JPS60230609A - Plastic lens holder - Google Patents

Abstract

PURPOSE:To hold a lens with good accuracy even if environmental conditions change by forming a holding member of a plastic material having a coefft. of thermal expansion and water absorptivity within the prescribed times the coefft. of thermal expansion and water absorptivity of a plastic lens. CONSTITUTION:The lens 6 is held and fixed to a lens barrel 4 by using a coupling member 5 having the coefft. of thermal expansion and water absorptivity within the range of 0.1-1.3 times the coefft. of thermal expansion and water absorptivity of the plastic lens 6. The member 5 is inserted into the lens barrel 4 in such a way that elastic arms 5b provided with pawls are first inserted and that the slopes at the pawl tips contact with the angle provided with the relief notch 4b of the flange part 4a of the barrel 4. The member is further inserted and pushed into the barrel 4 until the pawls embrace the deep side face of the flange part 4a. The arms 5b are deformed in follow up to the change in temp. and humidity so as to absorb a difference in expansion owing to said change thereby preventing disengagement and damage of the lens 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a plastic lens holding device used in cameras and the like.

[Prior art]

Conventionally, plastic lenses (hereinafter simply referred to as lenses)
For glass lenses, a holding device similar to that shown in FIG. 1 was often used. In Fig. 1, 1 is a lens barrel, 2 is a lens, 3 is a holding ring, and the lens 2
The lens holder provided on the inner side of the lens barrel 1 is fitted into the seat from the right side, and the opposite side of the lens holder is held down by a retaining ring 3 to be attached to the lens barrel 1. Note that the presser ring 3 is
The illustrated one screws into the inner surface of the lens barrel 1 to hold down the lens 2, but there are also bayonet type or spring type types that engage with the lens barrel 1 and hold down the lens 2.

In such a holding device, the lens 2 may be damaged due to environmental temperature and humidity conditions due to differences in thermal expansion coefficients between the lens barrel 1 and the lens 2, and the fact that the lens 2 has a certain degree of water absorption. There are problems in that the lens 2 is easily deformed due to looseness in its holding and excessive force applied to the lens 2.

In order to solve this problem, we developed a holding device in which an elastic member is interposed between the lens and the lens barrel or a holding ring (Japanese Patent Application Laid-Open No. 138606/1982), A holding device (Japanese Unexamined Patent Publication No. 1987-87502.87503) in which the shape of the outer peripheral part of the lens to be engaged is made to be easily deformed by elastic material, and the tapered surface of the outer peripheral part of the lens is made of an elastic material. A holding device in which a holding ring is engaged with the lens, and the lens and the lens barrel are not directly engaged or are engaged only on the lens surface side (Japanese Patent Application Laid-open No. 87504/1983).
, ■ A holding device in which the lens and the lens barrel or presser ring are engaged on the lens surface side by point or line contact (Japanese Patent Laid-Open Publication No. 87505/1987)
, ■ A holding device that uses elastic members with a small coefficient of friction in the lens barrel and holding ring that hold down both sides of the lens (Japanese Unexamined Patent Publication No. 87507/1983) has been proposed. . However, in O's holding device, the elastic member compresses and deforms and absorbs the difference in expansion that occurs between the lens, the lens barrel, and the holding ring. If the elastic member contacts the lens, the compressive reaction force of the elastic member becomes large and the lens is easily deformed, and the elastic member contacts the convex surface of the lens, the inner diameter of the lens barrel, and the flange surface perpendicular to the optical axis. If the lens is in contact with the lens, eccentricity is likely to occur between the lens barrel and the lens, and if the elastic member is in contact with the lens, lens barrel, or retainer ring,
There is one or more problems in that the compressive deformation of the elastic member becomes complicated and the lens tends to be eccentric or tilted.

