JP2014006414A - Lens holding device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in that a camera used in an environment where an ambient temperature changes significantly, optical characteristics and so on deteriorate due to heat stress caused in a lens by a difference between a lens and a lens barrel in linear expansion coefficient, and, to countermeasure it, a lens holding device that mitigates heat stress in the lens by use of an elastic body or adhesive has been proposed, which makes accurate assembly difficult due to the use of the elastic body or adhesive and cannot satisfy a highly accurate optical characteristic since the elastic body or adhesive deforms by its own weight of the lens even after the assembly.SOLUTION: A lens is held using carrier and retainer made of a material whose linear expansion coefficient is close to that of the lens. Thereby, heat stress caused by the difference between a lens barrel and lens in linear expansion coefficient can be mitigated. As a result, heat stress in the lens can be reduced, and the lens can be held by the carrier made of metal and the retainer.Accordingly, the holding function for the lens is stabilized, and highly accurate optical characteristic can be obtained.

Description

The present invention relates to a lens holding device. In particular, the present invention relates to a lens holding device that relieves thermal stress generated in a lens when ambient temperature changes without using an elastic body.

  Conventionally, as a lens holding device, as will be described later, a lens barrel is formed by attaching one surface of a lens to a holding portion that is integrally processed with a lens barrel and turning a screw around the periphery of the lens. A lens holding device having a structure of screwing and pressing a lens with a retainer is disclosed.

However, in such a conventional lens holding device, when used in an environment where the ambient temperature changes greatly, the optical characteristics are deteriorated or the lens is damaged due to the thermal stress generated in the lens due to the difference in linear expansion coefficient between the lens and the lens barrel. There was a problem that occurred.

As a countermeasure against this, a lens holding device has been proposed in which a thermal stress generated in a lens is reduced by using an elastic body or an adhesive (see, for example, Patent Documents 1 and 2).

JP-A-57-138606 JP-A-57-141607

Lens holding devices using elastic bodies and adhesives as described above are effectively used to relieve thermal stress in environments where the ambient temperature changes greatly, but use elastic bodies and adhesives. Therefore, it is difficult to assemble with high accuracy, and there is a problem that even after the assembly, the elastic body and the adhesive are deformed by the weight of the lens, and high-precision optical characteristics cannot be satisfied.

In addition, there are problems that it is difficult to inject an elastic body and an adhesive into a lens barrel having a complicated shape at the time of assembly, and that the curing time of the elastic body and the adhesive is long, resulting in an increase in assembly cost.

In addition, the elastic body and adhesive may be crushed due to the difference in linear expansion coefficient between the lens, lens barrel, elastic body and adhesive, and the elastic force may be lost. There was a problem that it was necessary to design and adjust.

The present invention has been made in order to solve the above-described problems, and can relieve thermal stress generated in the lens in an environment where the ambient temperature changes greatly, and without using an elastic body or an adhesive to hold the lens. An object of the present invention is to provide a lens holding device capable of realizing high-precision optical characteristics and cost reduction.

  The lens holding device according to the present invention is a lens holding device for holding a lens, and includes a lens barrel provided with a convex holding portion protruding inside the lens barrel, and a carrier that fits with the inner wall of the lens barrel. A retainer which is fitted with the inner wall of the lens barrel and turned in a circumferential direction, and one surface of the carrier is in contact with the holding portion, and the lens is mounted between the carrier and the carrier. The retainer is screwed into and fixed to the lens barrel, and the linear expansion coefficients of the carrier, the retainer, the lens, and the lens barrel are in a relationship of lens <carrier = retainer <lens barrel.

According to the lens holding device of the present invention, it is possible to provide a lens holding device that can relieve the thermal stress generated in the lens, can achieve high-precision optical characteristics, reduce assembly work, and can be reduced in size and weight.

It is sectional drawing of the lens holding device which concerns on Embodiment 1 of this invention. It is sectional drawing explaining the lens holding method which hold | maintains the conventional lens to a lens-barrel. It is sectional drawing explaining the lens holding method which inserts an elastic body between the conventional lens and a lens-barrel, and hold | maintains a lens.

FIG. 2 is a cross-sectional view for explaining a lens holding method for holding a conventional lens in a lens barrel. FIG. 3 is a cross-sectional view illustrating a lens holding method for holding a lens by sandwiching an elastic body between a conventional lens and a lens barrel.
As shown in FIG. 2, a lens barrel in which a retainer 4 having a lens 3 is attached to a holding portion 2 integrally processed with the lens barrel 1 and a screw 7 is turned on a part of the inner side is provided. 1, and a device for pressing the lens 3 with a retainer 4 was used. Further, as shown in FIG. 3, the thermal stress generated by the difference in linear expansion coefficient between the lens barrel 1 and the lens 3 is relaxed by the elastic body 5 or the adhesive 8 to reduce the thermal stress generated in the lens.

