JP2001251644A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device that can obtain excellent color reproducibility even under lighting with a poor color rendering property without the need for new provision of an external sensor. SOLUTION: The image pickup device is provided with an image pickup element 2 that converts an optical image of an object into an image pickup signal, a lens unit 1 that forms an optical image onto the image pickup element 2, a color separation means that separates color signals R', G', B' from the image pickup signal, a WB adjustment means 8b that adjusts white balance of the color signal by adjusting levels of the B', R' signals according to R, B signal gains respectively, a color signal integration means 8e that respectively calculates an integrated value of the color signals R, G, B whose white balance is adjusted, an arithmetic means 7A that outputs the R, B signal gains to the WB adjustment means 7b so that the integration values are identical to each other, an adder sbutractor 8d that converts the R, G, B signals into color difference signals through the matrix arithmetic operation using matrix coefficients from the arithmetic means 7A, and the arithmetic means 7A corrects the matrix coefficients according to the R, B signal gains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a video camera and an electronic still camera, and more particularly to an image pickup apparatus provided with means for correcting the color reproducibility of the image pickup apparatus.

[0002]

2. Description of the Related Art FIG. 20 is a block diagram of a conventional image pickup apparatus, and is a block diagram mainly related to color signal processing. 20, reference numeral 1 denotes a lens unit, 2 denotes an image sensor, 3 denotes an iris driver, and 4 denotes a timing generator (hereinafter referred to as TG).
5 is a front signal processing means, 6 is an A / D converter, 7 is an arithmetic means, 8 is a signal processing means, 9 is an output terminal, 10 is an image signal integrating means, 11 is an iris control means, and 12 is an iris control means. It is a zoom lens driver. In the lens unit 1, 1a is an iris, 1b is a lens system, and 1d is a zoom lens. Also, the signal processing means 8
8a, a color separation unit, 8b a white balance (WB) adjustment unit adjustment unit, 8c a matrix unit, 8c
d is an adder / subtractor, 8e is a color signal integrating means, 8g is an encoder, 8ba is a gain control means for an R (Red) signal, 8bb
Is gain control means for a G (Green) signal, and 8bc is B
(Blue) Signal gain control means.

[0003] The conventional image pickup apparatus shown in FIG. 20 includes a lens unit 1, an image pickup device 2, an iris driver 3, and a TG 4.
Signal processing means 5, A / D converter 6, arithmetic means 7, signal processing means 8, output terminal 9, image signal integration means 10, iris control means 11, zoom lens driver 12, And

The lens unit 1 has an iris (aperture mechanism) 1a and a lens system 1b, and forms an optical image of a subject on the image sensor 2. The iris 1 a is driven by an iris driver 3 to open and close, and adjusts the amount of light incident on the image sensor 2. The lens system 1b includes a plurality of lenses including a zoom lens 1d. The zoom lens 1d is driven by the zoom lens driver 12 to move back and forth. This zoom lens 1d
The magnification (hereinafter, referred to as the imaging magnification) of the subject to be imaged can be changed depending on the position.

An image sensor 2 converts light into an electric signal.
It has a large number of pixels arranged in a dimension and a plurality of types of color filters arranged on each pixel to obtain a color image, converts an optical image of a subject into an image signal, and converts this image signal The output is sent to the position signal processing means 5. The above color filters are, for example, three kinds of color filters of primary colors of R, G, and B. The TG 4 is controlled by the arithmetic unit 7 to generate a drive pulse for the image sensor 2 and output the drive pulse to the image sensor 2.

The pre-signal processing means 5 includes a CDS (Correlat
ed Double Sampling (correlated double sampling) circuit,
A gain adjustment circuit. This prefix signal processing means 5
The CDS circuit performs CDS on the imaging signal input from the imaging element 2 to remove noise, and further amplifies the imaging signal in the gain adjustment circuit to adjust the level of the imaging signal. The signal is output to the A / D converter 6. Also, A
The / D converter 6 converts the imaging signal input from the pre-signal processing means 5 from an analog signal to a digital signal,
The signal is output to the color separation means 8a of the signal processing means 8.

The image signal integrating means 10 integrates the image signal output from the pre-signal processing means 5 at least for each field or frame, and outputs the integrated value to the iris control means 11. Also, the iris control means 11
Outputs a control signal to the iris driver 3 so that the integrated value by the imaging signal integrating means 10, that is, an average picture level (APL) becomes a predetermined constant level, and controls the iris 1a by the iris driver 3. Open and close. The arithmetic unit 7 outputs a control signal to the zoom lens driver 12 so that the imaging magnification becomes a desired magnification, and the zoom lens driver 12
Moves the zoom lens 1d.

The signal processing means 8 separates the R, G, B primary color signals from the digital image signal input from the A / D converter 6, and separates the RY signal and B signal from these primary color signals.
-Y signal is generated, and a chrominance signal based on the RY signal and the BY signal is output to the output terminal 9. The signal processing unit 8 includes a color separation unit 8a and a WB adjustment unit 8
b, matrix means 8c, adder / subtractor 8d, color signal accumulating means 8e, and encoder 8g.

The color separation means 8a converts an input image signal into an R signal (color signal R ') and a G signal (color signal G').
And the B signal (color signal B ′), and outputs these color signals R ′, G ′, and B ′ to the WB adjustment unit 8b.

The WB adjusting means 8b includes a gain adjusting means 8ba for adjusting the gain of the color signal R ', a gain adjusting means 8bb for adjusting the gain of the color signal G', and a gain adjusting means for adjusting the gain of the color signal B '. Means 8bc. The WB adjusting means 8b amplifies or attenuates the color signal R 'in the gain adjusting means 8ba according to the R signal gain value from the calculating means 7, and the chrominance signal in the gain adjusting means 8bc in accordance with the B signal gain value from the calculating means 7. By amplifying or attenuating B ', the white balance (WB) of the color signals R', G ', and B' is adjusted so that the signal levels of the R, G, and B signals are equal to each other, and the R signal after WB adjustment (Color signal R), G signal (color signal G), and B signal (color signal B) are output to the color signal integrating means 8e and the adder / subtractor 8d.

The color signal accumulating means 8e accumulates the WB-adjusted color signals R, G, and B at least for each field or for each frame, thereby obtaining an integrated value ΣR, ΣB of the color signals R, G, and B. , ΣG are calculated, and the integrated values ΣR, ΣB, ΣG are output to the calculating means 7.

The calculating means 7 outputs the R signal gain value and the B signal gain value to the WB adjusting means 8b so that the integrated values ΣR and ΣB become equal to the integrated value ΣG.

The adder / subtractor 8d converts the WB-adjusted color signals R, G, and B into color difference signals, an RG signal (a difference signal between the R signal and the G signal) and a BG signal (a B signal and a G signal). Is generated and output to the matrix means 8c.

The matrix means 8c receives the input R-G
The RY signal (the difference signal between the R signal and the Y signal as the luminance signal) and the BY signal (the B signal and the Y signal) are subjected to a matrix operation represented by the following equation (1) to obtain the RY signal and the BG signal. RY signal and BY signal are output to the encoder 8g.

(Equation 1) In the equation (1), a11, a12, a21, a22
Is a matrix coefficient. These matrix coefficients a
11, a12, a21, and a22 are fixed values in the conventional imaging apparatus of FIG.

The encoder 8g encodes the RY signal and the BY signal so that the signal output from the output terminal 9 has a required signal format, and outputs the encoded signal to the output terminal 9. Here, the RY signal and the B signal
A chrominance signal of a video signal is generated by performing balanced modulation of the −Y signal, and the chrominance signal is output to the output terminal 9.

In the conventional image pickup apparatus shown in FIG. 20, the spectral sensitivity characteristics of the image pickup device 2 and the matrix means 8c are adjusted so that the color reproducibility of a video signal obtained under illumination of a standard light source becomes the color reproducibility which is a design target. Matrix coefficient a1
1, a12, a13, and a14 are determined in advance.
For example, NTSC (National Television System Commi
In the case of the ttee) method, the spectral response of the imaging device under illumination of a standard light source (for example, C light source) specified by the NTSC method is close to the color matching function specified by the NTSC method. Spectral sensitivity characteristics of the image sensor 2 and matrix coefficients a11, a12, a13, a1 of the matrix means 8c.
4 is determined in advance. Therefore, if the subject is NTSC
When illuminated with the above-mentioned standard light source specified by the method, ideal color reproducibility is obtained.

