JP2004078078A - Lens driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens driving device for securing minimum necessary lens operations by arranging a variable-speed mechanism in a power transmission mechanism between a motor and a movable lens, changing a speed ratio in the variable-speed mechanism in accordance with the inclination, etc., of a photographic lens (movable lens) to prevent an increase in motor torque, preventing an increase in power consumption for lens driving even when the photographic lens is tilted and preventing an unexpected things such as the movable lens does not move and a power source fails. <P>SOLUTION: A stepless variable-speed mechanism 28 is arranged in the power transmission mechanism 30 between the motor 22 and the movable lens 10. A control circuit 20 detects the inclination of the photographic lens (movable lens 10) from an inclination angel detection sensor 46 and changes the speed ratio of the stepless variable-speed mechanism 28 in accordance with the inclination. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lens driving device, and more particularly to a lens driving device that drives a large photographing lens for a television camera by a motor.
[0002]
[Prior art]
For example, a movable lens (group) such as a focus lens (group) for focusing and a zoom lens (group) for zooming is arranged in a photographing lens (EFP lens or the like) used for a television camera. A lens driving device is used to drive these movable lenses by motor. In general, a photographing lens for a television camera, particularly an EFP lens used in a studio, has a large diameter and weighs several kilograms alone for each movable lens (group), and these movable lenses (group) are driven by a motor. (JP-A-11-261873).
[0003]
On the other hand, in order to photograph an object placed on a ceiling, a floor, or the like, the photographing lens (television camera) may be largely tilted upward or downward. In such a case, a large load is applied to the motor to drive a movable lens such as a focus lens or a zoom lens. For this reason, conventionally, the movable current is moved against a large load by increasing the drive current supplied to the motor and increasing the torque of the motor as compared to when the taking lens is horizontal.
[0004]
[Problems to be solved by the invention]
However, when the drive current of the motor is increased as described above, the power consumption of the power supply increases, and when the remaining capacity of the power supply decreases, such as when using a battery, the lens does not operate at all, or in the worst case. In the case of (1), there is a possibility that the power supply goes down (the operation of the camera and the taking lens is completely stopped).
[0005]
On the other hand, when shooting with the shooting lens facing upward or downward, it is a special shooting situation.In such a situation, it is rare to change the focus or zoom greatly or operate at high speed. There is little need to move at speed.
[0006]
The present invention has been made in view of such circumstances, and when the shooting lens is greatly inclined, while preventing an increase in power consumption for driving the lens, the motor-driven movable lens does not operate, It is an object of the present invention to provide a lens driving device capable of preventing an unexpected situation such as a power failure and ensuring a minimum necessary lens operation.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a movable lens movable in an optical axis direction, a motor for generating power for driving the movable lens, and a motor for generating power for driving the movable lens. A power transmission mechanism for transmitting the driving power to the movable lens, wherein a part of the power transmission mechanism is formed, and a speed ratio between an operation speed of the motor and an operation speed of the movable lens. And a tilt mechanism in the optical axis direction of the movable lens as torque information related to the magnitude of the torque of the motor required to drive the movable lens, or supplied to the motor. Torque information detecting means for detecting the magnitude of the drive current; and changing the speed ratio of the transmission mechanism based on the torque information detected by the torque information detecting means. It is characterized by comprising: a speed ratio changing means for changing the magnitude of the torque of the motor required to drive's.
[0008]
According to a second aspect of the present invention, in the first aspect, a position detection sensor for detecting a position of the movable lens is engaged with a movable portion of the power transmission mechanism. The transmission mechanism is disposed on a power transmission path from the motor to the position detection sensor.
[0009]
According to a third aspect of the present invention, in the first aspect of the invention, the speed ratio changing means has a mode in which the speed ratio of the speed change mechanism is not changed under a predetermined condition. It is characterized by.
[0010]
According to the present invention, a speed change mechanism is disposed in a power transmission mechanism between a motor and a movable lens, and the speed ratio of the speed change mechanism is changed according to the inclination of a photographing lens (movable lens) or the like, so that the torque of the motor is changed. The power consumption for driving the lens is prevented from increasing even when the taking lens is tilted, and unexpected movements such as when the movable lens does not operate or the power supply goes down are prevented. Is prevented, and the minimum required lens operation is ensured.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a lens driving device according to the present invention will be described in detail with reference to the accompanying drawings.
