JPH03110991A - Color image pickup device - Google Patents

Abstract

PURPOSE:To attain proper white balance adjustment automatically even when a color temperature of an incident light differs by controlling the gain of an amplifier means based on a stored reference value and data, a detection output of a color temperature detection means and a detection output of an average level detection means. CONSTITUTION:A microcomputer 22 reads the result of calculation of differential amplifiers 12, 13, proper R-Y control signal voltage and B-Y control signal voltage in each of cases when color temperature of a lighting light are 3200K and 5000K stored in an EEPROM 23 to calculate proper R-Y control signal voltage and B-Y control signal voltage at the current color temperature of the lighting light. Then the microcomputer 22 outputs digital value representing two introduced control voltages R-YNOW and B-YNOW to a D/A converter 21. Thus, when the white valance is adjusted to a value in following to the actual color temperature of the light, the processing by the microcomputer 22 is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color imaging device, and more particularly to a color imaging device having an improved white balance function.

[Prior Art] A color imaging device such as a color video camera has a white balance function for displaying a subject on a screen in the same color as seen by the human eye.

Human eyes perceive a white object as white, regardless of changes in the color temperature of the illumination light of the object to be viewed. However, the color of an object captured by a color imaging device becomes more bluish as the color temperature of the illumination light is higher, and becomes more reddish as the color temperature of the illumination light is lower. In other words, the color perceived by the color imaging device and the color perceived by the human eye differ depending on the color temperature of the illumination light.

Therefore, color imaging devices are equipped with a white balance function that detects the color temperature of the illumination light of the subject and automatically adds correction according to the detected color temperature to the color information obtained by imaging the subject. .

FIG. 6 is a schematic block diagram of a conventional color video camera.

Referring to the figure, an image sensor 1 receives an image formed on a light receiving surface by reflected light from a subject (not shown) through a lens system (not shown), that is, an optical image of the subject, and converts it into an electrical signal. It is converted into and given to the processing circuit 2.

The processing circuit 2 generates a brightness signal representing the brightness of the subject based on the electrical signal output from the imaging probe 1.

Color difference signals R-Y and B-Y representing the color of the subject are created, and the encoder 5. to variable gain amplifiers 3 and 4, respectively.

Now, when the color temperature of the illumination light of the object changes, the color information obtained by imaging this object, that is, the color difference signal R-
Each average level of Y and BY changes. Therefore, regardless of changes in the color temperature of the illumination light, the average levels of the color difference signals R-Y and B-Y can be adjusted to
Variable gain amplifiers 3 and 4 are provided in order to maintain the color difference signals (color difference signals with a good white balance) R-Y and B-Y at the average level so that the color to be processed appears white. In other words, the variable gain amplifiers 3 and 4 constitute the white balance adjustment section 26.

The variable gain amplifier 3 outputs the color difference signal R-Y from the processing circuit 2 with a gain corresponding to a control signal (hereinafter referred to as R-Y control signal) output from a gain adjustment circuit 15, which will be described later.
is amplified to a predetermined average level and provided to the encoder 5.

Similarly, the variable gain amplifier 4 adjusts the color difference signal B-Y from the processing circuit 2 to a predetermined value with a gain corresponding to a control signal (hereinafter referred to as a B-Y control signal) output from a gain adjustment circuit 17, which will be described later. The signal is amplified to an average level of , and is provided to the encoder 5.

The encoder 5 synthesizes the luminance signal Y from the processing circuit 2 and the color difference signals R-Y and B-Y amplified by the variable gain amplifiers 3 and 4, respectively, and generates a color video signal that is the final camera output. The signal is output to a VTR (video tape recorder) or a monitor (receiver such as a home television), which is not shown. As a result, the color video signal output from the encoder 5 is recorded on a VTR or displayed as an image on a monitor. Note that the color difference signals output from the variable gain amplifiers 3 and 4 and the luminance signal output from the processing circuit 2 may not be combined and may be output separately to the outside.