However, the illumination of the subject cannot always be set by the photographer, and there may be various illuminations such as a fluorescent lamp and a mercury lamp in an actual imaging environment. For example, when photographed under illumination of a general fluorescent lamp, when the color rendering of the fluorescent lamp is low, color reproducibility is deteriorated compared to when photographing under illumination having good color rendering such as sunlight. There was a problem. This is because the color signals R, G, and B generated in the imaging device are obtained from a multiplication value of the spectral sensitivity characteristics of the image sensor 2, the spectral characteristics of the illumination, and the spectral reflection characteristics of the subject. This is because the spectral characteristics of a light source such as sunlight having good color rendering properties and a light source such as a fluorescent lamp having poor color rendering properties are significantly different.

In order to solve these problems, there is a conventional image pickup apparatus which improves the color reproducibility of the image pickup apparatus by determining a light source in a photographing environment and making the above matrix coefficient variable according to the light source. Was. FIG. 21 is a configuration diagram of a conventional image pickup apparatus for improving color reproducibility. In FIG. 21, reference numeral 13 denotes an external photometric sensor (external light sensor).
The same components as those of 0 are denoted by the same reference numerals.

The external light sensor 13 includes, for example, R,
It has three sensors provided with G and B color filters, and outputs the output signals of each sensor to the arithmetic means 7. The spectral sensitivity characteristics of the color filter of the external light sensor have the same characteristics as those of the color filter of the image sensor 2. Outside light sensor 13
Each of the sensors receives the light emitted from the illumination at the time of photographing through the color filter, so that the calculating means 7 determines the R, G, B ratio of the illumination light by the output signal from the external light sensor 13. R, G, B
The color rendering of the illumination can be estimated from the ratio. Generally, a fluorescent lamp has less R and B components than sunlight having a color rendering property (Ra) of 100. This is because the G component is increased in order to increase the luminous efficiency of the fluorescent lamp. Therefore, in the case of artificial illumination light, the value of R / G and the value of B / G tend to decrease as the color rendering property decreases.

The conventional image pickup apparatus shown in FIG.
The color rendering of the illumination is determined based on the R, G, B ratios of the illumination obtained from Step 3, and according to the color rendering, the calculating means 7 calculates the matrix coefficients a11, a12,
a21 and a22 were adjusted to correct the color reproducibility.

[0021]

However, FIG.
The conventional imaging apparatus described in (1) has a problem that good color reproducibility may not be obtained when photographing under illumination having poor color rendering properties.

Further, in order to realize the image pickup apparatus shown in FIG. 21, it is necessary to provide an external light sensor for determining the color rendering of the illumination light, which is disadvantageous in reducing the size of the image pickup apparatus. In addition, there is a problem that the design is restricted and the cost is disadvantageous.

The present invention has been made to solve such a conventional problem, and it is possible to correct color reproducibility even under illumination having poor color rendering properties without newly providing an external sensor. It is intended to obtain an imaging device.

[0024]

According to a first aspect of the present invention, there is provided an image pickup device for converting an optical image of a subject into an image pickup signal, and an image pickup device for converting the optical image into an image pickup signal. A lens unit that forms an image on the element, a color separation unit that separates the first, second, and third color signals from the image signal, and a signal level of the first color signal is adjusted according to a first signal gain value And a second signal gain value according to the second signal gain value.
White balance adjusting means for adjusting the signal levels of the first, second, and third color signals so that the signal levels of the first, second, and third color signals are equal to each other. Integrating means for calculating integrated values of the second and third color signals, and calculating means for outputting the first and second signal gain values to the white balance adjusting means so that the integrated values are equal to each other. Conversion means for converting the white balance-adjusted color signal into a color difference signal by a matrix operation using a matrix coefficient from the operation means, wherein the operation means is adapted to execute the matrix coefficient operation in accordance with the signal gain value. Is corrected.

According to a second aspect of the present invention, in the image pickup apparatus, the lens unit has an iris for adjusting a light amount incident on the image sensor, and a sensor for detecting an aperture ratio of the iris, and Is characterized in that a matrix coefficient is corrected according to the signal gain value and the aperture ratio.

According to a third aspect of the present invention, in the image pickup apparatus, the lens unit has means for changing an imaging magnification of a subject in accordance with a control signal from the arithmetic means, and the arithmetic means includes the signal gain value and the signal gain value. The matrix coefficient is corrected according to the imaging magnification.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram of an imaging apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is a lens unit, 2 is an image sensor, 3 is a driver, 4 is a timing generator (TG), 5 is a pre-signal processing unit, 6 is an A / D converter, 7A is an arithmetic unit,
8 is a signal processing means, 9 is an output terminal, 10 is an imaging signal integrating means, 11 is an iris control means, and 12 is a zoom lens driver. In the lens unit 1, 1a
Denotes an iris, 1b denotes a lens system, and 1d denotes a zoom lens. In the signal processing means 8, 8a is a color separation means, 8b is a white balance adjustment means (WB adjustment means), 8c is a matrix means, 8d is an adder / subtractor, 8e is a color signal integration means, 8g is an encoder, and 8ba is R Signal gain control means, 8bb is G signal gain control means, 8bc
Is gain control means for the B signal. In FIG. 1,
The same components as those in FIG. 20 are denoted by the same reference numerals.

The imaging apparatus according to the first embodiment shown in FIG. 1 includes a lens unit 1, an imaging element 2, an iris driver 3,
TG 4, pre-signal processing means 5, A / D converter 6
, Arithmetic means 7A, signal processing means 8, output terminal 9
, Imaging signal integrating means 10 and iris control means 11
And a zoom lens driver 12. As described above, the imaging device according to the first embodiment is obtained by replacing the arithmetic unit 7 with the arithmetic unit 7A in the conventional imaging device of FIG.

The lens unit 1 has an iris 1a and a lens system 1b, and forms an optical image of a subject on the image sensor 2. The iris 1 a is driven by an iris driver 3 to open and close, and adjusts the amount of light incident on the image sensor 2. The lens system 1b includes a plurality of lenses including a zoom lens 1d. Zoom lens 1d
Is driven by the zoom lens driver 12 to move back and forth. The imaging magnification can be changed depending on the position of the zoom lens 1d.

The image sensor 2 converts light into an electric signal.
It has a large number of pixels arranged in a dimension and a plurality of types of color filters arranged on each pixel to obtain a color image. The image sensor 2 converts an optical image of a subject into an image signal, and outputs the image signal to the front signal processing unit 5 (images the subject and outputs an image signal of the subject to the front signal processing unit 5). ). Representative image sensors include a CCD sensor and a CMOS sensor. Typical color filters include R (Red) and G (Gr
een), B (Blue) primary color filters and Ye (Yellow), Mg (Magent)
a), 4 of complementary colors of Cy (Cyan) and G (Green)
There are different types of color filters. The TG 4 is controlled by the arithmetic unit 7A, generates a drive pulse for the image sensor 2, and outputs the drive pulse to the image sensor 2.

The pre-signal processing means 5 has a CDS (correlation double sampling) circuit and a gain adjustment circuit. The pre-signal processing unit 5 removes noise by performing CDS on the image signal input from the image sensor 2 in the CDS circuit, and further adjusts the level of the image signal by amplifying the image signal in the gain adjustment circuit. The image signal whose noise has been removed and whose level has been adjusted is output to the A / D converter 6. The A / D converter 6 converts the image signal input from the pre-signal processing unit 5 from an analog signal to a digital signal, and converts the image signal into a color separation unit 8 of the signal processing unit 8.
output to a.

The image signal integrating means 10 integrates the image signal output from the pre-signal processing means 5 at least for each field or frame, and outputs the integrated value to the iris control means 11. Also, the iris control means 11
Outputs a control signal to the iris driver 3 so that the integrated value by the imaging signal integrating means 10, that is, an average picture level (APL) becomes a predetermined constant level, and controls the iris 1a by the iris driver 3. Open and close. In addition, the arithmetic means 7A includes:
A control signal is output to the zoom lens driver 12 so that the imaging magnification becomes a desired magnification, and the zoom lens driver 1
2 moves the zoom lens 1d.

