JPH10174002A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the definition of a video image by providing an OB integrated value detecting means for integrating and detecting an optical black level(OB level), and an OB integration control means for making the OB integrated value be ineffective in a fixed period. SOLUTION: A picture signal detected by a CCD 1 is sample-held by an S/H circuit and an AGC circuit 2 to be amplified into a prescribed level, and its DC component is cut by a coupling capacitor. Then, the resulting signal is clamped at the timing of the clamp pulse generated in a clamp pulse generating circuit 6 by a voltage generated in a DC voltage generating circuit 9 by a clamp circuit 3. The clamp pulse is supplied to the OB integration control circuit 7 on the other hand. In the OB integration control circuit 7, the edges of rising and falling of the clamp pulse are detected respectively, a control signal is generated in the period before and after, and is transmitted to an OB level correcting circuit 8. The OB level correcting circuit 8 receives the output of the OB integration control circuit 7, and stops OB level integration during the control signal is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a camera-integrated VTR for recording an image signal detected by a video camera or the like.

[0002]

[Prior art]

[First Conventional Example] FIGS. 12 and 14 are block diagrams showing the configuration of a conventional imaging apparatus. FIG. 12 and FIG.
In the circuit configuration of 4, an image sensor 1 such as a CCD for converting an image into an image signal by photoelectrically converting an image, and an image sensor 1
Correlation Sampling Circuit (S / H Circuit) for Reducing the Noise of Accumulated Charges and AGC for Adjusting the Gain of the Image Signal
A circuit including a circuit (hereinafter referred to as an AGC circuit); 4, an A / D converter for converting a video signal output from the clamp circuit 3 into a digital signal of 8 bits or 10 bits;
Reference numeral 5 denotes a signal processing circuit for performing digital signal processing on the digital video signal output from the A / D converter 4, and reference numeral 9 denotes a D for clamping the signal input to the clamp circuit 3.
A DC voltage generation circuit for generating a C voltage;
The OB (optical black) level of the video signal digitally converted by the converter 4 is compared with a predetermined black level 19 to calculate an offset amount such that the two coincide with each other, and the calculation result is used as the OB of the video signal. OB level correction circuit for performing addition or subtraction correction on levels, FIG. 14
Is a detailed diagram of the OB level correction circuit 18, and 10 is an optical black (O) of the image sensor 1 in a video signal.
B) An OB integrated value detecting circuit for integrating the optical black level (OB level) of the Y signal corresponding to the portion at one horizontal line or at predetermined intervals, and 11 is detected by the OB integrated value detecting circuit. A correction data calculating circuit for comparing the OB integrated value with a predetermined black level and calculating correction data such that the OB integrated value matches the predetermined black level;
And an addition / subtraction circuit for adding or subtracting the correction data calculated by the correction data calculation circuit 11 to the OB level of the video signal input to. The configuration is as described above.

Next, a specific operation will be described. FIG.
In the circuit configuration of 2, the video signal output from the image sensor 1 is input to the S / H circuit and the AGC circuit 2 and has a predetermined gain. The AG
The video signal output from the C circuit 2 is coupled in an AC manner by a DC cut by passing through a capacitor C, and is input to the clamp circuit 3. The video signal input to the clamp circuit 3 is clamped in the clamp circuit 3 by the fixed voltage generated by the DC voltage generation circuit 9 with the clamp pulse output from the clamp pulse generation circuit 6. The clamped video signal is input to the A / D converter 4 and converted into a digital signal.
The signal is input to the level correction circuit 18.

An example of the clamp circuit will be described with reference to FIG. In FIG. 13, reference numeral 1 denotes a CCD, 2 denotes an S / H circuit and an AGC circuit, and 4 denotes an A / D conversion circuit. A clamp pulse is supplied from a clamp pulse generation circuit 6 to the base of a transistor Q1. During the period, the transistor Q1 is turned on, and the voltage Ve generated by the DC voltage generation circuit 9 is applied to the signal line a. Transistor Q1 is OFF during the period when the clean pulse is low
Then, the voltage at point a is kept at voltage Ve. In this case, a parasitic capacitance Cob exists between the base and the collector of the transistor Q1.
The clamp pulse generated by the clamp pulse generation circuit 6 depends on the pattern of the substrate on which the clamp circuit and the like are mounted, and the like.
Of the stray capacitance Cf between the clamp line and the base line, the waveform becomes a differential waveform during the edge period of the clamp pulse and leaks into the signal line. FIG. 3 shows this waveform.
It is an OB part waveform shown in (b).