On the other hand, this color video camera has three photodetectors 6, 7, . and 8. These three photodetectors 6, 7. and 8, receives external light, converts the red, green, and blue light components contained therein into electrical components, and outputs the electrical components.

The output signal R of the photodetector 6 is an electric signal representing a red light component contained in the external light; the output signal G of the photodetector 7 is an electric signal representing a green light component; and the blue light component. The output signals B of the photodetectors, which are electrical signals representative of , are respectively input to logarithmic amplifiers 9, 10, . and logarithmically amplified by 11.

As a result, the output signal R of the photodetector 6 is transmitted from the amplifier 9 to l.
A signal converted to a magnitude of ogR (here, R represents the magnitude of the output signal of the photodetector 6) is output, and the output signal G of the photodetector 7 is output from the amplifier 10 as logG (here, G represents the magnitude of the output signal of the photodetector 7), and the output signal B of the photodetector 8 is output from the amplifier 11 as 1ogB (here, B The signal converted to the magnitude of the output signal of the converter 8 is output.

The outputs of amplifiers 9 and 11 are applied to differential amplifiers 12 and 13, respectively, and the output of amplifier 10 is applied to differential amplifier 12.
and 13 in common.

Differential amplifier 12 performs a calculation to determine the difference between the outputs of amplifiers 9 and 10 by differentially amplifying them. That is, in the differential amplifier 12, the difference between the magnitude logR of the output signal of the amplifier 9 and the magnitude logG of the output signal of the amplifier 10, that is, log(R
/G) is derived.

Similarly, differential amplifier 13 performs a differential amplification operation on the outputs of amplifiers 10 and 11 to calculate the difference between them. That is, in the differential amplifier 12, the difference between the magnitude 1ogG of the output signal of the amplifier 10 and the magnitude logB of the output signal of the amplifier 11, that is,
log(G/B) is derived.

The calculation result log(R/G) in the differential amplifier 12 is
The offset adjustment circuit 1 is used as the output signal of the differential amplifier 12.
given to 4. The offset adjustment circuit 14 corrects the level of the output signal of the differential amplifier 12 based on a preset value of the output when the input is O, that is, the offset value. give to

The gain adjustment circuit 15 has a preset gain for the output of the offset adjustment circuit 14, and appropriately controls the amplitude of the output signal of the differential amplifier 12, which has been adjusted by offset yJ8, and the gain of the variable gain amplifier 3. (the gain is adjusted to suit the size) and applied to the variable gain amplifier 3 as the above-mentioned RY control signal.

Similarly, the calculation result in the differential amplifier 13 is 1°g (G
/B) is offset-adjusted by the offset adjustment circuit 16, then gain-adjusted by the gain adjustment circuit 17, and given to the variable gain amplifier 4 as the above-mentioned BY control signal.

Now, when the color temperature of the object's illumination light, which is external light, changes, the output signals of the photodetectors 6, 7° and 8 that detect the external light change, and as a result, predetermined arithmetic processing is performed on these signals. The differential amplifier 1, which is the signal obtained by
The output signals of 2 and 13 also change. That is, the outputs of the differential amplifiers 12 and 13 indicate color temperature information of the illumination light. In other words, the photodetectors 6, 7 . and 8, and amplifiers 9,1
0 and 11 and the differential amplifiers 12 and 13 constitute a color temperature detection section 24 that detects the color temperature of illumination light.

On the other hand, as described above, the offset adjustment circuits 14 and 1
6 and gain adjustment circuits 15 and 17 generate signals that control the variable gain amplifiers 3 and 4 forming the white balance adjustment section 26 based on the outputs of the differential amplifiers 12 and 13, which indicate color temperature information of the illumination light. create. In other words, the offset adjustment circuits 14 and 16 and the gain adjustment circuits 15 and 17 are connected to the white balance adjustment section 2.
A white balance adjustment control section 25b is configured to control the white balance adjustment control section 6.

