JP3544009B2 - Zoom speed control device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a zoom speed control device such as a television lens.
[0002]
[Prior art]
As disclosed in, for example, Japanese Patent Application Laid-Open No. S51-40924, a conventional zoom speed control device for a television lens or the like controls a drive system such as a motor and the operation of the drive system for a zoom of the television lens or the like. The control is performed by a servo unit including a control system, and a zoom speed control device is used to supply a command signal to the control system in the servo unit.
[0003]
FIG. 6 is a circuit configuration diagram of such a zoom speed control device. Variable gain amplifiers 4 and 5 having variable resistors 2 and 3 are provided at both ends of a reference voltage generating circuit 1 having voltages at both ends of + V and -V. Are connected respectively. The output terminals of these variable gain amplifiers 4 and 5 are connected to both ends of a potentiometer 6 for detecting the operation amount of the zoom operation lever.
[0004]
The potentiometer 6 is configured such that the resistance values on both sides thereof are equal to Rx with a center tap 7 connected to the center of the potentiometer 6 interposed therebetween, and the potentiometer 6 has a sliding portion 8 that slides in conjunction with the zoom operation of the cameraman. Is connected, so that the resistance value r from the center tap 7 to the sliding portion 8 can be changed within a range of 0 ≦ r ≦ Rx. The sliding portion 8 is connected via a fixed resistor 9 to an operational amplifier 11 having a fixed resistor 10, and the output terminal of the operational amplifier 11 is connected to the center tap 7 and the lens drive circuit 12.
[0005]
During the zooming operation, the reference voltages + V and -V from the reference voltage generating circuit 1 are amplified to arbitrary voltages by the variable gain amplifiers 4 and 5, and applied to both ends of the potentiometer 6. The operational amplifier 11 outputs a drive signal Vcs according to the amount of movement of the sliding portion 8 of the potentiometer 6, and the lens drive circuit 12 drives the lens drive circuit 12 according to the drive signal Vcs.
[0006]
[Problems to be solved by the invention]
However, in the above-described conventional example, there is no command signal correction means when the displacement of the center tap 7 of the potentiometer 6 occurs due to a deformation of the mechanical system due to a temporal change or the like in the zoom speed control device or a deterioration in the performance of the potentiometer 6. Therefore, there is a problem that the voltage generated due to the deviation is output to the lens driving circuit 12 and the automatic zooming phenomenon in which the lens moves automatically even when the cameraman does not operate the zoom operation lever.
[0007]
SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problem and to provide a zoom speed control device capable of stopping the automatic zooming phenomenon even when the automatic zooming phenomenon occurs.
[0008]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a zoom speed control device comprising: mode switching means for switching to a mode for canceling automatic zooming in which a lens automatically moves without operating a zoom operation lever ; and mode switching. Means for holding, as a comparison signal, an operation command signal from the zoom operation lever when switching to the automatic zoom cancel mode by means; and a comparison signal output from the sample and hold means and the zoom operation lever. a command signal comparing means to compare the operation instruction signal output, operation command signal a drive command signal to be output to the lens driving circuit according to the comparison result of the command signal comparing means is outputted from the zoom operating lever or command signal switching for switching to any of the reference command signal the zooming does not operate Characterized by comprising a stage.
[0009]
[Action]
The zoom speed control device having the above-described configuration holds the operation command signal from the zoom operation lever when the mode is switched to the automatic zoom cancel mode by the mode switching unit in the sample and hold unit as a comparison signal. And an operation command signal from the zoom operation lever, and according to the comparison result, outputs either the operation command signal from the zoom operation lever or the reference command signal as a drive command signal to the lens drive circuit, thereby achieving zooming. Drive the lens.
[0010]
【Example】
The present invention will be described in detail based on the embodiment shown in FIGS.
FIG. 1 is a circuit configuration diagram of the first embodiment. Variable gain amplifiers 24 and 25 having variable resistors 22 and 23 are provided at both ends of a reference voltage generation circuit 21 that generates + V and −V voltages, respectively. The output terminals of these variable gain amplifiers 24 and 25 are connected to both ends of a potentiometer 26 for detecting the operation amount of the zoom operation lever.
[0011]
The potentiometer 26 is configured such that the resistance values on both sides thereof are equal to Rx with a center tap 27 connected to the center of the potentiometer 26 interposed therebetween. Is connected so that the resistance value r from the center tap 27 to the sliding portion 28 can be changed within a range of 0 ≦ r ≦ Rx.
