JPS645421Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in iris drive circuits in television cameras.

In a television camera, when the photoelectric conversion surface of the image pickup tube is not being scanned with an electron beam, the iris of the optical system is closed to prevent light from entering the photoelectric conversion surface to prevent deterioration of the photoelectric conversion surface. It is necessary to prevent this.

First, a conventional iris drive circuit for a television camera will be described with reference to FIG. 1 indicates an imaging signal system, and 2 indicates an optical system. First, the imaging signal system 1 will be explained. Reference numeral 3 denotes an image pickup tube, the image pickup output of which is supplied to an image pickup signal circuit 4. In addition, image pickup tube 3
may be either monochrome or color (three-tube or one-tube type), but in any case, only one tube is shown for simplicity of explanation. 5 is an output terminal for an imaging signal (video signal).

Reference numeral 6 denotes a power source (for example, the voltage is +12V, and a battery can be used), which is connected to an input terminal of a power supply circuit (so-called power board) 8 via a power switch 7. This power supply circuit 8 outputs various voltages necessary for the television camera, and here it is shown that it supplies a heater voltage (6.3V) to the image pickup tube 3 and a predetermined operating voltage to the image pickup signal circuit 4. has been done. Reference numeral 9 denotes an on/off switch that is turned on when a preheat (power save) control signal is supplied to the terminal 10. When this switch is turned on, only the heater voltage is output from the power supply circuit 8 (that is, other voltages are not output). (not output) but is supplied to the image pickup tube 3.

Next, the optical system 2 will be explained. Reference numeral 11 denotes an iris (diaphragm mechanism), which is provided in a lens system (not shown). Reference numeral 12 denotes a motor (DC motor) as an electric drive means for driving the iris 11. Note that when no voltage is supplied to both ends of the motor 12, the iris 11 is fully open. Reference numeral 18 denotes a control signal generating circuit, which supplies a control signal to one end of the motor 12 to control the size of the aperture of the iris 11. The control signal generation circuit 18 supplies the imaging signal circuit 4 with a DC voltage related to the brightness level of the imaging output, such as the average brightness voltage, and compares it with a reference voltage from the reference voltage source 14. The operating voltage is obtained from the power supply circuit 8) 13, and the comparison DC voltage from the level comparison circuit 13 is applied to the motor 1.
2. Note that the reference voltage source 14 is
It consists of a series circuit of a variable resistor and a potentiometer connected between the power supply (obtained from the power supply circuit 8) +B and ground.

Reference numeral 15 denotes a reference voltage generating circuit, which supplies a reference voltage (for example, +5.6 V) to the other end of the motor 12 via an auto/manual changeover switch 17. This reference voltage generation circuit 15 generates a reference voltage based on the voltage from the power supply 6. Changeover switch 1
7 is a movable contact D connected to the other end of the motor 12
, an automatic fixed contact AT to which the output terminal of the reference voltage generation circuit 15 is connected, and a fixed contact MN to which the auxiliary input terminal 16 is connected. When the changeover switch 17 wants to automatically adjust the size of the aperture of the iris 11 according to the amount of light incident on the image pickup tube 3, it switches the movable contact D to the fixed contact AT and changes the size of the aperture of the iris 11. When attempting to manually adjust the size, the movable contact D is switched to the fixed contact MN. or,
The movable contact D of this changeover switch 17 is a fixed contact.
When the switch 29 is turned on in conjunction with auto white balance or auto black balance adjustment in the state of switching to MN, a control signal from the control signal generation circuit 18 is supplied to one end of the motor 12, and a control signal is supplied to the other end of the motor 12. A reference voltage (+5V) from the power supply circuit 8 is applied, which causes the iris 11 to
The aperture of is automatically adjusted according to the level of imaging output from the imaging tube 3. That is, this changeover switch 1
7 is a switch for switching between automatic and manual adjustment of the aperture of the iris 11, and furthermore, when the movable contact D of this changeover switch 17 is switched to the fixed contact MN side, the power switch 7 is turned on, Even when the switch 9 is on during preheating (power saving), by turning on the switch 29, the aperture of the iris 11 can be controlled according to the level of the imaging output.
Further, a reference voltage (for example, +5V) obtained from the power supply circuit 8 is supplied to the auxiliary input terminal 16 via a manual on/off switch 29.

In the circuit shown in FIG. 1, the operation when the movable contact D of the changeover switch 17 is switched to the fixed contact AT will be explained. When the power switch 7 is on and the switch 9 is off, one end of the motor 12 is supplied with the control signal from the control signal generation circuit 18, that is, the level comparison circuit 13, and the other end is supplied with the reference voltage from the reference voltage generation circuit 15. is supplied, so the aperture of the iris 11 is controlled according to the level of the imaging output.

