JPS63229401A - Variable focus lens - Google Patents

Abstract

PURPOSE:To obtain a variable focus lens which can largely change a focal length at a high speed by providing piezo-electric materials consisting of transparent films which are stretched in parallel with each other in the aperture of a container and have stretchability in the central part to permit transmission of light and liquid which is hermetically filled by the piezo-electric materials in the container and allows the transmission of light. CONSTITUTION:The piezo-electric films 2a, 2b constituted of, for example, a ceramic piezo-electric material, are stretched in parallel in the apertures at both penetrated ends of the toric container 1. Holes which allows transmission of light are opened at the center of these piezo-electric films and the transparent films 4a, 4b are stretched therein. The inside of the container 1 is hermetically closed by these films and the high refractive index liquid 5 is filled therein. The transparent films 4a, 4b are so stretched as to be flattened to a plane in the state of impressing a voltage to the electrodes 3a, 3b of the piezo-electric films 2a, 2b by using a power supply 6. Then, the volume in the container decreases and the films 4a, 4b change to a projecting shape when the electric field is made zero. The liquid 5 in the container acts and the container 1 has the effect of a lens when light is entered through the films 4a, 4b in the container 1. The lens which largely changes the focal length at a high speed is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable focus lens that uses a piezoelectric material to rapidly change its focal length.

[Prior art and its problems]

Variable focus lenses have already been put into practical use as zoom lenses. However, when such a variable focus lens that moves the lens mechanically is used, for example, as an objective lens of an optical disk head, the response speed is too slow. on the other hand,
A method has been proposed in which the focal length is changed by changing the refractive index of the substance inside the lens without changing the position or shape of the lens. For example, research is being conducted on methods of changing the orientation of liquid crystals and methods of changing the voltage applied to ferroelectric crystals such as lithium niobate. However, at present, the value of the refractive index that can be changed by these methods is small, and the amount of change in focal length is also small. There is no lens yet that can change the focal length at such a high speed and at such a large extent.

An object of the present invention is to provide a variable focus lens that uses piezoelectric material and can change its focal length at high speed and greatly.

[Structure of the invention]

The variable focus lens of the first invention is composed of a container having at least one pair of openings in a linear direction, and a stretchable transparent film stretched parallel to each other in the openings so that light can pass through the central part. The piezoelectric material is characterized by comprising a piezoelectric material, a light-transmitting liquid that is hermetically filled in the container by the piezoelectric material, and a voltage applying means for applying a voltage to the piezoelectric material.

The variable focus lens of the second invention includes a container having at least one pair of openings in a linear direction, and a stretchable film stretched parallel to each other in the openings and made of a piezoelectric material with a transparent center. The device is characterized by comprising: a light-transmitting liquid that is hermetically filled in the container by the film; and a voltage applying means that applies a voltage to the piezoelectric material.

[Effect]

Piezoelectric materials generate electric polarization in response to stress caused by external forces, and by utilizing this property in reverse, the material can be deformed by changing the voltage applied to the material. Therefore, piezoelectric materials can be used to change the volume inside a hollow container. The relationship between electric polarization due to piezoelectricity and stress is expressed by the piezoelectric constant dik, where the stress tensor component is Xk (k=1.2. . . . 6), and the electric polarization vector component is Pi (i=1.2. 3), the following relationship holds true.

Pi = d,, When the container 23 is filled, the volume of the container 21 changes due to the change in shape of the transparent membranes 22a and 22b, provided that the liquid and body are sealed. When light 24 is incident on the transparent film, the liquid 23 and the transparent films 22a and 22b act as a lens, and the focal length changes as the transparent film changes. The deformation w (r) of the transparent film at the coordinate r at this time is expressed by the following equation.

Here, P is pressure, and D, Ct, and Ca are expressed by the following formula.

Cz”−□ ・ ・ ・(4)
D Here, E represents the Young's modulus of the transparent film, ν represents the Poisson's ratio of the transparent film, h represents the thickness of the transparent film, and a represents the radius of the transparent film.

When formulas (2) to (5) are rearranged, the following formula is obtained.

...(6) Now, considering only the center part, equation (6) becomes. Also,
The maximum stress at this time is a 2 σ= −P ・ ・
・(8) Represented by h2. A pressure within a range in which the maximum stress σ does not exceed the fatigue limit of the material of the transparent membrane is applied to the transparent membrane, and the amount of deformation of the central portion at that time can be determined from equation (7). The amount of volume change ΔV required at this time is obtained from the following equation.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 is a perspective view showing an embodiment of the first invention.

