JPH05100201A - Variable focus lens - Google Patents

Abstract

PURPOSE:To form ring band-shaped electrodes without any missing and to make image formation characteristics excellent by forming electrode lead-out lines on a different surface from the ring band-shaped electrodes. CONSTITUTION:On a transparent substrate 101, the electrode lead-out lines 102 are formed. Those electrode lead-out lines 102 are formed of transparent electrode films and a transparent insulating film 103 which is as thick as the electrode lead-out lines 102 are formed except at the pattern of the electrode lead-out lines 102. Then connection parts 104 for connecting the electrode lead- out lines 102 and ring band-shaped electrodes 106 are formed. The electrode lead--out lines 102 are connected to the ring band-shaped electrodes 106 through the connection parts 104. In this case, the ring band-shaped electrodes 106 and the electrode lead-out lines 102 and formed on different surfaces. Then the proper ring band-shaped electrode 106 is selected and applied with a voltage to vary the refractive index of liquid crystal to incident light, and thus a necessary phase distribution is generated to vary the focal length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens structure whose focal length can be changed electrically.

[0002]

2. Description of the Related Art As an example of a conventional variable focus lens, there has been considered a method of forming a Fresnel zone plate using a liquid crystal as described in JP-A-63-249125. The electrode pattern described there is shown in FIG.
The electrode lead-out line 502 is provided by removing a part of the electrode pattern 501.

[0003]

However, there is a problem that a part of the ring-shaped electrode pattern on the Fresnel zone plate is lost, which deteriorates the image forming characteristics.

The present invention solves such a problem, and an object of the present invention is to provide a varifocal lens which is composed of a ring-shaped electrode having no omission and has good image forming characteristics.

[0005]

A first variable focus lens of the present invention is a variable focus lens in which a variable refractive index material is sandwiched between an annular electrode and a counter electrode, and an electrode lead line of the annular electrode is provided. Is in a plane different from that of the ring-shaped electrode.

According to a second variable focus lens of the present invention, in the first variable focus lens, an electrode lead line, a connecting portion connecting the electrode lead line and the ring-shaped electrode, and the ring-shaped electrode are provided. It is characterized in that they are sequentially laminated, and the conductors in each layer are filled with a transparent insulating film having the same thickness as the conductor.

A third variable focus lens of the present invention is characterized in that, in the first variable focus lens, the refractive index variable material is liquid crystal.

A fourth variable focus lens of the present invention is characterized in that, in the first variable focus lens, the widths of the ring-shaped electrodes other than the innermost electrode are equal.

A fifth variable focus lens according to the present invention is characterized in that, in the first variable focus lens, a voltage is applied stepwise to a plurality of adjacent annular electrodes.

A sixth variable focus lens of the present invention is characterized in that, in the first variable focus lens, the ring-shaped electrode has an elliptical pattern.

[0011]

In the Fresnel lens having the lens action due to the periodic structure of the phase, the focal length is determined by the pattern of the periodic structure of the phase. Conversely speaking, the focal length can be changed by changing the pattern of the periodic structure of the phase. A ring-shaped electrode with a thinness determined by how finely the periodic structure of the phase should be changed is prepared, the orientation of the liquid crystal is changed by the voltage applied to this electrode, and the refractive index of the liquid crystal to incident light is changed. The phase is changed by changing. A desired focal length can be obtained by selecting a ring-shaped electrode that matches the pattern of the periodic structure having a phase corresponding to the desired focal length and applying a voltage.

[0012]

【Example】

(Embodiment 1) FIG. 1 is a diagram showing a configuration of a variable focus lens of the present invention. 1A is a cross-sectional view, and FIG. 1B is a plan view in which only the electrodes are extracted and drawn. Figure 1 (a)
Shows the AB cross section of FIG. 1 (b). The number of electrodes in the figure is drawn smaller than it is for the sake of clarity.

On a glass substrate 101 which is a transparent substrate,
The electrode lead wire 102 is formed. Electrode lead wire 1
02 is made of a transparent conductive film. A transparent insulating film 103 having the same thickness as the electrode lead-out line 102 is formed on a portion other than the pattern of the electrode lead-out line 102. Subsequently, a connecting portion 104 for connecting the electrode lead wire 102 and the ring-shaped electrode 106 is formed. The connection portion 104 is made of a transparent conductive film. A transparent insulating film 105 having the same thickness as the connecting portion 104 is formed on the portion other than the pattern of the connecting portion 104.