[0012]
The sliding portion 28 is connected via a fixed resistor 29 to an operational amplifier 31 having a fixed resistor 30. A command signal Vcs' from an output terminal of the operational amplifier 31 is supplied to a center tap 27, a command signal output switch. 32 terminal 32a, the (+) terminal of the buffer circuit 33, and the (-) terminal of the comparator 34. The terminal 32b of the command signal output switch 32 is provided, and the command signal Vcs output from the output terminal of the command signal output switch 32 is connected to the lens drive circuit 35. In a normal state, the command signal output switch 32 is electrically connected to the terminal 32a.
[0013]
Further, the output terminal of the buffer circuit 33 is connected to the (-) terminal of the buffer circuit 33 and one end of the command signal hold switch 36, and the other end of the command signal hold switch 36 is connected to the (+) terminal of the command signal hold capacitor 37 and the buffer circuit 38. ) Terminal. The command signal hold capacitor 37 is grounded at the other end. The output terminal of the buffer circuit 38 is connected to the (-) terminal of the buffer circuit 38 and the (+) terminal of the comparator 34, and the output terminal of the comparator 34 is connected to one end of a mode switch 39. The end is connected to the control terminal of the command signal output changeover switch 32.
[0014]
On the other hand, the other end of the automatic zooming cancel switch 40, one end of which is grounded, is connected to the control terminals of the command signal hold switch 36 and the mode changeover switch 39, and when the automatic zooming cancel switch 40 is on, The command signal hold switch 36 is turned off and the mode changeover switch 39 is turned on. Conversely, when the automatic zooming cancel switch 40 is turned off, the command signal hold switch 36 is turned on and the mode changeover switch 39 is turned off. Are turned off.
[0015]
During the zooming operation, the reference voltages + V and -V from the reference voltage generating circuit 21 are amplified to arbitrary voltage values by the variable gain amplifiers 24 and 25 and applied to both ends of the potentiometer 26. With the movement of the sliding portion 28 of the potentiometer 26 by the operator's zoom operation, a command signal Vcs' as shown by the solid line in FIG. 2 is output to the output terminal of the operational amplifier 31. When the lever is not operated, the sliding portion 28 of the potentiometer 26 is at the same position as the center tap 27, and a reference command signal is output so that zooming does not operate.
[0016]
However, due to changes in the mechanical system due to temporal changes in the zoom speed control device, disturbances, and the like, performance degradation of the potentiometer 26, and the like, the sliding of the potentiometer 26 is performed regardless of the state in which the photographer does not operate the zoom operation lever. The moving unit 28 may not return to the same position as the center tap 27, and the command signal Vcs' output from the operational amplifier 31 may shift as shown by the broken line in FIG.
[0017]
In such an automatic zooming state, when the photographer turns on the automatic zooming cancel switch 40 and enters the automatic zooming cancel mode, the command signal hold switch 36 is turned off, and the mode changeover switch 39 is turned on. Become. At this time, the command signal Vcs' of the operational amplifier 31 is sampled by the command signal hold capacitor 37 via the buffer circuit 33 and the command signal hold switch 36, and when the command signal hold switch 36 is turned off in this state. The command signal Vcs' at that time is held by the command signal holding capacitor 37. The held command signal Vcs ′ is input to the comparator 34 as the command hold signal Vchs via the buffer circuit 38.
[0018]
The comparator 34 has a hysteresis characteristic centered on the command hold signal Vchs. When the command hold signal Vchs> 0, the command signal is satisfied if the command hold signal Vchs satisfies the condition of 0 <Vcs ′ <2 · Vchs. conducting the output changeover switch 32 to the terminal 32b, when the command hold signal Vchs <0, if satisfied 2 · Vchs <Vcs'<0 condition, conducts a command signal output changeover switch 32 to the terminal 32 a.
[0019]
As described above, when the command signal output switch 32 is turned on to the terminal 32b side, the reference command signal is output to the lens drive circuit 35 as the command signal Vcs because the terminal 32b is grounded. When the command hold signal Vchs does not satisfy the above condition, the command signal Vcs' is output to the lens drive circuit 35 as it is, so that the automatic zooming occurs as shown by the broken line in FIG. As a result, the command signal Vcs has a characteristic as shown in FIG. 3, and it is possible to prevent the automatic zooming phenomenon in which the lens automatically moves when the cameraman does not operate the zoom operation lever.