Here, the offset value in the offset adjustment circuit 14 and the gain in the gain 5B adjustment circuit 15 are determined by the color difference signal RY from the processing circuit 2 in the variable gain amplifier 3.
The gain of the variable gain amplifier 3 is controlled so that the average level of R-Y is always corrected to a predetermined value (equal to the average level of the white-balanced color signal R-Y) regardless of the color temperature of the illumination light. A control signal is configured to be created. As a result, the white balance adjustment control section 2
The RY control signal outputted from the processing circuit 5b follows the change in the deviation of the average level of the color difference signal RY outputted from the processing circuit 2 from the predetermined value, that is, the color temperature change of the illumination light. In order to change the gain of the variable gain amplifier 3, the average level of the color difference signal RY input to the encoder 5 is always maintained at the predetermined value.

Similarly, the offset value in the offset adjustment circuit 16 and the gain in the gain 25g adjustment circuit 17 are set so that the average level of the color difference signal sy from the processing circuit 2 in the variable gain amplifier 4 is always a predetermined value regardless of the color temperature of the illumination light. (equal to the average level of the white-balanced color difference signal B-Y). As a result, the B-Y control signal output from the white balance control section 25b is adjusted to a change in the deviation of the color difference signal B-Y output from the processing circuit 2 from the predetermined value, that is, a change in the color temperature of the illumination light. Since the gain of the variable gain amplifier 4 is subsequently changed, the average level of the color difference signal B-Y input to the encoder 5 is always maintained at a predetermined value.

As mentioned above, in conventional color video cameras,
Color temperature detection section 24. White balance adjustment control section 25b
, and the function of the white balance adjustment section 26,
Color difference signals R-Y and B-Y are derived with white balance adjusted so as to project the same colors as the colors perceived by the human eye, and as a result, an image with good white balance is automatically obtained.

[Problems to be Solved by the Invention] As described above, white balance adjustment in a conventional color imaging device is based on the color difference signal R obtained by imaging a subject.
-Y and B-Y according to a control signal that is generated independently of Y and B-Y. On the other hand, this control signal is created based on the color temperature of light that enters a photodetector placed in front of the imaging device, similar to the imaging device. Therefore, if the color temperature of the light that enters the photodetector differs from the color temperature of the light that enters the image sensor, for example, when capturing an image of a subject outdoors from the shade to the sun, the white balance adjustment The control signal for controlling the image is created based on the color temperature in the shade, whereas the color difference signals R-Y and B-Y obtained by imaging the subject are created based on the color temperature in the sun.
It has a poor average level.

Therefore, in such a case, the color difference signal obtained by imaging the subject is corrected to correspond to a color temperature different from the color temperature of the illumination light of the actual subject. In other words, in the example shown in FIG. 6, the RY control signal and the B-
Variable gain amplifiers 3 and 4 by Y control signal
The gain becomes a value different from the value that should originally be taken. As a result, the average level of each of the corrected color difference signals R-Y and B-Y does not have a white balance,
The colors of the subject are not accurately reproduced in the reproduced image.

Furthermore, in the conventional color imaging device, the specification values of the white balance adjustment control unit that controls the white balance function unit, that is, the offset values in the offset adjustment circuits 14 and 16 in the example shown in FIG. 6, and the gain adjustment circuit 15 and The gain at 17 is manually adjusted by a human at the device manufacturing stage. Specifically, while changing the color temperature of the illumination light of the subject, a human adjusts the adjustment volume provided in the device in advance to set the above specification values, and produces a color difference signal that always maintains a white balance. The above specification values are set so that the following can be obtained. In this way, since the above specification values are set by humans, variations in the set values of these specification values cause variations in the white balance function of each device, and the labor costs for making this adjustment are increased by the imaging device. The cost is high.

An object of the present invention is to solve the above-mentioned problems, and to solve the problem in that the color temperature of illumination light of a subject is different from the color temperature of light incident on a photodetector for deriving a control signal for white balance adjustment. It is an object of the present invention to provide a color imaging device that can automatically perform appropriate white balance adjustment even in various cases, and eliminates the need to manually set the above-mentioned specification values.

