JPS60208728A - Optical element - Google Patents

Abstract

PURPOSE:To obtain plural focal positions by providing a member in a curved surface shape which has specific refracting power and an elastic body with an optical surface which is displaceable by being projected from or sunk in an opening part provided to part of said member. CONSTITUTION:An optical element 7 uses the surface of the member 2 in the curved-surface shape as the main mirror of a Schmidt optical system and a plane mirror or curved surface mirror 8 as a submirror. Incident luminous flux 9 is therefore reflected by the surface of the spherical surface member 2 firstly, and then reflected again by the submirror 8 to enter the opening part 2' of the member 2. An optical surface is formed of an elastic body at the opening part 2' and the incident luminous flux is refracted by this elastic body member to form an image at a point P. Then, the elastic body 3 is projected from or sunk in the opening part 2' by controlling a movable part 4 to shift the position of the image formation point P, thereby obtaining plural focal positions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical element applicable to various optical devices, particularly an optical element in which one optical element has a plurality of focal positions, and at least one of the focal positions is variable. It is related to.

Conventionally, when manufacturing an optical element having multiple focal positions, it has been difficult to manufacture by forming surfaces with multiple curvatures within one lens or mirror surface, or by combining a mirror and a lens. The difficulty was inescapable. Furthermore, once a lens surface or mirror surface is formed, its focal length cannot be changed.

Furthermore, in order to make the focal length variable not only in such an optical element but also in a general optical element, Japanese Patent Application Laid-Open No. 1983-1991 has been disclosed. As seen in Japanese Patent Laid-Open No. 16857, a means for filling an elastic container with liquid to form a lens element, changing the pressure of the liquid, changing the curvature of the elastic container, and changing its focal length, As seen in Japanese Patent Laid-open No. 56-110405 and Japanese Patent Application Laid-open No. 58-85415, a method using a piezoelectric body 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, and the latter has the disadvantage that its variable f cannot be made very large.

An object of the present invention is to provide an optical element having a plurality of focal positions that is easy to manufacture.

A further object of the invention is to provide the above-mentioned optical element in which at least one focal position can be made variable.

The optical element according to the invention includes a member having a curved surface shape having an opening and an elastic body, and an optical surface is formed by causing the elastic body to protrude or sink from the opening. The above object is achieved by imparting power to each of the curved member and the optical surface of the elastic body. That is, in the optical element, the elastic body is made to protrude convexly or sink concavely in the opening, thereby deforming the surface of the elastic body at the opening to form an optical surface having power. In addition, by forming a curved surface other than the opening of the member having an opening, power can be obtained from the curved surface.

Since the elastic body can change the surface shape at the opening by applying a force to the elastic body, it is possible to easily change the power, that is, the focal length. Further, the member having the curved surface is generally made of a member that does not deform,
Therefore, the power or focal length due to the curved surface is fixed, but by configuring the member with a flexible member,
It is possible to change the power by changing the curved surface of the member.

In the optical element according to the invention, desired optical properties can be achieved by reversibly changing the optical surface simply by applying an external force to the elastic body or by simply changing the volume of the elastic body. Therefore, the configuration and control of the optical element 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.

An elastic body used in non-inventions has the property (elasticity) that when force is applied to an object, it causes deformation, and as long as the applied force is not too large υ (within the elastic limit), the deformation returns to its original state when the force is removed. 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, with a limit strain of 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 used as appropriate, but in general, in order to easily obtain a large elastic change, or the state after deformation is optically good. In order to make the paper homogeneous, it is preferable that the elastic modulus is small.

Note that the elastic modulus (G) is expressed as G=ρ/r (ρ=stress, 12 elastic strain). In addition, elasticity that causes a large deformation of the tube with small stress is called high elasticity or rubber elasticity.
Therefore, this type of elastic body can be particularly preferably used in the invention.

As such rubber elastic bodies, natural rubber generally known as "6 rubber", for example, styrene-butadiene rubber (8
BR), butadiene comb (BR,), inbrene rubber (KR), ethylene propylene rubber (KPM, KPD)
M), butyl rubber (AER), 1 chloroprene rubber (C
R), acryloni) IJ lubutadiene rubber (NB
R), urethane rubber (U), silicone rubber (Sl),
Fluororubber (FPM), polysulfide rubber (T), polyether rubber (FOR, OHR.

