JPS6242248B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal reflection prevention device for a zoom lens, and in particular, uses movement of a movable lens system to make an antireflection wall movable to cut harmful internal reflection light when a long focal length system is set. The present invention relates to an internal reflection prevention device for a zoom lens that allows clear images to be obtained even when the aperture is wide open.

In zoom lenses that include a movable variable power lens and a movable correction lens in the lens system that constitutes the optical system of the zoom lens, the movable variable power lens is close to the objective lens when set to a short focus system. Since the movable variable magnification lens is placed in a long focal length system, the movable variable magnification lens moves backward, so there is a long area between the objective lens and the movable variable magnification lens. As a result, the external light that enters through the objective lens is reflected on the inner surface of the lens barrel.
This creates flare, which significantly reduces lens performance, especially when the aperture is wide open.

In view of the above, various antireflection measures have been proposed in the past.

For example, as shown in Japanese Utility Model Application Publication No. 49-136229, a screen-like spiral plate that expands and contracts in conjunction with the movement of the variable magnification lens is arranged on the sliding guide surface exposed by the movement of the variable magnification lens. This spiral plate is designed to cut out harmful reflected light (A),
As seen in Japanese Utility Model Publication No. 51-31649, the holding frame of the movable lens is slidably fitted into the guide cylinder,
The sliding surface of the guide tube is covered with a light shielding body having an anti-reflection function to cut out harmful light (B), as shown in Japanese Utility Model Application Publication No. 138741/1983, a movable lens is A light-shielding tube that extends forward from the support tube and moves relatively in the optical axis direction is attached to the support tube to cut out harmful light (C).
Furthermore, as seen in Japanese Utility Model Application Publication No. 53-54656, in addition to the cam groove for zoom movement, another cam groove is provided on the inner surface of the cam cylinder for zoom operation, and another cam groove is provided in parallel with this cam groove, and the pin of the light-shielding ring is attached to this cam groove. There is a model (D) that fits together and moves the light-shielding ring according to zooming to cut out harmful light.

However, in the case of using a spiral plate as in (A) above, it is necessary to separately provide a cam groove and a pin to engage with the cam groove for moving the frame of the spiral plate, and also in (B). In this case, since a cylindrical light shielding body is used, the area of anti-reflection treatment applied to the inner surface of the cylinder becomes significantly large, and it is necessary to provide relief grooves in the cylindrical light shielding body.As a result, manufacturing is extremely troublesome and costly. Moreover, in (B), the movable frame has a double structure, which occupies a large space within the lens barrel, which is not preferable. Furthermore, in the case of (C), when the movable lens moves forward and has a short focus, the effective diameter becomes smaller, and in (D), a special lens is required to move the light shielding ring as in (A) above. This requires the installation of a cam groove and a pin that engages with the cam groove, and since the sliding portion of the movable lens frame is short in the optical axis direction, there are problems such as tilting.

In view of this, the present invention effectively eliminates the drawbacks of the above-mentioned conventional devices, has a simple structure, and reliably cuts out harmful reflected light when setting a long focal length, prevents the generation of flare, and provides clear images. The object of this invention is to provide an internal reflection prevention device for a zoom lens that can be formed on a film.

In order to achieve the above object, in the present invention,
In a zoom lens having a movable lens for variable power and a movable lens for correction between a focusing lens and a fixed lens, a lens located between the focusing lens and the movable lens for variable power and on the inner circumferential surface of the lens barrel. an annular light-shielding wall movable along the optical axis, and a leg extending from the light-shielding wall backward in the optical axis direction beyond the variable magnification movable lens is attached to the lens frame of the movable correction lens. When the long focal point is set, the light shielding wall is located between the focusing lens and the variable magnification movable lens to cut out harmful light reflected on the inner surface of the lens barrel, and when the short focal length is set, the light shielding wall is located directly behind the focusing lens. It is located so that it does not block the incident light.

The present invention will be described below with reference to embodiments shown in the drawings.

The zoom lens targeted by the present invention has a focus ring (not shown), as shown in FIG. 1 when the long focus is set and FIG. 2 when the short focus is set.
A variable magnification movable lens 4 and a movable correction lens 5 are provided movably in the optical axis direction between a focusing lens 1 supported by a fixed lens barrel 2 and a fixed lens 3 supported by a fixed lens barrel 2. It has a zoom lens system, and the variable magnification movable lens 4 and the movable correction lens 5 have pins 6 and 7 implanted in the lens frames 4a and 5a, and cam grooves 9 formed in the fixed lens barrel 2, 10, and by the zooming operation, the variable magnification movable lens 4 recedes linearly from a short focal point to a long focal point as shown in the trajectory A shown in FIG. 4, and the movable correction lens 5 Trajectory B shown in the same figure
As shown in the figure, it moves backward from the short focal point to the long focal point in almost the same way as the variable magnification movable lens 4, and moves slightly forward before reaching the longest focal point, and at the longest focal point it moves back by a distance L than at the shortest focal point. It was designed to remain in place.