The processing in the OB level detection circuit 18 will be described below with reference to the block diagram of FIG.

One of the digital video signals input to the OB level correction circuit 18 is input to the addition / subtraction circuit 12, and the other is the OB integration value detection circuit 10.
Is input to In the OB integral value detection circuit 10, the optical black level (OB) of the Y signal corresponding to the optical black portion of the image sensor 1 in the video signal is output.
Level) is integrated over one horizontal line or at intervals set in advance mechanically as black component detection elements, and an OB integrated value is detected. The OB integration value detected by the OB integration value detection circuit 10 is compared with a predetermined black level 19 by the correction data calculation circuit 11 so that the OB integration value matches the predetermined black level 19. Correction data is calculated. In the addition / subtraction circuit 12,
O of the video signal input to the OB level correction circuit 18
The correction data calculated by the correction data calculation circuit 11 is added to or subtracted from the B level, and output from the OB level correction circuit. As a result, the OB level of the video signal input to the signal processing circuit 5 is kept constant.

[Second Conventional Example] Next, as a second conventional example, a three-plate type imaging apparatus will be described. In the circuit configuration shown in FIG. 16, reference numeral 26 denotes a diaphragm (hereinafter, referred to as an iris) for adjusting the amount of incident light, 1R, 1G, and 1B denote imaging elements such as CCDs for photoelectrically converting an image into RGB signals;
Reference numerals 2R, 2G, and 2B denote circuits including a double correlation sampling circuit (CDS circuit) for reducing noise of accumulated charges and an AGC circuit for adjusting the gain of an image signal. 3R, 3G, and 3B
Is a clamp circuit, 4R, 4G and 4B are video signals of 8 to 1
A / D converter for converting into a digital signal such as 0 bit, 6
Is a signal processing circuit for performing predetermined digital signal processing on the digital video signal, 7R, 7G, and RB are LPFs in a block in the signal processing circuit 6, and 23 is a signal for obtaining a luminance signal from the RGB signal at a predetermined addition ratio. An adder circuit, 8 an APC circuit for adding a high-frequency correction signal, 20 an OB level correction circuit,
21 is a gamma conversion circuit, 22 is a video signal processing circuit at the subsequent stage, 2
Reference numeral 4 denotes an iris control circuit for controlling the iris, and reference numeral 25 denotes an iris drive circuit. FIG. 17 is a detailed diagram of the OB level correction circuit 20, in which 10 is an OB integrated value detection circuit, 11 is a correction data operation circuit, and 12 is an addition / subtraction circuit, which is configured as described above.

Next, a specific operation will be described.
In the circuit configuration of FIG. 16, the incident light whose light amount is limited by the iris 26 is transmitted to the image pickup devices CCD1R, CCD1G, and CC1.
The image is formed on the D1B and photoelectrically converted at the same time, and is extracted as a plurality of video signals (for example, RGB signals). After the clock signals are removed from the RGB signals in the CDS / AGC circuits 2R, 2G, and 2B and the gains are adjusted by AGC, the clamp circuits 3R, 3G,
It is led to 3B. In the clamp circuits 3R, 3G, and 3B, the input video signal is supplied to an A / D converter 4 in a subsequent stage.
It is clamped to a predetermined DC voltage in accordance with the input ranges of R, 4G, and 4B. The clamped RGB signal is A / A
After being converted into digital signals by the D converters 4R, 4G, and 4B, the digital signals are input to the digital signal processing circuit 6. The digital RGB signals are limited to bands required for signal processing by LPFs 7R, 7G, and 7B, added by a predetermined addition ratio in an addition circuit 23, a high-frequency emphasis signal is added in an APC circuit 8, and an OB level correction circuit 20. The OB level correction circuit 20 corrects the OB level corresponding to the black portion of the added video signal, and this correction operation will be described in detail with reference to FIG. In FIG.
One of the input digital video signals is input to the addition / subtraction circuit 12, and the other is input to the OB integration value detection circuit 10. The OB integrated value detection circuit 10 integrates the optical black level (OB level) of the Y signal corresponding to the optical black period of the video signal at predetermined intervals and detects the integrated value. The OB integration value detected by the OB integration value detection circuit 10 is compared with a black level 19 determined by the correction data calculation circuit 11,
Correction data is calculated such that the OB integral value matches the determined black level 19. In the addition / subtraction circuit 12, the correction data calculated by the correction data calculation circuit 11 is added to or subtracted from the OB level of the input video signal, and is output. The OB level of the video signal is kept constant.
One of the video signals output from the OB level correction circuit 20 is guided to the iris control circuit 24. The other is subjected to γ correction by the γ correction circuit 21, and then guided to the video signal processing circuit 22 in the subsequent stage, subjected to predetermined signal processing, and output as a video signal. The other signal input to the iris control circuit 24 is
Generates a control signal for determining the degree of opening of the diaphragm according to the input signal level, and sends the control signal to the iris drive circuit 25. The iris drive circuit 25 adjusts the aperture of the iris 26 based on the control signal.

