JPS606806Y2 - Inner reflection prevention device for zoom interchangeable lenses for cameras - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an antireflection device that can effectively prevent internal reflections during photographing in a zoom type interchangeable lens for a camera, particularly a long focal length lens.

Generally, in zoom-type interchangeable lenses for cameras, focusing is performed by moving the first lens group on the objective side in the optical axis direction, and zooming is performed by moving the second and third lens groups relatively. However, in a long focal length interchangeable lens, the amount of movement of the movable lens in the optical axis direction is large, and the distance between each lens is relatively long.

Therefore, the sliding surface inside the lens barrel into which the movable lens holding frame is fitted is smoothed and coated with lubricant.

For this reason, during photographing, the incident light causes internal reflection, which deteriorates depiction performance, and this effect is particularly noticeable when photographing against the light.

Up to now, there have been devices designed to prevent the reflection of incident light on the inner surface of the lens barrel, but not only are the configurations complicated, but the light shielding between the first lens group and the second lens group is limited to the second lens group. , the light shielding effect on the sliding surface of the third lens group is not sufficient, and ghosts are likely to be created on the image plane.

This idea was made to solve the above-mentioned drawbacks, and it has a simple structure in which a cylindrical light-shielding member is provided on the sliding surface of the movable lens in the lens barrel so as to move together with the lens holding frame.
It is characterized by being able to effectively prevent problems caused by internal reflection.

To explain the embodiment with reference to the drawings, in FIG.
A female helicoid 3 is engraved on the inner peripheral surface of the central portion 2, and a pin 6 is implanted in a part of the outer periphery of the rear end.
A helicoid ring 5 inserted into the front end of a fixed lens barrel 4 is screwed into the female helicoid 3, and a pin 6 at the rear end is fitted into a long groove 8 parallel to the optical axis of an operating ring 7.

Therefore, when the operating ring 7 is rotated, the front cylinder 1 rotates together with the operating ring 7 via the pin 6 that engages with the long groove 8, and the helicoid 3 moves back and forth in the optical axis direction to perform focusing. It will be done.

As shown in FIG. 2, two guide grooves 16, 17, front and rear, and a pin 21 are provided on a part of the peripheral wall of the front half of the fixed lens barrel 4, and a pin 21 is provided on the inside. The holding frames 10 and 11 holding L2 and the third lens archipelago are arranged to slide and rotate via a pair of working legs 12 and 13 facing each other with their positions shifted from each other, and one of these working legs Pins 14 and 15 implanted on 12 and 13 pass through guide grooves 16 and 17 in fixed lens barrel 4.

The rear end of the fixed lens barrel 4 serves as a mounting section 9 for the camera, and a diaphragm mechanism (not shown) is built in adjacent thereto.

A cam barrel 18 is slidably fitted onto the outer periphery of the front half of the fixed lens barrel 4, and the cam barrel 18 has front and rear arcuate cam grooves 19 inclined with respect to the optical axis, as shown in FIG. ,18
A straight groove 22 parallel to the optical axis is bored, the pin 14 of the holding frame 10 of the second lens group L2 engages with the front arcuate cam groove 19, and the rear arcuate cam groove 20 engages with the pin 14 of the holding frame 10 of the second lens group L2. The pin 15 of the holding frame 11 of the 3 lens groups engages, and the straight groove 2
2 is engaged with a pin 21 on the fixed lens barrel 4.

Further, a light-shielding tube 23 is rotatably fitted to the inner peripheral surface of the front half of the fixed lens barrel 4, and a collar 23a at the front end of the light-shielding tube 23 is engaged with the front end surface of the fixed lens barrel 4 and inside the helicoid ring 5. The inner peripheral surface of this light-shielding tube 23 is formed into a fine sawtooth-like rough surface 23b, and the operating leg 12 of the holding frame 10 of the second lens group fits into a part of the peripheral wall. A pair of elongated notches 24 are provided, and a pair of wide notches 25 are provided into which the operating legs 13 of the holding frame 11 of the third lens group can fit and allow rotation thereof and movement in the optical axis direction.

Although the operating ring 7 and the cam cylinder 18 rotate relative to each other due to the fitting relationship between the rail member 7a and the ring protrusion 18a, they move together in the optical axis direction.

Therefore, when the operating ring 7 is rotated, that is, during focusing, the pin 21 on the fixed lens barrel 4 engages with the straight edge 22 of the cam barrel 18, so the cam barrel 18 does not rotate and the operation is performed. Focusing is performed by rotating and sliding only the ring 7 as described above, and when the operation ring 7 is moved in the optical axis direction, the cam cylinder 18 also moves together, and the arcuate groove 19 of the cam cylinder 18 moves. Holding frame 1 via pins 14.15 that engage with ゜20
A zooming operation is performed by relatively moving lenses 0 and 11 in the optical axis direction while rotating.