The signal processing means 8 separates the R, G, B color signals from the digital image signal input from the A / D converter 6, and separates the R, Y and B signals from these color signals.
A Y signal is generated, and a chrominance signal of a video signal based on the RY signal and the BY signal is output to an output terminal 9. The signal processing unit 8 includes a color separation unit 8a and a WB
Adjusting means 8b, matrix means 8c, adder / subtractor 8d
, A color signal integrating means 8e, and an encoder 8g. Note that the video signal may be, for example, a YUV signal (a composite signal of a Y signal that is a luminance signal and a U signal and a V signal that are color difference signals based on a uv chromaticity diagram). Is the UV signal composed of the U signal and the V signal.

The color separation means 8a converts an input image signal into an R signal (color signal R ') and a G signal (color signal G').
And the B signal (color signal B ′), and outputs these color signals R ′, G ′, and B ′ to the WB adjustment unit 8b.

The WB adjusting means 8b includes a gain adjusting means 8ba for adjusting the gain of the color signal R ', a gain adjusting means 8bb for adjusting the gain of the color signal G', and a gain adjusting means for adjusting the gain of the color signal B '. Means 8bc. The WB adjusting unit 8b amplifies or attenuates the color signal R ′ in the gain adjusting unit 8ba according to the R signal gain value from the arithmetic unit 7A, and also controls the chrominance signal in the gain adjusting unit 8bc according to the B signal gain value from the arithmetic unit 7A. By amplifying or attenuating B ', the white balance (WB) of the color signals R', G ', and B' is adjusted so that the signal levels of the R, G, and B signals are equal to each other, and the R signal after WB adjustment (Color signal R), G signal (color signal G), and B signal (color signal B) are output to the color signal integrating means 8e and the adder / subtractor 8d. W
The WB adjustment by the B adjusting means 8b is expressed by the following equation (2).

(Equation 2) In the equation (2), R ′, G ′, and B ′ are respectively WB
R, G, and B signals input to the adjusting means 8b.
G and B respectively represent W output from the WB adjusting unit 8b.
B-adjusted R, G, B signals, WBR, WBG,
WBB is a WB adjustment coefficient of the R, G, and B signals, respectively. In general, the WB adjustment is performed with the gain of the G signal fixed, so that the WB adjustment coefficient WBG of the G signal is a fixed value. The WB adjustment coefficients WBR and WBB are variable values according to the R signal gain value and the B signal gain value input from the arithmetic means 7A, respectively.

The color signal integrating means 8e integrates the WB-adjusted color signals R, G, and B for at least one field or one frame, respectively, thereby obtaining the integrated values ΣR, ΣB of the color signals R, G, and B. , ΣG are calculated, and the integrated values ΣR, ΣB, ΣG are output to the calculating means 7.

The calculating means 7A calculates the R signal gain value corresponding to the WB adjustment coefficient WBR and the B signal gain value corresponding to the WB adjustment coefficient WBB so that the integrated values ΣR and ΣB become equal to the integrated value ΣG. 8b. The calculating means 7A outputs the matrix coefficient corrected according to the R signal gain value and the B signal gain value to the matrix means 8c.

The adder / subtractor 8d converts the WB-adjusted color signals R, G, and B into color difference signals, an RG signal (a difference signal between the R signal and the G signal) and a BG signal (the B signal and the G signal). Is generated and output to the matrix means 8c.

The matrix means 8c receives the input R-G
The RY signal (the difference signal between the R signal and the Y signal as the luminance signal) and the BY signal (the B signal and the A difference signal of the Y signal) is generated, and the RY signal and the BY signal are output to the encoder 8g.

(Equation 3) In Equation (3), b11, b12, b21, and b22 are matrix coefficients. These matrix coefficients b1
1, b12, b21, and b22 are variable values input from the arithmetic means 7A. Note that it is also possible to generate the U signal and the V signal in the matrix means 8c.

Adder / subtractor 8d and matrix means 8c
Is conversion means for converting the WB-adjusted color signals R, G, B into color difference signals (here, RY signal and BY signal) by a matrix operation using a matrix coefficient from the operation means 7A. Make up.

FIG. 2 is a diagram showing a configuration example of the matrix means 8c. In FIG. 2, the matrix means 8c includes multipliers 8h, 8i, 8j, 8k and an adder / subtractor (adder) 8
1, 8 m. Matrix means 8
In c, the RG signal and the BG signal are input, and the matrix coefficients b11 and b1 shown in the equation (3) are input.
Signals corresponding to 2, b21 and b22 are input from the arithmetic means 7A. The multiplier 8h multiplies the RGB signal by the signal b11 and outputs the result to the adder 81. The multiplier 8i outputs B
-Multiply the G signal by the signal of b12 and output to the adder 8l. The adder 8l adds the signal input from the multiplier 8h and the signal input from the multiplier 8i, and performs R-Y
Generate a signal. Further, the multiplier 8k outputs the RG signal and b
21 and is output to the adder 8m. The multiplier 8j multiplies the BG signal by the signal b22 and outputs the result to the adder 8m. The adder 8m adds the signal input from the multiplier 8k and the signal input from the multiplier 8j to generate a BY signal.

The encoder 8g encodes the RY signal and the BY signal so that the signal output from the output terminal 9 has a required signal format, and outputs the encoded signal to the output terminal 9. Here, the RY signal and the B signal
A chrominance signal of a video signal is generated by performing balanced modulation of the −Y signal, and the chrominance signal is output to the output terminal 9. If the required signal format is a color difference signal,
It is also possible to add a sync chip or the like to each of the RY signal and the BY signal and output them individually. Also,
It is also possible to encode U and V signals.

Here, the color reproducibility of the general image pickup apparatus including the image pickup apparatus of the first embodiment in FIG. 1 and the conventional image pickup apparatuses of FIGS. 20 and 21 will be described. First, the RY signal and the BY signal output from the imaging device are obtained by Expression (3), and the color signals R and G constituting the RG signal and the BG signal shown in Expression (3). , G, and B are represented by the following equations (4), (5), and (6).

(Equation 4) In the equations (4), (5), and (6), λ is a wavelength.
R (λ), G (λ), and B (λ) are spectral sensitivity characteristics of the image sensor 2 for the R, G, and B components of the image signal, respectively. L (λ) is the spectral characteristic of illumination of the subject at the time of imaging. O (λ) is the spectral reflection characteristic of the subject. As shown in equations (4), (5), and (6),
The R, G, and B signals correspond to the spectral sensitivity characteristics R of the image sensor 2.
(Λ), G (λ), B (λ) and the spectral characteristic L of the illumination
It is determined as an integrated value of the product of (λ) and the spectral reflection characteristic O (λ) of the subject over the entire wavelength range.

FIG. 3 is a diagram showing an example of the spectral sensitivity characteristics of the image sensor 2 for the R, G, and B components. In FIG. 3, the spectral sensitivity is a relative spectral sensitivity with the peak value of the spectral sensitivity for the G component set to 1.0. FIG. 4 shows an example of spectral characteristics of illumination having good color rendering properties (good color reproducibility in an imaging device) represented by a halogen lamp, sunlight, and the like. FIG. 5 shows that the color rendering properties are higher than those of the illumination of FIG. It is also an example of the spectral characteristics of illumination represented by a fluorescent lamp, which is inferior. 4 and 5, the spectral level is a relative spectral level with a peak value of 1.0 in all wavelength ranges. Since the illumination represented by the fluorescent lamp and the like shown in FIG. 5 is configured by a combination of the emission line spectra, the color rendering properties are inferior to those of the illumination represented by the halogen lamp and the sunlight shown in FIG. The color reproducibility of the obtained representative signal obtained under the illumination of FIG. 4 does not always match the color reproducibility of the video signal obtained under the illumination of FIG.

In the image pickup apparatus, the spectral sensitivity characteristics of the image pickup device 2 (see FIG. 3) are set so that the color reproducibility of the video signal obtained under illumination of the standard light source as shown in FIG. ) And the matrix coefficient of the matrix means 8c (in the imaging device of the first embodiment, b1
1, b12, b21, and b22, and a11, a12, a21, and a22 in Equation (1) are determined in advance in the conventional imaging apparatus. For example, in the case of the NTSC system, NT
The spectral sensitivity characteristics of the image sensor 2 and the matrix of the matrix means 8c are set such that the spectral response of the image pickup device under illumination of the standard light source specified by the SC method is close to the color matching function specified by the NTSC method. The coefficient is determined in advance. Therefore, when the subject is illuminated by the above-mentioned standard light source defined by the NTSC system, ideal color reproducibility is obtained.

