JPH0314866Y2 - - Google Patents

Description

[Detailed explanation of the invention] Recent television cameras are also equipped with a pattern signal source (reference video signal source) such as a color barge generator, and the captured video signal and pattern signal (reference video signal) are switched by a switching circuit. That's what I do. In such a television camera, when the switching circuit is switched to the pattern signal source side, there is a risk that the captured video signal may leak into the pattern signal (reference video signal) through the capacitance between the contacts of the switching circuit. This becomes a particular problem when the amount of light incident on the image sensor is large and the level of the captured video signal is high.

The present invention was proposed in an attempt to solve the above-mentioned problems.

The television camera according to the present invention includes an image sensor, an image sensor that is supplied with an image signal from the image sensor and processes the image signal, and a reference video signal source.
The imaging circuit includes a switching circuit that switches between an imaged video signal from an imaging circuit and a reference video signal from a reference video signal source, and a signal processing circuit to which the output of the switching circuit is supplied. Based on the above, in a television camera equipped with an automatic control circuit that automatically adjusts the imaging signal, the imaging circuit is provided with an electrical cutoff means, and when the switching circuit is switched to the reference video signal source side, the electrical cutoff means is controlled. The system electrically interrupts the captured video signal to prevent the captured video signal from leaking to the signal processing circuit through the switching circuit, and also disables the automatic control circuit.

An embodiment of the present invention (color television camera) will be described below with reference to FIG.

Reference numeral 1 designates an image pickup device, which is a single-tube color image pickup tube in this example, but may also be a three-tube color image pickup tube, a monochrome image pickup tube, or a solid-state image pickup device such as a CCD.
2 is an optical system (lens system), and 3 is an aperture (manual or automatic). The imaging output from the imaging tube 1 is the imaging circuit.
The signal is supplied to a preamplifier 4 of the PK, and its output is supplied to a variable gain amplifier (automatic variable gain amplifier) 5.

The imaging signal from the amplifier 5 is commonly supplied to a low-pass filter 6 and a band-pass filter 7, from which a luminance signal Y and a chromaticity signal C are separated and extracted. , γ correction, white level clipping, etc.) 8 and chromaticity signal processing circuit 9
supplied to A luminance signal Y that has undergone signal processing is obtained from the luminance signal processing circuit 8. A red difference signal R-Y and a blue difference signal B-Y are obtained from the chromaticity signal processing circuit 9, and are supplied to synthesis circuits 10 and 11, respectively, to determine the polarity and level of the luminance signal Y from the luminance signal processing circuit 8. It is combined and added to the corrected luminance signals ±ΔY and ±ΔY obtained through the variable circuits 12 and 13, respectively.

14 is a reference video signal source (pattern signal generation source)
This is a color bar signal generation source from which a luminance signal Y, a red difference signal RY, and a blue difference signal B-Y are output. 15 are imaged video signals from the imaging circuit PK, that is, luminance signal Y, red difference signal RY, blue difference signal B-Y, and luminance signal Y, red difference signal RY, and blue color from the color barge generator 14. A changeover switch 1 that switches the difference signal B-Y in conjunction with each other.
This switching circuit consists of 5Y, 15R, and 15B, and is constructed of an electronic switching circuit using mechanical switching elements or semiconductor switching elements.

Luminance signal Y, red difference signal R-Y, switched by each switch 15Y, 15R, 15B,
The blue color difference signal B-Y is supplied to a delay device 16 and clamp circuits 17 and 18 of an NTSC encoder EC, which constitute a signal processing circuit, respectively. The clamp circuits 17 and 18 also serve as clamp circuits for quadrature modulation of color difference signals and white balance adjustment.
We are trying to simplify the circuit. clamp circuit 17,
Red difference signal R-Y, blue difference signal B-Y from 18
are supplied to balanced modulators 19 and 20, and are mutually balanced.
Color subcarrier signals with a phase difference of 90° are balanced-modulated, and each of the modulated signals is supplied to a combiner 21 where they are combined and added. The output of the synthesizer 21 is supplied to the bandpass filter 22 to obtain a quadrature modulated carrier color signal, which is supplied to the synthesizer 23 and added to the luminance signal from the delay device 16 to generate the NTSC system signal. The color video signal is amplified by the amplifier 24 and then output to the output terminal 25.