In addition, the @ holding device absorbs the difference in expansion between the lens and the lens diencephalon through sliding of the tapered engagement surface and elastic deformation of the lens outer periphery, so the position of the lens in the optical axis direction was likely to shift. There were problems such as the lens was prone to large distortions in extremely localized areas, it was difficult to obtain precision around the outer periphery of the lens, and the manufacturing cost of the lens was high. Is this a problem similar to the one in which the elastic member of the holding device in 0 comes into contact with the outer diameter of the lens and the inner diameter of the lens barrel?In order to avoid this problem, the lens can be removed by reducing the deformation reaction force of the holding ring. There is a problem in that the position of the lens in the optical axis direction is easily shifted due to the slippage of the aluminum or tapered engagement surface. If the holding devices O and e engage the outer diameter of the lens and the inner diameter of the lens barrel, the lens is likely to be deformed by changing its curvature or misaligned in the optical axis direction. There is a problem in that if there is a gap between the diameter and the inner diameter of the lens barrel, eccentricity tends to occur. Furthermore, all of the holding devices described in J. 1 to 2 have the problem that holding the lens takes the same or more effort than the holding device shown in FIG. 1.

[Purpose of the invention]

The present invention was made in order to solve the problems of the conventional lens holding device as described above, and the lens does not wobble, deform, or become eccentric even when the temperature and humidity of the environmental conditions change. To provide a lens holding device that can hold a lens with high precision without any risk of misalignment in the optical axis direction or easy removal, and that requires no effort and is inexpensive to manufacture. .

[Structure of the invention]

The present invention provides a lens holding device in which a plastic lens is fixed to a lens barrel via a coupling member made of a plastic material, in which the holding member has a coefficient of thermal expansion and a water absorption coefficient of 7 to 1.3 times that of the plastic lens. The above object is achieved by a plastic lens holding device characterized in that it is made of a plastic material having a coefficient of thermal expansion and a coefficient of water absorption within a range.

The plastic material used for the lenses and coupling members of the present invention, whose thermal expansion coefficient and water absorption rate have the above-mentioned relationship, can be obtained by selecting the main polymeric substance and the filler. Examples are shown in the table below.

(Note) PνMA: Polymethyl methacrylate SAN
: Styrene acrylonitrile Duracon G (325: Polyacetal resin manufactured by Boli Plastic Co., Ltd. (25 wt% glass fiber) Noryl 31: Polyline enylene oxide resin manufactured by Engineering Glass Co., Ltd. As in the combination of Example 1.2, thermal expansion of the bonding member The coefficient and water absorption coefficient are 0 of the thermal expansion coefficient and water absorption coefficient of the lens.
．． If it is in the range of 7 to 1.3 times, the lens will be stably fixed to the lens barrel even if the environmental temperature and humidity change, but the coupling member will If the lens is made of a material with a coefficient of thermal expansion and water absorption as low as 7 times, but as high as 1.3 times, the lens may become detached from the connecting member due to changes in temperature or humidity, or the lens may Problems such as pressure being applied to the lens and distortion of the lens are likely to occur.

〔Example〕

Next, the present invention will be explained with reference to specific embodiments shown in FIGS. 2 and 3.

2 is a partial sectional view showing an example of the lens holding device of the present invention in a state in which a lens is held, and FIG. 3 is a perspective view showing an example of a coupling member.

In FIGS. 2 and 3, 4 is a lens & barrel, 4a is a flange, 4b is a relief notch, 5 is a coupling member, 5a
5b is an annular base portion of the coupling member, 5b is an elastic arm with claws provided on one side of the annular base portion 5a perpendicular to the optical axis, three or more of which are arranged evenly in the circumferential direction, and 5c is also provided on the other side. The elastic arm 6 with claws is a lens having a thick holding portion 6a sandwiched between a surface perpendicular to the optical axis and a surface substantially parallel to the optical axis on its outer periphery.

The coupling member 5 has an elastic arm 5b with a claw first, and the inclined surface at the tip of the claw is the flange portion 4a of the lens barrel 4.

