JPH04149521A - Lens made of material with electrooptic effect - Google Patents

Abstract

PURPOSE:To eliminate energy dispersion due to diffracted light of high order by composing the lens of a lens main body which has at least one curved surface and a transparent electrode for applying a voltage to the main body. CONSTITUTION:The electrooptic E-O zoom lens 1 consists of the E-O substrate 2 and the ITO transparent electrode 3 which is vapor-deposited uniformly on this substrate 2. The material with electrooptic effect, e.g. ceramic is used for the substrate 2. The substrate 2 is formed in an optically polished plano-convex lens shaped with focal length (f), namely, formed having one surface curved into a parabolic surface. The ITO transparent electrode 3 is vapor-deposited uniformly on the surface of the substrate 2; and a flat plate type ITO transparent electrode part 3b is grounded and a concave ITO transparent electrode part 3a is applied with the voltage. The focal length can be varied electrically only by varying the applied voltage, a polarizing plate is not required specially, and no diffracting phenomenon is caused. Further, the energy dispersion due to diffracted light of high order is eliminated.

Description

Detailed Description of the Invention "Industrial Field of Application J The present invention relates to a variable focus lens using an E-〇 element having an electro-optical effect, and in particular to a variable focus lens that uses PLZT ceramic to generate energy from higher-order diffracted light. The present invention relates to a lens made of a material having an electro-optic effect without dispersion.

"Prior Art" There have been attempts to realize zoom lenses using E-0 elements. For example, a blind transparent electrode was formed on a PLZT ceramic plate, and a voltage applied to the transparent electrode There were lenses that created a lens effect by setting each to a specific value, or even turned it into a zoom lens.

"Problem to be solved by the invention" However, using the above conventional PLZT ceramic,
The E-0 zoom lens, in which the focal length can be electrically varied, has a serious drawback in that it cannot avoid energy dispersion due to higher-order diffracted light caused by a blind transparent electrode.

"Means for Solving the Problems" The present invention was devised in view of the above problems, and includes a lens body made of a material having an electro-optic effect and having a curvature formed on at least one surface, and a lens body that is made of a material having an electro-optic effect. The lens body is formed with a transparent electrode for applying voltage to the lens body.

Furthermore, the present invention provides an applied 1M voltage W for applying a voltage to the transparent electrode to change the focal length of the lens body.
Im means may also be provided.

Furthermore, it is also possible to provide a transparent reinforcing member configured to face the lens body with the transparent electrode in between.

The present invention is made of a material that has an electro-optic effect and has a curvature formed on one surface, and a first lens part that is made of a material that has an electro-optic effect and has a curvature formed on one surface. and a transparent electrode for applying a voltage to the first and second lens parts, respectively, and the first lens part and the second lens part The transparent electrode is sandwiched between the surfaces having no curvature and joined together.

Further, the present invention provides a plurality of connected lens parts each including a lens body having a curvature formed on at least one surface, and a transparent electrode formed on the lens body for applying a voltage to the lens body. It can also be configured as

Furthermore, the present invention uses a material having an electro-optic effect as PLZT.
It can also be made of ceramics.

"Operation" According to the present invention configured as described above, a curvature is formed on at least one surface of the lens body, and a transparent electrode is formed on this lens body. By changing the voltage applied to the transparent electrode by the voltage regulator, the focal length of the lens can be varied.

Further, in the present invention, a transparent M decorative member is provided to face the lens body with the transparent electrode in between, so that the lens body can be reinforced.

In the present invention, a curvature is formed on one surface of the first lens portion, a curvature is formed on one surface of the second lens portion, and a voltage is applied to each of the first lens portion and the second lens portion. A transparent electrode is provided for this purpose, and the non-curvature surfaces of the first lens part and the second lens part are joined with the transparent electrode in between.

Moreover, the present invention forms a curvature on at least one surface of the lens body, and makes the lens body transparent! The lens part with poles is
Multiple connections can also be made.

