JPS60114804A - Optical element - Google Patents

Abstract

PURPOSE:To obtain a lens widely variable in focal distance with a simple structure by forming on the optical surface of an elastic member another elastic thin layer having elasticity higher than said elastic member. CONSTITUTION:A mixture obtained by adding a catalyst to a silicone rubber is placed in a cylindrical vessel 29 made of brass having a transparent glass plate 28 to form a transparent elastic member 30. An aluminum plate 31 having a circular opening 32 is placed on this member 30, and it can be pressed with a threaded pressing ring 33 engaged with the threaded cylinder surface of the vessel 29. The plate 31 can be moved up and down by rotating the ring 33 to protrude and intrude the transparent elastic member 30 at the opening 32 of the plate 31. Then, a mixture of another silicone rubber contg. a catalyst is dropped on the surface of the hardened elastic member 30 and hardened in a horizontal state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical element used in optical equipment such as cameras and videos, and electro-optical equipment such as optical communications and laser discs. This invention relates to a variable focus optical element that can change the focal length.

Conventionally, as a variable focus lens, Japanese Patent Application Laid-Open No. 55-3685
7, in which a liquid is filled in an elastic container and its shape is changed by the pressure of the liquid, and JP-A-56-1104.
03 and Japanese Patent Application Laid-Open No. 58-85415, a device using a piezoelectric material has been proposed.

However, the former so-called liquid lens requires a liquid reservoir, a pressurizing device, etc., and has a problem in making the element compact, while the latter has the disadvantage that its variable amount cannot be made very large.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and provide a variable focus lens that has a large change in focal length and is simple in construction.

The optical element according to the present invention is characterized by comprising a member having an elastic body and an opening that allows the elastic body to protrude or sink to deform the optical surface. That is, the optical element according to the present invention deforms the optical surface formed by the elastic body at the opening by causing the bulk elastic body itself to protrude convexly or sink concavely from the opening of the member, thereby forming a desired shape. It is possible to obtain optical properties such as focal length.

Therefore, by simply applying an external force to the elastic body or changing the volume of the elastic body, the optical surface can be reversibly changed and the desired optical properties can be obtained, making it easy to configure and control the optical element. This is extremely easy, and the rate of change in the optical properties can be set extremely large because the optical properties change due to changes in the shape of the two optical surfaces.

The elastic body used in the present invention has the property of causing deformation when a force is applied to the object, and as long as the applied force is not too large (within the elastic limit), the deformation returns to its original state when the force is removed (elasticity). ) can be used.

In a normal solid, the maximum strain (critical strain) within its elastic limit is about 1%. In addition, vulcanized elastic rubber has a very large elastic limit (the limit strain is 100
It will be close to 0%.

In the optical element according to the present invention, an elastic modulus depending on the characteristics of the optical element to be formed is appropriately used, but in general, it is necessary to easily obtain large elastic deformation or to ensure that the state after deformation is optically accurate. In order to make it homogeneous, it is preferable to use a material with a small elastic modulus.

Note that the elastic modulus (G) is expressed as G-ρ/r (P-stress, r=elastic strain). Elasticity that causes large deformation with small stress is called high elasticity or rubber elasticity.
Therefore, in the present invention, this type of elastic body can be particularly preferably used.

Such rubber elastic bodies include natural rubber, commonly known as "rubber", and styrene-butadiene rubber (SBR).
, butadiene rubber (BR), impre rubber (IR), ethylene propylene rubber (EPM).

EPDM), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR)
, urethane rubber (U), silicone rubber (Si), fluororubber (FPM), multi-iM rubber (T), polyether rubber (POR, CHR, CHC) and other synthetic rubbers. All of these exhibit a rubbery state at room temperature. However, in general, polymeric substances take either a glassy state, a rubbery state, or a molten state depending on the degree of Brownian motion of the molecules. Therefore, polymeric substances that exhibit a rubbery state at the operating temperature of optical elements are widely used in the elasticity of the present invention. It can be used as a body. The elastic modulus in the rubber state is mainly determined by the crosslinking state of the polymer chains that make up the elastic body, and therefore, for example, vulcanization of natural rubber is nothing but a process that determines the elastic modulus.

In the present invention, it is desirable that the elastic body used be capable of large deformation with small stress, and for this purpose, adjustment of the crosslinking state is important.

