JPS615218A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To make a zoom lens barrel light-weight and low-cost by using aluminium as materials of a cam ring and using plastics as materials of a fixed cylinder in the zoom lens barrel and pressing a correcting system in one direction with a spring material. CONSTITUTION:In the zoom lens barrel, plastics are used as materials of a fixed cylinder 1, and aluminium is used as materials of a cam ring 2, and a coil spring 5 is interposed with a rod 4 as the core between a correcting system 3 and a retaining plate 6. The correcting system 3 is pressed right by the coil spring 5 to press a cam follower 7 to the right of a cam groove 8 of the cam ring 2, thus reducing play of the correcting system 3.

Description

[Detailed description of the invention] [Field of application of the invention] The non-invention relates to zoom lens barrels.

In particular, this is intended to prevent displacement of the focal plane due to backlash in the optical axis direction of the zoom section when a plastic material is used for the fixed barrel.

[Background of the invention]

The conventional zoom lens barrel is actual open m5s-1508.
As shown in Publication No. 24, the backlash due to the difference in length in the optical axis direction between the fixed tube and the cam ring was controlled by a shaft, so this backlash was only allowed to be about 10 to 30 μm. do not have. Therefore, when plastic material is used for the fixed barrel and aluminum material is used for the cam ring, the difference in expansion coefficient between the plastic material and the aluminum material in the operating temperature range of the zoom lens - 10°C to 50°C will cause the difference between the fixed barrel and the cam ring. Due to the difference in length in the optical axis direction of about 40 μm, the difference becomes 0 μm at the operating temperature where there is play between the fixed cylinder and the cam ring. As a result, the cam ring cannot be rotated, so t
i! Since it is not possible to use materials with different expansion coefficients for the i1 front leg and the cam ring, it is possible to reduce costs by using a plastic material for the fixed cylinder, which is both rx and good.

Regarding the housing, if both are made of plastic material, the difference in expansion coefficients will not be a problem, but since it is impossible to cut the cam groove with a good oval in the cam ring with plastic material, it is not possible to fix the cam ring. Plastic materials cannot be used for both the cylinder and the cam ring.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens that uses a glass material for a fixed barrel and is low in cost and light in weight.

[Summary of the invention]

When a plastic material is used for the fixed tube, the difference in stiffness in the optical axis direction from the aluminum cam ring is between -10°C and 5°C at the operating temperature.
In order to rotate the cam area within a range of 0°C, the difference in thermal expansion coefficients between the fixed cylinder and the cam ring is used. Change in length about 4
It needs to be 0 μm or more, and when considering the accuracy of one part, it is about 50 to 70 μm. Then, the amount of backlash between the fixed barrel and the cam ring in the optical axis direction also becomes 50 to 70 μm, increasing the focal position shift of the zoom lens. In order to solve this problem, the present invention constantly pushes the correction system of the zoom lens in one direction using a coil spring or the like.

This is intended to reduce the wobbling of the correction system due to the wobbling between the fixed barrel and the cam ring, and eliminate the bottleneck caused by the focus position.

Example of 0 cases] Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.

In the figure, 1 is a fixed cylinder, 2 (ecam moat), 3 is a compensator (correction system), 4 is a rod, 5 is an echo coil,
It is 6t1 press similar%, 7&s force moon lower, 8t ekam yeast.

Cam ring 2 is made of aluminum and has a length of 36,000 to 5 at 20℃.
6015, fixed cylinder 1 p C' G (30%)
So, the length of the cam drilling part at 20°C is 3a045~56.
The backlash between the cam ring 2 and the fixed cylinder 1 at room temperature of 20° C. is [J, 03 to 0.06 mm. At low temperature -10℃.

Since it is 0.02zx larger than the cam area 2 of the fixed tube 1 of pC-G (30 inches) made of violet or aluminum material, the amount of play between the cam ring 2 and the fixed tube 11 is 0.01 to 0.04 mηL. .

At a high temperature of 50℃, the play f is 0.05~
It becomes 0.08B. Usually this rattling lid is 0.01 to 0.0
4 mm, and within this range P3, the focal position shift is also within the allowable range. Therefore, in the present invention, C is placed around the rod 4 in the direct position range of room temperature to high temperature, and the katakaku described in 81J exceeds the permissible level.

A cam follower 7 is placed between the pressing plate 6 and the compensator 3, with a coil spring 5 interposed between them.

The right HVC in the diagram of cam groove 8 is pressed 51C
This prevents the compensator 3 from rattling.

It should be noted that in the present invention, the rattling of the variable power system has not been addressed, and at room temperature and high temperature,
Although the % wobble is larger than before, near the wide angle of zooming, the focus position shift due to the play in the variable magnification system is about 1 AD of the focus position shift caused by the play in the correction system, which is about 1 AD. C.

In addition, when zooming near telephoto, the focal position shift due to rattling in the magnification system is almost the same as that due to rattling in the correction system, but near telephoto, the depth of field is leaked, so There is no problem because the user can easily adjust the beats by turning the ring.

As mentioned above, according to this embodiment, even if the fixed barrel of the zoom lens is made of glass-tilek material and the cam ring is made of aluminum material,
The cam ring rotates smoothly at low temperatures, and the focus position shift at normal and high temperatures can be kept within an allowable level.

Also, Ii! j Increase the difference in length between foot lock 1 and cam area 2 by an even larger length (approximately 1 to 2 mm) L, and place it on the left or right side of cam area 2.
The present invention can also be ojed by intervening a spring or the like.

〔Effect of the invention〕

According to the present invention, since a fixed barrel made of glass material can be used, there is an effect that a zoom lens barrel can be manufactured at a low cost.

[Brief explanation of the drawing]

The figure is a sectional view of a main part of a zoom portion of a -'AM example of a zoom lens barrel according to the present invention.

Claims (1)

[Claims] A variable power system, a correction system, a rod for moving these in the optical axis direction, a cam ring having a groove for controlling the positions of the variable power system and correction system, and a fixing member for rotatably holding the cam ring. In the zoom lens barrel, the cam ring is made of aluminum and the fixed cylinder is made of aluminum, and the cam ring is rotated to move the variable power system and the correction system to zoom from telephoto to wide angle. The difference in length in the optical axis direction between the cam ring and the fixed barrel is determined by the difference in length in the optical axis direction between the cam ring and the fixed barrel due to temperature changes within the operating temperature range of the zoom lens. a spring material for pressing the correction system in one direction around a rod portion on which the correction system slides;
A zoom lens mirror unit, wherein play in the optical axis direction of the correction system is reduced.