JP5451986B2 - Liquid crystal lens and vision correction device using the same - Google Patents

Description

  The present invention relates to a lens having a variable focal length and a vision correction device using the same, and more particularly to a liquid crystal lens in which a gradient profile of liquid crystal molecules functions as an optical lens for incident light.

  For devices that are difficult to integrate large optical systems and mechanisms for adjusting such systems, the ability to change the focal length of the lens at high speed using electronic control is required.

  The present invention is applied to the production of lenses and microlenses for optical instruments, and in particular to adaptive optics, optoelectronics, machine vision, stereoscopic displays, and eyeglasses.

  The present invention provides a variable focal length by using a non-uniform surface state between the lens liquid crystal and the alignment layer of the lens, in particular by using a non-uniform spatial distribution of anchoring energy. An alternative approach to liquid crystal lenses is disclosed. The orientation of the liquid crystal molecules is known to depend on the external or magnetic field applied, the elasticity of the liquid crystal, the dielectric properties (when an electric field is applied), the magnetism (when a magnetic field is applied), and the anchoring energy. ing. The gradient profile of the anchoring energy results in a gradient profile of the liquid crystal molecules. As a result, a gradient profile of refractive index with respect to an extraordinary wave passing through the liquid crystal is generated, and this liquid crystal functions as an optical lens. The value of the gradient profile of the liquid crystal molecules is controlled by an external electric field or magnetic field. As a result, the value of the refractive index profile and the focal length of the liquid crystal lens are also controlled. The non-uniform distribution of anchoring energy results in a molecular and refractive index gradient profile even when the external electric or magnetic field is uniform and the liquid crystal layer has a uniform thickness.

  Employing non-uniform anchoring energy to achieve a gradient profile of liquid crystal molecules is novel.

  Non-Patent Document 1 describes the properties of liquid crystal alignment according to profiles, discusses possible alignment states, and derives equations.

  E. Patent Document 1 (2001) entitled “Variable focal lens panel and fabrication the same” by Tajima discloses a variable focal length lens panel and a manufacturing method thereof. In this variable focal length lens panel, a circular transparent electrode is provided on the center of the first substrate. A plurality of annular transparent electrodes are concentrically arranged outside the circular transparent electrode, and the width and interval are shortened toward the outside. The extension electrode extends laterally outward from the center toward the external terminal electrode. An alignment layer is present on these electrodes. A transparent electrode is also provided on the entire surface of the second substrate, and an alignment layer is also provided on the transparent electrode. Here, the first and second alignment layers are subjected to parallel alignment treatment. Although the first substrate and the second substrate are coupled to each other, a predetermined interval is maintained by a gap member disposed outside the annular transparent electrode. A nematic liquid crystal is enclosed in a gap between the first substrate and the second substrate.

  G. Meredith, B.M. Kipppelen, D.M. In US Pat. No. 5,637,028 (2006) entitled “Hybrid electro-active lens” by Mathine, a lens is disclosed that includes at least one electroactive cell to provide a lens with at least two focal lengths. . Here, the focal length of the electroactive cell can be adjusted based on the voltage applied to the electroactive cell. A voltage is supplied by an AC power source including a flying capacitor circuit. Electroactive lenses reduce birefringence by using a single cholesteric liquid crystal electroactive cell.

  H. Ren, Y. et al. -H. Fan, S.M. -T. Patent Document 3 (2005) entitled “Adaptive liquid crystal lenses” by Wu discloses an adaptive optical lens device, a system and method using the same, and includes at least two flat substrates and at least one uniform substrate. A nematic liquid crystal (LC) layer. One of the flat substrates has a spherical or annular ring-shaped Fresnel-type grooved transparent electrode therein. The other flat substrate has a transparent electrode coated on the inside thereof. The thickness of the LC layer is uniform. When a voltage is applied to the LC layer, a centrally symmetric distribution gradient of the refractive index is generated inside the LC layer. Thus, the LC layer focuses the light. The focal length of the lens can be continuously adjusted by controlling the applied voltage.