However, a decrease in the elastic modulus (a tendency to show large deformation with small stress) also leads to a decrease in strength, so in order to maintain the strength suitable for the purpose of the optical element to be formed, It is necessary to appropriately select the elastic body to be used. The elastic modulus is also measured by, for example, tensile, bending, or compression methods, depending on the type of stress depending on the usage of the optical element.

The elastic body used in the present invention preferably has an elastic modulus of 10" to 1013 dyne/c++I for a normal solid, and 108 dyne/c+d or less for a comb elastic body,
Preferably it is less than IQ6 dyne/crl, particularly preferably less than 5 x 105 dyne/crl, and the lower limit is when the elastic body constitutes an optical element, it is different from a normal liquid and the elastic body has a non-fragile property. The smaller the size, the better. Note that optical elements are often used at room temperature,
In particular, since the optical element may be used at high or low temperatures, the above range of elastic modulus is at the operating temperature of the optical element.

The hardness and softening of an elastic body depend on its elasticity. J
ISK6301 stipulates a method of applying a minute strain to the surface of a sample using a spring and evaluating the hardness of rubber based on the degree of penetration, and can be easily determined.

However, if the elastic modulus is as low as 10' dyn/d or less, measurement cannot be performed using the above method, and in that case, the penetration is evaluated using a 1/4 inch micro-consistency meter according to JIS K2808.

In addition, when the elastic modulus is small, it is difficult to measure it by ``tensile and elongation'', so the value can be determined by compression (5-inch deformation) and the correspondence with the penetration of the tip can be determined.

Rubber elastic materials do not require vulcanization, such as ethylene-vinyl acetate copolymers and A-B-A type butadiene-styrene block copolymers, in addition to the conventional vulcanization (crosslinking) method. It can be obtained by appropriately gelling a substance or a chain polymer by controlling the molecular chain length between the bridge points.

In all of these, the elastic modulus is controlled by adjusting the crosslinking state, the combination of molecules in the block copolymer, the gel state, etc.

Furthermore, in addition to controlling the structure of the elastic body itself, it is also possible to change and adjust its properties by adding a diluent or filler.

For example, silicone rubber (manufactured by Shin-Etsu Chemical; KE104 (
When a diluent (trade name: RTV Thinner, manufactured by Shin-Etsu Chemical Co., Ltd.) is added to a catalyst (trade name: AT-104? manufactured by Shin-Etsu Chemical Co., Ltd.), the hardness and tensile strength increase as the amount added increases. The steel strength decreases and, conversely, the elongation increases.

As the elastic modulus of the elastic body decreases, the tackiness increases. That is, this is because as the elastic modulus decreases, the proportion occupied by viscoelasticity increases.

This adhesion is not desirable for optical elements; for example, if dust in the air adheres to the surface of an optical element, it is difficult to remove.
This causes "blur" and other problems, which lowers its reputation as an optical element.

The present invention aims to improve this problem by making the surface of the elastic body forming the optical surface have a higher elastic modulus than that of the elastic body itself.

That is, in the present invention, the main body of the elastic body maintains a small elastic modulus so as to obtain large deformation with a small force, while only the surface forming the optical surface has a large elastic modulus, thereby solving two contradictory points. The elastic modulus of an elastic body can be controlled by its crosslinking state.

That is, when the crosslinking is 0%, it is a solution or a viscous liquid, and when it is 100% three-dimensionally crosslinked, it becomes a rigid body as seen in thermosetting resins.

Further, a method for curing only the surface of the elastic body is achieved by dispersing, adsorbing, and diffusing a crosslinking agent only on the surface, and causing a reaction only on the surface by heating and irradiation with light.

Various crosslinking agents are used depending on the structure of the target polymer; for unsaturated polymers (natural rubber, butadiene rubber, etc.), sulfur, sulfur compounds such as sulfur chloride and dithiol, benzoyl peroxide, and aminoazobenzene are used as crosslinking agents. There are substances that generate radicals through thermal decomposition, such as quinones, oxidizing substances with resonance structures such as polynitrobenzene, and compounds that generate radicals when used in combination with appropriate oxidizing agents, such as aromatic amines, phenols, and mercaptans.

Also, +4 divinylbenzene, ethylene dimethacrylate, and anhydrous methacrylate in the hinyl compound! Excellent crosslinking agents include divinyl or diallyl compounds such as diaryl phthalate, divinyl, di, and polyamines for evo-chishi resin, and alkyd resins, polyamide polyurethanes, and the like for di- and polyisocyanates.

