JPS635735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens holding device that holds a lens in a lens frame, and in particular, a lens holding device that holds a lens in a lens frame so that a plastic lens with weak temperature resistance does not change its shape even when the temperature changes. The purpose of this invention is to provide a lens system that maintains lens performance and has strong temperature resistance by fixing the lens inside the lens, and also to expand the operating temperature range of plastic lenses and other lenses that do not have temperature resistance.

Conventionally, when a lens, for example, a plastic lens 7, is mounted in a lens frame 2, the outer peripheral edge 7a of the rear surface of the plastic lens 7 is brought into contact with the lens frame mounting portion 4 of the lens frame 2, as shown in FIG. 1a. The plastic lens 7 is fitted into the lens frame fitting part 5, and the threaded part 6 threaded on the outer periphery of the presser ring 1 is screwed into the lens frame threaded part 3 threaded on the inner periphery of the lens frame 2. The presser ring 1 is screwed into the inside of the lens frame 2, and the abutting edge 1a formed on the inner circumferential edge of the presser ring 1, which contacts the plastic lens 7, is pressed against the outer circumferential edge 7b on the front side of the plastic lens 7, and the plastic lens 7 is fixed within the lens frame 2.

Now, when the plastic lens 7 having such a configuration is assembled to the lens frame 2 at room temperature and then exposed to a high temperature atmosphere, the linear expansion rate of the molding material of the plastic lens 7 will be different from that of the lens frame 2 and the presser. Because it is larger than the linear expansion rate of the molding material of ring 1,
The clearance of the lens frame fitting portion 5 in the lens frame 2 is reduced.

Furthermore, the first group is most affected by this effect.
Contact part 8 between lens 7 and presser ring 1 in Figure a
(Refer to the enlarged view shown in Fig. 1b), the clearance is already zero when the part is assembled at room temperature, and the forming of the lens 7 and the presser ring 1 occurs in the high temperature atmosphere. The difference in the coefficient of linear expansion of the materials directly affects the surface shape.

That is, the contact portion 8 of the lens 7 and the presser ring 1
In this case, the outer peripheral edge 7b on the front side of the lens 7, which the contact edge 1a of the presser ring 1 presses against, is depressed, and the lens 7 is regulated to a state of zero clearance by the contact edge 1a of the presser ring 1. .

Therefore, as the temperature increases, the plastic lens 7 begins to expand in the radial direction, but the restraint ring 1 restricts the deformation of the plastic lens 7 in the radial direction. Thermal stress is generated inside the lens 7.

Then, the thermal stress generated inside the plastic lens 7 concentrates on unregulated deformation in the optical axis direction, causing the plastic lens 7 to deform in the optical axis direction.

Considering the cross section in the axial direction including the optical axis of the plastic lens 7, since the length of the chord AB in FIG. radius becomes smaller.

Now, the length of the arc at room temperature is AB⌒, which is t°C than room temperature.
If the length of the arc at high temperature is A'B'⌒, and the coefficient of linear expansion of the plastic lens 7 is a, then it is approximated as A'B'⌒≒AB⌒・(1+αt).

Conversely, when the plastic lens 7 and lens frame 2 assembled together at room temperature are exposed to a low-temperature atmosphere, the plastic lens 7, lens frame 2, and retaining ring 1
Due to the difference in the coefficient of linear expansion of the molded materials, as the temperature decreases, the lens frame 2 and the presser ring 1 contract.
The shrinkage of the plastic lens 7 is large and tends to shrink more than the contraction of the lens frame 2 and the presser ring 1, but in this case as well, the front surface of the plastic lens 7, which is fixed by the pressure contact of the contact edge 1a of the presser ring 1, As a result of the side outer peripheral edge 7b being regulated, the plastic lens 7 cannot contract more than the contraction of the presser ring 1, similar to the case at high temperatures, and thermal stress is generated inside the plastic lens 7. At the same time, this thermal stress is concentrated in the optical axis direction of the plastic lens 7, which is not restricted by the presser ring 1, and causes deformation of the plastic lens 7 in the optical axis direction.

Therefore, the plastic lens 7 shown in FIG.
Considering the axial cross section including the optical axis, the chord AB⌒
Since the length of is regulated by presser ring 1, arc AB
The contraction concentrates on the area, and as a result, the radius of curvature increases.

Now, if the length of the arc at room temperature is AB⌒, the length of the arc at t°C lower than room temperature is A'B'⌒, and the coefficient of linear expansion of the molding material of the plastic lens 7 is α, then A'B' Approximate to ⌒≒AB⌒・(1−αt).

