JPH0327084B2 - - Google Patents

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.
In particular, the present invention relates to a variable focus optical element whose focal length can be changed by changing the shape of the optical surface.

Conventionally, as a variable focus lens, JP-A-55-
36857, in which a liquid is filled in an elastic container and its shape is changed by the pressure of the liquid, and those using piezoelectric materials, as in JP-A No. 56-110403 and JP-A No. 58-85415, have been proposed. has been done.

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 of the present invention has an aperture member made of a material that does not substantially deform, and a light-transmissive elastic body having a surface having a larger area than the aperture, The surface of the elastic body in the aperture is arranged to face the aperture and is used as an optical surface, and the optical surface protrudes or sinks from the aperture by releasing a volume change imparted to the elastic body at the aperture. This optical element is configured to have a variable focus, and is characterized in that all or part of the surface of the elastic body is made harder than the inside.

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 lumpy elastic body itself to protrude convexly or sink concavely from the opening of the member, thereby deforming the optical surface formed by the elastic body at the opening. 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 optical elements. This is extremely easy, and since the optical characteristics change based on the change in the shape of the optical surface, the rate of change in the optical characteristics can be set extremely large.

The elastic body used in the present invention is one that has the property (elasticity) that it deforms when force is applied to the object, and that the deformation returns to its original state when the force is removed, as long as the applied force is not too large (within the elastic limit). 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, and its limit strain is close to 1000%.

In the optical element according to the present invention, an elastic modulus depending on the characteristics of the optical element to be formed is used as appropriate, but in general, in order to easily obtain large elastic deformation, or the state after deformation is more homogeneous than optical. In order to achieve this, it is preferable to use a material with a small elastic modulus.

In addition, the elastic modulus (G) is G=σ/γ (σ=stress,
γ=elastic strain). Further, elasticity that causes large deformation with small stress is called high elasticity or rubber elasticity, and therefore, this type of elastic body can be particularly preferably used in the present invention.

Generally speaking, “rubber” is used as such a rubber elastic body.
Natural rubber known as styrene butadiene rubber (SBR), butadiene rubber (BR), isopre rubber (IR), ethylene propylene rubber (EPM,
EPDM), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), urethane rubber (U), alicorn rubber (Si), fluorine rubber (FPM), polysulfide rubber (T),
Examples include synthetic rubbers such as polyether rubber (POR, CHR, CHC). All of these exhibit a rubbery state at room temperature. However, in general, polymeric substances take either a glass state, a rubber state, or a molten state, depending on the degree of Brownian motion of the molecules.
Therefore, a wide variety of polymeric substances exhibiting a rubbery state at the operating temperature of the optical element can be used as the elastic body of the present invention. 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 a small stress) also leads to a decrease in strength. It is necessary to select the body appropriately. 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 has an elastic modulus smaller than that of a normal solid, 10 ¹¹ to 10 ¹³ dyne/cm ² , and preferably 10 ⁸ dyne/cm ² or less of a rubber elastic body.
10 ⁶ dyne/cm ² or less, particularly preferably 5×
The lower limit is 10 ⁵ dyne/cm ² or less, and the smaller the lower limit is, the better, as long as the elastic body does not spill when the elastic body constitutes an optical element, unlike a normal liquid. Note that although optical elements are often used at room temperature, they may also be used at particularly high or low temperatures, so the above range of elastic modulus is at the operating temperature of the optical element.

The hardness and softness of an elastic body depend to some extent on its elasticity. JIS6301 stipulates a method of applying a small strain to the sample surface using a spring and evaluating the hardness of rubber based on its penetration, which can be easily determined.

However, when the elastic modulus is as low as 10 ⁶ dyne/cm ² or less, it cannot be measured using the above-mentioned method, and in that case, the penetration is evaluated using a 1/4-inch micro-consistency meter according to JISK2808.

In addition, when the elastic modulus is small, it is difficult to measure it by "tensile-elongation" as a measurement method, so compression (5
% deformation), and the correspondence with the previous penetration can be determined.

Rubber elastic bodies are manufactured using the conventional vulcanization (crosslinking) process.
In addition to those that do not require vulcanization, such as ethylene-vinyl acetate copolymers and A-B-A type butadiene-styrene block copolymers, and chain polymers, etc. (by controlling the molecular chain length).

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.

