JPS60217323A - Automatic focus optical device - Google Patents

Abstract

PURPOSE:To simplify the constitution of an automatic focus optical device, and to improve its responsiveness by controlling the shape of an optical surface of an elastic body in accordance with a signal detected by a focusing state detecting means. CONSTITUTION:A transparent elastic body 3 is put into a cylindrical vessel 1 having a circular opening part 2, and the pressure is applied to the elastic body 3 through a movable part 4 consisting of a transparent parallel plate. In accordance with magnitude of the applied pressure, a part of the elastic body 3 is projects in the shape of a convex lens from the opening part 2, or sinks in the shape of a concave lens. A focusing state is detected by a focusing state detecting means, by which the pressure applied to the elastic body 3 is controlled in accordance with a detected signal, and a shape of an optical surface of the elastic body 3 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical device that achieves an autofocus function by deforming an optical surface made of an elastic body.

2. Description of the Related Art Conventionally, devices with an autofocus function have been widely used in cameras, optical disk devices, optical measurement devices, and the like.

In such an optical device, focusing is performed by mechanically moving part or all of the imaging lens along the optical axis direction. In such a mechanical focusing mechanism, the driving mechanism for the lens that is moved for focusing tends to be large in size, and it is difficult to obtain extremely fast response.

Furthermore, conventionally, as a method for changing the focal length of an imaging optical element without moving optical members such as lenses or mirrors, a liquid is placed in an elastic container as shown in Japanese Patent Application Laid-Open No. 55-38857. Some proposals have been made in which the shape of the piezoelectric material is changed by the hydraulic pressure applied to the piezoelectric material, and in which a piezoelectric material is used, as in Japanese Patent Application Laid-open No. 56-110403 and Japanese Patent Application Laid-open No. 58-85415.

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 to provide an optical device having a variable focus mechanism with a simple configuration and good responsiveness.

In the optical device according to the present invention, at least some optical members in the imaging optical system provided in the optical device include:
An elastic optical member consisting of an elastic body and means capable of controlling the shape of the optical surface of the elastic body is disposed, and the focal position of the imaging optical system itself is made variable by changing the surface shape of the optical member. . Furthermore, means for detecting the focal position of the imaging optical system is provided in the optical device, and the surface shape of the optical member is controlled based on information from the means. The elastic optical member deforms the optical surface formed by the elastic body at the opening by causing the volume-shaped elastic body itself to protrude convexly or sink concavely from the opening of the member having the opening, A desired focal length can be obtained. Therefore, simply by 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 focal length can be obtained, making it easy to configure and control the optical member. This is extremely easy, and since the focal length changes based on changes in the shape of the optical surface, the rate of change in the focal length can be set extremely large.

The elastic body of the optical member used in the optical device of the present invention causes deformation when 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. A material having the property of returning to its original shape (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, with a limit strain of 100
It will be close to 0%.

The elastic material has an elastic modulus depending on the characteristics of the optical device to which it is applied, and is generally used to easily obtain large elastic deformation or to make the state after deformation optically more homogeneous. Therefore, a material with a small elastic modulus is preferable.

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

Such rubber elastic bodies include natural rubber generally known as "rubber", such as styrene-butadiene rubber (S
BR), butadiene rubber (BR), imprene rubber (
IR), ethylene propylene rubber (E PM, E P
DM), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NB
R), urethane rubber (U), silicone rubber (St),
Examples include fluororubber (FPM), polysulfide rubber (T), and polyether rubber (FOR, CHR, CHC). 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, a polymeric substance exhibiting a rubbery state at the temperature at which the optical element is used can be widely used as an elastic body applied to the optical device of the present invention. The modulus of elasticity 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 modulus of elasticity.

It is desirable for the elastic body to undergo 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, so it is necessary to use It is necessary to select the elastic body appropriately.

The elastic modulus is also measured by, for example, tensile, bending, compression, etc. methods depending on the type of stress depending on how the optical member is used.