In addition, the present invention uses PLZ as a material having an electro-optical effect.
It is also possible to use T ceramics.

"Example" An example of the present invention will be described based on the drawings. FIG. 1 shows the configuration of the E-○ (electro-optical) zoom lens 1 of this embodiment.
and an ITO transparent electrode [i3] uniformly deposited on this E-〇 substrate 2. The E-0 substrate 2 is made of a material that has an electro-optic effect, and in this embodiment, the PL
ZT (Lanthanum-mod i f 1ed
LeadZironate T electrode anate) Ceramics are used. In particular, La, Zr, and T
Ceramics with a composition ratio of i of 9/65/35 have a large number of E-〇 bodies, excellent transmittance over a wide wavelength range, are optically isotropic, and are resistant to externally applied voltages. It has characteristics such as the direction of the electric field coincides with the principal axis of the refractive index ellipsoid.
Ideal for lens operation.

The E-0 substrate 2 is in the shape of an optically polished plano-convex lens having a focal length [f]. That is, one surface of the E-0 substrate 2 is a curved surface having curvature.

Although this curvature surface is formed into a parabolic surface, it may also be formed into a spherical surface.

On the surface of the E-〇 substrate 2, an ITO transparent electrode 3 is deposited as shown in -. The flat IT○ transparent electrode section 3b is used as a ground, and a voltage is applied to the convex ITO transparent electrode section 3a.

Although the E-0 substrate 2 of this embodiment has a curved surface with one side having a curvature, it can also be formed with a curved surface having a curvature on both sides. That is, for example, it can be configured to have a biconvex lens shape.

The applied voltage control means 4 shown in FIG. 2 is a means for applying a voltage to the E-0 zoom lens 1, and can adjust the voltage applied to the ITO transparent electrode 3 as appropriate. The applied voltage control means 4 of this embodiment can vary from 6000 volts to 0 volts. Therefore, when the applied voltage control means 4 applies an electric field to the E-0 zoom lens 1 via the transparent conductor w13, it becomes possible to provide a spatial distribution of refractive index that cancels out the lens effect of the E-0 substrate 2. As a result, a zoom lens whose focal length changes continuously from focal length f to infinity can be constructed.

Next, the principle of this embodiment will be explained.

Here, the horizontal axis of the surface of the E-0 substrate 2 is the Xo axis, the vertical axis is the Xo axis, and the optical axis? Let it be the z-axis. Furthermore, E-〇 board 2
Let the center of the plane be the coordinate origin. Then, the total width of the lens is calculated and the maximum thickness is defined as QO.

[Analysis using thin lens approximation] A thin E-0 lens as shown in FIG. 3 will be analyzed. Here, the refractive index of the E-0 substrate 2 is assumed to be no, and the radius of curvature is assumed to be R. It is assumed that the maximum thickness Qo of the lens is sufficiently smaller than the radius of curvature R.

First, the lens effect of the E-0 substrate 2 will be analyzed.

The equation of the circle representing the curved shape of this E-0 substrate 2 is xo
2+ (z-(do-R)) 2=R2...
(1) From the first equation, the lens thickness Q (Xo) is calculated as follows:
(2) becomes. Here, the possible range of xo is -h/2≦
x0≦h/2 (3). From the Pythagorean theorem, the total width of the lens is (h/2) + (r-ζ).

=R2 Then, The total width of the lens is becomes.

In other words, the total width of the lens is Thickness Q and curvature half It is determined from the diameter R.

Than this, the law of nature. optical distance at Q op ( )teeth, becomes.

Furthermore, from R) σ0 and the fifth equation, using a binomial approximation from R), di. p(Xo> =n, σ0 (no 1) / 2 R) ・ ・ ・ ・ ・ (7) And the phase φ(X) of a normal optical lens is φ(X)=
-k(n& -(x2/2f))... (8) Therefore, by comparing the seventh and eighth equations, E
The focal length Nfo of the -0 substrate 2 is: (9) Note that when no voltage is applied to the E-0 zoom lens l, it functions as an fo lens.

