JPH03294812A - Lens moving device - Google Patents

Abstract

PURPOSE:To use a motor with low torque and to prevent hysteresis from being generated in focusing operation by providing a pressing means which presses a racking member against a driving shaft. CONSTITUTION:The racking part 27 which is made of resin and has nearly the same pitch as the screw pitch of a driving shaft 21 is fixed atop of a leaf spring 28 and pressed against the driving shaft 21 by the leaf spring 28 from one side. On the side of the racking member 27, an abutting part 29 which abuts on the screw part of the driving shaft 21 is provided integrally with the racking part 27 and pressed against the driving shaft 21 by the leaf spring 28. Thus, the small-sized racking member 27 is pressed against the driving shaft 21 of the stepping motor from one side and a lens is driven by the racking member 27 to reduce the load on the stepping motor. Consequently, the low- torque motor is usable and the hysteresis is prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a lens moving device for a video camera, an electronic still camera, etc., in which a rack member connected to a lens is moved linearly by rotation of a drive shaft to perform automatic focus adjustment. Regarding.

2. Description of the Related Art In general, the basic configuration of a photographing lens system in a video camera or the like is comprised of a front lens group (2008), an Okashite lens group (2008), a compensator lens group, a variator lens group, and a master lens group. A method for adjusting the focus of a video camera equipped with such a photographic lens system is to slightly vibrate the master lens group in the photographic lens system using a ceramic actuator, etc., and measure the high-frequency component level of the signal obtained from the image sensor. According to the National Technical Report, a method is used that detects the front focus and rear focus by using a method, and feeds it back to the lens drive system to adjust the position of the front lens group so that the image is sharpest.
31, No. 6, 1958, pp. 65-67).

Recently, a device that can perform both optical path length microvibration and focusing has been proposed (see Japanese Patent Laid-Open No. 1-265215), and focusing has come to be done by moving lenses other than the front lens, such as a mass lens. There is. Below, the fourth section regarding the configuration of such a conventional lens moving device will be explained.
This will be explained with reference to the figures. As shown in the figure, an outer cylinder 1 holds an inner cylinder 3 to which a master lens group 2 is fixed so as to be slidable in the optical axis direction, and a ball bearing 4 is inserted between the outer cylinder 1 and the inner cylinder 3. has been done. A drive shaft 6 provided in the stepping motor 5 has its tip held by a guide plate 7 for steadying, and a movable piece 8 screwed onto the drive shaft 6 and the inner cylinder 3 are connected by an arm 9. With the above configuration, the moving piece 8 moves linearly as the stepping motor 5 rotates, and the master lens group 2 fixed to the inner cylinder 3 moves in the optical axis direction to focus on the subject.

Problems to be Solved by the Invention However, in the above configuration, it is necessary to apply grease or the like to the threaded portion in order to improve the slidability between the drive shaft 6 and the movable piece 8. Since the stepping motor is in contact with the drive shaft 6, the load on the stepping motor increases due to the viscosity of the grease, and the temperature characteristics at low temperatures also deteriorate, so a high torque motor is required, which is an important factor for video cameras used outdoors. There was a problem that a certain amount of power consumption per weight and volume increased. Additionally, a clearance is required between the drive shaft 6 and the movable piece 8 for sliding, and this clearance causes hysteresis in the movement of the master lens group with respect to the rotation of the stepping motor, resulting in a change in the rotation angle of the stepping motor. Correspondingly, there was also the problem that the lens did not operate accurately, resulting in unstable focusing operation.

The present invention solves the above problems, and aims to provide a lens moving device that can use a low-torque motor and can prevent hysteresis during focusing.

Means for Solving the Problems In order to achieve the above object, the present invention presses the drive shaft of a stepping motor from one side with a rack member having a pitch that is almost the same as the thread pitch of the drive shaft, and guides the stepping motor by this rack member. A lens frame that slides on the top is driven to move the lens on the optical axis.

Function: With the above-described configuration, the present invention presses the small rack member against the drive shaft from one side, so the contact area between the feed screw portion of the drive shaft and the threaded portion of the rack member can be reduced, and grease can be reduced. It is possible to prevent an increase in load due to viscosity. In addition, even if the rack member combined with the lens frame is pressed against the drive shaft and the rack member receives force as a reaction, the lens frame is structured to slide on the guide in the optical axis direction, so the lens Never exercise outside of this. Furthermore, since the rack member is pressed, the threaded part of the rack member and the threaded part of the feed screw part of the drive shaft always mesh with each other without any gaps, and even if the drive shaft repeats forward and reverse rotations, the gap between the gears will cause The so-called backlash that occurs is suppressed to a minimum.

