JPS62139508A - Focusing device for lens barrel - Google Patents

Abstract

PURPOSE:To perform focusing operation without rotating any lens by placing a focusing lens holder in linear motion along a shaft according to the rotation of a focusing ring. CONSTITUTION:A lens 10 is fixed to the focusing lens holder 1 by a lens fixing ring 11 and a slide pipe 12 is fixed to the focusing lens holder 1. Then, the focusing lens holder 1 is so built in so that it is freely slidable on the shaft 7 by the slide pipe 12 in optical-axis directions. A fixed lens barrel 4, on the other hand, is provided with a guide pin escape hole 14 and a guide pin 15 fixed to the focusing lens holder 1 engages a spiral cam groove 17 provided to the focusing ring 16 through the guide pin escape hole 14. Then, when focusing operation is performed, the focusing ring 16 is rotated and moved in the spiral cam groove 17 and the focusing holder 1 moves along the shaft 7 according to said movement, thereby making a focusing adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a focusing device for a lens barrel used in an optical device such as a camera.

2. Description of the Related Art FIG. 3 shows the configuration of a focusing mechanism in a conventional focusing device. In FIG. 3, lenses 2 and 3 are fixed to the focusing lens holder 1, and helicoids 5a are provided on the focusing lens holder 1 and the fixed lens barrel 4, respectively.
By engaging 5b, the focusing lens holder 1
is incorporated into the fixed lens barrel 4. The variable power lens holder 6 is slidably attached to a shaft 7 provided in the fixed lens barrel 4 in its axial direction. Further, a bin 9 provided in the variable power lens holder 6 is slidable in a spiral cam groove 8a provided in a cylindrical cam 8 rotatably incorporated along the inner surface of the fixed lens barrel 4. engaged. Therefore, by rotating the focusing lens holder 1, the focusing lens holder 1 rotates in the axial direction due to the engagement of the helicoids 5a and sb provided on the focusing lens holder 1 and the fixed lens barrel 4, respectively. It moves and comes into focus. Furthermore, by rotating the cylindrical cam 8 by means not shown,
The pin 9 moves along the cam groove 8a, and along with this movement, the variable power lens holder 9 moves along the shaft 7, and a variable power operation is performed.

Problems to be Solved by the Invention However, in the conventional focusing device using the helicoid 5, if the engagement accuracy with the helicoid 6b provided in the focusing lens holder 1 is maintained high, the focusing device can be The movement of the lens holder 1 was not smooth, and the helicoids SA and SB were assembled by fitting the helicoids SA and SB together, resulting in poor workability.

In addition, since the focusing lens holder 1 rotates, the lenses 2 and 3 rotate when the focus cell is set, so if the centering accuracy of the lenses 2 and 3 with respect to the optical axis is poor, the image of the subject will be distorted. The problem was that it rotated.

In view of the above-mentioned problems, the present invention provides a focusing device for a lens barrel that is inexpensive and capable of focusing by moving the lens straight in the optical axis direction without rotating it.

Means for Solving the Problems In order to solve the above problems, the focusing device of the present invention has a focusing lens holder slidably attached to a shaft provided in the optical axis direction of a fixed lens barrel. A guide pin provided on the focusing lens holder is engaged with a cam groove formed in a focusing ring provided on the fixed lens barrel so as to be rotatable about the optical axis of the fixed lens barrel. It was forced upon me.

Effects According to the present invention, by rotating the focusing ring, a moving force acts on the guide pin fitted into the cam groove provided in the focusing ring, and the focusing lens holder is configured as follows. It moves along a shaft provided in the optical axis direction of the fixed lens barrel.

Therefore, the focusing lens can be moved freely without having to rotate it.