[0012]
FIG. 1 is a diagram showing a schematic configuration of a lens driving device to which the present invention is applied. In FIG. 1, a movable lens 10 is, for example, a focus lens (group) for focusing provided in a lens barrel (fixed barrel 12) of a photographic lens (EFP lens or the like) used for a television camera, or a variable lens. A movable lens (group) such as a zoom lens (group) for magnification is shown, and the movable lens 10 is arranged so as to be movable in the optical axis direction of a photographing lens (movable lens 10). In the example shown in the present embodiment, the movable lens 10 is held by a lens holding frame 14, and a pin 16 protrudes from the lens holding frame 14. The pin 16 is engaged with the cam groove 18A of the cam cylinder 18 via the straight groove 12A of the fixed cylinder 12, and the movable lens 10 moves in the optical axis direction by rotating the cam cylinder 18. It has become.
[0013]
On the other hand, a command signal indicating a command value of the moving position or the moving speed of the movable lens 10 is given from, for example, a controller (not shown) to the control circuit 20 of FIG. According to the value, a control signal for controlling the rotation speed of the drive motor 22 (hereinafter, referred to as the motor 22) of the movable lens 10 is given to the motor drive circuit 24. When a command value for the moving position of the movable lens 10 is given to the control circuit 20, for example, a position signal indicating the current position of the movable lens 10 is acquired from a position detection sensor (potentiometer) 26 in FIG. A control signal for commanding an operation at a rotational speed corresponding to the difference between the current position and the current position is given to the motor drive circuit 24. The position detection sensor 26 in the figure is engaged with a gear 44 which is a movable part of a power transmission mechanism from the motor 22 to the movable lens 10, and detects the position of the movable lens 10 based on the rotation angle of the gear 44.
[0014]
The motor drive circuit 24 applies a drive voltage corresponding to the rotation speed of the control signal given from the control circuit 20 to the motor 22, and supplies a drive current corresponding to the torque generated by the motor 22 to the motor 22. As a result, the motor 22 rotates at the rotation speed indicated by the control signal. A power supply 25 such as a battery and a commercial power supply is connected to the motor drive circuit 24, and a drive voltage and a drive current for the motor 22 are obtained from the power supply 25.
[0015]
The motor 22 and the movable lens 10 are connected by a power transmission mechanism 30 including a gear, a continuously variable transmission mechanism 28, and the like in addition to the cam cylinder 18 described above. The output shaft rotates, and one conical belt wheel (original vehicle) 36A of the continuously variable transmission mechanism 28 rotates via the gears 32 and 34.
[0016]
Here, as shown in FIG. 2, the stepless speed change mechanism 28 has two conical conical belt wheels 36A and 36B arranged with their rotation axes parallel and opposite in direction. , 36B, an endless belt 38 is stretched. Thus, when the conical belt wheel 36A rotates as described above, the other conical belt wheel (slave) 36B rotates via the belt 38. A guide roller 40 is engaged with the belt 38. When the guide roller 40 is moved in the direction of the rotation axis by a motor (not shown), the belt 38 is moved in the direction of the rotation axis of the conical belt wheels 36A and 36B. It has become. Thereby, the rotation speed ratio between the conical belt wheel 36A and the conical belt wheel 36B is changed. The mechanism for changing the position of the belt 38 is shown as a belt driving unit 41 in FIG.
[0017]
In FIG. 1, when the motor 22 rotates and the conical belt wheel 36A of the continuously variable transmission mechanism 28 rotates as described above, the other conical belt wheel 36B of the continuously variable transmission mechanism 28 rotates, and via the gears 42 and 44. The cam cylinder 18 rotates. Thereby, the movable lens 10 moves in the optical axis direction.
[0018]
Also, at a predetermined position of the photographing lens, the inclination angle of the optical axis of the photographing lens (inclination from the horizontal direction in the vertical plane including the optical axis), that is, the inclination angle detection for detecting the inclination angle of the optical axis of the movable lens 10 A sensor 46 is provided, and an inclination angle detected by the inclination angle detection sensor 46 is provided to the control circuit 20.
[0019]
The control circuit 20 sends a control signal to the belt driving unit 41 based on the inclination angle given from the inclination angle detection sensor 46, controls the position of the guide roller 40 (see FIG. 2), and To control the speed ratio. For example, the speed ratio ((rotational speed of conical belt wheel 36B) / (rotational speed of conical belt wheel 36A)) of the stepless speed change mechanism 28 decreases as the inclination angle detected by the inclination angle detection sensor 46 increases. Then, the position of the belt 38 is changed by the belt driving unit 41 (the belt 38 is moved in a direction in which the diameter of the conical belt wheel 36A increases). As a result, the torque of the motor 22 required to move the movable lens 10 is reduced, and the increase in the drive current supplied to the motor 22 from the motor drive circuit 24 (power supply 25) is reduced.