[Means for Solving the Problems] In order to achieve the above objects, a color imaging device according to the present invention includes an imaging means for imaging a subject and deriving a color difference signal, and a color difference signal derived by the imaging means. gain controllable amplification means for amplifying the color difference signal; average level detection means for detecting the average level of the color difference signal amplified by the amplification means; color temperature detection means for detecting the color temperature of external light; A predetermined reference value for appropriate white balance, the color temperature of the illumination light of the object, and the gain of the amplification means necessary to bring the average level of the color difference signal amplified by the amplification means to the reference value. A gain of the amplification means is determined based on a storage means for storing data showing a correlation, a reference value and data stored in the storage means, a detection output of the color temperature detection means, and a detection output of the average level detection means. and gain control means for controlling.

[Function] Since the color imaging device according to the present invention is configured as described above, gain control of the amplification means for amplifying color difference signals is not performed based only on the detection output of the color temperature detection means; The average level of the color difference signal when the white balance is maintained (predetermined reference value for proper white balance) and the average level of the actual color difference signal amplified by the amplification means, elements that have not been considered in the past. is taken into consideration.

[Embodiment] FIG. 1 is a schematic block diagram of a color video camera according to an embodiment of the present invention.

Referring to the figure, this color video camera has an image sensor 1 similar to the conventional color video camera shown in FIG.
．． Processing circuit 2. Encoder 51 Negative star power detection unit 24. White balance style including the white balance adjustment control section 25a and the white balance adjustment section 26! i control section 25
The configuration and operation of the functional units except for a are similar to those in the conventional color video camera shown in FIG.

The white balance adjustment control unit 25a includes a low-pass filter 18 that detects the average level of the color difference signal R-Y by extracting the DC component of the color difference signal RY amplified by the variable gain amplifier 3, and a color difference t amplified by the variable gain amplifier 4. - a low-pass filter 19 that detects the average level by extracting the DC/DC component of No. It includes an A/D converter 20 that converts each average level and each output signal of the differential amplifiers 12 and 13, that is, the color temperature information of the illumination light of the object, into digital data and outputs the digital data. The white balance adjustment control section further includes the digital data and an EEFROM (Electrical Memory), which will be described later.
icallyErasabfe and Prog
rammable Read 0n1y Mem
A microcomputer (hereinafter referred to as a microcomputer) performs processing according to the processing flow described later based on the data stored in the microcomputer (ory) 23, derives appropriate R-Y control signal voltages and B-Y control signal voltages, and outputs them as digital signals. )22, EEPROM2
3, and a D/A converter 21 that converts the digital R-Y control signal and digital B-Y control signal obtained as a result of processing by the microcomputer 22 into analog signals and supplies them to the variable gain amplifiers 3 and 4, respectively. .

The EEPROM 2B has appropriate R- to output color difference signals R-Y and B-Y with the color temperature of the illumination light of the object and the white balance from the variable gain amplifiers 3 and 4, respectively.
The relationship between the Y control signal voltage and the B-Y control signal voltage is stored in advance by the following operation of the white balance adjustment control section 25a at the time of device manufacture.

First, the video camera is operated under illumination light having a reference color temperature for humans (3200 K in this case) so as to image a subject under the illumination light. In this initial state, the microcomputer 22 is set in advance to output digital signals corresponding to appropriate R-Y control signal voltages and B-Y control signal voltages under illumination light having the reference color temperature. As a result, variable gain amplifiers 3 and 4 have an appropriate R-
Although the Y control small signal and the B-Y control signal are respectively given, the color difference signals R-Y and B output from the variable gain amplifiers 3 and 4 may vary depending on various conditions.
- Each average level of Y deviates from a predetermined value (each average level of color difference signals R-Y and B-Y with white balance). Therefore, in this initial state, the color difference signals R-Y and B- output from the variable gain amplifiers 3 and 4 are
so that each average level of Y matches the predetermined value: 18
It will be arranged. This adjustment is manually performed by a person via an adjustment section (not shown) provided in advance in this video camera. When this adjustment is completed, the function of the white balance adjustment control section 25a is activated, and the microcomputer 22 operates according to a predetermined program.

