th2 is set to 20 similarly to the above thresholds Tha to Thc. Set to In the latter case, there is no room for the above adjustment 2 after all.

[Adjustment 3] When RB calculated from the R and B values of the pixel is larger than the second threshold Th2 and smaller than the first threshold Th1 (that is, Th2 <RB <Th1), that is, the above adjustment. in the case of intermediate 1 and adjustment 2, the adjustment means 4, depending on the size of the R-B, linear interpolation and correction amount 1 in the correction amount C _R C ^* _R and adjustment 2 in the adjustment 1 above Then, the correction amount C ^** _R is calculated, and the R value of the pixel is multiplied by the calculated correction amount C ^** _R to correct the R value and make an adjustment.

In this case, the correction amount C ^** _R is calculated by linear interpolation.
_{^{C ** R = 1 + (C}} R C * R -1) × (R-B) / (Th1-Th2) ... (13)
Can be calculated by calculating. Also in this case, the correction amount at the color temperature index value T ^* C _R C ^* if _R has not associated with the correction amount by linear interpolation or the like C _R C ^* _R is calculated in the table for the referenced chromatic The

  Next, the operation of the color balance adjusting apparatus 1 according to this embodiment will be described.

  In the conventional color balance adjustment described above, the white balance adjustment process is performed on an image pickup apparatus that has been adjusted in advance so that the R, G, and B sensitivities unique to the image pickup apparatus are matched, and the balance of R, G, and B is substantially uniform. By applying the correction amount to the chromatic color as it is, the values of R, G, and B of the pixel can be adjusted.

However, as in this embodiment, incident light is incident on the imaging device 10 such as a CCD image sensor via a transmission member such as a windshield or a protective plate of a vehicle, or an optical filter such as an infrared cut filter or a polarization filter. In the case of the camera system to be used, even if the R, G, B sensitivity inherent to the imaging apparatus 10 is adjusted in advance, the correction amount in the white balance adjustment process, that is, R, G, B for achromatic pixels It is not always possible to adjust the R, G, and B values of the pixels accurately by applying the correction amounts C _R , C _G , and C _B to the chromatic colors as they are.

Therefore, in the present embodiment, as described above, the determination unit 3 determines whether the pixel is an achromatic pixel or a chromatic pixel based on the R, G, and B values of the pixel. The relationship between the color temperature index value T ^* preset in a different manner for the achromatic color pixel and the chromatic color pixel and the correction amount, that is, the achromatic color table and the chromatic color table described above, The values of R, G, and B are adjusted by using properly.

  As described above, in this embodiment, the pixel is determined according to the determination conditions of the above formulas (3) to (5) as a reference for determining whether the pixel is an achromatic color or a chromatic color. This is based on the fact that the transmission characteristics of the windshield of a vehicle and the transmission characteristics of an optical filter such as an infrared cut filter cause the original color of the subject to reach the CCD image sensor or the like at least in the visible light region. ing.

  In other words, the windshield is colorless and transparent, and is formed so that when white light passes through the windshield etc., it is captured by a CCD image sensor or the like without being colored in a specific color (for example, red). The optical filter is configured to transmit all light in the visible light region. When the threshold Tha or the like is set to 20 in the above equations (3) to (5), the wavelength range for determining an achromatic color is set to be quite narrow.

However, even in the above model, the transmission characteristic Ftglass (λ) of the windshield, the transmission characteristic OPTfilter (λ) of the optical filter, and the spectral sensitivity characteristics [r (λ), g (λ), b ( depending relationship lambda)] and the like, for example, as shown in FIG. 4, at 5500K color temperature T corresponds to white, the theoretical value I _R and I _G is to become in theory value I _B comparable relative intensity In some cases, the values are slightly smaller than the theoretical values I _R and I _G.

Therefore, for example, the above (1) Theoretical values I _R, which is calculated according to _formula, I _G, according to I _B, the above pixel determining conditions that the pixel of the achromatic, for example,
｜ RG ｜ ≦ 20
0 ≦ R−B ≦ 40
0 ≦ GB ≦ 40
It is also possible to set as follows.

