JP2925418B2 - Light control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, this type of apparatus has a light amount control member (aperture blade) 25, 26 as shown in FIGS.
To control the light amount to approach the target value.
More specifically, the motor control signal V _C output from the arithmetic circuit 5 for calculating and amplifying the difference between the light amount control signal V _S and the speed control signal V _E energizes the drive coil 3 in the motor unit 1 to rotate the rotor. The magnet 2 is driven to rotate. The rotation of the rotor magnet 2 causes the aperture blades 25 and 26 to
4 drive. In addition, a braking coil 4 for detecting the rotation speed of the rotor magnet 2 is provided, and a speed signal from the braking coil 4 is negatively fed back to the arithmetic circuit 5 as a speed control signal via an amplifier circuit 6. The motor control signal V _C 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 generates a reference potential V _DD such as a control signal, and outputs the reference potential to one end of the braking coil 4, the amplifier circuit 6, and the arithmetic circuit 5.

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

The driving force of the rotor magnet 2 and the spring force of the spring 28 are transmitted via the driving arm 24 to the light quantity control members 25 and 2.
6 to control the amount of light passing through the openings 23a and 27b.

[0005] The motor control signal V _C is the drive coil 3
The rotor magnet 2 is driven (one-way drive) only in the opening direction (direction in which the opening area increases) via the drive arm 24, and is closed in the closing direction (the opening area decreases). In this case, 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]

In, however the prior art [0005] The control member 25, 26 to be driven according to the motor control signal V _C, a torque sufficient to overcome the spring force of the spring 28 is needed at all times. 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, and the size and power consumption of the motor unit need to be increased. There was a disadvantage that it could not be avoided.

Further, depending on the system, there is a case where it is desired to cut off or open the light amount after the power is turned off, and the light amount has to be cut off using a strong spring which is a factor of enlargement.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a light quantity control device for controlling a passing light quantity by operating a light quantity control member by energizing a drive coil to rotate a rotor,
The drive coil is bidirectionally energized based on the light intensity control signal,
A first drive circuit for rotating the rotor in forward and reverse directions;
A second direction in which the drive coil is energized in one direction for a predetermined time after the power is turned off to rotate the rotor toward a predetermined position;
And the holding means for holding the rotor at the predetermined position even after the predetermined time can eliminate the need for a strong return spring, which was conventionally required, and enable low-voltage driving. .

[0009]

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

FIG. 1 shows a configuration of a light quantity control device according to the present embodiment. In FIG. Reference numeral 12 denotes a rotor magnet that drives the light amount control members (aperture blades) 35 and 36 in FIG. Reference numeral 13 denotes a drive coil for rotating the rotor magnet 12 based on a potential difference between a motor control signal V _C output from the arithmetic circuit 15 and a motor control signal −V _C output from the inverting amplifier circuit. Reference numeral 14 denotes a braking coil for detecting the rotation speed of the rotor magnet 12. 15 amplifies calculates the difference between the light amount control signal V _S and the speed control signal V _E,
Arithmetic circuit for outputting a motor control signal V _C. The light amount control signal V _S is detected by a sensor such as a CCD to detect the light flux passing through the openings of the light amount control members 35 and 36, and is taken in as photometric information. And so on. 16 amplifies the output of said braking coil 14, an amplifier circuit for outputting to the operation circuit 15 as the speed control signal V _E, 1
7 inverts the motor control signal V _C output from the arithmetic circuit 15 with respect to the midpoint potential V _DD , and supplies a motor control signal −V _C having the same absolute value with a reverse polarity to one end of the drive coil 13. An inverting amplifier circuit for outputting; a reference voltage generating circuit for generating a midpoint potential V _DD of a power supply voltage serving as a reference potential; 15 is a voltage holding circuit that outputs the voltage to the circuit 15

In FIG. 2, reference numeral 31 denotes a PCB substrate on which circuit elements are mounted. Numeral 32 constitutes a magnetic circuit together with the rotor magnet 12, which causes an imbalance in the magnetic resistance due to a step in the radial direction and a gap at the joint, and causes the rotor magnet 1
Clinch yoke 2 with magnetic stability point (stable stop point). Reference numeral 33 denotes an aperture base plate having an opening 33a and supporting each component. Numeral 34 denotes a light amount control member (aperture blade) 35 which controls the driving force of the rotor magnet 32 by swinging the driving pin 34a.
A drive arm transmitting to 36; The drive pin 34a is inserted into the slots 35b and 36b. 35 is a light amount control member having an opening 35a. 36 is a light amount control member having an opening 36a. An aperture 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-described configuration, the light amount control signal V _S and the speed control signal VE output from the amplifier 16 become the motor control signal V _C in the arithmetic circuit 15. The motor control signal V _C is inverted with respect to the midpoint potential V _DD by the inverting amplifier circuit 17 to obtain a motor control signal −V _C.