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

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

Further, the elastic body according to the present invention is preferably a highly elastic body so as to obtain large deformation with small stress.
Such elastic bodies are soft and have a problem in self-retention.

In the present invention, this problem is solved by maintaining elasticity in the necessary parts of the elastic body and hardening the unaffected outer part.

As mentioned above, various types of elastic bodies are known, but many exhibit their elasticity through "bridging" through vulcanization, etc. In this case, the elastic behavior is in a "bridging" state. Dependent.

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

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, dithiol, and peroxide are used. Radicals are generated when used in combination with substances that generate radicals through thermal decomposition such as benzoyl and aminoazobenzene, oxidizing substances that have a symbiotic structure such as quinone and polynitrobenzene, and suitable oxidizing agents such as aromatic amines, phenols, and mercaptans. There are compounds, etc.

In addition, vinyl compounds include divinyl or diallyl compounds such as divinylbenzene, ethylene dimethacrylate, methacrylic anhydride, and diaryl phthalate; epoxy resins include mono, di, and polyamines; di and polyisocyanates include alkyd resins, polyamides, and polyurethanes. are excellent crosslinking agents.

In addition, this catalyst absorbs light in the visible or ultraviolet region and easily decomposes into radicals, and the generated radicals promote the crosslinking reaction or activate the monomers by being excited by light and colliding with the monomers. Carbonyl compounds such as diacetyl, benzyl, benzophenone, benzaldehyde, and cyclohexane, azo compounds such as azobisisobutyronitrile and azomethane, tetramethylthiuram disulfide, and benzene A variety of dyes are used, such as thiazolyl disulfide, carbon tetrachloride, organic peroxides, uranyl nitrate and eosin, erythrosin, neutral red.

Furthermore, the crosslinking reaction can be carried out not only by the crosslinking agent but also by irradiation with radiation. Polymers that can be crosslinked by radiation include natural rubber, polybutadiene rubber, silicone rubber, neoprene rubber, as well as polyethylene, polypropylene, polystyrene,
Such as polyvinyl chloride.

Further, any crosslinked state can be obtained as an intermediate state during curing of the thermosetting resin.

The present invention is achieved by controlling the crosslinking state of a part of the elastic body, that is, all or a part of the surface other than the surface forming the optical surface, by the above-mentioned method and crosslinking three-dimensionally to form a network structure. , the periphery of an elastic body is hardened to form a container.

That is, it is made into a container by hardening only the peripheral portion while maintaining elasticity such that the inside of the elastic body protrudes or sinks from the opening and can be deformed to exhibit its optical effect.

This makes it possible to integrate the elastic body and the container, which greatly contributes to making the device more compact.

The member having openings for forming the optical surface of the elastic body may be a flat plate with openings, or the parts other than the openings may be cured by a crosslinking reaction as described above.

Further, as a method for curing only the surface of the elastic body, the above-mentioned crosslinking agent is dispersed, adsorbed, and diffused only on the surface, and reaction is caused only on the surface by heating and light irradiation. Further, the hard film on the surface is not necessarily made of rubber, but may be made of a general hardening type resin. Although the shape of this aperture varies depending on the required optical effect, it is generally a circular aperture to form a convex or concave lens with a variable focal length.

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

The optical element formed by these openings can change its shape arbitrarily by external force applied to the elastic body or by volume change of the elastic body due to thermal expansion/contraction, sol-gel change, etc. It is possible to control the effect by feedback while detecting the effect.

Furthermore, 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 conventional methods can be used to apply an external force to the elastic body, but it is desirable to deform the elastic body using a feedback mechanism while detecting optical effects. 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.

Figures 1 to 3 show cross sections of typical basic configurations of the optical element of the present invention, in which 1 is a hardened surface of a cylindrical elastic body, 3 is a transparent elastic body, and 4 is an opening. The aperture plate also serves as a movable part for pressurizing the elastic body. FIG. 1 shows a state in which no pressure is applied. FIG. 2 shows a state in which pressure is applied to the elastic body 3 through the aperture plate 4, and in this case, a portion of the elastic body protrudes from the aperture in the shape of a convex lens 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 aperture plate 4, in which case the elastic body has a concave lens shape at the aperture.