  Further, when the imaging device 10 such as a CCD image sensor is mounted on a robot acting autonomously, for example, a protective plate or the like installed in front of the imaging device 10 is colorless and transparent like a vehicle windshield. Not limited to this, when white light passes through a protective plate or the like, it may be captured in a specific color (for example, red). In such a case, the pixels that output the R, G, and B values corresponding to this specific color (red), and the pixels that output the R, G, and B values in the vicinity thereof are achromatic pixels. Conditions for the R, G, and B values of the pixel are set so as to be determined to be present.

  In addition, regardless of the model as described above, an image of an achromatic color chart such as white is captured by the camera system of the imaging device 10 such as a transmission member such as an actual windshield and a protective plate, an optical filter, and a CCD image sensor. It is also possible to set in advance a condition for measuring the R, G, and B values of each pixel output at that time and determining that the pixel is an achromatic pixel based on the measured value.

If it is determined that the pixel is an achromatic color, the adjustment unit 4 uses the correction amounts C _R , C _G , and C _B for the values of R, G, and B for the achromatic color pixel. , G, B values are corrected and adjusted. At that time, when a white plate is colored in a specific color (for example, red) and imaged when white light is transmitted through the protective plate etc. as described above, The R, G, and B values of the pixels that output the R, G, and B values corresponding to this specific color (red) are such that R = G = B, that is, an achromatic color such as white or gray. It is adjusted so that it becomes the corresponding color. In addition, correction amounts C _R , C _G , and C _B of R, G, and B values for achromatic pixels are set in advance so as to be adjusted as described above.

  Therefore, in the above case, when the outside world is viewed with the human eye through a colored protective plate, etc., the whole appears reddish, and the original white object also appears red. The R, G, and B values of the pixel are achromatic colors such as white and gray.

  By performing such adjustment, as in the present embodiment, even in a camera system in which a transmission member such as a windshield or a protection plate of a vehicle or an optical filter such as an infrared cut filter or a polarization filter is interposed, an achromatic color is obtained. It becomes possible to accurately adjust the values of R, G, and B output from the pixels where the subject is imaged to the values of R, G, and B corresponding to achromatic colors.

The correction amounts C _R , C _G , and C _B for R, G, and B values for achromatic pixels are the correction amounts C _R C ^* _R and C for R, G, and B values for chromatic pixels. ^{_{G C * G, C B C}} * correction amount for the color temperature as ^{_{B C * R, C * G}} , the ^C _{* B} unmultiplied. However, the correction amounts for the color temperature are not considered in the correction amounts C _R , C _G , and C _B for the R, G, and B values for the achromatic color pixels.

As shown in FIG. 4, the relative values of R, G, and B based on the above equation (1) used for calculating the correction amounts C _R , C _G , and C _B of the R, G, and B values for the achromatic color pixel Looking at the theoretical values I _R , I _G and I _B of the intensity, when the color temperature T is low, the theoretical value I _R is larger than the theoretical values I _G and I _B , and the color temperature T is When it is high, the theoretical value I _B is larger than the theoretical values I _R and I _G.

Therefore, it is considered that the correction amounts C _R , C _G , and C _B for the values of R, G, and B for the achromatic pixel already include the correction amount for the color temperature. In FIG. 4, the reason why the theoretical values I _R , I _G , and I _B when the color temperature T is 5500 K corresponding to white is not I _R = I _G = I _B is mainly the transmission of the windshield. This is considered to be due to the characteristics and transmittance characteristics of the optical filter.

On the other hand, when the pixel is a chromatic color, the R, G, and B values are corrected using the correction amounts C _R , C _G , and C _B for the achromatic pixel. In this case, for example, the saturation of the chromatic pixels may be reduced, and an image that should be originally captured in color may be corrected to a monochrome image. Then, as described above, if the image is captured in this way, problems such as erroneous recognition of the color of the subject based on the captured image occur.

Therefore, in the present embodiment, as described above, the adjustment for the pixel determined to be a chromatic color pixel is configured to be performed in a different manner from the adjustment for the achromatic color pixel. Then, the chromatic color table is referred to, and R, G, B correction values C _R C ^* _R , C _G C ^* _G , C _B C ^* _B for the chromatic pixel are used to calculate the R of the pixel. The values of G and B are corrected and adjusted.

