JPS6315565B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lens holding device, and more particularly to a lens holding device that stores a lens body within a lens frame and uses a presser ring to fix the lens body within the lens frame in the radial and axial directions. Conventionally, when a lens, for example, a plastic lens 7, is to be mounted in a lens frame 2, the back outer peripheral edge 7a of the plastic lens 7 is placed on the lens frame body 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 while being in contact with each other, 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. While doing so, screw the presser ring 1 into the inside of the lens frame 2, and press the contact edge 1a formed on the inner peripheral edge of the presser ring 1, which contacts the plastic lens 7, with the outer peripheral edge 7b on the front side of the plastic lens 7. plastic cleanse 7
is constructed by fixing it 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 coefficient of linear expansion of the molding material of the plastic lens 7 will be the same as that of the lens frame 2. and is larger than the linear expansion coefficient of the molding material of the presser 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 (first
(see the enlarged view shown in Figure b), the clearance in this part is already zero when it is assembled at room temperature, and in the high temperature atmosphere, the line between the molding material of the lens 7 and the presser ring 1 is The difference in expansion coefficient 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 of the plastic lens 7 in the axial direction including the optical axis, since the length of the chord AB in FIG. becomes smaller. Now, the length of the arc at room temperature is AB, and it is t℃ below room temperature.
When the length of the arc at high temperature is A'B' and the linear expansion coefficient of the plastic lens 7 is α, 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 linear expansion coefficients of the plastic lens 7, the lens frame 2, and the holding ring 1 are different, as described above. Therefore, as the temperature decreases, the plastic lens 7 contracts more than the lens frame 2 and the presser ring 1, and tends to shrink more than the lens frame 2 and the presser ring 1.
In this case as well, the outer peripheral edge 7b on the front side of the plastic lens 7, which is fixed by pressure contact with the abutting edge 1a of the presser ring 1, is restricted, so that the shrinkage of the plastic lens 7 is prevented as in the case at high temperatures. Presser ring 1
As a result, thermal stress is generated inside the plastic lens 7, and this thermal stress is concentrated in the optical axis direction of the plastic lens 7, which is not restricted by the presser ring 1, causing the plastic lens 7 to shrink. 7 in the optical axis direction. Therefore, the plastic lens 7 shown in FIG.
Considering the cross section in the axial direction including the optical axis of
The contraction concentrates on the area, and as a result, the radius of curvature increases. Now, the length of the arc at room temperature is AB, and it is t℃ below room temperature.
If the length of the arc at low temperature is A'B', and the coefficient of linear expansion of the molding material of the plastic lens 7 is α, then A'B'≈AB·(1−αt) is approximated. Therefore, from the above, Plastic Cleanse 7
When the plastic lens 7 is mounted in a lens frame 2 having a conventional structure with the presser ring 1, it is obvious that the radius of curvature of the plastic lens 7 changes due to temperature changes, that is, it becomes smaller at high temperatures and becomes larger at low temperatures. In comparison, it can be seen that the focus position shifts significantly and various aberrations worsen. In addition, in the conventional lens and lens frame configuration, as shown in FIG. 1e, the lens holding member 23
At least two lenses 2 in the lens fitting part 26 of
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 presser 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 that occur due to 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. There was a strong need for the development of appropriate countermeasures. SUMMARY OF THE INVENTION The object of the present invention is to overcome the above-mentioned drawbacks and to provide a lens holding device which provides accurate radial positioning during assembly and which holds a plastic lens in a lens frame without changing its shape in the event of temperature changes. The aim is to widen the operating temperature range of plastic lenses, which have poor temperature resistance. Embodiments and drawings illustrating the present invention will be described. FIGS. 2a and 2b show a first embodiment of the lens holding device of the present invention, in which a lens holding ring 33 is screwed into a lens frame threaded portion 32 provided on the inner surface of a lens frame 31. FIG. Mirror frame 31
A thrust beam 37 is formed radially inward to position the plastic lens 36 between it and the retaining ring 33 in the axial direction. The position of the presser ring 33 is determined by the presser ring body attaching portion 34, and the lens 36 is held by the elasticity of the thrust beam 37. A radial beam 38 is further formed on the lens frame 31, and the lens 36 is positioned in the radial direction by the radial inner surface of the radial beam 38. As shown in FIG. 2b, the radial beam 38 and the thrust beam 37 are each formed as a plurality of protrusions spaced apart from each other, and furthermore, they are constructed so that they do not overlap each other in the axial direction. By this,
When forming the lens frame 31, there is no need to create a complicated shape such as an undercut. Furthermore, radial beam 3