Next, the focal length of the E-○ lens with an external voltage applied will be analyzed.

Here, the E-0 lens is made of a secondary E-0 material, and its surface is covered with a transparent electrode so that the applied electric field changes only in the X direction.
Assume that i3 is deposited. The change in the refractive index tensor of a second order E-0 material caused by an applied electric field is given by: Here, nrrk+ is a 6×6 matrix element in the refractive index tensor, and R, lkl are quadratic E-
The coefficient is 0, and Ek and E are electric field components.

If the electric field has only two components, the changes in each number of index ellipsoids due to the applied electric field are respectively...
・(]O) becomes. Furthermore, assuming that the crystal structure of the secondary E-0 material belongs to the cubic system (dotted: m3m), the 10th
The second-order E-0 matrix number of Eq.

from now, External electric field E7 caused by The index ellipsoid is becomes.

Note that the refractive index nX in the X direction is η× 77 o (1+ 7702R12E x2) −
3 given by 0 Furthermore, ①) Since n02 I2 Z2, using binomial approximation, it becomes x (no- (no3/2)).

Similarly, y (no- (no3/2) E, 2 Z (no- (no3/2) E, 2 becomes.

and, When voltage V is applied to E-0 substrate 2, The two components E2 of the electric field are ■ It can be approximated as

Assuming that the light incident on the E-0 substrate 2 is a horizontal beam, the refractive index change Jn, (xo) is n8, so An (Xo) - (no3/2) l R12x
(v/Q (Xo)) 2... (18) Furthermore, 1. / Q By applying a binomial approximation to 2(Xo), and further substituting Equation 19 into Equation 18, Δn
(Xo) = (no3/ 2) l R12XV2(
1102+x02/Q3R) (20)

Then, the optical distance dop (Xo) when voltage is applied is calculated by subtracting nQ from the seventh equation from n0+Δn(X
o). Here, since R>XO', ignoring the term x 04, Qop (x)=
[no+ (no3/2)I R12×(■/Q)2
Q co[(no 1) (no'/2) x I
R121 (v/c) 2 x (x2/2R) ・ ・ ・ ・ ・ (21) Also, the condition for the focal length to be infinite is ζ0ρ
Since (X) is a constant, (no 1)
(no3/2)lR121(V/d)"=0 ・ ・ ・ ・ ・ (22) From the 22nd formula, the applied voltage that makes the focal length infinite is the radius of curvature in the range R> Xo becomes irrelevant.

Therefore, the focal length f of the E-0 zoom lens 1 with voltage applied is f=R[(no 1) (no3/2)IR12
1X(V/R) 2 ] −1 .

[Analysis using thick lens approximation Next, analyze the thick inner lens. For thick lenses, the exact approximation of thin lenses does not hold, so analytical derivation is difficult. Therefore, first, we will derive a refractive index distribution that cancels out the lens effect of the E-0 substrate 2.

Regarding the thick inner lens shown in Fig. 4, the lens thickness is Q,
Define the total width as h.

This lens shape L(Xo) is L (xo) =0 (1(2xo /2)2)...
・(24) Optical pressure fulliLop at distance NQ (
Lop(Xo)
-noR(4Q/h2)X(no-1) -no+Jn (XO), then z=
The phase distribution θ(xo) at Q is θ(xo) = [no +An(xo)
k Qx [1-(2xo/k) 2 ] σ (2xo/h)2 ・(27)

The first term in Equation 27 represents the phase due to passing through the lens, and the second term represents the phase due to passing through the air.

