JP2006091392A - Electric-field-controlled anamorphic liquid crystal lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously and variably control the shape and direction of an ellipse and a focal distance by forming elliptic refractive index distribution. <P>SOLUTION: A liquid crystal lens is provided with: a first substrate having a first electrode; a second substrate; a second electrode arranged on the outside of the second substrate and forming a circular hole type pattern; and a liquid crystal layer stored between the first and second substrates and orienting liquid crystal molecules: and allowed to be driven by applying voltage between the first electrode and the second electrode and controlling the orientation of the liquid crystal molecules. The second electrode is divided into a plurality of parts by slits formed continuously to the hole type pattern part and potential distribution is formed by applying voltage for setting a pair of electrodes opposed to each other in the diameter direction of the hole type pattern to the same potential to variably control optical characteristics on the basis of elliptic refractive index distribution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the liquid crystal lens having an elliptical refractive index spatial distribution characteristic, the present invention can vary the major axis direction of the ellipse and the ratio of the major axis to the minor axis by voltage, and easily adjust the focal length characteristic. The present invention relates to an electric field control anamorphic liquid crystal lens.

  In recent years, a liquid crystal element used in a thin and light flat panel display panel can easily control the alignment state of liquid crystal molecules by processing the surface of two substrates constituting the liquid crystal element or by applying an external voltage. Further, it has an excellent characteristic that the effective refractive index can be continuously varied from a value for extraordinary light to a value for ordinary light by applying a voltage.

As described above, the liquid crystal capable of greatly variably controlling the molecular orientation state by applying a low voltage has begun to be applied to various optical elements including a display. As an optical element utilizing the spatial distribution characteristics of the refractive index in a liquid crystal element so far, an alignment process having a strong alignment regulating force such that liquid crystal molecules are aligned in one direction parallel to the substrate is performed, and a circular shape having a diameter of several hundreds of μm is performed. In a liquid crystal device fabricated using an electrode with a hole pattern, the spatial distribution characteristics of the refractive index based on the liquid crystal molecular alignment effect due to an axially symmetric non-uniform electric field are used to obtain the same spatial characteristics as those of a SELFOC lens. A method for obtaining a liquid crystal microlens having a refractive index distribution characteristic has been reported (Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2).
In addition, a liquid crystal lens with an increased effective diameter of the lens has been devised by inserting an insulating medium between the circular hole pattern electrode and the liquid crystal layer (Patent Document 2), and the focal length and lens characteristics are greatly increased by the applied voltage. Therefore, it is expected to be applied to various micro optical devices.

  A liquid crystal microlens that changes the position of a focal point in a plane perpendicular to the optical axis by dividing a pair of opposed circular hole patterns with a diameter of several hundred μm or less by slits and applying different voltages to each electrode part. It has been devised (Patent Document 3).

  Similarly, a circular hole pattern having a diameter of several hundred μm or less is divided by slits, and an alignment film having a very weak alignment regulating force for liquid crystal molecules at the substrate interface is used to change the polarization direction of incident light. A liquid crystal polarization control device capable of rotation control has been reported (Patent Document 4).

  Furthermore, by making the circular hole pattern having a dimension of several hundred μm into an elliptical shape, the refractive index distribution becomes an elliptical shape, and the refractive index distribution and the focal length characteristics are different between the major axis direction and the minor axis direction of the ellipse. It has been reported that an electric field controlled anamorphic liquid crystal lens having large astigmatism can be constructed (Non-patent Document 3).

JP-A-11-109303 JP2004-4616 JP-A-11-109304 JP 2001-272687 A Toshiaki Nose, Susumu Sato (T. Nose and S. Sato), “Liquid-crystal microlens obtained with a nonuniform electric field”, Liquid Crystals, 1989, Vol. 5, P 1425-1433 Susumu Sato, “The World of Liquid Crystals”, Sangyo Tosho Co., Ltd., April 15, 1994, p. 186-189 M. Honma, T. Nose and S. Sato, “Optical properties of anamorphic liquid crystal microlenses and their application to laser diode collimation (Optical properties of anamorphic liquid crystal microlens and their application for laser diode collimation, Japanese Journal of Applied Physics, 1999, Vol. 38, No. 1A, P.89-94

  However, in the liquid crystal microlens structure, there is a problem that in the structure in which the electrode is divided, a disclination line is generated at the boundary between regions where the alignment directions of liquid crystal molecules are different, and the optical characteristics are deteriorated, and the diameter is several hundred μm. However, it was difficult to obtain a lens structure having a relatively large size.