The operation of the microcomputer 22 at this time will be explained with reference to FIG. FIG. 2 is a process flow diagram showing a series of processes performed by the microcomputer 22 at this time.

First, the microcomputer 22 determines the average levels of the color difference signals R-Y and B-Y, which are amplified by the variable gain amplifiers 3 and 4, respectively, and which are provided via the A/D converter 20.
That is, the low-pass filter 18 and one output (R
-Y)' and (B-Y)' and the outputs of the differential amplifiers 12 and 13 are sequentially written into the EEPROM 23. That is, each average level (R-Y)' of the color difference signals R-Y and B-Y amplified by the variable gain amplifiers 3 and 4
Color difference signals R-Y and B-Y when the digital data of and (B-Y)' are white balanced
The average level of (RY)' 3200 and (BY)'
3200 in the EEFROM 23 (processing steps S1 to S4). Next, differential amplifiers 12 and 13
The calculation results log(R/G) and log(G/
Calculation results log (R/G)a 200 and l in the differential amplifiers 12 and 13 when the digital data in B) has a color temperature of illumination light of 3200.

g (G/B) s 200 is written into the EEPROM 23 (processing steps 85 to S8).

Furthermore, the microcomputer 22 outputs the digital R-Y control signal and digital B that it is outputting at this time.
- Y control signal respectively, the color temperature of the illumination light is 32
Proper R-Y control signal R-Y at 00K,
2oo and B-Y control signal B-Y32oo to the EEFROM 23 (processing steps S9 and 510).

Next, the color temperature of the illumination light is changed from 3200K to 5000K, and the microcomputer 22 operates according to the following program. As a result, the microcomputer 22 adjusts the RY control signal and BY control signal provided to the variable gain amplifiers 3 and 4, respectively, so that white balance can be achieved again in this state. The operation of the microcomputer 22 at this time will be explained with reference to FIGS. 3 and 5.

FIG. 3 is a processing flow diagram showing the operation of the microcomputer 22 when the color temperature of illumination light is set to 5000K. FIG. 5 is a diagram showing the relationship between the color temperature of illumination light and appropriate R-Y control signal voltages and B-Y control signal voltages to be applied to variable gain amplifiers 3 and 4, respectively. Referring to FIG. 5(a), the appropriate R-Y control signal voltage (vertical axis) for obtaining a white-balanced color difference signal from the variable gain amplifier 3 indicates color temperature information of illumination light. Operation result log in differential amplifier 12
It increases in proportion to (R/G) (horizontal axis). Similarly, referring to FIG. 5(b), the appropriate Y control signal voltage (vertical axis) for obtaining a white-balanced color difference signal B-Y from the variable gain amplifier 4 is expressed as color temperature information. The calculation result of the differential amplifier 13 shown is log (G/B) (
tM axis).

When the color temperature of the illumination light is changed from 3200K to 5000K, the microcomputer 22 first outputs the digital R-Y control signal that it is outputting at that time, that is, the appropriate color temperature when the color temperature of the illumination light is 3200K. A digital value representing the R-Y control signal voltage is incremented by a predetermined amount (processing step 51).
1).

Thereafter, the microcomputer 22 uses the output (RY)' of the low-pass filter 18 provided via the A/D converter 20, that is, the R-Y control signal corresponding to the digital value incremented in the processing step Sll, to increase the gain. The average level of the color difference signal RY output from the controlled variable gain amplifier 3 is set as a variable (RY)'5ooo
(processing step 512). Next, microcomputer 2
2 is the average level (R-Y) of 3200 of the color difference signal R-Y obtained under the reference illumination light with the white balance stored in the EEPROM 2B.
Read from the ROM 23 and set the variable (RY)'s. It is determined whether it is equal to oo (step 513).

