CN101010619A - Optical element - Google Patents

Abstract

By performing electrical control in the optical element, the focal length can be greatly changed. The optical element includes: a first substrate (111) having a first electrode (21); a second substrate (112); a second electrode (22) disposed outside the second substrate; and a liquid crystal layer (311) disposed between the first substrate and the second substrate and composed of aligned liquid crystal molecules. A first voltage (Vo) is applied between the first electrode and the second electrode, thereby controlling the alignment of the liquid crystal molecules, thereby operating the optical element. A third electrode (23) is disposed over the insulating layer and outside the second electrode. A second voltage (Vc) independent of the first voltage (Vo) is applied to the third electrode, thereby changing the optical characteristics.

Description

Optical element

technical field

The present invention relates to an optical element in which two different voltages are applied between electrodes provided on a substrate constituting a liquid crystal cell and electrodes provided outside the substrate, thereby controlling the orientation of liquid crystal molecules, and a specific optical element can be easily adjusted. characteristic.

Background technique

Liquid crystals have fluidity like liquids and exhibit anisotropy in electro-optical properties. The orientation of liquid crystal molecules can be controlled in various ways. In recent years, there has been remarkable progress in developing thin and light-weight, flat-type display devices utilizing the properties of liquid crystals. If two glass plates constituting a liquid crystal element and having a transparent conductive film are surface-treated, and if a voltage is applied from the outside, the orientation of liquid crystal molecules can be easily controlled. The refractive index of any such liquid crystal element can vary continuously between its value at which it appears extraordinary to its value at which it appears ordinary. This is an excellent characteristic that other optical materials cannot present.

Variable-focus lenses each of which has a variable effective refractive index have been proposed (see Patent Document 1 and Non-Patent Documents 1 and 2). By utilizing the electro-optic effect of nematic liquid crystals, glass substrates with transparent electrodes can be bent. Therefore, the liquid crystal layer is shaped like a lens, not like in an element structure included in a general liquid crystal display. A voltage is applied across the electrodes to control the orientation of the liquid crystal molecules. Thus, the effective refractive index of the lens is changed.

A method may be used in which a spatial distribution of refractive index is imparted to an optical medium so as to obtain a lens effect. Such optical media known as SELFOC (GRIN) lenses are commercially available. In a nematic liquid crystal cell, the liquid crystal molecules are aligned along the direction of the electric field. A method of providing a liquid crystal lens exhibiting a spatially distributed refractive index has been published (see Patent Document 2, Patent Document 3, and Non-Patent Documents 3 and 4). In these methods, an axisymmetric non-uniform electric field is generated using electrodes having a circular pattern, and such a liquid crystal lens is obtained by utilizing the effect of liquid crystal molecule alignment.

Just as Patent Document 4 discloses a network polymer network in liquid crystals in order to improve the performance of liquid crystals. It is relatively easy to modify such a lens using liquid crystals to a microlens array comprising a plurality of tiny, so-called microlenses arranged two-dimensionally, thereby forming a flat plate.

It has been proposed that, in a liquid crystal microlens, a pair of electrodes should be provided outside the electrodes of a circular pattern in order to improve the performance of the lens (see Non-Patent Document 5). In addition, a method has been proposed in which an insulating layer is interposed between the liquid crystal layer and the electrode having a circular pattern, and the ratio of the diameter of the circular pattern to the thickness of the liquid crystal layer should be 2:1 to about 3:1. In order to impart the best performance to the requirements of microlenses (see Non-Patent Documents 6 and 7).

On the other hand, an optical device using a liquid crystal element instead of a lens mirror has been proposed (see Patent Document 5). In this apparatus, an imaging device detects an optical image obtained by an optical system having a focusing unit having an aberration correction mechanism, and determines the aberration using a signal generated by the imaging device. Signals for correcting aberrations are generated, whereby aberrations occurring in the optical system due to atmospheric fluctuations are corrected to provide an optical image without distortion. Also, an electric field controlled anamorphic liquid crystal lens having an elliptical distribution of refractive index has been proposed as a lens using a liquid crystal optical element (see Non-Patent Document 8).

Unlike ordinary optical elements that are passive elements, these optical elements using liquid crystals can provide lenses that can adjust properties such as focal length and aberration of the optical system.

