JPS5879223A - Speed control servo circuit of zoom lens - Google Patents

Abstract

PURPOSE:To permit optional changing of the telphoto end and wide end of a zoom lens, and to make zooming operation fast by adding a window comparator, etc. to a speed control servo circuit. CONSTITUTION:A switch SW1 is turned on to connect a window comparator consisting of operational amplifiers 2 and 3 to a servo circuit. When a servomotor M is driven by the operations for setting of potentiometers P2-P4, the input terminal voltage of an amplifier 1 is made zero by the bias applied upon a diode D1 and the motor M stops. In this case, the zoom lens operates as a speed control type servo between the set value W1 and a telephoto position T1, and operates as an optionally settable position control type servo circuit at the value W1 and the position T1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control servo circuit for a zoom lens.
The present invention relates to a speed control servo circuit for a zoom lens, which allows the positions of both ends of the speed control servo circuit to be set, which also functions as a position control servo, and which also has a safety function when the set positions overlap.

(From IE, speed control type and position control panel are known as zoom lens servo functions, and depending on the purpose of use,
For example, a speed control type is used when zooming in or out of the screen, and a position control type is used when changing the composition of the screen, etc., as appropriate.

However, in conventional devices, the speed control type and the wrinkle control type have completely different components as servo circuits, so they are generally constructed as separate units, and changes in the servo function can be made in the device itself. There are drawbacks such as the need to change the servo device, lack of quick response, and the configuration of the servo device as a separate unit is economically disadvantageous.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a speed control servo circuit for a zoom lens having technical means for solving the above-mentioned conventional drawbacks.

The above technical means is configured such that a window comparator having a variable binary level is provided in the speed control servo circuit, and the position of the zoom lens is determined by the comparator so that driving of the comparator servo circuit is stopped. This makes it possible to arbitrarily set both ends of the zoom lens, that is, the telephoto end and the wide end, so that it can be used for position control even though it is a speed control lid.

The present invention will be explained below based on the preferred embodiments shown in the accompanying drawings. Figure 1 is a circuit connection diagram of the circuit of the present invention, showing the driving direction (tele or wide) and driving speed of a zoom lens (not shown). The intermediate terminal of the potentiometer P used to set the value is grounded, and the potentiometer P is attached to the zoom lens body or a pan rod (not shown). The sliding terminal of this potentiometer P1 is connected to a servo drive amplifier.

The output of the amplifier 1 is connected to a motor MK which servo drives the zooming operation of the zoom lens, and this motor M drives the zoom lens as well as the sliding terminal of a potentiometer P for detecting the zooming position and a tacho generator G.

The output of the tachogenerator G is negatively fed back to the input terminal of the amplifier 10, which serves to keep the speed of the motor M constant, that is, to eliminate uneven rotation of the motor M due to load fluctuations, thereby providing smooth operation.

Since these closed loop servo circuits are well known as speed control servo circuits, a detailed explanation will be omitted.

Furthermore, the sliding terminal of the potentiometer P4 is connected to the positive input terminals of opeances 2 and 3 constituting the window comparator via a protective resistor R1.

The negative input terminals +K of the operational amplifiers 2 and 3 of this camera are the sliding terminals of the potentiometer P, which limits the position of the tele end, through the resistors R1 and R2, and the sliding terminal of the potentiometer P, which limits the position of the wide end. are connected via resistors R4 and R1, respectively.

In addition, the output terminals of these operational amplifiers 2 and 3 are connected through a diode DI and a resistor R1 so that the voltage at the sliding terminal of the potentiometer P6 is only operated at a voltage below the limit value at the tele end, and a voltage at the potentiometer P6 above the limit value at the wide end. diode D so that it operates only at the sliding terminal voltage of P,
, and are fed back to the negative input terminal via the resistor R1.

Therefore, for these window comparators, the sliding terminal voltage of potentiometer P4 (zoom lens position) is ♂
When the voltage of the sliding terminal of the potentiometer P falls below the lower limit of the gloss level (the limit value of the tele end), the operational amplifier 2
is in the operating state, and the sliding terminal voltage of the potentiometer P4 (zoom lens position) is the upper limit value of the - side reher, that is, the potentiometer P.

If the sliding terminal voltage (limit value at the wide end) is exceeded, the operational amplifier 3 becomes active, or in the intermediate region between these levels, both operational amplifiers 2 and 3 become inactive due to the reverse bias of the diodes D1 and D1. state.

Further, the anode terminal of the diode D and the cathode terminal of the diode D are connected to each other and serve as output terminals of a window comparator, which are connected to the input terminal of the amplifier 10 via a switch 8W.

