JPH03132262A - Camera signal processing circuit - Google Patents

Abstract

PURPOSE:To prevent deterioration in the signal accuracy of an absolute black level of an optical black waveform portion by inserting a replacement black waveform part representing a relative black level into a video signal in addition to the optical black waveform portion representing an absolute black level. CONSTITUTION:A replacement black waveform portion W24 representing a relative black level is inserted to a video signal in addition to an optical black waveform portion W22 representing an absolute black level by utilizing horizontal blanking line feedback. Thus, since a signal level of the replacement black waveform portion W24 is clamped as to a signal processing stage executing the signal processing based on the relative black level actually, the opportunity of causing noise to the absolute black level or making dirt in the optical black waveform portion W22 is less. Thus, the signal accuracy of the absolute black level is not deteriorated and a video signal with excellent picture quality is sent from a camera.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A: Industrial field of application B: Overview of the invention C: Prior art (Figs. 5 to 7) D: Problems to be solved by the invention (Figs. 6 and 7) E: Means for solving the problems (Figures 1 to 4) Effect of F (Figures 1 to 4) Example C (G1) First example (Figures 1 to 4) (G2) Other examples H Effects of the invention A. Field of Industrial Application The present invention relates to a camera signal processing circuit, and is particularly applicable to a camera signal processing circuit that clamps the black level constituting a television video signal.

B. Summary of the Invention The present invention provides a camera signal processing circuit that inserts a replacement black waveform section in addition to the optical black waveform section, thereby improving the optical black waveform section constituting the television image signal. It is possible to prevent signal accuracy from deteriorating.

CConventional technologyFor example, CCD (charge coupled
In a television camera having an imager consisting of a device), black level information representing optical black at the time of shooting is inserted into the horizontal retrace period as a reference level of the television video signal, and the luminance is adjusted based on this black level information. A camera signal processing circuit is used in which signal processing for forming signals and chroma signals is performed in a number of sequentially connected signal processing stages.

In this type of conventional camera signal processing circuit, in order to insert black level information into the horizontal retrace period of the imaging signal obtained from the imager, as shown in FIG.
An optical black surface 2B, which is shielded from light in advance, is installed adjacent to the side of the imaging m2A of the imager 2 constituting the imager 2. The photoelectric conversion output S1 obtained from the CCD element constituting the imaging surface 2A and the optical black surface 2B is transferred to a horizontal register. 2C and passes through the amplifier circuit 3 to the imaging signal S2.
The image signal is sent to the image signal output terminal P1 as a signal.

The image signal S thus sent to the image signal output terminal P1
2 (Fig. 7 (A)) is a CD S as shown in Fig. 6.
(Correlated Double Sample
ng) sampled in the sampling circuit 5,
Video human input signal S through automatic gain control circuit (AGC) 6
3 (FIG. 7(B)) and is supplied to the clamp circuit 7.

Here, the lift/damage signal 32 (FIG. 7(A)) is generated during an imaging plane scanning period T having one horizontal scanning period (this is called an LH period).
The optical black surface scanning period T following the image waveform part W1 obtained by scanning the imaging surface 2A in 1
2, an optical black waveform portion W2 obtained by scanning the optical black surface 2B;
The signal configuration is such that blank waveform portions W3 and W4 are provided before and after the image waveform portion W1 and the optical black waveform portion W2.
B)) has an image waveform portion S3 and an optical black waveform portion W12 in the imaging surface scanning period Tl and the optical black surface scanning period T2, respectively, and has a blank waveform portion W13 and an optical black waveform portion W12 in the preceding and following blank periods T3 and T4, respectively. It exhibits a signal waveform having W14.

As shown in FIG. 7(C), the clamp circuit 7 generates an optical black waveform portion W1 by a clamp pulse CLP rising during the optical black surface scanning period T2.
At the same time, the signal level of the other waveform portions W11.2 is clamped. ．． The clamp output signal 314 obtained by passing W13 and W14 as is is supplied to the signal processing circuit section 8, and the signal processing circuit section 8 performs signal processing to give the necessary characteristics as a video signal, and then outputs the video output signal S5. It is sent to the video output terminal P2 as a video output terminal P2.