A piezoelectric film 2a made of, for example, a ceramic piezoelectric material is provided at the openings at both ends of a torus-shaped container l made of, for example, metal.

Stretch 2b parallel to each other. A hole through which light can pass is formed in the center of these piezoelectric films, and transparent films 4a and 4b made of, for example, polyester are placed in the hole.

The inside of the container 1 is sealed with these films, and a high refractive index liquid 5 such as toluene is filled therein.

Piezoelectric film 2a using power source 6.

Transparent film 4a with voltage applied to electrodes 3a, 3b of 2b.

If 4b is stretched so that it becomes flat, when the electric field is reduced to 0,
The volume inside the container decreases, and the transparent films 4a and 4b change into convex shapes. When light passes through the transparent films 4a and 4b and enters the container 1, the liquid 5 inside the container acts, causing the container 1 to function as a lens.

For example, when a voltage of 100 mm is applied to a piezoelectric film with a diameter of 25+ nm, the piezoelectric film changes by 80 μm at the center, and the volume inside the container can change by 11.6 mm.

At this time, toluene with a refractive index of 1.50 was used to
By expanding and contracting the transparent films 4a and 4b of m, it was possible to realize a variable focus lens whose focal length changes continuously from infinity to 3 mm at a response speed of 1/100 seconds or less.

Furthermore, by using a liquid with a high refractive index, it is possible to realize a lens with a short focus at low voltage.

FIG. 2 is a perspective view showing an embodiment of the second invention.

For example, a toroidal container 11 made of metal, etc.
Stretchable membranes 14a and 14b made of polyester or the like are stretched over the openings at both ends of the membrane. A hole is made in the center of these films, and piezoelectric films 12a and 12b made of a transparent piezoelectric material such as PLZT are stretched in parallel to seal the inside. A high refractive index liquid 15 such as toluene is filled therein. When voltage is applied to the electrodes 13a, 13b of the transparent piezoelectric films 12a, 12b using the power source 16, the transparent piezoelectric films change into a convex shape, and the films 14a, 14
b changes into a concave shape. When light passes through the transparent piezoelectric films 12a and 12b and enters the container 11, the liquid 1 inside the container
5 acts, and the container 11 functions as a lens.

For example, when a voltage of 100 μm is applied to a piezoelectric film with a diameter of 25 mm, the piezoelectric film changes by 80 μm at the center, and the volume inside the container can be changed by Il, 61III, and 113. At this time, by using toluene with a refractive index of 1.50, it was possible to realize a variable focus lens whose focal length changes continuously from infinity to 31 at a response speed of 1/100 seconds or less. Furthermore, by using a liquid with a high refractive index, it is possible to realize a lens with a short focus at low voltage.

〔Effect of the invention〕

As described above in detail, according to the variable focus lens of the present invention, it is possible to realize a lens that is fast and has a large amount of change in focal length.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the variable focus lens of the first invention, FIG. 2 is a perspective view showing an embodiment of the variable focus lens of the second invention, and FIG. 3 is a perspective view of the variable focus lens of the second invention. It is a diagram showing the principle. 1, IL 21...Container 2a, 2b...Piezoelectric film 3a, 3b, 13a, 13b...Electrode 4a, 4
b, 22a, 22b...Transparent film 5.15...
. . . High refractive index liquid 6.16 . . . Power supply 12a, 12b . . . Transparent piezoelectric film 14a, 1
4b...Membrane 23...Transparent liquid 24...Light

Claims (2)

[Claims] (1) a container having at least one pair of openings in a linear direction, and a piezoelectric material made of a transparent film stretched parallel to each other across the openings and having a stretchable shape so that light can pass through the central portion; A variable focus lens comprising: a light-transmitting liquid that is hermetically filled in the container by the piezoelectric material; and a voltage application means that applies a voltage to the piezoelectric material. (2) a container having at least one pair of openings in a linear direction; a stretchable film stretched parallel to each other across the openings and made of a piezoelectric material with a transparent center; A variable focus lens comprising: a light-transmitting liquid hermetically filled therein; and voltage application means for applying a voltage to the piezoelectric material.