JPS62202683A - Television camera having high-sensitive image pickup tube - Google Patents

Abstract

PURPOSE:To set automatically the optimum sensitivity is response to the lightness of an object by detecting a level of an output video signal of an image pickup tube and controlling an applied voltage to an image electrode so that the level is always at a prescribed value. CONSTITUTION:A video signal fed to a video signal output terminal 2 of a SiT image pickup tube 1 is amplified by a preamplifier 3, the result is fed to a processing circuit 4. The output signal of the processing circuit 4 is branched partly and fed to an automatic sensitivity adjusting circuit 7. The circuit 7 compares the level of the video signal with the reference level to form a control signal in response to the difference. The control signal is fed to a high-voltage generating circuit 8 to generate a high voltage at an image electrode voltage input terminal 9 of the image pickup tube 1 in response to the said control voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a television camera equipped with a high-sensitivity image pickup tube whose sensitivity can be adjusted by changing the voltage applied to an image electrode, that is, a photocathode. be.

(Prior Art) As mentioned above, SEC is a high-sensitivity image pickup tube whose sensitivity can be adjusted by the voltage applied to the image electrode.
tubes and SiT tubes (Si j! ion-1nLesifi
erTarget Camera Tube) is known. For example, TV cameras using SiT tubes can provide image quality sufficient for color broadcasting even under low illuminance of about 2 lux, and can also provide image quality comparable to conventional broadcasting TV cameras even under intense sunlight. can get. In particular, TV cameras equipped with such highly sensitive SiT tubes can clearly see even dark subjects that cannot be seen with the human eye, making them useful for night surveillance, observation of the ecology of natural animals, and stars. It is widely used for observation of

To adjust the sensitivity of a TV camera equipped with the SiT tube mentioned above, a cameraman or video engineer (VIE) manually operates the sensitivity adjuster provided on the SiT camera according to the shooting situation to obtain the desired sensitivity. was.

(Problems to be Solved by the Invention) As mentioned above, the sensitivity of conventional television cameras equipped with high-sensitivity image pickup tubes has been manually adjusted. It was troublesome to have to adjust the sensitivity depending on the brightness. In addition, when observing natural animals at night, the sensitivity is high, so you have to change the sensitivity depending on whether the moon is hidden behind clouds or when it emerges from the clouds. I had to be careful and the sensitivity adjustment operation was troublesome.

In particular, the sensitivity of SiT tubes needs to be drastically changed from high sensitivity under slight moonlight to low sensitivity under intense sunlight, so it is troublesome to adjust this manually and always A considerable amount of skill was required to adjust the sensitivity to the optimum level. Furthermore, the circuit that processes the output video signal of the SiT tube is provided with a clipping function to limit the maximum output level, so the sensitivity of the SiT tube is normally set to a level higher than the required level.

Therefore, there was a drawback that adversely affected the lifespan of the SiT tube.The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, free the user from extremely troublesome sensitivity adjustment operations, and automatically adjust the sensitivity to the optimal sensitivity at all times. It is an object of the present invention to provide a television camera equipped with a high-sensitivity image pickup tube, which can increase the life of the high-sensitivity image pickup tube.

(Means for Solving the Problems) A television camera having a high-sensitivity image pickup tube according to the present invention includes a high-sensitivity image pickup tube whose sensitivity is variable depending on the voltage applied to the image electrode, and an output from the high-sensitivity image pickup tube. an automatic sensitivity adjustment circuit that compares the video signal with a reference level and generates a sensitivity adjustment signal according to the difference; It is characterized by comprising a high voltage generation circuit that applies a voltage to the image electrode to adjust the sensitivity of the image pickup tube.

(Function) The video camera equipped with the high-sensitivity image pickup tube of the present invention described above detects the level of the output video signal of the image pickup tube, and applies a voltage to the image electrode so that this level always remains at a predetermined value. By controlling the camera, the optimum sensitivity is automatically set according to the brightness of the subject, eliminating the need for the operator to perform troublesome operations to adjust the sensitivity. Furthermore, since the sensitivity is not increased more than necessary, the life of the image pickup tube can be significantly extended.