At that time, R in the chromatic color pixel, G, the correction amount for B _{C R, C G,} also in _{C B,} as shown in FIG. 9, R, G, the theoretical value _I R of _{B, I G, I B} is the theoretical value I _G when the color temperature T is _low, has a large value theory I _R compared to I _B, the theoretical value I _R in the case the color temperature T is higher _than I _G since the theoretical value I _B is larger, the correction amount C _R in the chromatic color pixels R, G, for _B, C _G, is already considered to include the correction amount for color temperature in C _B.

After that, the correction amounts C ^* _R , C ^* _G , and C ^* _B for the color temperature are further multiplied, and the correction amounts of the R, G, and B values for the chromatic color pixels are calculated as C _R C ^* _R , C _G The reason for setting C ^* _G and C _B C ^* _B is that, as described above, the pixel color is accurately determined even when the pixel color is also taken dark, such as when it is cloudy, rainy, or shaded. In order to convert it so that it can be recognized, the values of R, G, and B of the pixel at the color temperature T (color temperature index value T ^* ) are changed to R _5500K , G _5500K in a state of 5500K corresponding to white in a clear sky, This is because conversion is performed so as to approach the value of B _5500K .

Accordingly, even when the pixel color is also imaged darkly, for example, when it is cloudy, using the correction amounts C _R , C _G , and C _B for _R , _G , and _B in the chromatic color pixel, the pixel color If it is adjusted so that can be accurately recognized, it is possible to use C _R , C _G , and C _B as correction amounts of R, G, and B values for chromatic pixels.

However, even in this case, the correction amounts C _R , C _G , and C _B are calculated by a method different from the case of the achromatic color that calculates Input (λ) as 1 for all wavelengths λ. For example, as in this embodiment, the theoretical values I _R , I _G , and I _B of the relative intensities of R, G, and B calculated by setting Input (λ) as in the above formulas (7) to (9). Is calculated based on

  In the adjustment unit 4 of the present embodiment, for the chromatic pixel, only the largest color component among the R, G, and B values of the pixel is to be adjusted, and the color component having the second largest value is adjusted. However, the reason is that the largest color component is reflected most strongly in the pixel color, and if the largest color component is adjusted, the color of the pixel is not adjusted. This is because the adjustment is sufficient, and the calculation process is lightened and performed at high speed.

  Accordingly, when there is no need to increase the speed of the arithmetic processing, for example, when there is almost no difference between the value of the largest color component and the value of the second largest color component, both colors It is possible to correct the components together, or to correct all three color components.

As described above, according to the color balance adjusting device 1 according to the present embodiment, whether the pixel is an achromatic pixel or a chromatic pixel based on the R, G, and B values of each pixel. After the determination, whether the pixel is an achromatic pixel or not according to the relationship between the correction value and the color temperature index value T ^* preset in a different manner for the achromatic pixel and the chromatic pixel. R, G, B values based on the color temperature index value T ^* by using the above-mentioned relationship depending on whether the pixel is a chromatic color, that is, using the achromatic color table and the chromatic color table to be referenced. A correction amount is calculated, and R, G, and B values for each pixel are adjusted according to the correction amount.

  Therefore, it is possible to appropriately adjust the R, G, and B values of the pixel depending on whether the pixel is a pixel in which an achromatic subject is imaged or a pixel in which a chromatic subject is imaged. Even in a camera system in which a transmissive member such as a windshield and a protective plate, an optical filter such as an infrared cut filter or a polarization filter, and the like are interposed in front of the imaging device 10, R of each pixel of an image captured by the imaging device 10 , G and B can be accurately corrected and adjusted.

  For this reason, even in such a camera system, it is possible to accurately adjust an achromatic color such as white or gray and a chromatic color such as red, green or blue, and based on the captured image. Thus, the color of the subject can be accurately recognized. For example, when the imaging device 10 is mounted on a vehicle, a robot that acts autonomously, or the like to detect a subject, it is possible to accurately detect the subject and accurately detect the subject. Become.