When the power switch 7 is on and the switch 9 is on, the heater voltage is only supplied from the power supply circuit 8 to the image pickup tube 3.
The output voltage of No. 3 becomes the ground voltage, and this ground voltage is supplied to one end of the motor 12, and the reference voltage (+5.6 V) from the reference voltage generation circuit 15 is supplied to the other end, so that the iris 11 is closed. .

The iris 11 is similarly closed when the power switch 7 is off.

Next, in the circuit shown in FIG.
The operation when the movable contact D is switched to the fixed contact MN (forced auto state) will be explained. When the power switch 7 is on and the switch 9 is off, if the switch 29 is turned on in conjunction with auto white (or black) balance adjustment, a control signal is supplied to one end of the motor 12, and a power supply circuit is supplied to the other end. Since the reference voltage (+5V) from 8 is supplied, the aperture of the iris is controlled according to the level of the imaging output.

However, when the power switch 7 is on and the switch 9 is on, or when the power switch 7 is off, the output voltage of the level comparison circuit 13 becomes the ground voltage, and this ground voltage is supplied to one end of the motor 12. Even if the switch 29 is turned on in conjunction with auto white (or black) balance adjustment, no voltage is supplied to the other end of the motor 12, or ground voltage is supplied to the other end of the motor 12, so the iris 11 cannot be closed and the iris 11 cannot be fully opened. It will remain as it is.

In view of this point, the present invention provides that, in a state where the reference voltage can be supplied from the above-mentioned auxiliary input terminal 16 to the other end of the electrical drive means 12, the electrical drive means is supplied from the auxiliary input terminal 16 independently of the power supply circuit 8. The present invention proposes an iris drive circuit that can close the iris 11 by supplying a reference voltage to the other end of the iris 12.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to FIG. 2. In FIG. 2, parts corresponding to those in FIG. Omitted.

The iris drive circuit according to the present invention has an iris 1
1, a control signal generating circuit 18 that supplies an iris control signal to one end of the electrical driving means 12, and a control signal generating circuit 18 that supplies an iris control signal to one end of the electrical driving means 12, and a control signal generating circuit 18 that supplies an iris control signal to one end of the electrical driving means 12, and a control signal generating circuit 18 that supplies an iris control signal to one end of the electrical driving means 12. a main reference voltage generation circuit 15 that generates a reference voltage to be supplied to the control signal generation circuit 18; a power supply circuit 8 that generates an operating voltage based on the voltage from the power supply 6 and supplies it to the control signal generation circuit 18; In an iris drive circuit having an auxiliary input terminal 16 led out from the other end,
A sub-reference voltage generation circuit 19 is provided which generates a reference voltage to be supplied to the other end of the electrical drive means 12 based on the voltage from the power supply 6 independently of the power supply circuit 8. The reference voltage is supplied to the auxiliary input terminal 16.

First, the reference voltage generation circuit 15 is used as a main reference voltage generation circuit, and separately from this, the sub reference voltage generation circuit 19 is used as a main reference voltage generation circuit.
will be established. This circuit 19 generates a reference voltage (for example, +5V) to be supplied to the other end of the motor 12 as an electric drive means, based on the voltage (for example, +12V) from the power supply 6, regardless of the power supply circuit 8. This reference voltage is supplied via an on/off switch 20 from an auxiliary input terminal 16 to a changeover switch 17 to the other end of a motor 12 as an electrical drive means. In this example, this switch 20 is linked so that it turns on and off in accordance with the on/off state of switch 9, and when a preheat (power save) control signal is supplied to terminal 10, both switches 9 and 20 are turned off. .

Next, the sub reference voltage generation circuit 19 will be explained. Reference numeral 21 denotes a power supply terminal, which is connected to a midpoint between the power supply 6 and the power switch 7. The terminal 21 is grounded through a constant voltage generator 22 consisting of a series circuit of a resistor 23 and a Zener diode 24 as a constant voltage element, and the voltage (from +12V to +
The voltage (dropped to 5 V) is supplied to the non-inverting input terminal of the differential amplifier 26 of the voltage stabilizing circuit 25. Power supply terminal 21 is NPN transistor 2
7 and the emitter-collector of a PNP transistor 28 connected in series therewith are grounded. The output terminal of the differential amplifier 26 is commonly connected to the bases of the transistors 27 and 28. And the transistor 27,
28 emitters are commonly connected to the inverting input terminal of the differential amplifier circuit 26 and also connected to the auxiliary input terminal 16 through the switch 20.

Next, the operation of the circuit shown in Fig. 2 will be explained, but if the movable contact D of the changeover switch 17 is switched to the fixed contact AT, it is the same as that in Fig. 1, so the explanation will be omitted. Explain the case when

Power switch 7 is on, switches 9 and 2
When 0 is on, only the heater voltage is supplied from the power supply circuit 8 to the image pickup tube 3, so the output voltage of the level comparison circuit 13 becomes the ground voltage, and this ground voltage is supplied to one end of the motor 12. The reference voltage (+5V) from the sub-reference voltage generation circuit 19 is connected to the other end.
is supplied, the iris 11 is closed.

Power switch 7 is off, switches 9 and 20
Similarly, the iris 11 is closed when is on.

It is also possible to operate the switches 9 and 20 independently, but in that case, in addition to the above-mentioned operation, the following operations are also possible. When the switch 20 is on, the power switch 7 is on, and the switch 9 is off, a control signal is supplied to one end of the motor 12, and a reference voltage from the sub-reference voltage generation circuit 19 is supplied to the other end. The aperture of the iris 11 is controlled according to the imaging output level.

Incidentally, the power supply terminal 21 can also be derived from the connection midpoint between the power switch 7 and the input terminal of the power supply circuit 8. In that case, it goes without saying that the sub-reference voltage generation circuit 19 functions only when the power switch 7 is on.

Further, the power supply voltage supplied to the main reference voltage generation circuit 15 may be obtained from the connection midpoint between the power switch 7 and the input terminal of the power supply circuit 8.

Next, a modification of the sub-reference voltage generation circuit 19 and switch 20 shown in FIG. 2 will be explained with reference to FIG.
In FIG. 3, parts corresponding to those in FIG. 2 will be described with the same reference numerals. Power supply terminal 21 is resistor 23
It is grounded through a constant voltage generator 22 consisting of a series circuit of - diode 30 - diode 30' - Zener diode 24. Approximately 1.4V obtained at the midpoint of connection between resistor 23 and diode 30, and between diode 30' and Zener diode 24.
Two voltages having a voltage difference of
The voltage is supplied to the bases of NPN and PNP transistors 27 and 28 of the voltage stabilizing circuit 25 through the sources and drains of transistors 1 and 32, respectively. Note that the input terminal 10 is connected to the gates of the field effect transistors 31 and 32. The collector of transistor 27 is connected to terminal 21, and its emitter is connected to resistor 3.
5 to the auxiliary input terminal 16, and its base is connected to the input terminal 1 through the resistor 33.
Connected to 6. The collector of transistor 28 is grounded, its emitter is connected to input terminal 16 through resistor 36, and its base is connected to resistor 34.
It is connected to the input terminal 16 through.

Note that a plunger or the like may be used as the electric drive means 12.

According to the present invention described above, the electric drive means 12 for driving the iris 11;
a control signal generation circuit 18 that supplies an iris control signal to one end; a main reference voltage generation circuit 15 that generates a reference voltage to be supplied to the other end of the electrical drive means 12 based on the voltage from the power supply 6; an iris drive circuit having a main power supply circuit that generates an operating voltage based on the voltage from the electric drive means 6 and supplies it to the control signal generation circuit 18; and an auxiliary input terminal 16 led out from the other end of the electric drive means 12. A sub-reference voltage generation circuit 19 is provided which generates a reference voltage to be supplied to the other end of the electric drive means 12 based on the voltage from the power supply 6 independently of the power supply circuit 8. Since the reference voltage is supplied to the auxiliary input terminal 16, even in a state where the reference voltage can be supplied from the auxiliary input terminal 16 to the other end of the electric drive means 12, the auxiliary voltage can be supplied to the auxiliary input terminal 16 independently of the power supply circuit 8. The iris 11 can be closed by supplying a reference voltage from the input terminal 16 to the other end of the electrical drive means 12.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional iris drive circuit, Fig. 2 is a block diagram showing an embodiment of the iris drive circuit according to the present invention, and Fig. 3 shows a partial modification of Fig. 2. It is a circuit diagram. 1 is an imaging signal system, 2 is an optical system, 3 is an image pickup tube, 4
is an imaging signal circuit, 6 is a power supply, 7 is a power switch, 8 is a power supply circuit, 9 is a switch, 11 is an iris, 12 is a motor as an electric drive means, 15
is the main reference voltage generation circuit, 16 is the auxiliary input terminal, 1
7 is an auto/manual changeover switch, 18 is a control signal generation circuit, 19 is a sub-reference voltage generation circuit, 2
0 is a switch, and 21 is a power supply terminal.

Claims (1)

[Scope of utility model registration request] an electric drive means for driving the iris; a control signal generating circuit for supplying an iris control signal to one end of the electric drive means; and a reference for supplying the other end of the electric drive means based on a voltage from a power supply. a main reference voltage generation circuit that generates a voltage; a power supply circuit that generates an operating voltage based on the voltage from the power supply and supplies it to the control signal generation circuit; In the iris drive circuit having an auxiliary input terminal, an auxiliary reference voltage generation circuit generates a reference voltage to be supplied to the other end of the electric drive means based on the voltage from the power supply regardless of the power supply circuit. An iris drive circuit comprising: a reference voltage generating circuit; and a reference voltage from the sub reference voltage generating circuit is supplied to the auxiliary input terminal.