Problems to be Solved by the Invention D In the conventional configuration described above, the signal processing circuit section 8 processes a part of the clamp output signal S4 supplied from the clamp circuit n7,
That is, by clamping the signal level of the optical black waveform part W12 at that timing with the clamp pulse CLP1 as the waveform of the optical black surface scanning period T2, this is used as the reference black level signal in the scanning screen part to perform γ correction. A signal that determines the operating point when performing signal processing such as brightness signal setup, set-up processing, chroma signal carrier balance processing, IH delay circuit gain adjustment processing, aperture control processing, horizontal synchronization signal input acquisition processing, etc. used as

In reality, the signal processing circuit unit 8 has a large number of signal processing stages that execute these processes, and when executing the processing assigned to each signal processing stage, the clamp circuit 7 uses the IH input signal to perform the processing assigned to each signal processing stage. Optical black waveform part W1
By re-clamping the signal level clamped to 2 (FIG. 7(B)) each time, the assigned predetermined signal processing is executed using the on-duty clamp level as the reference black level.

However, in this case, until the video output signal S5 is sent to the video output terminal P2 of the signal processing circuit unit 8 based on the imaging signal S2 sent from the solid-state imaging device I,
Since the reference black level is repeatedly clamped each time signal processing is performed in a large number of signal processing stages included in the signal processing circuit unit 8, the reference black level is superimposed on the optical black waveform part W2 of the input image signal each time. The black level when the black reference level is captured is based on changes in the clamp level due to the clamp operation in response to noise, or dirt caused by the clamp pulse leaking in and deforming the optical black waveform. There is a risk of deviation.

In practice, the amount of deviation is considered to increase as the number of signal processing stages that require clamping increases. There is a problem that the error becomes large.

The present invention has been made in consideration of the above points, and is a camera signal processing circuit that is capable of suppressing errors as much as possible in a signal processing stage in which it is essential to use an absolute black level as a reference. This is what we are trying to propose.

E Means for Solving the Problem In order to solve this problem, in the present invention, an optical black waveform part W22 is inserted into a part of the horizontal scanning retrace period waveform part of the imaging signal 312 obtained from the imager 13. At the same time, black level insertion means 17 inserts a replacement black waveform part W24 having a second signal level corresponding to the first signal level of the optical black waveform part W22 into the other part of the horizontal scanning blanking period waveform part. should be established.

By inserting the replacement black waveform part W24 in addition to the F-action optical black waveform part W22,
By being able to supply relative black level information by the black waveform unit W24 as a replacement for a signal processing stage that requires a relative black level as a reference value, the optical black waveform unit W can be supplied to a signal processing stage that requires a relative black level as a reference value.
Since it is no longer necessary to clamp the optical black waveform portion W22, the signal accuracy of the optical black waveform portion W22 can be prevented from deteriorating.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

(Gl) First Embodiment In FIG. 1, the video signal processing circuit 11 uses the timing signal Sll generated in the timing signal generation circuit
The imaging signal 512 (FIG. 2(A)) obtained by operating the solid-state imaging device 13 in a damaged manner is sent to the CDS sampling circuit 1 of the image processing circuit main body 14 having a tC circuit configuration.
5 and subjected to sampling processing, it is inputted to the black level clamp switching circuit 17 as a video input signal 313 (FIG. 2(B)) through the automatic gain control amplifier circuit 16.

As shown in FIG. 3, the black level clamp switching circuit 17 receives the video input signal 313 from the DC level shifter 21 and supplies the level shift output signal 314 obtained at its output terminal to the comparison input terminal of the comparison circuit 22.

On the other hand, the reference voltage output 315 of the reference voltage source 23 is applied to the reference input terminal of the comparator circuit 22, so that the voltage level of the level shift signal 314 and the reference voltage output S15 are
When there is a difference between the voltage level of S16, the difference output S16
is held in the output capacitor 24 and given as a shift control signal to the DC level shifter 21, and thus the comparator circuit 22 performs feedback control so that the DC level of the level shift output signal S14 matches the reference voltage output 315.

