JPH0817498B2 - Imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus having an image pickup element for converting an optical image into a plurality of color signals and extracting the color signals.

[Prior Art] In an image pickup device that converts an optical image into an electric signal of three primary colors, the amplification gain of each color signal system of a photoelectrically converted electronic circuit is adjusted according to the color temperature of a light source that illuminates a subject. (So-called white balance adjustment) is required.

Conventionally, the adjustment of the white balance is performed for the stationary light as a normal state. On the other hand, when the flash light emitting device is used, the white balance can only be uniquely determined according to the color temperature of the light emitted by the flash light emitting device.

[Problems to be Solved by the Invention] However, when photographing using a flash light emitting device,
In many cases, the contribution from ambient light (ambient light) cannot be ignored as the ambient condition of the subject.

In that case, as in the conventional case, satisfactory image capturing cannot be performed by adjusting the white balance to match only one of the ambient light and the flash light emission.

In view of these problems, the present invention considers both the contribution of ambient light and the contribution of flash light emission during shooting,
It is an object of the present invention to provide an imaging device that can obtain a correct white balance.

[Means for Solving the Problems] In order to achieve this object, in the present invention, a means for storing color temperature data relating to the flash light emitting means, a first detecting means for measuring the luminous intensity by the flash light emitting, Second detecting means for measuring subject brightness due to ambient light; colorimetric means for measuring color temperature due to ambient light; amplifying means for controlling the balance of color signals obtained from the image sensor; The white balance is adjusted by controlling the amplification gain by the amplification means according to the measurement value measured by the second detection means, the color temperature value measured by the color measurement means, and the color temperature data relating to the flash light emitting means. And means.

[Operation] According to the present invention, it is obtained from the image pickup device according to the measured value regarding the light amount of the flash light emission and the ambient light, the value obtained by measuring the color temperature due to the ambient light, and the color temperature data related to the flash light emitting means. By controlling the balance of the color signals, it is possible to obtain a white balance in which the respective color temperatures of ambient light and flash light are added.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 (a) is a block diagram showing a configuration of a first embodiment of an image pickup apparatus according to the present invention, and FIG. 1 (b) is a flow chart showing the operation thereof. The image pickup device has a built-in focus member. In this figure, 1 is an optical system for forming a subject image,
2a is a shutter, 2b is a driver (driving circuit) for the shutter 2a, 2c is a diaphragm, 2d is a driver for the diaphragm 2c, 3 is an image sensor, 4 and 5 are outputs of the image sensor 4, that is, R (red) and B
A variable gain amplifier inserted in each electric signal circuit of each primary color of (blue), 6 is a signal processing circuit, 7 is a recording circuit, and 8 is a recording circuit.
Is an arithmetic and control circuit, 9 is an automatic focusing member, 10 is a photometric circuit, 11 is a colorimetric circuit for ambient light, 12 is a flash light emitting device,
13 is a release switch.

The image sensor 3 is composed of, for example, a CCD, converts an optical image of a subject into an electric signal, and, for example, red, blue, green (G) 3
Extracted as primary color signal.

With respect to the amplifiers 4 and 5, the gains of the amplifiers 4 and 5 are balanced with respect to the color temperature of the light source that illuminates the subject so that correct color reproduction, that is, white balance is obtained.

Next, the operation of this embodiment will be described. When a power source (not shown) is turned on, the photometric circuit 10 and the colorimetric circuit
11 operates and measures the brightness Bv of the steady illumination light and its color temperature (R: B: G = A _R1 : A _B1 : 1) (ST101, ST102) and inputs the result to the arithmetic control circuit 8. To do.

After that, when the release switch 13 is operated (ST103), the automatic focus adjusting member 9 is operated to adjust the optical system 1 for focusing and measure the distance D to the subject (ST104). The value is input to the arithmetic control circuit 8.

Assuming that the light quantity (GNo) of the flash light emitting device 12 is known, the diaphragm (FNo) at which proper exposure can be obtained is given by the following equation.

FNo = (GNo) / D (1) Then, the aperture 2c is driven by the driver 2d to the aperture given by the equation (1) (ST105), and then the shutter 2a is driven by the driver 2b to open (ST106). ), The flash light emitting device 12 is caused to emit light (ST107), then the shutter 2a is closed (ST108), the aperture 2c is opened (ST109), and the object is captured from the image sensor 3 in the next one field period (or frame period). Information (electrical signal) relating to the image is read, converted into a signal form recordable on the recording medium by the signal processing circuit 6, and recorded on the recording medium via the recording circuit 7 (ST110).

