JPH032847A - Automatic diaphgram control device for tv camera lens - Google Patents

Abstract

PURPOSE:To obtain a stable picture signal under a wide range of object condition by adjustably constituting the reference terminal voltages of amplifiers. CONSTITUTION:The output terminal 33 of an operational amplifier 3 is constituted such that a voltage is supplied to a driving coil 5 in proportion to a control signal. In this time, when the object condition brightens, the rectifying signal obtained from a comparison with the reference voltage by a reversal amplifier 1 hightens; the control signal of the output terminal 33 obtained from a comparison with the reference voltage by the operational amplifier 3 lowers; the voltage of the driving coil 5 decreases; a diaphgram is driven in a closing direction. Contrarily, when the object condition darkens, the rectifying signal obtained from the comparison with the reference voltage lowers; the voltage of the driving coil 5 increases; a servometer M is driven in a direction opening the diaphgram. Therefore, by adjusting the voltage of the voltage terminal 2 with a variable resistance VR2, reference voltages of the amplifiers 1 and 3 are adjusted respectively, and output voltage can be adjusted at a most suitable picture signal level. Thus, a stable picture signal can be obtained under the wide range of the object condition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to automatic aperture control ral+ for television camera lenses.
Regarding equipment.

2. Description of the Related Art Traditionally, automatic aperture control devices for television camera lenses have been known to use a one-sided spring drive system.
Since the drive voltage range was narrow and unreliable, the drive 1b that controls the aperture in both opening and closing directions has been praised for its high reliability and low current consumption.

Problems to be Solved by the Invention Recently, TV camera lenses are particularly desired to be compact, so conventional bidirectional drive type lenses have complicated structures and control circuits, resulting in problems. There was a problem.

Means for Solving the Problems The present invention provides an automatic aperture control device that controls the aperture of a lens using an image signal from a television camera. An amplifier that amplifies the signal greatly and conversely amplifies it small when it is large, making it possible to adjust the optimal image signal level of the TV camera, and rectifying it after passing through it (4) Amplification of the rectified signal and a servometer for aperture control. The base terminal voltage of the amplifier is configured to be able to adjust the damping by the feedback signal from the detection coil, and a stable image signal can be obtained under a wide range of subject conditions. It is an object of the present invention to provide an automatic aperture control device for a television camera lens that is capable of simplifying the drive mechanism and achieving miniaturization, is highly reliable, and has low current consumption.

EXAMPLES The present invention will be described in detail with reference to examples shown below.
In the figure, W is an input terminal for inputting an image signal (2) from a television camera, and is connected to the inverting input terminal 11 of the operational amplifier 1 according to the present invention via a capacitor CI and a resistor R2. A non-inverting input terminal 12 of the operational amplifier 1 is connected to a reference terminal 2, which will be described later, via a resistor R3, and a variable resistor VRI is connected in series between the inverting input terminal 11 and the output terminal 13 as a feedback resistor. be. Input terminal W is resistor R1
It is connected to the ground via GND.

The operational amplifier 1 is configured to invert and amplify the image signal (2) from which the DC component has been removed using the capacitor C2, and obtain an inverted amplified signal at its output terminal 13.
J! By adjusting il, the gain of operational amplifier Al (
The structure allows the amplification factor to be changed continuously. In other words, increasing the resistance value of the variable resistor VRI increases the gain, and conversely decreasing the resistance value decreases the gain, so for example, the optimal image signal level of the camera is high,
When the input image signal υ-■ is high, the amount of input change becomes large, but in such a case, the resistance value should be reduced to reduce the gain, and conversely, when the amount of input change of the image signal V is small, The structure is such that an inverted amplified signal with a constant output is always obtained by increasing the resistance value and adjusting the gain to increase. In addition, adjusting the optimal image signal level so that the amplifier gain is high when the input signal level is small and low when it is large: This not only keeps the response speed constant, but also suppresses hunting.
This is particularly effective when space is limited due to miniaturization.

The inverted signal obtained by the above-described inverting amplifier circuit is rectified by a subsequent rectifying circuit. The rectifier circuit is configured to connect a diode D1 in the forward direction to the output terminal 13 of the amplifier 1 to obtain a rectified signal.

A capacitor C2 and a resistor R4 are each provided between the ground GND and the ground GND in order to smooth the rectified signal. The rectified signal is connected via a resistor R6 to an inverting input terminal 31 of an operational amplifier 3 constituting the present invention for obtaining a control signal for automatic diaphragm servo make. A resistor R7 is provided between the inverting input terminal 31 and the output terminal 33 of the operational amplifier 3 as a feedback resistor that determines the amplification factor in proportion to the resistor R7. C3 is an integrating capacitor provided in parallel with resistor R7. Further, the output terminal of the operation detection coil 4 of the servometer M for diaphragm control is connected to the input terminal 31 via a resistor R5, so that a damping feedback signal for braking the servometer M can be obtained. It is composed of: The other output end of the detection coil 4 is connected to the reference terminal 2. Furthermore, the non-inverting input terminal 32 is connected to the reference voltage terminal 2.
is connected to via a resistor R8, and compares the rectified signal and the braking signal of the detection coil 4 with a reference voltage,
When the signal at the inverting input terminal 31 is large, the difference from the reference voltage at the non-inverting input terminal 32 becomes small, and the signal at the output terminal 33 becomes smaller.
The control signal is small, and conversely, when the signal at the inverting input terminal 31 is small, the difference from the reference voltage at the non-inverting input terminal 32 becomes large, so that a large control signal can be obtained at the output terminal 33. . C4 is output terminal 33 and ground G
This is a smoothing capacitor installed between the ND and the ND.