Therefore, from the above, when the plastic lens 7 is attached to the conventional lens frame 2 with the presser ring 1, the radius of curvature of the plastic lens 7 changes due to temperature changes. It is clear that the temperature becomes larger at room temperature, and that the focus position shifts significantly and various aberrations worsen compared to when the temperature is normal.

In addition, in the conventional lens and lens frame configuration, as shown in FIG.
1 and 22 and both lenses 21 and 22
By interposing the centering member 24 between them, the two lenses 2 that are adjacent to each other by their outer peripheral edges can be
A composite lens constructed to reduce the frictional resistance between lenses 1 and 22 and to prevent lens misalignment between both lenses 21 and 22 was proposed in Japanese Utility Model Application Publication No. 55-138606. ing.

However, in the case of this configuration, two lenses 2
The structure in which the lenses 21 and 22 are fixed in the fitting part 26 by the presser ring 25 only reduces the friction between the lenses 21 and 22, and there is no change in the conventional structure. The outer diameter is regulated by the fitting part 26 of the lens holding member 23 or the inner diameter of the holding ring 25, and similarly to the plastic lens 7, changes in the radius of curvature due to temperature changes of both lenses 21 and 22 can be prevented. First, it is impossible to avoid a shift in focus position and worsening of aberrations due to temperature changes.

Therefore, there is a need for a lens holding structure that prevents changes in the radius of curvature caused by temperature changes in the conventional lens mounting structure for a lens frame, and that does not cause focus position deviation or worsening of various aberrations, or other lens holding structures. There was a strong need for the development of appropriate countermeasures.

Therefore, the present invention proposes a lens holding device that can solve the various drawbacks of the conventional lens holding device described above and meet the above-mentioned demands.Hereinafter, examples of the lens holding device of the present invention will be specifically described with reference to the drawings. Explain in detail.

FIG. 2 shows an embodiment of the lens holding device of the present invention, and numeral 30 is a lens frame made of synthetic resin as a molding material, and this lens frame 30 is provided with a threaded portion 31 into which a retaining ring 50 is screwed. A lens barrel mounting portion 32 of the plastic lens body 40 is provided, and a fitting portion 33 of the deformation absorbing sleeve 60 as an elastic member is provided.
A deformation absorbing portion 34 serving as a thin barrier for holding the deformation absorbing sleeve 60 is integrally formed on the inner periphery of the deformation absorbing sleeve 60 .

In the embodiment shown in FIGS. 2a and 2b, the lens barrel mounting portion 3
The deformation absorbing portion 2 and the deformation absorbing portion 34 are constructed by protruding intermittently at three locations in the circumferential direction of the lens frame 30, but both are constructed by continuously protruding from the inner periphery of the lens frame 30. It is also possible to configure

The deformation absorbing sleeve 60 is stored in the fitting part 33 as a storage part of the lens frame 30, with the flange part 61 having a thin plate structure on the inside and the lens frame fitting part 62 on the outside.
are integrally formed from synthetic resin.

In addition, the flange portion 61 of the deformation absorbing sleeve 60
A lens fitting portion 63 having an inner diameter corresponding to the outer diameter of the plastic lens body 40 is provided on the inner periphery of the plastic lens body 40 .

Although the flange portion 61 of the deformation absorbing sleeve 60 is continuously provided on the inner circumference of the annular lens frame fitting portion 62, it is also possible to divide it and provide it intermittently (not shown). It is.

Now, when fixing the plastic lens body 40 within the lens frame 30 having the above configuration, first,
The plastic lens body 40 is fitted into the lens fitting portion 63 provided on the inner periphery of the flange portion 61 of the deformation absorbing sleeve 60, and the plastic lens body 40 is formed into a thin wall shape protruding from the inner periphery of the deformation absorbing sleeve 60 as an elastic member. The plastic lens body 40, which is supported by the flange portion 61 that acts as a barrier to the lens frame 30 and is fitted into the deformation absorbing sleeve 60, is
, and fit the lens frame fitting part 62 of the deformation absorbing sleeve 60 into the fitting part 33 of the lens frame 30, so that the deformation absorbing sleeve 60 protrudes from the inner periphery of the lens frame 30. thin-walled deformation absorbing section 34
After supporting the plastic lens body 4 with
It is fixed at 0.

