JPH09116808A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent control of an iris from being affected by fluctuation of an OB(optical black) level. SOLUTION: An iris control circuit 12 outputs a control signal of an iris 1 in response to a video signal picked up by an image pickup element 2. On the other hand, the video signal flucutation of an OB level is corrected for the video signal by an OB level correction circuit 9. The correction data used for the correction are fed to an OB inverse correction circuit 17 to cancel the OB fluctuation component in the control signal to control the iris 1 via an iris drive circuit 13. Since the control signal of the iris is corrected in response to the OB level correction, the affect of the fluctuation of the OB level on the iris control is avoided.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a camera-integrated VT.
The present invention relates to an image pickup apparatus such as R, and more particularly, to an image pickup apparatus that corrects an optical black level (OB level) of a signal.

[0002]

2. Description of the Related Art Recently, a new proposal has been made as a method for reproducing a direct current component of an optical black level (OB level) of a signal in an image pickup apparatus of this type. FIG. 5 is a block diagram showing the configuration of the image pickup apparatus. In the circuit configuration of FIG. 5, 1 is an aperture (hereinafter referred to as iris) for adjusting the amount of incident light, 2 is an image pickup device such as a CCD for photoelectrically converting an image into a video signal, and 3 is a dual layer for reducing noise of accumulated charges. Correlation sampling circuit (CDS circuit)
And a CD including an AGC circuit for adjusting the gain of the video signal
S / AGC circuit, 4 clamp circuit, 5 video signal 8
An A / D converter for converting a digital signal of 10 bits or the like, and a signal processing circuit 6 for performing a predetermined digital signal processing on the digital video signal.

In the signal processing circuit 6, 7 is an LPF, 8
Is an APC circuit for adding a high frequency correction signal, 9 is an OB level correction circuit, 10 is a γ correction circuit, 11 is a video signal processing circuit, 12 is an iris control circuit for controlling an iris, 1
Reference numeral 3 is an iris drive circuit.

FIG. 6 is a detailed diagram of the OB level correction circuit 9.
Reference numeral 14 is an OB integrated value detection circuit, 15 is a correction data operation circuit, and 16 is an addition / subtraction circuit.

Next, a specific operation will be described. In the circuit configuration of FIG. 5, the incident light of which the amount of light is limited by the iris 1 is imaged on the image sensor 2 and is photoelectrically converted at the same time and is taken out as a video signal. The video signal is C
After the clock component is removed in the DS / AGC circuit 3 and a predetermined gain adjustment is performed by the AGC, it is guided to the clamp circuit 4. In the clamp circuit 4, the input video signal is clamped to a predetermined DC voltage according to the input range of the A / D converter 5 in the subsequent stage. The clamped video signal is converted into a digital signal by the A / D converter 5 and then input to the signal processing circuit 6.

The digital signal is limited to a band required for signal processing by the LPF 7, and one of them is iris control circuit 12
Be led to. The other one is input to the OB level correction circuit 9 after the high frequency emphasizing signal is added in the APC circuit 8. The OB level correction circuit 9 corrects the OB level corresponding to the black portion of the video signal.

The above correction operation will be described with reference to FIG. In FIG. 6, one of the input digital video signals is input to the adder / subtractor circuit 16, and the other is input to the OB integrated value detection circuit 14. In the OB integrated value detection circuit 14, the optical black level (O) of the Y signal (luminance signal) corresponding to the optical black portion period of the video signal is
(B level) is integrated at preset intervals, and the integrated value is detected. The detected OB integrated value is compared with the black level determined by the correction data calculation circuit 15, and correction data is calculated so that the OB integrated value matches the determined black level. Next, the OB level of the video signal is kept constant by adding or subtracting the correction data calculated by the correction data calculating circuit 15 to the OB level of the video signal input in the adder / subtractor circuit 16 and outputting the same.

The video signal output from the OB level correction circuit 9 is γ-corrected by the γ-correction circuit 10, and then guided to the video-signal processing circuit 11 in the subsequent stage to be subjected to predetermined signal processing, whereby the video signal Is output as. The other signal input from the LPF to the iris control circuit 12 generates a control signal for determining the aperture of the diaphragm in accordance with the input signal level in the iris control circuit 12, and the iris drive circuit 13 receives the control signal. Send a control signal. The iris drive circuit 13 adjusts the diaphragm of the iris 1 based on the control signal.

