JP3278745B2 - Color imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color imaging apparatus that appropriately adjusts white balance.

[Conventional technology]

FIG. 6 is a control block diagram of a white balance of a conventional color image pickup apparatus, and FIG. 7 is a control block diagram of a colorimetric circuit.

In FIG. 6, reference numeral 4 denotes a subject image in red (hereinafter, referred to as R), green (hereinafter, referred to as G), and blue (hereinafter, referred to as B).
Decomposed into three primary colors of the image pickup element for converting into an electric signal, 5 R amplifier for amplifying the R component of the subject obtained from the imaging device 4 (hereinafter referred to as A _R.), B amplifier which also amplifies the B component 6 (hereinafter referred to as A _B.), 7 is sent from the amplifier A _R 5 and A _B amplified R signal is 6 and B signals and the imaging element 4 G
A signal processing unit that derives a predetermined signal based on the signal. 8 is a photometric circuit for measuring the amount of light passing through a not-shown aperture, 9 is a colorimetric sensor that separates the light source color into three primary colors and converts them into electric signals, 10 is a flash light emitting device, and 11 is a colorimetric sensor 9 is a control unit for controlling the signal obtained in 9.

 The operation of the above configuration will be described.

In FIG. 6, the R, G, B
The converted signals KR, KG, and KB of the components are obtained, and the control unit 11 obtains the ratio between the color signals R and G of the light source light and the ratio between B and G from the converted signals KR, KG, and KB.

On the other hand, the subject is also converted by the image pickup device 4 into signals of three primary colors of R, G and B.

As is well known, the white balance is to remove the influence of the light source light from the reflected light of the subject so that it can be reproduced white when a white object is photographed. Therefore, KG is added to the R signal of the R, G, B signals. The white balance adjustment is performed by multiplying the KG / KB by the / KR and B signals. That is, the amplifiers A _R 5 and A
_At B6, a signal is sent from the control unit 11 so as to control as described above. The detailed operation of the control unit 11 will be described with reference to FIG.

Outputs KR, KG, and KB of the colorimetric sensor 9 are input to logarithmic compression circuits 3-1, 3-2, and 3-3 included in the control unit 11, and effectively use the dynamic range. It is easy to do. In each output log KR, log KG, log KB of the logarithmic compression circuits 3-1, 3-2, 3-3, log KR
And log KG are input to a differential unit 3-4, and log KB and log KG are input to a differential unit 3-5, respectively.
(KG / KR) and log (KG / KB) are output. Normally, the differential output via the switch 3-8 and the switch 3-9, respectively sent to amplifiers A _R 5, A _B 6, the white balance is adjusted.

On the other hand, at the time of shooting by flash, a charge completion signal is sent from the flash light emitting device 10, and the switches 3-8 and 3-9
Touches the flash constants 3-6 and 3-7, and the amplifier A _R
Flash constants log SR and log SB are sent to 5, _AB 6, respectively. That is, at the time of flash photography, a predetermined color temperature is set in advance and constant control is always performed.

[Problems to be solved by the invention]

However, since the conventional example is configured as described above, in the case of backlight, that is, when the light source light is directly incident on the imaging device, the subject is not illuminated and the subject is in a shadow. Colorimetric sensor 9
Since the light source light is incident on the light source, the control unit 11 operates to adjust the white balance to the color temperature of the light source.
However, since the subject is in a shadow and is different from the color temperature of the light source, the white balance does not match.

For example, when photographing a person with a sunset as a background, the color of the sunset is incident on the colorimetric sensor 9, so that the control unit 11
Although it is determined that the color temperature is quite low, the color temperature is high because the person who is the subject is actually shadowed. Therefore, if the white balance is adjusted in accordance with the color temperature of the light source, there is a disadvantage that the subject becomes a considerably blue color.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the conventional example, and has as its object to provide a color image pickup apparatus capable of appropriately adjusting white balance even in the case of backlight.

[Means for solving the problem]

A color imaging device according to the present invention is configured as follows.

(1) control means for controlling a white balance of a color signal output from an image pickup means; and evaluation means for evaluating whether or not the subject is in a backlight state, wherein the control means controls the subject by the evaluation means. Is evaluated to be in a backlight state, the control range of the white balance is limited.