When a temperature change is applied to the plastic lens body 40 held in the lens frame 30 in the lens holding device comprising such a process, the plastic lens body 40 expands and contracts as the cold and heat changes are repeated, causing generation in the radial direction. The thermal stress caused by the deformation absorbing portion 34 of the lens frame 30 and the deformation absorbing sleeve 60
is absorbed by the elastic deformation of the flange portion 61 of
This prevents changes in the radius of curvature of the plastic lens body 40.

Therefore, the plastic lens body 40 is attached to the lens frame 3.
0, there is no need to particularly expand the clearance with the lens frame 30, including the clearance for fitting with the deformation absorbing sleeve 60, and the settings can be made as before, so the lens performance remains the same as before. can be maintained at the same level.

In absorbing the thermal stress in the radial direction, the elastic deformation of the deformation absorbing portion 34 and the flange portion 61 of the deformation absorbing sleeve 60 is used. It is possible to design the plastic lens body 40 without relying solely on shape factors such as the thickness of the member to be elastically deformed, and without regard to the material of the plastic lens body 40, so that moldability and assembly workability are satisfied for the intended purpose. It is possible to measure the realization while

The lens holding device of the present invention has the above-mentioned structure, and has a three-way structure consisting of a lens frame, a plastic lens housed therein, and an elastic member inserted between the two. In this case, a deformation absorbing part that absorbs the thermal stress in the radial direction due to thermal expansion of the plastic lens is provided at the fitting part with the deformation absorbing sleeve as an elastic member, and in the case of an elastic member, the deformation absorbing part that absorbs the thermal stress in the radial direction due to the thermal expansion of the plastic lens is provided. A deformation absorbing part is provided at the lens fitting part with the plastic lens, and the structure in which the deformation absorbing sleeve is fitted and fixed to the plastic lens stored in the lens frame prevents heat in the radial direction of the plastic lens due to temperature changes. Absorbs stress and prevents changes in the radius of curvature of the lens.

Therefore, it is possible to prevent the focal position from shifting and aberrations from worsening due to temperature changes, and it is possible to expand the operating temperature range of the plastic lens.

Furthermore, by dividing the deformation absorbing portion, the contact area with the deformation absorbing sleeve or plastic lens can be reduced, making it easier to deform structurally, and promoting the desired effect.

Furthermore, since both the lens frame and the sleeve are constructed with deformation absorbing members that absorb thermal stress, by combining the elastic modulus of both materials, the degree of absorption can be adjusted from the perspective of the material. This makes it possible to select a plastic lens that is easy to design, has a well-known structure, and has a wide fitting clearance with the lens frame that exceeds the normal temperature range while keeping the same setting as before. Can be used in a temperature range.

[Brief explanation of the drawing]

1a to 1e show a conventional lens holding device,
Figure 1a is a side sectional view, Figure 1b is a partially enlarged sectional view of Figure 1a, and Figures 1c and d show changes in the radius of curvature due to temperature changes in the lens holding device of Figure 1a. Explanatory drawings, FIG. 1e is a side sectional view showing an embodiment different from FIG. 1a, FIG. 2 is an embodiment of the lens holding device of the present invention, and FIG. 2a is a side sectional view;
FIG. 2b is a front sectional view, and FIG. 2c is a front view of the deformation absorbing sleeve. 30... Lens frame, 31... Screw part, 32... Lens barrel attachment part, 33... Fitting part, 34... Deformation absorbing part, 40... Plastic lens body, 50...
Holding ring, 60... Deformation absorbing sleeve, 61... Flange portion, 62... Lens fitting portion, 63... Lens fitting portion.

Claims (1)

[Scope of Claims] 1. A lens holding device for holding a plastic lens on a lens frame, comprising: a deformation absorbing device comprising a thin piece protruding from the inner periphery of the lens frame in a direction perpendicular to the optical axis, facing the lens peripheral wall; part 34, an annular lens frame fitting part that is disposed between the deformation absorbing part and the peripheral wall of the lens and comes into contact with the tip of the deformation absorbing part, and a thin wall that protrudes from the inner periphery of this fitting part toward the lens peripheral wall. Deformation absorbing sleeve 60 with pieces
a lens that fits into the tip of the thin piece; a barrel portion 32 that protrudes from the lens frame in a direction perpendicular to the optical axis so as to prevent movement of the lens and the deformation absorbing sleeve in the optical axis direction; and the lens and a presser ring 50 screwed onto the lens frame so as to press the deformation absorbing sleeve toward the barrel portion and clamp it.