8. It becomes easy to set the rigidity of the thrust beam 37 to a required value. During assembly, the axial position of the plastic lens 36 is determined by the end surface 35 of the presser ring 33 that is in contact with the presser ring barrel attachment portion 34. The radial position of lens 36 is determined by the radial inner surface of radial beam 38. The radial beam 38 and the outer circumferential surface of the lens 36 are brought into contact with each other with a slight elasticity to ensure accurate positioning in the radial direction during assembly. When the lens frame 31 having the plastic lens 36 reaches a high temperature, the lens 36 expands. 1st
In the known example shown in the figure, the outer circumferential surface of the lens directly contacts the inner surface of the lens frame, causing deformation of the lens, but according to the present invention, the outer circumferential surface of one side of the lens 36 is supported by the radial beam 38. Thermal expansion of the lens 36 is absorbed by the elastic deformation of the radial beam 38, and no deformation (change in radius of curvature, etc.) of the lens 36 occurs. The expansion of the lens 36 in the axial direction is absorbed by the elastic deformation of the thrust beam 37. When it is necessary to reduce the elasticity of the radial beam 38 and thrust beam 37, radial grooves 40 of the required dimensions,
A thrust groove 39 is formed. When the lens system is brought to a low temperature, the lens 36 contracts, but the radial beam 38 and thrust beam 38 during assembly
The shrinkage is absorbed by the elasticity of the lens 36, and no wobbling occurs in the lens 36. Usually, the lens frame 31 is made of a synthetic resin material with high rigidity and low elasticity. If the required elasticity values of the thrust beams 37 and radial beams 38 are different from the characteristics of the material of the lens frame 31, the materials of the beams 37 and 38 and the material of the lens frame 31 are made of different materials using a known double molding method. It can be integrally molded. FIG. 3 shows a second embodiment of the invention. Mirror frame 3
Each part formed in 1 is the same as that in FIG. 2 and is indicated by the same reference numeral, and detailed explanation will be omitted. In the case of FIG. 3, a peripheral parallel portion 42 is formed on the plastic lens 41 to increase the surface of contact with the thrust beam 37 and ensure positioning in the axial direction. The thrust beam 37 is slightly elastically changed during assembly to ensure lens retention. In the case of FIG. 3, the thrust beam 37 may be replaced by a rigid shank portion shown in FIG. 1 for positioning in the axial direction, and the holding ring 33 may have a structure in which it does not contact the ring shank portion 34. Since the width of the flat portion 42 of the lens 41 is small, the dimensional change in the axial direction due to thermal expansion and contraction is extremely small, and the change in the radius of curvature of the lens 41 due to the loosening of the attachment can be ignored. lens 4
Thermal expansion and contraction in the radial direction of 1 is absorbed by the elasticity of the radial beam 38. Figures 4 and 5 show the third lens holding device of the present invention.
An example is shown below. Similar parts or parts are designated by the same reference numerals as in FIG. In this embodiment, an inclined beam 45 is used in place of the thrust beam 37 shown in FIGS.
The lens 41 is positioned in the axial direction by contacting the flat portion 46 of the lens 41. As in the previous embodiment, the inclined beam 45 is elastically deformed during assembly to provide axial holding force. In the case of this embodiment, the elastic deformation dimension is made larger than that of the upright thrust beam 37 shown in FIGS.
Lens holding power can be increased. The function of the thrust beam 38 is similar to the example shown in FIGS. 2 and 3. The example in FIG. 4 shows an example in which the thrust beam 38 and the inclined beam 45 are formed as the same protrusion, and are formed as the entire circumference or a plurality of protrusions as required. Slanted beam 45
Grooves 47 can also be formed to adjust the elasticity of the material. In FIG. 5, the radial beam 38 and the inclined beam 45 are separately formed as protruding parts that protrude from the inner surface of the lens frame 31. In FIG. In this case, the radial beam 38 and the inclined beam 45
are alternately protruded from the inner surface of the lens frame 31 when viewed in the circumferential direction, and arranged so as not to overlap each other when viewed in the axial direction. FIG. 6 shows another embodiment of the lens holding device of the present invention. Similar parts or components are indicated by the same reference numerals as in FIGS. 2 and 3. In the example shown in FIG. 6, a lens peripheral tapered portion 52 is provided at the outer peripheral edge of the plastic lens 51, and an inclined radial beam 53 has the same taper as the tapered portion 52.
Position the plastic lens 51 in the radial direction by pressing it against the plastic lens 51. The positioning of the lens 51 in the axial direction is performed by the thrust beam 37, as in the previous example. In the example shown in FIG. 6, the inclined radial beam 53 is integrally formed with the thrust beam 37 and projected from the inner surface of the lens frame 31, but it can be formed as a separate protruding part as in the previous example. . When the lens frame with the shape shown in Figure 3 is made of polycarbonate, and the radial beam and thrust beam are integrally molded using ABS resin using the double molding method, changes in the radius of curvature due to temperature changes are determined by the conventional fixing method. The table below shows the experimental results compared with the lens according to Numbers indicate radius of curvature, rmm.