Further, under illumination as shown in FIG. 5, which has a different spectral characteristic from the standard illumination, the matrix means 8c
By adjusting the matrix coefficients of R,
The G and B signals can be made equal to the R, G and B signals obtained under illumination as shown in FIG. 4 (this is called metamerism). Metamerism may not always be the same for all illumination spectral characteristics,
The color reproducibility can be improved by changing the matrix coefficient according to the illumination so as to approximate it. The conventional imaging apparatus of FIG. 21 adjusts a matrix coefficient based on the R, G, B ratio of illumination obtained from the external light sensor 13 to correct color reproducibility.

Next, a correction operation (improvement operation) of the color reproducibility in the image pickup apparatus according to the first embodiment will be described. FIG.
5 is a flowchart illustrating a procedure for correcting color reproducibility in the imaging apparatus according to Embodiment 1 of the present invention. The procedure of FIG. 6 is a WB adjustment step WBS (steps S1 to S8).
And the matrix correction step MCS (steps S9 to S
11).

The arithmetic means 7A has means internally serving as an up / down counter for increasing or decreasing a numerical value by "1" one by one for the R signal and the B signal. The value of the up / down counter of the R signal is UDCR, and the value of the up / down counter of the B signal is UDCB. The calculating means 7A outputs the counter value UDCR as an R signal gain value to the signal gain adjusting means 8ba of the WB adjusting means 8b, and uses the counter value UDCB as a B signal gain value in WB
The signal is output to the signal gain adjusting means 8bc of the adjusting means 8b.

The WB adjusting means 8b is provided with a color separating means 8
The color signals R ′, G ′, and B ′ input from a are converted to the R and B signal gain values UDCR and UDC input from the arithmetic unit 7A.
Using the WB adjustment coefficients WBR and WBB corresponding to B and the WB adjustment coefficient WBG having a fixed value, WB according to equation (2)
The color signals R, G, and B that have undergone the WB adjustment are adjusted.
Here, in order to simplify the explanation, the R signal gain value UDC
R = WB adjustment coefficient WBR, B signal gain value UDCB = WB
The adjustment coefficient is WBB. The signal gain adjusting means 8ba
The gain of the R signal is increased or decreased according to the signal gain value UDCR (= WB adjustment coefficient WBR).
The gain of the B signal is increased or decreased according to the B signal gain value UDCB (= WB adjustment coefficient WBB). The signal gain adjusting means 8bb keeps the gain of the G signal constant according to the fixed value of the WB adjustment coefficient WBR. UDC for constant gain G signal
If the values of R and UDCB decrease, the WB adjustment coefficient W
The values of BR and WBB also become smaller, so that the R signal and B
The signal gain is reduced. UDCR and UDC
As the value of B increases, the values of the WB adjustment coefficients WBR and WBB also increase, and the gains of the R signal and the B signal increase.

The WB adjustment steps shown in FIG.
S9) will be described below. First, in step S1, the calculating means 7A outputs the initial values WBR0 and WBB0 of the R and B signal gain values (counter values) UDCR and UDCB to the signal gain adjusting means 8ba and 8bc of the WB adjusting means 8a. As a result, the signal gain adjusting means 8ba sets R
The signal gain is set according to the initial value WBR0, and the signal gain adjusting means 8bc sets the B signal gain according to the initial value WBB0.

Next, in step S2, the integrating means 8
“c” integrates the WB-adjusted color signals R, G, and B for each one field or one frame or more corresponding to one screen of video, and outputs the integrated values ΣR, ΣG, and ΣB to the arithmetic means 7B. .

Next, the calculating means 7A compares the integrated values ΣR and ΣG in step S3. If the integrated value ΣR of the R signal is smaller than the integrated value ΣG of the G signal, in step S4, the counter value (R signal gain value) UDC
R is increased (increased) by a predetermined constant value i. This corresponds to increasing the R signal gain in the WB adjusting means 8b. Also, the integrated value of the R signal ΣR
Is larger than the integrated value ΣG of the G signal, in step S5, the counter value (R signal gain value) UDCR is decreased (decreased) by a predetermined constant value i.
This corresponds to reducing the R signal gain in the WB adjusting means 8b.

Next, the calculating means 7A compares the integrated values ΣB and ΣG in step S6. If the integrated value ΣB of the B signal is smaller than the integrated value ΣG of the G signal, in step S7, the counter value (B signal gain value) UDC
B is increased (increased) by a predetermined constant value j. This corresponds to increasing the B signal gain in the WB adjusting means 8b. Also, the integrated value of the B signal 信号 B
Is larger than the integrated value ΣG of the G signal, in step S8, the counter value (B signal gain value) UDCB is reduced (decreased) by a predetermined constant value j.
This corresponds to reducing the B signal gain in the WB adjusting means 8b.

The steps S2 to S8 of the WB adjustment step WBS are repeated with a matrix correction step MCS (steps S9 to S14) described later interposed therebetween, so that the integrated values ΣR, ΣG, ΣB are substantially equal. Thus, the signal gains of the signals R ′ and B ′ that are color-separated from the imaging signal are adjusted, and the WBs of the R, G, and B signals are adjusted so that the levels of the R, G, and B signals are substantially equal. After the WB adjustment is completed (after the levels of the R, G, and B signals have become substantially equal), the above W
For each B adjustment step, the up / down counter is:
Up operation and down operation will be repeated alternately,
The counter values UDCR and UDCB converge to the values when the WB adjustment is completed.

Before explaining the matrix correction step MCS (steps S9 to S14) of FIG.
Relationship between R and UDCB values and types of illumination (light source) (including color rendering properties and color temperatures), and R and B signal gain values UD
The limitation of the adjustment range of CR and UDCB will be described below. FIG. 7 is a diagram showing the relationship between the values of UDCR and UDCB and the type of illumination (light source), and the adjustment range of UDCR and UDCB.

In general, a halogen lamp, sunlight (color rendering property Ra = 100), a standard light source (for example, JIS Z872)
In the case of using illumination having extremely high color rendering properties such as 0, A, C, D50, and D55 light sources, the relationship between the illumination color temperature and the values of UDCR and UDCB when WB adjustment is completed is represented by a curve in FIG. L. For example, the point M in FIG.
000 [K (Kelvin)] are the values of UDCR and UDCB when the WB is adjusted in sunlight (reddish, sunset, etc.), and point N in FIG. 7 is sunlight (blueish) having a color temperature of 5800 [K]. , UDCR and UDCB when the WB adjustment is performed in the clear sky.

The WB adjustment in the image pickup apparatus of the first embodiment and the conventional image pickup apparatuses shown in FIGS. 19 and 20 is based on the premise that an integrated image becomes an achromatic color when all the taken images are integrated. It is called a method. The TTL WB adjustment has a problem that when the subject is a single color or when a specific color occupies most of the subject, the color becomes lighter or an error occurs in the WB adjustment.
For this reason, in an imaging apparatus that employs TTL WB adjustment, the UDCR and UDCB adjustment ranges in WB adjustment are limited to avoid the above-described problem and increase the accuracy of WB adjustment.

In FIG. 7, the area ABCDEF is the adjustment range of UDCR and UDCB in WB adjustment. Therefore, in the WB adjustment, only the value within the above adjustment range is U
The adjustment values of DCR and UDCB are allowed, and the adjustment of UDCR and UDCB to values outside the above adjustment range is prohibited.
Range. The above adjustment range is set to UDC when a white subject is imaged under various illuminations.
It is predetermined based on the range of values that R and UDCB can take. In the adjustment range ABCDEF of FIG. 7, the WB tracking range of the color temperature in sunlight is 2800.
The range is from [K] (point A) to 8000 [K] (point D).

In FIG. 7, the subject is G (Green).
, The values of UDCR and UDCB in the WB adjustment go to the upper right direction, and the subject is Mg (Magenta).
, The values of UDCR and UDCB in the WB adjustment move toward the lower left. Further, usually, there is no Mg illumination due to the luminous efficiency of the illumination light, and the lower the color rendering property, the more the color is directed to the direction of G. Therefore, the values of UDCR and UDCB in the WB adjustment move toward the upper right as the color rendering property becomes worse. The area ADKH in FIG. 7 shows the WB when white is imaged under illumination such as a three-wavelength fluorescent lamp having relatively good color rendering properties (however, the color rendering properties are inferior to the area ABCD).
This is the range of the values of UDCR and UDCB when the adjustment is completed. A region HKEF in FIG. 7 is a range of values of UDCR and UDCB when WB adjustment is completed when white is imaged under illumination of a white fluorescent lamp or the like whose color rendering property is inferior to that of a three-wavelength fluorescent lamp. .