In this way, a desired optical surface shape can be realized at the opening by a portion of the elastic body depending on the magnitude of the external force applied to the movable portion of the container. Further, it is desirable that the aperture plate 4 having the apertures 2 be optically opaque, but if it is transparent, it can be used as a bifocal optical element. Also, instead of the configuration shown in Fig. 1, the elastic body itself can be hardened to form an aperture plate as shown in Fig. 4.
It is also possible to configure the elastic body 3 to be pressurized by the movable part 6. 5 is a hardened surface. Furthermore, the fifth
As shown in the figure, it is also possible to provide a plurality of openings 7 and 8 and to apply pressure to each of them to provide a curvature. Further, by changing the sizes of the plurality of openings, different curvatures can be given to each of the openings.

Here, any method can be used to apply pressure to the elastic body 3 by driving the opening plate or the movable part, and a simple method is to cut a thread in the container and then screw the movable part into the container. , a method of controlling a movable part using an electromagnet, etc., but the present invention is not limited to these methods. Also,
As an example of another optical element, as shown in FIG. 6, a cylindrical piezo element 9 is used, and by expanding and contracting in the radial direction, an elastic body 3 filled inside the piezo element is inserted into an opening 10 of the cylinder. It is also possible to form an optical surface by protruding and settling from the surface. Further, the opening of the optical element according to the present invention is not limited to a circular shape. For example, when the optical element has a rectangular opening 11 as shown in FIG. It is possible to have a cylindrical or toric shape.

Note that FIGS. 8 and 9 are specific examples of applying an external force to an elastic body, and in FIG. 8, an elastic body 3 whose periphery is hardened is housed in a cylindrical piezoelectric body 12,
By applying a voltage from the power source 13 via the switch 7, the disc-shaped movable part 14 and the driving part 16 having the opening 15 are brought closer together, thereby deforming the optical surface of the opening 15. In addition, FIG. 9 shows a movable part 1 made of ferromagnetic material by an electromagnet 18.
9 in the depth direction, the optical surface at the opening 20 of the elastic body 3 whose periphery is hardened can be deformed.

Example 1 Elastic body (manufactured by Shin-Etsu Chemical Co., Ltd., trade name;
When preparing KE104GEL), first add 14% of a catalyst (trade name: CAT-104, manufactured by Shin-Etsu Chemical Co., Ltd.) to form an outer container. Prepare an elastic body containing an elastic body with 9% catalyst added, which is hard on the outside (penetration is 30 using a 1/4-inch micro-consistency meter according to JISK2808) and soft on the inside (penetration is also 80). did. FIG. 10 shows this state. By combining an elastic body 3 with a hardened periphery, a member 9 made of ferromagnetic material having a circular opening, and an electromagnet 18, a very compact optical element can be made. Ta. FIG. 11 shows a state in which the elastic body is compressed by an electromagnet and the optical surface is made to protrude in a convex shape.

Example 2 An example of the piezo element illustrated in FIG. 6 was manufactured as a prototype.
First, one end of the piezo (10 m/mφ x 15 m/m) was covered with a Teflon plate with a polished surface, and Example 1 was applied from above.
The same KE104EL with 14% catalyst CAT~104 added was poured to a thickness of 3m/m and cured. Next, an elastic body of KE104GEL containing 9% CAT104 was packed on top of this and hardened.

As a result, it was possible to create a convex lens at the other end without blocking one end with a glass plate, etc., and to create a compact element.

[Brief explanation of the drawing]

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. FIGS. 4 and 5 are sectional views of other embodiments of the optical element of the present invention, respectively. FIG. 6 is a sectional view showing an example of an optical element using a cylindrical piezo element. FIG. 7 is a perspective view of yet another optical element according to the present invention. Figure 8, Figure 9, Figure 1
0 and 11 are respectively cross-sectional views of an optical element according to the invention in which means for applying an external force are arranged. 1 and 5... hardened surface, 2, 7, 8, 10,
11, 15 and 20...opening, 3...elastic body, 6, 14 and 19...movable part, 9...piezo element, 12...piezoelectric body, 13...power supply, 16...
...Driver, 17...Switch, 18...Electromagnet.

Claims (1)

[Claims] 1. An opening member having an opening and made of a material that does not substantially deform, and a light-transmitting elastic body having a surface having a larger area than the opening, the surface facing the opening. The surface of the elastic body in the aperture is arranged as an optical surface, and the optical surface is configured to protrude or sink from the aperture by releasing a volume change given to the elastic body in the aperture, so that the focus can be changed. An optical element characterized in that all or part of the surface of the elastic body is made harder than the inside of the elastic body.