JPS6143340Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an aperture adjustment device for a television camera, and is intended to improve the response during manual adjustment, especially when the aperture is adjusted both manually and automatically. be.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an aperture adjustment mechanism. In the figure, reference numeral 1 denotes a diaphragm provided on the entrance side of a lens system of a television camera, and the aperture of this diaphragm 1 is varied by rotation of a drive coil 2. The drive coil 2 is rotatably disposed within the gap between the permanent magnets 3, the magnetic flux within the gap is in the direction of the arrow, and when a drive current is passed through the drive coil 2 in the direction of the arrow, the drive coil 2 rotates in the direction of the arrow. This rotational force and rotation angle are proportional to the drive current. Braking coil 4 that rotates together with drive coil 2
will be provided. When the braking coil 4 rotates, an electromotive force is generated by cutting the magnetic flux within the air gap. This electromotive force is supplied to an external circuit as a braking signal, and braking is performed on the variable operation of the diaphragm 1.

In addition, when adjusting the aperture 1 by electromagnetic force,
The coil may be fixed and the permanent magnet may be movable. Further, the above-mentioned adjustment of the diaphragm 1 is performed electrically based on the level of the drive signal. Separately, manually turn the rotary plate to mechanically aperture 1.
You may also adjust it.

As shown in FIG. 2, the output of the comparison amplifier 5 is supplied to the drive coil 2 as a drive signal. The comparison amplifier 5 is constituted by an operational amplifier, and its non-inverting input terminal is supplied with the reference voltage selected by the changeover switch 6, and its inverting input terminal is supplied with the comparison voltage selected by the changeover switch 7. Supplied via resistor 8. 9 is a feedback resistor of the comparison amplifier 5. The electromotive force generated in the braking coil 4 is supplied to the inverting input terminal of the comparison amplifier 5 as a braking signal (current) via resistors 10a and 10b. A switch 11 that is turned off during manual adjustment is provided in parallel with the resistor 10b. The braking signal is
The higher the rotational angular velocity of the drive coil 2, the higher the level, and hunting in the diaphragm 1 due to a sharp change in the level of the drive signal is prevented. If switch 11 is off,
Since both resistors 10a and 10b are inserted, the gain of the braking signal is lowered compared to when they are on.

The changeover switch 6 has a terminal 6A that is connected during automatic adjustment and provides a predetermined voltage to the comparison amplifier 5, and a terminal that is selected during manual adjustment and provides a variable voltage generated in the slider of the variable resistor 12 to the comparison amplifier 5. 6
It has M. The variable resistor 12 is provided, for example, at a location apart from the camera body, so that the aperture 1 can be adjusted by remote control.

The changeover switch 7 is connected to a terminal 7A that is connected during automatic adjustment and is supplied with the average level of the output signal of the television camera 13, and is connected during manual adjustment and is supplied with a position detection signal via the amplifier 18 of the position detection element 17. It has a terminal 7M. The output signal of the television camera 13 is supplied to a processor (not shown) via a preamplifier 14 and a clamp circuit 15, and is also supplied to a rectifier circuit 16.
A is supplied. The position detection element 17 has a magnetic or photoelectric configuration that generates a position detection signal of a level corresponding to the aperture of the aperture 1. Furthermore, the switches 6, 7, and 11 are configured to interlock with each other.

In the configuration of the embodiment of the present invention described above, during manual adjustment, the switches 6, 7, and 11 are in the state shown in FIG. 2. A predetermined DC voltage is supplied to the comparison amplifier 5 from the slider of the variable resistor 12 via the changeover switch 6. On the other hand, amplifier 18
A position detection signal from the position detection element 17 is supplied to the comparison amplifier 5 via the changeover switch 7 and the input resistor 8, and a drive signal with a polarity and level corresponding to the difference between the two input voltages is sent to the drive coil 2. is supplied to This causes the drive coil 2 to rotate and the position detection signal to change as well. Comparison amplifier 2 to 5
When the levels of the two inputs become equal, the drive signal becomes zero, and the aperture is adjusted according to the position of the slider of the variable resistor 12. During this manual adjustment, the switch 11 is turned off, so the gain of the braking signal is lowered.

During automatic adjustment, a fixed reference voltage is supplied to the comparison amplifier 5 via the changeover switch 6. A drive signal having a polarity and level corresponding to the difference between this reference voltage and the output voltage of the rectifier circuit 16 via the switch 7 is supplied to the drive coil 2. Feedback control is performed so that this difference becomes zero.
During this automatic adjustment, the switch 11 is on, so the gain of the braking signal is larger than during manual adjustment.

As understood from the description of one embodiment above,
According to the present invention, since the gain of the braking signal is switched between manual adjustment and automatic adjustment, when braking becomes excessive during manual adjustment and the variable resistor 12 is moved, the response to the change in the aperture 1 It is possible to prevent the speed from slowing down and improve the operational feel.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the general structure of an aperture adjustment mechanism in an embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention. 1 is the aperture, 2 is the drive coil, 4 is the brake coil,
5 is a comparison amplifier, 6, 7, 11 are switches, 13
is a television camera, and 17 is a position detection element.

Claims (1)

[Scope of utility model registration request] A diaphragm that is varied by a drive coil that is electromagnetically displaced in response to a drive signal, a braking coil that moves together with the drive coil and generates the electromotive force as a braking signal, and a position that detects the position of the diaphragm. a detection means, a level detection circuit for detecting the level of the output signal of the television camera; during manual adjustment, the drive signal is formed based on the output of the position detection means; during automatic adjustment, the drive signal is formed based on the output of the level detection circuit; A comparison means for forming the drive signal based on the drive signal, a means for adding the braking signal to the drive signal, and a means for making the braking by the braking signal smaller during the manual adjustment than during the automatic adjustment. TV camera aperture adjustment device.