JPH024541Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television camera device that uses a vidicon as an image pickup tube and has a function to adjust its sensitivity.

As shown in FIG. 1, a conventional television camera device of this type connects the electrode of the target 2 of the vidicon 1 to the output end of the automatic sensitivity adjustment circuit 14 via the load resistor 4, and connects It is connected to the input end of the preamplifier 6 via the capacitor 5, and the positive voltage obtained at the output end of the automatic sensitivity adjustment circuit 14 is applied to the target 2 through the load resistor 4, which is obtained when scanning the electron beam. A signal current corresponding to the amount of incident light is input to a preamplifier 6 through a coupling capacitor 5. The signal voltage amplified by this preamplifier 6 is then transferred to a smoothing circuit 11 consisting of a resistor 12 and a capacitor 13.
The comparison amplifier 15 compares the voltage with a reference voltage preset in the reference voltage source 16, and the base of the control transistor 17 is controlled based on the difference voltage to obtain the target voltage applied to the target 2. The sensitivity is automatically adjusted by controlling the . In this case, a well-known preamplifier 6 is usually used, and this preamplifier 6 is mainly used for high impedance amplification in the first stage.
A FET (field effect transistor) element 7, a final stage amplifier 9, an output terminal of this amplifier 9, and the FET
It consists of a feedback resistor 10 inserted between the gates of the FET element 7, and is configured to amplify the signal output from the vidicon 1 input to the gate of the FET element 7 to a desired level.

Note that 8 is the drain resistance of the FET element 7,
The cathode 3 of the busicon 1 is grounded. Further, the collector of the control transistor 17 constituting the automatic sensitivity adjustment circuit 14 is connected to the drive power supply +B via a collector resistor 18, and its emitter is grounded via an emitter resistor 19.

However, in such a conventional television camera device, since the target voltage of the vidicon 1 normally varies between 20 and 70V with respect to the cathode 3, a coupling capacitor 5 is connected between the vidicon 1 and the first stage circuit of the preamplifier 6. and load resistor 4 is required. Therefore, the first stage circuit of the preamplifier 6 becomes susceptible to thermal noise caused by the coupling capacitor 5 and the load resistor 4, resulting in a decrease in the S/N ratio and The drawback was that the size impeded miniaturization.

The present invention was developed with these points in mind, and its purpose is to perform automatic sensitivity adjustment by controlling the cathode voltage applied to the cathode of the image pickup tube, and to connect the target of the image pickup tube to the input of the preamplifier. It is an object of the present invention to provide a television camera device which can improve the S/N ratio and reduce the size by directly connecting the device to the end side, thereby omitting a coupling capacitor and a load resistor.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.

FIG. 2 is a circuit configuration diagram of essential parts showing an embodiment of the television camera device according to the present invention. In the figure, the electrode of the target 2 of the vidicon 1 is connected to the input end of the preamplifier 6, that is, the gate of the first stage high impedance amplification FET element 7, and its drain is connected to the input end of the amplifier 9. One of the output terminals of this amplifier 9 is a feedback resistor 10
connected to the gate of the FET element 7 via
The other one is connected to the negative input end of the comparator amplifier 15 via a resistor 12 that constitutes the smoothing circuit 11 . Further, a positive reference voltage preset by a reference voltage source 16 is applied to the positive input terminal of the comparator amplifier 15, and its output terminal side is connected to the base of the level shift transistor 17a. and,
The emitter of the transistor 17a is connected to the drive power supply Vcc via the emitter resistor 19, and the collector thereof is connected to the negative drive power supply -B via the collector resistor 18, and is also connected to the cathode 3 of the busicon 1. . Note that the preamplifier 6, smoothing circuit 11, and automatic sensitivity adjustment circuit 14 are basically the same as those used in the prior art.

Next, the operation of the above embodiment will be explained. Here, when the vidicon 1 is scanned by an electron beam, a signal current from the target 2 flows through the input impedance of the preamplifier 6 as a load. Thereby, the signal current is amplified by the preamplifier 6 and taken out as a signal voltage. At this time, when the output signal voltage of the preamplifier 6 is smoothed by the smoothing circuit 11 and inputted to the comparison amplifier 15 of the automatic sensitivity adjustment circuit 14, this comparison amplifier 15 combines the output signal voltage from the preamplifier 6 with the reference voltage. A reference voltage set in advance is compared with the voltage source 16, and the difference voltage is applied to the base of the level shift transistor 17a. As a result, the base voltage of the transistor 17a is controlled by the differential voltage of the comparison amplifier 15, so that the cathode voltage applied to the cathode 3 of the vidicon 1 is controlled to be constant. Therefore, the collector potential of the transistor 17a is lower than the target 2 of the vidicon 1, and the potential difference therebetween is equal to the potential difference between the cathode 3 of the vidicon 1 and the target 2, as in the conventional case.
That is, by shifting the cathode voltage of the vidicon 1 by the target voltage and controlling this cathode voltage based on the differential voltage from the automatic sensitivity adjustment circuit 14, the sensitivity can be automatically adjusted. Therefore, target 2 of busicon 1
There is no need to apply a target voltage to the FET element 7, and the target voltage can be operated at the same potential as the gate of the FET element 7. Therefore, according to the above embodiment, the conventional load resistor 4 shown in FIG.
Also, the coupling capacitor 5 can be omitted.

As explained above, according to the television camera device according to the present invention, it is possible to make the potential of the target of the image pickup tube equal to the potential of the gate of the first-stage high-impedance amplification FET element constituting the preamplifier. As a result, a load resistor and a coupling capacitor can be omitted.
Therefore, the effect of noise on the first stage circuit of the preamplifier is eliminated, the S/N ratio can be improved, and the circuit configuration can be simplified to reduce the size.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit configuration diagram showing a conventional television camera device, and FIG. 2 is a circuit configuration diagram of essential parts showing an embodiment of the television camera device according to the present invention. 1... Busicon, 2... Target, 3... Cathode, 6... Preamplifier, 7... FET constituting the first stage high impedance amplifier circuit, 10...
Feedback resistor, 11... Smoothing circuit, 14... Automatic sensitivity adjustment circuit, 15... Comparison amplifier, 16... Reference voltage source, 17a... Level shift transistor,
18...Collector resistance, 19...Drain resistance.

Claims (1)

[Scope of utility model registration request] In a television camera device equipped with a preamplifier that inputs the signal output of the image pickup tube to the first-stage high-impedance amplification FET element, the signal output of the preamplifier is smoothed, and the output voltage and the preset standard are This can be achieved by providing an automatic sensitivity adjustment circuit that compares the voltage and controlling the cathode voltage applied to the cathode of the image pickup tube based on the difference voltage, and by directly connecting the target of the image pickup tube to the gate of the FET element. The potential of the target is set to the FET.
A television camera device characterized in that the potential is equal to the potential of the gate of the television camera device.