In the present invention, the above-mentioned movable correction lens 5
Focusing on the movement of the movable correction lens 5, the light-shielding wall 11 is supported by the lens frame 5a of the movable correction lens 5, and in conjunction with the movement of the movable correction lens 5, the light-shielding wall 11 is positioned at a position where it blocks internally reflected light when the movable correction lens 5 is at a long focal point. , and are configured to be positioned at positions that do not obstruct the incident light when the focus is short.

The light-shielding wall 11 has an annular shape placed along the inner periphery of the fixed lens barrel 2, and has a plurality of pieces (three in the embodiment) extending rearward from the outer periphery of the light-shielding wall 11.
Engagement parts 12a, 12a, 12a, which are formed by bending the rear ends of the leg parts 12, 12, 12 toward the center, fit into engagement grooves 13 formed in the circumferential direction on the outer periphery of the front end of the lens frame 5a of the movable correction lens 5. The light shielding wall 11 is attached so as to be moved in the optical axis direction together with the movable correction lens 5 when engaged.

Note that since the variable magnification movable lens 4 and the movable correction lens 5 approach each other during long focal length, the lens frames 4a and 5a can be slidably engaged with each other as shown in FIG. ing. That is, a plurality of (three in the figure) protruding pieces 4b, 4b, .
Grooves 4c and 5c are formed between each of the grooves 4c and 5c, into which the opposing protrusions 4b and 5b are slidably fitted. Therefore, the leg portion 1 of the light shielding wall 11
The engagement groove 13 with which the second engagement portion 12a engages is formed on the outer surface of the tip portion of the protruding piece 5b of the lens frame 5a of the movable correction lens 5.

Since the present invention has the above configuration, the zoom operation ring 8
When the lens is rotated in the long focal point direction for zooming, the variable magnification movable lens 4 and the movable correction lens 5 are moved by pins 6, which engage with cam grooves 9, 10 of the zoom operation ring 8.
7, and reaches the most retracted position as shown in FIG. 1 at the longest focal point.

At this time, due to the backward movement of the movable correction lens 5, the light shielding wall 11 attached to the lens frame 5a of this lens also moves backward, allowing only the photographing light beam incident from the focusing lens 1 to pass through and being reflected on the inner surface of the lens barrel. The light reflected in the 4 directions of the variable magnification movable lens is blocked by the light shielding wall 1.
1 to the cutting position.

When the zoom operation ring 8 is rotated in the short focus direction, the variable magnification movable lens 4 and the movable correction lens 5 advance to predetermined positions as shown in FIG. 2, and when the movable correction lens 5 is at its shortest focus, The light shielding wall 11 is located behind the outer periphery of the focusing lens 1,
The photographing light beam entering the variable magnification movable lens 4 is not obstructed.

In this way, in the present invention, the light-shielding wall that cuts off the reflected light reflected by the inner surface of the lens barrel is supported by the lens frame of the movable correction lens that moves backward when the focus is long and moves forward when the focus is short. Fourth
It advances and retreats along the same trajectory C as the movable correction lens shown in the figure, effectively cutting off internal reflections caused by the inner surface of the lens barrel between the focusing lens and the variable magnification lens during long focal lengths, and at short focal lengths. Since it is located directly after the focusing lens and does not obstruct the incident light flux, it is possible to block internally reflected light only at long focal points, where internal reflections are particularly high, and it does not limit the effective aperture at short focal points. Moreover, it does not interfere with the movement of the variable magnification movable lens. Further, according to the present invention, since the light shielding wall utilizes the movement of the movable correction lens, there is no need for extra processing or materials such as installing a pin that engages a special cam groove, and this reduces costs. Various excellent effects can be obtained, such as being able to be carried out without raising the amount of water.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an outline of a zoom lens to which the present invention is applied, when the zoom lens is set to a long focus, Fig. 2 is a cross-sectional view when the zoom lens is set to a short focus, Fig. 3 is an exploded perspective view, and Fig. 4 is a movable zoom lens. FIG. 1... Focusing lens, 2... Fixed lens barrel, 3... Fixed lens, 4... Movable lens for variable magnification, 5... Movable lens for correction, 6, 7... Pin,
8...Zoom operation ring, 9, 10...Cam groove, 11
... light shielding wall, 12 ... leg part, 12a ... engagement part,
13...Engagement groove.

Claims (1)

[Claims] 1. In a zoom lens having a movable lens for variable power and a movable lens for correction between a focusing lens and a fixed lens, a lens located between the focusing lens and the movable variable power lens along the inner surface of the lens barrel. a ring-shaped light-shielding wall movable in the optical axis direction, and a leg extending from the focusing wall backward in the optical axis direction beyond the magnification variable movable lens is attached to the lens frame of the correction movable lens. Internal anti-reflection device in lenses.