[0009]

However, in the imaging apparatus shown in the first conventional example, the OB portion clamped by the clamp pulse has a flaw caused by the pulse clamp. In some cases, the flaw affects the detection integration value, and the resulting black level of the resulting signal fluctuates or sinks, thereby deteriorating the image quality.

Further, in the imaging apparatus described in the first conventional example, when the DC voltage of the Y signal fluctuates due to temperature or the like, the operation result of the correction data operation circuit 11 is as shown in the table of FIG. When a correction amount that periodically repeats certain correction amounts K and K + 1 is generated, the OB level of the video signal periodically fluctuates because the change amount of the OB level per the minimum change amount of the correction amount is large. However, there is a problem that a stable video signal cannot be obtained.

Further, in the image pickup apparatus shown in the second conventional example, the video signal input to the iris control circuit 12 is a video signal after RGB addition, for example, as shown in FIG. Between the AGC gain and the DC voltage of the clamp
If the OB levels of the RGB signals vary and change (ob variation), appropriate OB level correction data cannot be obtained because of the variation Δob of each channel, and the iris control circuit 12 does not have appropriate correction control data. Is sent, and as a result, the iris malfunctions and the appropriate amount of light is
There is a drawback that the light does not enter.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the drawbacks of the first conventional example and to eliminate the phenomenon that the black level of the obtained signal rises or falls, thereby improving the quality of a video image.

In addition, the present invention provides an image pickup apparatus which does not have the above-mentioned problems, particularly when the minimum change amount of the correction amount changes periodically and frequently, with respect to the first conventional example. The purpose is to:

Another object of the present invention is to provide an image pickup apparatus which does not cause the above-mentioned problems irrespective of the fluctuation of the OB level of each channel, compared to the second conventional example.

[0015]

[Means for Solving the Problems]

[First Solution] In order to solve the above problem, a signal corresponding to an optical black portion of a CCD is fixed to a fixed DC signal.
Clamping means for clamping to a voltage, fixed DC voltage generating means for generating a fixed DC voltage, and an optical black level (OB level) of the signal are integrated at predetermined intervals and the value is integrated. OB integral value detecting means for detecting, OB integral control means for invalidating the OB integral for a certain period, OB integral value detected by the OB integral value detecting means and a predetermined black level. And a correction data calculating means for calculating a correction amount such that the two coincide with each other, and an addition and subtraction for adding or subtracting the correction data obtained by the correction data calculating means to or from the OB level of the video signal. The above object is attained by providing means.

(Operation) Even if a flaw occurs due to the clamp pulse, the integral value of the flaw part is ignored, so that the influence of the flaw on the OB integral detection value is eliminated, and the accurate black level detection is performed. Solve the problem.

[Second Solution] In order to solve the above problems, a clamp means for clamping a Y signal corresponding to an optical black portion of a CCD to a fixed DC voltage, and generating the fixed DC voltage Fixed D for
C voltage generating means, OB integrated value detecting means for integrating the optical black level (OB level) of the Y signal at predetermined intervals, and detecting the value thereof;
Correction amount calculating means for comparing the OB integrated value detected by the B integrated value detecting means with a predetermined black level and calculating a correction amount such that the two coincide with each other; Correction data determining means for filtering the corrected correction amount to determine correction data, and adding / subtracting means for adding or subtracting the correction data determined by the correction data determining means to or from the OB level of the video signal. The above-mentioned subject is solved by providing.