A polymer curable liquid crystal can be used as the liquid crystal material. In this case, liquid crystals are polymerized, and thereby solidified, to provide a polymer lens after focus adjustment (see Patent Document 6).

Patent Document 1: Japanese Patent Application KOKAI Publication No. 54-151854

Patent Document 2: Japanese Patent Application KOKAI Publication No. 11-109303

Patent Document 3: Japanese Patent Application KOKAI Publication No. 11-109304

Patent Document 4: Japanese Patent Application KOKAI Publication No. 10-239676

Patent Document 5: Japanese Patent Application KOKAI Publication No. 03-265819

Patent Document 6: Japanese Patent Application KOKAI Publication No. 09-005695

Non-Patent Document 1: S. Sato, "Liquid-crystal lens-cell with variable focal length", Japanese Journal of Applied Physics, 1979, Vol. 18, pp. 1679-1683

Non-Patent Document 2: S. Sato, "Liquid crystals and application thereof", Sangyo Tosho Co., Ltd., October 14, 1984, pp. 204-206

Non-Patent Document 3: T. Nose and S. Sato, "A liquid-crystal micro lens obtained with a non uniform electric field", Liquid Crystals, 1989, pp. 1425-1433

Non-Patent Document 4: S. Sato, "The World of liquid crystal", Sangyo Tosho Co., Ltd., April 15, 1994, pp. 186-189

Non-Patent Document 5: M. Honma, T. Nose and S. Sato, "Enhancement of numerical aperture of liquid crystal microlenses using a stacked electrode structure", Japanese Journal of Applied Physics, August 2000, Volume 39, No.8, Pages 4799-4802

Non-Patent Document 6: M. Ye and S. Sato, "Optical properties of liquid crystallens of any size", Preliminary reports, 49th meeting of the Applied Physics Society, March 2002, 28p-X-10, p. 1277

Non-Patent Document 7: M. Ye and S. Sato, "Optical properties of liquid crystallens of any size", Japanese Journal of Applied Physics, May 2002, Vol. 41, No. 5, pp. L571-L573

Non-Patent Document 8: Y.Yokoyama, M.Ye and S.Sato, "Electrically controllable liquid crystal anamorphic lens", 2004 preliminary reports, meeting of the Society of Liquid Crystal, Japan, September 26, 2004

Contents of the invention

All of the above: a liquid crystal lens with a lens-shaped liquid crystal layer; a liquid crystal microlens utilizing the spatial refractive index distribution of liquid crystal molecules, which is obtained by an axisymmetric non-uniform electric field and produced by a circular pattern of electrodes; a A method as proposed in Non-Patent Document 5, in which a pair of electrodes are provided outside the circular pattern electrodes; and a structure as proposed in Non-Patent Documents 6 and 7, in which an insulating layer is provided between the liquid crystal layer and the circular pattern Between electrodes, these can obtain good optical characteristics. However, they all have problems. They can hardly achieve good performance over a wide range of applied voltages.

Accordingly, an object of one embodiment of the present invention is to provide an optical element having good optical characteristics that can be easily and greatly changed while being maintained.

It is an object of another embodiment of the present invention to provide an optical element whose focal point can be moved in three dimensions.

It is an object of another embodiment of the present invention to provide optical properties like this which can be controlled for convex or concave lenses.

In order to solve the above-mentioned problems, the optical element according to the present invention mainly includes a first substrate having a first electrode, a second substrate, a second electrode disposed outside the second substrate and having a hole, and a liquid crystal layer, wherein the liquid crystal layer is disposed on Between the first substrate and the second substrate and composed of liquid crystal molecules aligned in one direction. The first voltage is applied between the first electrode and the second electrode to control the alignment of the liquid crystal molecules, thereby operating the optical element. In the optical element, a third electrode is provided outside the second electrode and above the insulating layer, and a second voltage independent of the first voltage is applied to the third electrode, thereby controlling the optical characteristic.

Thanks to the arrangement described above, the focus position can be changed greatly by electrical control without mechanically moving the lens back and forth as in conventional optics.