Y. Sun, S.M. Kowel, G.M. Patent Document 4 (2004) by Nordin discloses a reference plate, a liquid crystal layer arranged to electrically communicate with the reference plate, and a plurality of liquid crystals arranged to electrically communicate with the liquid crystal layer. A liquid crystal adaptive lens is disclosed that includes a closed loop electrode. The closed loop electrode is adapted to receive a variable control voltage, and the refractive index of at least a portion of the liquid crystal layer is adjusted to change the direction of light passing through the liquid crystal layer. By including the closed loop electrode, the liquid crystal layer of the liquid crystal adaptive lens can have a refractive index that changes in the radial direction.
Dwight W.D. Berreman, “Solid Surface Shape and the Alignment of an Adjudicating Nematic Liquid Crystal”, Phys. Rev. Lett. 1972, 28, pp. 1683-1686 US Pat. No. 6,191,881 US Pat. No. 7019890 US Pat. No. 6,859,333 US Pat. No. 6,778,246

  The present invention discloses a liquid crystal lens having a variable focal length and a visual acuity correction apparatus using the same. The gradient profile of the liquid crystal molecules creating a gradient profile of refractive index is achieved by non-uniform anchoring energy and an applied external electric or magnetic field. The focal length of this lens is controlled by an external electric field or magnetic field.

  In the following, non-limiting details of the construction of the electro-optic lens of the present invention are provided. The present invention provides an electro-optic lens filled with a liquid crystal material and controlled by an external electric or magnetic field. A typical liquid crystal cell is shown in FIG. 1, where the liquid crystal material (100) is composed of two substrates (101, 102) having a conductive inner surface (103, 104) and an alignment layer (105, 106). It is sandwiched between. The substrate can be any material that provides the desired light transmission and functions in the apparatus and method disclosed herein, including quartz, glass, and plastic as known in the art. It is done. The conductive material used for the conductive surfaces 103, 104 can be any suitable material, including those specifically disclosed in the present application and other materials known in the art. The conductive material is preferably transparent, and examples thereof include indium oxide, tin oxide, and indium tin oxide (ITO). The thickness of each conductive layer is typically 30 nm to 200 nm. The layer must be thick enough to provide adequate electrical conductivity, but is preferably not thick enough to provide extra thickness for the entire lens structure. The alignment layers 105 and 106 determine the molecular alignment of the liquid crystal material 100 near the surface. The interaction between the molecules of the liquid crystal material 100 and the alignment layer (105 or 106) is characterized by the anchoring energy. The alignment layers 105, 106 can be any material that has anisotropic volume or surface properties and is used to align the molecules of the liquid crystal material 100 near the surface. For example, polyimide having photoinduced anisotropy. The substrates are spaced apart by spacers or other means known in the art. The spacer can be any desired material, such as Mylar, glass, quartz, or other material that can provide the desired spacing.

  The molecules of the liquid crystal material 100 are reoriented under the influence of an applied electric field or magnetic field. Nematic liquid crystals are uniaxial and the optical axis coincides with the molecular axis. When molecules reorient in the presence of a field, the entire index ellipsoid rotates, causing a large change in refractive index.

Liquid crystals can be divided into two groups. If the dielectric tensor is such that the component along the molecular axis (or optical axis) is larger than the component perpendicular to the axis (ε _// > ε _⊥ ), the liquid crystal has positive dielectric anisotropy The molecules tend to be oriented parallel to the applied field. If the dielectric tensor is such that the component along the segmentation axis (or optical axis) is smaller than the component perpendicular to the axis (ε _// <ε _⊥ ), the liquid crystal has negative dielectric anisotropy. The molecules tend to be oriented perpendicular to the applied field. Either type can be used to form a liquid crystal lens. The molecular orientation of the liquid crystal material 100 depends on the value of the external field, anchoring energy, the position of the molecule in the cell, and the elasticity of the liquid crystal material.