The WB adjustment is completed by repeating the WB adjustment operation (steps S2 to S9 of the WB adjustment step WBS in FIG. 6), and the R, G, B signals from which the WB has been obtained are obtained. After the completion of the WB adjustment, UDCR and UDCB converge to values according to the type of illumination. UDCR, U above
Since the DCB is generated by the arithmetic means 7A, the area ABCD, the area ADKH, and the area HKEF shown in FIG.
Is set in advance in the arithmetic means 7A, the arithmetic means 7A calculates the UDCR,
UDCB value (UDCR, UD when WB is taken)
The convergence value of CB) is equal to the area ABCD and the area ADK in FIG.
H and the area HKEF can be determined in which area. Therefore, the UDC when the WB adjustment is completed
It is possible to determine the type of illumination based on the values of R and UDCB.

FIG. 8 shows UDCR and UDC in WB adjustment.
FIG. 9 is a diagram illustrating an example of a change and convergence of a value of B. This FIG.
Are initial values WBR0, WBB0 of UDCR, UDCB.
(Refer to step S1 in FIG. 6) (UDCR, UDCB)
= (WBR0, WBB0) = (140, 140) (FIG. 7)
And S = 1 in FIG. 8, and i = 1 (step S in FIG. 6).
4 and S5), j = 1 (see steps S7 and S8 in FIG. 6), and when the WB adjustment operation in FIG. 6 (steps S2 to S8 in the WB adjustment step WBS in FIG. 6) is repeated 20 times, UDCR, UDCB value is (UDCR, UDCB)
= (160, 160) (point P in FIG. 8), showing that the values of UDCR and UDCB converge to (UDCR, UDCB) = (160, 160) in the WB adjustment operation for the 20th and subsequent times. It is. At this time, it can be understood that the illumination used for the photographing is a white fluorescent lamp or illumination having a color rendering property similar to that of the white fluorescent lamp.

In the imaging apparatus according to the first embodiment, the matrix coefficient b according to the values of UDCR and UDCB for WB adjustment
11, b12, b21, and b22 are corrected. More specifically, the adjustment range is divided into a plurality of areas, and (UDCR, U
DCD) is located in which area, and (UD)
The matrix coefficients b11, b12, b21, and b22 are corrected in accordance with the area where (CR, UDCB) is located.

FIG. 9 is a diagram showing an example of the area division of the adjustment range of the UDCR and UDCB in the imaging apparatus according to the first embodiment of the present invention. In FIG. 9, the area ABCDEF is set as the adjustment range (the same as FIG. 7), and this adjustment range is set to the area a, the area b, the area c, and the area s (= the area ABCDP).
Q). In FIG. 9, the color rendering properties of the illumination deteriorate in the order of the area s → the area a → the area b → the area c. The data on the adjustment range and the areas a, b, c, and s are set in advance in the arithmetic unit 7A. The calculation means 7A indicates that (UDCR, URCB) is the area a,
It is determined whether it is located in any one of the areas b, c, and s. If it is located in any one of the areas a, b, and c, the matrix coefficient b11 is set to a correction value corresponding to the area. ,
b12, b21, and b22 are corrected. The operation means 7
A is a matrix coefficient b11, b12, b21, b2 if (UDCR, URCB) is located in the area s.
2 is not corrected with the initial value.

FIG. 10 is a diagram showing an example of the correction values of the matrix coefficients corresponding to the regions a, b, and c of FIG. 9 in the imaging apparatus according to the first embodiment of the present invention. As shown in FIG. 10, when the value of (UDCR, URCB) is located within the area a, the calculating means 7A adds the correction value Δb11 = “+ 2” to the initial value of the matrix coefficient b11 and adds the correction value Δb11 = “+ 2” to the initial value of b12. The correction value Δb12 = “0” is added (b12 is not corrected and the initial value is maintained), and the correction value Δb21 =
“−1” is added, and the correction value Δb22 =
“0” is added (b22 is not corrected and the initial value is kept), and these corrected matrix coefficients b11 and b1 are added.
2, b21 and b22 are output to the matrix means 8c.
When the value of (UDCR, URCB) is located in the region b, the calculating means 7A adds the correction value Δb11 = “+ 4” to the initial value of the matrix coefficient b11, and the correction value Δb12 = “0” is added (b12 is not corrected and the initial value is kept), and the correction value Δ is added to the initial value of b21.
b21 = “− 2” is added, and the correction value Δ is added to the initial value of b22.
b22 = “0” is added (b22 is not corrected and the initial value is maintained), and these corrected matrix coefficients b1
1, b12, b21 and b22 are output to the matrix means 8c. Further, the arithmetic means 7A includes (UDCR, URC
When the value of B) is located in the area c, the matrix coefficient b
The correction value Δb11 = “+ 6” is added to the initial value of 11, and b
The correction value Δb12 = “+ 1” is added to the initial value of “12”, and b
The correction value Δb21 “−3” is added to the initial value of 21 and b2
The correction value Δb22 = “0” is added to the initial value of 2 (b22
Are not corrected and the initial values are kept), and the corrected matrix coefficients b11, b12, b21 and b22 are output to the matrix means 8c. (UDCR, URC
When the value of B) is not located in any of the areas a, b, and c, that is, the area s (= area ABCDPQ) in FIG.
Is located within the matrix coefficient b, the calculating means 7A
The initial values of 11, b12, b21, b22 are output to the matrix means 8c.

The matrix correction step MCS (steps S9 to S14) in FIG. 6 will be described below. First,
In step S9, the calculating means 7A determines (UDCR,
URCB) is located in the area a in FIG. If it is not located in the area a, the process proceeds to step S11. If it is located in the area a, the calculation means 7A determines in step S10 that the matrix coefficients b11, b12, b21, b22 set in advance.
Is added to or subtracted from the initial value of (i.e., the correction value of the area a shown in FIG. 10), and the corrected matrix coefficients b11, b12, b21, and b22 are output to the matrix means 8c, and the WB adjustment step WBS Step S2
Return to

In step S9, (UDCR, URC
If B) is not located in the area a, step S11
In, the arithmetic means 7A determines whether or not (UDCR, URCB) is located in the area B of FIG. And
If it is not located in the area b, the process proceeds to step S13. If it is located in the area b, the calculation means 7A
In step S12, the individual correction values (for example, the correction value of the area b shown in FIG. 10) are added to and subtracted from the initial values of the matrix coefficients b11, b12, b21, and b22 set in advance, and the correction is performed. Matrix coefficient b1
1, b12, b21, and b22 are output to the matrix means 8c, and the process returns to step S2 of the WB adjustment step WBS.

In the above step S11, (UDCR, URC
If B) is not located in the area b, step S13
In 7, the calculation means 7A determines whether (UDCR, URCB) is located within the area c in FIG. And
If it is not located in the area c, that is, if it is located in the area s, the calculating means 7A will use the matrix coefficients b11,
The initial values of b12, b21 and b22 are stored in the matrix unit 8c.
And returns to step S2 of the WB adjustment step WBS. If it is located in the area c, the calculation means 7A
In step S14, the individual correction values (for example, the correction value of the area c shown in FIG. 10) are added to and subtracted from the initial values of the matrix coefficients b11, b12, b21, and b22 set in advance, and the correction is performed. Matrix coefficient b1
1, b12, b21, and b22 are output to the matrix means 8c, and the process returns to step S2 of the WB adjustment step WBS.

R (Red) when imaged under sunlight,
When Ye (Yellow) has the color reproducibility shown in FIG. 11, the color reproducibility of R and Ye when an image is captured under a white fluorescent lamp is as shown in FIG. In general, illuminations with poor color rendering have reduced redness, increased yellowness or greenish color reproduction. Therefore, the gains (U, R) of the R and B signals when the WB adjustment is completed under a white fluorescent lamp having the color reproducibility shown in FIG.
DCR, URCB) is located in the region b of FIG. 9, the matrix coefficient b11 corresponding to the gain of the RY signal
Is corrected to be large, and the matrix coefficient b22 corresponding to the gain of the BY signal is corrected to be small, so that the color reproduction shown in FIG. 12 can be made closer to the color reproduction shown in FIG. The color reproducibility can be corrected so as to improve the color rendering.

