JPH06258684A - Light quantity controller - Google Patents

Abstract

PURPOSE:To disuse a strong return spring required at the time of turning off a power source, to make the controller small in size and light in weight, and to drive it at a low voltage by providing a means for holding a rotor at a specified rotating position at the time of turning off the power source. CONSTITUTION:A driving coil 13 on which voltage is impressed by the potential difference of motor control voltage Vc and -Vc, controls to rotate a rotor magnet 12, thereby a light quantity control member is driven to control light quantity passing through an aperture part. The rotating speed of the rotor magnet 12 is detected by a control coil 14, and negatively fed back to a comparison arithmetic circuit 15 as a speed control signal V5 by an amplifier circuit 16, then the controllability of the light quantity such as hunting is improved. At the time of turning off the power source, the output of a voltage holding circuit 19 becomes higher than the output of a reference voltage generation circuit 18, and in that period, the output of the circuit 15 becomes constant voltage, so that the output of an invertible amplifier circuit 17 becomes high voltage, then a current is applied to the coil 13 in one direction. Therefore, the rotor magnet 12 drives the light quantity control member in a closing direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light quantity adjusting device mounted on an optical device such as a video camera.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 3 and 4, a device of this type has a light amount control member (aperture blade) 25, 26.
Is driven to control the light amount to approach the target value.
Specifically, the motor control signal Vc, which is the output of the arithmetic circuit 5 that compares the light amount control signal Ys and the speed control signal, energizes the drive coil 3 in the motor unit 1 to rotate the rotor magnet 2. The rotation of the rotor magnet 2 drives the diaphragm blades 25 and 26 via the drive arm 24. Further, it has a braking coil 4 for detecting the rotation speed of the rotor magnet 2, and the speed signal from the braking coil 4 is negatively fed back to the comparison operation circuit 5 as a speed control signal via an amplifier circuit 6. The motor control voltage Vc is applied to one end of the drive coil 3, and the ground level constant voltage is applied to the other end. Reference numeral 8 denotes a reference voltage generating circuit that creates a reference potential Vbb such as a control signal, and outputs the reference potential to one end of the braking coil 4, the amplifier circuit 6, and the comparison operation circuit 5.

In FIG. 4, 21 is a PCB substrate,
Reference numeral 22 is a yoke that is a magnetic material that forms a magnetic circuit together with the rotor magnet 2, 23 is an aperture base plate that has an opening 23a and supports each component, and 24 is a light amount control member 25 that controls the driving force of the rotor magnet 2 and the spring 28. A drive arm transmitting to 26, a light quantity control member 25 having an opening 25a,
Reference numeral 26 denotes a light amount control member having an opening 26a, 27 denotes an aperture case having an opening 27a for supporting the light amount control members 25, 26, and 28 denotes the light amount control members 25, 26 via the drive arm 24. It is a spring that is driven in the direction (throttle direction).

The drive force of the rotor magnet 2 and the spring force of the spring 28 are transmitted via the drive arm 24 to the light quantity control member 25.2.
6 is controlled to control the amount of light passing through the openings 23a and 27b.

The motor control voltage Vc is applied to the drive coil 3
The rotor magnet 2 is driven only in the opening direction (direction in which the opening area increases) via the drive arm 24 (unidirectional driving), and in the closing direction (opening area decreases). The light amount control members 25 and 26 are driven in the closing direction only by the spring force after the power is turned off, and the light amount cutoff state is maintained.

[0006]

However, in the above-mentioned conventional example, in order to drive the control members 25 and 26 in accordance with the motor control voltage Vc, a torque sufficient to overcome the spring force of the spring 28 is always required. Moreover, the spring force has sufficient power to drive the control members 25 and 26. Therefore, a very large torque is required for the motor, so that the motor portion becomes large and the power consumption becomes large. It had the drawback of being unavoidable.

Further, depending on the system, there is a case where it is desired to cut off or open the light quantity after the power is turned off, and it has been necessary to cut off the light quantity by using a strong spring which is a factor of increasing the size.