  Furthermore, in an electric field control anamorphic liquid crystal lens using an elliptical hole-shaped pattern electrode, the major axis and minor axis direction of the ellipse and the shape thereof, that is, the ratio of the major axis to the minor axis, are determined. There is a problem that it is difficult to change these parameters.

  The object of the present invention is to solve the above-mentioned problems, with a simple configuration without mechanical moving parts, having an opening with a dimension of several millimeters or more, and suppressing the occurrence of disclination lines, An electric field control analog which has an elliptical refractive index distribution very quickly, and can continuously control the elliptical shape such as rotation of the ellipse in the major axis direction and the ratio of the major axis to the minor axis, and the respective focal lengths. The object is to provide a morphic liquid crystal lens.

  In order to solve the above problems, the present invention is provided with a first substrate having a first electrode, a second substrate, and a circular hole pattern disposed outside the second substrate. A second electrode, and a liquid crystal layer in which liquid crystal molecules accommodated between the first substrate and the second substrate are aligned, and a voltage is applied between the first electrode and the second electrode. In the liquid crystal lens that operates by controlling the orientation of liquid crystal molecules in addition to the above, the second electrode is a hole-shaped divided pattern electrode that is divided into a plurality of portions by slits provided continuously with the hole-shaped pattern portion. Optically based on an elliptical refractive index distribution by forming a potential distribution by applying a voltage that makes the pair of electrodes opposed to each other in the diameter direction of the hole pattern of the electrode divided into a plurality of portions have the same potential. The feature is that variable control of characteristics can be obtained. To provide a field control anamorphic liquid crystal lens.

  In addition, the pair of electrodes opposed to each other in the diameter direction of the hole-shaped divided pattern electrode is applied with a voltage having a different potential to form a potential distribution, whereby the center of the ellipse is refracted from the center axis of the circular hole-shaped opening. 2. An electric field controlled anamorphic liquid crystal lens according to claim 1, wherein variable control of optical characteristics based on the rate distribution can be obtained.

  Further, in the electric field control anamorphic liquid crystal lens, a third electrode is disposed outside the second electrode through an insulating layer, and the first electrode and the second electrode are disposed on the third electrode. An electric field controlled anamorphic liquid crystal lens is provided, wherein a variable voltage can be controlled by applying a second voltage independent of the voltage applied between the first and second voltages.

  By the above means, the optical characteristics such as the major axis direction of the ellipse, the ratio of the major axis to the minor axis, and the focal length of each major axis and minor axis are continuously variably controlled without mechanical action. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1A shown as a cross-sectional view of the embodiment, reference numeral 11 denotes a first substrate (for example, transparent glass having a thickness of 1.3 mm), and a first electrode 21 (as a material is ITO as a material) , Indium, tin, and oxide). A second substrate (for example, a transparent glass having a thickness of 1.3 mm) 12 is disposed on the first electrode 21 side so as to face each other in parallel. A second electrode 22 (a thin aluminum film having a thickness of about 150 nm) is formed on the outside of the second substrate 12. As shown in FIG. 1B, the second electrode 22 has a circular hole pattern 22a (for example, a diameter of 7 mm), and is divided into eight by a 10 μm wide slit.

Between the first substrate 21 side of the first substrate 11 and the second substrate 12, a liquid crystal layer 31 in which liquid crystal molecules are aligned in one direction (the material is E44 manufactured by Merck, for example, a thickness of 130 μm). ) Is formed. 41 and 42 are spacers for keeping the thickness of the liquid crystal layer 31 constant.
On the surfaces of the first and second substrates sandwiching the liquid crystal layer, a polyimide film SE-2170 (not shown) was applied to a thickness of about 150 nm in order to align the liquid crystal in one direction, and stabilized by heat treatment. Later, rubbing is applied in one direction.