The elastic body has an elastic modulus of 10''-
It is smaller than 10 dyne/cm2, and 1.
08 dyne/am2 or less is suitable, preferably 10
6 dyne/cm2 or less, particularly preferably 5 x 105
dyne/cm2 or less, and the lower limit is preferably smaller as long as the elastic body has a property that it does not spill when the elastic body constitutes an optical member, unlike a normal liquid. Note that although optical devices 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 member.

The hardness and softness of an elastic body depend to some extent 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 its penetration, which can be easily determined.

However, if the modulus of elasticity is as low as 106 dyne/c+n2 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 JIS K2808.

In addition, when the elastic modulus is small, it is difficult to measure it by "tensile and elongation" as a measurement method, so the value can be determined by compression (5% 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.

The elastic modulus of each of these 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 type; KE104G
EL (product name)) and catalyst (product name; Cat alyst
-104, Shin-Etsu Chemical Type), when a diluent (trade name: RTV Thinner, Shin-Etsu Chemical Type) 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 Φ 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 one in which the opening is provided in a flat plate, and when the elastic body is housed in a container and used, at least one part of the container is used. An opening may be provided in one wall. 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 elastic optical member formed by these openings 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 feedback while detecting the effect. things are 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 conventionally known 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 the optical effect. It is preferable to use a method that allows electrical control of an electromagnet, a stepping motor, a piezoelectric element, or the like. Also,
Volume change due to heating can be performed using a heater provided outside or inside the elastic body. It goes without saying that the elastic optical member can have the configuration of an elastic lens or an elastic mirror, but in the following description,
This will be explained using an elastic lens.

Figures 1 to 3 show cross sections of typical basic configurations of elastic lenses used in the optical device according to the present invention.
1 is a cylindrical container having a circular opening 2, 3 is a transparent elastic body, and 4 is a movable part for pressurizing the elastic body, which is 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 3 through the movable part 4, and in this case, a part of the elastic body protrudes from the opening 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 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 by a portion of the elastic body depending on the magnitude of the external force applied to the movable part of the container. Further, it is desirable that the aperture plate 2' having the apertures 2 is optically opaque. 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. 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, a plurality of openings 7 and 9 are provided,
It is also possible to give each curvature by applying pressure.

Further, 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 an optically transparent top lid 11 of the container, and by applying external pressure to the movable part 4, an optical surface made of an elastic body 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. , a method of controlling a movable part using an electromagnet, etc., but the present invention is not limited to these methods. Further, as an example of another elastic lens used in the present invention, as shown in FIG. 7, a cylindrical piezo element 14
It is also possible to use the radial expansion and contraction to cause the elastic body 3 filled inside the piezo element to protrude and sink from the cylindrical opening 15 to form an optical surface.

Note that FIGS. 8 and 9 show specific examples of applying an external force to the elastic body. In FIG. 8, the elastic body 3 is housed in a cylindrical piezoelectric body 21, and the switch By applying a voltage through 23, the optical surface of the opening 18 is deformed by bringing the disk-shaped movable section 20 and the driving section 19 having the opening 18 closer to each other. Further, FIG. 10 shows that the optical surface of 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.

By using the elastic lens described above, an autofocus optical device can be realized without using almost any mechanically movable parts. Hereinafter, the optical device of the present invention will be explained using the drawings.

FIG. 10 is a diagram showing one embodiment of the optical device of the present invention, and this figure is an example in which the present invention is applied to an autofocus optical device for an optical disc. In the figure, 30 is a semiconductor laser that is a light source, 31 is a drive circuit that drives the semiconductor laser,
32 is a collimator lens that collimates the light beam emitted from the semiconductor laser 30, and 33 is a half mirror that guides the collimated light beam onto the optical disk surface, which will be described later.
Reference numeral 134 denotes an elastic lens as explained in FIG. 7, for example, and functions as a condenser lens that condenses the collimated light beam. 35 is an optical disk, and 36 is a motor for rotating the optical disk. The light beam focused on the surface of the optical disk 35 by an elastic lens 34 is reflected by the optical disk, passes through the elastic lens 34 again, and is turned into a half mirror. -33 and is guided to the focus state detection system 37. The focusing state detection system is a known means, for example, as shown in the figure, a light amount sensor 39 is set at defocus positions before and after the convergence position of the light beam via a half mirror 38.
and 39', and a focus state determination circuit 40 that determines the focus state based on the output signal of the light amount sensor (39, 39').
A combination of these can be used. The signal detected by the focus state detection system is guided to the elastic lens drive circuit 41, and the power of the elastic lens is controlled by the drive circuit. The condensing position of the light beam is maintained correctly on the surface of the optical disk 35.

FIG. 11 is a diagram showing another embodiment of the optical device of the present invention, and is a diagram showing the basic principle of an active autofocus optical device used in cameras and the like. In the figure, reference numeral 50 denotes an elastic lens applied to the present invention, and the elastic lens is driven using, for example, a piezo element as explained in FIG. 7. 51 is a drive circuit for driving the elastic lens, 52 is the image plane of the elastic lens, and 53 is for pointing the object to be photographed. 5
Reference numeral 4 denotes an LED, which is installed at a position where it is in a mirroring relationship with the image plane 52 with respect to the mirror 55. 57 is a COD that detects the light emitted from the LED 54 and reflected by the subject 53, and the COD is placed in a mirroring relationship with the image plane 52 with respect to the mirror 56. LED54
The emitted light flux is reflected by the mirror 55, passes through the peripheral part of the elastic lens 50 that is not used for image formation, reaches the subject 53, is reflected by the subject, and passes through the peripheral part of the elastic lens 50 again. An image is formed on the CCD 57 by the mirror 56. The focus state is 5. The focus state detection circuit 58 detects the blur of the imaged spot on the CCD.
It is determined by detecting the A signal is fed back from the focus state detection circuit to the elastic lens drive circuit 51 according to the focus state, and the power of the elastic lens is controlled by the signal. By the method described above, it is possible to realize an autofocus control device used in a camera or the like.

The above example is a so-called active type autofocus device that performs autofocus control using light emitted by an LED, etc., but a passive type auto-off focus device that performs autofocus using the light of the subject itself is also available. Needless to say, it can be easily realized in accordance with the spirit of the invention.

The following method is also effective as a method for driving the elastic lens used in the above-mentioned optical device. That is, a minute high frequency signal is always added to the signal generated by the elastic lens drive circuit, so that the elastic lens always repeats minute deformation at high frequency.

Due to the minute deformation shown in 1, the focal position shifts by a minute amount, but the focus state detection circuit detects this shift in the focal position, and in order to bring it into focus, the elastic lens is moved back and forth between the focal points. It is possible to determine in which direction the vehicle should be driven. With normal focus detection methods, it is possible to distinguish between in-focus and out-of-focus states, but it is difficult to determine in which direction the focus is out of focus, so quick driving is not possible. The method allows for fast response.

Such a driving method is based on the first method of the present invention using an elastic lens.
This is due to two effects, and such high-frequency driving is difficult with normal movement of the entire lens.

Seventh aspect of the optical device according to the present invention is that the optical system used in the optical device can control the focus of the optical system without displacement in the optical axis direction, and has high response characteristics. Control is possible.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9 each show an optical device of the present invention. 10 and 11 are views each showing an embodiment of the optical device of the present invention. 30-m- semiconductor laser, 31-m- drive circuit, 32
-m-collimator lens, 33-m-half mirror,
34.50-m-elastic body lens, 37--focus state detection system, 41.51--elastic body lens drive circuit, 52-
m-image plane, 53--1 object, 54-1-LED, 5
7----CCD, 58-m-Focus state detection circuit.

Claims (1)

[Claims] (1) An elastic optical member comprising an elastic body and a member having an opening capable of protruding or sinking the elastic body to deform the optical surface; and a focusing state detection means for detecting the focusing state of the elastic optical member. An automatic focusing optical device comprising: an automatic focusing optical device, wherein the shape of the optical surface of the optical member is controlled according to a signal detected by the focusing state detecting means.