Here, the white balance adjustment method will be briefly described.

The irradiation light intensity of the subject by the flash light emitting device 12 is (GNo /
D) ² and the ratio to the irradiation intensity Bv of ambient light is Bv: (GNo / D) ² = k: l ...... (2) k + 1 = 1 ...... (3), which is stored in, for example, a storage device. If the white balance for the flash emission is R: B: G = A _R2 : A _B2 : 1 (4), the amplification degrees A _R and A _B of the amplifiers 4 and 5 are A _R = kA _R1 + lA _R2 …… (5) A _B ＝ kA _B1 ＋ 1A _B2 …… (6) It is possible to obtain a white balance considering the contributions of ambient light and flash light.

In place of the equations (5) and (6), A _R = k'A _R1 + l'A _R2 (7) A _B = k "A _B1 + l" A _B2 ... (8) In order to obtain a white balance, the correspondence from k and l to k ′, k ″ and l ′, l ″ is written in the form of a table or a function in a storage area in the arithmetic control circuit 8 by an experiment. If it is used in the calculation for adjusting the white balance, even better color reproducibility can be obtained.

Next, a second embodiment of the image pickup apparatus according to the present invention will be described with reference to the flowchart of FIG. The hardware used in this embodiment is the same as that in the first embodiment, and will be omitted.

When a power source (not shown) is turned on, the photometry circuit 10 and the color measurement circuit 11 are activated in the same manner as in the first embodiment, and photometry and color measurement are performed (ST201, ST202).

In addition, the automatic focus adjusting member 9 operates to adjust the optical system 1 for focusing, measure the distance D to the subject, and input the value to the arithmetic and control circuit 8. The aperture FNo is obtained by the example (1) formula (ST203).

Next, the arithmetic control circuit 8 determines whether or not the subject is an area where flash light emission photography is possible (ST204). That is, the aperture FNo obtained by the formula (1) is the open FNo of the taking lens.
If the value is larger than that, it is determined that the flash emission photography is possible (within the interlocking range) (Y), and conversely, if the value is smaller, it is determined that the flash emission photography is not possible (outside the interlocking range) (N).

When it is determined that it is within the interlocking range, the same white balance adjustment as described in the first embodiment is performed (ST205).
If it is determined that the value is out of the interlocking range, the flash emission is ignored and only the white balance of the constant light is adjusted (ST206).

When the white balance adjustment method is determined in this way, the release switch 13 is then operated (ST20
7), narrow down the aperture (ST208) and drive the shutter 2a
Driven by 2b to open (ST209), flash light emitting device 12
Light is emitted (ST210), and then the shutter 2a is closed (ST21
1) The aperture is opened (ST212), the information on the subject image is read from the image sensor 3 in the next one field period (or frame period), and recorded on the recording medium via the recording circuit 7 (ST213).

Next, referring to the flowchart of FIG. 3 (a),
A third embodiment of the image pickup apparatus according to the present invention will be described. Since this embodiment is only partially different from the second embodiment, the description of the overlapping portions will be omitted.

In flash photography, if it is determined that the white balance is outside the interlocking range and the white balance is adjusted according to the constant light (ST206), the exposure control is performed according to the exposure calculation in the constant light. For that purpose, exposure calculation is performed based on the photometry result in ST201 (ST301).

After that, wait for the release switch 13 to be operated (ST302), and then press the aperture 2c to ST30 when the release operation is performed.
The aperture is narrowed down according to the calculation result in 1 (ST303), and the shutter 2a is driven by the driver 2b to expose the image sensor 3 for the time determined in ST301 (ST304).

In this way, when it is determined that the flash light emission is out of the interlocking range, the flash light emitting device does not emit light, energy is saved, and optimum light emission for steady light photography becomes possible.

The exposure calculation in ST301 may be calculated according to the program shown in FIG. 3 (b). Alternatively, the calculation can be performed according to a predetermined mode (shutter priority, aperture priority, etc.). FIG. 3 (b) is a program diagram used for determining the exposure of the stationary light in this embodiment, where the horizontal axis represents the shutter speed and the vertical axis represents the aperture.

Next, another embodiment will be described. FIG. 4 (a) is a block diagram showing the configuration of a fourth embodiment of the image pickup apparatus according to the present invention, FIG. 4 (b) is a flow chart showing the operation thereof, and the flash light emitting apparatus is an image pickup apparatus of light quantity GNo1. It is an imaging device that is built-in and to which an external flash light emitting device can be attached. In this figure, 41 is an external flash light emitting device,
42 is an external flash light emitting device 41 and an arithmetic control circuit 8 of the image pickup device.
It is a line that connects between and. Other parts are first
The description is omitted because it is the same as FIG.