If the determination result in processing step 813 is "YES", that is, if the average level of the color difference signal R-Y currently output from the variable gain amplifier 3 is equal to that in the white balance state, the microcomputer 22 When the color temperature of the illumination light is 5000, the output digital R-Y control signal is set to the appropriate R-Y control signal.
- EEFROM as Y control signal Rysooo
(processing step 813).

However, the determination result in processing step 813 is “No.
", that is, if the average level of the color difference signal B-Y currently output from the variable gain amplifier 3 has not yet reached the value in a white balanced state, the microcomputer 22 starts from processing step Sll. In other words, by repeating the processing in processing steps Sll to 51B, the R-Y control signal voltage becomes the white-balanced color difference signal R- when the color temperature of the illumination light is 5000. The value is automatically adjusted to the value necessary to obtain Y and stored in the EEPROM 23.

Next, in processing steps 815 to S18, the microcomputer 22 performs the same processing as that performed in processing steps Sll to 814 on the BY control signal and the output (B-Y)' of the low-pass filter 19.

That is, the microcomputer 22 sets the variable (B-Y)'5ooo
The current output voltage of the low-pass filter 19 substituted into
The digital B-Y control signal that it outputs until it matches the digital value (B-Y) ' a 200 representing the average level of the color difference signal B-Y in a state where the white balance is maintained, which was previously stored in the EEPROM 2B. After adjusting the B-Y control signal voltage to the value required to obtain a white balanced color difference signal B-Y when the color temperature of the illumination light is 5000 by incrementing this value, E EPROM2
3.

Next, the microcomputer 22 inputs the differential amplifier 1 which is digitized and provided by the A/D converter 20 in this state.
Operation result l by 2 and 13.

Let g(R/G) and log(G/B) be log(R/B), each a value indicating that the color temperature of the proof light is 5000.
G) s a o o and log(G/B) sooo
(Processing step S)
19-522).

As described above, when the microcomputer 22 performs the processing according to the processing flow shown in FIGS. 2 and 3,
The color temperature information from the color temperature detection unit 24 and the appropriate R when the color temperature of the illumination light is 3200 and 5000, respectively.
-Y control signal and B-Y control signal,
And the average level of the color difference signals R-Y and B-Y from the variable gain amplifiers 3 and 4 in a white balanced state is stored in the EERPOM 23. In other words,
By storing two points A and B on the straight line in FIG. 5(a) and two points C and D on the straight line in FIG. 5(b) in the EEPROM 2B, the color temperature of the illumination light and The relationship between the appropriate gains of the variable gain amplifiers 3 and 4 is indirectly stored, and the average level of the color difference signals R-Y and B-Y to be output from the variable gain amplifiers 3 and 4 is also stored.

Next, the operation of the microcomputer 22 during actual shooting with this video camera will be explained with reference to FIG. FIG. 4 is a process flow diagram showing a series of processes performed by the microcomputer 22 during actual photographing.

First, the microcomputer 22 calculates the current calculation result log(R
/G) and l o g (G/B), respectively, as a variable l o g representing current color temperature information.
(R/G) N OV and l.

g (G/B) N Ow (processing step 823).

Next, the microcomputer 22 stores the EEPROM as described above.
23, the calculation results log(R/G) 3200 and log(G/B) i of the differential amplifiers 12 and 13 in the case where the color temperature of the illumination light is 3200 and 5000, respectively.

. . and the appropriate R-Y control signal voltage R-Y320
0 and B-Y control signal voltage B-YIQOO are read from the EEPROM 23, and these and the variable l o
g (R/G)N Ow and log(G/B)N
OV value and calculate the appropriate R-Y control signal voltage R-Y)ov and B-Y control signal voltage B at the current color temperature of illumination light by performing the calculation shown in the following formula.
-YNo, is calculated (processing step 524).

R-YN OW =(RYs　o　.

(R/G) N O log(R/G)s o R-Ya 20o)Xlog w　/(log(R/G)s　o　o　.