であり、Ｍはそれぞれ独立的に、水素原子、アルカリ金属またはＮＨ_４を表す。また、Ｂ^１、Ｂ^２は、

であり、Ｒ^３、Ｒ^４、Ｒ^５は独立的に、水素原子、ハロゲン原子、カルボキシル基、モノまたはジまたはトリハロメチル基、モノまたはジまたはトリハロメトキシ基、シアノ基、アミノ基、または、ヒドロキシル基である。ＳＤ１（ＣＡＳ Ｎｏ．６２３２−４９−１）は、この目的のために非常に適していて、以下の化学構造を有する。

In a known manufacturing method of a liquid crystal lens, an alignment layer having a uniform distribution of anchoring energy is used, and the non-uniform distribution of an external electric field is used. In the novel method of manufacturing a liquid crystal lens disclosed in the present invention, the molecular gradient profile of the liquid crystal material 100 is achieved by a non-uniform distribution of applied electric field or magnetic field and anchoring energy. There are several ways to achieve a non-uniform distribution of anchoring energy. For example, it can be realized by a photo-alignment method using a material having photo-induced anisotropy for the alignment layers 105 and 106. In particular, it is preferable to use a photochemically stable and dichroic anisotropic absorbing material represented by the following general formula (1).
^{B 1 -N = N-A-} N = N-B 2 (1)
Where A is

And each M independently represents a hydrogen atom, an alkali metal or NH ₄ . B ¹ and B ² are

R ³ , R ⁴ , R ⁵ independently represent a hydrogen atom, a halogen atom, a carboxyl group, a mono or di or trihalomethyl group, a mono or di or trihalomethoxy group, a cyano group, an amino group, or a hydroxyl group It is a group. SD1 (CAS No. 6232-49-1) is very suitable for this purpose and has the following chemical structure:

  The anchoring energy of the above-mentioned substances is determined by the amount of irradiation light during photopolymerization. The distribution of the anchoring energy is generated by the distribution of the irradiation light quantity. For example, the distribution of the amount of irradiation light can be realized by a combination of a filter having a distributed transmittance and a light source, or by scanning with a laser beam having a variable intensity.

  Another example is based on the rubbing method. It is well known that by rubbing a surface (eg, the surface of a polyimide), an anisotropy on the surface is formed that can align the molecules of the liquid crystal material. The anchoring energy depends on the rubbing parameters such as the rotational speed of the rubbing roller, the pressure of the rubbing roller against the substrate, and the non-uniform conditions of rubbing that cause a non-uniform distribution of anchoring energy. It is also known that anchoring energy depends on a substance. The alignment layers 105 and 106 can be composed of a mixture of two materials having different anchoring energies. The spatial distribution of anchoring energy results from the spatial distribution of the concentrations of these substances. For example, the concentration distribution can be realized using an ink jet method. A positive liquid crystal lens and a light wave propagating through it are schematically shown in FIG. The molecular gradient profile of the liquid crystal material 100 is formed by a non-uniform spatial distribution of anchoring energy of the alignment layers 105 and 106 and a uniform electric or magnetic field. From one side of the liquid crystal material 100 functioning as an optical lens, an incident or outgoing light wave 201 can have a plane wavefront, while an incident or outgoing light wave 202 can have a spherical wavefront.

  A negative liquid crystal lens and a light wave propagating through it are schematically shown in FIG. The molecular gradient profile of the liquid crystal material 100 is formed by a non-uniform spatial distribution of anchoring energy of the alignment layers 105 and 106 and a uniform electric or magnetic field. From one side of the liquid crystal material 100 functioning as an optical lens, an incident or outgoing light wave 301 can have a plane wavefront, while an incident or outgoing light wave 302 can have a spherical wavefront.

  FIG. 4 shows a calculation result of the spatial distribution of the anchoring energy of the alignment layers 105 and 106 that generates the molecular gradient profile of the liquid crystal material 100 of the positive lens shown in FIG. The value of the gradient profile is controlled by the voltage applied to the conductive surfaces 103, 104, and as a result, the focal length of the liquid crystal lens is controlled.

  FIG. 5 shows a calculation result of the spatial distribution of the anchoring energy of the alignment layers 105 and 106 that generates the molecular gradient profile of the liquid crystal material 100 of the negative lens shown in FIG. The value of the gradient profile is controlled by the voltage applied to the conductive surfaces 103, 140, and as a result, the focal length of the liquid crystal lens is controlled.