Next, the automatic white balance adjustment circuit 27 as an automatic setting circuit (automatic control circuit) will be explained. This is the above-mentioned combiner 10, 11, polarity
Level variable circuits 12, 13, clamp circuit 17,
Including 18. The red difference signal R-Y and the blue difference signal B-Y from the clamp circuits 17 and 18 are supplied to detection circuits 28 and 29, respectively, and the respective detection outputs are sent to the auto white balance adjustment control circuit 30.
supplied to Reference numeral 31 denotes an automatic white balance adjustment activation switch. When turned on, automatic white balance adjustment is activated, and when turned off, it is canceled.

32 is a changeover switch that controls switching of the changeover circuit 15, and when the grounded movable contact m is switched to the fixed contact a side, the changeover switch 15Y of the changeover circuit 15,
15R and 15B are switched to the imaging circuit PK side,
When switched to fixed contact b, changeover switch 15
Y, 15R, and 15B are switched to the reference video signal source 14 side. Then, the reference video signal is supplied to the encoder EC so that each part of the encoder EC can be adjusted to obtain a desired output.
Furthermore, the fixed contact a of the changeover switch 32 is connected to the switch 3.
1 to the control circuit 30, fixed contact b
is connected to the switching control terminal of the switching circuit 15 and the gain control terminal of the variable gain amplifier 5. and,
When the movable contact m of the switch 32 is switched to the fixed contact a side, the automatic white balance adjustment operation can be performed by operating the switch 31, and the variable gain amplifier 5 has a normal gain or AGC control operation. Furthermore, when the movable contact m of the switch 32 is switched to the fixed contact b side, the automatic white balance adjustment operation is canceled and does not operate even if the switch 31 is operated, and the variable gain amplifier 5 has a reduced gain or The movement is destroyed.

Further, when the variable gain amplifier 5 and the changeover switch 32 switch the changeover circuit 15 to the reference video signal source 14 side, a cutoff means 33 is configured to prevent the captured video signal from leaking through the changeover circuit 15 to the encoder EC. . As a result, the leaked captured video signal is superimposed on the reference video signal and the encoder EC
This can prevent the original adjustment from becoming impossible.

Next, the auto white balance adjustment circuit 27 will be further explained. When performing white balance adjustment, a white subject is photographed using the image pickup tube 1, and the levels of the color difference signals R-Y and B-Y at that time are adjusted to match the level of the video signal during the blanking period. The level of the luminance signal Y in the color difference signal is adjusted.

In the auto white balance adjustment control circuit 30, the outputs of the detection circuits 28 and 29 are supplied to a pair of window comparators, respectively. Further, the threshold values of the pair of comparators are set to V _TL and V _TH with a predetermined width above and below the level of the video signal within the blanking period as a reference. Then, in a pair of comparators, a signal indicating that the level of the color difference signal is outside the threshold range and a signal indicating whether the level is off to the upper side or lower side are formed, and these signals are combined into a pair. are supplied to the count control terminal and up-down control terminal of the up-down counter, respectively. In this pair of counters, when the level of the color difference signals R-Y, B-Y is higher than the threshold value _VTH , the pair of counters is counted down, and when it is lower than the threshold value _VTL , the pair of counters is counted up. . Further, a clock signal from a clock signal generator is supplied to the pair of counters. Then, the count values of the pair of counters are respectively supplied to a pair of DA converter circuits and converted into DC voltages proportional to the size of the count values, and the pair of voltages (each output of the control circuit 30) are The luminance signal ±ΔY is supplied to the level variable circuits 12 and 13 and obtained through the polarity and level variable circuits 12 and 13.
supplied to

Thus, the color difference signals R-Y, B-Y are the threshold values.
When V _TH and V _TL are out of the range, the gains of the polarity/level variable circuits 12 and 13 are controlled, the levels of the luminance signals ±ΔY and ±ΔY supplied to the combining circuits 10 and 11 are adjusted, and the color difference signal Adjustments are made so that RY and BY fall within the range of threshold values V _TH and V _TL .

Next, the operation of the television camera shown in FIG. 1 will be explained. When the movable contact m of the changeover switch 32 is switched to the fixed contact a side, the changeover switches 15Y, 15R, and 15B of the changeover circuit 15 are switched to the imaging circuit PK side. At this time, image pickup tube 1
The captured image signal is supplied to the image capturing circuit PK, and the captured image signal obtained from this is supplied to the encoder EC through the switching circuit 15 and output to the output terminal 25.
NTSC color video signals can be obtained. Further, when the operating switch 31 is turned on, the auto white balance adjustment operation as described above is performed.

