JP3124868B2 - Speed control device such as zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device such as a zoom lens used for a television camera or the like.

[0002]

2. Description of the Related Art A conventional speed control device such as a zoom lens is disclosed in, for example, Japanese Patent Application Laid-Open No. S51-40924. That is, as shown in FIG. 4, two variable resistors connected to two variable gain amplifiers 5 and 6 having variable resistors 3 and 4 connected to the reference voltage generating circuit 2 are provided at both ends of the potentiometer 1. Devices 7 and 8 are connected, and the potentiometer 1 is configured to drive a lens driving circuit 11 via an amplifier 10 having a fixed resistor 9. Note that the four variable resistors 3, 4, 7, and 8 are set so as to interlock with each other, but these four variable resistors 3, 4
In the case where the components 4, 7, and 8 are constituted by independent components, it is necessary to make adjustments using a voltage measuring device or the like.

[0003]

However, in order to arbitrarily change the relationship between the operation amount of the speed operation unit and the command signal voltage in the conventional circuit, a quadruple volume is required, and the shape of the operation unit becomes large. At the same time, in order to prevent the maximum value (positive or negative) of the output voltage from fluctuating, a quadruple volume having special characteristics and almost no variation is required, which makes actual commercialization difficult. There is a point.
Further, this circuit has a problem that the relationship between the operation amount of the speed operation unit and the speed command signal voltage cannot be set to be one-to-one.

Generally, the same speed operation unit such as a zoom lens is commonly used to maintain compatibility regardless of the type and characteristics of the zoom lens. For this reason, the speed at which the relationship between the operation amount of the speed control unit and the speed command signal can be set and changed over a wide range according to the type of zoom lens, the content of the program to be produced, and the preference and familiarity of the cameraman who operates the lens. There is a need for an operation unit.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a speed control device such as a zoom lens that can arbitrarily change a relationship between an operation amount of a speed operation unit and a speed command signal voltage.

[0006]

According to the present invention, there is provided a zoom lens speed control apparatus comprising: a potentiometer for generating a command voltage for speed control;
In a zoom lens having a servo amplifier for amplifying the command voltage and a servomotor for moving a lens group based on the output of the servo amplifier, the potentiometer is constituted by a variable resistor with a center tap interposed therebetween, and the potentiometer Are connected to a positive and negative reference power supply, and a first amplifier having a non-inverting (or inverting) amplifying function is connected to the variable resistor via a sliding portion, and the output of the first amplifier is connected to the variable resistor. Connected to a lens drive circuit section, connected to a second amplifier having a variable resistor having a continuously variable resistance value and having an inverting (or non-inverting) amplifying function, and outputting the output of the second amplifier to the second amplifier. It is characterized in that it is connected to a center tap.

The lens speed control device includes a resistor, a power supply for applying positive and negative reference voltages to both ends of the resistor, a sliding portion for sliding the resistor in conjunction with an operation, A first amplifier having a non-inverting (or inverting) amplifying function by inputting an output obtained through a sliding portion, a lens driving circuit connected to an output of the first amplifier, and an output of the first amplifier And a second amplifier having an inverting (or non-inverting) amplifying function, and an output of the second amplifier is connected to the center of the resistor.

[0008]

In the speed control device such as a zoom lens having the above-mentioned structure, a sliding portion connected to a resistor is connected to a first amplifier having a constant gain, and a second variable gain is provided at the center of the resistor.
By changing the gain of the second amplifier, the relationship between the operation amount of the speed operation unit and the speed command signal voltage is continuously changed from one-to-one to an arbitrary characteristic.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a block diagram of the first embodiment, which is for a speed control device such as a zoom lens. A potentiometer 22 is connected to both ends of a reference power supply 21 whose voltages at both ends are + V and -V. This potentiometer 22 is composed of variable resistors 24 and 25 having the same resistance value of RX with a center tap 23 interposed therebetween. The variable resistor 24 is variably connected to a sliding portion 26 that moves in conjunction with the zoom operation of the cameraman, and sets the resistance value X from the center tap 23 to the sliding portion 26 to 0 ≦ X ≦ RX.
It can be changed within the range. The other end of the sliding portion 26 is connected to the (+) terminal of the operational amplifier 27, and the (-) terminal of the operational amplifier 27 is grounded via a fixed resistor 29 having a resistance value R1. The output terminal of the operational amplifier 27 is connected to the lens driving circuit 30 and to the (-) terminal of the operational amplifier 27 via a fixed resistor 31 having a resistance value R2.

Further, the center tap 23 is provided with an operational amplifier 32.
And the resistance value is 0 ≦ VR3 ≦
Operational amplifier 3 via variable resistor 33 variable in the range of R3
2 (-) terminal. The operational amplifier 32
The (+) terminal is grounded, and the (-) terminal is connected to the lens drive circuit 30 via a fixed resistor 35 having a resistance value R4.