In order to cancel the lens effect, Equation 27 is AklA:
Since its value is the refractive index at X0=0, θ (xo)=Aka= [no+IΔn (Xo) I xo=o]k 0・
・ ・ ・ ・ (28) And from the 27th and 28th equations, Jn (xo
) is Jn (Xo) Jn, g) ten (no 1) (2xo/k)”1
(2xo/h)2 ・ ・ ・ ・ ・ (29) Furthermore, since Jn(xo) is a value that changes depending on the applied voltage ■, rewriting Equation 29, Jn (x,)− V) Δn+(,,,+(no 1)(2x,)/k)21
(2xo/h)z ・ ・ ・ ・ ・ (30) Therefore, the refractive index distribution that satisfies Equation 30 is E-0
This cancels out the lens effect of the substrate 2 and makes the focal length of the E-0 zoom lens 1 infinite.

Note that An (0, ■) can be calculated by the finite element method or the like.

[Diffracted light distribution regarding thin lens] Spot size W. A horizontally polarized Gaussian beam of propagates along two axes (ray axes), with 2=0 and X. Assuming vertical incidence to the E-0 zoom lens 1 in the axial (horizontal) direction,
Using Fresnel diffraction approximation, the spot sizes in the X direction and the X direction at the distance wlz from the E-0 zoom lens 1 are as follows.

[Numerical calculation] The dependence of the focal length of the thin lens on the applied voltage is as shown in FIG. However, no=2.5, R1□ is a second-order electro-optic coefficient, and IRI□ +=2.42×10-'<
mm2/kv2), and the lens thickness ζ-200μm
It is. The larger the focal length f0 when the applied voltage is O■,
The amount of change in the focal length due to the applied voltage increases.9 Furthermore, when the radius of curvature R = 15 m (fo = 10 m>), the distance dependence of the spot size is as shown in Figure 6. However, the incident Gaussian beam wavelength λ -o, 633 μm, spot size W. = 2.0 mm, total lens 1ih = 15.5
This is the case of cm. The applied voltage that makes the focal length infinite is 5.63 kV. The focal length and focal plane spot size for various applied voltages are shown in Table 1.
It will look like this. The results show that as the applied voltage increases, the focal length becomes longer and the spot size becomes larger.

[Modification] As described above, in this embodiment, the IT formed on the E-0 substrate 2
The O transparent electrode portions 3a and 3b are configured to be connected to applied voltage control means 4, and this applied voltage control means 4
By changing the voltage applied to the E-0 plate 2 via the ITO transparent electrodes 3a and 3b, the E-0 zoom lens l
The focal length of the lens is variable.

Furthermore, as shown in FIG. 7, a transparent reinforcing member 2 is attached to the E-0 substrate 2.
1 can also be joined. The structure can be such that an ITO transparent electrode 3 is inserted between the transparent reinforcing member 21 and the E-〇 substrate 2. Note that the transparent reinforcing member 21 may be made of glass, sapphire, or the like.

Furthermore, as shown in FIG. 8, two E-〇 substrates 2, a first plano-convex lens 200 and a second plano-convex lens 210, are prepared,
The plane portions of the first plano-convex lens 200 and the second plano-convex lens 210 can also be joined with the transparent electrode [1r3b in between. Using this transparent electrode 3a as a common ground, voltage from the applied voltage control means 4 can be applied to the transparent electrodes [r3a, 3a formed on the first and second plano-convex lenses 200 and 210]. In this case, the applied voltage can be halved and the load on the applied voltage thinning means 4 can be reduced.

Further, as shown in FIG. 9, a plurality of E-0 zoom lenses 1.1 of this embodiment can be connected in series. Note that transparent reinforcing members 2L 21... can also be attached. And these E-0 zoom lenses 1.1...
By operating , Fourier transform can be performed. Then, by Fourier transforming the input and output signals, a spectrum can be obtained, and by determining the Fourier transform ratio of the object and image, the spatial frequency characteristics can be determined.

This embodiment configured as described above can be applied to a large-scale laser radar collimator, an optical switch, etc.

"Effects" The present invention configured as below-L includes a lens body made of a material having an electro-optic effect and having a curvature formed on at least one surface, and a lens body formed on the lens body,
Since it is composed of a transparent electrode for applying a voltage to the lens body, there is an effect that the focal length can be changed electrically by simply changing the applied voltage.