[0020]
FIG. 4 is a block circuit configuration diagram of the second embodiment, and the same reference numerals as those in FIG. 1 indicate the same members. The output of the operational amplifier 31 is connected to a microcomputer 42 via an A / D converter 41 in addition to the center tap 27 and the terminal 32a of the command signal output switch 32. The output of the microcomputer 42 is a command signal output switch 32. Connected to the control terminal. The other end of the automatic zooming cancel switch 43 whose one end is grounded is connected to the microcomputer 42.
[0021]
FIG. 5 is a flowchart showing the processing procedure of the microcomputer 42. First, in step S1, the state of the automatic zooming cancel switch 43 is checked. If the automatic zooming cancel switch 43 is off, the switch flag is set in step S2. Set to 0 and return to step S1. This switch flag is a flag for distinguishing whether or not the mode is the automatic cancel mode, and when the switch flag is 1, it indicates that the mode is the automatic cancel mode.
[0022]
If the automatic zoom cancel switch 43 is on in step S1, the value of the switch flag is checked in step S3. If the value is 0, the switch is turned on immediately after the automatic zoom cancel switch 43 is turned on. Therefore, first, the switch flag is set to 1 in step S4. Next, in step S5, the value of the command signal Vcs', which is the output of the operational amplifier 31, is sampled via the A / D converter 41, and the value is substituted for the judgment reference command signal Vrcs. Then, the process proceeds to step S6.
[0023]
On the other hand, if the switch flag is 1 in step S3, the process directly proceeds to step S6 because the judgment reference command signal Vrcs has already been sampled. In step S6, the command signal Vcs 'to be compared is sampled, and in step S7, a value obtained by adding / subtracting the hysteresis constant x to the judgment reference command signal Vrcs is compared with the command signal Vcs' by the following equation.
(Vrcs−x) ≦ Vcs ′ ≦ (Vrcs + x)
[0024]
As a result of this comparison, if the condition of the above expression is satisfied, the microcomputer 42 conducts the command signal output changeover switch 32 to the terminal 32b in step S8. If the condition of the above expression is not satisfied, the microcomputer 42 outputs the command signal in step S9. The switch 32 is electrically connected to the terminal 32a. As described above, even if the A / D converter 41 and the microcomputer 42 are used instead of the comparator 34 and the command signal holding capacitor 37, the same effect as that of the first embodiment is obtained, and the lens is automatically moved. Automatic zooming can be prevented.
[0025]
【The invention's effect】
As described above, the zoom speed control device according to the present invention can stop the automatic zooming by switching to the automatic zooming cancel mode by the mode switching unit even when the automatic zooming occurs, thereby stopping the shooting. , Can be prevented from being stopped.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a first embodiment.
FIG. 2 is a graph showing a relationship between a rotation angle of a potentiometer and a zoom command signal.
FIG. 3 is a graph showing a relationship between a rotation angle of a potentiometer and a zoom command signal when automatic zooming is canceled.
FIG. 4 is a circuit configuration diagram of a second embodiment.
FIG. 5 is a flowchart of a processing procedure according to the second embodiment.
FIG. 6 is a circuit configuration diagram of a conventional zoom speed control device.
[Explanation of symbols]
21 Reference voltage generating circuits 24, 25 Variable gain operational amplifier 26 Potentiometer 27 Center tap 28 Sliding section 31 Operational amplifier 32 Command signal output switch 33 Lens drive circuits 33, 38 Buffer circuit 34 Comparator 36 Command signal hold switch 37 Command signal hold Capacitor 39 Mode changeover switches 40, 43 Automatic zooming cancel switch 41 A / D converter 42 Microcomputer

Claims (1)

A mode switching unit for switching to a mode for canceling automatic zooming in which the lens is automatically moved without operating the zoom operation lever, and the zoom operation lever when switching to the automatic zooming cancel mode by the mode switching unit. Sample and hold means for holding the operation command signal as a comparison signal, a command signal comparison means for comparing a comparison signal output from the sample hold means with an operation command signal output from the zoom operation lever , command signal switching means for operation command signal or the zooming outputted from the zoom operating lever according to the comparison result of the drive command signal the command signal comparing means to switch to one of the reference command signal is not activated to output to the lens driving circuit zoom speed control of the television lens characterized by comprising a preparative Location.

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