(Operation) When the DC voltage of the Y signal fluctuates, the optical black level (OB level) of the Y signal is integrated at predetermined intervals, an OB integrated value is detected, and the value is determined in advance. The corrected black level is compared with the calculated black level to calculate a correction amount that matches the two, and the correction amount is filtered to determine correction data.
The object is achieved by adding or subtracting the correction data determined by the correction data determining means from the level.

[Third Problem Solving Means] In order to solve the above problems, an iris, iris driving means for driving the iris, iris control means for controlling opening and closing of the iris, a plurality of image pickup devices, and a plurality of A plurality of clamping means for clamping an output signal of the image sensor, a plurality of A / D converters for converting a video signal clamped by the clamping means into digital data, and a conversion to digital data by the A / D converter A plurality of detection means for integrating the level of a portion corresponding to black of each of the plurality of video signals thus obtained, and comparing the integrated value detected by the detection means with a predetermined level. A plurality of correction data calculating means for calculating a correction amount, and a plurality of corrections obtained by the plurality of correction data calculating means for a plurality of respective video signals. In an image pickup apparatus provided with a plurality of addition / subtraction means for adding or subtracting data, a signal inputted to the iris control means has a certain ratio of a plurality of correction data corresponding to the plurality of video signals, respectively. The above problem is solved by using a correction signal based on the signal obtained by the above.

[Operation] Even if the OB level of each video signal fluctuates and each OB level correction means operates accordingly, the signal guided to the iris control means is a signal obtained by the ratio of each correction level. The above-mentioned problem is solved by making the above control less susceptible to the fluctuation of the OB level.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] An embodiment of the present invention will be described below with reference to the block diagrams of FIGS. CCD1, S /
The H circuit & AGC circuit 2, the clamp circuit 3, the A / D conversion circuit 4, the signal processing circuit 5, and the DC voltage generation circuit 9 have the same configuration as that shown in FIG. The output of the clamp pulse generation circuit 6 is connected to the clamp circuit 3 and the OB integration control circuit 7. The control output of the OB integration control circuit 7 is connected to the OB level correction circuit 8. OB
The detailed configuration of the level correction circuit 8 is as shown in FIG.

Next, a specific operation will be described. The parts that are the same as in the conventional example are omitted, and the parts unique to the present embodiment will be described. The image signal detected from the CCD 1 is S / H
The signal is sampled and held by the circuit & AGC circuit 2, amplified to a predetermined level, and the DC component is cut by the coupling capacitor C. Next, the clamp circuit 3 clamps at the timing of the clamp pulse generated by the clamp pulse generation circuit 6 with the voltage generated by the DC voltage generation circuit 9 as in the conventional example. The other end of the clamp pulse is input to the OB integration control circuit 7. The OB integration control circuit 7 detects the rising edge and the falling edge of the clamp pulse, and performs the operation shown in FIG.
Is generated and sent to the OB level correction circuit 8. The OB level correction circuit 8 receives the output of the OB integration control circuit 7 and stops the OB level integration while the control signal (c) is being generated.

FIG. 2 shows an OB level correction circuit 8 according to this embodiment.
FIG. The OB integral value detection circuit 10, the correction data operation circuit 11, and the addition / subtraction circuit 12 operate in the same manner as in the conventional example, and thus description thereof is omitted. Reference numeral 13 denotes a gate circuit provided between the output of the OB integrated value detection circuit 10 and the correction data operation circuit 11, and performs a gate operation by a signal input to a gate signal input terminal. The gate signal input terminal is connected to the output of the OB integration control circuit 7, and the OB integration detection circuit 10
Is gated.

FIGS. 4A and 4B show an OB integration control circuit 7.
And an example of its flowchart are shown. In FIG. 4, when a clamp pulse (b) is input from the clamp pulse generation circuit 6, it is supplied to the monomultivibrator 31 and the inverter 30, and the output (c) of the inverter 30 is input to the monomultivibrator 32. Each of the mono-multi vibrators 31 and 32 is at a high level during a period of th (d) and (e), added by the OR circuit 23, and output as the control signal (f) of FIG.