As described above, according to the first embodiment, a new external sensor is provided by correcting the matrix coefficients b11, b12, b21, and b22 according to the R and B signal gain values UDCR and UDCB of the WB adjustment. Without this, the color reproducibility can be properly corrected according to various illuminations including the illumination with poor color rendering properties, and an image with good color reproducibility can be obtained. Further, as compared with the case where an external sensor is provided, it is possible to reduce the size of the device and increase the degree of freedom in design, and to reduce the cost.

In the first embodiment, as shown in FIG. 9, the adjustment ranges of the gains (UDCR, URCB) of the R and B signals are divided into four areas a, b, c, and s. Even if the adjustment range is divided into two, three, or five or more regions, the same effect can be obtained. The matrix correction values Δb11, Δb12, Δb21, Δb22 are also calculated for the matrix coefficients b11, b12, b21, b2.
Instead of adding / subtracting the initial value of 2, it is also possible to multiply / divide the initial value. However, it goes without saying that the correction by addition and subtraction reduces the processing load on the arithmetic means 7A.

Embodiment 2 As explained above, TT
In the L-type WB adjustment, an error occurs in the WB adjustment when the subject is a single color or when a specific color occupies most of the subject. For this reason, in the imaging apparatus according to the first embodiment employing the TTL WB adjustment, the accuracy of the WB adjustment is increased by limiting the UDCR and UDCB adjustment ranges in the WB adjustment. But Iris 1
When the aperture ratio of “a” is small or the imaging magnification of the subject is high, even if the adjustment range of UDCR and UDCB is limited, W
The accuracy of the B adjustment may be reduced, and the accuracy of the color reproducibility may be reduced in the imaging device of the first embodiment due to the reduced accuracy of the WB adjustment.

Therefore, the imaging apparatus according to the second embodiment is different from the imaging apparatus according to the first embodiment in that the UD adjustment UDC
A matrix correction value Δb11 corresponding to the values of R and UDCB,
By correcting Δb12, Δb21, Δb22 (see FIG. 10) according to the aperture ratio of the iris 1a, or according to the imaging magnification of the subject, or according to the aperture ratio of the iris 1a and the imaging magnification of the subject, Iris 1
This is characterized in that erroneous correction of color reproducibility is prevented when the aperture ratio a is small or when the imaging magnification of the subject is high. In other words, the imaging apparatus according to the second embodiment performs the WB adjustment according to the UDCR and UDCB values and the aperture ratio of the iris 1a, or the WB adjustment UDCR and UDCB values and the imaging magnification, or the WB adjustment UDCR ,
Matrix coefficients b11, b12, b21, b according to the value of UDCB, the aperture ratio of iris 1a, and the imaging magnification
Correction of 22 prevents erroneous correction of color reproducibility when the aperture ratio of the iris 1a is small or when the imaging magnification of the subject is high.

FIG. 13 is a configuration diagram of an imaging apparatus according to the second embodiment of the present invention. In FIG. 13, reference numeral 1A denotes a lens unit, 1c denotes a sensor, and 7B denotes a calculation means, and the same components as those in FIG. As described above, the imaging device according to the second embodiment differs from the imaging device according to the first embodiment (see FIG. 1) in that the lens unit 1 is replaced by the lens unit 1A.
And the arithmetic means 7A is changed to the arithmetic means 7B.

The lens unit 1A is obtained by adding a sensor 1c to the lens unit 1 of FIG. The sensor 1c is a sensor that detects the aperture ratio of the iris 1a, and outputs a voltage signal corresponding to the aperture ratio of the iris 1a to the calculation unit 7B. This sensor 1c is a lens unit 1
A, and can be realized by, for example, a Hall element.

The calculating means 7B is different from the calculating means 7A of the first embodiment in that the UDCR and UDCB values of the WB adjustment and the aperture ratio of the iris 1a or the UDCR and UDCB values of the WB adjustment and the imaging magnification are used. Depending on,
Alternatively, the matrix coefficients b11, b12, b21, and b22 are corrected according to the UDCR and UDCB values of the WB adjustment, the aperture ratio of the iris 1a, and the imaging magnification. The calculating means 7B can recognize the aperture ratio of the iris 1a from the signal input from the sensor 1c. The arithmetic means 7B is provided with a zoom lens driver 12
Since the zoom lens 1d is driven by sending a control signal to the zoom lens 1d, the position of the zoom lens 1d can be recognized by the control signal, and the imaging magnification of the subject can be recognized from the position of the zoom lens 1d.

First, a matrix correction procedure according to the UDCR and UDCB values of the WB adjustment and the aperture ratio of the iris 1a will be described below. The calculating means 7B includes the sensor 1
c, the aperture ratio of the iris 1a can be recognized, and the UDC as shown in FIG.
Matrix correction values Δb11, Δb12, Δb21, Δb22 for each of the R and UDCB adjustment ranges are provided in advance. Further, the calculating means 7B calculates L
It has a UT (Look Up Table). LUT of FIG.
In, the coefficient I is determined in advance such that the value decreases as the aperture ratio of the iris 1a increases (as the F-number decreases).

The calculating means 7B obtains a coefficient I corresponding to the aperture ratio of the iris 1a from the LUT of FIG. 14, and uses the obtained coefficient I to calculate the matrix correction values Δb11, Δb12, Δb12
The following equation is applied to b21 and Δb22. Δb11 ← Δb11 / I (8) Δb12 ← Δb12 / I (9) Δb21 ← Δb21 / I (10) Δb22 ← Δb22 / I (11)

In the TTL adjustment of the TTL system, the iris 1a
When the aperture ratio of the WB is small, the accuracy of WB adjustment may be reduced even if the adjustment range of UDCR and UDCB is limited. On the other hand, in the imaging apparatus according to the second embodiment, as can be seen from Equations (8) to (11), the matrix correction values Δb11 to Δb22 are changed as the aperture ratio of the iris 1a decreases (as the iris 1a closes). ), Small value. That is, when (UDCR, UDCB) is located in the area a in FIG. 9, when it is located in the area b, and when it is located in the area c, the iris 1
As the aperture ratio of a becomes smaller, the matrix coefficients b11 to
The correction amount of b22 is reduced. Generally, the illuminance of a subject under artificial light such as a fluorescent lamp or a mercury lamp is smaller than the illuminance of the subject under sunlight. Therefore, the iris 1a
The closer to, the higher the possibility of shooting under sunlight. No correction of the matrix coefficient is required under sunlight.
Therefore, in the imaging apparatus according to the second embodiment, the correction amount of the matrix coefficient is reduced as the iris 1a is closed, thereby preventing erroneous color correction due to a decrease in the accuracy of WB adjustment.

Next, a matrix correction procedure according to the values of UDCR and UDCB for WB adjustment and the imaging magnification will be described below. The arithmetic means 7B can recognize the imaging magnification of the subject by the control signal sent to the zoom lens driver 12, and also has the UDCR, U as shown in FIG.
Matrix correction value Δb1 for each DCB adjustment range area
1, Δb12, Δb21, Δb22 are provided in advance. Further, the calculating means 7B includes the LUT shown in FIG. In the LUT of FIG. 15, the coefficient z is predetermined so that its value increases as the imaging magnification (ZOOM ratio) increases.

The calculating means 7B obtains a coefficient z corresponding to the imaging magnification from the LUT of FIG. 15, and uses the obtained coefficient z to
Matrix correction values Δb11, Δb12, Δb21, Δb
22 is subjected to the operation shown in the following equation. Δb11 ← Δb11 / z (12) Δb12 ← Δb12 / z (13) Δb21 ← Δb21 / z (14) Δb22 ← Δb22 / z (15)

As the imaging magnification of the subject increases,
Since only a part of the subject is imaged, there is a high possibility that a single color occupies the majority. For this reason, in the TTL adjustment of the WB method, if the imaging magnification of the subject increases, the UD
Even if the adjustment range of CR and UDCB is limited, the accuracy of WB adjustment may decrease. On the other hand, in the imaging apparatus according to the second embodiment, as can be seen from Equations (12) to (15), the matrix correction values Δb11 to Δb22 decrease as the imaging magnification increases. That is, (U
DCR, UDCB) are located in the area a in FIG.
In each of the case where it is located in the area b and the case where it is located in the area c, the correction amount of the matrix coefficients b11 to b22 is reduced as the imaging magnification increases, so that erroneous color correction due to a decrease in the accuracy of WB adjustment can be prevented. Preventing.