Further, an annular electrode 106 for controlling the refractive index of the liquid crystal 108 to form a Fresnel lens is formed. The ring-shaped electrode 106 is made of a transparent conductive film. The ring-shaped electrode 1 is formed on the portion other than the pattern of the ring-shaped electrode 106.
A transparent insulating film 107 having the same thickness as 06 is formed.

ITO composed of indium oxide and tin oxide can be used as the transparent conductive film forming the electrode lead wire 102, the connecting portion 104, and the ring-shaped electrode 106.

Further, as the transparent insulating films 103, 105 and 107 for filling the portions other than the pattern of the transparent conductive film, in order to prevent unnecessary diffraction due to the difference in refractive index with the transparent conductive film,
It is optimal to use a material having the same refractive index as that of the transparent conductive film, but in reality, a material having a refractive index as close as possible to the refractive index of the electrode lead line will be used. For example, cerium oxide (CeO ₂ ), silicon oxide (SiO),
Zirconium oxide (ZrO ₂ ) and the like.

The liquid crystal 108 is sealed between the common electrode 109 formed of a transparent conductive film formed on the glass substrate 110, the ring-shaped electrode 106 and the transparent insulating film 107.

The varifocal lens in this embodiment is a Fresnel lens having a lens action due to the periodic structure of the phase, and among them, it is called a blazed Fresnel lens. The operation of the variable focus lens in this embodiment will be described with reference to FIG. The phase distribution of the axisymmetric plus lens is shown in FIG. The horizontal axis represents the radius R of the lens, and the vertical axis represents the phase. The phase changes from the center O of the lens toward the outer periphery of the lens periodically and in a sawtooth shape by 2π. One period in which the phase changes from 0 to −2π is called a zone. The radius Rm of the zone is given by the following equation.

Rm = (2mλf + (mλ) ² ) ^1/2 (1) Here, m is an integer, λ is a wavelength, and f is a focal length. That is, the position of the zone is determined when the focal length f of the lens is determined. Therefore, by calculating Rm that realizes a desired focal length, selecting a ring-shaped electrode corresponding to the pattern, applying a voltage, and changing the refractive index of the liquid crystal with respect to incident light to give a desired phase distribution, The focal length of can be realized. In this case, it is desirable to continuously change the phase in one zone from 0 to −2π, but since the refractive index of the liquid crystal is changed by the discrete annular electrodes, the phase change is also discrete. Therefore, the voltage applied to each ring-shaped electrode is controlled so as to approximate the ideal phase distribution as much as possible. This will be specifically described with reference to FIGS. 2B and 2C.

FIG. 2B shows the distribution of the voltage applied to the ring-shaped electrodes 106 and the respective electrodes when the focal length is f _b . For clarity, only a part of the lens is drawn for drawing. The horizontal axis shows the radius R direction of the lens, and O is the center of the lens. 201
Indicates the voltage distribution.

From the formula (1), the radiuses Rm _b and Rm _b +1 of the zones are Rm _b = (2m _b λf _b + (m _b λ) ² ) ^1/2 (2-1) Rm _b + 1 = (2 (m _b +1) λf _b + ((m _b +1) λ) ² ) ^1/2 (2-2). In order to change the phase between Rm _b and Rm _b +1 from 0 to −2π, a voltage is applied stepwise to the electrode between the annular electrodes Emb1 and Emb2. The steps may have the same magnitude, that is, the voltage may change linearly between the electrodes Emb1 and Emb2, but the steps should be close to the phase distribution shown in FIG. 2 (a). It is desirable to change the size for each electrode.

On the other hand, in FIG. 2C, the focal length f _c (≠
The distribution of the voltage applied to each of the annular electrodes 106 and the respective electrodes in the case of f _b ) is shown. As in FIG. 2B, only a part of the lens is taken out and drawn. The horizontal axis shows the radius R direction of the lens, and O is the center of the lens. Two
02 indicates the voltage distribution.

The radius R of the zone corresponding to the focal length f _c
m _c, Rm _c +1 with the formula _{(1), Rm c = (} 2m c λf c + (m c λ) 2) 1/2 ... (3 over _{1) Rm c + 1 = (} 2 (m c +1 ) Λf _c + ((m _c +1) λ) ² ) ^1/2 (3-2). In order to change the phase between Rm _c and Rm _c +1 from 0 to −2π, a voltage is applied stepwise to the electrode between the annular electrodes Emc1 and Emc2.