Description of drawings

1A is a cross-sectional view showing the structure of an embodiment of an optical element according to the present invention;

1B is a plan view showing the structure of an embodiment of an optical element according to the present invention;

Figure 2 is a view showing the potential distribution in the element, and thereby explains the function of the optical element according to the present invention;

FIG. 3A is a view showing a first example in which potential distribution varies in the optical element according to the present invention, and thereby explains the function of the optical element;

3B is a view showing a second example in which the potential distribution is changed in the optical element according to the present invention, and thereby explains the function of the optical element;

4 is a view showing how the optical phase of a light wave passing through the optical element according to the present invention changes as viewed along the optical axis of the optical element;

5 is a view showing how the optical phase of light waves passing through the optical element according to the present invention changes, and thereby explains the function of the optical element;

Figure 6 is a diagram showing how the focal length varies with the control voltage and thereby illustrates the function of the optical element;

7 is a cross-sectional view showing the structure of another embodiment of an optical element according to the present invention;

8A is a cross-sectional view showing the structure of another embodiment of an optical element according to the present invention;

8B is a plan view showing the structure of another embodiment of an optical element according to the present invention;

9A is a cross-sectional view showing the structure of another embodiment of an optical element according to the present invention;

9B is a plan view showing the structure of other embodiments of the optical element according to the present invention;

FIG. 10A is a view illustrating a specific structure of the control unit shown in FIG. 9;

FIG. 10B is a view illustrating how the focus of the liquid crystal lens moves in the control unit shown in FIG. 9;

FIG. 11 is a view showing the actually measured potential applied to the split electrode (splitelectrode) shown in FIG. 10 and the movement of the focus along the x direction;

12 is a view showing actually measured potentials applied to the divided electrodes shown in FIG. 10 and movement of the focal point in the y direction;

FIG. 13 is a view showing the potential applied to the split electrode shown in FIG. 10 and the movement of the focal point in a direction at an angle to the x direction and the y direction, the potential and the movement being actually measured;

14A is a cross-sectional view showing the structure of another embodiment of an optical element according to the present invention;

14B is a plan view showing the structure of another embodiment of an optical element according to the present invention;

Figure 15 is a view showing the potential distribution in the optical element of Figures 14A and 14B, and thereby explains the function of the optical element;

FIG. 16A is a view showing a first example in which the potential distribution varies in the optical element of FIGS. 14A and 14B, and thereby explains the function of the optical element;

FIG. 16B is a view showing a second example in which the potential distribution varies in the optical element of FIGS. 14A and 14B , and thereby explains the function of the optical element;

Fig. 17 is a view showing how the optical phase of a light wave passing through the optical element of Fig. 14 changes, and thereby explains the function of the optical element;

Fig. 18 is a view showing how the focal length varies with the control voltage, and thereby illustrates the function of the optical element shown in Fig. 14; and

Fig. 19 is a view showing the structure of another embodiment of the optical element according to the present invention.

Detailed ways

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In FIGS. 1A and 1B , numeral 111 designates a first substrate (transparent glass plate). The first electrode 21 (made of ITO) is formed on the inner surface of the first substrate 111 . On one side of the first electrode 21, a second substrate 112 (transparent glass plate) is disposed facing the first electrode 21 and extending parallel thereto. On the outside of the second substrate 112, a second electrode 22 (made of aluminum) is formed. As shown in FIG. 1B , the second electrode 22 has a circular hole 222 (eg, 4.5 mm in diameter).

A liquid crystal layer 311 (for example, with a thickness of 130 μm) is formed between the first electrode 21 and the second substrate 112 on which the first electrode 21 is formed. Reference numerals 41 and 42 denote spacers defining the liquid crystal layer 311 .

In addition, an insulating layer 113 (eg, a glass layer as thin as 70 μm) is located on the upper surface of the second electrode 22 , and a third electrode 23 (made of ITO) is formed on the insulating layer 113 . A protective layer 114 (made of glass) is provided on the upper surface of the third electrode 23 . Those surfaces of the first and second substrates which contact the liquid crystal layer were coated with polyimide and rubbed in the x-axis direction.

In order for the optical element to function as a liquid crystal lens, a first voltage Vo is applied between the first electrode 21 and the second electrode 22 . To apply the first voltage Vo, the second voltage Vc is initially set to 0V and the first voltage Vo is set to an appropriate value. The voltage applying unit 51 applies a voltage Vo. The voltage is set to a value that imparts optimum optical characteristics (hereinafter referred to as primary optical characteristics) to the lens. Next, a second voltage Vc independent of the first voltage Vo is applied between the first electrode 21 and the third electrode 23 . The voltage applying unit 52 outputs the second voltage Vc. If the second voltage Vc is varied, the optical characteristics of the lens (hereinafter referred to as second-order optical characteristics) can be controlled. It should be noted that Vo and Vc are identical in frequency and phase.

