JPH0334730Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an automatic aperture control device for a television camera that adjusts the aperture of the amount of light incident on the image pickup tube within a reference range in response to the brightness of the subject. If left in the open state, the image pickup tube light-receiving surface will be illuminated without corresponding aperture control when the subject brightness increases, and the automatic aperture control device will be activated to prevent the light-receiving surface from being burnt out. When the power supply is cut off, the aperture is automatically reduced to a closed control state.

Conventionally, as this type of device, for example,
As described in Publication No. 50-34231, the aperture is set in the open direction,
Among two power supplies that operate in the closing direction and two power switches provided for each, by shutting off one power switch and delaying the shutoff of the other power switch, the diaphragm can be moved in the closing direction by the other power supply. A configuration that narrows down the aperture unilaterally, or, as described in Japanese Utility Model Application Publication No. 50-66647, maintains power supply to the aperture drive motor after the power switch is shut off, and at the same time irradiates the light receiving element with high brightness. or, as described in Japanese Utility Model Application Publication No. 48-5617, when the power switch of the diaphragm control circuit is cut off, the power source for closing the diaphragm is turned off by an electromagnetic relay. Some devices are known that switch to batteries, but all of these conventional devices use power from the power source to narrow the diaphragm in the closing direction after the power switch is shut off, so this method also includes the removal of the power source. There was a problem that the device could not operate if the power supply was shut off.

Therefore, the present invention aims to provide an automatic aperture control device for a television camera that eliminates these drawbacks, and the gist thereof is as described in the claims of the utility model registration.

The present invention will be explained in detail with reference to the embodiments shown below. FIG. 1 is a circuit diagram of the main parts of an automatic diaphragm device, in which 1 is the positive voltage side of the power supply circuit, and 2 is the zero voltage side. 3 is the aperture drive coil of the servo mechanism; when current flows in the forward direction shown by arrow A in the figure, it drives the aperture in the closing direction, and when current flows in the opposite direction of arrow A, it drives the aperture in the open direction. It is set to do so. Reference numerals 4 and 5 denote switching elements consisting of switching transistors that control power supply to the aperture drive coil 3 in the forward direction, and are connected in series to the power supply circuit via the coil 3.
turns ON when the voltage of base 4a rises above the specified range
However, the switching element 5 is configured to turn on when the voltage of the base 5a falls below a predetermined range. Reference numerals 6 and 7 indicate switch elements that control power supply in the opposite direction to the aperture drive coil 3, which are connected in series to the power supply circuit via the coil 3. The switch element 7 consists of a switching transistor that turns on when the voltage at its base 7a falls below a predetermined range. The bases 4a and 7a of the switch elements 4 and 7 are resistors R1 and R2, respectively.
The bases 6a, 5a of the switch elements 6, 5 are connected through resistors R3, R4, respectively. It is connected in series to the power supply circuit, and also connected via two diodes D3 and D4.
Reference numeral 8 denotes an inverting amplification circuit for the light reception output signal 10 of the television camera, and its output terminal 8a is connected between the diodes D1 and D2 to provide an output voltage that increases in accordance with the increase in subject brightness. Further, 9 is an inverting amplifying circuit which further inverts and amplifies the output voltage of the inverting amplifying circuit and applies an inverse output voltage from its output terminal 9a between the diodes D3 and D4, and when the voltage at the output terminal 8a increases or decreases, The relationship is such that the voltage at the output terminal 9a decreases and increases conversely.
Therefore, when the amount of light received by the television camera increases and the voltage at the output terminal 8a increases, the voltage at the output terminal 9a decreases, and the base 4a of the switch element 4 accordingly decreases.
When the voltage at the switch element 5 exceeds a predetermined range and turns on, at the same time the voltage at the base 5a of the switch element 5 falls below a predetermined range and turns on, power is supplied to the aperture drive coil 3 in the forward direction (direction of arrow A), and the aperture is turned on. is driven in the closing direction to limit the amount of light received by the television camera. On the other hand, as the amount of received light decreases and the voltage at the output terminal 8a drops, the voltage at the output terminal 9a increases, and as a result, the voltage at the base 7a of the switch element 7 increases. When the voltage falls below a predetermined range and turns on, at the same time the voltage at the base 6a of the switch element 6 rises above a predetermined range and turns on.
and the aperture drive coil 3 in the opposite direction (counter arrow A direction)
is supplied with power, and the diaphragm is driven in the opening direction.As a result, the diaphragm is automatically controlled so that the television camera always obtains an appropriate amount of light received within the reference light amount range.