20 0 ) + RY3 20 0...
(1) B-Yi+ow=(B-Ys o o o [3-Y3200)
Xlog(G/I3) N ov /(
log(G)B>5 0 0 0 -1log(G/B)
a 2 (10) + R-Y3200... (2) The above formula (1) is expressed by the differential amplifier 1 in FIG. 5(a).
From the two points A and B on the straight line indicating the relationship between the calculation result 2 (R/G) and the appropriate R-Y control signal voltage, the current calculation result 10 of the differential amplifier 12 on the straight line is calculated. g (R/G) s. R- corresponding to 1
This is an operation for deriving the Y control signal voltage. Similarly, the above equation (2) is expressed by the differential amplifier 13 in FIG. 5(b).
The calculation result l.

From the two points C and D on the straight line showing the relationship between g (G/B) and the appropriate -Y control signal voltage, the current calculation result of the differential amplifier 13 on the straight line log
(G/B) This is an operation for deriving the B-Y control signal voltage corresponding to N Ow. That is, in processing step S24, the appropriate control voltage at the current color temperature of the illumination light is determined based on the relationship between the color temperature of the illumination light and the appropriate control voltage for the variable gain amplifiers 3 and 4, which is stored in the EEPROM 23 in advance. R-YNoW and B-yNo.

is derived.

Next, the microcomputer 22 uses the two control voltages RYNOW and BYNOV/ that were derived in processing step S24.
A digital value representing the value is output to the D/A converter 21 (
Process step 525). Therefore, the color temperature of the light incident on the image sensor 1 and the photodetectors 6, 7 . If the color temperature of the incident light on and 8 substantially matches, processing step S25
At the stage where the processing in is completed, the variable gain amplifiers 3 and 4 are controlled by the R-Y control signal and the B-Y control signal appropriate for the color temperature of the current illumination light provided via the D/A converter 21. It outputs color difference signals R-Y and B-Y with a well-balanced white balance.

However, as described above, when capturing an image of a subject in the sun from the shade, the color temperature of the light incident on the image sensor 1 and the photodetectors 6, 7. If the color temperature of the incident light and 8 are significantly different, the color difference signal R is white-balanced by the R-Y control signal voltage and the B-Y control signal voltage calculated in processing step S24.
-Y and BY are not available.

Therefore, following the processing in processing step S25, the microcomputer 22 calculates the average level (R-Y) of the color difference signal R-Y from the variable gain amplifier 3 provided via the A/D converter 2o.
'variable (RY)', .

1 (processing step 526). Next, the microcomputer 22 outputs the average level (R-Y
)'3200 is read from the EEPROM 23, and this is the current average level (R-Y) of the color difference signal R-Y.'N
It is determined whether or not it substantially matches Ow (processing step 527).

If the determination result in processing step S27 is "NO", that is, if the color difference signal RY currently output from the variable gain amplifier 3 and the color difference signal RY to be output are significantly different, then this are photodetectors 6, 7 . This means that light different from the actual illumination light of the subject is incident on 8 and 8.

In this case, the microcomputer 22 increments the digital RY control signal voltage currently output by the mill by a predetermined amount, and repeats the processing from step S26.

That is, in processing steps S26 to S28, the R-Y control signal calculated in processing step S24 is applied so that the R-Y control signal that follows the color temperature of the actual illumination light of the subject is applied to the variable gain amplifier 3. Corrections are applied to the signal voltage.

As a result, the determination result in processing step S27 is 'Y
When ES' is reached, the microcomputer 22 executes processing step S26.
~ Correction processing similar to the correction processing performed on the R-Y control signal voltage in S28 is performed in processing step 5.
Steps 29 to S31 are performed for the BY control signal. That is, the average level (B-Y)' of the color difference signal B-Y currently output from the variable gain amplifier 4 is substituted into the variable (B-Y)' N Ow (step 529), and then E Color difference signal B read from E P ROM2 B in a white balanced state
-Y's average level (B-Y)' 320° and the number of capsules (B-Y)' NOV are incremented until the value of NOV that it is outputting is incremented.