As described above, the focal length can be changed by selecting an appropriate ring-shaped electrode, applying a voltage, and changing the refractive index of the liquid crystal with respect to the incident light to create a required phase distribution.

The width of each ring-shaped electrode 106 must be thin enough to cope with the change in the phase distribution, and it is desirable that the width is equal to the required resolution over the entire lens surface. However, since the size of the innermost ring zone does not become smaller than a certain size, the innermost ring-shaped electrode 11
The radius of 1 does not have to be as small as the width of the other annular electrodes.

(Embodiment 2) The varifocal lens in this embodiment is a blazed Fresnel lens as in Embodiment 1, but the annular electrode 301 has an elliptical pattern as shown in FIG. FIG. 3 is a plan view of the ring-shaped electrode, and the number of electrodes in the drawing is drawn smaller than it actually is for the sake of clarity.
It differs from the lens of Example 1 only in the planar shape of the annular electrode and the electrode lead-out line.

The focal length of a Fresnel lens having an elliptical pattern differs in the Y and X directions in the figure. Therefore, the focal length in the Y direction and the focal length in the X direction can be changed by changing the voltage pattern applied to the annular electrode 301.

(Embodiment 3) The varifocal lens in this embodiment is a Fresnel lens having a lens action due to the periodic structure of the phase as in Embodiments 1 and 2, but is called a binary Fresnel lens among them. It is what has been. The operation of the variable focus lens in this embodiment will be described with reference to FIG.

FIG. 4 shows the phase distribution of an axisymmetric plus lens.
It shows in (a). The horizontal axis represents the radius R of the lens, and the vertical axis represents the phase. The phase periodically changes by π from the center O of the lens toward the outer circumference of the lens. One period in which the phase changes from 0 to −π is called a zone.
The radius Rn at which the phase changes is given by the following equation.

Rn = (nλf + (nλ / 2) ² ) ^1/2 (4) Here, n is an integer, λ is a wavelength, and f is a focal length. That is, the position of the zone is determined when the focal length f of the lens is determined. Therefore, if Rn that realizes a desired focal length is calculated, a ring-shaped electrode corresponding to the pattern is selected, a voltage is applied, the refractive index of the liquid crystal with respect to incident light is changed, and a desired phase distribution is obtained, The focal length of can be realized. This will be specifically described with reference to FIGS. 4B and 4C.

FIG. 4B shows the distribution of the voltage applied to each of the annular electrodes 106 and the respective electrodes when the focal length is f _b . For clarity, only a part of the lens is drawn for drawing. The horizontal axis shows the radius R direction of the lens, and O is the center of the lens. 401
Indicates the voltage distribution.

The radius Rn _b to invert the phase, Rn _b +1 with the formula _{(4), Rn b = (} n b λf b + (n b λ / 2) 2) 1/2 ... (5 over 1) Rn _b is a _{+1 = ((n b +1)} λf b + ((n b +1) λ / 2) 2) 1/2 ... (5-2). In order to change the phase between Rn _b and Rn _b +1 by π, it suffices to change the refractive index of the liquid crystal with respect to the incident light. This can be achieved by changing the voltage applied to the annular electrode between Enb1 and Enb2. realizable. A ring-shaped electrode is selected from the center O of the lens toward the outermost circumference of the lens according to the pattern determined by the equation (4), and a voltage is applied to form a desired phase distribution.

On the other hand, in FIG. 4C, the focal length f _c (≠
The distribution of the voltage applied to each of the annular electrodes 106 and the respective electrodes in the case of f _b ) is shown. Similar to FIG. 4B, only a part of the lens is taken out and drawn. The horizontal axis shows the radius R direction of the lens, and O is the center of the lens. Four
02 indicates the voltage distribution.

From the formula (4), the radii Rn _c and Rn _c +1 for inverting the phase are calculated as follows: Rn _c = (n _c λf _c + (n _c λ / 2) ² ) ^1/2 ... (6-1) Rn _c + 1 = ((n _c +1) λf _c + ((n _c +1) λ / 2) ² ) ^1/2 (6-2). In order to change the phase between Rn _c and Rn _c +1 by π, the voltage applied to the annular electrode between Enc1 and Enc2 may be changed.

As described above, the focal length can be changed by selecting an appropriate ring-shaped electrode, applying a voltage, and changing the refractive index of the liquid crystal with respect to the incident light to create a necessary phase distribution.