(Example) FIG. 1 is a diagram showing the configuration of an example of a television camera equipped with a high-sensitivity image pickup tube of the present invention. In this example, a SiT image pickup tube is used as the high-sensitivity image pickup tube l. The video signal supplied to the video signal output terminal 2 of the StT image pickup tube 1 is amplified by the preamplifier 3 and then supplied to the video signal amplification and processing circuit 4 . The output signal of this video signal amplification and processing circuit 4 is further passed through a video signal processing circuit 5, and the video signal is outputted to an output terminal 6 as a camera output signal. In the present invention, the output signal of the video signal amplification and processing circuit 4 is transferred to the automatic sensitivity adjustment circuit 7.
also supplied. The automatic sensitivity adjustment circuit 7 sets the level of the video signal to a reference level, for example, 100% of the video signal.
% level and form a control signal according to the difference. This control signal is supplied to the high voltage generation circuit 8, and the image pickup tube l
A high voltage is generated at the image electrode voltage input terminal 9 according to the value of the control signal.

In the television camera described above, the relationship between the sensitivity of the SiT image pickup tube 1 and the high voltage applied to the image electrode is as shown in FIG. That is, when the absolute value of the negative voltage applied to the image electrode is increased, the sensitivity of the SiT image pickup tube 1 increases almost proportionally. Therefore, if the input voltage-output voltage characteristics of the high voltage generation circuit 8 are set as shown in FIG. 3, the circuit including the SiT imaging tube mouth motion sensitivity adjustment circuit 7 and the high voltage generation circuit 8 can constitute a negative feedback circuit. Thus, the sensitivity of the SiT image pickup tube 1 is automatically adjusted by a range so that the level of the video signal becomes 100%.

In FIG. 4, the horizontal axis represents illuminance (lux), and the vertical axis represents the level of the video signal. The solid curve A shows the video signal level of the television camera according to the invention, and ranges from 2 lux to 200 lux.
The level of the video signal is 10 over a wide range of 0 lux.
It is maintained at 0% (usually 0.7 V). On the other hand, the dotted curve B shows the change in video signal level when the sensitivity is manually adjusted in a conventional television camera so that the video signal level at 2 lux becomes 100%, and the dashed curve C shows the change in the video signal level when the sensitivity is manually adjusted so that the video signal level at 2 lux becomes 100%. This figure shows the change in the video signal level when the sensitivity is manually adjusted so that the video signal level at lux is 100%. According to the present invention, as mentioned above, the sensitivity is always set to an ideal state in the operating range from 2 lux to 2000 lux, so it is possible to avoid raising the sensitivity more than necessary or accidentally lowering the sensitivity. It does not become too expensive, and the life of the SiT image pickup tube can be extended.

FIG. 5 is a circuit diagram showing a detailed configuration of an example of the automatic sensitivity adjustment circuit 7. As shown in FIG. Since this example uses a color television camera, video signals are supplied from three red, green, and blue SiT image pickup tubes to input terminals 11R, IIG, and IIB, respectively. The emitter of these video signals is connected to the resistor 12.
are supplied to the bases of emitter follower transistors 14R, 14G, and 14B, which are commonly connected to ground conductor 13 via . The video signal has a pedestal level of 3■ as shown in Figure 6A and a peak-to-peak voltage of 0.7■ at 100% of the video signal.For example, the video signal as shown in Figure 5B, C, and D are supplied to the input terminals 11R, IIG and IIB, respectively, the highest level signal among the red, green and blue video signals at each instant appears at the terminal 15 as shown in FIG. This composite video signal appearing at terminal 15 is applied to the base of a first transistor 17 constituting a current mirror amplifier 16.

At the base of the second transistor 18 of this current mirror amplifier 16 there is a resistor 19,20 and a potentiometer 21.
and the output terminal of the operational amplifier 22. The input terminal of this operational amplifier 22 is connected to a terminal 23 that receives a parabolic signal synchronized with horizontal scanning and a terminal 24 that receives a sawtooth signal synchronized with vertical scanning. The signals supplied to these terminals 23 and 24 are set appropriately, and as shown in FIG. Avoid outputting video signals in the peripheral areas. Further, by adjusting the potentiometer 21, the size of the central portion can be changed. After extracting the video signal from the center of the screen in this way, an integrating circuit 2 with variable integration time consisting of a resistor 25, a potentiometer 26 and a capacitor 27
Transistor amplifier 29 connected to Darlington through 8
supply to. If the potentiometer 26 of the integration circuit 28 is adjusted to shorten the integration time, a video signal corresponding to the highlight at the center of the screen will be output, and if the integration time is lengthened, a video signal corresponding to the average value at the center of the screen will be output. . An output terminal 30 of the transistor amplifier 29 is connected to a current summing point 32 via a resistor 31. This current addition point 32 is further connected to an output tap of a potentiometer 34 via a resistor 33. This potentiometer 34 is connected via a resistor 35 to a terminal 36 to which a power supply voltage of 9.6 V is applied, and also to the grounding staff 13 via a resistor 37.

