JPS635734B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens holding device that holds a lens within a lens frame, and in particular, a lens holding device that holds a plastic lens with weak temperature resistance within the lens frame so that its shape does not change even when the temperature changes. The object of the present invention is to provide a lens system that maintains its lens performance and has strong temperature resistance, and to expand the temperature range in which plastic lenses and other non-temperature resistant lenses can be used.

Now, FIG. 1a describes the prior art.

When fixing the plastic lens 7 into the lens frame 2 using the conventional technique, the lens 7 is first abutted against the lens frame body attachment part 4 through the lens frame fitting part 5. Next, screw in the presser ring 1 which has a presser ring threaded portion 6 around it that engages with the lens frame threaded portion 3, and
As shown in FIG. b, the lens 7 can be fixed into the lens frame 2 by holding the lens holding ring contact part 8.

Now, when the lens 7 and the lens frame 2 assembled at room temperature are brought to a high temperature state, as shown in FIG. Since the coefficient of linear expansion is larger than the linear expansion coefficient for molding, the clearance of the lens frame fitting portion 5 becomes small. Furthermore, the location where this effect is most noticeable is shown in Figure 1b.
In the lens holding ring abutment part 8 shown in the figure, this part already has zero clearance when assembled at room temperature, so at high temperatures the difference in linear expansion coefficient between the lens 7 and the holding ring 1 directly changes the surface shape. will have an impact on (The surface of the lens 7 is depressed by the lens holding ring 1 at the lens holding ring contact portion 8, and the lens is regulated to a zero clearance state by the inner diameter of the holding ring 1.) In other words, as the temperature increases, The lens begins to expand in the radial direction.

However, for the reasons mentioned above, this radial deformation is restricted and thermal stress is generated inside the lens. Therefore, in the next step, the lens begins to deform in the direction of the optical axis, which is not subject to any restrictions, in order to eliminate this thermal stress. Therefore, considering the cross section in the axial direction including the optical axis of the lens 7 (see the explanatory diagram in Fig. 1c), since the length of the chord AB is regulated by the presser ring 1, the expansion of the arc AB is concentrated. As a result, the radius of curvature becomes smaller.

Now, the length of the arc at room temperature is A′B′, which is t℃ from room temperature.
The arc length at high temperature is AB, and the linear expansion coefficient of the lens is α.
Then, it can be approximated by A′B′≒AB・(1+αt).

Next, when the lens 7 and lens frame 2 assembled at room temperature are brought to a low temperature as shown in FIG. Since the coefficient of linear expansion is larger than the linear expansion coefficient of the material from which the ring 1 is molded, the lens 7 tends to contract more than the lens frame 2 and the presser ring 1 as the temperature decreases.

However, as mentioned above in the high-temperature state, the outer periphery of the lens 7 is restricted by the lens presser ring abutment part 8 of the presser ring 1, so the lens 7 will not shrink more than the presser ring 1. This means that it cannot be contracted.
Therefore, thermal stress will occur inside the lens 7.

In the next step, the lens 7 begins to deform in the direction of the optical axis, which is not subject to any restrictions, in order to eliminate this thermal stress. Therefore, if we consider the cross section of the lens 7 in the direction including the optical axis (see the explanatory diagram in Fig. 1 d), the string
Since the length of AB is regulated by presser ring 1, the arc
Contraction concentrates on AB, and as a result, the radius of curvature becomes larger.

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 material of lens 7 is α, then A'B'≒AB・( 1−αt).

For the reasons mentioned above, when a plastic lens is fixed in the lens frame 2 using the conventional technology, the radius of curvature changes with temperature changes (it becomes smaller at high temperatures and becomes larger at low temperatures), so it This resulted in a large shift in the focus position and worsening of various aberrations.

Further, as shown in FIG. 1e, an alignment member 24 is provided between at least two adjacent lenses 21 and 22 at the outer peripheral edge for the purpose of reducing frictional resistance.
A method of obtaining a composite lens that does not cause misalignment of the centers of lenses 21 and 22 by arranging
138606), but this only reduces the friction between the two lenses 21 and 22, so the outer shape of the lens is limited by the inner diameter of the holding ring 25 or the lens holding member. In the end, even if the plastic lens is fixed in the lens holding member 23 using this method, it is not possible to prevent the radius of curvature of the plastic lens from changing due to temperature changes, and the above-mentioned shift in focus position due to temperature, Alternatively, this may lead to worsening of aberrations.

