JPH0334731Y2 - - 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 is 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 further inverts and amplifies the output voltage of the inverting amplifier circuit 8 and connects the output terminal 9a between the diodes D3 and D4.
This is an inverting amplifier circuit that gives an opposite output voltage from the output terminal 9a.
The relationship is such that the voltage 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 accordingly, when the voltage at the base 4a of the switch element 4 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, supplying power to the diaphragm drive coil 3 in the forward direction (direction of arrow A), driving the diaphragm in the closing direction and reducing the amount of light received by the television camera. On the other hand, when the amount of light received decreases and the voltage at the output terminal 8a drops, the voltage at the output terminal 9a increases, and accordingly, when the voltage at the base 7a of the switch element 7 falls below a predetermined range and turns ON, at the same time Switch element 6
turns ON when the voltage of the base 6a exceeds the specified range.
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 receives an appropriate amount of light within the reference light amount range.

As shown in FIG. 2, in the automatic diaphragm control device according to the present invention, a capacitor C is connected through a diode D5 and a resistor R5 from a positive voltage side 1 to a zero voltage side 2 in a power supply circuit. The capacitor C is connected in series to form a charging circuit, while the excitation coil 11a of the electromagnetic relay 11 is connected to the capacitor C in parallel. Further, the capacitor C is connected to a discharge circuit 12 for discharging the charged charge via a switch element 11b of the electromagnetic relay 11.
are connected in series in the forward direction (direction of arrow A) of the aperture drive coil 3.

Therefore, when power is supplied to the power supply circuit, the capacitor C is charged, while the switch element 11b of the discharge circuit 12 is open and in a non-conducting state, so that automatic aperture control of the aperture drive coil 3 is performed. is performed in the same manner as in FIG. When the power supply to the power supply circuit is cut off, the electromagnetic relay 11 is activated by the transient current flowing through the excitation coil 11a, and the switch element 11b becomes conductive. 12 is closed, the charged current flows in the forward direction (arrow A direction) 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 to the diaphragm drive coil 3 in the forward and reverse directions, that is, quickly opening and closing the diaphragm. 7, 5, 6 base 4a, 7a,
Each diode D1, D provided between 5a 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 A, thereby eliminating the dead range of the switch element and enabling highly accurate control. An essential component of the invention is that when the power is cut off, when attempting to supply power in the forward direction A to the drive coil 3 in order to drive the diaphragm in the closing direction, the forward negative voltage of the drive coil 3 Even if you try to take advantage of the fact that the switch element 5 on the side closes at the same time as the power is cut off, it is difficult to use because the switch element 7 connected to the negative voltage side in the reverse direction becomes conductive at the same time as the switch element 5 when the power is cut off. Although there is a problem, the present invention provides a chargeable capacitor C between the positive voltage side 1 and negative voltage side 2 of the power supply circuit via the diode D5, and the excitation coil 11a of the electromagnetic relay 11. Said capacitor C
The capacitor C is connected to the aperture via a switch element 11b on both sides of the aperture drive coil 3, which is simultaneously turned on by the excitation coil 11a of the electromagnetic relay 11, which is excited when the power supply is cut off. Since the configuration includes a discharge circuit connected in series in the forward direction A of the drive coil 3, the switch element 11b becomes conductive at the same time as the power is cut off, discharging the capacitor C, and discharging the respective switch elements 4, 5, 6, and 7, it is possible to reliably achieve power supply in the forward direction A to the drive coil 3 by the capacitor C and operate the diaphragm in the closing direction. It has the effect of being able to be in 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 the drawing]

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, 11... Electromagnetic relay, C... 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
The electromagnetic relay 11 excitation coils 11a are provided in parallel to the capacitor C, and the capacitor C is provided with the electromagnetic relay 1 that is excited when the power supply is cut off.
The television is characterized in that a discharge circuit is provided in which switch elements 11b which are simultaneously turned on by one excitation coil 11a are connected in series in the forward direction A of the aperture drive coil 3 via both sides of the aperture drive coil 3. Automatic aperture control device for cameras.