Line from the flash light emitting device 41 to the arithmetic control circuit 8
Is it possible to emit light via 42? The light quantity GNo2 of one's own is inputted, and the arithmetic control circuit 8 outputs a light emission command signal to the flash light emitting device 41.

Next, the operation of this embodiment will be described. When a power source (not shown) is turned on, the flash light emitting device 41 outputs to the arithmetic and control circuit 8 information regarding whether or not charging is completed, the amount of light (GNo2), and the color temperature (ST401). Next, the arithmetic control circuit 8 determines whether or not the flash light emitting device 41 has been charged (ST402).

If charging is complete, the amount of light (GN
o) is the sum of the light amounts of the built-in flash light emitting device 12 and the external flash light emitting device 41 GNo = ((GNo1) ² + (GNo2) ² ) ^1/2 (9) (ST403).

If charging is not completed, the amount of light (GNo) that illuminates the subject is only the amount of light from the built-in flash light emitting device 12, so GNo = GNo1 (10) (ST404).

Regarding the white balance adjustment, in the first to third embodiments, the illumination elements are two components, that is, the stationary light and the one type of flash light emission. The flash light emitting device of is added and it becomes three. If the light quantity ratio for illuminating the subject is (ambient light): (built-in flash light emitting device): (external flash light emitting device) = k: l: m (11) k + l + m = 1 (12) , The white balance of the flash light emitting device 41 is R: B: G = A _R3 : A _B3 : 1 (13), and the amplification degrees A _R and A _B of the amplifiers 4 and 5 are A _R = k′A _R1 + L'A _R2 + m'A _R3 (14) A _B = k "A _B1 + l" A _B2 + m "A _B3 ... (15) The relationship should be (k, l, m). From (k ′,
The correspondence to l ′, m ′) and (k ″, l ″, m ″) may be determined in exactly the same way as in the first embodiment.

In this embodiment, an example in which the number of the external flash light emitting device is one has been described, but it goes without saying that the same method can be used in the case of a plurality of devices.

[Effects of the Invention] As is clear from the above description, according to the present invention, the imaging device is controlled by controlling the balance of color signals obtained from the imaging device in consideration of contributions of both flash light emission and ambient light. The correct white balance can be adjusted.

[Brief description of drawings]

FIG. 1 (a) is a block diagram showing a configuration of a first embodiment of an image pickup apparatus according to the present invention, FIG. 1 (b) is a flowchart showing its operation, and FIG. 2 is a second embodiment. FIG. 3 (a) is a flowchart for explaining the third embodiment, FIG. 3 (b) is a program diagram used for determining the exposure of stationary light in the same embodiment, and FIG. FIG. 4A is a block diagram showing the construction of the fourth embodiment, and FIG. 4B is a flow chart showing its operation. In the figure. 1: Optical system, 2a: Shutter 2c: Aperture, 3: Image sensor 4,5: Variable gain amplifier 6: Signal processing circuit 8: Arithmetic control circuit 10: Photometry circuit, 11: Color measurement circuit

Claims (3)

[Claims] 1. An image pickup device for forming an optical image on the surface of an image pickup device, converting the image into a plurality of color signals and taking out the same, and a means for storing color temperature data of a flashlight emitting means and a luminous intensity by the flashlight emission. For controlling the balance of the color signals obtained from the image pickup device, the first detecting means for measuring the luminance of the subject by the ambient light, the second detecting means for measuring the subject brightness by the ambient light, the color measuring means for measuring the color temperature by the ambient light. Controlling the amplification gain by the amplification means according to the measurement values measured by the first and second detection means, the color temperature value measured by the color measurement means, and the color temperature data relating to the flash light emission means. And a means for adjusting the white balance. 2. A method of measuring a distance to a subject, and when the measured value is larger than a distance at which the subject can be flash-photographed, the flash emission is ignored and the white balance with respect to the stationary light is adjusted. The imaging device according to claim (1). 3. When the flash light emitting means built in the image pickup device and the flash light emitting means external to the image pickup device are used, the distance to the object is measured, and the measured value is the flash light built in the image pickup device. The image pickup apparatus according to claim (1), wherein the white balance can be adjusted without ignoring the flash emission even when the distance is larger than the flash-capable distance of the subject by the light emitting means.