JPS60114802A - Optical element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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-objective equipment such as optical communications and laser discs, and in particular, relates to an optical element used in optical equipment such as cameras and videos, and electro-objective equipment such as optical communications and laser discs. , relates to a variable focus optical element that changes the focal length.

Conventionally, as a variable focus optical element, Japanese Patent Application Laid-Open No. 55-368
57, in which liquid is filled in an elastic container and its shape is changed by the pressure of the liquid, and JP-A-56-110
405, % Patent Publication 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, provide a variable focus optical element with a large change in focal length, and a simple configuration.

The optical element according to the present invention is characterized in that it comprises a member having an elastic body and an opening capable of protruding or sinking the elastic body to deform the optical reflective surface. That is, the optical element according to the present invention deforms the optical reflection 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,
It is possible to obtain desired optical characteristics, 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 reflective surface can be reversibly changed to obtain the desired optical properties, making it possible 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 has the property that when a force is applied to an object, it causes deformation, the added force is only slightly larger (within the elastic limit), and when the force is removed, the deformation returns to its original state ( elasticity) can be used.

In a normal solid, the maximum strain (critical strain) Fi at its elastic limit date is about 1%. In addition, in the case of elastic rubber with an addition of 1, the extrinsic limit is very large, and the limit strain l'
It will be close to 1lDOD%.

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 obtain a thick elastically deformable complete product, it is In order to make the material more homogeneous than the optical IC, it is preferable that the elastic modulus is small.

The elastic modulus (()) is expressed as G=σ/γ (σ: stress, γ: elastic strain). Further, elasticity that causes large deformation with a 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.

Such rubber elastic bodies include natural rubber and styrene-butadiene rubber (SDR), which is generally known as ``1 rubber''.
, butadiene rubber (BR), isoprene rubber (KR)
, ethylene propylene rubber (EPM, E?DM)
, butyl rubber (AER), chloroprene rubber (CAR)
Acrylonitrile loosetadiene rubber (NI3R), urethane rubber (U), noricone rubber (Si), fluorine rubber (FPM), polyether rubber (FOR, CHR, CHO), etc. Synthetic rubbers can be mentioned. All of these materials 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 exhibiting a rubbery state at the operating temperature can be widely used as the elastic body of the present invention.

The elastic modulus 1-t in the rubber state is determined mainly by the crosslinking state of the polymer chains constituting 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 for large deformations to occur with 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 modulus of the elastic body used in the present invention is smaller than that of a normal solid, which is 1011 to 10" dyne/m2, and is suitably 10' dyne/cm2 or less of a rubber elastic body, preferably 10' dyne/c- IIL2 or less, particularly preferably ff, 5 x 105 dyneAIn2 or less, and the lower limit is preferably smaller as long as the elastic body does not spill, unlike normal liquids, when the elastic body constitutes an optical element. is often used at room temperature, but may also be used particularly at high or low temperatures, so 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
ISK 6501 stipulates a method of applying a small strain to the surface of a sample using a spring and evaluating the hardness of rubber based on the degree of penetration9, which can be easily learned.

However, when the elasticity is as low as 106 dynθ1 cm2 or less, the above-mentioned method cannot be used to determine the elasticity, and in that case, the penetration is evaluated using an inch micrometer according to JISK 2808.

If the modulus of elasticity is small, it is difficult to measure it using the tensile-elongation method, so the value can be determined by compression (5% deformation) and can be correlated with the penetration of the tip.

In addition to conventional vulcanization (crosslinking), rubber elastic materials require vulcanization, such as ethylene-vinyl acetate copolymer and A-B-A type butadiene-styrene groin copolymer. You can also use chain polymers, etc. (w
It can be obtained by gelling to control the molecular chain length between the J 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, depending on the structure of the elastic body itself, in addition to controlling the elastic body, 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; KE104G
jlljL (product name)) and catalyst (product name; Catalyst
lyst-104 Shin-Etsu Chemical #) with diluent (product name i
When RTV thinner (manufactured by Tsukagetsu Chemical Industry Co., Ltd.) is added, as the amount added increases, the hardness and tensile strength decrease, and conversely, the elongation increases.

The method of deforming the optically reflective surface at the aperture of an elastic body is
In addition to external force, it is also possible to utilize volume changes due to thermal expansion/contraction, sol-gel deformation, etc. using the above-mentioned materials. To obtain an optically reflective surface, it is necessary to make the surface of the elastic body a reflective surface.

Methods for making a reflective surface include, for example, depositing a complete set of aluminum or silver on the surface of an elastic body, dispersing metal powder, depositing a layer with a significantly different refractive index, spin coding, or plasma polymerization. methods can be adopted.

The member having an opening for forming the optically reflective 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. An opening may be provided in one wall.

Further, although this aperture varies depending on the required optical effect, it is generally a circular aperture to form a convex or concave optical reflection surface with a variable focal length.

Further, by providing an opening in the shape of a rectangular slit, an optical element having a cylindrical or toric optical reflecting surface can be formed.

The optical element formed by these apertures can change its shape arbitrarily (C) 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 to do so.

Furthermore, it would be possible to provide this opening with a piezoelectric element such as a cylindrical piezo, which would make the element significantly more compact.

All conventionally known methods can be used to apply an external force to the elastic body, but deformation of the elastic body can be
It is desirable to perform this using a feedback mechanism while detecting the optical effect, 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 an 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 cylindrical container with a circular opening 2, and 3 is a reflective surface on the opening side. an elastic body,
Reference numeral 4 denotes a movable part for pressurizing the elastic body, which is composed of an optically transparent parallel flat plate. 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 5 through the movable part 4, and in this case, depending on the magnitude of the applied pressure,
A portion of the elastic body protrudes from the opening in the shape of a convex mirror. Third
The figure shows a state in which negative pressure is applied to the elastic body through the movable part 4.
In this case, the elastic body has a concave mirror shape at the opening.