[0009]

However, in the above-mentioned conventional image pickup apparatus, since the video signal input to the iris control circuit 12 is a signal before the OB level is corrected, as shown in FIG. Due to causes such as dark current, AGC gain change, clamp DC voltage change, etc.
When the level changes, the variation Δob is regarded as the variation of the average level of the signal component as it is. Therefore, the iris control circuit 12 generates the correction control data of Δob and sends it to the iris drive circuit 13, and as a result, the iris is Δ
change by ob. However, in reality, the brightness of the subject has not changed, and the fluctuation of the iris causes a malfunction, resulting in a problem that the video signal level fluctuates.

The present invention has been made in view of such a problem, and an object thereof is to obtain an image pickup apparatus in which the iris control is not affected by the fluctuation of the OB level.

[0011]

According to a first aspect of the invention, diaphragm means, image pickup means for photoelectrically converting a subject image obtained through the diaphragm means and outputting a video signal, and a video signal obtained from the image pickup means. And a control means for controlling the diaphragm means based on the video signal obtained from the image pickup means and the correction signal obtained from the generation means.

According to a second aspect of the invention, a diaphragm means,
Depending on the image pickup means for photoelectrically converting the subject image obtained through the diaphragm means to output a video signal, the correction means for correcting the black level of the video signal obtained from the image pickup means, and the video signal corrected by the correction means. And a control means for controlling the diaphragm means.

[0013]

According to the present invention, even when the OB level of the video signal fluctuates and the OB level correction operation is performed accordingly, the control signal for performing the iris control is also subjected to the same correction, so that the iris control is performed. Can be made unaffected by fluctuations in the OB level.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to the block diagrams of FIGS. 1 to 7 and 9 to 13 have the same configuration as the blocks with the same numbers in FIG. 5 described in the conventional example, and a description thereof will be omitted. The configuration of the OB level correction circuit 9 according to the present embodiment is as shown in FIG.
One of the outputs of O of FIG. 1 provided by the present embodiment.
It is adapted to be input to the B reverse correction circuit 17.

Next, a specific operation will be described. In the circuit configuration of FIG. 1, after the incident light whose light amount is limited by the iris 1 is imaged on the image sensor 2 and extracted as a video signal, the operation processed by the signal processing circuit 6 is the conventional example of FIG. The same is done as.

Next, the correction operation of the OB level correction circuit 9 will be described with reference to FIG. In FIG. 2, one of the digital video signals input from the APC circuit 8 is input to the addition / subtraction circuit 16, and the other is input to the OB integrated value detection circuit 14.
Is input to The OB integrated value detection circuit 14 integrates the optical black level (OB level) of the Y signal corresponding to the optical black portion period of the video signal at preset intervals and detects the integrated value. The detected OB integrated value is compared with the black level determined by the correction data operation circuit 18, and the correction data is calculated so that the OB integrated value matches the determined black level. The calculated correction data is input to the addition / subtraction circuit 16 and the OB inverse correction circuit 17. In the adder / subtractor circuit 16, the OB level of the video signal is kept constant by adding or subtracting the correction data calculated by the correction data calculating circuit 15 to the OB level of the input video signal and outputting it. The video signal output from the OB level correction circuit 9 is γ-corrected by the γ-correction circuit 10 and then guided to a video signal processing circuit 11 in a subsequent stage to be subjected to predetermined signal processing and then output as a video signal. To be done.

On the other hand, from the LPF 7 to the iris control circuit 12
The other signal input to the iris control circuit 12
A control signal for determining the opening of the throttle is generated in accordance with the input signal level. This control signal causes the OB reverse correction circuit 17 to cancel the variation Δob when the OB level changes by the correction data. It Therefore, the control signal sent to the iris drive circuit 13 is the same as before the OB level was changed. Iris drive circuit 13
Then, the diaphragm of the iris 1 is adjusted based on this control signal.