010), etc. All of these exhibit a rubbery state at room temperature. However, polymeric substances generally take one of a glass state, a rubber state, or a molten state depending on the degree of Brownian motion of the molecules. Therefore, polymeric substances exhibiting a rubbery state at the temperature at which optical elements are used can be widely used as elastic bodies. The elastic modulus in the rubber state is mainly determined 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 of changing the elastic modulus.

In the 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 mode of stress depending on how the optical element is used.

As for the elastic body used in the present invention, the elastic modulus of a normal solid is smaller than 1011 to 10" dyne/cm2, and the elastic modulus of a rubber elastic body is suitably 108 dyne/cm2 or less, preferably 10' dyne/ctn2 or less, Particularly preferably 5
X 105 dyn 2 or less, and the lower limit is preferably as small as possible if the elastic body has properties that do not spill, unlike ordinary liquids, when the elastic body constitutes an optical element. 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 softening of an elastic body depend on its elasticity. J
SK 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 penetration, which can be easily determined.

However, the elastic modulus is 1o'ayne/cIIL'
If the value is as low as below, it cannot be measured using the above-mentioned method, and in that case, the penetration is evaluated using an inch micro consistency meter according to 2808.

In addition, when the elastic modulus is small, it is difficult to measure it by 1 tension and 1 extension, 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.

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 (Shin-Etsu Chemical #; K1104
GIL (product name)) and catalyst (product name; Catalyst
-104, manufactured by Shin-Etsu Chemical Co., Ltd.) and a diluent (product name: RTV
When thinner (manufactured by Shin-Etsu Chemical Co., Ltd.) is added, as the amount added increases, the hardness and tensile strength decrease, and conversely, the elongation increases.

As a method for deforming the optical surface at the opening of the elastic body, in addition to external force, it is also possible to use the volume change due to thermal expansion/contraction or sol-gel change using the above-mentioned materials.

The member having an opening for forming the optical surface of the elastic body may be a curved plate with an opening provided therein,
Furthermore, when the elastic body is housed in a container and used, an opening may be provided in the wall forming at least one curved surface of the container. Although the 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 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 is controlled by feeding while detecting the effect. things are possible.

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 conventionally known methods can be used to apply an external force to the elastic body, but the deformation of the elastic body can be
It is desirable to use a feedback mechanism while detecting optical effects, and for this purpose, electromagnets, stepping motors,
A method in which the pressure can be electrically controlled using an element or the like is preferable. Further, the volume change due to heating can be performed using a heater provided outside or inside the elastic body. less than,
The uninvented optical element will be explained in detail using the drawings.

FIG. 1, FIG. 2, and FIG. 3 are diagrams showing one embodiment of an optical element according to the invention. In the figure, 1 is a cylindrical container,
2 is a spherical member fixed to a cylindrical container, the surface of which has been optically reflectively treated by vapor deposition of aluminum, etc., and an opening 2' is provided in a part of the member. . 6 is a transparent elastic body, and 4 is a movable part for pressurizing the elastic body 3, which is an optically transparent parallel plate. The movable portion 4 is attached to an elastic body 6.

FIG. 1 is a diagram showing a state in which the movable part 4 is not applying pressure to the elastic body 3, and the surface of the elastic body at the opening 2' is a flat surface. FIG. 2 is a diagram showing a state in which the movable part 4 applies pressure to the elastic body 3. In this case, according to the magnitude of the applied pressure, a part of the elastic body is shaped like a convex lens toward the opening 2'. stand out.

FIG. 3 shows a state in which the movable part 4 applies negative pressure to the elastic body 3, that is, a state in which the elastic body is pulled by the movable part 4. In this case, the elastic body has a concave lens shape at the opening 2'. become. In this way, the shape of the elastic body in the opening 2' can be made into a desired optical surface shape depending on the magnitude of the external force applied to the movable part.