According to the present embodiment, the clamp circuit 3 removes the impulse generated when the clamp pulse generation circuit 6 rises or falls, so that even if a flaw caused by the clamp pulse is on the OB portion, before and after the flaw is generated. Since the operation of the OB integration is not performed in the portion, the obtained data is not affected by the flaw, so that the integrated data of the correct black level is obtained, and the accurate black level correction is performed.

[Second Embodiment] A second embodiment of the present invention will be described below with reference to the block diagrams of FIGS. 5 and 6 and the flowchart of FIG.

5, a CCD 1, an S / H circuit & AGC circuit 2, a clamp circuit 3, a clamp pulse generating circuit 6, DC
Voltage generation circuit 9, A / D conversion circuit 4, and signal processing circuit 5
Has the same configuration as that of FIG. 12 described in the conventional example.

The OB integral value detection circuit, the correction data operation circuit 11, and the addition / subtraction circuit 12 in FIG. 6 are the same as those described in FIG.

The reference numeral 13 shown in FIG.
By comparing the OB level of the video signal digitally converted with the predetermined black level and calculating an offset amount such that the two coincide with each other, filtering the calculation result to determine correction data, This is a new OB level correction circuit for performing correction of adding or subtracting the correction data to the OB level. Reference numeral 14 shown in FIG. 2 denotes a correction data determination circuit for filtering the correction amount calculated by the correction data calculation circuit 11 and determining correction data.

Next, a specific operation will be described. FIG.
In the circuit configuration described above, the video signal output by the CCD 1 of the image sensor is input to the S / H circuit & AGC circuit 2, where the detection signal of each pixel element of the video signal is converted into a continuous video signal. To have a predetermined gain. The video signal output from the S / H circuit & AGC circuit 2 is AC-coupled by passing through a capacitor and input to the clamp circuit 3. The clamp circuit 3
Is clamped by the clamp voltage output from the DC voltage generation circuit 9 with the clamp pulse output from the clamp pulse generation circuit 6 in the clamp circuit 3. The clamped video signal is input to the A / D converter 4 and converted into a digital signal, and then input to the new OB level correction circuit 13. Thereafter, the processing in the new OB level detection circuit 13 is described with reference to FIG.
This will be described with reference to the block diagram of FIG.

One of the digital video signals input to the new OB level correction circuit 13 is input to the addition / subtraction circuit 12, and the other is the OB integration value detection circuit 10.
Is input to In the OB integrated value detection circuit 10, the optical black level (OB level) of the Y signal corresponding to the optical black portion of the CCD 1 of the image pickup device in the video signal is set to one horizontal line or an interval previously set as a black level detection device. Integrate every time, OB
Detect the integral value. The OB integrated value detected by the OB integrated value detecting circuit 19 is compared with a predetermined black level by the correction data calculating circuit 11, and a correction is made so that the OB integrated value matches the predetermined black level 19. The quantity is calculated. The correction amount calculated by the correction data calculation circuit 11 is input to the correction data determination circuit 14 and is compared with the correction data determined by the correction data determination circuit 14 to perform filtering and determine correction data. The addition / subtraction circuit 12 adds or subtracts the correction data determined by the correction data determination circuit 14 to or from the OB level of the video signal input to the new OB level correction circuit 13, and outputs the result from the new OB level correction circuit 13.

As a result, the OB level of the video signal input to the signal processing circuit 5 is kept constant.

Next, specific processing of the correction data determination circuit 14 will be described with reference to the flowchart of FIG.

First, it is determined whether the correction amount X calculated by the correction data calculation circuit 11 is equal to the correction data Y of the correction data detection circuit 14 input to the addition / subtraction circuit 12 (S1). If equal, step S6
Move to. If they are not equal, the correction amount X calculated by the correction data calculation circuit 11 and the addition / subtraction circuit 1
It is determined whether there is a difference of 2 or more from the correction data Y of the correction data detection circuit 14 input to 2 (S2). If there is a difference of 2 or more, 1 is added to the correction data Y in step S8 to bring the correction amount X calculated by the correction data calculation circuit 11 close to the correction data Y. If the difference does not reach 2, it is determined whether or not the difference between the correction amount X calculated by the correction data calculation circuit 11 and the correction data Y input to the addition / subtraction circuit 11 is 2 or more (S3). If the difference is 2 or more, 1 is subtracted from the correction data Y in step 7 to bring the correction amount X calculated by the correction data calculation circuit 11 closer to the correction data Y. If the difference does not reach 2, it means that the difference between the correction amount X calculated by the correction data calculation circuit 11 and the correction data Y input to the addition / subtraction circuit 11 is -1 or +1.

