JPS615216A - Cam ring of zoom lens - Google Patents

Abstract

PURPOSE:To perform smoothly the zooming operation by providing a groove part, to which a cam follower should be attached, in a part other than the zoom operation area of a cam groove and the macro photographic area. CONSTITUTION:A cam ring 8 provided on a zoom lens barrel is provided with a cam groove 1 for a magnification varying lens group holding member which is engaged with the cam follower and moves it in the direction of the optical axis and a cam groove 2 for correcting lens holding member. Cam grooves 1 and 2 consist of macro photographic areas 1a and 2a, zoom photographic areas 1b and 2b, and cam follower attaching areas 1c and 2c respectively. The cam follower is attached in cam follower attaching areas 1c and 2c.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a mechanism for zooming a zoom lens barrel, and particularly to a cam ring having a cam groove for achieving zoom photography and macro photography. It is.

[Background of the invention]

A zoom lens generally has a lens group for changing magnification that is moved. By utilizing the movement of the lens groups by this cam ring, we created a cam groove area where one lens group is stopped and only the other lens group is moved, allowing for macro photography in addition to zooming. Are known.

A device in which the cam grooves for the zooming shooting area and the macro shooting area are continuously provided is, for example, disclosed in Utility Model Publication No. 51-628.
No. 30. A cam ring with such cam grooves is usually a thin cylinder with two spiral cam grooves for moving members that hold two lens groups in a predetermined relationship in the optical axis direction. It is being And conversion.

Due to requirements such as ease of processing, it is usually made of aluminum. Cam followers attached to holding members that hold the variable power and correction lens groups are fitted into the cam grooves to press the lens groups to position them at predetermined positions. To ensure optical performance, the clearance between this cam groove and cam follower is 0.015~0.
, oa.

It is necessary to keep it to no more than a nod. Furthermore, in order to perform zooming operations smoothly, the cam follower must move smoothly along the cam groove. Therefore, there should be no scratches, cracks, etc. on the cam groove.

However, when attaching the cam follower to the holding member, as mentioned above (because the clearance between the cam groove and the cam follower is very small, the cam groove may be damaged by the cam 7 lower itself, or the cam follower mounting jig may come into contact with the cam groove). This may damage the cam groove.Also, since the holding member is not prevented from moving in the optical axis direction, the holding member may move in the optical axis direction during the cam follower assembly work, causing the cam to become unstable. As follower installation is carried out,
This promotes damage caused by the cam groove jig and the cam 7 lower. If the cam groove is scratched, the cam follower will come into contact with the scratch, making it impossible to obtain smooth operability.

Regarding conventional cam rings, even in the above-mentioned known examples, no structure is shown that takes into account the work of attaching such a cam follower to a lens holding member.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cam ring that can achieve smooth zooming operations without the risk of causing the above-mentioned click phenomenon.

[Summary of the invention]

In order to achieve the above object, in the present invention, the portion K of the cam groove other than the zoom operation area and the macro photography area, the cam 7
A groove is provided for use in attaching the lower.

For example, it is preferable to extend the cam groove part on the telephoto side where the two cam groove start positions substantially coincide with each other in the optical axis direction, from the viewpoint of workability in connecting the cam 7 lower.

However, the installation position is not limited to this.

It is also effective to make the groove for attachment wider than the width of the cam groove in the zoom operation or macro operation area.

[Embodiments of the invention]

Examples of the present invention will be described below. FIG. 1 is a developed view showing one embodiment of a cam ring according to the present invention, and FIG. 2 is a sectional view of a main part of a zoom lens barrel provided with this cam ring.

In FIG. 2, 3 is a variable power lens group holding member, 4 is a correction lens holding member, and 5 is a penetrating member that penetrates the holding member 4.
It is a guide member that guides the lens in the optical axis direction, and one end is connected to the fixed tube 6.
and the other end thereof is locked in holes provided in the holding plate 7, respectively. (The guide member of the variable power lens group holding member 3 is omitted from the illustration)
A cam ring 8 is rotatably fitted on the circumferential surface of the fixed cylinder 6, and cam followers 9 and 9' attached to the holding members 3 and 4 are engaged with this cam @8. , cam grooves 1 and 2 for moving cam followers 9 and 9' in the optical axis direction are provided. This cam groove will be explained in detail with reference to FIG. 1 is a cam groove for the variable magnification lens group holding member 3, and the cam groove is a macro photography area 1a.

It consists of a zoom shooting area 1b and a cam follower attachment area 1c. 2 is a cam groove for a correction lens holding member; similarly, the cam groove 2 is used for macro photography area 2a, X-mu photography area 2;
b, and a cam 7 lower attachment area 2c.