The output terminal 33 of the operational amplifier 3 is connected to the drive coil 5 of the servometer M, and the other terminal of the coil 5 is connected to the ground GND of the power supply circuit to supply the drive coil 5 with a voltage proportional to the control signal. As such, there is no tR.

The servometer M for driving the diaphragm is always biased with a rotational force by a spring in the direction of closing the diaphragm, and the drive coil 5 drives the servometer M in the direction of opening the diaphragm against the spring. The configuration is such that aperture control is performed in balance with the above. The drive coil 5 is configured to receive a control signal from the operational amplifier 3 so that the driving forces of the spring and the servometer M are balanced.

Further, the reference voltage supply circuit according to the present invention is connected via a variable resistor VR2 so as to output a voltage at an intermediate level (preferably approximately 1/2) of the stabilized power supply voltage to the reference voltage terminal 2. . In the case of the embodiment, a smoothing capacitor C6 and series resistors RIO and R11 having approximately equal resistance values are provided in parallel between the positive terminal R and the ground GND, and a variable resistor VR2 is connected between the resistors R10 and R11. A reference voltage terminal 2 is connected to the reference voltage terminal 2, and the power supply voltage is adjusted and supplied to the reference voltage terminal 2. C5 is a smoothing capacitor connected between the reference voltage terminal 2 and the ground side GND.

The operation mode of the present invention will be explained with reference to an embodiment having the above configuration.The image signal (2) from the television camera has its DC component removed by the capacitor C1, and is supplied from the base voltage terminal (2) by the operational amplifier (1). The signal is inverted and amplified using the reference voltage as a reference, and becomes an inverted signal at its output terminal 13. The gain (amplification factor) of this operational amplifier 1 is determined by the ratio of the resistance value of the variable resistor VRI to the resistor R2, so by adjusting the variable resistor VRI, the gain can be varied depending on the resistance value, and the amplitude of the inverted signal can be adjusted. Can be scaled.

This inverted signal is input to the diode D1, subjected to DC regeneration, inputted to the inverted input terminal 31 of the operational amplifier 3, and compared with the voltage at the reference voltage terminal 2 of the non-inverted input terminal 32.
A control signal is available at output terminal 33. At this time, the feedback signal of the detection coil 4 of the servometer M is also input to the inverting input terminal 31, so the control signal is damped by the braking signal of the servometer M and is supplied to the drive coil 5 of the servometer M. It happens.

The operation of the drive coil 5 is, for example, when the drive coil 5 is keeping the aperture at a predetermined opening angle based on a control signal when the optimum image signal is obtained for a predetermined subject, and if the condition of the subject does not change, the control signal is also activated. It does not change and the voltage of the drive coil 5 is also maintained, but if the condition of the object changes, for example, it becomes brighter, the rectified signal that is the result of being compared with the reference voltage by the inverting amplifier l becomes high, and the voltage of the operational amplifier increases. 3, the base f$ lightning voltage is compared, the control signal at the output terminal 33 becomes smaller, the voltage at the drive coil 5 decreases, and the diaphragm is driven in the closing direction.
The next iJ image signal state will be maintained. Conversely, if the subject condition becomes dark, the rectified signal becomes lower by comparison with the reference voltage, the output signal (control signal) of the operational amplifier 3 becomes larger, the voltage of the drive coil 5 increases, and the servometer M is driven in the direction of opening the aperture, and the next optimum image signal state is reached and the balance is maintained.

Therefore, by adjusting the voltage of the reference voltage terminal 2 with the variable resistor VR2, the reference voltage of each amplifier 1.3 is adjusted, and the change in the control signal is minimized to adjust the optimum image signal level output voltage. As a result, not only can the offset be adjusted to keep the response speed constant, but also hunting can be suppressed. It is valid. Furthermore, limiting the output voltage leads to limiting the output current, which is effective for miniaturization.

As can be understood from the above, by adjusting the level and limiting the output voltage using the configuration described above, even if the image signal supplied from the TV camera to the lens varies slightly, it will not become a problem at high brightness. Hunting can be suppressed and stable image signals can be obtained under a wide range of subject conditions.

Effects As described above, according to the automatic aperture control device for a lens for a television camera according to the present invention, in the automatic aperture control device that controls the aperture of the lens using the image signal of the television camera, When the image signal level to be supplied is small, it is amplified greatly, and conversely, when it is large, it is amplified small, and the optimal image signal level of the TV camera is determined by iJ! The reference terminal voltage of the amplifier is adjusted by the amplifier that enables J adjustment, the amplification of the rectified signal obtained by rectification after passing through it, and the feedback signal from the detection coil of the servometer for aperture control to apply damping. By adjusting the image signal level, limiting the output voltage, and adjusting the offset, even if the image signal supplied from the TV camera to the lens varies slightly, it also prevents hunting, which is a problem at high brightness. However, this has the effect of suppressing this and obtaining stable image signals under a wide range of subject conditions.

[Brief explanation of drawings]

The figure is a circuit diagram of an embodiment of the device of the present invention. 1.3...Operation amplifier 2...Midpoint voltage terminal 4...Detection coil 5... Drive coil W...Image signal input terminal R...Power supply voltage positive side terminal GND...power supply voltage negative side terminal M...Servometer

Claims (1)

[Claims] In an automatic aperture control device that controls the aperture of a lens using the image signal from a television camera, when the image signal level supplied from the television camera to the lens is low, it is greatly amplified, and when it is high, it is amplified to a small degree and the image signal is amplified to the TV. An amplifier that can adjust the optimal image signal level of the camera, and an amplifier that amplifies the rectified signal obtained by rectifying it after passing through it, and damps it by the feedback signal from the detection coil of the servometer for aperture control. 1. An automatic aperture control device for a television camera lens, characterized in that the reference terminal voltage of the lens is adjustable, and a stable image signal can be obtained under a wide range of subject conditions.