EXAMPLE Hereinafter, a focusing device for a lens barrel according to an example of the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of a main part showing an embodiment of the present invention. In FIG. 1, a lens 10 is fixed to a focusing lens holder 1 by a lens fixing ring 11. As shown in FIG. A slide pipe 12 is fixed to this focusing lens holder 1. Reference numeral 7 denotes a shaft that is attached to the fixed lens barrel 4 by the fixing fittings 1sa and 13b, extending in the optical axis direction.The focusing lens holder 1 is mounted on the shaft 7 by the slide pipe 12 It is built in so that it can freely slide in the optical axis direction. 8 is a cylindrical cam rotatably provided on the inner surface of the fixed lens barrel 4.

The fixed lens barrel 4 is provided with a guide pin relief hole 14, and when the guide pin 16 fixed to the focusing lens holder 1 is provided in the focusing ring 16 through the guide pin relief hole 14, It is engaged with a helical cam groove 17. The focusing ring 16 is a focusing ring fixing fitting 1
8 is incorporated into the fixed lens barrel 4 so as to be rotatable about its optical axis, and its inner surface is provided with a spiral cam groove as shown in FIG.

A slide pipe 12 is fixed to each of the variable power lens holder 6 and the correction lens holder 19, and the lenses are slidably attached on the shaft 7 via the slide pipe 12. Each of these lens holders 6.19 is provided with a guide pin 9, which is engaged with a cam groove (not shown) of a cylindrical cam 8 rotatably incorporated inside the fixed lens barrel 4. are combined. Reference numeral 20 denotes a variable magnification ring rotatably provided along the outer periphery of the fixed lens barrel 4. The variable magnification ring 2o is inserted through a screw through an arcuate escape hole 21 provided in the fixed lens barrel 4. 22, the cylindrical cam 8Vc is connected to the cylindrical cam 8Vc, and by rotating the variable power ring 2o, the cylindrical cam 8 rotates, and the cam groove provided in the cylindrical cam 8 connects the variable power lens holder 6.
, a correction lens holder 19 moves along the shaft 7 and can change the magnification.

At the time of focusing, the spiral cam groove 17 is moved by rotating the focusing ring 16, and with this movement, the focusing holder 1 is moved along the shaft 7, and the focusing ring 16 is rotated. This allows adjustment. Furthermore, since this focusing operation moves a lightweight lens, the power required for focusing is small.

Effects of the Invention As described above, the present invention provides a method in which a focusing lens holder is slidably attached to a shaft installed in a fixed lens barrel in the direction of its optical axis, and is rotatably attached to the fixed lens barrel. By fitting the guide bin provided on the lens holder into the spiral cam groove of the focusing ring, even if the focusing ring rotates, the focusing lens holder, i.e., the lens can move straight and focus without rotating. Furthermore, since the lens does not rotate, even if the lens is misaligned with respect to the optical axis, the image of the subject can be focused without rotating. In addition, since the meshing precision achieved by helicoid processing and the assembly work of the helicoid based on actual assembly are not required, it is possible to realize a focusing device that is inexpensive and has good assembly workability, which is extremely advantageous in practice.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a focusing device for a lens barrel according to an embodiment of the present invention, Fig. 2 is a perspective view of a focusing ring in the same device, and Fig. 3 is a conventional lens barrel using a helicoid. FIG. 3 is a cross-sectional view of the focusing device of FIG. 1... Focusing lens holder, 4... Fixed lens barrel, 7... Shaft, 14... Guide bin relief hole, 15... Guide bin, 16・・・・・・
Focusing ring, 17...Cam groove, 18...
・Focusing ring fixing bracket.

Claims (2)

[Claims] (1) A shaft is provided inside the fixed lens barrel in the direction of its optical axis, and a guide pin is provided in the focusing lens holder that is slidably attached to the shaft, and
A focusing ring provided with a spiral cam groove is rotatably attached to the fixed lens barrel, the guide is engaged with the cam groove provided in the focusing ring, and the focusing ring is rotated. A focusing device for a lens barrel, characterized in that the focusing lens holder is moved linearly along the shaft in accordance with the rotation of the lens barrel. (2) The focusing holder is slidable in the optical axis direction at a position behind the variable power lens group, and the focusing holder shares a shaft with the variable power lens holder group. A focusing device for a lens barrel according to claim 1.