JP2887811B2 - Lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device used for a photographic lens of a video camera.

2. Description of the Related Art In recent years, the development of small video cameras that are convenient to take out and use outdoors has been actively developed. The driving device also needs to be downsized.

Hereinafter, a conventional lens driving device will be described with reference to the drawings.

FIG. 3 is a sectional view of a lens barrel including a conventional lens driving device. In FIG. 3, the outer frame of the lens barrel is the main body 1,
It comprises a third group frame 8 and a master flange 21. In FIG. 3, reference numeral 1 denotes a main body, and a lens constituting the objective lens group 5.
2, 3, and 4 are fixed at predetermined positions. Reference numeral 6 denotes a spacer between the lenses 3 and 4, and reference numeral 7 denotes a lens holding nut. 8 is the body 1
The lens 9 is fixed in the third group frame that is coupled to the lens. Reference numeral 10 denotes a guide pole provided so that both ends of the main unit 1 and the third group frame 8 are fitted to each other.
A moving frame 11 for a zoom lens holding 12, 13, and 14 can slide on the guide pole. Reference numeral 16 denotes a screw shaft provided at both ends between the main body 1 and the third group frame 8, and a screw shaft provided in parallel with the optical axis 17 and the guide pole 10, and the zoom lens moving frame 11 moves in the optical axis 17 direction. You can do it. Reference numeral 18 denotes a gear unit integrally fixed to one end of the screw shaft 16. Reference numeral 19 denotes a motor unit, which is fixed to the upper part of the main body 1. The shaft of the motor unit 19 is rotated by a control signal. The rotation rotates the screw shaft 16 and moves the zoom lens moving frame 11 in the direction of the optical axis 17. To move to. Reference numeral 20 denotes an iris portion for performing an aperture operation, reference numeral 21 denotes a master flange fixed to the third group frame 8, and reference numeral 22 denotes a master flange 21 and both ends fitted to the third group frame 8 so as to be parallel to the optical axis 17. Multiple guide poles,
Reference numeral 23 denotes a focus lens moving frame supported by the guide pole 22, and the focus lens moving frame 23 fixes lenses 24, 25, and 26 constituting a focus lens group 27.

28 is a focus motor, which is fixed to one of the outer sides of a mounting frame 28a for mounting the focus motor 28,
The bottom surface 28b of the mounting frame 28a is fixed outside the master flange 21. FIG. 5 shows the nut 30 in FIG.
FIG. 4 is an enlarged cross-sectional view in the direction of arrow A in a state where the focus lens and a focus lens moving frame 23 are engaged with each other. Hereinafter, description will be made with reference to FIG. Focus motor 28 screw shaft
29 meshes with a nut 30, and the lower end of the nut 30 is engaged with the upper end of the focus lens moving frame 23. The focus lens moving frame 23 has a hole in the center for the guide pole 22 to pass through.
The engaging portion 23a between the nut and the nut 30 is
The width of the nut 3 is smaller than that of the nut 30. The center of the bottom surface 28b of the mounting frame 28a and the center of the surface of the master flange 21 on which the bottom surface 28b of the mounting frame 28a is fixed are partially cut away in the optical axis 17 direction. The notched end surfaces on the bottom surface 28b of the mounting frame 28a serve to suppress the rotation of the focus lens moving frame 23 engaged with the nut 30. Therefore, when the screw shaft 29 of the focus motor 28 rotates, the focus lens moving frame 23 can move in the direction of the optical axis 17 integrally with the nut 30 meshed with the screw shaft 29. The lens barrel detects the amount of movement of the zoom lens moving frame 11 at the time of focusing, and a position detecting means (not shown) for transmitting a detection signal, and a control unit for processing the detection signal and transmitting a control signal (FIG. (Not shown).

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

When focusing, first focus lens group 27
Detects the position of the subject while constantly vibrating at a frequency of about 15 Hz, and the position detecting means sends a detection signal to the control unit. Next, the control unit processes the detection signal to determine the amount by which the zoom lens moving frame 11 having the zoom lens group 15 should move, and sends a control signal for the moving amount to the focus motor 28, This control signal causes the focus motor 28 to rotate. As a result, the screw shaft 29 rotates, and the focus lens moving frame 23 engaged with the nut 30 meshing with the screw shaft 29 moves in the direction of the optical axis 17 to complete the focusing.

Problems to be Solved by the Invention Incidentally, in the above-described conventional configuration, the focus lens moving frame 23 slides on the guide pole 22, so that especially when mass production is considered, the focus lens moving frame 23 and the guide pole
A certain clearance is required between 22. But,
The screw shaft 29 of the focus motor 28 rotates and the nut
If this clearance is too large when 30 slides in the direction of arrow A (the direction of the optical axis), especially in the above configuration where the position of the guide pole 22 and the position of the engaging portion 23a are separated, the fourth
The rotation of the focus lens moving frame 23 in the direction of arrow B as shown in the figure occurs instantaneously when the nut 30 is started. In other words, since the focus lens moving frame 23 is in a state where it only tilts and does not slide at the time of the start, a time occurs.
It is not possible to smoothly follow the movement of the nut 30. Therefore, a momentary defocus occurs when the nut 30 is started.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lens driving device that does not cause defocus when a nut is activated when focusing.