The level shift output signal S14 is a level shift output signal 31 applied to the video signal input terminal I of the input switching circuit 25.
4 and the changeover level signal 317 applied to the signal input terminal I8 as a pre-blanking signal 318 (FIG. 2(C)).
) (supplied from the timing signal generation circuit 12 through pin P12 and output from the clamp switching circuit 17 while being switched by i) as a black level signal 519 (FIG. 2(D)).

In this way, the clamp change change output signal 319 generates the change blanking period T4X within the blank blanking period by the fall of the blank blanking signal SlB, and during this blank blanking period T4X, the change level signal 317 The voltage level is inserted into the clamp 1 replacement output signal S19 (FIG. 2(D)) as a black waveform portion W24.

In this embodiment, the switching level signal S1'7 is the reference voltage output 315 of the reference voltage source 23, which is output by the level processing circuit 26.
By performing the level adjustment process 2, the constant voltage level signal 317 of the same voltage rail as the optical black waveform part W2 (FIG. 2(A)) of the video input signal 313 is made to be m2.

In addition to this configuration, a black level clamp replacement circuit A 17 is provided.
The comparator circuit 22 (FIG. 1) receives an optical link clamp signal (No. 8 520 (FIG. 2 (E
)), a comparison operation is performed between the pulse widths, and thereby the voltage level of the optical black waveform portion W12 of the video input signal 313 is set to the reference voltage output S15 every IH scanning period. It is made to repeat.

The clamp switching output signal 319 obtained at the output terminal of the black level clamp switching circuit 17 in this manner is supplied to the chroma signal processing section 31 and the luminance signal processing section 32.
In various signal processing stages constituting the chroma signal processing section 31 and the luminance signal processing section 32, the signal level of the optical black waveform part W22 of the clamp replacement output signal 319 can be clamped by the optical black clamp pulse signal 320. being done.

In addition, the black level clamp switching circuit 17, the chroma signal processing section 31, and the luminance signal processing section 32 are supplied with switching pulses generated during the falling section of the blanking signal 31B in the timing signal generation circuit 12. A signal 521 (FIG. 2 (F)) is given, and this causes the chroma signal processing section 31 and the luminance signal processing section 32 to change the voltage level corresponding to the switching black waveform part W24 during the pulse width of the switching pulse signal 321. It is designed so that it can be clamped to the constituent signal processing ends.

In the black level clamp replacement circuit 17 of FIG.
When the video input signal 313 arrives, the preceding blank period T
3. During the raised and damaged surface scanning period T1 and the optical black surface scanning period T2, the output switching circuit 25 is switched to the video signal input terminal ■1 side by the blanking pulse 318, so that the video signal 513 (see FIG. Among B)), the signal portions of the front blank waveform portion W13, video waveform portion Wll, and optical black waveform portion W12 are input as the level shift output signal 314 of the DC level shifter 21 to the video signal input terminal! , as a clamp changeover output signal 319, as shown in FIG. 2(D),
The black level clamp switching circuit 17 outputs the blank waveform portion W23, the video waveform portion W21, and the optical black waveform portion W22.

On the other hand, during the blanking period T4X, which is the falling period of the blanking pulse 31B, the output switching circuit 25 switches to the side switching signal input terminal 13, so that the level switching circuit 26 sends out the level switching level signal S17. is sent as the clamp transition output signal 519, so that the transition black waveform portion W24 having the voltage level of the transition level signal 517 is outputted from the black level clamp transition switching circuit 17.

In the above configuration, when the front blank waveform portion W3, the video waveform portion Wl, the optical link waveform portion W2, and the rear blank waveform portion W4 are sequentially transmitted from the solid-state imaging device 13 every horizontal scanning period ( 2(A)), and correspondingly, the front blank waveform portion W is output as the video input signal 513 (FIG. 2(B)).
13. Video waveform section Wl 1. The optical black waveform portion W12 and the trailing blank waveform portion W14 are sequentially input to the black level clamp switching circuit 17.