  According to such a configuration, the electrodes corresponding to the diameter direction of the circular hole pattern electrode divided into eight parts are respectively paired, for example, A1-A2 in FIG. 1 (B) through the variable resistor from the power source 51 (1 kHz). By applying a voltage Va as a potential and applying different predetermined voltages Vb, Bc, Vd to the other pairs of electrodes B1-B2, C1-C2, D1-D2 to form a potential distribution, liquid crystal molecules The refractive index characteristic distributed in an elliptical shape with the electrode pair having the lowest potential as the major axis direction, that is, an elliptical optical phase distribution can be formed.

  The liquid crystal described in Patent Document 2 is applied by applying a voltage between all the electrodes A1-A2, B1-B2, C1-C2, and D1-D2 divided into eight to the same potential. Lens characteristics and variable focus characteristics similar to the lens can be obtained.

  In FIG. 2, when the voltage is applied so that the first electrode 21 and all of the eight electrodes A1-A2, B1-B2, C1-C2, and D1-D2 have the same potential, The graph shows the relationship between the change in focal length and the voltage when the voltage applied between the electrodes is changed from 40 Vrms to 130 Vrms. By changing the voltage, the focal length is continuously changed.

  FIGS. 3A, 3B, and 3C show light wave phase distributions (interference fringes) when the electric field controlled anamorphic liquid crystal lens of the present invention is viewed from the optical axis direction. When the same voltage 60 Vrms is applied to the electrodes A1-A2, B1-B2, C1-C2, and D1-D2 corresponding to the diameter direction of each of the eight divided circular hole pattern electrodes, FIG. As shown in FIG. 4, the interference pattern becomes a concentric circle, which shows good lens characteristics. Here, each adjacent interference fringe corresponds to a phase difference of 2π, that is, a shift of one wavelength. FIG. 3B shows that the potential Va of the electrode pair A1-A2 is the lowest 20 Vrms, the potential Vc of the electrode pair C1-C2 orthogonal to the electrode pair A1-A2 is the highest 60 Vrms, and the electrode pair B1- The interference patterns are shown when the potentials Vb and Vd of B2 and D1-D2 are set to an intermediate value of 40 Vrms. FIG. 3C similarly shows an interference pattern when voltages of Va = 30 Vrms, Vc = 90 Vrms, and Vb = Vd = 60 Vrms are applied. When a different voltage is applied to each pair of electrodes, an elliptical interference pattern whose major axis is the direction of the electrode pair having the lowest potential is obtained. Further, by varying the potential of each electrode pair, it is possible to vary the density of interference fringes, that is, the phase difference distribution characteristics of light waves.

4A and 4B show the state of the phase delay φ of light in the electric field controlled anamorphic liquid crystal lens in the above embodiment. FIG. 4A shows the phase delay characteristics of light when voltages of Va = 20 Vrms, Vb = 40 Vrms, Vc = 60 Vrms, and Vd = 40 Vrms are applied. FIG. 4B shows the phase delay characteristics of light when voltages of Va = 30 Vrms, Vb = 40 Vrms, Vc = 90 Vrms, and Vd = 60 Vrms are applied. In FIGS. 4A and 4B, the black circles are measured values with respect to the major axis direction of the elliptical refractive index distribution, and the white circles are measured values with respect to the minor axis direction of the elliptical refractive index distribution, and the solid line represents the measured values. A square curve determined to be closest. The phase characteristics of the square distribution are different between the major axis direction and the minor axis direction of the ellipse. In FIG. 4A, the focal lengths in the major axis direction and the minor axis direction are approximately 64 cm and 24 cm, respectively, and in FIG. 4B, they are 47 cm and 20 cm, respectively.
5A, FIG. 5B, FIG. 5C, and FIG. 5D show the ellipsoidal refractive index distribution characteristic in the major axis direction, that is, the electrode pair that has the lowest potential, A1-A2, The interference patterns when B1-B2, C1-C2, and D1-D2 are sequentially changed are shown. It shows that the major axis direction of the ellipse is rotating and the direction can be controlled.