In the present invention, the second order optical properties vary from values with very short focal lengths to values with infinite or nearly infinite focal lengths. Focal lengths can vary over a wide range. Therefore, the present invention is valuable in practice and can be applied in various applications.

Figure 2 shows the potential distribution in the space between the first and second electrodes when Vo=70V (fixed value for best performance) is applied between the first electrode 21 and the second electrode 22 And it is observed when the second voltage (control voltage) Vc=10V is applied to the third electrode 23 . In FIG. 2, z is the direction of the optical axis, and y is the direction intersecting the optical axis at right angles. It should be noted that z, y and x are exactly the same as z, y and x shown in FIG. 1 . If the equipotential lines define a steep gradient, the focal length of the lens is short. If they define a gentle gradient, the focal length of the lenses is long.

3A and 3B show other potential distributions, ie two potential distributions that can be observed in the liquid crystal layer. 3A shows that when Vo=70V (fixed value for best performance) is applied between the first electrode 21 and the second electrode 22 and a second voltage is applied between the first electrode 21 and the third electrode 23 ( Potential distribution observed when control voltage) Vc=10V. FIG. 3B shows potential distributions observed when the control voltage is varied and the second voltage (control voltage) Vc=20V is applied. This change in potential distribution corresponds to the inclination angle of the liquid crystal molecules and to the refraction angle of light. The focal length in the state of FIG. 3B is longer than that in the state of FIG. 3A .

In FIG. 4, A, B, C and D show how the phases of light waves observed at the optical axis of the optical element according to the present invention are distributed. More specifically, A, B, C, and D show that when the control voltage Vc applied to the third electrode 23 is changed to 0V, 20V, 40V, and 60V, while the fixed voltage Vo=70V is applied to the first electrode 21 and the second electrode 22, how does the phase distribution of the light wave change. As seen from A to D in FIG. 4, the higher the control voltage Vc, the longer the interval between the interference fringes. The longer the interval between the interference fringes, the less pronounced the refraction of light and thus the longer the focal length.

Figure 5 shows how a light wave passing through a liquid crystal lens achieves an optical phase retardation φ. Basically, the light has a square distribution characteristic. Therefore, its phase delay gradually decreases outward from the y-axis. When the control voltage (second voltage) increases, the phase difference between the center of the lens and its periphery decreases. Therefore, the focal length at Vc=50V is longer than that at Vc=10V.

FIG. 6 shows the relationship between the focal length change of the optical element according to the present invention and the above-mentioned control voltage Vc. When the control voltage Vc changes, the focal length also changes. The present invention is not limited to the above-described embodiments.

Fig. 7 shows the structure of another embodiment of the present invention. Components that are the same as those shown in FIG. 1 are denoted by the same reference numerals. This embodiment differs from the first embodiment in the structure of the liquid crystal layer 311 . In this embodiment, the liquid crystal layer 311 includes a first liquid crystal layer 311a, a second liquid crystal layer 311b and an insulating layer 312 (made of transparent glass). The first and second liquid crystal layers 311a and 311b are separated by an insulating layer 312 interposed therebetween.

Configured in this way, the liquid crystal layer 311 can respond at a very high speed. The response speed of any liquid crystal layer is inversely proportional to the square of the thickness of that layer. Thus, this layer 311 can respond to control signals four times faster than the element of FIG. 1 because it comprises two liquid crystal layers, a first layer 311a and a second layer 311b.

Due to having a two-layer structure, the liquid crystal layer 311 can obtain the following advantages. If the liquid crystal layers 311a and 311b have been rubbed in the same direction, the liquid crystal molecules are aligned in the same direction in both layers 311a and 311b. As a result, the lens can achieve twice the magnification of a single-layer lens. In other words, when the two lenses are combined, they achieve the same effect and thus a shorter focal length.

In addition, if the liquid crystal layers 311a and 311b are rubbed all the time in two directions intersecting at right angles, respectively, the lens can be used as a liquid crystal cell without a polarizing plate.