[0008]

According to a first aspect of the present invention, a light amount control device of the present invention controls a light amount control member by rotating a rotor as a drive source forward and backward by magnetic action based on a light amount control signal to operate a light amount control member. Rotor drive circuit and power supply OF
By providing a second rotor drive circuit that drives the rotor in the direction of the specific rotation position for a predetermined time by magnetic action at the time of F, and holding means that holds the rotor at the specific rotation position even when the power is off. The strong return spring, which was conventionally required, can be eliminated, and low voltage driving can be enabled.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of the light quantity control device of this embodiment. In FIG. 1, 11 is a motor section. Reference numeral 12 is a rotor magnet that drives the light amount control members (aperture blades) 35 and 36 in FIG. Reference numeral 13 is a drive coil for rotating the rotor magnet 12 by the voltage difference between the motor control voltage Vc output from the comparison calculation circuit 15 and the motor control voltage −Vc output from the inverting amplifier circuit. 14 is a braking coil that detects the rotational speed of the rotor magnet 12. Reference numeral 15 is a comparison calculation circuit for performing a comparison calculation of the light amount control signal Vs and the speed control signal V _E and outputting a motor control voltage Vc. The light amount control signal Vs is detected by a sensor such as a CCD for the light flux that has passed through the openings of the light amount control members 35 and 36 and is taken in as photometric information, and a microcomputer or the like is used to correct the difference from a preset value. It was decided by. Reference numeral 16 is an amplifier circuit for amplifying the output of the braking coil 14 and outputting it to the comparison operation circuit 15 as a speed control signal V _E. Reference numeral 17 is a motor control voltage Vc output from the comparison operation circuit 15 for a midpoint potential V _DD. An inverting amplifier circuit that inverts the control voltage -Vc having the same absolute value with the opposite polarity to the drive coil 13, and a reference voltage generation circuit 18 that creates a midpoint potential _VDD of the power supply voltage that becomes the reference potential. , 19 is the power source O
It is a voltage holding circuit which holds the potential at the time of FF by the resistors R ₁ and R ₂ and the capacitor C for a predetermined time and outputs it to the comparison operation circuit 15.

In FIG. 2, reference numeral 31 is a PCB board on which circuit elements are mounted. Reference numeral 32 forms a magnetic circuit together with the rotor magnet 12, and causes a magnetic resistance imbalance due to a radial step and a gap between the joints.
A clinch yoke with a magnetic stable point (stable stop point) on 2. A diaphragm base plate 33 has an opening 33a and supports each component. Reference numeral 34 is a light amount control member (aperture blade) for driving force of the rotor magnet 32 by swinging the drive pin 34a.
-Drive arm transmitting to 36. The drive pin 24a is inserted into the elongated holes 35b and 36b. Reference numeral 35 is a light amount control member having an opening 35a. Reference numeral 36 is a light amount control member having an opening 36a. A diaphragm case 37 has an opening 37a and an arc groove 37b for limiting the swing range of the drive arm 34, and supports the light amount control members 35 and 36.

In this embodiment having the above construction, the light amount control signal Vs and the speed control signal V _E which is the output of the amplifier circuit 16 are used.
Becomes the motor control voltage Vc in the comparison calculation circuit 15. The motor control voltage Vc is inverted by the inverting amplifier circuit 17 with respect to the midpoint potential V _DD to obtain the control voltage −Vc.

The drive coil 13 applied with a potential difference between the motor control voltage Vc and -Vc controls the rotation of the rotor magnet 12 in accordance with the motor control voltage difference, and the light amount control member 3 is provided.
5.36 is driven to control the amount of light passing through the openings 37a and 33a to bring it closer to the target amount of light. Further, the rotation speed of the rotor magnet 12 is detected by the control coil 14, and the amplification circuit 16 feeds back negatively as the speed control signal V _E to the comparison operation circuit 15 to improve the light quantity controllability such as hunting.