For the sake of explanation, the voltage value of the sliding portion 26 is
V1, the voltage value of the center tap 23 is V2, and the output voltage value of the operational amplifier 27 is V3. In such a configuration, when the output voltage value V3 of the operational amplifier 27 is calculated, first, the gain A1 of the operational amplifier 27 becomes constant at A1 = (R1 + R2) / R1, and the output voltage value V3 is expressed by the following equation. V3 = V1 · A1 ... (1)

Since the gain A2 of the operational amplifier 32 is -A2 = -VR3 / R4, its value ranges from -A2 = 0 to (-R3 / R4) (2). Here, the maximum amplification rate is R3 / R4. Further, the voltage value V2 of the center tap 23 is as follows. V2 = V3 · (−A2)… (3)

The voltage value V1 of the sliding portion 26 is as follows: V1 = (+ V−V2) (X / RX) + V2 (4) From these equations (1) to (4), the output voltage value V3
Is given by V3 = V1 · A1 = (+ V-V2) (X / RX) A1 + V2 · A1 = (+ V + A2 · V3) (X / RX) · A1-A1 · A2 · V3

When this equation is rearranged with respect to V3, the following equation is obtained. {1-A1 • A2 • (X / RX) + A1 • A2} • V3 = + V • A1 •
(X / RX)

Thus, the output voltage value V3 is expressed by the following equation. V3 = ｛+ V ・ A1 ・ (X / RX)} / ｛1-A1 ・ A2 ・ (X / R
X) + A1 · A2｝ = (+ V · A1 · X) / (RX + A1 · A2 · RX
−A1, A2, X)… (5)

This equation (5) indicates that when X = 0, V3 = 0,
When X = RX, V3 = + V · A1, and a fixed voltage is output in each case. When A2 = 0, that is, when VR3 = 0,
V3 = (+ V.A1 / RX) .X, and the output voltage value V3 linearly increases with respect to the resistance value X. Generally, from the relationship of X ≦ RX, A1 · A2 · RX−A1 · A2 · X ≧ 0, and V3 = a · X /
The non-linear characteristic of (bc × X) is obtained. Where a,
b and c are positive fixed constants, and bc · X> 0 for an arbitrary resistance value X.

FIG. 2 is a characteristic diagram of the speed command signal voltage in the circuit of FIG. 1, wherein a straight line with a gain of 0 is realized when VR3 = 0 and a curve of the maximum gain is realized when VR3 = R3. Is shown. When 0 <VR3 <R3, the curve becomes an intermediate curve between the above two curves according to the value of the resistance value VR3 of the variable resistor 33.

In the first embodiment, it is assumed that the sliding portion 26 is connected to the variable resistor 24.
When connected to the fifth side, the output voltage value V3 provides an output having similar characteristics only by inverting the sign. As described above, by adjusting the variable resistor VR3, appropriate zoom operation or lens speed control according to the subject can be performed.

FIG. 3 is a block diagram of the second embodiment, and the same reference numerals as those in FIG. 1 denote the same members.
A sliding portion 41 is connected to the variable resistor 24, and the sliding portion 41
Is connected to the (-) terminal of an operational amplifier 43 via a fixed resistor 42 having a resistance value R5, and further connected to the (-) terminal via a fixed resistor 44 having a resistance value R6. Connected to the output end of the The output terminal is connected to the lens drive circuit 30 and is grounded via a variable resistor 45 having a resistance value of 0 ≦ VR7 ≦ R7. The (+) terminal of the operational amplifier 43 is also grounded.

Further, the center tap 23 is connected to an operational amplifier 48.
Connected to the output terminal of the fixed resistor 4 having a resistance value of R8.
9 is connected to the (-) terminal of the operational amplifier 48. This (-) terminal is grounded via a fixed resistor 50 having a resistance value R9.

For the sake of explanation, the voltage value of the sliding portion 41 is
V4, the voltage value of the center tap 23 is V5, and the output voltage value of the operational amplifier 43 is V6. From center tap 23 to sliding part 4
It is the same as the first embodiment that the resistance value up to 1 is X and the value is in the range of 0 ≦ X ≦ RX.

In such a configuration, the operational amplifier 43
Is calculated, first, the gain A3 of the operational amplifier 43 becomes constant as -A3 = -R6 / R5, and the output voltage value V6 is expressed by the following equation. V6 = −V4 · A3… (6)

The gain A4 of the operational amplifier 48 is given by A4 =
{(R8 + R9) / R9｝ · (VX / VR7) Here, VX indicates the resistance value between the ground of the variable resistor 45, and the maximum value is R7
Therefore, the resistance value VX and the gain A4 take values of VX = 0 to R7 and A4 = 0 to (R8 + R9) / R9 (7), respectively.