1 color balance adjustment device two-color temperature calculation section 3 judging means 4 adjusting means 10 imaging device _{C R, C G,} R for _{C B} achromatic pixels, G, the correction amount ^C _* R values of ^B, _{C *} ^G, Correction amount for C ^* _B color temperature C _R C ^* _R , C _G C ^* _G , C _B C ^* _B Correction amount of R, G, B values for chromatic color pixels
Ftglass (λ) Transmission characteristics of vehicle windshield (spectral sensitivity characteristics of imaging device)
_{I R, I G, I B} R, G, relative intensity by the theoretical values M (lambda) blackbody radiation of the relative intensities of the B
OPTfilter (λ) Optical filter characteristics (spectral sensitivity characteristics of the imaging device)
Ratio of each theoretical value of r _R , r _G , r _B [r (λ), g (λ), b (λ)] Spectral sensitivity characteristic (spectral sensitivity characteristic of imaging device)
T ^* color temperature index value Th1 first threshold Th2 second threshold Tha to Thc predetermined threshold Ω integration range for wavelength (predetermined wavelength range)

Claims (7)

In a color balance adjustment device for an image taken by an imaging device,
Color temperature calculation means for calculating a color temperature index value for each pixel based on the R, G, and B values of each pixel of the image input from the imaging device;
Determination means for determining whether each pixel is an achromatic pixel or a chromatic pixel based on the R, G, and B values of each pixel of the image;
According to the relationship between the color temperature index value and the correction amount preset in different manners for the achromatic pixel and the chromatic pixel, each pixel is an achromatic pixel or a chromatic color pixel. The correction amount for the R, G, and B values based on the color temperature index value is calculated using the relationship depending on whether the pixel is a pixel, and the R, G, and B values for each pixel are calculated according to the correction amount. Adjusting means for adjusting; and
A color balance adjusting device comprising:   The correction amount of the R, G, and B values for the achromatic pixel is a predetermined wavelength obtained by multiplying the spectral sensitivity characteristic of the imaging device and the relative intensity due to black body radiation under the condition for imaging white. Of the theoretical values of the relative intensities of R, G, and B for each color temperature index value when integrated over a range, the relative intensity is calculated based on the theoretical value that is the second largest for each color temperature index value. 2. The color balance adjusting apparatus according to claim 1, wherein the color balance adjustment device is set for each color temperature index value as a reciprocal of a ratio of the theoretical values.   The adjustment means selects pixels having the same R, G, and B values from among the pixels that are determined to be achromatic pixels by the determination means from the adjustment targets of the R, G, and B values by the correction amount. 3. The color balance adjustment apparatus according to claim 2, wherein the color balance adjustment apparatus adjusts the values of R, G, and B according to the correction amount for the other pixels that are excluded.   The correction amounts of the R, G, and B values for the chromatic pixels are the spectral sensitivity characteristics of the imaging device in the wavelength ranges where the sensitivity is high for each of R, G, and B in the spectral sensitivity characteristics of the imaging device. The theoretical values of the relative intensities of R, G, and B for each color temperature index value obtained by integrating the values obtained by multiplying the relative intensities by black body radiation, and the relative intensities of R, G, and B at the reference color temperature The relative intensity for each color temperature index value out of the correction value for the color temperature calculated by dividing the respective theoretical values of the color temperature and the theoretical values of the relative intensities of R, G, and B for each color temperature index value Is set for each color temperature index value as a value obtained by multiplying the correction amount for R, G, and B calculated as the reciprocal of the ratio of the respective theoretical values calculated based on the second largest theoretical value. Claims Color balance adjustment device according to any one of claims 3 to.   5. The wavelength range having high sensitivity for each of R, G, and B in the spectral sensitivity characteristics of the imaging apparatus is set as a wavelength range having the same wavelength width for R, G, and B. 6. Color balance adjustment device.   The adjustment means adjusts only the largest color component among the R, G, and B values of the pixel determined to be a chromatic color pixel by the determination means, and sets the largest color component value and the largest value. When the difference from the value of the small color component is equal to or greater than a predetermined first threshold, the value of the largest color component is multiplied by the correction amount for the color component, and the difference is smaller than the predetermined first threshold. When the value is equal to or smaller than the second threshold value set in the value, the value of the largest color component is not adjusted, and when the difference is a value between the first threshold value and the second threshold value, 6. The R, G, and B values are adjusted by multiplying the value of the largest color component by a value obtained by linearly interpolating the correction amount in accordance with the difference. Color balance adjustment device.   The determination means sets a condition that | R−G |, | R−B |, and | B−G | are each equal to or less than a predetermined threshold based on the R, G, and B values of each pixel of the image. 7. If it satisfies, it is determined that the pixel is an achromatic pixel, and otherwise, it is determined that the pixel is a chromatic pixel. The color balance adjusting device according to item.

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