With this configuration, the level of the video signal is compared at the current addition point 32 with the reference level determined by the potentiometer 34, and a signal corresponding to the difference is obtained.

The current addition point 32 is connected to the negative input terminal of a differential amplifier 39 via a field effect transistor (FET) 38 that controls on/off of automatic sensitivity adjustment. The configuration is such that a voltage of 9.6 V or OV is applied to the gate of this FIE 73B via the terminal 40. When applying a voltage of OV,
FET3B turns on and automatic sensitivity adjustment works.
When 9.6■ is applied, Fl! 73B is turned off and automatic sensitivity adjustment no longer works. The positive input terminal of the differential amplifier 39 is coupled to a terminal 41 to which a voltage of +3■ is applied, so as to compensate for the 3■ pedestal value of the video signal. FE
In order to manually adjust the sensitivity when T3B is off and the automatic sensitivity adjustment does not work, the negative input terminal of the differential amplifier 39 is connected to a terminal of 1.8 to 7.8 Configure so that voltage can be applied. This voltage can be arbitrarily set by operating the manual sensitivity adjustment camera provided on the television camera. In this way, a signal corresponding to the difference between the video signal level appearing at the current addition point 32 and the base level is passed through the integration/voltage shift circuit 43 including the operational amplifier 39 to obtain the desired automatic sensitivity adjustment control voltage. Convert to
This is output to the output terminal 44.

As mentioned above, according to the automatic sensitivity adjustment circuit of this example, red,
The video signal at the center of the screen is extracted from the composite video signal consisting of the video signal with the highest level among the green and blue video signals, the level of the extracted video signal is compared with the reference level, and the sensitivity is adjusted according to the difference. The control voltage for adjustment can be output to the output terminal 44. Also, the size of the center part of the screen can be adjusted arbitrarily, and any signal from the highlight to the average value of the extracted video signal can be output. can be used for automatic sensitivity adjustment, so it is possible to adjust the sensitivity according to the drawing intention.In this way, the sensitivity control voltage of 1.8 to 7.8 cm obtained at the output terminal 44 is converted to a high voltage. Supplied to generation circuit 8 (Fig. 1), approximately -3 to -9kV
This voltage is commonly applied to the image electrodes of the red, green, and blue SiT image pickup tubes. In this way, the sensitivity of these SiT image pickup tubes can be automatically adjusted so that a 100% video signal is always obtained.

(Effects of the Invention) As described above, according to the television camera equipped with the high-sensitivity image pickup tube of the present invention, the sensitivity of the image pickup tube can be automatically controlled to a Q-variable state, so that the operator does not have to carry out sensitivity adjustment operations. For example, when used for daytime monitoring or observing natural animals at night, there is no need to adjust the sensitivity according to the brightness of the surroundings or subject, making it extremely easy to use. Furthermore, since the sensitivity will not be increased more than necessary, the life of the image pickup tube will be extended.

In addition, the sensitivity is automatically adjusted to the optimal value by 31jl, so
In addition to an operating method in which the sensitivity is fixed and the lens aperture is varied by an auto-iris mechanism, an operating method in which the lens aperture is fixed and the sensitivity is automatically adjusted can also be adopted.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of an example of a television camera equipped with the high-sensitivity image pickup tube of the present invention, Figure 2 is a graph showing the relationship between the sensitivity of the image pickup tube and the image electrode voltage, and Figure 3 is the generation of high voltage. Graph showing the characteristics of the circuit, Figure 4 is a graph showing the relationship between video signal level and illuminance, Figure 5 is a circuit diagram showing the configuration of an example of an automatic sensitivity adjustment circuit, and Figures 6 A-E are the same operations. FIG. 7 is a signal waveform diagram for explaining the operation. 1...High sensitivity image pickup tube 2...Video signal output terminal 3...Preamplifier 4...Video signal amplification and processing concave surface 5...Video signal processing circuit 6...Camera output terminal 7. ...Automatic sensitivity adjustment circuit 8...High voltage generation circuit 9...Image electrode Figure 4 Skin (!Mooksun Figure 6A CD Figure 7)

Claims (1)

[Claims] 1. Compares a high-sensitivity image pickup tube whose sensitivity is variable depending on the voltage applied to the image electrode and the video signal output from this high-sensitivity image pickup tube with a reference level, and generates a sensitivity adjustment signal according to the difference. The apparatus includes an automatic sensitivity adjustment circuit, and a high voltage generation circuit that receives the sensitivity adjustment signal and applies a voltage to the image electrode to adjust the sensitivity of the high-sensitivity image pickup tube so that the level of the video signal matches a reference level. A television camera with a high-sensitivity image pickup tube characterized by: