JPH05292391A - Driving circuit for automatic iris lens - Google Patents

Abstract

PURPOSE:To use a DC driven automatic iris lens under a high illuminance without providing a mechanical stopper by suppressing hunting for the high illuminance. CONSTITUTION:The output signal of a CCD 2 has the noise eliminated by an S/H circuit 3 and is processed by a process 4 to output a video signal 5. The output of the S/H circuit is detected by a detector 6 and is subtracted from a set voltage E2 by a subtractor 7, and this output voltage E3 is applied to a coil L1 of an automatic iris lens 1 to drive and open/close an iris. The detection output of the detector 6 is inputted to comparators 8 and 9, and if it is higher than a set voltage E4 or lower than a set voltage E5, comparators output signals respectively, and OR is operated in an AND operating circuit 10 after integration, and the output is integrated by an integrator 11 and is applied to the base electrode of a transistor 12. The driving voltage E3 from the subtractor 7 is so limited that it is not reduced to the emitter voltage of the transistor or lower, and the drop of the voltage applied to the coil L1 is suppressed, and a stop is controlled to prevent the occurrence of hunting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for an auto iris lens, and more particularly to a drive circuit for suppressing hunting under high illuminance.

[0002]

2. Description of the Related Art In an auto iris lens that opens and closes a diaphragm with a DC voltage and has a structure in which the diaphragm is completely closed,
There is something that causes hunting at high illuminance. For this reason,
It was necessary to provide a mechanical stopper to prevent the aperture from completely closing when the illuminance exceeds a set value, or to set a restriction such as not using it under high illuminance conditions.

[0003]

In view of the above, the present invention limits the drive voltage of the auto iris lens so that it does not fall below a required value when hunting occurs during use under high illuminance. Suppress hunting,
It is to enable the use of a DC drive type auto iris lens even under high illumination conditions.

[0004]

In order to solve the above-mentioned problems, the present invention provides an auto iris lens for detecting a signal from an image pickup device and driving a diaphragm by a drive voltage based on the detected output. A first comparator for comparing with a first set level, a first integrating circuit for integrating an output of the first comparator, a second comparator for comparing the detected output with a second set level, and a second comparator A second integrator circuit for integrating the output of the above, a logical product arithmetic circuit for performing a logical product operation of the integrated value of the first integrator circuit and the integrated value of the second integrator circuit, and an integrator for integrating the output of the logical product arithmetic circuit. A limiter circuit for limiting the drive voltage of the auto iris lens based on the output from the integrator is provided.

[0005]

With the above construction, in the drive circuit of the auto iris lens according to the present invention, the detection output of the signal from the image pickup device such as CCD (charge coupled device) is inputted to the two comparators. One of the comparators compares the input signal with the first set potential, outputs a signal when it is above the set potential, and the other comparator compares the input signal with the second set potential (potential lower than the first set potential). , A signal is output when the potential is equal to or lower than the set potential, the outputs of the comparators are respectively integrated appropriately, and the two integrated values are subjected to a logical product operation by a logical product operation circuit. The output from the AND operation circuit is integrated to limit the drive voltage of the auto iris lens so that it does not drop below this integrated value (voltage).

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive circuit for an auto iris lens according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of essential parts of an embodiment of a drive circuit for an auto iris lens according to the present invention. In the figure, reference numeral 1 is an auto iris lens, which opens and closes an aperture by a DC voltage applied to a coil L1. The coil L2 generates a counter electromotive force by the magnetic field generated in the coil L1, and feeds back this voltage to the drive circuit of the coil L1 via the resistor R4. 2 is C
An image sensor such as a CD. 3 is sample hold (S /
The H) circuit removes noise from the signal from the CCD 2.
A process circuit 4 processes the signal from the S / H circuit 3 to generate a desired video signal 5 for output. A detector 6 detects a signal from the S / H circuit 3. Reference numeral 7 is a subtractor (operational amplifier), which inputs the output voltage E1 of the detector 6 integrated by the resistor R1 and the capacitor C1 to the “−” terminal and divides it by the variable resistor R2 from the power supply voltage Vc Input E2 to the “+” terminal and subtract voltage E1 from voltage E2 to obtain voltage
E3 is output and applied to the coil L1 via the resistor R3.

Reference numeral 8 is a comparator which inputs the output voltage E1 of the detector 6 to the "+" terminal, divides the power supply voltage Vc by the variable resistor R5 and compares it with the set voltage E4 applied to the "-" terminal. , Voltage E4
Outputs a "high" signal when exceeding. 9 is a comparator,
Input the output voltage E1 of the detector 6 to the "-" terminal,
Vc is divided by the variable resistor R6 and compared with the set voltage E5 applied to the “+” terminal, and a “high” signal is output when the voltage drops below E5. Reference numeral 10 denotes a logical product calculation circuit, which inputs the output of the comparator 8 integrated by the resistor R7 and the capacitor C2 and the output of the comparator 9 integrated by the resistor R8 and the capacitor C3, and calculates the logical product. 11 is an integrator (operational amplifier)
Then, the output voltage E6 from the AND operation circuit 10 is integrated by the time constants of the resistor R9 and the capacitor C4 and input, and the voltage E7 is output. Reference numeral 12 is a transistor, and the emitter voltage is held at a voltage obtained by subtracting the base-emitter voltage from the voltage E7 applied to the base electrode, and the output voltage E3 of the subtractor 7 is held.
The voltage drop is limited so that it does not drop below the emitter voltage. S is a reset switch, auto iris lens 1
When the is replaced, etc., turn it on to reset it.