(2) control means for controlling the white balance of the color signal output from the imaging means, and evaluation means for evaluating whether or not the subject is in a backlight state, wherein the control means When the subject is evaluated as being in a backlight state, the white balance is controlled based on a color signal in a narrower screen range than when the subject is not evaluated as being in a backlight state, among the color signals output from the imaging unit. I did it.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

(Configuration) FIG. 1 is a control block diagram of a color image pickup apparatus showing an embodiment of the present invention, and FIG. 2 is a flowchart of the above-mentioned conventional example. The same or corresponding parts as in the conventional example are denoted by the same reference numerals.

In FIG. 1, reference numeral 1 denotes an optical system for focusing a subject image, 2a
Is an aperture that limits the luminous flux of the subject, 2b is a driver that drives the aperture, 3a is a shutter that limits the incident time of the subject light, 3b is a driver that drives the shutter, and 4 is an image sensor that is an imaging unit. Yes, and constitutes the second color measurement means.

8A is a photometric circuit which is a photometric means for measuring the amount of light passing through the aperture, 9 is a colorimetric circuit which is a first colorimetric means, 12
Is an arithmetic control circuit that controls the drivers 2a and 3a and the amplifiers A _R 5 and A _B 6 from information on the photometric circuit 8A, the colorimetric circuit 9, and the flash light emitting device 10, and the arithmetic control circuit 12 controls the white balance. It has voltage correcting means 12a.

Further, the photometry circuit 8A has a photometry area divided into a plurality of sections, and further includes an evaluation unit 8a for evaluating what kind of subject is being imaged based on the output of these photometry areas. , 12b are selecting means for selecting one of the colorimetric circuit 9 and the image sensor 4 based on the evaluation result of the evaluating means 8a.

The selecting means 12b is used in a second embodiment described later.

(Operation) An operation will be described based on the above configuration. In FIG. 2, when the power is turned on (step 101), the photometric circuit 8A
Is activated, and the exposure EV is obtained (step 102). If the EV value is equal to or less than the lower limit EV value N of the metering interlocking range (step
103), and outputs a predetermined value preset for strobe photographing as a white balance (WB) control signal (step 111), and then performs a strobe photographing sequence (step 112).

In step 103, if EV ≧ N, colorimetry is performed by the colorimetric circuit 9 (step 104), and a white balance control voltage is calculated (step 105). If the color temperature in a range of color temperature CT of the colorimetric result is previously set to a low color temperature CT _L side and the high color temperature VT _H side (step 106), white balance control voltages calculated in step 105 Is output (step 109), and a sequence of general photographing is performed (step 110). Also, in step 106, if the color temperature CT is CT ≦ CT _L , that is, the color temperature is lower than the low color temperature specified value, or CT ≧ CT _H , that is, if the color temperature CT is higher than the high color temperature specified value. In step 102, the evaluation means based on the photometric result by the photometric circuit 8A
Evaluate whether 8a is backlit (step 10
7) If it is not backlight, the operation after step 109 is performed, and if it is backlight, the correction means 12a corrects the control voltage of the white balance (step 108).

Thereafter, the corrected control voltage is output (step 109),
A sequence of general photographing is performed (step 110).

An example of a method of correcting the control voltage of the white balance will be described with reference to the relationship diagram between the color temperature and the white balance control voltage shown in FIG. That is, the relationship between the color temperature and the white balance control voltage in a normal case is shown by a straight line in FIG. If it is determined in step 107 that the subject is backlit,
As indicated by the straight line of FIG. 3, below the specified value CT _L, or in the case of CT _H or more color temperatures respectively set in the control voltage of the white balance in the CT _L, CT _H, no more white balance adjustment Is corrected in step 108 so as not to perform.

By correcting the control voltage of the white balance at the time of backlight, the color temperature of the colorimetric sensor 9 and the color temperature of the subject at the time of backlight, which have conventionally been a problem, are greatly different. The disadvantage of not being performed can be solved.

 Next, a second embodiment of the present invention will be described.

FIG. 4 is a control block diagram of the color image pickup apparatus of the second embodiment, and FIG. 5 is a flowchart of the operation of this embodiment.

In FIG. 4, 14 is an integration circuit, and 15 is an A / D converter. 20 is a microcomputer, which is a color judging means
16 and an output value calculation means 17 and an output control means 18 are built in.

 The operation will be described based on the above configuration.