Embodiment 1 FIG.
Hereinafter, an embodiment according to the present invention will be described with reference to FIG. In the lens holding device according to the first embodiment, the carrier 6 that fits into the lens barrel 1 is fitted to the holding portion 2 that is integrally processed with the lens barrel 1, and after the lens 3 is placed on the carrier 6, The retainer 4 with the screw turned is screwed into the lens barrel 1 with the screw 7 turned to a part of the inside, and the lens 3 and the carrier 6 are pressed and held.
At this time, by using the carrier 6 and the retainer 4 made of a material close to the linear expansion coefficient of the lens 3 as compared with the linear expansion coefficient of the lens barrel 1, heat generated in the lens 3 under an environment where the ambient environment temperature changes greatly. The stress is relieved by the carrier 6 and the retainer 4.
For example, when the material whose linear expansion coefficient is lens 3 <carrier 6 = retainer 4 <lens 1 is used and the temperature changes to the low temperature side, the barrel 1 contracts more than the lens 3. On the other hand, since the carrier 6 and the retainer 4 are less likely to contract than the lens barrel 1, the thermal stress generated in the lens 3 due to the contraction of the lens barrel 1 can be relaxed by the carrier 6 and the retainer 4.

In addition, since the carrier 6 is made of metal instead of an elastic body, the holding function after assembly is stable and high-precision optical characteristics can be obtained.

Furthermore, by using the carrier 6, it is possible to select the lens barrel 1 made of various materials, and to hold a variety of lenses 3 having different linear expansion coefficients in one lens barrel 1.

By mounting this lens holding device on a camera (imaging device), a camera having excellent optical characteristics can be provided at low cost even in an environment where the ambient temperature changes greatly.

As described above, according to the lens holding device of the present invention, the heat generated by the difference in linear expansion coefficient between the lens barrel and the lens is obtained by holding the lens using the carrier and the retainer made of a material close to the linear expansion coefficient of the lens. Stress can be relieved by carrier and retainer.
In addition, since the thermal stress generated in the lens can be reduced and the lens can be held by metal, the holding function is stable and high-precision optical characteristics can be obtained.
In addition, the assembly cost can be reduced because there is no need to inject and cure the elastic body and adhesive during assembly.
Furthermore, by using a metal carrier and retainer, it is possible to eliminate the work of designing and adjusting the thickness so that the elastic body and the adhesive do not lose the elastic force.
Further, it becomes possible to reduce the thermal stress of any lens regardless of the linear expansion coefficient of the lens. Therefore, the material of the lens barrel can be selected without depending on the lens for an optical system composed of many types of lenses having different linear expansion coefficients. For example, the weight can be reduced by selecting a material with a low density for the lens barrel.
Furthermore, by applying the present invention to a camera having an athermal (temperature-independent) optical system composed of various types of lenses having different linear expansion coefficients, a focus adjustment mechanism and a mechanism control substrate are not required. The camera can be made smaller and lighter and the manufacturing cost can be reduced. Furthermore, the power required for the mechanism that is driven during focus adjustment and the substrate that controls the mechanism can be reduced, and the power saving effect of the camera can be obtained.

1 barrel, 2 holding part, 3 lens, 4 retainer, 5 elastic body, 6 carrier, 7 screw, 8 adhesive.

Claims (3)

A lens holding device for holding a lens,
A lens barrel having a convex holding portion protruding inside the lens barrel;
A carrier that fits into the inner wall of the lens barrel;
A retainer that fits with the inner wall of the lens barrel and is turned in the circumferential direction;
With
One surface of the carrier is fixed in contact with the holding portion,
The retainer is fixed by being screwed into the lens barrel in a state where the lens is mounted between the retainer and the carrier,
Each linear expansion coefficient of the carrier, the retainer, the lens, and the lens barrel is
Lens <Carrier ≒ Retainer <Lens holding device characterized by the size relationship of the lens barrel. 2. The lens holding device according to claim 1, wherein the carrier and the retainer are made of a metal material having a linear expansion coefficient that is closer to the linear expansion coefficient of the lens than the linear expansion coefficient of the lens barrel. An imaging device in which the lens holding device according to claim 1 is mounted as an optical component.

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