Means for Solving the Problems In order to solve the above-described problems, a lens driving device according to the present invention includes a master flange constituting a part of an outer frame of a lens barrel, and a guide supported by the master flange. A pole, a movable frame having a lens group provided by being fitted to the guide pole, a motor fixed to the master flange, a nut meshed with a screw shaft of the motor, An engaging portion provided on a nut for engaging the moving frame; and an elastic member for elastically locking the engaging portion and the moving frame with respect to the optical axis so as to restrict movement in the thrust direction and the radial direction. And the engaging portion has one surface abutting on the moving frame,
The other surface is pressed in the thrust direction by the elastic member.

Operation If the lens is driven in such a configuration, the nut and the moving frame are locked by the elastic member at the engaging portion between the nut and the moving frame, so that the screw shaft of the motor rotates and meshes with the screw shaft. When the moving nut engaged with the nut tries to slide on the guide pole, the rotating operation of the screw shaft is accurately transmitted to the moving frame via the nut. Therefore, instantaneous defocusing at the time of starting the nut can be prevented.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a lens barrel including the lens driving device of the present embodiment, and FIG. 2 is an enlarged view in which a state in which a nut 31 and a focus lens moving frame 33 are engaged in FIG. .

In FIG. 2, a part of the upper end of the focus lens moving frame 33 is largely cut downward, and a hole for passing the guide pole 22 is formed in the center of the cutout. A screw hole for engaging with the screw shaft 29 is formed in the center of the nut 31, and an engagement portion 31a extends downward from the center of the lower end of the nut 31. This engagement part 3
1a, one surface 31c of both lower end surfaces thereof is in contact with one surface of both end surfaces of the cutout portion of the focus lens moving frame 33. The other side of the notch 33
A part of the elastic member 34 contacts and is fixed to d. In a part of the elastic member 34 which does not contact the surface 33d of the cutout portion, the tip of this portion contacts the surface 31b of the engaging portion 31a. The surface 31b is constantly pressed in the direction of the surface 31d in contact therewith, and the engaging portion 31a is locked.

The operation of the lens driving device configured as described above will be described below. Since the focusing operation in this embodiment is the same as that of the conventional apparatus shown in FIGS. 3 and 4 except for the process of transmitting the rotation of the focus motor 28, the rotation of the focus motor 28 is transmitted. Only the process will be described below.

1 and 2, when the focus motor 28 rotates, the screw shaft 29 rotates and the nut 31 starts to slide in the optical axis direction. However, the engagement portion 31a and the focus lens moving frame 33 are elastic members. Since the nut 31 is pressed and locked, the rotation operation in the direction of arrow B as shown in FIG. 2 does not occur when the nut 31 is started. Therefore, the operation of the nut 31 is properly transmitted to the focus lens moving frame 33, and the focus lens moving frame 33 can smoothly follow the operation of the nut 31.

As described above, according to the present embodiment, the engagement portion 31 of the nut 31
Since a and the moving frame 33 for the focus lens are locked by the elastic member 34, the operation of the nut 31 is accurately transmitted to the moving frame 33 for the focus lens, and the moving frame 33 for the focus lens is moved to the operation of the nut 31. A smooth following operation can be performed.

In the present embodiment, the description has been made using a focus lens. However, the present invention is not limited to the focus lens, but may be applied to, for example, a zoom lens.

Effect of the Invention As described above, in the lens driving device of the present invention, since the engaging portion of the nut and the moving frame are pressed and locked by the elastic member, the operation of the nut is accurately transmitted to the moving frame and moved. The frame can smoothly follow the operation of the nut.

Therefore, the lens driving device of the present invention prevents instantaneous defocusing that occurs when the nut is started, and enables smooth and stable focusing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a lens mirror copper including a lens driving device according to an embodiment of the present invention, FIG. 2 is an enlarged view in which a nut and a focus lens moving frame in the embodiment are engaged, and FIG. FIG. 4 is a sectional view of a lens mirror copper including a conventional lens driving device, FIG. 4 is an enlarged view of a state in which a conventional nut and a focus lens moving frame are engaged, and FIG. FIG. 3 is an enlarged cross-sectional view in the direction of arrow A in a state where the moving frame for a focus lens is engaged. 1 ... body, 11 ... moving frame for zoom lens, 21 ... master flange, 22 ... guide pole, 28 ... focus motor, 29 ... screw shaft, 31 ... nut, 31a ...
Engagement part, 33: moving frame for focus lens, 34: elastic member.

Claims (1)

(57) [Claims] A master flange constituting a part of an outer frame of a lens barrel, a guide pole supported by the master flange, and a lens group provided to be movable by fitting to the guide pole. A moving frame having the motor fixed to the master flange, a nut meshed with a screw shaft of the motor, an engaging portion provided on the nut and engaging with the moving frame, and the engaging portion; The moving frame includes an elastic member that elastically locks with respect to the optical axis so as to restrict movement in the thrust direction and the radial direction, and one surface of the engaging portion abuts on the moving frame,
A lens driving device, wherein the other surface is pressed in a thrust direction by the elastic member.