JPH0324645B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a plastic lens holding device, and more particularly to a plastic lens holding device 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. . 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 for 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 machined with the support tube, and then insert a presser ring 4 with a thread turned around the circumference, also on the inner side. A screw 5 is screwed into the support cylinder 1 which is turned into a part, and the support cylinder 1 is held by being pressed against the corner 3a. This presser ring 4 is the support tube 1
and the threaded portion 5, and are held in the support tube 1 while being press-fitted to the lens 2. Further, the inner diameter of the fitting part 6 of the barreled part 3 is made slightly larger than the outer diameter of the lens 2. However, this difference between the inner diameter of the barreled part 3 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 this lens 2
Assuming that the material of is glass, even if the lens system shown in FIG. 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, so if the lens system shown in Figure 1A is brought to a high temperature state, the lens 2 is larger than the inner diameter of the barreled portion 3 of the support cylinder 1.

[Table] FIG. 1B is a diagram showing the relative displacement of the inner and outer diameters of the support tube 1 and the lens 2 depending on the above-mentioned temperatures. 1st
In FIG. B, the solid line shows the 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. That is, looking at Figure 1B, the outer diameter of the lens at room temperature is
As the temperature increases, D _L and the barreled inner diameter D _K become
If there are no restrictions, the lens 2 will expand in the direction of the optical axis and in the direction orthogonal to it to have an outer diameter D′ _L , and
The inner diameter of the barreled portion 3 is D' _K . However, in reality, even if the lens 2 in Fig. 1A tries to expand, it is held down by the barreled part 3, and as shown in Fig. 1B, the outer diameter D _L of the lens 2 is the free expansion of the outer diameter D' _L . It becomes smaller than the lens and has an outer diameter of D'' _L.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 out and the outer diameter becomes D''L. Figure 1B
As shown in Fig. 1, the inner diameter _DK of the barreled portion 3 becomes an inner diameter D'' _K which is larger than the inner diameter D' _K . Therefore, if the lens 2 and the support tube 1 in Fig. 1A are placed in a high temperature state, the inner diameter D''K in Fig. 1B is larger than the inner diameter D''K.
As shown in the figure, compressive stress is generated at the lens inner diameter D' _L and tensile stress is generated at the support cylinder outer diameter D' _K , and the mutual expansion is balanced, resulting in the lens outer diameter D'' _L and the support cylinder outer diameter D'' _K. and,
This stress causes the thinnest part of the plastic lens, that is, the outer periphery of the positive lens 2, to
If the lens is a negative lens, thin wrinkles or undulations will occur on the lens surface at the center, and the radius of curvature will change greatly, resulting in a large change in aberration characteristics and changes in imaging characteristics. When both ends are fixed, if compressive stress is generated, buckling may occur in a negative lens with a thin center thickness. In addition, due to these effects, the optical axis of the lens system may shift, the lens may become eccentric or tilted, or the distance between lenses may change.
There was a risk that lens performance would deteriorate. These things have been one of the major drawbacks of using plastic lenses. The present invention eliminates the above-mentioned drawbacks and eliminates the optical disturbance caused by the difference in linear expansion coefficient between the lens and the supporting tube made of different materials, especially the deformation of the lens at high temperatures, when using a plastic lens. An elastic member is provided between the lens and the barreled part of the support tube, between the lens and the presser member, and at the fitting part of the lens and the support tube, so that the optical axis direction and It is an object of the present invention to provide a holding device that can be removed by absorbing dimensional changes in a direction perpendicular to the holding device. The present invention provides a holding device for holding a plastic lens, in which a barreled portion formed in a lens support tube that holds the plastic lens, a presser member that presses the lens, and a space between the barreled portion and the presser member. and an interposed elastic member made of a material slightly softer than the hardness of the lens, so that the elastic member absorbs deformation in the optical axis direction of the lens and in a direction perpendicular thereto due to expansion or contraction of the lens. The feature is that the lens is held by pressing it. Hereinafter, the present invention will be explained in detail with reference to the drawings. Note that the same reference numerals are used for the same parts in each figure. FIG. 2A is a longitudinal sectional view of the first embodiment of the present invention. A deformation absorbing material 14 made of an elastic material whose hardness is slightly softer than that of the lens 13 is interposed between the barreled portion 12 of the support tube 11 and the plastic lens 13 to absorb a portion of the inside of the support tube 11 and the outer periphery of the presser ring 15. By screwing together the threaded portion 16 which has been turned in a similar manner, the holding ring 15 holds the lens 13 in pressure contact with the deformation absorbing material 14, and the holding ring 15 itself is also locked. Note that a material with strong elasticity is selected for the material of the deformation absorbing material 14. FIG. 2B is a longitudinal sectional view showing the shape of the deformation absorbing material 14 shown in FIG. 2A in a free state. By forming a somewhat acute angle α and pressing the lens 13 against the deformation absorbing material 14 using the holding ring 15, it is made into a right-angled shape as shown in FIG. 2C.
Now, when the lens system shown in FIG. 2A is brought to a high temperature state, compressive stress is applied to the lens 13 due to the difference between the coefficient of linear expansion of the material of the support tube 11 and the material of the plastic lens 13. As a result, the thin portion of the lens 13 tends to be deformed. However, since the deformation absorbing material 14 interposed between the lens 13 and the barreled portion 12 first deforms in the optical axis direction and the direction orthogonal thereto, the lens 13
Its own deformation can be prevented. Furthermore, when the lens system shown in FIG. 2 is brought to a low temperature, the linear expansion coefficient of the material of the lens 13 is larger than that of the support tube 11, which causes the lens 13 to contract, contrary to the case at a high temperature. is larger than the contraction of the support tube 11, and a play is likely to occur between the lens 13 and the support tube 11. However, the lens 13 is pressed against the deformation absorbing material 14, and the deformation absorbing material 14 in FIG.
Since the acute angle α is changed to a right angle as shown in the deformation absorbing material 14 shown in FIG. Therefore, even if the lens system is brought to a low temperature state, the lens 13 is held down by the holding ring 15 by the deformation absorbing material 14, so that the lens 13
There is no backlash between the support tube 11 and the support tube 11. In this way, deformation of the lens due to temperature changes is suppressed, and its optical performance is maintained well. FIG. 2D is a longitudinal sectional view of a modification of the first embodiment. In this example, the retaining ring 15 presses the deformation absorbing material 14 between the lens 13 and the retaining ring 15 via a threaded portion 16 turned into a part of the inside of the support tube 11 while sandwiching the deformation absorbing material 14 between the lens 13 and the retaining ring 15. Even in this manner, the same effect as in FIG. 2A can be obtained. 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 embodiments, the present invention (a) provides a deformation absorbing material made of a highly elastic material between the lens and the support tube, so that it can be used in the vicinity of the minimum thickness of the lens. Deformation occurs, and the Newton ring of the lens before deformation is 2~
However, as a result of deformation, the number of Newton rings becomes 10 or more, or the number of Newton rings deforms to such an extent that it does not form a ring shape, whereas according to the present invention, there are only 2 to 3 Newton rings in the lens before deformation. I was able to keep three. (b) Holding the lens in the support tube by applying deformation to the deformation absorbing material made from a highly elastic material eliminates the looseness between the lens and the support tube that was likely to occur in the past. was completed. Therefore, partial blur caused in the lens system due to lens play,
It was possible to prevent image deterioration due to deterioration of taste torsion and other aberrations.