Embodiment Hereinafter, a lens moving device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In FIGS. 1 and 2, focusing lenses 11 and 12 are fixed to a lens frame 13 made of resin by heat caulking or the like. Two guide balls 15 and 16 are provided inside the fixed lens barrel 14, and when the holes 13a and 13b at one end of the lens frame 13 slidably engage with the guide balls 16, the focusing lens 11 and 12 are movably guided in the direction of the optical axis 17. A rack unit 18 (details will be described later) is fixed to the lens frame 13 with screws 19, and the tip of the rack unit 18 is engaged with a drive shaft 21 of a stepping motor 20. Grease (not shown) is applied to the surface of the threaded portion of the drive shaft 21. Drive shaft 21 (: engaged. The drive shaft 21 is held by a metal bearing 22 of the stepping motor 20 and a thrust hair ring 24 provided on the kite board 23. By biasing the drive shaft 21 in the direction of the thrust bearing 24 by a plate spring (not shown), rattling of the drive shaft 21 in the thrust direction is prevented. It is fixed to the fixed lens barrel 14 with screws 25 and 26.

Next, details of the rack unit 18 will be explained. Third
In the figure, a rack part 27 made of resin having approximately the same thread pitch as the thread pitch of the drive shaft 21 is fixed to the tip of a plate spring 28, and the rack part 27 is attached to the drive shaft 21 from one side by the plate spring 28. Being pressed. On the rack part 27 side,
The contact portion 29 that comes into contact with the threaded portion of the drive shaft 21 is also connected to the rack portion 2.
7, and the plate spring 28 connects the drive shaft 2.
It is pressed to 1. The reinforcing plate 30 is provided with positioning holes 31 and 32 as shown in FIG.
It is inserted into the protrusions 33 and 34 of No. 3.

The operation of the lens moving device configured as described above will be described below.

The stepping motor 20 is configured to rotate 9 degrees per pulse, and the thread pitch of the drive shaft 21 is 0.
Since it is set to 4+m, the stepping motor 20
When rotates by one pulse, the drive shaft 21 rotates by 9 degrees, the rack portion 27 engaged with the drive shaft 21 moves by 10 μm, and the rack portion 27 is integrally fixed to the lens frame 13 by the plate spring 28. Therefore, the focusing lenses 11 and 12 are also aligned with the optical axis 1.
Move 10 μm in the direction of 7. stepping motor 20
By rotating forward and backward, the focusing lens 11.1
2 can also move back and forth to perform focusing operations.

As described above, according to this embodiment, by pressing a small rack member against the drive shaft of the stepping motor from one side and driving the lens by this rack member, the load on the stepping motor is reduced, and the low-torque motor Therefore, it is possible to provide a lens moving device that can be used and prevent the occurrence of hysteresis.

In the embodiment, a stepping motor was used as the drive motor, but a brushless DC motor or the like may also be used.

Effects of the Invention As is clear from the above embodiments, according to the present invention, since the contact area between the feed screw portion of the drive shaft and the rack member is reduced, it is possible to prevent an increase in load due to the viscosity of the grease. It is possible to use a low-torque motor, resulting in lower power consumption, smaller size, and lighter weight. In addition, since the rack member is pressed against the feed screw part of the drive shaft, the thread part of the rack member and the thread part of the feed screw part of the drive shaft always mesh with each other without any gaps, so that so-called play does not occur, and therefore the motor rotation It is possible to provide a small and lightweight lens moving device for a video camera, etc., which has low power consumption, can reduce the hysteresis of the movement of the lens frame relative to the lens frame, and can accurately perform focusing operations.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts showing the configuration of a lens moving device according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the main parts of the device, and FIG. 3 is a diagram showing the drive shaft and rack unit of the same device. FIG. 4 is a plan view of the main part showing the engaged state, and a sectional view of the main part of a conventional lens moving device. 11.12 Focusing lens (lens), 15.46...
... Guide ball (guide means), 18 ... Rack unit, 20 ... Stepping motor (
motor), 21...drive shaft, 27...
Rack part (rack member), 28... leaf spring (pressing means).

Claims (1)

[Claims] A lens frame that holds a lens, a guide means for guiding the lens frame in the optical axis direction, a drive shaft having a feed screw portion, a motor that drives the drive shaft, and a thread pitch of the drive shaft. A lens moving device comprising rack members having the same pitch and a coupling means for coupling the rack member and the lens frame, the lens moving device comprising a pressing means for pressing the rack member against the drive shaft. .