The transmittance of the lens is higher in the blazed Fresnel lens of the first embodiment than in the binary Fresnel lens of the present embodiment.

Although the embodiments of the variable focus lens of the present invention have been described above, the variable focus lens of the present invention can be applied to a lens of an optical head for an optical disc, a lens for a laser beam printer, or a spectacle lens. Is. Also,
The structure in which the ring-shaped electrode and the extraction electrode are composed of different layers, and the gap between the electrodes is filled with an insulating film to be flattened can be applied to a reflection type variable focus mirror.

It is also possible to control aberrations by forming a zone pattern corresponding to an aspherical lens with the ring-shaped electrode.

[0039]

As described above, according to the present invention, by forming the electrode lead wire on the surface different from the ring-shaped electrode, it is possible to form a ring-shaped electrode without any omission.

Therefore, there is an effect that good imaging characteristics can be obtained.

Further, an electrode lead wire, a connecting portion connecting the electrode lead wire and the ring-shaped electrode, and a ring-shaped electrode are sequentially laminated, and a transparent insulating film having the same thickness as these conductors is provided between the conductors in each layer. By filling in with, it is possible to prevent the disconnection of the conductor by eliminating the step and to suppress the generation of unnecessary diffracted light.

Further, by making the widths of the ring-shaped electrodes equidistant in portions other than the innermost electrode, it is possible to form an arbitrary phase distribution.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a variable focus lens of the present invention. (A) is sectional drawing. (B) is a plan view showing only electrodes. (A) is an AB cross section of (b).

FIG. 2 is a diagram for explaining the operation of the variable focus lens in the first example of the variable focus lens of the present invention. (A)
FIG. 4 is a diagram showing a phase distribution of a lens. FIG. 6B is a diagram showing the distribution of the voltage applied to the ring-shaped electrode when the focal length is f _b .
(C) is a figure which shows the distribution of the voltage applied to a ring-shaped electrode in the case of a focal length f _c .

FIG. 3 is a plan view showing a pattern of ring-shaped electrodes in a second embodiment of the variable focus lens of the present invention.

FIG. 4 is a diagram for explaining the operation of the variable focus lens in the third example of the variable focus lens of the present invention. (A)
FIG. 4 is a diagram showing a phase distribution of a lens. FIG. 6B is a diagram showing the distribution of the voltage applied to the ring-shaped electrode when the focal length is f _b .
(C) is a figure which shows the distribution of the voltage applied to a ring-shaped electrode in the case of focal length f _c .

FIG. 5 is a diagram showing an electrode pattern in a conventional variable focus lens.

[Explanation of symbols]

 101, 110 glass substrate 102 electrode lead wire 103, 105, 107 transparent insulating film 104 connection portion 106 ring-shaped electrode 108 liquid crystal 109 common electrode 111 innermost ring-shaped electrode 201, 202 voltage distribution Rm, Rm + 1, Rmb, Rmb + 1, Rmc, Rmc + 1 Zone radii Emb1, Emb2, Emc1, Emc2 Center of ring-shaped electrode O lens R Radius 301 Ring-shaped electrode 401, 402 Voltage distribution Rn, Rn + 1, Rnb, Rnb + 1, Rnc, Rnc + 1 Radius Enb1, Enb2, Enc1, Enc2 Ring-shaped electrode 501 Electrode pattern 502 Electrode lead wire

Claims (6)

[Claims] 1. A variable focus lens in which a variable refractive index material is sandwiched between a ring-shaped electrode and a counter electrode, wherein an electrode lead line of the ring-shaped electrode is in a plane different from that of the ring-shaped electrode. Variable focus lens. 2. An electrode lead wire, a connecting portion connecting the electrode lead wire and the ring-shaped electrode, and the ring-shaped electrode are sequentially laminated, and a transparent insulating film having the same thickness as the conductor is provided between the conductors in each layer. The variable focus lens according to claim 1, wherein the variable focus lens is filled with. 3. The variable focus lens according to claim 1, wherein the variable refractive index material is liquid crystal. 4. The variable focus lens according to claim 1, wherein the annular electrodes other than the innermost electrode have the same width. 5. The variable focus lens according to claim 1, wherein a voltage is applied stepwise to a plurality of adjacent annular electrodes. 6. The variable focus lens according to claim 1, wherein the ring-shaped electrode has an elliptical pattern.