Next, a matrix correction procedure according to the UDCR and UDCB values of the WB adjustment, the aperture ratio of the iris 1a, and the imaging magnification will be described below. Calculation means 7
B can recognize the aperture ratio of the iris 1a by a signal input from the sensor 1c, can recognize the imaging magnification of the subject by a control signal sent to the zoom lens driver 12, and has a UDC as shown in FIG.
Matrix correction values Δb11, Δb12, Δb21, Δb22 for each of the R and UDCB adjustment ranges are provided in advance. Further, the calculating means 7B includes a LUT of a coefficient I for the aperture ratio of the iris 1a (see FIG. 14) and a LUT of a coefficient z for the imaging magnification (see FIG. 15).
And

The calculating means 7B obtains a coefficient I corresponding to the aperture ratio of the iris 1a from the LUT of FIG. 14, and obtains a coefficient z corresponding to the imaging magnification from the LUT of FIG. 15, using the obtained coefficients I and z. And the matrix correction value Δb1
The following equation is applied to 1, Δb12, Δb21, and Δb22. Δb11 ← Δb11 / (I × z) (16) Δb12 ← Δb12 / (I × z) (17) Δb21 ← Δb21 / (I × z) (18) Δb22 ← Δb22 / (I × z) (( 19)

As can be seen from equations (16) to (19),
The matrix correction values Δb11 to Δb22 are
As the aperture ratio becomes smaller and the imaging magnification increases, the value becomes smaller. That is, (UDCR, UDCB)
Are located in the area a, the area b, and the area c in FIG. 9, the matrix coefficients b11 to b11 decrease as the aperture ratio of the iris 1a decreases and the imaging magnification increases. By reducing the correction amount of b22, erroneous color correction due to a decrease in the accuracy of WB adjustment is prevented.

As described above, according to the second embodiment, the matrix coefficients b11 and b1 are determined according to the R and B signal gain values UDCR and UDCB of the WB adjustment and the aperture ratio of the iris 1a.
2, b21 and b22, the iris 1
Even when the aperture ratio of “a” is small, it is possible to prevent the accuracy of the WB adjustment from lowering. Therefore, it is possible to prevent erroneous correction of the color reproducibility due to the lowering of the accuracy of the WB adjustment, and to obtain an image with good color reproducibility. it can. Also, R and B signal gain values UD for WB adjustment
By correcting the matrix coefficients b11, b12, b21, and b22 in accordance with the CR, UDCB, and the imaging magnification of the subject, it is possible to prevent a decrease in the accuracy of WB adjustment even when the imaging magnification is large. An erroneous correction of color reproducibility due to a decrease in accuracy can be prevented, and an image with good color reproducibility can be obtained.

In the second embodiment, equations (8) to (8)
As shown in (15), the matrix correction values Δb11 to Δb2
2 was divided by a coefficient I corresponding to the aperture ratio of the iris 1a and a coefficient z corresponding to the imaging magnification, but the matrix correction value Δ
It is also possible to add and subtract coefficients I and z to b11 to Δb22. Where ULT of coefficient I and ULT of coefficient z
Must be configured to support addition and subtraction. It goes without saying that the correction by addition and subtraction reduces the processing load on the arithmetic means 7B.

Embodiment 3 FIG. 16 is a configuration diagram of an imaging device according to Embodiment 3 of the present invention. In FIG.
7C is an operation means, and the same components as those in FIG. 13 are denoted by the same reference numerals. As shown in FIG. 16, the imaging device according to the third embodiment is different from the imaging device according to the second embodiment (see FIG. 13) in that the arithmetic means 7B is used as the arithmetic means 7C and the imaging signal integrating means 10 and the iris control means 11 are used. In this case, the iris driver 3 is deleted and is controlled by the arithmetic means 7C.

The calculating means 7C is different from the calculating means 7B of the second embodiment in that the integrated value に よ る
R, ΣG, brightness L of the image taken from ΣB (for example,
L = ΣR + ΣG + ΣB) is calculated, and a control signal is output to the iris driver 3 so that the value of L, that is, the average image level (APL) becomes a predetermined constant level, and the iris 1a is opened and closed by the iris driver 3. . In the imaging device according to the third embodiment, the same effect as that of the imaging device according to the second embodiment can be realized with respect to color reproducibility.

As described above, according to the third embodiment, by controlling the iris driver 3 by the arithmetic means 7C, the imaging signal integrating means 10 and the iris control means 11
Can be deleted, and the device configuration can be simplified.

It is also possible to apply the arithmetic means 7C of the third embodiment to the first embodiment and control the iris driver 3 by the arithmetic means 7A.

Embodiment 4 FIG. 17 is a configuration diagram of an imaging device according to Embodiment 4 of the present invention. In FIG. 17, 7D
Denotes arithmetic means, 8A denotes signal processing means, and 8f denotes matrix means, and the same elements as those in FIG. 16 are denoted by the same reference numerals. As shown in FIG. 17, the imaging device according to the fourth embodiment differs from the imaging device according to the third embodiment (see FIG. 16) in that the arithmetic unit 7C is an arithmetic unit 7D and the signal processing unit 8 is a signal processing unit 8A. Things. The signal processing means 8A is the same as the signal processing means 8 of the third embodiment except that the matrix means 8c is replaced by the matrix means 8f and the adder / subtractor 8d is omitted.

The matrix means 8f is provided in the first embodiment.
Unlike the matrix means 8c (see FIGS. 1 and 2), the input color signals R, G, and B are converted into RY signals and BY signals by a matrix operation shown in the following equation (20). These RY signals and BY signals are output to the encoder 8g.

(Equation 5) In the equation (20), c11, c12, c13, c2
1, c22 and c23 are matrix coefficients. These matrix coefficients c11, c12, c13, c21, c2
2 and c23 are variable values input from the calculating means 7D. The matrix unit 8f converts the WB-adjusted color signals R, G, and B by a matrix operation using a matrix coefficient from the operation unit 7D into a color difference signal (here, R-
(Y signal and BY signal). Note that it is also possible to generate a U signal and a V signal in the matrix means 8f.

FIG. 18 is a diagram showing a configuration example of the matrix means 8f. In FIG. 18, the matrix means 8f
Is realized by multipliers 8p, 8q, 8r, 8s, 8t, 8u and adder / subtracters (adders) 8v, 8w. The matrix means 8f includes an RG signal and a BG signal.
A signal is input, and the matrix coefficients c11, c12, c13, c21, c22, c shown in equation (20) are input.
The signal corresponding to 23 is input from the calculating means 7D.

The multiplier 8p multiplies the R signal by the signal c11 and outputs the result to the adder 8v. The multiplier 8q multiplies the G signal by the signal of c12 and outputs the result to the adder 8v. The multiplier 8r multiplies the B signal by the signal of c13 and outputs the result to the adder 8v. The adder 8v adds the signal input from the multiplier 8p, the signal input from the multiplier 8q, and the signal input from the multiplier 8r, and generates an RY signal.

The multiplier 8s multiplies the R signal by the signal of c21 and outputs the result to the adder 8w. The multiplier 8t
The G signal is multiplied by the signal of c22 and output to the adder 8w. The multiplier 8u multiplies the B signal by the signal of c23,
Output to the adder 8w. The adder 8w includes a signal input from the multiplier 8s, a signal input from the multiplier 8t,
The signal input from the multiplier 8u is added to generate a BY signal.

The calculating means 7D is different from the calculating means 7C of the first embodiment in that the UDCR and UDCB values of the WB adjustment and the aperture ratio of the iris 1a or the UDCR and UDCB values of the WB adjustment and the imaging magnification are used. Depending on,
Alternatively, the matrix coefficients c11, c12, c13, c21, c22, and c23 are corrected according to the UDCR and UDCB values of the WB adjustment, the aperture ratio of the iris 1a, and the imaging magnification.

UDC in Imaging Device of Fourth Embodiment
The adjustment ranges and the area divisions of R and UDCB are the same as those of the imaging apparatus according to the first embodiment.
b, c, and s. FIG. 19 is a diagram illustrating an example of a correction value of a matrix coefficient corresponding to the regions a, b, and c in FIG. 9 in the imaging device according to the fourth embodiment of the present invention.

The arithmetic means 7D can recognize the aperture ratio of the iris 1a by the signal input from the sensor 1c, and can recognize the imaging magnification of the object by the control signal sent to the zoom lens driver 12.
As shown in FIG. 19, the matrix correction values Δc11, Δc12, and Δc1 for each region section of the UDCR and UDCB adjustment ranges.
3, Δc21 and Δb12 are provided in advance. Further, the calculating means 7D includes an LUT of a coefficient I for the aperture ratio of the iris 1a (see FIG. 14) and an LUT of a coefficient z for the imaging magnification (see FIG. 15).