As described above, when the R-Y control signal voltage and the B-Y control signal voltage are adjusted to follow the color temperature of the actual illumination light (when the determination result in processing step S30 becomes "YES") ) The processing by the microcomputer 22 ends.

As described above, in this embodiment, the color temperature is set to 32 at the device manufacturing stage.
All subsequent adjustments for white balance are performed automatically by only manual adjustment of the output voltages of variable gain amplifiers 3 and 4 under the reference illumination light of 00 K. In other words, proper R- at a color temperature of 5000K.
The Y control signal and the B-Y control signal are
It is automatically derived based on each average level of white-balanced color difference signals R-Y and B-B obtained at a color temperature of 3200K, and the appropriate R-Y control signal and B-Y at each color temperature are stored in the EEPROM 23. Data showing the correlation between the color temperature of the illumination light and the appropriate gains of the variable gain amplifiers 3 and 4 for deriving the control signal is automatically stored. This reduces the labor costs that were previously required for adjustments during manufacturing.
This makes it possible to reduce product costs, and eliminates variations in white balance function between devices that occur due to manual adjustments.

Furthermore, unlike before, the white balance adjustment control section 2
5a and the white balance adjustment section 26 constitute a closed loop, and the color difference signals R-Y and B-Y actually output from the variable gain amplifiers 3 and 4 are fed back to the white balance adjustment control section 25a, and the EEPRO
M23i is compared with a pre-stored appropriate color difference signal (a color difference signal with a good white balance obtained under the reference illumination light). Therefore, even when the color temperature detected by the color temperature detection section 24 does not indicate that of the actual illumination light of the subject, it is possible to perform an appropriate white balance adjustment.

Note that the means for storing data necessary for white balance adjustment is not limited to EEF ROM, but may be any storage means that can store data obtained during adjustment and read data necessary during normal operation. It may be.

[Effects of the Invention] As described above, according to the present invention, even when the color temperature of the illumination light of the subject differs from that of the color temperature detection means, a good color difference signal with sufficient white balance can be obtained. At the same time, various adjustments during manufacturing required for white nogrance adjustment are automated. As a result, the labor costs conventionally required for adjustments during manufacturing can be reduced, making it possible to improve the quality of reproduced images while reducing the cost of the device.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a color video camera showing an embodiment of the present invention; FIGS. 2, 3, and 4 are process flow diagrams showing the processing performed by the microcomputer shown in FIG. 1;
Figure 5 is a diagram showing the relationship between the color temperature of the illumination light of the subject and the appropriate R-Y control signal voltage and B-Y control signal voltage, and Figure 6 is a schematic diagram of a conventional color video camera. be. In the figure, 1 is an image sensor, 2 is a processing circuit, 5 is an encoder, 18 and 1 are low/low filters, and 20 is an A
/D converter, 21 is a D/A converter, 22 is a microcomputer, 2
3 is an EEPROM, 24 is a color temperature detection section, 25a and 25b are white lance adjustment control sections, and 26 is a white lance adjustment section. In each figure, the same reference numerals indicate the same or equivalent parts. Figure 82 sr ~ 5tO-Kari'' Sujulγ Figure 3 5ll-S22: Sending step

Claims (1)

[Scope of Claims] Imaging means for imaging a subject and deriving a color difference signal; gain controllable amplification means for amplifying the color difference signal derived by the imaging means; and amplification means for amplifying the color difference signal derived by the imaging means; average level detection means for detecting the average level of the color difference signals, color temperature detection means for detecting the color temperature of external light, a predetermined reference value for appropriate white balance, and illumination light of the subject. storage means for storing data indicating a correlation between the color temperature of the color temperature and the gain of the amplification means necessary to bring the average level of the color difference signal amplified by the amplification means to the reference value; gain control means for controlling the gain of the amplification means based on the stored reference value and the data, the detection output of the color temperature detection means, and the detection output of the average level detection means; Color imaging device.