A voltage difference between the motor control voltage Vc and the control voltage −Vc is applied to the drive coil 13, and the maximum voltage width thereof is almost the circuit power supply voltage, which is equivalent to the case of the conventional example. In the case of normal rotation and reverse rotation, it is only necessary to reverse the polarities of the motor control voltages Vc and -Vc, and in this case as well, the maximum voltage width is almost the power supply voltage. That is, it is possible to perform normal rotation / reverse rotation without a spring while maintaining the same motor control voltage with the same circuit power supply as the conventional example. Moreover, since the control voltage itself applied to the drive coil 13 is used, it can be realized without deterioration of controllability.

Further, when the power is turned off, the output of the voltage holding circuit 19 becomes higher than the output of the reference voltage generating circuit 18 for a certain period of time, so that the output of the comparison operation circuit 15 becomes a constant voltage during the period, and the output of the inverting amplifier circuit 17 is accordingly accompanied. The output becomes a high voltage, and the drive coil 13 is energized in one direction (closing direction). Therefore, the rotor magnet 12 drives the light quantity member in the closing direction (the opening area, that is, the direction in which the light quantity decreases).

When the rotor magnet 12 is rotated in the closing direction, a clinch yoke having a magnetically stable point is used to close the light quantity control members 35 and 36 relative to the rotor magnet 12 (the drive pin 34a of the drive arm 34 has an arc groove 37b). Power is applied by holding power in the state of being locked at one end).
The amount of light can be blocked even after FF. Since the attraction force may be weak enough to hold the light amount control members 35 and 36, it is possible to prevent a large load on the motor unit.

In the above embodiment, the means for generating the speed control signal, the means for adding the light amount control signal and the speed control signal to generate the motor control voltage, and the motor control voltage having the same absolute polarity but the same absolute value are used. A means to generate a control voltage with a value, a means to cut off the amount of light when the power is off, and a power off
The spring for driving the light quantity control member in one direction can be eliminated by providing a means for holding the light quantity cut-off state later,
It is possible to reduce the size and weight of the motor unit, reduce power consumption, and drive at a low voltage corresponding to battery drive, and also to realize the light amount cutoff after the power is turned off, which is required by the system.

In the above embodiment, the clinch yoke 3 is used as a means for maintaining the light quantity cutoff state after the power is turned off.
2 was used, but as another means, a spring that urges the light amount control member in the closing direction with an extremely weak spring force, or a permanent magnet that attracts and holds the rotor magnet at the closed rotational position (the light amount control member is in a shielded state) is used. However, there are similar effects.

[0019]

The present invention can provide a light quantity control device which can eliminate a strong return spring which has been conventionally required, can be driven at a low voltage, and can be reduced in size, weight and power consumption. .

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a light quantity control device as an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a light quantity control device as an embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional light amount control device.

FIG. 4 is an exploded perspective view of a conventional light amount control device.

[Explanation of symbols]

 11 Motor Section 12 Rotor Magnet 13 Drive Coil 15 Comparison Arithmetic Circuit 16 Amplifying Circuit 17 Inverting Amplifier Circuit 18 Reference Voltage Generating Circuit 19 Power Supply Holding Circuit 25/26 Light Quantity Controlling Member 32 Clinch Yoke

Claims (2)

[Claims] 1. A light amount control device for controlling a passing light amount by operating a light amount control member by rotating a rotor as a driving source, wherein a first rotor drive for rotating the rotor by magnetic action based on a light amount control signal. A circuit, a second rotor drive circuit for magnetically driving the rotor in the direction of the specific rotation position for a predetermined time when the power is off, and holding means for holding the rotor at the specific rotation position even when the power is off. And a light quantity control means. 2. The magnet rotor is magnetized to have n poles (n is a positive number of 2 or more) and has a rotation angle range of θ = 360 °.
The light quantity control device according to claim 1, wherein the angle is set to be equal to or less than / n.