Among these waveform parts, the front blank waveform part W13 and the video signal waveform part Wl 1. The optical black W12 passes through the output switching circuit 25 as it is and is output as the blank waveform part W23, the video waveform part W211, and the optical black waveform part W22 of the clamp switching output signal 319 (FIG. 2 (D)). On the other hand, video input signal 3
23, the timing at which the blank waveform portion W14 arrives (therefore, the timing when the optical black waveform portion W2 of the horizontal scanning period arrives)
2 is inserted), the output switching circuit 25 switches to the side change signal input terminal I3 side, so that the signal level of the step change level signal 517 is used instead of the trailing blank waveform section W14. The replacement black waveform portion W24 is then inserted and output.

In this way, the optical black surface scanning period T2 and the pre-blanking period T4X following the video waveform portion W21
During this period, the optical black waveform part W22 and the replacement black waveform part W24 are sequentially output to the chroma signal processing section 31 and the luminance signal processing section 32, but the inside of the chroma signal processing section 31 and the luminance signal processing section 32 is The signal processing stage includes an optical black clamp pulse signal 5.
20 (Fig. 2 (E)) and a replacement pulse signal 521 (
(F) in FIG. 2 are given at the timing when the optical black waveform portion W22 and the replacement black waveform portion W24 are supplied, respectively, so that the signal level of the optical black waveform portion W22 is set to the optical level by the optical black clamp pulse signal S20. The black clamp pulse signal 320 is clamped at the signal processing stage given, and then the black waveform section W24 is switched to the signal processing stage given the switched pulse signal s21.
signal level is clamped.

Here, the signal processing stages constituting the chroma signal processing section 31 and the luminance signal processing section 32 are a signal processing stage group 31ZB and 32ZB that require the black level of the optical black waveform part W2 of the imaging signal 312 as absolute black level information. The signal processing stage groups 31SB and 32SB are classified into signal processing stage groups 31SB and 32SB, which only need to set the black level of the video signal to be processed so that the video signal to be processed falls within the dynamic range of the signal processing stage. 1 signal processing stage group 31Z
The optical black clamp pulse signal S20 is given to B and 32ZB, whereas the signal processing stage group 31 requires a black level corresponding to the dynamic range.
A switching pulse signal S21 is given to SB and 32SB.

Thus, the absolute black level signal processing stage groups 31ZB and 32Z
In contrast to clamping the absolute black level based on the optical black waveform portion W22 of the output signal S19, a relative black level signal processing stage group 31S is used.
B and 323B clamp the relative black level by the switching pulse signal S21.

Therefore, according to the configuration shown in FIG. 1, while the relative black level signal processing stage groups 31SB and 32SB clamp the relative black level, the absolute black level signal processing stage groups 31ZB and 32Z
By not performing a clamping operation on B, it is possible to effectively avoid the possibility that signal accuracy will be degraded due to noise generation in the optical black waveform section 322 or leakage of clamp pulses.

In this embodiment, the absolute black level signal processing stage group 31ZB
Alternatively, 32ZB includes a gamma correction processing stage, a brightness signal setup processing stage, and a chroma signal carrier balance processing stage, and relative black level signal processing stage groups 31SB and 32SB include a gain adjustment processing stage for the lH delay circuit and an aperture processing stage. A control processing stage and a horizontal synchronization signal input acquisition processing stage can be assigned.

As one example, the configuration shown in FIG. 4 can be assigned as the absolute black level signal processing stage and the relative black level signal processing stage included in the luminance signal processing section 32.

That is, a gamma correction circuit 41 is provided as a signal processing stage included in the luminance signal absolute black level processing stage group 32ZB in a part of the IC circuit constituting the video signal processing circuit main body section 14, and a gamma correction circuit 41 is provided as a signal processing stage included in the luminance signal absolute black level processing stage group 32ZB. 3) is clamped from pin P21 in the clamp circuit 42, and its clamp output S36 is given to the gamma correction circuit 41.

An optical black clamp pulse signal 520 (FIG. 2 (E)) is given to the clamp circuit 42, which causes a clamp replacement output signal 519 (FIG. 2 (D)).
The signal level of the optical black waveform portion W22 is clamped, and thus a clamp output S31 obtained by clamping the absolute black level can be supplied to the gamma correction circuit 41.

Gamma correction output S32 is an IH externally connected to pin P22.
It is delayed in the delay circuit 42, and the delayed output S33 is sent to the relative black level signal processing stage group 31SB through the pin P23.
is applied to the gain control signal processing stage that constitutes the.