In addition, this catalyst absorbs light in the visible or ultraviolet region and easily decomposes into radicals, and the generated radicals promote cross-linking reactions or are excited by light and collide with monomers. , it is also possible to use a substance that activates the heptamer and performs a crosslinking reaction, such as diacetyl,
Carbonyl compounds such as benzyl, benzphenone, benzaldehyde, and cyclohexane, azo compounds such as azobisisobutyronitrile and azomethane, tetramethylthiuram disulfide, benzothiazolyl disulfide, carbon tetrachloride, organic peroxides, uranyl nitrate, and eosin. A variety of dyes are used, such as , erythrosine, and neutral red.

Furthermore, the crosslinking reaction can be carried out by irradiation with radiation without using a crosslinking agent. Polymers that can be crosslinked by radiation include natural rubber, polybutadiene rubber, silicone rubber,
In addition to neoprene rubber, polyethylene, polypropylene, and polystyrene.

Such as polyvinyl chloride.

Further, any crosslinked state can also be obtained as an intermediate state during curing of the thermosetting resin. As a method for deforming the optical surface at the opening of the elastic member, in addition to external force, it is also possible to use the volume change due to thermal expansion/contraction, sol-gel change, etc. using the above-mentioned materials.

The member having an opening for forming the optical surface of the elastic body may be a flat plate with an opening, and when the elastic body is used by being housed in a container, at least one part of the container is used. Both may be provided with an opening in one wall. Although this aperture varies depending on the optical effect required, it is generally a convex aperture with a circular aperture and a variable focal length.
It is common to form a concave lens.

Further, by providing an opening in the shape of a rectangular slit, a cylindrical lens and a toric lens can also be formed.

The optical element formed by these apertures can change its shape arbitrarily by applying an external force to the elastic body or by changing the volume of the elastic body, and the degree of change can be controlled by feedback while detecting the effect. It is possible.

Further, it is also possible to provide this opening with a piezoelectric element such as a cylindrical piezo, which allows the element to be made significantly more compact.

All of the conventionally known methods can be used to apply an external force to the elastic body, but the deformation of the elastic body is
It is desirable to use a feedback structure while detecting optical effects, and for this purpose, a method that allows electrical control of electromagnets, stepping motors, piezoelectric elements, etc. is preferable. Further, the volume change due to heating can be performed using a heater provided outside or inside the elastic body. Next, a typical configuration of the optical element according to the present invention will be explained with reference to the drawings.

1 to 3 show cross sections of typical basic configurations of the optical element of the present invention, in which 1 is a cylindrical container having a circular opening 2, 3 is a transparent elastic body, and 4 is an elastic body. A movable part for pressurizing the body, consisting of optically transparent parallel flat plates. FIG. 1 shows a state in which no pressure is applied. Figure 2 shows the movable part 4
In this state, pressure is applied to the elastic body 3 through the opening, and in this case, a part of the elastic body protrudes from the opening in a convex lens shape according to the magnitude of the applied pressure. FIG. 3 shows a state in which negative pressure is applied to the elastic body through the movable part 4, and in this case, the elastic body has a concave lens shape at the opening.

In this way, a desired optical surface shape can be realized at the opening portion of a portion of the elastic body depending on the magnitude of the external force applied to the movable portion of the container. In addition, opening 2
It is desirable that the aperture plate 2 is optically opaque, but if it is transparent, it can be used as a bifocal optical element. Further, the movable part and the elastic body are bonded together with an adhesive or the like, if necessary. Further, if necessary, the elastic body and the inner wall surface of the container are entirely bonded. Moreover, instead of the configuration shown in FIG. 1, as shown in FIG. 4, an elastic body 3 placed in a container 5 having an optically transparent parallel flat plate at the bottom is pressurized by a movable part 6 having a circular opening 7. It is also possible to have a configuration like this. Furthermore, as shown in FIG. 5, it is also possible to provide a plurality of openings 7 and 9 and to apply a curvature to each opening by applying pressure. Furthermore, by changing the sizes of the plurality of openings, different curvatures can be given to each of the openings.

Further, as shown in FIG. 6, the elastic body 3 may be housed in a container 10 having an opening 13 formed inside the container. This opening 13 is an optically i
By applying external pressure to the movable part 4, an optical surface made of an elastic material is formed in the opening 13.