【table】

[Table] According to the present invention, by forming a radial beam that elastically deforms in the radial direction and a thrust beam that elastically deforms in the axial direction within the lens frame, the shape of the lens body changes due to temperature changes. This makes it possible to improve the temperature resistance of the lens, without impairing the accuracy of positioning in the radial and axial directions during assembly. The present invention was developed for use with plastic lenses with a large coefficient of thermal expansion, but it can be used to accurately correct parts such as glass lenses with a thin center wall, which are prone to distortion and deformation when fixed with conventional retaining rings. It is suitable for use as a holding device, and since the mounting is performed using a predetermined elastic holding method, accurate positioning can be achieved without causing deformation. When assembled at room temperature, by assembling radial beam thrust beams, especially inclined beams that play the role of thrust beams, with a predetermined elastic deformation, the positioning in the axial and radial direction becomes accurate, and the gap during assembly is reduced. becomes unnecessary. Furthermore, there is no loosening or rattling during shrinkage at low temperatures. If the mirror frame, radial beam, and thrust beam are made of separate materials and integrally molded using a double molding method, it becomes possible to set the rigidity of the mirror frame and the elasticity of each beam to the desired values. . If necessary, only the radial beam can be made elastically deformable, and the axial direction can be kept rigid.

[Brief explanation of the drawing]

Figure 1 shows the prior art, Figure 1a is a cross-sectional view of a part of the lens frame and lens, Figure 1b is an enlarged view of part A in Figure 1, and Figure 1c is the curvature when the lens expands. FIG. 1 d is a diagram showing changes in the radius of curvature when the lens contracts. FIG. 1 e is a sectional view of the lens holding device with an alignment member inserted. FIG. A partial sectional view of a lens frame according to a first embodiment of the lens holding device, FIG. 2b is a view from A in FIG. 2, and FIGS. 3 to 6 are partial sectional views showing other embodiments of the present invention. It is a diagram. 1, 25, 33... Holding ring, 2, 23, 34... Lens frame, 3, 32... Internal screw, 4... Trunked part, 5... Fitting part, 7, 21, 22, 36, 41, 51... Plastic Lens, 37... Thrust beam, 38... Radial beam, 39, 40, 47... Groove, 45... Inclined beam, 5
3... Inclined radial beam.

Claims (1)

[Scope of Claims] 1. A lens holding device for storing a lens in a lens frame and fixing it using a presser ring, comprising: a radial beam that is elastically deformable in the radial direction along the inner circumference of the lens frame; Multiple elastically deformable thrust beams are installed alternately,
A lens holding device characterized in that one side of the lens is abutted and held by a radial beam and a thrust beam, and the other side of the lens is pressed by the presser ring. 2. The lens holding device according to claim 1, wherein the elastically deformable beam is provided with a groove at its protruding end. 3. The lens frame is made of synthetic resin, and the elastically deformable beam is made of a synthetic resin different from that of the mirror frame, and is integrally molded by a double molding method.
Lens holding device as described in section. 4. The lens holding device according to claim 1, wherein said lens is a plastic lens. 5. The lens holding device according to claim 1, wherein the lens is provided with a flat portion supported by an elastically deformable beam or a presser ring. 6. A lens holding device that stores a lens in a lens frame and fixes it using a retainer ring, which includes a radial beam that can be elastically deformed in the radial direction and a slope that can be elastically deformed in the thrust direction along the inner circumference of the lens frame. A lens holding device comprising a plurality of projecting beams, one side of the lens is abutted and held by a radial beam and an inclined beam, and the other side of the lens is pressed by the holding ring. . 7. The lens holding device according to claim 6, wherein the elastically deformable beam is provided with a groove at its protruding end. 8. The lens holding device according to claim 6, wherein the radial beams and the thrust beams or the inclined beams are arranged alternately along the inner peripheral direction of the lens frame. 9. The lens holding device according to claim 6, wherein the radial beam and the thrust beam or the inclined beam are each formed from the same protrusion. 10. The lens holding device according to claim 6, wherein the lens frame is made of synthetic resin, and the elastically deformable beam is made of a different synthetic resin than the lens frame and is integrally molded by a double molding method. 11. The lens holding device according to claim 6, wherein said lens comprises a plastic lens. 12. The lens holding device according to claim 6, wherein the lens is provided with a flat portion supported by an elastically deformable beam or a presser ring.