[0020]
In the control of the position of the belt 38, for example, the inclination angle detected by the inclination angle detection sensor 46 is adjusted so that the torque of the motor 22 required to drive the movable lens 10 does not increase to a predetermined value or more. The position of the belt 38 is changed to a predetermined position.
[0021]
As described above, in the above-described embodiment, the speed ratio of the operating speed of the motor 22 and the movable lens 10 is changed by the stepless speed change mechanism 28 using the conical belt wheels 36A and 36B. The configuration of another transmission mechanism, such as a transmission mechanism using the same, may be used.
[0022]
Further, in the above embodiment, the inclination angle of the movable lens 10 is detected, and the speed ratio of the transmission mechanism is controlled based on the inclination angle. This is not necessarily the case. For example, the speed ratio of the speed change mechanism may be controlled so that the torque of the motor 22 required to drive the movable lens 10 does not exceed a certain value, and the value of the drive current supplied to the motor 22 is detected. The speed ratio of the transmission mechanism may be controlled so that the value of the drive current does not increase to a predetermined value or more. Further, the speed ratio of the transmission mechanism may be controlled so that the power consumption in consideration of the driving voltage does not increase to a predetermined value or more.
[0023]
Further, in the above-described embodiment, as a mechanism for driving the movable lens 10, the cam cylinder 18 is rotated by the motor 22 to move the movable lens 10 in the cam groove 18 </ b> A of the cam cylinder 18 to move the movable lens 10 in the optical axis direction. However, the present invention can be applied to a case where the power of the motor 22 is transmitted as a driving force in the optical axis direction of the movable lens 10 by another mechanism. In this case, it is preferable that the speed change mechanism is inserted and arranged in a position that does not affect the position detection of the movable lens 10, that is, in a power transmission path between the position detection sensor and the motor 22.
[0024]
In the above embodiment, the speed ratio of the speed change mechanism (the stepless speed change mechanism 28) is not always changed according to the inclination of the movable lens 10 or the like. (Predetermined position). For example, a switch is provided for the operator to determine whether or not to change the speed ratio of the speed change mechanism in accordance with the inclination of the movable lens 10 or the like. The speed ratio of the speed change mechanism may not be changed if the capacity is such that the movable lens 10 can be driven sufficiently without changing the speed ratio of the speed change mechanism.
[0025]
【The invention's effect】
As described above, according to the lens driving device of the present invention, the speed change mechanism is disposed in the power transmission mechanism between the motor and the movable lens, and the speed in the speed change mechanism is changed according to the inclination of the photographing lens (movable lens). By changing the ratio to prevent the motor torque from increasing, even when the photographing lens is tilted, the power consumption for driving the lens is prevented from increasing and the movable lens operates. This prevents an unexpected situation such as a missing or power-down, and ensures a minimum necessary lens operation.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a lens driving device to which the present invention is applied.
FIG. 2 is a schematic configuration diagram showing a main configuration of a continuously variable transmission mechanism.
[Explanation of symbols]
Reference Signs List 10 movable lens, 12 fixed cylinder, 18 cam cylinder, 20 control circuit, 22 motor, 24 motor drive circuit, 25 power supply, 28 stepless speed change mechanism, 30 power transmission mechanism, 36A, 36B ... conical belt wheel, 38 ... belt, 40 ... guide roller, 41 ... belt drive unit, 46 ... inclination angle detection sensor

Claims (3)

A movable lens movable in the optical axis direction, a motor for generating power for driving the movable lens, and a power transmission mechanism for transmitting the power of the motor to the movable lens as power for driving the movable lens. Lens drive device,
A transmission mechanism that forms a part of the power transmission mechanism and that varies a speed ratio between an operation speed of the motor and an operation speed of the movable lens;
Detecting the tilt angle of the movable lens in the optical axis direction or the magnitude of the drive current supplied to the motor as torque information related to the magnitude of the torque of the motor required to drive the movable lens. Torque information detecting means,
Speed ratio changing means for changing the speed ratio of the transmission mechanism based on the torque information detected by the torque information detecting means, and changing the magnitude of the torque of the motor required to drive the movable lens;
A lens driving device comprising: When a position detection sensor for detecting the position of the movable lens is engaged with a movable portion of the power transmission mechanism, the transmission mechanism is disposed on a power transmission path from the motor to the position detection sensor. The lens driving device according to claim 1, wherein 2. The lens driving device according to claim 1, wherein the speed ratio changing unit includes a mode in which the speed ratio of the transmission mechanism is not changed under a predetermined condition.

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