[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 line showing the relative displacement of the inner and outer diameters of the support tube and lens due to temperature in Figure 1A. 2A is a vertical sectional view of the first embodiment of the present invention, FIG. 2B is a partial longitudinal sectional view of the shape of the deformation absorbing material shown in FIG. 2A, and FIG. Diagram B
FIG. 2D is a vertical cross-sectional view showing the deformed state of the deformation absorbing material shown in FIG. 1... Support cylinder, 2... Lens, 3... Trunked part, 3a
... Corner, 4... Holder ring, 5... Threaded part, 6... Lens.
Fitting part of barreled part, D _K ...Inner diameter of barreled part at room temperature, D′ _K
...Inner diameter of the barrel when expanded, D'' _K ...Inner diameter of the barrel when balanced with lens expansion, D _L ...Outer diameter of the lens at room temperature, D' _L ...Outer diameter of the lens when expanded, D'' _L …
Lens outer diameter when balanced with expansion of barreled part, 11
... Support cylinder, 12 ... Trunked part, 13 ... Lens, 14
... Deformation absorbing material, 15... Presser ring, 16... Threaded portion.

Claims (1)

[Claims] 1. In a holding device for holding a plastic lens, a barreled portion formed on a lens support tube for holding a plastic lens, a pressing member for holding down the lens, and a holding device that engages with the lens surface and outer periphery of the lens, and An elastic member having a substantially L-shaped cross section and formed of a material slightly softer than the hardness of the lens is interposed between the attachment part and the holding member, and the elastic member causes the lens to expand or contract to deform the lens. A holding device for a plastic lens, characterized in that it presses and holds at least the lens surface so as to absorb water.