The calculating means 7D is the same as the calculating means 7A of the first embodiment (steps S9 and S1 in FIG. 6).
1, S13), R, B signal gain (UD
CR, UDCB) is located in which region of FIG. Further, a coefficient I for the aperture ratio of the iris 1a and / or a coefficient z for the imaging magnification are obtained from the LUT of FIG. 14 or / and FIG. Further, the matrix correction values Δc11 to Δc23 (see FIG. 19) corresponding to the area where (UDCR, UDCB) is located are calculated in the same manner as the calculation means 7B of the second embodiment (Equation (7)). To (19)), a correction operation using the coefficient I or / and the coefficient z is performed. Then, the matrix correction value Δc obtained by performing the above-described correction calculation is performed in the same manner as the calculation unit 7A of the first embodiment (similarly to steps S10, S12, and S14 in FIG. 6).
By adding and subtracting 11 to Δc23 to and from the initial values of the matrix coefficients c11 to c23, respectively, the matrix coefficient c
11 to c23, and the corrected matrix coefficient c
11 to c23 are output to the matrix means 8f. Accordingly, the same effect as that of the imaging device according to the second embodiment can be achieved with respect to color reproducibility.

As described above, according to the fourth embodiment, the input color signals R, G, and B are converted into color difference signals (RY) by the matrix operation using the matrix coefficients from the operation means 7D.
Matrix means 8f for directly converting the
Is provided, the adder / subtractor 8d (see FIG. 16) can be omitted, and the device configuration can be simplified.

The signal processing device 8 of the fourth embodiment
A and the arithmetic means 7D can be applied to the first or second embodiment.

[0102]

As described above, according to the image pickup apparatus of the first aspect of the present invention, the matrix coefficient is corrected in accordance with the first and second signal gain values of the white balance adjustment, so that a new external device can be obtained. Without providing a sensor, color reproducibility can be properly corrected according to various illuminations including illumination with poor color rendering properties, and an effect that an image with good color reproducibility can be obtained. Further, as compared with the case where an external sensor is provided, there is an effect that the size of the device and the degree of freedom in design can be increased, and the cost can be reduced.

According to the image pickup apparatus of the second aspect,
By correcting the matrix coefficient in accordance with the first and second signal gain values of the white balance adjustment and the iris aperture ratio, it is possible to prevent a decrease in the white balance adjustment accuracy even when the iris aperture ratio is small. Therefore, it is possible to prevent an erroneous correction of color reproducibility due to a decrease in accuracy of white balance adjustment, and to obtain an image having good color reproducibility.

According to the image pickup apparatus of the third aspect,
By correcting the matrix coefficient according to the first and second signal gain values of the white balance adjustment and the imaging magnification of the subject, it is possible to prevent a decrease in the accuracy of the white balance adjustment even when the imaging magnification is large. In addition, it is possible to prevent an erroneous correction of color reproducibility due to a reduction in accuracy of white balance adjustment, and to obtain an image with good color reproducibility.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an imaging device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a matrix unit in the imaging device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of spectral sensitivity characteristics of an image sensor for R, G, and B components.

FIG. 4 is a diagram illustrating an example of spectral characteristics of illumination having good color rendering properties, such as a halogen lamp and sunlight.

FIG. 5 is a diagram illustrating an example of spectral characteristics of illumination having poor color rendering properties represented by a fluorescent lamp.

FIG. 6 is a flowchart illustrating a procedure for correcting color reproducibility in the imaging apparatus according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between values of UDCR and UDCB and types of illumination (light source), and an adjustment range of UDCR and UDCB.

FIG. 8 is a diagram illustrating an example of changes and convergence of values of UDCR and UDCB in WB adjustment.

FIG. 9 is a diagram showing a U in the imaging apparatus according to the first embodiment of the present invention.
It is a figure showing an example of the field division of the adjustment range of DCR and UDCB.

FIG. 10 is a diagram illustrating an example of a correction value of a matrix coefficient according to a region division of a UDCR and UDCB adjustment range in the imaging device according to the first embodiment of the present invention. .

FIG. 11 is a diagram showing the color reproducibility of R and Ye under sunlight having good color rendering properties.

FIG. 12 is a diagram showing the color reproducibility of R and Ye under a white fluorescent lamp with poor color rendering properties and the correction of the color reproducibility of R and Ye according to the first embodiment of the present invention.

FIG. 13 is a configuration diagram of an imaging device according to a second embodiment of the present invention.

FIG. 14 is a diagram illustrating an LUT of a correction coefficient I of a matrix correction value according to an iris aperture ratio.

FIG. 15 is a diagram illustrating an LUT of a correction coefficient z of a matrix correction value according to an imaging magnification.

FIG. 16 is a configuration diagram of an imaging device according to a third embodiment of the present invention.

FIG. 17 is a configuration diagram of an imaging device according to a fourth embodiment of the present invention.

FIG. 18 is a configuration diagram of a matrix unit in the imaging device according to the fourth embodiment of the present invention.

FIG. 19 is a diagram illustrating an example of a correction value of a matrix coefficient according to an area division of an adjustment range of UDCR and UDCB in the imaging apparatus according to Embodiment 4 of the present invention.

FIG. 20 is a configuration diagram of a conventional imaging device.

FIG. 21 is a configuration diagram of a conventional imaging device that improves color reproducibility.

[Explanation of symbols]

1 lens unit, 1a iris, 1b lens system, 1c sensor, 1d zoom lens, 2
Imaging device 3 iris driver 4 timing generator (TG) 5 pre-signal processing means 6
A / D converter, 7A, 7B, 7C, 7D calculation means, 8, 8A signal processing means, 8a color separation means, 8b white balance adjustment means (WB adjustment means), 8c matrix means, 8d adder / subtracter, 8
e color signal integrating means, 8f matrix means, 8g
Encoder, 8h, 8i, 8j, 8k multiplier,
8l, 8m adder / subtracter, 8p, 8q, 8r, 8s, 8
t, 8u multiplier, 8v, 8w adder / subtracter, 8ba,
8bb, 8bc gain control means, 9 output terminals, 10
Imaging signal integration means, 11 iris control means, 1
2 Zoom lens driver.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) // H04N 101: 00 H04N 1/46 A (72) Inventor Akihisa Miyata 2-2-2 Marunouchi, Chiyoda-ku, Tokyo No. 3 Mitsubishi Electric Co., Ltd. (72) Inventor Tetsuya Hayashi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 5B057 BA02 BA19 CA01 CA12 CB01 CB12 CD14 DB02 DB06 5C065 AA01 AA03 BB02 CC01 DD01 EE12 GG15 GG18 GG21 GG22 GG24 5C066 AA01 EA14 EE04 GA01 GB03 KA12 KE02 KE03 KE04 KE19 KM01 5C077 MM02 MP08 PP20 PP32 PP34 PP37 PP68 PQ12 SS03 TT09 5C079 HB01 MA03NA03 NA11

Claims (3)

[Claims] 1. An image sensor for converting an optical image of a subject into an image signal, a lens unit for forming the optical image on the image sensor, and first, second, and third color signals from the image signal. Color separation means for separating the first color signal and the first color signal according to the first signal gain value, and adjusting the signal level of the second color signal according to the second signal gain value. White balance adjusting means for adjusting the white balance so that the signal levels of the second and third color signals are equal to each other, and calculating the integrated values of the first, second and third color signals subjected to the white balance adjustment, respectively. Integrating means for outputting the first and second signal gain values to the white balance adjusting means so that the integrated values become equal to each other; and a matrix operation using matrix coefficients from the arithmetic means. Ri, and a converting means for converting the color signal adjusted the white balance color-difference signal, the calculating means, the image pickup apparatus characterized by correcting the matrix coefficients in response to the signal gain value. 2. The apparatus according to claim 1, wherein the lens unit includes an iris for adjusting an amount of light incident on the image sensor, and a sensor for detecting an aperture ratio of the iris. 2. The imaging device according to claim 1, wherein the matrix coefficient is corrected according to the following. 3. The lens unit has means for changing an imaging magnification of a subject according to a control signal from the arithmetic means, and the arithmetic means corrects a matrix coefficient according to the signal gain value and the imaging magnification. The imaging device according to claim 1, wherein: