JPH0640669B2 - Imaging device - Google Patents

Description

The present invention relates to an image pickup apparatus of a system in which diaphragm control is performed by using a signal of a specific portion in a signal obtained from the image pickup apparatus.

[Prior Art] Conventionally, an image pickup apparatus has been proposed in which an aperture of incident light is controlled using a specific portion in an image pickup signal, such as a central portion of a screen or a portion excluding an upper portion of the screen. .
This has a feature that an appropriate aperture amount can be obtained for a subject when the background light is excessively bright (backlight) or excessively dark (highlight) as compared with the subject. However, in this method, especially in a color video camera, signal detection is performed from the luminance signal, and since the red and blue components in the luminance signal are small, when the color of the subject in the above-mentioned specific portion is dark (especially blue). Or when the color is red) the aperture is not appropriate,
It opens too much.

[Problems to be Solved by the Invention] As described above, in the conventional image pickup apparatus, since the signal is detected from the luminance signal, there are few blue and red components in the luminance signal. When the aperture control of the incident light is performed using the specific portion, there is a problem that the aperture amount is not appropriately controlled depending on the color of the subject.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an imaging device that can obtain an appropriate aperture amount.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the image pickup apparatus of the present invention has an aperture control means for extracting a signal obtained from the image pickup apparatus to control an aperture, and the extracted signal. Of these, a correction signal generating means for generating a correction signal according to the color signal information is provided, and the control value of the aperture control means is corrected by the correction signal from the correction signal generating means.

[Operation] With the above configuration, it is possible to appropriately control the aperture even with respect to the difference in color of the subject.

[Embodiment] FIG. 1 is a block diagram showing a main part of an image pickup apparatus according to an embodiment of the present invention. Reference numeral 1 is a lens, 2 is a diaphragm for varying the amount of incident light, and 3 is a CCD or a MOS type semiconductor. An image pickup device, 4 is an amplifier, 5 is an input signal, and a luminance signal and R.
G. A Y-C separation unit for separating a color signal consisting of B, 6 is a process encoder for synthesizing a standard television signal from a luminance signal and a color signal, 7 is an output terminal, and 8 is an aperture correction signal V _c generated from the color signal. correction signal generator, the contact input signal 9 - sectional gate, 10 denotes a diaphragm driving unit for controlling throttle by comparing the signal Vs and the correction signal V _c from the gate 9, 11 is a gate which represents the level of the photometric portion It is a gate signal generator that generates a signal g.

In the image pickup apparatus shown in FIG. 1, an image of a subject (not shown) passes through the lens 1, and the light amount is controlled by the diaphragm 2.
An image is formed on the upper side, photoelectrically converted into an image pickup signal, which is output and amplified by the amplifier 4. The output s of the amplifier 4 is partially output by the YC separation unit 5 to the Y signal and the color difference signal (R-
Y), (B-Y), and the process encoder 6
Are combined into a standard television signal by and output from the output terminal 7 to an external device. On the other hand, the other output s of the amplifier 4 is also input to the gate 9, passes only the gate signal g portion, and is input to the aperture drive unit 10 as the signal V _s .
Color difference signals (R-Y), (B -Y) is also input to the correction signal generator 8, the correction signal V _c is generated, is input to the drive unit 10 stop together with the gate signal g. The diaphragm driver 10 compares the average value of the signal V _s with the correction signal V _c to control the diaphragm 2. The diaphragm 2, the image pickup element 3, an amplifier 4, the gate 9 forms a feedback loop by the diaphragm driving unit 10, the average value and the correction signal V _s of the signal V _s is applied so that the same level.

FIG. 2 is a block diagram showing the details of the main part of the correction signal generator 8 in FIG. 1, 20 and 22 are positive clipping circuits, 21 and 23 are negative clipping circuits, 24 and 25 are inverting amplifiers, 26, 27, 28 and 29 are K ₁ , K ₂ and
A multiplier for multiplying the constants of K ₃ and K ₄ , 30 is an adder, 31
Is a reference voltage, and 32 is a gate. Now, Y-C in FIG.
Only the negative portion of the color difference signal (RY) signal input from the separating unit 5 is taken out by the positive clipping circuit 20, and the multiplier 2
It is input to the adder 30 after being multiplied by a constant K ₁ by 6. Also,
Only the positive portion is taken out by the negative clip circuit 21 and inverted by the inverting amplifier 24, and then the constant K ₂ is given by the multiplier 27.
And is input to the adder 30. In addition, the color difference signal (B
Similarly for the −Y) signal, the negative part extracted by the positive clip circuit 22 is multiplied by a constant K ₃ by a multiplier 28, and the positive part extracted by the negative clip circuit 23 is inverted by an inverting amplifier 25 and then multiplied. The multiplier 29 multiplies the constant K ₄ and the adder 30
Entered in. The adder 30 includes the multipliers 26, 27,
The respective input signals from 28 and 29 and the reference voltage 31 are added and output, and the gate 32 outputs only the portion represented by the gate signal g as the correction signal V _c . The constants K _{1 to} K ₄ are determined as follows. The level of the output s of the amplifier 4 at the time of capturing a white object is 1, and the levels of the output s at the time of capturing R (red), G (green), and B (blue) subjects are S _R ,
If S _G and S _B , then S _R = 0.3 S _G = 0.6 S _B = 0.1. This value is slightly different by method of the color filters of the imaging device _3, S _R, S _G, each _{S B} is less than 1. Therefore, the value of the correction signal V _c at this time is also S _R , S _G ,
If it is the same as S _B , the aperture will be appropriate. When the constants K ₁ , K ₂ , K ₃ and K ₄ are calculated in this way, K ₁ = 0.33 K ₂ = 1 K ₃ = 0.33 K ₄ = 1.

FIG. 3 is a diagram showing the value of the correction signal V _c when the values of the color difference signals (RY) and (BY) in FIG. 2 are varied. When the color difference signals RY = 0 and BY = 0, the correction signal V _c = 0.
Then, as the color becomes darker, the value of the correction signal V _c becomes smaller.

FIG. 4 is a block diagram showing the details of the main parts of another embodiment of the correction signal generator 8 in FIG. 41,4
Reference numeral 2 is an analog-digital (A / D converter), 43 is a read-only memory (ROM) for table conversion, 44 is a latch circuit, and 45 is a digital-analog (D / A) converter. (RY), (BY)
Are converted into digital signals by A / D converters 41 and 42, respectively, and are input as address signals to the ROM 43 for table conversion. For example, the values shown in FIG. 3 are written in the ROM 43 as table data, and the color difference signal (R
Data output corresponding to the values of (-Y) and (BY) is obtained. This data output is converted into an analog correction signal V _c by the D / A converter 45 through the latch circuit 44 and output. In the latch circuit 44, the clock signal is controlled by the gate signal g, and the data output of only the portion of the gate signal g is taken out. Then, the correction signal V taken out
_c is input to and processed by the diaphragm drive unit 10 in FIG.

Although the input of the correction signal generator 8 is the color difference signals (RY) and (BY) in the above embodiment, it may be a primary color signal or a correction signal. Further, the gate circuit 9 may be a circuit that changes the output value according to the level of the gate signal, instead of a circuit that simply connects and disconnects.

Further, although the diaphragm driving unit 10 is applied to the feedback type diaphragm driving method, the diaphragm driving unit 10 can also be applied to a method in which a diaphragm control photosensor is provided separately from the image sensor.

Further, the diaphragm is not limited to a mechanical diaphragm, and can be applied to an electronic shutter operation or a case where the transmittance is changed electrophysically.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to realize an imaging device that prevents an error in the aperture amount due to the color of a subject.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an image pickup apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing details of a main part of a correction signal generator shown in FIG. 1, and FIG. FIG. 4 is a diagram showing the value of the correction signal V _c when the values of the color difference signals (RY) and (BY) are varied, and FIG. 4 is another embodiment of the correction signal generator in FIG. It is a block diagram which shows the detail of the main part shown. In the figure. 1: Lens, 2: Aperture 3: Image sensor, 4: Amplifier 5: YC separation unit 6: Process encoder 8: Correction signal generator, 9: Gate 10: Aperture drive unit 11: Gate signal generator

Claims (1)

[Claims] 1. An exposure means control signal (V _s ) using an image pickup means (3) for picking up a subject image and an output signal of the image pickup means.
Exposure amount control signal forming means (4, 9), and exposure amount control means (2) for variably controlling the exposure amount in the image pickup means in accordance with the exposure amount control signal formed by the exposure amount control signal forming means. A detection means (8) for detecting information (V _c ) relating to the color depth of the subject from the color information signal being output by the image pickup means; and the subject may have a dark color depending on the output of the detection means. An image pickup apparatus comprising: a correction unit (10) that corrects the exposure amount control signal so as to reduce the exposure amount of the image pickup unit controlled by the exposure amount control unit when detected.