Here, it is determined whether or not the counter T counting in a certain cycle in the correction data determination circuit 14 is longer than a predetermined time Z in which the correction amount X is stabilized (S4). If it is shorter (Z> T), the process proceeds to step S9, and the counter T is increased by one. If it is long, the correction data X calculated by the correction data calculation circuit 11 is input to the correction data Y input to the addition / subtraction circuit 12 (S5). Next, the counter T is reset to 0 (S6). FIG. 8 shows a change in the correction data determined by the correction data determination circuit 142 according to the flowchart shown in FIG. While the values of K and K + 1 are repeatedly output at each timing based on the correction amount X of the correction data calculation circuit 11, the correction data Y output from the correction data determination circuit 13 is corrected to the K value at any timing. , A constant level which is not affected by temperature and environmental changes is output, so that the addition / subtraction ratio by the addition / subtraction circuit 12 is also constant, and a high-quality video signal without fluctuation is obtained.

[Third Embodiment] A third embodiment of the present invention will be described below with reference to the block diagram of FIG. In the third embodiment, an iris 26, CCDs 1R, 1G, 1B, CDS / AGC which operate in the same manner as the conventional example of FIG.
Circuits 2R, 2G, 2B, clamp circuits 3R, 3G, 3
Description of the B and A / D conversion circuits 4R, 4G, 4B will be omitted, and the digital signal processing circuit 6 will be described.

RG input to the digital signal processing circuit 6
The B signal is limited to a band required for signal processing by LPFs 7R, 7G, and 7B, and the OB level correction circuits 20R, 20G,
20B. The OB level correction circuit 20R,
In 20G and 20B, the OB level corresponding to the black portion of the video signal is corrected. In FIG. 10, each input digital video signal is input to the addition / subtraction circuit 12, and the other is input to the OB integration value detection circuit 10. Is done. Said O
The B integral value detection circuit 10 integrates the optical black level (OB level) of each signal corresponding to the optical black period of the video signal at predetermined intervals,
The integrated value is detected. The OB integrated value detected by the OB integrated value detection circuit 10 is compared with a black level 19 determined by the correction data calculation circuit 14, and correction data such that the OB integrated value matches the determined black level 19 is obtained. Is calculated. The result of the operation is led to the addition / subtraction circuit 12. The correction data calculated by each of the correction data calculation circuits 11 is added to or subtracted from the OB level of each video signal input to the addition / subtraction circuit 12, and is output. The OB level of each video signal is kept constant. The video signals output from the OB level correction circuits 20R, 20G, and 20B are:
An addition circuit 23 adds the signals at a predetermined addition ratio to obtain a luminance signal. Thereafter, the high frequency correction is performed by the APC circuit 15 and the gamma correction is performed by the gamma correction circuit 21. Then, the signal is guided to the video signal processing circuit 22 in the subsequent stage, subjected to predetermined signal processing, and output as a video signal.

The OB level correction circuits 20R, 20R
The other outputs of G and 20B are added at a predetermined addition ratio by an adder circuit 27, and then input to an iris control circuit 24. In the iris control circuit 24, the aperture of the diaphragm is adjusted according to the input signal level. Generate a control signal to determine.

According to the above-described embodiment, even if the OB level changes due to, for example, a change in the dark current, a change in the AGC gain, or a change in the clamp DC voltage, the change Δob of each signal is equal to the signal addition ratio. And the control data sent to the iris drive circuit is less affected by variations in the OB level of each channel.

[Fourth Embodiment] A fourth embodiment of the present invention will be described below with reference to the block diagram of FIG. FIG.
1 LPF 7R, 7G, 7B and OB level correction circuit 2
Up to 0R, 20G, and 20B, the APC circuit 15, the gamma correction circuit 21, the video signal correction circuit 22, the iris control circuit 24
Up to this point, the blocks are the same as those in FIG.