There is also a "lens barrel" described in Japanese Utility Model Application Publication No. 49-11740, but this has a structure in which the lens surface is held down via an O-ring made of an elastic material, and this does not meet the purpose of the present application. is an invention of a different technical idea.

On the other hand, the following is a consideration of the conventional technology regarding the optical element fixing member.

1. ``Lens holding device'' disclosed in Japanese Utility Model Publication No. 53-40254 (1) The engaging protrusion of the pressure contact member must have contradictory properties of elasticity and rigidity to satisfy the lens performance. In order to smoothly assemble the lens using pressing force, it is difficult to select the material and set the strength.

(2) Due to the nature (above) of the engaging protrusions of the pressure welding part, it is difficult to provide many protrusions.
Therefore, since it must be constructed with a small number of protrusions, the force that presses the lens becomes partially uneven, and the lens surface shape, eccentricity of the lens optical axis,
It is not possible to fully guarantee against inclination.

(3) If the pressure contact member is made of plastic, even if its function is satisfactory at room temperature, there is a high risk that it will loosen due to stress relaxation due to temperature changes.

(4) When the number of engaging protrusions of the pressure contact member is increased, the number of man-hours required for machining the grooves that fit into each protrusion increases.

(5) When an elastic body is used, a difference is likely to occur in the pressing force of the lens between the part with the engaging protrusion and the part without it, making it difficult to set the pressing force.

(6) Assuming that a plastic lens is used for the lens, the low mechanical strength of the lens material makes it susceptible to the pressing force of the pressing member, which, combined with the unevenness of the pressing force, makes it difficult to fix the plastic lens. is not appropriate.

(7) From the above, it cannot be used as a suitable lens holding device for lens systems that require high performance, including plastic lenses, and/or when the usage environment changes significantly.

2 Other Prior Art (1) Caulking Method The lens 28 is fixed to the lens frame 26 by tilting the claw 27 provided on the lens frame 26 using the known method shown in FIG. If this happens, the lens 28 will be deformed due to the heat generated by crimping and the amount of crimping force, and not only will it be unable to maintain its surface shape, but it may also be damaged.

Therefore, the present invention proposes a lens holding device that solves the drawbacks of the conventional lens holding devices described above and can meet the above-mentioned demands.
Each embodiment of the lens holding device of the present invention will be specifically described below with reference to the drawings.

FIG. 2 shows a first embodiment of the present invention.
0 is a lens frame, 31 is a lens mounting part provided inside the lens frame 30, and 32 is a lens fitting part. In addition to the annular embodiment, it is also possible to construct the lens body with a plurality of partially annular lens body attachment pieces and lens fitting pieces (not shown).

33 is a threaded portion of a retaining ring 34 provided on the inner wall of the lens frame 30.

Further, an elastic body 35 constituting an elastic portion is fixed to the presser ring 34 on the side of the contact surface with a self-deformable absorbing lens 40, which will be described later.

The illustrated embodiment shows a case in which it is constructed by lining an elastic member such as rubber.

Furthermore, regarding the material of the presser ring 34, the material of the lens frame 30 is
Similarly, when the lens frame 30 is made of synthetic resin, it is not limited to metal materials, and may be made of synthetic resin as well.A specific example thereof is carbon fiber with high elastic modulus, etc. The presser ring 34 is formed of a synthetic resin material containing
The elastic body 35 is made of ABS resin or the like having a low elastic modulus, and the two are integrated by double molding or insert molding.

Next, the self-deformation absorbing lens 40 is made of synthetic resin, and has a deformation absorbing portion along the outer periphery of the plastic lens body 41 that is thinner than the minimum thickness of the lens body 41 and has a V-shaped cross section. 42 is provided, and a lens frame fitting 43 having an inverted trapezoidal cross section is provided on the outer periphery of the deformation absorbing portion 42.

Now, the self-deforming absorption lens 40 is inserted into the lens fitting part 32 of the lens frame 30, fitted into the lens frame fitting part 43 on the outer periphery, and then dropped into the lens barrel fitting part 31. By screwing the ring 34 onto the threaded portion 33, a deformation absorbing portion 42 provided in the self-deforming absorbing lens 40 itself is interposed between the plastic lens body 41 and the lens fitting portion 32, and the plastic lens body 41 and the holding ring 34 are interposed. The self-deformable absorption lens 40 can be fixed within the lens frame 30 with an elastic body 35 interposed therebetween.

When a temperature change is applied to the plastic lens body 41 held in this configuration, the plastic lens body 41 expands and contracts as the temperature changes repeatedly, and thermal stress generated in the radial direction at high temperatures is absorbed by the deformation absorbing portion It can be absorbed by the elastic deformation of the lens barrel 3 of the lens frame 30.
The thermal stress in the thrust direction in one part is caused by the presser ring 3.
This can be absorbed by the elastic deformation of the elastic body 35 of No. 4, and the elastic deformation action of the elastic body 35 promotes the elastic deformation effect of the deformation absorbing portion 42.

Therefore, in the lens holding device according to the first embodiment of the lens holding device of the present invention, when storing the plastic lens body 41 in the lens frame 30, the plastic lens body 41 has a plastic lens body 4 on its outer periphery.
The self-deformation absorbing lens 40 is provided with a deformation absorbing portion 42 formed with a thickness thinner than the minimum thickness of the self-deformation absorbing lens 40.
The retaining ring 34 that presses and fixes the lens into the lens fitting part 32 of the lens frame 30 is configured by providing an elastic body 35 at the contact part with the self-deformation absorbing lens 40, so that the following effects can be obtained. .

First, when a cold-heat change occurs in the plastic lens body 41, thermal stress is generated in the radial direction due to thermal expansion of the plastic lens body 41.
Thermal stress is absorbed by the elastic deformation in step 2, and changes in the radius of curvature of the lens can be prevented. Therefore, there is no need to particularly increase the fitting clearance between the plastic lens body 41 and the lens frame 30, and the setting can be made as before, so that the lens performance can be maintained at the same level as before.

Further, the presser ring 34 has an elastic body 35 attached to the lens pressing portion.
, it is possible to follow the expansion and contraction in the thrust direction due to temperature changes in the holding ring contact part of the plastic lens body 41, and in the case of expansion, it absorbs the thermal stress generated in the thrust direction. However, it can help prevent changes in the radius of curvature of the plastic lens. In addition, since the elastic body 35 acts in a direction that offsets the stress relaxation caused by the clamping ring 34 of the plastic lens body 41, loosening of the clamping ring 34 can be prevented, and the lens will not wobble for a long time. can be retained. This momentum can be used to expand the range of environments in which plastic cleansers can be used.

Next, in the second embodiment shown in the third figure, the configurations of the lens frame 30, presser ring 34, and elastic body 35 are the same as in the first embodiment, and the self-deforming absorption lens 40 accommodated therein is
have different configurations.

That is, the self-deformation absorption lens 40 is constructed by providing the deformation absorption part 42 in the first embodiment by providing an annular foamed part 44 made of a foam layer on the outer periphery of a plastic lens body 41.

However, the function and effect of the deformation absorbing part 42 can be achieved only by providing the foamed part 44;
In the illustrated embodiment, an annular lens frame fitting part 45 is provided on the outer periphery of the foamed part 44.

In addition, the plastic lens body 41 and the foamed part 4
4, and the foamed part 44 and the lens frame fitting part 45 are connected by a lens anchor 46 provided on the outer periphery of the plastic lens body 41 and a fitting part anchor 47 provided on the inner periphery of the lens frame fitting part 45, respectively; The foamed portion 44 can be formed between the plastic lens body 41 and the lens frame fitting portion 45 by foam molding.

Further, a skin layer 48 is provided on the outer skin of the foamed portion 44, but this is not necessarily formed during the molding process of the foamed portion 44, but it may be actively formed or, conversely, it may be formed. Sometimes it is done without.

Note that the foamed portion 4 of the illustrated self-deformable absorption lens 40
4 shows only the case where it is provided in an annular shape along the outer periphery of the lens body, but it is also possible to implement this with a plurality of partially annular foam pieces (not shown), and the elastic deformation effect of the foam part 44 can be further enhanced. It can be improved.