By the way, in any of the above cases, the inner surface of the front half of the fixed lens barrel 4, that is, the second and third lens groups 1, 1, 3
Since the sliding surface of is covered with the light-shielding tube 23, the problem of internal reflection due to incident light does not occur.

In other words, in the case of a focusing operation, the first lens group L
□ moves forward and backward, and the second and third lens groups L2. Since L3 does not move at all, the light-shielding tube 23 also does not move and remains at a constant position.In addition, in the case of zooming operation, by moving the operation ring 7 in the optical axis direction, the second and second light-shielding tubes 18 are The holding frames 10 and 11 of the three lens groups L3 move in the optical axis direction while rotating, but one holding frame 10
Since the actuating leg 12 fits into the elongated notch 24 of the light-shielding tube 23, the light-shielding tube 23 is rotated together, but the actuating leg 12 slides inside the notch 24, and the light-shielding tube 23 is rotated. 23
is not moved in the optical axis direction, and since the operating leg 13 of the other holding frame 11 is fitted into the wide notch 25 of the light-shielding tube 23, it rotates and slides independently of the light-shielding tube 23. 23
has no effect on.

Therefore, the light-shielding tube 23 does not move in the optical axis direction even during a zooming operation, but maintains a constant position.

As described above, in this invention, the cam tube has front and rear arcuate cam grooves and a linear groove parallel to the optical axis on the outer periphery of the fixed lens barrel, which has two guide grooves and a pin that are inclined with respect to the optical axis on the front peripheral wall. The linear groove of the fixed lens barrel is engaged with the pin so that it slides, and the inner surface of the front half of the fixed lens barrel is provided with an elongated notch and a wide notch that are shifted in position in the circumferential direction. A light-shielding tube having a rough surface is rotatably fitted into the fixed lens barrel, and a holding frame for a second lens group having a plurality of actuating legs and a third lens group having a plurality of actuating legs are provided inside the fixed lens barrel. The holding frame of the second lens group is disposed facing each other with the positions of the operating legs shifted, and the operating leg of the second lens group is slidably engaged with the elongated notch of the light-shielding tube, and The pin is engaged with one guide groove of the fixed lens barrel and one arcuate cam groove of the cam barrel, and the operating leg of the third lens group is positioned in the wide notch of the light-shielding barrel to allow sliding and rotation. At the same time, the pin on the leg is engaged with the other guide groove of the fixed lens barrel and the other arcuate cam groove of the cam barrel, so that the optical axis direction and circular direction of the lens group are maintained not only during focusing operations but also during zooming operations. The light-shielding tube can be kept in a constant position regardless of its movement in the circumferential direction, and the lens sliding surface inside the lens barrel can be reliably covered by the light-shielding tube. Reflections are effectively prevented and the descriptive quality of photography is improved.Moreover, the troublesome markings on the inner surface of the lens barrel have been processed,
There is no need to attach complicated parts, and the light-shielding tube only needs to be fitted into the lens barrel, so the structure is simple and easy to manufacture.

[Brief explanation of drawings]

FIG. 1 is a half-cut side view of an embodiment of this invention. FIG. 2 is a partially exploded perspective view of the components. FIG. 3 is a sectional view taken along the line XX in FIG. 1. In the figure, 1...front barrel, 4...fixed lens barrel,
5... Helicoid ring, 7... Operation ring,
10, 11... Holding frame, 12, 13...
・Operation leg, 14, 15...Pin, 18...
...Cam tube, 23...Shading tube, 24...
・Elongated notch, 25... wide notch.

Claims (1)

[Scope of utility model registration request] Two guide grooves 16 inclined with respect to the optical axis on the peripheral wall of the front half,
17 and a pin 21, a cam barrel 18 having front and rear arcuate cam grooves 19, 20 and a straight groove 22 parallel to the optical axis is engaged with the pin 21 with its straight groove 22. The fixed lens barrel 4 is fitted in a sliding manner, and the inner surface of the front half of the fixed lens barrel 4 has an elongated notch 24 and a wide notch 25 that are shifted in position in the circumferential direction. 2
3 are rotatably fitted together, and inside the fixed lens barrel 4 there is a holding frame 10 for the second lens group L2 having a plurality of working legs 12 and a third lens group having a plurality of working legs 13. The holding frame 11 of the second lens group L2 is arranged so as to face each other with the positions of the operating legs 12 and 13 shifted, and the operating leg 12 of the second lens group L2 is slidably engaged with the elongated notch 24 of the light-shielding tube 23. At the same time, the pin 14 on the leg is engaged with the guide groove 16 on one side of the fixed lens barrel 4 and the arcuate cam groove 19 on one side of the cam barrel 18, and the operating leg 13 of the third lens group L3 is attached to the light shielding barrel 23. The pin 15 on the leg is positioned in the wide notch 25 of the fixed lens barrel 4 to allow sliding and rotation.
0 and the other arcuate cam groove 20 of a cam barrel 18.