8A and 8B illustrate another embodiment of the present invention. The optical element comprises two elements identical to those shown in FIG. 7 . It is a double-unit structure having an upper unit and a lower unit symmetrical to each other. The same components (first element units) as those shown in FIG. 7 are denoted by the same reference numerals. The first and second element units share the second and third electrodes 22 and 23 . The second element unit is located above the first element unit. The second element unit has substrates 111-2 and 112-2, electrodes 21-2, a first liquid crystal layer 311a-1, a second liquid crystal layer 311b-2, an insulating layer 312-2, a common second electrode 22, and a common third electrode 23. In this embodiment, the gap G is located between the second electrode 22 and the third electrode 23 because these electrodes 22 and 23 are located on the same plane. The second electrode 22 has a cutout 23a extending from its hole to one side thereof. An outer lead line 23a is guided from the third electrode 23 through the cutout 23a. The control voltage Vc is applied through the outer lead 23a.

Each of the upper and lower liquid crystal layers that are symmetrical to each other may include two or more layers. If so, the lens capabilities and responsiveness will be further improved.

In the present invention, the liquid crystal layer can be made of a dual-frequency driving type material, that is, it acts as an N-type when driven by a high-frequency signal (a dozen kilohertz) and a P-type when driven by a low-frequency signal (about 100 Hz). effect. If the liquid crystal layer is made of such a material, the response speed of the alignment operation of liquid crystal molecules can be improved.

9A and 9B illustrate another embodiment of the present invention. In the embodiment shown in FIGS. 1A and 1B , a fixed voltage is applied to the second electrode 22 . In this embodiment, the second electrode 22 is divided into two or more segments, for example, four electrode segments 22a to 22d as shown in FIG. 9B. Minor changes in the voltage applied to these electrodes can be made by the control unit 55 . In other respects, this embodiment is the same as the embodiment of FIGS. 1A and 1B .

FIG. 10A shows the structure of the control unit 55 . FIG. 10B illustrates how the focus moves when the control unit 55 controls the focus position.

The voltage applied to the electrode segment 22a comes from the wiper of the variable resistor 55a. Its value varies from voltage +V to voltage -V. Similarly, the voltage applied to electrode 22b comes from the wiper of variable resistor 55b and ranges from voltage +V to voltage -V; the voltage applied to electrode 22c comes from the wiper of variable resistor 55c and Varies in the range of voltage +V to voltage -V; and the voltage applied to electrode 22d comes from the wiper of variable resistor 55d and ranges in voltage +V to voltage -V.

When the voltage applied to the electrode segments 22a to 22d is slightly changed, the focal point can move in the x-axis direction or the y-axis direction or both directions. In addition, the focal point can be moved in the z-axis direction. Therefore, the position of the focal point can be controlled in three dimensions.

In Fig. 11, A and B show how to control the focus position along the x-axis direction while fixing it in the focal plane by adjusting the voltage Vc. More specifically, A in FIG. 11 shows how the focus moves in space when the voltage applied to the second electrode 22 varies. B in FIG. 11 shows where the focal point is within the focal plane.

In Fig. 12, A and B show how to control the focus position along the y-axis direction. More specifically, A in FIG. 12 shows how the focal point moves in space when the voltage applied to the second electrode 22 varies. B in FIG. 12 shows the distance by which the focus moves.

In FIG. 13, A and B show how to control the focus position along the x-axis direction and the y-axis direction. That is, A in FIG. 13 shows the voltage applied to the second electrode 22, and B in FIG. 13 shows the distance by which the focus moves.

The present invention is not limited to the above-described embodiments. In these embodiments, the liquid crystal lens acts as a convex lens. However, according to the present invention, it is also possible to easily operate the liquid crystal lens as a concave lens.

14A and 14B show an embodiment in which the liquid crystal lens functions as a concave lens. In this case, the voltage applying unit 61 applies a constant AC voltage Vo between the first electrode 21 and the third electrode 23 , and the voltage applying unit 62 applies the voltage Vc between the first electrode 21 and the second electrode 22 . The voltage Vc can vary. In every other respect, this embodiment is the same as the embodiment shown in Figs. 1A and 1B.