The focal length of the liquid crystal lens shown in FIGS. 4 and 5 is obtained using the following equation.
f = πr ² / (ΔΦλ)
Here, f is a focal length, r is a lens radius, ΔΦ is a phase difference between abnormal waves passing through the center and the periphery of the liquid crystal lens, and λ is a wavelength of light.

  FIG. 6 shows the calculation result of the phase profile of the light wave passing through the liquid crystal lens shown in FIG. 2 when the applied voltage is 0.35V. The calculation is performed on a Merck liquid crystal material E7, the thickness of the liquid crystal material 100 is 15 μm and the lens diameter is 1 mm.

  FIG. 7 shows the calculation result of the phase profile of the light wave passing through the liquid crystal lens shown in FIG. 2 when the applied voltage is 0.75V. The calculation is performed on Merck's liquid crystal material E7, where the thickness of the liquid crystal material 100 is 15 μm and the lens diameter is 1 mm.

  FIG. 8 shows the calculation result of the phase profile of the light wave passing through the liquid crystal lens shown in FIG. 2 when the applied voltage is 1V. The calculation is performed on Merck's liquid crystal material E7, where the thickness of the liquid crystal material 100 is 15 μm and the lens diameter is 1 mm.

When the refractive power of the liquid crystal lens changes within the range from the minimum value D _min to the maximum value D _max , D ₀ + D _min to D ₀ + D _max are obtained by matching with another electric field lens or optical system having the refractive power D _0. A new range of One method of creating an electric field lens is to use the liquid crystal lens described above with curved substrates 101 and 102. This electric field lens has a refractive power D ₀ + D _min when the external electric field or magnetic field is zero.

  When one of the substrates 101 and 102 of the liquid crystal lens shown in FIG. 2 or 3 is coated with a material that reflects light, the liquid crystal lens functions as a reflective lens. The refractive index of the reflective lens is twice as large as the refractive power of such a transmissive lens. FIG. 9 schematically shows a positive reflective liquid crystal lens provided with a reflective substrate 101. The light passes through the liquid crystal material 100 twice, thereby increasing the refractive power of the lens by a factor of 2, and the range in which the refractive power changes by an applied external electric or magnetic field is doubled.

An example of a typical liquid crystal cell is shown. An example of a positive liquid crystal lens having non-uniform anchoring energy and applied with a uniform electric field is shown. An example of a negative liquid crystal lens having non-uniform anchoring energy and having a uniform electric field applied thereto is shown. An example of anchoring energy distribution for a positive liquid crystal lens is shown. An example of anchoring energy distribution for a negative liquid crystal lens is shown. The abnormal wave phase distribution when 0.35 V is applied is shown. The abnormal wave phase distribution when 0.7 V is applied is shown. The abnormal wave phase distribution when 1 V is applied is shown. A reflective liquid crystal lens is shown.

Explanation of symbols

100 Liquid crystal substance 101, 102 Substrate 103, 104 Conductive surface 105, 106 Alignment layer 201, 202, 301, 302 Light wave

Claims (6)

An adjustable liquid crystal lens having a variable focal length having at least one liquid crystal layer sandwiched between two substrates,
At least one of the substrates has an alignment layer with a non-uniform spatial distribution of anchoring energy;
One of the substrates of the liquid crystal lens has a reflective internal surface, the liquid crystal lens is a reflective lens ,
An adjustable liquid crystal lens having a variable focal length, wherein the alignment layer is made of at least two different substances, and the spatial distribution of the anchoring energy is achieved by the concentration distribution of the at least two different substances . The adjustable liquid crystal lens with variable focal length according to claim 1, wherein the substrate is flat. The adjustable liquid crystal lens with variable focal length according to claim 1, wherein at least one of the substrates is curved. The adjustable liquid crystal lens with variable focal length according to any one of claims 1 to 3, wherein a uniform external voltage is applied. 4. An adjustable liquid crystal lens with a variable focal length according to any one of claims 1 to 3, wherein a uniform external magnetic field is applied. The adjustable liquid crystal lens with variable focal length according to any one of claims 1 to 3 , wherein an external magnetic field having a non-uniform spatial distribution is applied.

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