As shown in FIG. 2, the automatic diaphragm control device according to the present invention has two capacitors C1 and C2 connected in parallel through resistors R5 and R6, respectively, in the power supply circuit. These capacitors C
1 and C2 charging circuits are configured. A discharge circuit 11 for discharging in the forward direction to the aperture drive coil 3 is provided in one of the capacitors C1 via a switch element 12 consisting of a switching transistor. The base 12a of the switch element 12 is connected to the positive voltage side 1 of the power supply circuit, and when the power supply is cut off and the voltage of the base 12a decreases, the switch element 12 is turned on, and remains in a non-conducting state during normal power supply. has been done. The other capacitor C2 has a similar discharge circuit 13 connected to a switch element 14.
is connected to the base 7a of the switch element 7 through the switch element 7, and when the voltage at the base 14a of the switch element 14 decreases when the power supply is cut off, the element 14
ON, and set the charging voltage of capacitor C2 to base 7.
It is configured to supply power to a and prevent the switch element 7 from turning on.

Therefore, when power is supplied to the power supply circuit, the capacitors C1 and C2 are charged, while the switch elements 12 and 14 of the discharge circuits 11 and 13 are in a non-conducting state, so that the aperture The automatic aperture control of the drive coil 3 is performed in the same way as in the case of FIG. The discharge circuits 11 and 13 of C1 and C2 become conductive, but among the switch elements 5 and 7 which turn on as the voltage decreases, the base 7a of the switch element 7 maintains the OFF state due to the discharge voltage of the capacitor C2. , discharge circuit 11 of capacitor C1
conducts in the forward direction (direction of arrow A) of the diaphragm drive coil 3, and the diaphragm is driven in the closing direction to the closed state.

As described above, according to the automatic aperture control device for a television camera according to the present invention, the aperture drive coil 3 for controlling the amount of light is connected to the power supply circuit consisting of the positive voltage side 1 and the negative voltage side 2 of the coil 3. In this case, the power supply in the forward direction A drives the diaphragm in the closing direction, and the power supply in the reverse direction drives the diaphragm in the opening direction, so that the amount of light received is kept within the standard range. In the automatic aperture control device for a television camera, for example, when the light reception signal output increases, the output of the output terminal 8a of the inverting amplifier circuit 8 of the light reception signal output 10 is changed to the forward direction A positive voltage side of the aperture drive coil 3. Switch element 4
At the same time, the same output is supplied to the base 4a of the forward direction A negative voltage side as the output terminal 9a of the inverting amplification output circuit 9 on the opposite side.
Since the switch elements 4 and 5 operate simultaneously, the aperture drive coil 3 is supplied with power in the forward direction A, and the aperture is immediately driven in the closing direction. Similarly, when the signal output decreases, the switch element 6 on the reverse positive voltage side and the switch element 7 on the reverse negative voltage side of the aperture drive coil 3 operate simultaneously, supplying power to the aperture drive coil 3 in the reverse direction. The diaphragm is immediately driven in the opening direction, which has the effect of supplying power in the forward direction to the diaphragm drive coil 3, that is, quickly opening and closing the diaphragm. 7, 5, 6 base 4a, 7a, 5
Each diode D1, D provided between a and 6a
2, D3, and D4 reduce the voltage difference between the base and emitter of the transistors constituting each switch element.
The switch elements 4, 5, 6, and 7 have the effect of sensitively responding to increases and decreases in the output of the switch element 4, thereby eliminating the dead range of the switch element and enabling highly accurate control. An essential component of the invention is that in order to drive the diaphragm in the closing direction when the power is cut off, a transistor whose base 12a is connected to the positive voltage side 1 of the power supply circuit and which conducts when the voltage drops is driven in the forward direction. The capacitor C
1. When a discharging circuit consisting of a switch element 12, a drive coil 3, a switch element 5, and a negative voltage side 2 is provided, and an attempt is made to supply power in the forward direction A to the drive coil 3, the reverse direction negative voltage side of the drive coil 3 is The connected switch element 7 becomes conductive at the same time as the switch element 5 when the power is cut off. However, in the present invention, a capacitor C2 is provided in the same manner as the capacitor C1, and the base 14
A is connected to the base 7a of the switch element 7 through a switch element 14 having a transistor connected in series in the forward direction which is connected to the positive voltage side 1 of the power supply circuit and becomes conductive when the voltage of the base 14a decreases, and the capacitor C2 is connected to the base 7a of the switch element 7. By providing a discharge circuit consisting of the switch element 14, the base 7a, and the negative voltage side 2, the capacitor C2 is discharged simultaneously with the discharge of the capacitor C1, and charging power is supplied to the base 7a of the switch element 7. This prevents conduction of the switch element 7, ensures that the capacitor C1 supplies power in the forward direction A to the drive coil 3, and operates the diaphragm in the closing direction. This has the effect of automatically bringing the system into a closed state.