The output voltage value V5 of the operational amplifier 48 is given by the following equation. V5 = V6 ・ A4… (8)

The voltage value V4 of the sliding portion 41 is as follows: V4 = (+ V−V5) (X / RX) + V5 = (+ V−V6 · A4) (X / RX) + V6 · A4 (9) From the equations (6) to (9), the operational amplifier 4
The output voltage value V6 of 3 is as follows: V6 = -V4A3 = -A3 (V-V6A4) (X / RX) + V6A4 = -A3-V (X / RX) + A3A4V6 X / RX) + V6
A4, and rearranging the output voltage value V6 gives: {1-A33A4 ・ (X / RX) + A4｝ V6 = -A3 ・ V ・ (X /
RX). From this, V6 = {-A3 · V · (X / RX)} / {1-A3 · A4 · (X / RX) + A4} =-(A3 · V · X) / (RX + A3 · A4・ RX-A3 ・ A4 ・ X) ... (10) is obtained.

The equation (10) is identical to the equation (5) of the first embodiment except that the polarity is inverted. That is, the output characteristics obtained in the second embodiment are the same as those in the first embodiment, and the characteristics shown in FIG. 2 are obtained. The reversal of the polarity can be eliminated by reversing the wiring of the reference power supply 21 connected to the potentiometer 22.

In this manner, the speed operation unit of the present invention can be used for all zoom lenses having different characteristics and specifications, and operates the lens according to the lens operation characteristics according to the contents of the program to be produced, the cameraman's familiarity, and his / her preference. The characteristic of the speed command signal voltage at the time of performing can be arbitrarily selected and set. Furthermore, since it can be used for all zoom lenses having different characteristics and specifications, maintenance and backup at the time of failure can be easily performed, which is a great advantage for the user side.

In the embodiment, the description has been given of the zoom lens speed control device. However, the present invention is also effective for a position control device such as a lens focus operation. In the case of this lens focusing operation, there is a problem that the amount of movement of the focus lens is large on the close side and small on the infinite side, which cannot be solved theoretically.

For this reason, the relationship between the operation amount of the focus operation unit and the position control voltage is one-to-one depending on the place where the program is shot, the type and characteristics of the zoom lens, the preference of the cameraman, and the like.
There are demands that vary widely from to non-linear characteristics. For example, if you produce a program indoors like a studio,
Since the close side of the focus is often used, a one-to-one linear characteristic that facilitates the close operation is preferred. Linear characteristics are preferred. In addition, when there is a subject from a close position to an infinite position, an intermediate characteristic is preferred.

As described above, the required characteristics differ depending on the type of lens and the preference of the cameraman. The present invention can cope with such a case by changing a part of the device.

[0031]

As described above, in the speed control device such as the zoom lens according to the present invention, the maximum output voltage and the sliding portion are located at the center of the resistor by changing the gain of the amplifier using the resistor. It is possible to continuously change the relationship between the operation amount of the speed operation unit and the output voltage from one-to-one to a predetermined non-linear characteristic without changing the voltage at the time of reaching. Further, the size can be reduced and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block circuit configuration diagram of a first embodiment.

FIG. 2 is a characteristic diagram of a speed command signal voltage.

FIG. 3 is a block diagram illustrating a block circuit according to a second embodiment;

FIG. 4 is a block circuit configuration diagram of a conventional speed control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 21 Reference power supply 22 Potentiometer 23 Center tap 24, 25, 33, 45 Variable resistor 29, 31, 35, 42, 44, 49, 50 Fixed resistor 26, 41 Sliding part 27, 32, 43, 48 Operational amplifier 30 Lens drive circuit

Claims (3)

(57) [Claims] And 1. A potentiometer for generating a command voltage for speed control, and a servo amplifier for amplifying the command voltage, the zoom lens and a servo motor for moving the lens group on the basis of the output of the servo amplifier ,
The potentiometer is constituted by a variable resistor having a center tap interposed, positive and negative reference power supplies are connected to both ends of the potentiometer, and the variable resistor has a non-inverting (or inverting) amplifying function via a sliding portion. A first amplifier having a variable resistor having a continuously variable resistance value and an inverting (or non-inverting) amplifying function. A speed control device for a zoom lens, wherein the speed control device is connected to a second amplifier, and an output of the second amplifier is connected to the center tap. 2. A resistor, a power supply for applying positive and negative reference voltages to both ends of the resistor, a sliding portion for sliding the resistor in conjunction with an operation, and a resistor provided through the sliding portion. Amplifier having a non-inverting (or inverting) amplifying function and a lens driving circuit connected to the output of the first amplifier
And a second amplifier having an inverting (or non-inverting) amplifying function by receiving an output of the first amplifier and having an output of the second amplifier connected to the center of the resistor. A lens speed control device. 3. The lens speed control device according to claim 2, wherein the second amplifier includes a resistor having a variable resistance value.