In this way, a desired optically reflective 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 part of the container. Further, the movable part and the elastic body are bonded together using an adhesive or the like, if necessary. Further, if necessary, the elastic body and the inner wall surface of the container are entirely bonded. In addition, instead of the configuration shown in FIG. 1, as shown in FIG. 4, an elastic body 5 which is placed in a container 5 having a parallel flat plate at the bottom and whose opening side is a reflective surface has a circular opening 7. It is also possible to adopt a configuration in which pressure is applied by the movable part 6. Furthermore, as shown in FIG. 5, it is also possible to provide a plurality of openings 7 and 9 and to apply pressure to the elastic body 6 with the surfaces of both openings serving as reflective surfaces to give each curvature. 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 formed by a cylinder 12 fixed to the optically transparent top lid 11 of the container, and by applying external pressure to the movable part 4, an optically reflective surface made of an elastic body is formed at the opening 1.
Formed in 3.

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 such as a method of controlling a movable part using an electromagnet, but the present invention is not limited to 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.
By expanding and contracting in the radial direction, the elastic body 6 filled inside the piezo element can protrude and sink from the cylindrical opening 15 to form an optical reflective surface. Furthermore, the opening of the optical element according to the present invention is not limited to a circular shape. For example, if a container 16 having a rectangular opening 17 is used as shown in FIG. It is possible to make the body shape cylindrical or toric.

Note that FIGS. 9 and 10 show specific examples of applying an external force to an elastic body. In FIG. By applying a voltage through the disc-shaped movable part 20 and the driving part 19 having the opening part 18, the mouth part 18 is moved closer to each other.
deforms the optically reflective surface of the Further, FIG. 10 shows a device in which the optical reflection surface at the opening 24 of the elastic body 3 can be deformed by moving the movable part 25 made of a ferromagnetic material in the depth direction of the container 27 using an electromagnet 26. be.

Example 1 FIG. 11 is a sectional view of an optical element manufactured in this example. First, silicone rubber (product name: K E104 Gam, manufactured by Shin-Etsu Chemical Co., Ltd.) was charged with a catalyst (product name: : 0a-alyst 10
4 Shin-Etsu Chemical Co., Ltd.) was added in an amount of 12% by weight, and was left to stand for 48 hours at 50 ml to form an elastic body 60. The elastic modulus of this elastic body is 2 x 105 dy≠L2. Next, an aluminum plate 61 having an opening 32 with a diameter of approximately 15 cm is placed on the 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 36 moves the aluminum plate 31 up and down, causing the elastic body to protrude or settle through the opening 32 of the aluminum plate 31. let The shape of the protruding and sinking part at this time is a rotationally symmetrical aspherical surface with a large radius of curvature near the optical axis and a small radius of curvature at the periphery. When the radius of curvature near the optical axis was varied within the range of -2, the radius of curvature near the optical axis could be continuously varied within the range of 00 to 30.

Further, the focal length of the mirror at this time could be varied within the range of one flash to -15πm.

Example 2 In Example 1, the diameter of the opening 432 of the aluminum plate 31 was set to 1
When set to 0, the radius of curvature near the optical axis is oo~25, and the focal length is 1~2 for a pressure of 0 to 200.
I was able to change it within a range of 12.

Example 3 In Example 1, when the amount of catalyst added was set to 10%, the elastic modulus of the obtained elastic body was approximately 1 x 105 dyn, Am
It was 2. Pressure at this time 0-100g/crIL2
On the other hand, the radius of curvature near the optical axis could be varied in the range of 0 to 32 degrees, and the focal length could be varied in the range of -1 to -16 degrees.

Example 4 In Example 1, the surface of the aluminum plate 310 having an opening in contact with the elastic body 30 was pre-treated with a primer (trade name Niprimer A1 manufactured by Shin-Etsu Chemical Co., Ltd.), and the aluminum plate 31 and the elastic body 6ot were bonded. . When the holding ring 33 rotates, the aluminum plate 31 is pulled up and negative pressure is applied to the elastic body 30, so that the elastic body 3o sinks into a concave shape at the opening 32 of the aluminum plate. For the applied negative pressure of 0 to 100 flfi71L2, the radius of curvature near the optical axis is oo to 63 cm, and the focal length is o.
It was possible to change it continuously from o to 3211+I+.

As a result, by pressing the aluminum plate down and pulling it up, it is possible to form a convex-portal mirror continuously (C), and the focal length is oo ~ 32 dragon → - It has been found that it acts as an optical element that varies in the range of SEN to -12 Ryu.

[Brief explanation of the drawing]

Figure i41, Figure 2, and Figure 3 are cross-sectional views of the optical element according to the present invention, and Figure 1 shows the 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 downward. FIGS. 4, 5, and 7 are cross-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. FIGS. 9, 10, and 11 are cross-sectional views in which means for applying an external force to an optical element according to the present invention are arranged. 1.5, 8, 10.16 and 29 ... Containers 3 and 30 ... Elastic bodies 2.7, 9.15, 15.17 and 32 ... Openings 4 and 6 ... Movable part 14 ... Piezo atom 28 ... Glass plate 31 ... Aluminum plate 33 ... Holding ring

Claims (1)

[Claims] (1) An optical element comprising an elastic body and a member having an opening capable of protruding or sinking the elastic body to deform an optical reflection surface.