Therefore, according to the present invention, not only is it possible to perform excellent aperture control during normal shooting, but even if the power is turned off and the TV camera is left unattended after shooting, the aperture closes immediately, reducing the amount of incident light to the minimum or Since it is maintained in a shut-off state, it has the effect of preventing accidents such as burnout of the image pickup tube, and is of great practical benefit.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the main parts of an embodiment of an automatic aperture device for a television camera to which the present invention is applied;
The figure is a circuit diagram showing a main part of an embodiment of the device of the present invention. 3... Aperture drive coil, 4, 5, 6, 7... Switch element, 12, 14... Switch element, 1
1, 13...discharge circuit, C1, C2...capacitor.

Claims (1)

[Scope of utility model registration request] The diaphragm driving coil 3 for light amount control is driven in the closing direction by supplying power in the forward direction A in a power supply circuit consisting of a positive voltage side 1 and a negative voltage side 2 of the coil 3. In an automatic aperture control device for a television camera, which is connected so that the aperture is driven in the opening direction by power supply in the opposite direction, and the amount of light received is kept within a reference range, an inverting amplification circuit for a light reception signal output 10 is used. The output terminal 8a of 8 is connected to the base 4a of a switch element 4 consisting of a transistor whose collector is connected to the positive voltage side 1 and whose emitter is connected to the forward positive voltage side of the drive coil 3 via a reverse diode D1. At the same time, the base 7a of a switch element 7 consisting of a transistor whose collector is connected to the negative voltage side 2 and whose emitter is connected to the reverse negative voltage side of the drive coil 3 is connected via a forward diode D2, while the inverting amplification circuit 8
An output terminal 9a of an inverting amplifier circuit 9 which inverts and amplifies the inverted amplified signal of the output terminal 8a of the inverting amplifier circuit 9 and outputs an inverted amplified output.
is connected via a reverse diode D3 to the base 6a of a switch element 6 consisting of a transistor whose collector is connected to the positive voltage side 1 and whose emitter is connected to the reverse positive voltage side of the drive coil 3, and the collector is connected to the negative voltage side. A switch element 5 consisting of a transistor connected to the voltage side 2 and having its emitter connected to the forward negative voltage side of the drive coil 3
A capacitor C2 is connected to the base 5a of the inverting amplifier circuit 8 through a forward diode D4, and a capacitor C2 having a charging circuit between the power supply circuits 1 and 2 is connected to the inverting amplifier circuit 8 side, and a capacitor C1 is connected to the inverting amplifier circuit 9 side. A switch element 14 is connected to the one capacitor C2 in parallel and has a transistor connected in series in the forward direction, the base 14a of which is connected to the positive voltage side 1 of the power supply circuit and becomes conductive when the voltage of the base 14a drops. the capacitor C2 connected to the base 7a of the switch element 7;
A discharge circuit consisting of a switch element 14, a base 7a, and a negative voltage side 2 is provided, and the other capacitor C1 has a transistor whose base 12a is connected to the positive voltage side 1 of the power supply circuit and which conducts when the voltage drops. The capacitor C is connected to the positive voltage side in the forward direction A of the aperture drive coil 3 through a switch element 12 arranged in series.
1. An automatic aperture control device for a television camera, which is provided with a discharge circuit consisting of a switch element 12, a drive coil 3, a switch element 5, and a negative voltage side 2.