JPS6296916A - Plastic lens holding device - Google Patents

Abstract

PURPOSE:To absorb and eliminate the change of dimensions due to the temperature change between a lens and a mount part and to suppress the deformation of lens faces, which are affected greatly by the change of dimensions, as much as possible by providing an elastic member between the plastic lens and a retaining member. CONSTITUTION:A mount part 12 is formed in a lens holding cylinder 11 as one body, and one lens face r2 of a plastic lens 13 is brought into contact with a corner part 23 of the mount part 12. An elastic member 24 slightly softer than the plastic lens is brought into contact with the other lens face r1 of the plastic lens 13, and a retaining ring 15 is arranged on the outside of the elastic member 24. When the plastic lens 13 is deformed, the elastic member 24 absorbs the deformation of the plastic lens to suppress the action of a great stress upon the plastic lens. When the plastic lens 3 is much deformed, the stress is applied to the plastic lens 13 and the lens face r1 which has less influence upon the lens capacity is deformed, but the deformation of the lens face r2 which has a great influence upon the lens capacity is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic lens holding device, in particular, a plastic lens that absorbs deformation of the lens due to changes in ambient temperature using an elastic member made of a material slightly softer than the hardness of the lens. The present invention relates to a holding device.

First, a method of holding a conventional general lens using a barreled portion formed on a lens support tube and a presser ring that presses the lens will be described. FIG. 1A is a longitudinal sectional view showing an example of a conventional method for holding a lens in a support tube. The method of holding the lens 2 on the support tube 1 is to abut the lens 2 against the corner 3a of the barreled part 3 that is integrally formed with the support tube, and then attach a retainer ring 4, which is threaded around the periphery, also on the inside side. Partially threaded part 5
It is screwed into the machined support tube 1 and held by pressing it against the corner 3a. This presser ring 4 is screwed together with the support tube 1 through a threaded portion 5, and is held in the support tube 1 while being press-fitted to the lens 2. Further, the barreled portion 3 is provided with a fitting portion 6, the inner diameter of which is made slightly larger than the outer diameter of the lens 2. However, this difference between the inner diameter of the fitting part 6 and the outer diameter of the lens 2 causes wobbling when the lens 2 is assembled into the barreled part 3 of the support tube 1. The amount of backlash is extremely small so as not to affect performance.

Now, if the material of this lens 2 is glass, even if the lens system shown in FIG. Since the coefficient is small, the inner diameter of the support tube 1 is larger than the outer diameter of the lens 2, and a phenomenon in which the support tube 1 tightens the lens 2 does not occur. However, if the material forming the lens 2 is plastic, the expansion of the lens 2 is much larger than the expansion of the support tube 1.
When the lens system shown in FIG. 1A is brought to a high temperature state, the outer diameter of the lens 2 becomes larger than the inner diameter of the barreled portion 3 of the support tube 1.

FIG. 1B is a diagram showing the relative displacement of the inner and outer diameters of the support cylinder 1 and the lens 2 depending on the above-mentioned temperature. In FIG. 1B, the solid line shows the normal temperature state, the dashed line shows the free expansion state of the lens 2 and the support cylinder 1, and the dotted line shows the balanced expansion state of the lens 2 and the support cylinder 1. In other words, when looking at FIG. 1B, as the temperature rises, the lens 2 expands and the outer diameter D'L increases as the temperature rises. Furthermore, the inner diameter of the barreled portion 3 is D'.

However, in reality, even if the lens 2 in FIG. 1A tries to expand, it is held down by the barreled portion 3, and the lens 2 as shown in FIG. 1B
The outer diameter OL is smaller than the free expansion lens having the outer diameter D'L, and becomes the outer diameter □nL. On the other hand, in FIG. 1A, even if the barreled part 3 expands, the lens 2 on the inside tries to expand, so it is further pushed open, and as shown in FIG. 1B, the barreled part 3 expands. The inner diameter DK is larger than the inner diameter D' (
) become uK. Therefore, the lens 2 and support tube 1 in FIG.
When the lens is placed in a high temperature state, the inner diameter D'L of the lens changes as shown in Figure 1B.
A compressive stress is generated in the outer diameter D'K of the support tube, and a tensile stress is generated in the outer diameter D'K of the plastic lens.The mutual expansion is balanced and the outer diameter of the lens becomes D'', which becomes the outer diameter QLIK of the support tube.This stress causes the plastic lens to Thin wrinkles, undulations, or large changes in the radius of curvature may result in large aberrations on the lens surface where it is thinnest, that is, on the outer periphery for positive lens 2 or at the center for negative lens. As the lens changes, the imaging characteristics also change.If compressive stress occurs when both ends are fixed, buckling may occur in a negative lens with a thin center thickness.In addition, the lens system is affected by these The optical axis of the lens may shift, the lens may become eccentric or tilted, the distance between the lenses may change, and lens performance may deteriorate.These are one of the major disadvantages of using plastic lenses. Ta.