Next, the operation of the drive circuit for the auto iris lens according to the present invention will be described with reference to the voltage waveform diagram of FIG. Light from the captured image is passed through the auto iris lens 1 to C
The light enters the CD 2, is converted into an electric signal, and is output. This signal is input to the S / H circuit 3 to remove noise and the like, and the process circuit 4 performs processing such as gamma correction and outputs a video signal 5. On the other hand, the detector 6 detects the output of the S / H circuit 3, integrates the detected voltage E1 with the resistor R1 and the capacitor C1, and inputs it to the “−” terminal of the subtractor 7. To the “+” terminal of the subtractor 7, a voltage E2 obtained by dividing the power supply voltage Vc by the variable resistor R2 for adjusting the set voltage is applied.
The voltage E1 at the “–” terminal is subtracted from E2, and the voltage E3 is output. As shown in FIG. 3, this voltage E3 is a voltage (shading drive voltage) that decreases in accordance with an increase in the output of the detector 6 (increase in incident light), and this voltage is driven by the diaphragm of the auto iris lens 1 via the resistor R3. It is applied to the coil L1 for driving, and is driven in the direction to close the diaphragm according to the increase of the incident light. The coil L2 generates a counter electromotive force due to the magnetic field generated in the coil L1, feeds back this voltage to the “−” terminal of the subtractor 7 via the resistor R4, and abrupt fluctuation of the drive voltage applied to the coil L1. Work to limit.

The output voltage E1 of the detector 6 is also applied to the "+" terminal of the comparator 8 and the "-" terminal of the comparator 9. This output voltage E1 is, for example, the curve (E1) in FIG. 2 when hunting occurs in the diaphragm of the auto iris lens 1.
Increase or decrease like. The "-" terminal of the comparator 8 has a power supply voltage
Voltage E4 divided from Vc by variable resistor R5 for setting voltage adjustment
Is applied to the “+” terminal of the comparator 9, and the voltage divided by the variable resistor R6 for adjusting the set voltage from the power supply voltage Vc is applied.
E5 is being applied. In the comparator 8, the voltage E1 is the voltage E4.
When it becomes the above, the "high" signal B (shown by the vertical line) is output, and the comparator 9 outputs the "high" signal B (shown by the vertical line) when the voltage E1 becomes equal to or lower than the voltage E5. Output. The "high" signal B from the comparator 8 is integrated as a waveform C (shown by dots) with the time constant of the resistor R7 and the capacitor C2, and is input to one input terminal of the AND operation circuit 10, and The “high” signal B from the comparator 9 is integrated as a waveform D (indicated by dots) with the time constant of the resistor R8 and the capacitor C3, and is input to the other input terminal of the AND operation circuit 10. AND operation circuit
Reference numeral 10 logically ANDs the "high" signal B and the waveform C with the "high" signal B and the waveform D. That is, the voltage E6 is output while the two inputs are both “high”.

The integrator 11 inputs the voltage E6 via the resistor R9 and outputs a voltage E7 which is integrated by the time constants of the resistor R9 and the capacitor C4. This voltage E7 is applied to the base electrode of the transistor 12, whereby the emitter voltage of the transistor 12 is held at a voltage obtained by subtracting the base-emitter voltage from the voltage E7 applied to the base electrode, and the resistor R3 is applied. The subtractor 7 applied to the coil L1 via
The output voltage E3 is limited so as not to drop below the emitter voltage of the transistor 12. Therefore, when hunting occurs in the auto iris lens 1, the driving is stopped at the required diaphragm position and the hunting converges. When the auto iris lens 1 is replaced, the switch S is turned on to reset the drive circuit.

[0011]

As described above, according to the drive circuit of the auto iris lens according to the present invention, when hunting occurs in the diaphragm and the output signal level of the image sensor suddenly increases or decreases, the signal level increases or decreases. Is used to suppress the diaphragm operation of the auto iris lens. As a result, the DC drive type auto iris lens can be used under high illuminance without providing a mechanical diaphragm limiting stopper.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an embodiment of a drive circuit for an auto iris lens according to the present invention.

FIG. 2 is a voltage waveform diagram for explaining the operation of the drive circuit of the auto iris lens according to the present invention.

FIG. 3 is a diagram showing a relationship between incident light and diaphragm drive voltage.

[Explanation of symbols]

 1 Auto Iris Lens 2 Image Sensor (CCD) 3 Sample and Hold Circuit (S / H Circuit) 4 Process Circuit 5 Video Output 6 Detector 7 Subtractor (Operational Amplifier) 8 Comparator 9 Comparator 10 AND Operation Circuit (AND Circuit) 11 Integrator (operational amplifier) 12 Transistor L1 Aperture drive coil R2 Variable resistor for voltage setting R5 Variable resistor for voltage setting R6 Variable resistor for voltage setting R7 Integrating resistor R8 Integrating resistor R9 Integrating resistor C2 Integrating capacitor C3 Integrating capacitor C4 Integrating capacitor S Reset switch

Claims (1)

[Claims] 1. An auto iris lens for detecting a signal from an image pickup device and driving a diaphragm with a drive voltage based on the detected output, the first comparator for comparing the detected output with a first set level; A first integrator circuit for integrating the output of the comparator, a second comparator for comparing the detected output with a second set level, and a second comparator for integrating the output of the second comparator.
An integration circuit, an AND operation circuit for performing an AND operation on the integration value of the first integration circuit and the integration value of the second integration circuit, an integrator for integrating the output of the AND operation circuit, and an output from the integrator. A drive circuit for an auto iris lens, which is configured with a limiter circuit that limits the drive voltage of the auto iris lens based on the above.