  In the present invention, the example in which the second electrode 22 is divided into eight has been described. However, when the number of divided electrodes is further increased, the control of the ellipse in the major axis direction can be performed with higher definition. Moreover, it is not limited to said structure.

  Furthermore, by providing a potential difference between each pair of electrodes, it is possible to obtain an asymmetric refractive index distribution characteristic in which the center of the ellipse is displaced from the center of the circular hole pattern. In this case, a liquid crystal lens having astigmatism characteristics and deflection characteristics can be configured.

  In addition, a third electrode is disposed outside the second electrode via an insulating layer, and a second voltage independent of the voltage applied to the third electrode between the first electrode and the second electrode is provided. By applying this voltage, the major axis and minor axis direction of the ellipse and the shape of the elliptical refractive index distribution can be constant, and the focal length in the major axis and minor axis direction can be continuously varied over a wide range. .

  The electric field control anamorphic liquid crystal lens of the present invention has various applications such as when the aberration is rotated, such as the shape correction of an elliptical output light beam such as a semiconductor laser, or the aberration correction of an optical system having astigmatism. Is possible.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows one Embodiment of the electric field control anamorphic liquid crystal lens in this invention. Explanatory drawing which shows a mode that the focal distance with respect to an applied voltage changes in order to demonstrate the function of the electric field control anamorphic liquid crystal lens concerning this invention. FIG. 3 is an explanatory diagram showing a state in which the phase of a light wave passing through an electric field control anamorphic liquid crystal lens changes from the optical axis direction in order to explain the function of the electric field control anamorphic liquid crystal lens according to the present invention. FIG. 3 is an explanatory diagram showing an example in which the distribution of phase lag with respect to light waves of the electric field controlled anamorphic liquid crystal lens is changed in order to explain the function of the electric field controlled anamorphic liquid crystal lens according to the present invention. FIG. 3 is an explanatory diagram showing a state in which the phase of a light wave passing through an electric field control anamorphic liquid crystal lens changes from the optical axis direction in order to explain the function of the electric field control anamorphic liquid crystal lens according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... 1st board | substrate, 12 ... 2nd board | substrate, 21 ... 1st electrode, 22 ... 2nd electrode, 22a ... Circular hole, 31 ... Liquid crystal layer, 41 ... spacer, 42 ... spacer, 51 ... power source (1 kHz).

Claims (3)

A first substrate having a first electrode; a second substrate; a second electrode provided with a circular hole-shaped pattern disposed outside the second substrate; and the first substrate A liquid crystal layer in which liquid crystal molecules accommodated between the first electrode and the second substrate are aligned, and a voltage is applied between the first electrode and the second electrode to control the alignment of the liquid crystal molecules. The second electrode is a hole-shaped divided pattern electrode that is divided into a plurality of portions by a slit continuously provided with the hole-shaped pattern portion, and the electrode divided into the plurality of portions By applying a voltage that makes the pair of electrodes facing the diameter direction of the hole pattern the same potential to form a potential distribution, variable control of optical characteristics based on an elliptical refractive index distribution can be obtained. Electric field controlled anamorphic liquid crystal lens Refractive index distribution in which the center of the ellipse is deviated from the center axis of the circular hole-shaped opening by applying a voltage that makes the pair of electrodes opposed to each other in the diameter direction of the hole-shaped divided pattern electrode have different potentials. 2. The electric field control anamorphic liquid crystal lens according to claim 1, wherein variable control of the optical characteristics based on the above is obtained. 3. The electric field controlled anamorphic liquid crystal lens according to claim 1, wherein a third electrode is disposed outside the second electrode through an insulating layer, and the first electrode is disposed on the third electrode. An electric field controlled anamorphic liquid crystal lens characterized in that a variable control of optical characteristics can be obtained by applying a second voltage independent of a voltage applied between the electrode and the second electrode.

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