By storing and holding the self-deforming absorption lens 40 having the above structure in the lens frame 30 in the same manner as in the first embodiment, the lens holding device of the present invention can be constructed. The self-deformation absorbing lens 40 includes a deformation absorbing portion made of a foamed portion 44 provided on the outer periphery of the main body 41.
It is press-fixed into the lens frame 30 by a retaining ring 34 provided with an elastic body 35, and exhibits the following effects.

First, when a cold-heat change occurs in the plastic lens body 41, the thermal stress in the radial direction caused by the thermal expansion is absorbed by the elastic deformation of the foamed part 44, and the thermal stress in the thrust direction of the lens fixing part is suppressed. This can be absorbed by the elastic body 35 disposed on the ring 34, and even if temperature changes are applied to the plastic lens, changes in the radius of curvature of the lens can be prevented.

In addition, a plastic lens body 41 and a mirror frame 30 are also included.
The fitting clearance with the plastic lens body 41 can be set to zero or a value close to it due to the elasticity of the foamed part 44 arranged on the outer periphery of the plastic lens body 41.
Misalignment and shift with respect to the optical axis of the lens can be reduced, and lens performance can therefore be improved.

Furthermore, even during long-term use, the elasticity of the foamed portion 44 disposed on the outer periphery of the plastic lens body 41 and the elasticity of the elastic body 35 disposed on the presser ring 34 prevent the phenomenon of stress relaxation at the plastic lens fixing part. Since they cancel each other out, it is possible to prevent the phenomenon of loosening of the presser ring 34 and also to prevent the occurrence of rattling of the lens.

As is clear from the above description, according to the present invention, the lens body is supported by a lens deformation absorbing portion provided on the outer periphery of the lens body that is easily deformable in the radial direction and has no pressing force in the optical axis direction. Therefore, the lens deformation absorbing portion absorbs expansion and contraction of the lens body in the radial direction due to temperature changes.
In addition, since the holding ring contact surface of the lens frame fitting part provided on the outside of the lens deformation absorbing part is pressed by the holding ring via an elastic body, this elastic body causes the lens frame fitting part to change due to temperature changes. The expansion and contraction in the thrust direction is absorbed.

Therefore, it is possible to prevent changes in the radius of curvature of the lens body caused by changes in temperature of the lens fixed within the lens frame.

[Brief explanation of the drawing]

Figures 1a to 1f are for explaining a conventional lens holding device. Figure 1a is a sectional view, Figure 1b is an enlarged view of the same part, and Figures 1c and d are lenses that change due to temperature changes. An explanatory diagram showing the thermal stress in Figure 1 e and f are the first
Cross-sectional view showing a lens holding device different from that shown in Figure a, 2nd
3 and 3 show embodiments of the lens holding device of the present invention, FIG. 2 is a side sectional view showing the first embodiment, FIG. 3a is a side sectional view showing the second embodiment, and FIG. FIG. 3b is a partial front view of the self-deforming absorption lens in the same example. 30...Mirror frame, 31...Lens barrel attachment part, 32...
... Lens fitting part, 33 ... Threaded part, 34 ... Pressing ring, 35 ... Elastic body, 40 ... Self-deformation absorbing lens, 41 ... Plastic lens body, 42 ...
Deformation absorption part, 43, 45... Lens frame fitting part, 44...
...Foamed part, 46... Lens anchor, 47... Fitting part anchor, 48... Skin layer.

Claims (1)

[Scope of Claims] 1. A lens holding device that presses and fixes a lens housed in a lens fitting part in a lens frame to a fixing member in the lens frame using a holding ring, which comprises: a lens body and a lens provided on the outer periphery of the lens body; a lens deformation absorbing part that is easily deformable; and a lens deformation absorbing part provided on the outer periphery of the absorbing part, with the peripheral surface serving as a fitting part to the lens frame, one side surface serving as a contact surface for the fixing member, and the other side surface serving as a holding ring. comprising a lens integrally or integrally formed with a lens frame fitting portion serving as an abutment surface, and a presser ring attached to the lens frame so as to press the presser ring abutment surface of the lens via an elastic body, A lens holding device characterized in that the expansion and contraction of the lens body in the radial direction due to temperature changes is absorbed by the lens deformation absorbing portion, and the expansion and contraction of the lens frame fitting portion in the thrust direction is absorbed by the elastic body.