The gain control signal processing stage has a gain control circuit 43, which clamps the delayed output 333 in a clamp circuit 44 and then supplies the clamp output S34 to the gain control circuit 43.

The clamp circuit 44 receives a replacement pulse signal 521 (second
(F)) is given, and as a result, a clamp output S34 obtained by clamping the signal level of the black waveform section W24 of the clamp change output signal 519 (FIG. 2 (D)) is sent to the gain control circuit 43. Supplied.

As a result, the gain control circuit 43 outputs the clamp output S
The gain of the video waveform portion of the clamp output S34 can be appropriately controlled within a predetermined dynamic range based on the signal level of the black waveform portion S24 clamped by the changeover pulse signal 321 among the three four.

Therefore, when setting the reference signal of the gain control circuit 34, the optical black waveform portion W22
By eliminating the need to perform clamp processing on the signal level, it is possible to prevent clamp noise from being mixed into the optical black waveform portion W22 included in the clamp output S34, and from leaking a clamp pulse.As a result, the gain control When the gain control output S32 sent from the circuit 43 to the pin P24 is subjected to set-up processing of a luminance signal in a subsequent set-up circuit (not shown), it is possible to suppress the occurrence of calculation errors.

According to the above configuration, in addition to inserting the optical black waveform portion W22 representing the absolute black level using the horizontal retrace period, a replacement black waveform portion W24 representing the relative black level is inserted. As a result, the signal processing stage that actually performs signal processing based on the relative black level can be replaced by clamping the signal level of the black waveform section W24, thereby reducing the absolute black level of the optical black waveform section W22 accordingly. It is possible to reduce the chances of noise generation or staining, and therefore, the signal accuracy of the absolute black level does not need to be degraded, so that a video signal with even better image quality can be sent out from the camera.

(G2) Other Embodiments (1) In the above-mentioned embodiments, an embodiment was described in which the present invention was applied to a television camera using COD as an imager, but the present invention is not limited to this. It can be widely applied to other solid-state image sensors and television cameras using cathode ray tubes.

(2) In the above-described embodiment, a case was described in which the replacement black waveform section W24 (FIG. 2 (D)) clamps a signal level that is almost the same as the signal level of the optical black waveform section W22. However, the signal level of the transition black waveform portion is not limited to this, and may be shifted to a higher or lower value by a predetermined voltage.

Effects of the Invention As described above, according to the present invention, the dynamic range of the circuit can be increased by inserting into the video signal a replacement black waveform portion representing the relative black level in addition to the optical black waveform portion representing the absolute black level. By not clamping the optical black waveform portion as the reference level of the signal processing stage that requires a relative black level to the determined reference signal level, it is possible to prevent the signal accuracy of the absolute black level of the optical black waveform portion from deteriorating accordingly. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the camera signal processing circuit according to the present invention, FIG. 2 is a signal waveform diagram showing signals of each part thereof, and FIG. 3 is a block diagram showing an embodiment of the camera signal processing circuit according to the present invention. FIG. 4 is a block diagram showing the detailed configuration of the luminance signal processing section 32 in FIG. 1;
FIG. 6 is a block diagram showing a solid-state imaging device, FIG. 6 is a block diagram showing a conventional camera signal processing circuit, and FIG. 7 is a signal waveform diagram showing signals of each part in FIG. 11...Video signal processing circuit, 12...
Timing signal generation circuit, 13... Solid-state imaging device, 14... Video signal processing circuit main body, 17.
...Black level clamp replacement circuit, 31...
...Chroma signal processing unit, 31ZB... Absolute black level signal processing stage group, 313B... Relative black level signal processing stage group, 32... Luminance signal processing unit, 3
2ZB...Absolute black level signal processing stage group, 32S
B...Relative black level signal processing stage group.

Claims (1)

[Claims] An optical black waveform portion is inserted into a part of the horizontal scanning blanking period waveform portion of the imaging signal obtained from the imager, and the optical black waveform is inserted into another portion of the horizontal scanning blanking period waveform portion. 1. A camera signal processing circuit comprising: black level insertion means for inserting a replacement black waveform portion having a second signal level corresponding to a first signal level of the camera signal processing circuit.