The present invention eliminates the above-mentioned drawbacks, and when using a plastic lens, optical disturbances caused by the difference in linear expansion coefficient between the lens and a supporting tube made of different materials, especially the deformation that occurs in the lens at high temperatures, can be eliminated by plastic lenses. An elastic member is provided between the lens and the holding member to absorb and remove dimensional changes due to temperature changes between the lens and the body part, and to minimize deformation of the lens surface, which is greatly affected by deformation. The object is to provide a holding device.

The present invention provides a holding device for holding a plastic lens having lens surfaces whose optical performance is affected by deformation differently. A holding member for holding down the lens; and an elastic member interposed between the holding member and a lens surface that is less affected by deformation and formed of a material slightly softer than the hardness of the lens. The elastic member is characterized in that the lens is pressed and held so as to absorb deformation of the lens due to expansion or contraction of the lens, and to suppress deformation of the lens surface which is largely affected by the deformation.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a longitudinal sectional view showing the structure of an embodiment of the holding device according to the present invention. A barreled portion 12 is integrally formed on the lens holding tube 11, and one lens surface r2 of the plastic lens 13 is brought into contact with a corner portion 23 of the barreled portion. On the other lens surface r1 of the plastic lens 13, there is an elastic member 24 that is slightly softer than the hardness of the plastic lens.
The presser ring 15 is placed on the outside of the elastic member 24. A threaded portion is formed on the outer circumferential surface of this presser ring 15 and screwed into threaded portion 16 formed on the inner circumferential surface of the support cylinder 11 .

Therefore, by screwing the presser ring 15, the plastic lens 13 can be held in pressure contact with the barreled portion 12 via the elastic member 24.

In a lens system having a plastic lens 13, deformation of the lens surface r1 of the lens 13 has little effect on the optical performance of the lens system, but deformation of the lens surface r2 has a strong effect on the optical performance of the lens system. In this case, the lens surface r1, which has a small influence on the lens system, allows some deformation, and the lens surface r2, which has a stronger influence on the lens system,
Try not to deform it as much as possible. For this reason, the lens surface r of the plastic lens 13, which is largely affected by deformation,
2 is pressed against the corner portion 23 of the portion 12, and the lens surface r1, which is less affected by deformation, is pressed by the holding ring 15 via the elastic member 24. With this configuration, when the plastic lens 13 is deformed, the elastic member 24 first absorbs the deformation of the plastic lens, thereby preventing large stress from acting on the plastic lens. Furthermore, if the plastic lens 13 deforms significantly, the elastic member 24 cannot sufficiently absorb this deformation, and the plastic lens receives stress. , deformation of the lens surface r2, which greatly affects lens performance, can be prevented.

Therefore, overall deterioration of lens performance can be suppressed.

Roughly speaking, the position of the lens surface r2 is at the corner part 2 of the barrel part 12.
3 and does not change in the optical axis direction, it also has the effect of ensuring an air gap between adjacent lenses.

Note that the present invention is not limited to the above-described embodiments, and various changes can be made within the scope of the claims.

As described above in the Examples, the effects of the present invention can be summarized as follows.

(b) By providing an elastic member that is made of a highly elastic material and absorbs deformation between the lens and the holding member, deformation occurs near the minimum thickness of the lens in the conventional method, and the lens before deformation There were 2-3 Newton rings,
By deformation, there are 10 or more Newton rings, or the deformation occurs to the extent that it does not form a ring shape, whereas according to the present invention, 2 to 2 Newton rings of the lens before deformation are deformed.
I was able to keep three. In particular, the Newton's ring on the lens surface that comes into contact with the barreled part was able to be maintained at the same level as before deformation.

(b) The lens surface, which has a large effect on optical performance due to deformation, is brought into contact with the barreled part, and the lens surface, which has a small effect on deformation, is pressed by a holding member via an elastic member, so that the effect of deformation is small. Even if the lens surface is deformed, deformation of the lens surface, which has a large effect, can be suppressed as much as possible, and deterioration of optical characteristics can be reduced as a whole.

(c) Since the position of the lens surface, which has a large impact on optical performance, is regulated by the barrel, fluctuations in the air distance between adjacent lenses can be suppressed, and deterioration of the optical performance of the lens system as a whole can be suppressed. .

[Brief explanation of drawings]

Figure 1A is a vertical cross-sectional view showing a conventional method of holding a lens in a support tube, and Figure 1B is a diagram showing the relative displacement of the inner and outer diameters of the support tube and lens due to temperature in Figure 1A. , FIG. 2 is a longitudinal sectional view of an embodiment of the holding device of the present invention. 11... Support cylinder 12... Trunked part 13.
... Lens 15 ... Holding ring 16 ... Threaded part 24 ... Elastic members r+, rz ... Lens surface

Claims (1)

[Claims] 1. In a holding device for holding a plastic lens having lens surfaces whose optical performance is affected by deformation differently, a holding device is formed on a lens support tube holding the plastic lens,
A barreled part that comes into contact with a lens surface that is largely affected by deformation, a holding member that presses the lens, and a holding member that is interposed between the holding member and the lens surface that is smallly affected by deformation, and whose hardness is slightly less than that of the lens. and an elastic member made of a soft material, and the elastic member presses and holds the lens so as to absorb deformation of the lens due to expansion or contraction of the lens.