Next, a specific description will be clear in the description of the above-described embodiments, and therefore, a part unique to the fourth embodiment will be described. The video signals input to the digital signal processing circuit 6 are LPFs 7R, 7G, 7B
OB level correction circuits 20R, 20G,
20B. The OB level correction circuit 20R,
In 20G and 20B, the OB level corresponding to the black portion of the video signal is corrected. In FIG. 10, each input digital video signal is input to the addition / subtraction circuit 12, and the other is input to the OB integration value detection circuit 10. Is done. Said O
The B integral value detection circuit 10 integrates the optical black level (OB level) of each signal corresponding to the optical black period of the video signal at predetermined intervals,
The integrated value is detected. The OB integrated value detected by the OB integrated value detecting circuit 10 is compared with the black level 19 determined by the correction data calculating circuit 11, and correction data such that the OB integrated value matches the determined black level 19 is obtained. Is calculated. The result of the operation is led to the addition / subtraction circuit 12. The correction data calculated by the correction data calculation circuit 11 is added to or subtracted from the OB level of each video signal input by the addition / subtraction circuit 12 and output.
Even if the input OB level fluctuates due to environmental changes such as humidity, the OB level of each video signal is kept constant. The video signals output from the OB level correction circuits 20R, 20G, and 20B are added by an addition circuit 23 at a predetermined addition ratio to obtain a luminance signal. After that, high frequency correction is performed by the APC circuit 15,
After the γ correction is performed by the γ correction circuit 21, the γ correction is performed by the video signal processing circuit 22 in the subsequent stage to perform predetermined signal processing and output as a video signal.

The other output of the adding circuit 23 is directly input to the iris control circuit 24. The iris control circuit 24 generates an aperture control signal according to the input signal level.

According to the present embodiment described above, even if the OB level changes due to, for example, a change in the dark current, AGC gain, or a change in the clamp DC voltage, the change Δob of each signal is equal to the signal addition ratio. And the control data sent to the iris drive circuit is less affected by variations in the OB level of each channel. Further, since the addition circuit is shared, the configuration is simpler than that of the third embodiment.

As the input signal to the iris control circuit described in the third and fourth embodiments, the output signal of the OB integration control circuit having a constant OB level described in the first and second embodiments is input. It goes without saying that the iris control can be further appropriately performed.

[0045]

As described above, according to the present invention,
Even if a flaw caused by the clamp pulse appears on the OB part, the data obtained is not affected by the flaw because the OB integration operation is not performed before and after the flaw.
Therefore, correct black level integration data is obtained, and accurate black level correction is performed.

According to the present invention, even if the D signal of the Y signal
Even when a correction amount is generated such that the calculation result by the correction data calculation circuit 11 periodically repeats as shown by the correction amount X in FIG. 8 when the C voltage fluctuates, FIG.
When the signal processing is performed, a stable video signal can be obtained without periodically changing the OB level of the video signal.

Furthermore, even if the OB level changes due to a change in environment such as temperature due to, for example, a change in dark current, an AGC gain, a change in the clamp DC voltage, etc., a change Δob of each signal of the three colors in particular. Is suppressed by the sum of the signals, and the control data sent to the iris drive circuit is less affected by the variation in the OB level of each color channel. Further, when a common addition circuit is used, the circuit configuration can be simplified, and furthermore, a higher quality video signal can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an OB level correction circuit 8 according to the present invention.

FIG. 3 is a waveform chart for explaining the operation of the first embodiment according to the present invention.

FIG. 4 is an example of an OB integration control circuit 7 according to the present invention and its flowchart.

FIG. 5 is a block diagram of an imaging device according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a new OB level correction circuit 13 of the present invention.

FIG. 7 is a flowchart illustrating an operation of the imaging apparatus according to the second embodiment of the present invention.

FIG. 8 is a graph showing an operation state of the second embodiment according to the present invention.

FIG. 9 is a block diagram showing a configuration of a third embodiment of the present invention.

FIG. 10 shows OB level correction circuits 20R and 20 of the present invention.
It is a block diagram of G and 20B.

FIG. 11 is a block diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 12 is a block diagram of a first conventional imaging apparatus.