In such an optical element, the light beam incident on the element is imaged at different positions for the light beam incident on the surface of the spherical member 2 and the light beam incident on the elastic member of the opening. Furthermore, the light flux incident on the surface of the spherical member 20 is as shown in FIGS.
In the state shown in the figure, the image is always formed at a fixed position, but the image formation position of the light beam incident on the aperture 2 is determined depending on the shape of the surface of the elastic body. In other words, the imaging position of the light beam incident on the aperture 2 can be freely controlled by the pressure applied to the movable part 4.

Simple methods for driving the movable part 4 include a method of cutting a thread in a container and screwing the movable part into the container, and a method of controlling the movable part 4 using an electromagnet. As another example, the movable part 4 may be fixed to the container 1 and the spherical member 2 may be moved. The same effect can also be obtained by forming the container 1 with a cylindrical piezo element and causing the elastic body filled inside the piezo element to protrude and sink from the opening by expanding and contracting in the radial direction.

Further, contrary to FIGS. 1 to 3, it is also possible to make the surface of the elastic body in the opening 2' a reflective surface and to form the spherical member 2 from a light-transmitting member. (2,3
) can also be light-transmitting or light-reflecting.

FIG. 4 shows an example in which the optical element according to the invention is applied as a variable focus telephoto lens.

In Fig. 4, 7Fi is an optical element according to the invention shown in Figs. 1 to 3, 8 is a plane mirror, and 8 is a curved mirror.
is used as a secondary mirror. Therefore, the incident light beam 9 is first reflected on the surface of the spherical member 20, and then reflected again on the secondary mirror 8 and enters the opening 2' of the member 2. An optical surface made of an elastic member is formed in the opening 2', and the incident light beam is refracted by the elastic member and focused on a point P. By controlling the movable part 4 to protrude or sink the elastic body 3 within the opening 2', it is possible to change the position Mt of the imaging point P. Further, in order to correct aberrations, high performance can be achieved by arranging an aberration correction lens in the optical path or by making the primary mirror 2 or the secondary mirror 8 aspherical.

FIG. 5 is a diagram showing another embodiment of a telephoto lens using the optical element according to the invention. Optical element 10 shown in FIG.
It is a spherical member made of a 11Fi transparent optical member, and an opening 11' is provided in the center thereof. 1
Reference numeral 2 denotes a spherical movable member, and a peripheral portion 12b of the movable member 12 excluding the center portion 12a is subjected to a reflective treatment with a metal film such as aluminum. Therefore, the light beam 9 incident on the optical element 10 passes through the member 11 and the elastic body 3
After passing through the rotating member 120, the light is reflected by the reflecting section 12b, and is emitted from the member 11 to the outside of the optical element via the elastic body 3 again. The light beam emitted from the optical element 10 is reflected by the concave mirror 13 and then reflected again by the optical surface of the elastic body 3 formed in the opening 11' of the member 11 and the transparent part 12a of the movable member 11.
It is imaged at point P via tl-.

The optical element 10 shown in FIG. 5 is used as a so-called in-mirror lens, and by using a part of the movable member 10 as a reflecting surface, the degree of freedom in optical design is increased. .

In the above-mentioned embodiment, a case was described in which only the shape of the optical surface of the elastic body 3 can be changed. It is also possible to configure the elastic body so that its surface deforms as the pressure applied to the elastic body changes.

As described above, in the optical element according to the invention, an element having multiple powers at the same time can be obtained with a single optical element with a simple configuration, and the power can also be easily changed. This makes it possible to provide an optical element that can be widely applied to.

[Brief explanation of drawings]

Figures 1, 2, and 6 are diagrams for explaining an embodiment of the optical element according to the uninvented invention, and Figure 4 and Figure 5 are diagrams each showing an example of the optical element according to the uninvention. FIG. 1 is a diagram showing an example of a telephoto lens. 1... Container 2.11... Spherical shaped member 2', 11'... Opening 6... Elastic body 4.12... Movable member 5.6.9... Luminous flux 7.10 ...Optical element. Applicant Canon Co., Ltd. 1111

Claims (1)

[Claims] (1) It is characterized by comprising a curved member having a predetermined refractive power and an elastic body having an optical surface that can be deformed by protruding or sinking from an opening provided in a part of the member. optical element.