Fig. 15 has described a kind of electric potential distribution, this is when the voltage Vo=60V (namely, is used for obtaining the fixed value of optical characteristic) is applied between the first electrode 21 and the third electrode 23 and between the first electrode 21 and the second electrode 23 The potential distribution observed when the second voltage (control voltage) Vc=10V is applied between the electrodes 22 . In FIG. 15, z is the direction in which the optical axis extends, and y is the direction intersecting the optical axis at right angles. It should be noted that z, y and x are the same as their equivalents shown in Figures 1A and 1B. The potential distribution is the opposite of that shown in Figure 2. This means that the liquid crystal lens functions as a concave lens.

16A and 16B show different potential distributions. 16A shows that when Vo=60V (fixed value for obtaining optical characteristics) is applied between the first electrode 21 and the third electrode 23 and the second voltage (control voltage) Vc=5V is applied to the second electrode 22 The potential distribution observed at . FIG. 16B shows potential distributions observed when the second voltage (control voltage) Vc was changed to 20 V and applied. The change in this potential difference corresponds to the tilt angle of the liquid crystal molecules and also corresponds to the refraction angle of light. The potential distribution shown in FIGS. 16A and 16B is opposite to the potential distribution shown in FIGS. 3A and 3B . This means that the liquid crystal lens functions as a concave lens.

FIG. 17 shows how light has an optical phase retardation φ when passing through a liquid crystal lens. Basically, the phase retardation of this light wave has a quadratic distribution characteristic. Therefore, its phase delay gradually decreases outward from the y-axis. When the control voltage (second voltage) is changed, the phase difference between the center of the lens and its periphery is controlled. That is, the concave lens characteristics may vary.

Fig. 18 is a graph showing how the focal length varies with the above-mentioned control voltage Vc. When the control voltage Vc changes, the focal length also changes.

The present invention is not limited to the above-mentioned embodiment in which the liquid crystal lens is a convex lens or a concave lens. In the present invention, a convex lens and a concave lens may be used in combination.

Figure 19 shows a multifunctional lens that is an implementation of the embodiment of Figures 1A and 1B (i.e., used as a convex lens) and the embodiment of Figures 9A and 9B (i.e., the focus position can be controlled in three dimensions. example) and a combination of the embodiment of FIGS. 14A and 14B (ie, the embodiment used as a concave lens). The function of the lens can be switched between a convex lens function and a concave lens function by switches 64 and 65 . When the lens is used as a convex lens, it is possible to finely adjust the voltage applied to the segments of the second electrode independently of each other, thereby adjusting the focus three-dimensionally. When the lens is used as a concave lens, the voltages applied to the segments of the second electrode can be controlled independently of each other.

The present invention is not limited to the above-described embodiments. The components of any one embodiment may be modified in various ways to bring the invention to practice without departing from the spirit or scope of the invention. Furthermore, components of any of the above-described embodiments may be combined in various ways to obtain different inventions, if necessary. For example, some components of either embodiment may not be used. Furthermore, components of different embodiments may be combined in any desired manner. The shape of the third electrode may be defined by a sine wave function, a superposition function of sine wave functions, or any power function. In the above embodiments, there is one liquid crystal lens. However, a plurality of liquid crystal lenses can be arranged to form a linear array or a two-dimensional array.

Industrial Applicability

The optical element according to the present invention can be used in various ways. They can be used as magnifying lenses or in vision units used in robots.

Claims (12)