FIG. 13 is a clamp circuit diagram and a block diagram of a first conventional example.

FIG. 14 is a block diagram of an OB level correction circuit 18 of the first conventional example.

FIG. 15 is a graph showing an operation state of a conventional example corresponding to the second embodiment according to the present invention.

FIG. 16 is a block diagram of a second conventional imaging apparatus.

FIG. 17 is a block diagram of an OB level correction circuit 20 of a second conventional example.

FIG. 18 is a diagram showing a relationship between a clamp pulse according to a second conventional example, a flaw caused by clamping of an OB portion, and a gate signal output from an OB integration control circuit.

[Explanation of symbols]

 Reference Signs List 1 CCD 2 S / H circuit & AGC circuit 3 Clamp circuit 4 A / D conversion circuit 5 Signal processing circuit 6 Clamp pulse generation circuit 7 OB integration control circuit 8, 20 OB level correction circuit 9 DC voltage generation circuit 10 OB integration value detection circuit REFERENCE SIGNS LIST 11 correction data arithmetic circuit 12 addition / subtraction circuit 13 gate circuit 14 correction data detection circuit 19 black level 21 γ correction circuit 22 video signal processing circuit 23 addition circuit 24 iris control circuit 25 iris drive device 26 iris

Claims (6)

[Claims] 1. A clamp means for clamping a signal corresponding to an optical black portion of a CCD to a fixed DC voltage, a fixed DC voltage generating means for generating the fixed DC voltage, and the fixed DC voltage. O for integrating the optical black level (OB level) of the signal at predetermined intervals and detecting the OB integrated value
B integrated value detecting means, OB integral controlling means for disabling the OB integral for a certain period of time, and comparing the OB integrated value detected by the OB integrated value detecting means with a predetermined black level. A correction data calculating means for calculating a correction amount such that the two coincide with each other; and an adding / subtracting means for adding or subtracting the correction data obtained by the correction data calculating means to or from the OB level of the video signal. An imaging device characterized in that: 2. The OB integration control means according to claim 1, wherein said predetermined interval is an optical black portion of said CCD at intervals of optical black pixels repeatedly set in said CCD. Wherein the edge portion of the clamp pulse supplied to the clamp means is made ineffective for the predetermined period. 3. Clamping means for clamping a Y signal corresponding to an optical black portion of a CCD to a fixed DC voltage; fixed DC voltage generating means for generating the fixed DC voltage; OB integral value detection means for OB-integrating the optical black level (OB level) of the voltage signal at predetermined intervals and detecting the OB integral value, and OB integral value detected by the OB integral value detection means And a predetermined black level, and a correction amount calculating means for calculating a correction amount such that the two coincide with each other. Filtering is performed on the correction amount calculated by the correction amount calculating means to determine correction data. Correction data determining means for adding the correction data determined by the correction data determining means to the OB level of the video signal, or An imaging apparatus comprising: an addition / subtraction unit for performing subtraction. 4. The imaging apparatus according to claim 3, wherein the filtering of the correction amount suppresses a change in the correction amount during a period at least twice as long as a cycle of a clamp pulse supplied to the clamp circuit. Imaging device. 5. An iris, iris driving means for driving the iris, iris control means for controlling opening and closing of the iris, a plurality of image sensors, and a plurality of clamp means for clamping output signals of the plurality of image sensors. A plurality of A / D converters for converting the video signal clamped by the clamp means into digital data; and a plurality of video signals converted to digital data by the A / D converter, each corresponding to black. A plurality of detecting means for integrating the level of the portion and detecting the value; a plurality of correction data calculating means for comparing the integrated value detected by the detecting means with a predetermined level to calculate a correction amount; A plurality of addition / subtraction means for adding or subtracting a plurality of correction data obtained by the plurality of correction data calculation means to each of the video signals. The signal input to the iris control means is a correction signal based on a signal obtained by a certain ratio of a plurality of correction data respectively corresponding to the plurality of video signals. apparatus. 6. The image pickup apparatus according to claim 5, wherein the plurality of clamps are clamps for three colors of R, G, and B, and a signal input to the iris control is the addition / subtraction. An image pickup apparatus, wherein the output of the adding means for adding the outputs of the means is the plurality of video signals.