According to the first embodiment, even if the OB level changes due to a dark current, a change in AGC gain, a change in clamp DC voltage, etc., the signal for controlling the iris is also corrected. Therefore, the iris control can be prevented from being affected by the fluctuation of the OB level.

FIG. 3 is a block diagram showing a second embodiment of the present invention. 3 to 13 are the same as the blocks denoted by the same numbers in FIG. 5 described in the conventional example, and the description thereof will be omitted. An OB level correction circuit 19 has the same configuration as the OB level correction circuit 9.

Next, since the specific operation will be clear from the above description, the operation of the part peculiar to the second embodiment will be described. The video signal input to the signal processing circuit 6 is band-limited by the LPF 7, and one of them is APC circuit 8
The high frequency emphasizing signal is added at, and the same processing as in the first embodiment is performed and output from the video signal processing circuit 11. The other output of the LPF 7 is input to the OB level correction circuit 19. The OB level correction circuit 19 has the same configuration as the OB level correction circuit 9, and its operation is as described in the first embodiment. The video signal corrected by the OB level correction circuit 19 generates a control signal for determining the aperture of the diaphragm in the iris control circuit 12 according to the input signal level, and the iris drive circuit 13 outputs the iris 1
Control.

According to the second embodiment, even if the OB level changes due to a dark current, a change in AGC gain, a change in clamp DC voltage, or the like, the signal for controlling the iris is also corrected. Therefore, the iris control can be prevented from being affected by the fluctuation of the OB level. Further, since the OB level correction circuit 19 having the same structure as the OB level correction circuit 9 is used for the iris correction, more accurate correction can be performed.

FIG. 4 is a block diagram showing a third embodiment of the present invention. 4 to 13 are the same as the blocks with the same numbers in FIG. 5 described in the conventional example, and the description thereof will be omitted. The difference from the conventional example is that the output of the OB level correction circuit 9 is input to the iris control circuit 12.

Next, the operation will be described. Since the signal input to the iris control circuit 12 is the signal that has passed through the OB level correction circuit 9, the same effect as that of the second embodiment shown in FIG. 3 can be obtained. Further, the output of the OB level correction circuit 9 after passing through the APC circuit 8 is only that the high frequency component is AC-added to the video signal, and the original signal component is extracted experimentally by integration. I know.

According to the third embodiment, even if the OB level changes due to a dark current, a change in the AGC gain, a change in the clamp DC voltage, or the like, the signal for controlling the iris is also corrected. Therefore, the iris control can be prevented from being affected by the fluctuation of the OB level. Further, since the correction circuit for the video signal and the correction circuit for the iris control are shared by the OB level correction circuit 9,
A simpler configuration can be achieved.

[0025]

As described above, according to the present invention,
For example, even if the OB level changes due to reasons such as dark current, AGC gain change, and clamp DC voltage change, the iris control signal is also corrected, so the iris control affects the OB level change. It becomes possible not to receive.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an OB level correction circuit.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a third embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional imaging device.

FIG. 6 is a block diagram showing a configuration of an OB level correction circuit.

FIG. 7 is a signal waveform diagram illustrating an input video signal to the iris control circuit when the OB level changes.

[Explanation of symbols]

 1 Iris 2 Image sensor 9, 19 OB level correction circuit 12 Iris control circuit 13 Iris drive circuit 14 OB integrated value detection circuit 16 Addition / subtraction circuit 17 OB reverse correction circuit 18 Correction data operation circuit

Claims (2)

[Claims] 1. A diaphragm means, an imaging means for photoelectrically converting a subject image obtained through the diaphragm means to output a video signal, and a correction signal for compensating a black level of a video signal obtained from the imaging means. An image pickup apparatus comprising: means, and control means for controlling the diaphragm means based on a video signal obtained from the image pickup means and a correction signal obtained from the creating means. 2. A diaphragm means, an imaging means for photoelectrically converting a subject image obtained through the diaphragm means and outputting a video signal, a correction means for correcting the black level of the video signal obtained from the imaging means, and the correction An image pickup apparatus comprising: a control unit that controls the diaphragm unit according to a video signal corrected by the unit.