Further, when the movable contact m of the changeover switch 32 is switched to the fixed contact b side, the changeover switches 15Y, 15R, and 15B of the changeover circuit 15 are switched to the reference video signal source 14 side. At this time, the color bar signal from the reference video signal source 14 is supplied to the encoder EC via the switching circuit 15, and an NTSC color bar video signal is obtained at the output terminal 25. At this time, even if the temporary operation switch 31 is turned on, the automatic white balance adjustment operation is not performed. Further, the gain of the variable gain amplifier 5 becomes minimum or -∞, and the imaging signal is cut off at that point, and there is no possibility that the imaging video signal leaks into the reference video signal of the encoder EC through the switching circuit 15.

Furthermore, the auto white balance adjustment control circuit 30
The relationship between the switches 31 and 32 can also be as shown in FIG. That is, the switch 31,
32 are connected in parallel between the control circuit 30 and ground, respectively.

In this case, when the switch 32 is off, each of the changeover switches 15Y, 15R, 15 of the changeover circuit 15
B is switched to the imaging circuit PK side. At this time,
The image signal from the image pickup tube 1 is supplied to the image pickup circuit PK, and the imaged video signal obtained thereby is supplied to the encoder EC through the switching circuit 16, so that an NTSC color video signal is obtained at the output terminal 25. Furthermore, when the operating switch 31 is turned on, the auto white balance adjustment operation as described above is performed.

Moreover, when the switch 32 is on, the switching circuit 1
Each of the changeover switches 15Y, 15R, and 15B of No. 5 is switched to the reference video signal source 14 side. At this time, the color bar signal from the reference video signal source 14 is supplied to the encoder EC via the switching circuit 15, and an NTSC color bar video signal is obtained at the output terminal 25. At this time, even if the temporary operation switch 31 is turned on, the automatic white balance adjustment operation is not performed. Further, the gain of the variable gain amplifier 5 becomes minimum or -∞, and the imaging signal is cut off at that point, and there is no possibility that the imaging video signal leaks into the reference video signal of the encoder EC through the switching circuit 15.

Note that a microcomputer may be provided in the control circuit 30 to perform automatic white balance adjustment. That is, the level of the blanking period in the color difference signal is sampled, and this level is
The level of the image period in the color difference signal is sampled, this level is A-D converted and stored in the memory of the microcomputer, the difference between these levels is calculated, and the The polarity/level variable circuits 12 and 13 are controlled based on the calculation results.

In this case, a program may be provided to the microcomputer so that when the switch 32 in FIG. 2 is turned on, the automatic white balance adjustment operation is not performed.

Note that the reference video signal source 14 may be a signal source such as a crosshatch pattern signal, a dot pattern signal, or a test pattern signal.

Further, the automatic setting circuit 27 may be an automatic black balance adjustment circuit, an automatic pedestal setting circuit, an automatic centering circuit, or the like.

According to the above-described television camera of the present invention, when the switching circuit is switched to the reference video signal source side, the possibility that the captured video signal leaks into the reference video signal through the switching circuit is avoided. This is particularly effective when the amount of light incident on the image sensor is large.

Furthermore, according to the present invention described above, when the switching circuit is switched to the reference video signal source side, the automatic control circuit (automatic setting circuit) is deactivated, so that the switching circuit then switches to the imaging circuit. If the switching circuit is switched to the reference video signal source side, there is no risk of incorrect automatic control being performed due to erroneous data captured when the switch was switched to the reference video signal source side, and if the switching circuit is switched to the reference video signal source side. , there is no risk that the automatic control circuit (automatic setting circuit) will perform unnecessary and erroneous automatic control (automatic setting) on the reference video signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram showing a part of another embodiment. 1 is an image sensor, PK is an image sensor, 14 is a reference video signal source, 15 is a switching circuit, EC is an encoder,
27 is an automatic setting circuit, and 33 is a cutoff means.

Claims (1)

[Scope of utility model registration request] an imaging device, an imaging circuit to which an imaging signal from the imaging device is supplied and processes the imaging signal, a reference video signal source, an imaging video signal from the imaging circuit, and a reference video signal from the reference video signal source. and a signal processing circuit to which the output of the switching circuit is supplied, and the imaging circuit includes an automatic control circuit that automatically adjusts the imaging signal based on the output of the signal processing circuit. In the television camera, the imaging circuit is provided with an electrical cutoff means, and when the switching circuit is switched to the reference video signal source side, the electrical cutoff means is controlled to electrically cut off the captured video signal. The television camera is configured to shut off the captured video signal to prevent the captured video signal from leaking to the signal processing circuit through the switching circuit, and to disable the automatic control circuit.