Here, the connection point between the resistors R1 and R3 and the resistor R4
The negative input terminal and positive input terminal of the operational amplifier 4, which are negatively fed back through the diode D, are connected to the connection point between and Rs('), respectively, and when the limit value at the tele end and the limit value at the wide end overlap, The limit value at the tele end is forcibly set to the limit value at the wide end, and this forced setting value may be set at the tele end. In this case, the polarity of the positive and negative inputs of operational amplifier 4 and diode D are reversed This is achieved by connecting.

The operation of the speed control servo circuit of the zoom lens having the above configuration will be explained. First, when the switch 8W is in the OFF state, the conventional speed control servo circuit is activated. A case will be described in which a window comparator is connected to this servo circuit, that is, a case where the telephoto end and wide end positions of the zoom lens can be controlled.

Now, the zoom lens operator turns the sliding terminal of the potentiometer P and sets it to the (T1) position shown in FIG. 2B, for example.

Rotate the sliding terminal and set it, for example, to the 6vt) position in Figure 2 (a), and the zoom lens position, that is, the sliding terminal voltage of potentiometer P4 is at an intermediate value between (W, ) and (T,). do.

In this state, when the sliding terminal of the potentiometer P is rotated a predetermined amount, for example in the telephoto direction, the servo motor M is driven at a speed proportional to the amount of rotation. When the zoom lens reaches the telephoto position ('i'+)K by this driving, the voltage at the sliding terminal of the potentiometer P tends to fall below the voltage at the sliding terminal of the potentiometer P.

Therefore, the diode D1 is biased in the forward direction, and the operational amplifier 2 is activated so that the input terminal voltage of the amplifier 10 becomes zero, and the servo motor M is stopped, that is, the zoom lens is stopped at this telephoto position.

Similarly, when the hydraulic terminal of the potentiometer P is rotated a predetermined amount, for example in the wide direction, the zoom lens is zoomed at a speed proportional to the amount of rotation, and the operational amplifier 3 is at the wide position (9), ). starts and stops.

Therefore, the zoom lens has these set values CW, ) and (
TI), it operates as a speed control type servo circuit, and at the set values (9), ) and (T,), it operates as a position control type servo circuit, which is arbitrarily set.

Here, as shown in Figure 2 (b), the tele end setting value (T, )
When the wide end setting values overlap, that is, when the sliding terminal voltage of potentiometer P exceeds the sliding terminal voltage of potentiometer P, the ohde D is forward biased and the operational amplifier 4 is activated. The negative input terminal voltage of the operational amplifier 2 is strongly set to the terminal voltage of the potentiometer P to prevent the window comparator from being inactive. This state is shown in Figure 2 (c), in which case the complete position (TI, W,)
Needless to say, it operates as a control servo circuit.

As explained above, according to the circuit of the present invention, by adding a window comparator etc. to the speed control servo circuit,
The telephoto end and wide end of the zoom lens can be easily changed as desired, making it possible to use the zoom lens for position control.

In addition, since the added special circuit is a simple circuit, it can be easily incorporated into the existing speed control servo circuit.Furthermore, the additional circuit can be activated or deactivated by opening or closing a switch, increasing the sophistication and speed of zooming operations. It is possible to provide a zoom lens speed control servo circuit with unprecedented high performance, such as dramatically improved speed.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing an embodiment of the present invention and 117
2gl is an example of the setting state in this circuit, and shows the normal case (a), the case of over-two-tube (b), and the case of activation of the safety circuit at the time of overship, V→. 1... Servo 5-motion amplifier, M... Servo motor, G
.../cosienerator, 2.3 and 4... operational amplifier sp, J! IPI and P4...potentiometer, Dl e DB and..., diode, BW,...switch, a, s R1*fusion@R4@R@t K@ and R1...resistance. Applicant: Fuji Photo-Koki Co., Ltd.

Claims (1)

[Claims] 1) A speed control servo circuit for a zoom lens that servo-drives the zoom lens in the tele or wide direction at a speed corresponding to the amount of rotation of a manually operated potentiometer,
A potentiometer that detects the position of this servo-driven zoom lens and a window controller that converts the output level of this potentiometer to a variable level of 200 million are provided so that the servo circuit is stopped by the output level of this comparator. A speed control servo circuit for a zoom lens, characterized in that: 2) the window comparator includes means for forcibly setting one value when the variable 200 million levels overlap; Speed control servo circuit for zoom lens described in item $1.