Here, any method can be used to apply pressure to the elastic body 3 by driving the movable part 4 or 6, and a simple method is to cut a thread in the container and then screw the movable part into the container. There are methods of controlling the movable part using electromagnets, but the present invention is not driven by these methods. Further, as an example of another optical element according to the present invention, as shown in FIG. 7, a cylindrical piezo element 14 is used.
Due to its radial expansion and contraction, the elastic body 3 filled inside the piezo element can be made to protrude and sink from the cylindrical opening 15 to form an optical surface. Furthermore, the aperture of the optical element according to the present invention is not limited to a circular shape;
As shown in Figure 5, if a container 16 having a rectangular opening 17 is used, the shape of the elastic body that protrudes and settles under pressure can be made into a cylindrical or toric shape.

Note that FIGS. 9 and 10 are specific examples of applying an external force to an elastic body, and in FIG. By applying a voltage across the diameter, the disc-shaped movable part 20 and the driving part 19 having the opening 18 are brought closer together, and the opening 18 is moved closer to each other.
It deforms the optical surface of the Also, Figure 10 shows
The electromagnet 26 moves the movable part 25 made of ferromagnetic material to the container 2.
7 in the depth direction, the optical surface of the opening 24 of the elastic body 3 can be deformed.

Example 1 FIG. 11 is a sectional view of an optical element manufactured in this example. First, a brass cylindrical container 29 (inner diameter 50 all! and depth 20 vryn) with a transparent glass plate 28 at the bottom is made.
) with silicone rubber (product name: KE104Gel).

Catalyst (product name: Ca-ta)
lyst 104 *manufactured by Shin-Etsu Chemical Co., Ltd.) in an amount of 12% by weight was placed therein and left at 50° C. for 48 hours to form a transparent elastic body 30. The elastic modulus of this transparent elastic body is approximately 2
X 105dyn/crl. Next, an aluminum plate 31 having an opening 32 at a corner with a diameter of approximately 15 degrees is placed on the transparent elastic body 30, and is held in place by a holding ring 33. Here, the presser ring 33 is adapted to be screwed into the cylindrical container 29, and the rotation of the presser ring 33 moves the aluminum plate 31 up and down, causing the transparent elastic body to protrude or sink through the opening 31 of the aluminum plate 31.

Next, silicone rubber (
KE104Gel) and catalyst (CBtalyst104
) was added in an amount of 14% by weight, and about 1 cc of the liquid mixture was dropped onto the surface of the already cured elastic body, and the mixture was cured in a horizontal position (50° C. for 4 hours).

The optical element obtained in this way has improved surface adhesion, and dust and dirt adhering to the surface can be completely removed by blowing it with a blower. There is almost no difference in the shape of the protruding and submerged part from the case without hardening treatment on the surface.When the pressure applied to the rotation of the presser ring is varied in the range of 0 to 200 El/cd, the radius of curvature near the optical axis changes. It was possible to change it continuously in the range of 0 to 30111 m.

Further, the focal length of the lens at this time could be varied within the range of ω to 74 am.

Example 2 An elastic body was prepared in the same manner as in Example 1, and the surface of the elastic body at the opening 32 was coated with ultraviolet curable silicone rubber (product name: TU).
V6050. (manufactured by Toshiba Silicone) and cure it by irradiating it with ultraviolet light.

In the thus obtained optical element, the adhesiveness of the surface of the opening 32 could be greatly improved without affecting other properties.

[Brief explanation of drawings]

1, 2, and 3 are cross-sectional views of the optical element according to the present invention, in which FIG. 1 shows a state in which no external force is applied, FIG. 2 shows a state in which an external force is applied upward, and FIG. 3 shows a state in which an external force is applied upward. indicates a state in which an external force is applied downward. FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are sectional views of other embodiments of the optical element of the present invention, respectively. FIG. 8 is a perspective view of yet another optical element according to the present invention. 9M10 and 11 are cross-sectional views showing means for applying an external force to the optical element according to the present invention. 1.5, 8, 10.16 and 29...Containers 3 and 30......Elastic bodies 2.7, 9
, 13, 15, 17 and 32......Openings 4 and 6...Movable part 14...Piezo element 28...・・・・Glass plate 31・・・・・・・・・Aluminum plate 33・・・・・・・Applicant: Canon Co., Ltd.

Claims (1)

[Claims] (1) In an optical element characterized by comprising an elastic body and a member having an opening capable of protruding or sinking the elastic body to deform the optical surface, the elastic body is attached to the surface of the elastic body forming the optical surface. An optical element characterized by having a thin layer having a large elastic modulus.