The drive coil 13 applied with the potential difference between the motor control signals V _C and −V _C controls the rotation of the rotor magnet 12 in accordance with the motor control voltage difference.
Drive 36 to control the amount of light passing through openings 37a and 33a to approach the target amount of light. Further, the rotation speed of the rotor magnet 12 is detected by the braking coil 14, and the amplification circuit 16 performs negative feedback to the arithmetic circuit 15 as the speed control signal VE, thereby improving the light amount controllability such as hunting (turbulence).

The potential difference between the motor control signal V _C and the motor control signal -V _C is applied to the driving coil 13, the maximum voltage width becomes substantially circuit power supply voltage is comparable to the conventional example. When the polarity of the motor control signal V _C output from the arithmetic circuit 15 is inverted, the polarity of the motor control signal −V _C is also inverted, so that the motor control signal V _C and the motor control signal applied to the drive coil 13 are inverted. polarity of the potential difference between -V _C is inverted. Thus, the rotor magnet 12 by the polarity of the motor control signal V _C output from the arithmetic circuit 15 performs normal rotation reversed. Also in this case, the maximum voltage width is almost equal to the power supply voltage. Therefore, normal rotation and reverse rotation can be performed without a spring while maintaining the same motor control voltage with the same circuit power supply as the conventional example. In addition, since the polarity of the potential difference applied to the drive coil 13 is used, it can be realized without deterioration in controllability.

When the power is off, the output of the voltage holding circuit 19 is higher than the output of the reference voltage generating circuit 18 for a certain period of time.
Accordingly, the output of the inverting amplifier circuit 17 becomes a high voltage, and the drive coil 13 is energized in one direction (closing direction).
Therefore, the rotor magnet 12 drives the light amount member in the closing direction (the direction in which the opening area is reduced, that is, the light amount is reduced).

When the rotor magnet 12 is rotated in the closing direction, a clinch yoke having a magnetically stable point is positioned with respect to the rotor magnet 12 at the closing position of the light amount control members 35 and 36 (the driving pin 34a of the driving arm 34 is connected to the circular groove 37b). In a state where it is locked at one end of the
The light quantity can be cut off even after the FF. Since the suction 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-described embodiment, the first drive circuit that bidirectionally energizes the drive coil based on the light quantity control signal and rotates the rotor in the forward and reverse directions includes the arithmetic circuit 15, the inverting amplifier circuit 17, and the drive coil. 13 and power off
A second drive circuit that supplies current to the drive coil in one direction for a predetermined time from the predetermined time and rotates the rotor toward a predetermined position includes a power supply holding circuit 19, an arithmetic circuit 15, and a drive coil 13.
Consists of And, by using the magnetic action of the clinch yoke and the rotor as a holding means for holding the rotor at the predetermined position even after the predetermined time, a spring for driving the light amount control member in one direction can be eliminated. In addition, the motor unit can be reduced in size and weight and consume less power, and can be driven at a low voltage corresponding to battery driving. In addition, it is possible to cut off the amount of light after turning off the power, which is a system requirement.

In the above-mentioned embodiment, the clinch yoke 3
Other methods use a spring that urges the light amount control member in the closing direction with a very weak spring force, and a permanent magnet that closes the rotor magnet and attracts and holds the rotor at the rotational position (the light amount control member is in a shielded state). This has the same effect.

[0019]

According to the present invention, it is possible to eliminate the need for a strong return spring, which has been required in the past, and to provide a light quantity control device capable of driving at a low voltage, realizing a small size, light weight and low power consumption. .

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a light quantity control device as an embodiment of the present invention.

FIG. 2 is an exploded perspective view 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 quantity control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Motor part 12 Rotor magnet 13 Drive coil 15 Operation circuit 16 Amplification circuit 17 Inverting amplification circuit 18 Reference voltage generation circuit 19 Power supply holding circuit 25/26 Light quantity control member 32 Clinch yoke

Claims (1)

(57) [Claims] 1. A light quantity control device for controlling a quantity of light passing through by actuating a light quantity control member by rotating a rotor by energizing a drive coil, bi-directionally energizing the drive coil based on a light quantity control signal,
A first drive circuit for rotating the rotor in the forward and reverse directions, and a second drive circuit for rotating the rotor toward a predetermined position by energizing the drive coil in one direction for a predetermined time from power-off.
And a holding means for holding the rotor at the predetermined position after the predetermined time.