JPS58202433A - Motor-driven zooming device - Google Patents

Abstract

PURPOSE:To detect accurately the fact that zooming reaches the telephoto end or the wide end, without depending on a variation of an image of an object in a finder, by measuring a driving current value of a motor for driving a moving element for zooming. CONSTITUTION:When a changeover switch S is turned on to a telephoto terminal T side, transistors TR1, TR'1 conduct, a currnt flows to the left from the right to a motor 13, and a zoom ring is turned to the telephoto side. Also, when the changeover switch S is turned on to a wide terminal W side, transistors TR2, TR'2 conduct, a current flows to the right from the left to the motor 13, and the zoom ring is turned to the wide side. A voltage drop across a resistance R0 is varied by a load current flowing to the motor 13 at the time of zooming, therefore, by utilizing this voltage drop V0, it is detected that turning of the zoom ring reaches the telephoto end or the wide end.

Description

[Detailed description of the invention] The present invention relates to an improvement in a powered zoom device.

Conventionally, electric zoom devices have been employed in cine cameras, video cameras, and the like. With these electric zoom devices, the photographer must judge whether the zooming mechanism has reached the end position of the zoom movement based on changes in the subject image seen through the 'l''l'L7 eyeliner or electronic viewfinder. For this reason, even if a friction clutch is installed between the electric mechanism and the zooming mechanism to prevent extreme stress from being placed on the electric mechanism or the zooming mechanism,
At the telephoto or wide-angle end of zooming, the motor is delayed in stopping, which wastes power and reduces the durability of parts. In addition, electric zoom devices are also known in which a control lever is attached to a zoom ring that rotates with the camera so that zooming can be performed manually. A decision should be made, but it is difficult to expect the photographer looking through the viewfinder to make a decision accordingly. In order to allow such manual operation, it is necessary to provide a friction clutch between the electric mechanism and the zooming mechanism.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an electric zoom device that can clearly detect when zooming has reached the telephoto end or the wide end, regardless of changes in the subject image in the finder. be.

The electric zoom device of the present invention is characterized in that it is detected that the zooming mechanism has reached the end position of the zooming movement based on a change in the load current of the electric motor, and the detected signal is used to directly or Since the driving of the motor can be stopped indirectly, wasteful power consumption can be prevented and the durability of parts can be improved.

Hereinafter, the present invention will be explained based on the drawings.

Fig. 1 is a partial sectional view of a lens of a video camera equipped with an electric zoom device, Fig. J is a front view of a friction clutch portion between the electric mechanism and the zooming mechanism, and Fig. 3 is a drive circuit diagram of the motor of the electric mechanism. FIG. q is a graph showing changes in motor load current as voltage changes, and FIG. 5 is a block circuit diagram for detecting whether zooming is at the tele end or wide end state based on changes in motor load current.

The zoom lens shown in FIG. 1 consists of a focus lens group F fitted to a focus ring /, a front group lens V / and a rear group lens V2 for variable magnification that are moved in the optical axis direction by a zoom ring λ, and a fixed barrel. It is composed of a substitute image front group lens M/ and a rear group lens M2 that are integrally fitted to the
The focus lens group F moves forward and backward in the optical axis direction for focusing by rotating the focus ring/ in the optical axis direction, and the front group lens for variable magnification V/ and the rear group lens V2
shows the cam bin 6 installed in each lens frame L and evening.
and 7 is the zoom ring! It engages with a cam groove provided in a cam ring t that rotates integrally with the optical axis layer, and further
When the zoom ring λ rotates toward the optical axis, the first zoom ring λ is engaged with the guide grooves 3a and 3b provided in the optical axis direction, so that when the zoom ring λ rotates toward the optical axis, the first
The magnification is changed by moving in the optical axis direction within the range indicated by the solid line and the two-dot chain line in the figure. The focus ring / is screwed with a helicoid ring 9 integrally connected to the fixed cylinder 3 by a helicoid screw, and the cam ring r has a connecting pin IO implanted in it that passes through a circumferential groove of the fixed cylinder 3. By engaging with the zoom ring 1, focusing and zooming are performed as described above.

The structure of a zoom lens as described above is conventionally known.