In particular, it has the outstanding effect of not requiring a polarizing plate and causing no diffraction phenomenon. Furthermore, there is an effect that energy dispersion due to higher-order diffracted light does not occur.

Further, by providing a transparent reinforcing member configured to face the lens body with the transparent electrode in between, the entire lens can be reinforced.

The present invention is made of a material that has an electro-optic effect and has a curvature formed on one surface, and a first lens part that is made of a material that has an electro-optic effect and has a curvature formed on one surface. and a transparent electrode for applying a voltage to the first and second lens parts, respectively, and the first lens part and the second lens part Since the structure is such that surfaces having no curvature are joined with the transparent electrode sandwiched therebetween, the applied voltage can be halved, and the burden on the applied voltage control means can be reduced.

According to the present invention, a plurality of lens parts each including a lens body having a curvature formed on at least one surface and a transparent electrode formed on the lens body for applying a voltage to the lens body are provided. They can also be configured in a connected manner, and have the effect of being able to perform Fourier transformation.

Furthermore, the present invention uses a material having an electro-optic effect as PLZT.
It can also be made of ceramics, and because it is polycrystalline, it has the outstanding effect of not causing birefringence.

[Brief explanation of drawings]

The figure shows an embodiment of the invention, and Fig. 1 shows E of this embodiment.
2 is a diagram showing the configuration of the -0 board, and FIG.
A diagram explaining the configuration of the -0 zoom lens, FIG. 3 is a diagram explaining a thin lens, and FIG. 4 is a diagram explaining a thick inner lens.
FIG. 5 is a diagram for explaining the applied voltage dependence of the focal length of the E-0 zoom lens, FIG. 6 is a diagram for explaining the distance dependence of the spot size, and FIGS. 7 to 9 are diagrams for explaining this example. 9 is a diagram illustrating a modification example of 9 ■ ・ ・ 2 ・ ・ 21 ・ 2] 0 3a ・ 3b ・ 4 ・ ・ ・E-〇zoom lens・E-0 substrate・Transparent reinforcing member・first plano-convex lens・First plano-convex lens, transparent electrode, transparent electrode, applied voltage control means

Claims (1)

[Claims] (1) A lens body made of a material having an electro-optic effect and having a curvature formed on at least one surface, and a voltage formed on the lens body to which a voltage is applied. 1. A lens made of a material having an electro-optic effect, characterized in that it is made of a transparent electrode for (2) A lens body made of a material having an electro-optic effect and having a curvature formed on at least one surface, and a transparent electrode formed on the lens body for applying a voltage to the lens body. 1. A lens made of a material having an electro-optic effect, characterized in that it is comprised of applied voltage control means for applying a voltage to the transparent electrode to change the focal length of the lens body. (3) A lens body made of a material having an electro-optic effect and having a curvature formed on at least one surface, and a transparent electrode formed on the lens body for applying a voltage to the lens body. A lens made of a material having an electro-optic effect, characterized in that it is comprised of a transparent reinforcing member configured to face the lens body with the transparent electrode in between. (4) The first lens part is made of a material that has an electro-optic effect and has a curvature formed on one surface, and the first lens part is made of a material that has an electro-optic effect and has a curvature formed on one surface. It consists of a second lens part and a transparent electrode for applying a voltage to the first and second lens parts, respectively, and the curvature of the first lens part and the second lens part 1. A lens made of a material having an electro-optic effect, characterized in that the surfaces without the transparent electrode are joined together with the transparent electrode sandwiched therebetween. (5) A lens body made of a material having an electro-optical effect and having a curvature formed on at least one surface, and a transparent electrode formed on the lens body for applying a voltage to the lens body. The lens part is made up of
A lens made of a material having an electro-optic effect, characterized in that it is constructed by connecting a plurality of lenses. (6) A lens made of a material having an electro-optic effect according to any one of claims 1 to 5, wherein the material having an electro-optic effect is PLZT ceramics.