1. An optical element comprising: a first substrate having a first electrode; a second substrate; a second electrode disposed outside the second substrate and having a hole; and a liquid crystal layer disposed on the first substrate between and said second substrate and composed of aligned liquid crystal molecules, and wherein a first voltage is applied between said first electrode and said second electrode to control the orientation of said liquid crystal molecules, It is characterized in that the third electrode is arranged on the insulating layer and outside the second electrode, and is configured to receive a second voltage independent of the first voltage; and the first voltage has the optimum first voltage A primary optical characteristic is assigned a fixed value to the optical element, and the second voltage is varied to vary the secondary optical characteristic of the optical element. 2. An optical element comprising: a first substrate having a first electrode; a second substrate; a second electrode disposed outside the second substrate and having a hole; and a liquid crystal layer disposed on the first substrate between and said second substrate and composed of aligned liquid crystal molecules, and wherein a first voltage is applied between said first electrode and said second electrode to control the orientation of said liquid crystal molecules, It is characterized in that the third electrode is arranged on the insulating layer and outside the second electrode, and is configured to receive a second voltage independent of the first voltage; and the second voltage has the optimal first voltage A primary optical characteristic is assigned a fixed value to the optical element, and the first voltage is varied to vary a secondary optical characteristic of the optical element. 3. The optical element according to claim 1 or 2, wherein the second electrode having a hole is divided into a plurality of electrode segments surrounding the optical axis, and control voltages independent of each other are applied to these electrode segments respectively superior. 4. The optical element according to claim 1 or 2, characterized in that the shape of the third electrode is defined by a sine wave function, a superposition function of a sine wave function or an arbitrary power function. 5. The optical element according to claim 1 or 2, characterized in that one insulating layer divides the liquid crystal layer into a first liquid crystal layer and a second liquid crystal layer, or a plurality of insulating layers divides the liquid crystal layer into a plurality of liquid crystal layers layer. 6. The optical element according to claim 1 or 2, characterized in that one or more insulating layers divide the liquid crystal layer into several liquid crystal layers arranged to orient the liquid crystal molecules parallel to each other or perpendicular to each other. 7. The optical element according to claim 1 or 2, characterized in that the liquid crystal layer is formed into a dual-frequency drive type, which acts as an N-type when driven by a high-frequency signal and as a P-type when driven by a low-frequency signal. type effect. 8. An optical element, characterized in that it comprises: a first substrate having a first electrode on an inner surface; a second substrate facing the inner surface of the first substrate; a second electrode disposed outside the first substrate and having a hole; a first liquid crystal layer disposed between the first substrate and the second substrate and composed of liquid crystal molecules; a third electrode disposed through an insulating portion and connected to said second electrode; a third substrate configured to be symmetrical to the second substrate with respect to the third electrode; The fourth substrate has a second liquid crystal layer and a third liquid crystal layer, and the second liquid crystal layer and the third liquid crystal layer are respectively arranged relative to the second and third electrodes and the third substrate and the first liquid crystal a layer is symmetrical to said first substrate; and for applying a first voltage between said first and second electrodes and between said second and fourth electrodes and for applying a second voltage independent of said first voltage to said third Electrode device. 9. The optical element according to claim 8, wherein an insulating layer divides the first liquid crystal layer into a third liquid crystal layer and a fourth liquid crystal layer, and an insulating layer divides the second liquid crystal layer into a third liquid crystal layer and the fourth liquid crystal layer. 10. The optical element according to claim 8, characterized in that said third electrode is arranged spaced apart from said aperture of said second electrode. 11. An optical element comprising: a first substrate having a first electrode; a second substrate; a second electrode disposed outside the second substrate and having a hole; and a liquid crystal layer disposed on the first substrate and between the second substrate and composed of aligned liquid crystal molecules, wherein a first voltage is applied between the first electrode and the second electrode to control the alignment of the liquid crystal molecules, Wherein, the third electrode is disposed on the insulating layer and outside the second electrode, and is configured to receive a second voltage independent of the first voltage; a circuit for changing the second voltage is provided, while the circuit enables said first voltage is maintained at a fixed value, thereby controlling optical properties such that said optical element acts as a convex lens; and providing a circuit for varying said first voltage while maintaining said second voltage at a fixed value, The properties are thereby controlled so that the optical element acts as a concave lens. 12. An optical element comprising: a first substrate having a first electrode; a second substrate; a second electrode disposed outside the second substrate and having a hole; and a liquid crystal layer disposed on the first substrate and between the second substrate and composed of aligned liquid crystal molecules, wherein a first voltage is applied between the first electrode and the second electrode to control the alignment of the liquid crystal molecules, wherein the third electrode is disposed on the insulating layer and outside the second electrode and is configured to receive a second voltage independent of the first voltage; a first circuit is provided which maintains the first voltage at fixing a value, thereby optimizing a first state optical characteristic based on said first voltage, and varying said second voltage, thereby optimizing a second stage optical characteristic; providing a second circuit which keeps said second voltage at a fixed value, thereby optimizing third-state optical characteristics based on said second voltage, and varying said first voltage, thereby optimizing fourth-order optical characteristics; and providing a switch performed between said first circuit and said second circuit switch between.

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