JPH09127398A - Lens driving mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of components and assembly man-hours and to reduce cost by arranging spring materials between a moving lens part and both fixed lens parts and controlling the movement of the moving lens part by heating or cooling the spring material. SOLUTION: The moving lens part 2 in a lens barrel part 1 is guided by two guide bars 7, and a shape memory alloy spring or a bias spring 8 made of ordinary material is arranged on one side in the moving direction of the lens part 2 and the shape memory alloy spring 9 is arranged on the other side. By cooling or heating the springs 8 and 9, the lens part 2 is moved in a direction shown by an arrow due to the redeformation or the recovery of the springs 8 and 9. Then, a position meter 11 is engaged with a moving lens frame and always detects the position of the moving lens so as to set it at a set focus position, or calculates the focus position so as to perform autofocusing operation at the calculated position. In the case the number of positions where the lens should be moved is one, for example, a bifocal lens, the position meter need not be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving mechanism for adjusting the focal point and varying the magnification of an optical system of a silver halide camera, a still video camera, a video movie camera, and a copying machine.

[0002]

2. Description of the Related Art It is necessary to drive a lens in the optical axis direction in order to adjust the focal point of an optical system of a silver salt camera, a still video camera, a video movie, etc. and an optical system of a copying machine. As a means, a drive source such as an electromagnetic motor and an ultrasonic motor, and a mechanical portion such as a gear, a cam and a lead screw have been used.

For example, in focus adjustment, a focus lens is driven by a multi-threaded screw portion such as a helicoid by an electromagnetic motor via a gear or the like. Some inner-focus type zoom lenses have a focus lens driven by a lead screw and an electromagnetic motor via a belt or a gear, or a motor shaft driven by a nut screw as a lead screw (special feature). Kaihei 1-93712
No.).

Further, also for zooming, lens driving is performed by engaging a variator lens with a cam groove of a cam ring and rotating the cam ring by a motor through a gear or the like. In some cases, the lead screw method is used.

[0005]

However, in the above case, expensive motors, power trains such as gear trains, cams, belts, lead screws, etc. are required, resulting in an increase in cost. In addition, since the power transmission member must be arranged to drive the lens, the structure of the device is complicated and space is required, the lens barrel is complicated and large, and the motor part is a mirror. It protrudes from the body. Further, since the number of members is large and the structure is complicated, the number of assembling steps is increased and the skill of assembling is also required, which causes a problem of cost increase.

An object of the present invention is to solve such a problem,
It is to provide a lens driving mechanism having a simple structure.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a lens provided with a movable lens portion, which is supported by a guide bar in the lens barrel and moves between fixed lens portions on both sides of the lens barrel. In the drive mechanism, a spring member is arranged between the movable lens unit and both fixed lens units, at least one of the spring members is a shape memory alloy, and the moving lens unit is heated or cooled to heat the movable lens unit. Configured to control movement.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a shape memory alloy is used as a lens driving means.

Shape memory alloys, regardless of elastic strain or plastic strain,
It is a metal that has the property of recovering to its original state of zero strain and deformation in a certain temperature range regardless of any deformation and strain. That is, it is a metal that has a property as if it remembers the metal shape when the strain deformation is zero. Shape memory effect (SME: SHAP)
E MEMORY EFFECT). And this metal is SMA (SHAPE MEMORY ALLO
Y). As the SMA used here, a titanium-nickel alloy system is used, which requires repeated movements of deformation and recovery for a long time and has good durability against fatigue and the like. Further, the SMA for the actuator is constructed by using a reversible type or an irreversible type.

In the lens driving mechanism of the present invention, the spring-shaped SMA member is attached to the moving lens frame fitted in the moving guide bar from the fixed end in the lens barrel, and the SMA member is heated by Joule heat by directly energizing. To transform it. This control is performed by PWM (pulse width modulation) energization.

Then, a position meter is engaged with the movable lens frame to constantly detect the position of the movable lens and set it at a set focus position, or index the focus position to perform an autofocus operation at that position.

A cross section of a typical principle structure of the lens driving mechanism of the present invention is shown in FIGS. Two cases can be considered depending on the method of re-transformation.

In FIG. 1, the re-deformation is performed by a bias spring made of a general spring material. In the lens barrel portion 1, a movable lens portion 2 is composed of a bias spring 3 made of a normal material and a shape memory alloy spring 4. I support you. The spring 4 can be moved to the right in the figure by heating it, and can be moved to the left by cooling the spring 4.

FIG. 2 shows a system in which two SMA springs 5 and 6 are heated and cooled to alternately re-deform one of the SMAs by utilizing the SMA recovery force. By moving the spring 5 and heating the spring 6, the moving lens unit 2 moves leftward, and by heating the spring 5 and cooling the spring 6, the moving lens unit 2 moves rightward.

[0015]

Embodiments FIGS. 3 to 5 show an embodiment of a lens driving mechanism of the present invention. 3 and 4 are explanatory views showing the internal structure of the lens driving mechanism. In the embodiment of FIG. 3, the movable lens portion 2 in the lens barrel portion 1 is guided by two guide bars 7, and a shape memory alloy spring or a bias spring 8 made of a common material is provided in one of the moving directions of the movable lens portion 2. The shape memory alloy spring 9 is arranged on the other side, and the moving lens unit 2 moves in the direction of the arrow by re-deforming or recovering the springs 8 and 9 by cooling and heating the springs 8 and 9. A position meter 11 measures the position of the moving lens unit 2.

If there is only one position to move the lens, such as a bifocal lens, no position meter or the like may be provided and the lens may be mechanically abutted to position the lens. Furthermore, even if the magnification rate is set to several, such as in a copying machine, the position may be judged by a position meter for control, or mechanically, a stopper or the like may be moved in and out at each magnification rate to change the magnification. You may move it.

[0017]

EFFECT OF THE INVENTION Since the drive source is spring-like and easily expands and contracts when energized, it can be easily controlled.
Moreover, since motors and drive transmission members are not required, the number of parts and the number of assembling steps are reduced, and the cost can be reduced. There are also fewer lens barrel parts. The lens barrel structure is extremely simple and compact, which provides space advantages. It can also be integrated into most lens barrels. In addition, since a protrusion such as a motor cannot be formed, the weight is extremely light. Since no motors are used, no electromagnetic noise is generated, and no mechanical noise is generated because no gear is used. Since it has a spring shape, the movable lens frame is constantly pressurized so that there is no backlash. Therefore, accurate control can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the principle of a lens driving mechanism of the present invention.

FIG. 2 is a sectional view showing the principle of the lens driving mechanism of the present invention.

FIG. 3 is an explanatory view showing an embodiment of a lens driving mechanism of the present invention.

FIG. 4 is an explanatory view showing another embodiment of the lens driving mechanism of the present invention.

FIG. 5 is a circuit block diagram using two SMA springs.

[Explanation of symbols]

 1 Lens barrel 2 Moving lens part 3-6 Spring 7 Guide bar 8, 9 Spring 10 Fixed lens part 11 Position meter 12 CPU 13 Operation system input circuit 14 Lens drive control circuit SMA (1), SMA (2) Shape memory spring

Claims (1)

[Claims] 1. A lens driving mechanism comprising a movable lens part supported by a guide bar in the lens barrel and moving between fixed lens parts on both sides of the lens barrel, wherein a spring is provided between the movable lens part and both fixed lens parts. A lens driving mechanism, wherein materials are arranged, at least one of the spring materials is a shape memory alloy, and the movement of the movable lens unit is controlled by heating or cooling the spring material.