In the zoom section configured as described above, the assembly of the zoom section involves attaching the guide member 5 to the fixed tube 6, holding members 3, 4, and so on. After inserting the cam ring 8, attach the holding plate 7. Thereafter, the lowers 9 and 9' of the cam 7 are fitted into the cam grooves 1c and 2c through holes (not shown) made in the fixed tube, and are attached to the holding member 3.4. At this time, the holes drilled in the fixed cylinder are cam grooves 1c,
The K is placed above the cam follower attachment area of 2c, so that the cam follower can only be attached in this area.

The cam ring of this embodiment has the advantage that it can be easily produced with only a slight increase in machining time, since the cam groove is simply extended under pressure.

By the way, since the cam follower mounting groove has the same groove width as the zoom photographing areas 1b and 2b as shown in the figure, scratches may occur here. The scratches on the cam follower mounting grooves 1c and 2c are used only when assembling, and are not used during zooming or macro photography, so they do not directly serve as supporting rings for operational performance, but sometimes when they are scratched, they also cause chips. There is a slight risk that the chips may adhere to the lens surface and cause other defects.

Another embodiment that improves this point will be described with reference to FIG. FIG. 3 is a developed view of the cam ring in which the groove width T of the cam follower mounting groove is wider than the groove width t of the zoom photographing areas 1b and 2b. The groove iJ difference (Tt) is required to be 50 μm or more. If the groove width difference is smaller than 50 μm, there will be little effect in preventing damage to the groove side surfaces when attaching the cam follower. In addition, in order to smoothly move the cam follower from the cam lower mounting groove to the zoom range or macro photography range, it is necessary to connect both grooves smoothly. Therefore, when the groove width difference becomes large, the groove connecting portion 1d,
2d becomes longer, and as a result, the length of the groove becomes significantly longer.

This means that not only does it take time to process the grooves, which increases costs, but also makes the cam ring more likely to deform. From the above point of view, it is appropriate that the groove width difference is 0.1 to 1.

Next, the installation of the cam 7 lower in this embodiment will be explained. The cam follower may be mounted using the cam follower mounting groove as described in the previous embodiment, but the cam follower may not always be fixed in the specified position due to looseness, so it may not be possible to install the cam follower in the same position as the variable magnification lens group. This may cause the correction lens spacing to be incorrect, or the cam follower may not be able to move smoothly along the cam groove. A method of attaching a cam follower that is improved in this respect will be explained with reference to FIG. FIG. 4 is a sectional view of the main parts of the zoom section, where 5 is a guide member, 6 is a main cylinder,
8 is a cam ring, 9 is a cam 7 lower, 10 is a screw hole for locking the cam 7 lower provided in the holding member 12 of the lens 11, and 13 is a lens holder. First, Figure 4 (], HC
As shown, the cam follower 9 is temporarily fastened to the locking screw hole through the hole 15a formed in the fixed cylinder in the cam lower mounting groove 14. At this time, the screw may tilt due to the play in the screw, but since the groove width of the cam ring is wide, the side surface of the groove will not be damaged. Rotate the cam ring to the specified cam groove in the next pressure zoom range. By doing so, Figure 4 (
As shown in 2), the button cam follower 9 is guided by the cam groove to the normal position. The cam ring 80 is rotated to the position where the tightening hole 15b is drilled in the fixed cylinder 6. By fully screwing the cam follower 9 in this state, it is fixed as shown in FIG. 4 (3).

Although a screw-in type cam follower has been described here, it goes without saying that the present invention is not limited to any method for engaging the cam 7 lowerer.

Furthermore, in the above embodiment, the case where there are two cam grooves has been described, but depending on the type of lens, there may be three or more cam grooves, and the method of the present invention can be applied as is.

〔Effect of the invention〕

According to the present invention, a groove for attaching the cam follower is provided on the extension of the zoom shooting range, and the cam 7 lower is attached to this groove, which may damage the cam groove when assembling the cam follower to the holding member. This eliminates the clicking effect in the zoom shooting area, and allows smooth zooming.

[Brief explanation of the drawing]

FIG. 1 is a developed plan view of a cam ring showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of a zoom lens needle barrel using the cam ring of FIG. 1, and FIG. Another cam groove invention!
The developed plan view showing #t11, and FIG. 4, is a non-BA view showing the method of installing the cam follower in the present invention. 1.2...Cam groove, la, 2a...Macro shooting area lb, 2b...Zoom shooting area lc, 2c...Camuno-row-taking area 8...Cam ring 9, 9'... cam follower.

Claims (1)

[Claims] 1. A cam capable of performing zooming photography and macro photography by moving a holding member holding a variable magnification lens group and a correction lens in the optical axis direction while maintaining a predetermined positional relationship. In a zoom lens barrel equipped with a cam ring having a groove, a groove part for fitting into the cam groove and attaching a cam follower to the holding member is extended to an end of the cam groove part in a zooming photography and macro photography area. A zoom lens cam ring characterized by the provision of a cam ring. 2. The cam ring for a zoom lens as set forth in claim 1, wherein the groove for attaching the cam follower is a groove wider than the cam groove width for zooming photography and macro photography areas.