When it is inserted into the lens barrel 4 so as to come into contact with the corner where the relief notch 4b is provided, and pushed further, the claw rides on the inner surface of the flange portion 4a and the claw-equipped elastic arm 5b is bent.
When brought into contact with the end surface of the flange portion 4a, which is the end surface of the annular base portion 5a, the claws come off the inner surface of the flange portion 4a, and the elastic arms 5b with claws recover their flexure, so that the claws hold the rear side of the flange portion 4a. Then, it is attached to the lens barrel 4.

Even if a difference in expansion occurs between the connecting member 5 and the lens barrel 4 due to changes in temperature and humidity, the flange portion 4a, which is engaged by the elastic arms 5b with claws arranged evenly in the circumferential direction, has elastic elastic arms with claws. Since the relief notch 4b is provided on the base side of the arm 5b, the claw-equipped elastic arm 5b can easily follow the deformation to absorb the difference in expansion, and therefore there is no eccentricity between the lens barrel 4 and the coupling member 5. There is no possibility that the coupling member 5 will be displaced in the optical axis direction. Further, since the claw-equipped elastic arms 5b hold the flange portion 4a with their claws, there is no fear that the coupling member 5 will come off.

The lens 6 is further inserted into the elastic arm 5b with a claw so that the corner of the thick holding portion 6a on the side perpendicular to the optical axis is brought into contact with the inclined surface of the tip of the claw of the elastic member with claw @5c of the coupling member 5. When pushed in, the coupling member 5 is attached to the coupling member 5 in the same way as the coupling member 5 was attached to the lens barrel 4. In the illustrated example, the coupling member 5 is made of the same material as the lens 6 or a material whose coefficient of thermal expansion and water absorption are in the range of 0.7 to 1.3 times that of the material of the lens 6. Therefore, even if the lens 6 is not provided with a relief part such as the relief notch 5b in the flange part 4a of the lens barrel 4, it is difficult for the lens 6 to be held by the coupling member 5 to be eccentric or skewed. Of course, there is a risk that it will lose its hold. Note that when there is a difference in thermal expansion coefficient or water absorption rate between the coupling member 5 and the lens 6 that is close to the limit of the above-mentioned range, the lens 6 also has a relief notch 4b in the flange 4a of the lens barrel 4 A relief notch may be provided. As a result, the lens 6 can be held without being eccentric or tilted, and since the holding is done by the clawed elastic arms 5c, no large force is applied to the lens 6.

As described above, the lens 6 is easily attached to the lens barrel 4, and the lens 6 may be attached to the coupling member 5 first, and then the coupling member 5 is attached to the lens barrel 4. The engaging surfaces of the lens barrel 4, coupling member 5, and lens 6, which provide mounting accuracy, are all flat circumferential surfaces perpendicular to the optical axis, so they can be formed easily and accurately. , easy and accurate installation.

〔Effect of the invention〕

As described above, the lens holding device of the present invention has the following features:
There is no risk of the lens shaking or coming off, and even if the environmental temperature and humidity change, there will be no eccentricity, misalignment in the optical axis direction, or excessive force being applied to the lens. ,
It can be easily and precisely attached to the lens barrel, and the overall manufacturing cost is lower than that of the conventional method, which is an excellent advantage.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing an example of a conventional lens holding device.
Fig. 2 is a partial sectional view showing an example of the lens holding device of the present invention in a state in which a lens is held, and Fig. 3 is a partial cross-sectional view of a lens holding device according to the present invention; Part, 3
... Presser ring, 5... Connecting member, 5a... Annular base body, 5b, 5C... Elastic arm with claw. Patent applicant Konishiroku Photo Industry Co., Ltd.

Claims (1)

[Scope of Claims] 1. A lens holding device in which a plastic lens is fixed to a lens barrel via a coupling member made of a plastic material, wherein the holding member has a coefficient of thermal expansion and a water absorption coefficient of 0.1 to 1 of the coefficient of thermal expansion and water absorption of the plastic lens. A plastic lens holding device characterized in that it is formed of a plastic material having a coefficient of thermal expansion and a coefficient of water absorption in the range of 3 times. 2. The plastic lens holding device according to claim 1, wherein the coupling member has a coupling portion that elastically couples with the lens barrel. Orthopedics