Further, a zoom gear /l is rotatably fitted into the first zoom ring 2, and a friction spring 12 is engaged therebetween so as to transmit rotational force. This zoom gear l/
A forward/reverse rotation motor with a reducer attached to the fixed cylinder 3. -ta 1
The drive gear tq provided on the output shaft of No. 3 is meshed with the drive gear tq. Therefore, the rotation of the zoom ring 1 is performed by the rotation of the motor 130 being transmitted to the zoom ring 2 by the drive gear wheel 1, the zoom gear l/ that meshes therewith, and the friction spring 12. Note that the zoom ring λ can also be rotated by operating the manual operation lever 15 installed therein, and in that case, there will be no slippage between the friction spring t2 and the zoom ring 2 or between the zoom gear l/. Therefore, the rotation of the zoom ring 2 is not transmitted to the motor 13. Also, when rotated by motor 3, the end of the cam groove of cam ring g reaches lens frame DA, cam pin B of j, and at the tele or wide end where it reaches 7, between the friction spring 12 and the zoom gear //. Alternatively, excessive force is prevented from being applied to the transmission system due to slipping between the zoom lenses.

The motor 130 rotations are performed by the circuit shown in FIG. That is, when the selector switch S is turned on to the tele terminal T side, the transistors Tr/ and Tr/' become conductive, and current flows from right to left in the motor 3, which causes the motor 13 to zoom through the drive gear l#, etc. Rotate ring 2 to the tele side. Also, change the selector switch S to the wide terminal Wfl! When the IK is turned on, the transistors Tr2 and Tr2' become conductive, and current flows through the motor/3K from left to right, causing the motor 13 to rotate the zoom ring 2 toward the wide side. During zooming by the motor 13, the load current flowing through the motor 13 changes as shown in FIG. 11 by the voltage drop Vo=IRo across the resistor R in FIG. 3. The first peak of this voltage drop ■o is based on the starting current, and the peak on the right is the load current when the zoom ring 2 reaches the tele end or wide end and slip occurs at the friction spring 12. It is based on The electric zoom device of the present invention detects when the rotation of the zoom ring 2 reaches the telephoto end or the wide end by using a change in the load current, that is, a voltage drop Vo based on the load current. be.

Detection of whether the zoom ring has reached the telephoto end or the wide end is performed by the circuit shown in FIG.

That is, the voltage drop Vo across the voltage take-out resistor Ro from the drive circuit shown in FIG. 3 takes a time t2, which slightly exceeds the time t1 shown in FIG. From the point in time when V has passed, the voltage is manually input to the detection circuit, and the VO detection circuit then outputs it to the comparison circuit, excluding short-period fluctuations, and the comparison circuit uses the detected voltage 5 manually input from the VO detection circuit through a normal zooming cycle. If %<vr compared with the comparison voltage Vr which is larger than the voltage drop when the movement is being performed, the drive circuit shown in Fig. 3 is used to continue the rotation of the motor 3, or a warning is displayed on the finder. For example, by not lighting up, it is notified that zooming movement is to be performed, and when v≧Vr, the drive circuit shown in Fig. 3 is turned off by appropriate means, or a warning display on the viewfinder is turned on, etc., and zooming is performed. Informs you that the movement has reached the telephoto end or wide*.

In the electric zoom device of the present invention, as described above, since it is notified that the zooming movement has reached the telephoto end or the wide end, unnecessary slip rotation of the motor is prevented and power consumption is reduced. Not only that, but the durability of the parts can also be improved.

[Brief explanation of the drawing]

1 [J is a partial sectional view of the lens of a video camera equipped with an electric zoom device, Figure 2 is a front view of the friction clutch between the electric mechanism and the zooming mechanism, and Figure 3 is a drive circuit diagram of the motor of the electric mechanism. , Fig. 1 is a graph showing changes in motor load current, and Fig. S is a block circuit diagram for detecting whether zooming is at the tele end or wide end state based on the motor load current. /... Focus ring, F... Focus lens group, λ... Zoom ring, V/, V2... Front group lens for variable power, rear group lens, 3.
...Fixed barrel, M/, M2...Front group lens for imaging, rear group lens,...S, 5...Lens frame, 6,7...Cam bin, l
...Cam ring, 9... Helicoid ring, IO... Connection pin, //...-Zoom gear, 12.
-Friction spring, 13... Forward/reverse rotation motor, /l
・-・Drive gear, S...changeover switch, T・
-・Tele terminal, W...-wide terminal, Tr/
, Tr/', Tru, Trλ'-) transistor, Ro...resistance for voltage extraction, ■o'...detection voltage, Vr...comparison voltage. Figure 2 Figure 3 Figure 4 Wharf Figure 5

Claims (1)

[Claims] t. An electric zoom device in which a moving element of a zooming stop is driven by a motor, comprising a detection means for detecting that the element has reached an end stop position by measuring a motor drive current value. An electric zoom device characterized by: 2. The electric zoom device according to claim 1, wherein the moving element is connected to the motor via a friction clutch. (5) The electric zoom device according to claim 1 or 2, wherein driving of the motor is stopped by a signal from the detection means. 4. The electric zoom device according to any one of claims 1 to 3, wherein a warning is displayed based on a signal from the detection means.