4 and 5, the output of the image sensor 4 is input as a color signal for white balance adjustment to an integration circuit 14 that performs an integration operation for each vertical period. The output of the integration circuit 14 is converted into a digital signal by the A / D converter 15 and input to the microcomputer 20. The microcomputer 20 determines the color judgment means 16 from the input signal.
The output value calculating means 17 calculates the value of the white balance control signal based on the result. Further, as a method of obtaining a color signal for white balance adjustment, a peak method may be adopted in which the peak position of a luminance signal is regarded as a light source instead of the integrated value of the color signal, and the color signal at that position is used as information. Alternatively, the integration method and the peak method may be used together. This is output to the D / A converter 19 by the output control means 18, converted into a DC voltage by the D / A converter 19, and input to the A _R 5 and A _B 6 amplifiers, and the color signals R, The output of B is controlled. In this embodiment, a mechanism of white balance control by the TTL method as described above is added to the first embodiment, and the operation will be described in detail with reference to FIG. That is, in FIG. 5, as a result of the photometry in step 102, when it is determined that general photographing without using a flash is performed, it is determined whether or not the subject is backlit (step 107). Colorimetry (Step 14)
And calculate the white balance control voltage (step 10
5) The same flow as in the first embodiment is performed. If it is determined that the subject is backlit, the selection means 12b selects the second color measurement means 4 and performs the white balance adjustment by the TTL method described above (step 113). The white balance adjustment in the TTL method is as described above, and the operation after step 109 is the same as that of the first embodiment.

As described above, in the case of backlight, switching to the TTL method can solve the problem of the conventional white balance deviation caused by the difference between the color temperature of the colorimetric sensor 9 and the color temperature of the subject. .

Also, in the TTL method performed in backlight according to the second embodiment, there is often a difference between the color temperature of the subject and the color temperature of the background during backlight, so that the color signal used for white balance adjustment is In order to eliminate the influence, the upper part of the screen is cut and, for example, control is performed so that only the lower part of the whole screen is used, so that the difference in color temperature between the subject and the background can be reduced. Alternatively, although the color signals for the entire screen are used, the same effect can be obtained by controlling to weight the color signals in the vertical direction of the entire screen.

As described above, according to the above-described embodiment, it is determined whether the light is backlit by the evaluation unit that compares and evaluates a plurality of outputs of the photometry unit that detects the amount of light in which the photometry region is divided into a plurality, If it is backlight and the color temperature is lower or higher than the specified color temperature range, correct color imaging can be obtained by correcting the white balance control voltage obtained by the colorimetric circuit. Can be.

Further, at the time of backlight, the second color measurement means is selected by the selection means, and switching from the external measurement method to the TTL white balance adjustment is performed. The deviation of the white balance due to the difference between the temperature and the color temperature of the subject can be solved.
Further, when the second light source color detecting means is selected, TT
Adjust the color temperature difference between the subject and the background during backlighting by cutting off the color signal at the top of the entire screen of the imaging means in the L system or by weighting the color signal of the entire screen vertically and outputting it. Thus, the white balance can be properly adjusted.

[Effects of the Invention] As is clear from the above description, according to the present invention, by correcting the control signal for white balance control when the subject is in a backlight state, white balance control applicable even in a backlight state is achieved. Can be realized.

Further, the external measurement method and the TTL method are appropriately switched depending on whether the subject is in a backlight state, and thereby, it is possible to prevent the occurrence of a shift in white balance at the time of backlight.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a color image pickup apparatus showing one embodiment of the present invention, FIG. 2 is a flowchart of the above embodiment, FIG. 3 is a graph showing the relationship between color temperature and white balance control voltage, FIG. The figure shows a color imaging device of another embodiment.
FIG. 5 is a control block diagram of a TTL system, FIG. 5 is a flowchart of another embodiment, FIG. 6 is a control block diagram of a conventional color image pickup device, and FIG. 7 is a control block diagram of a conventional colorimetric circuit. 8A is a photometry circuit, 8a is evaluation means, 9 is a colorimetry circuit, 12 is an arithmetic control circuit, 12a is white balance control voltage correction means, 1
2b is a selection means. In the drawings, the same or corresponding parts are represented by the same reference numerals.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/04-9/11 H04N 9/64-9/78

Claims (2)

(57) [Claims] A control unit configured to control a white balance of a color signal output from an imaging unit; and an evaluation unit configured to evaluate whether a subject is in a backlight state. When the subject is evaluated as being in a backlight state, the control range of the white balance is limited. 2. An image processing apparatus comprising: a control unit for controlling a white balance of a color signal output from an imaging unit; and an evaluation unit for evaluating whether or not a subject is in a backlight state, wherein the control unit includes the evaluation unit. When the subject is evaluated as being in the backlight state, the white balance is determined based on the color signals in a narrower screen range than the color signal output from the imaging unit when the subject is not evaluated as being in the backlight state. A color imaging device characterized by controlling: