JP2013182098A - Optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element which can modulate a uniform phase difference with a simple configuration.SOLUTION: An optical element 100 includes a pair of substrates 103, a deformation material 105 provided between the pair of substrates 103 and arbitrarily changing a distance between the pair of substrates 103, and an optical area 104 surrounded by the pair of substrates 103 and the deformation material 105 and filled with liquid crystal 112.

Description

  The present invention relates to an optical element, and more particularly to a structure for modulating a phase difference.

  Conventionally, various optical elements utilizing the optical anisotropy of liquid crystal have been provided, and a display body, an optical pickup device, and a recording / reproducing device have been provided. For example, in an optical pickup device, a phase difference plate that gives an arbitrary phase difference to an arbitrary region is known in order to improve a reading defect due to reflected light from other than a recording target region (for example, Patent Document 1). reference).

JP 2006-344332 A

  Patent Document 1 discloses an optical element capable of modulating a phase difference by controlling an electric field of a liquid crystal. In the case of phase difference modulation by the electric field control method, the orientation of the liquid crystal inside the optical element is not uniform because it is different in a region close to and far from the electrode. For this reason, the application characteristics (the relationship between the voltage and the phase difference) of the optical element must be obtained in advance for each optical element, resulting in a significant increase in man-hours.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art and provide an optical element capable of modulating a uniform phase difference with a simple structure.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms or application examples. That is, the gist of the present invention is that an optical element capable of modulating the phase difference by a simple method is formed by incorporating a material whose volume is changed by stimulation such as heat, light, and electricity.

  Application Example 1 An optical element according to this application example includes a pair of substrates, a deformable material that is provided between the pair of substrates and changes a distance between the pair of substrates, the pair of substrates, and the deformation An optical region surrounded by a material and filled with liquid crystal.

  According to this application example, the deformable material undergoes a volume change due to stimulation, and the volume between the pair of substrates changes. At this time, the deformation characteristics of the material (relationship between stimulus and volume change) are unique to the material. Once this relationship is obtained, the phase difference can be obtained by Δnd. It is not necessary to obtain the relationship with the voltage, and a uniform phase difference can be modulated with a simple structure. In addition, significant man-hour reduction is realized.

  Application Example 2 An optical element according to this application example is provided between a pair of substrates, a deformation material provided between the pair of substrates, and a distance between the pair of substrates, and the same plane as the deformation material. An elastic material installed and connected to the deformable material; and an optical region surrounded by the pair of substrates and the deformable material and the elastic material and filled with liquid crystal. .

  According to this application example, the deformable material undergoes a volume change due to stimulation, and the volume between the pair of substrates changes. At this time, the deformation characteristics of the material (relationship between stimulus and volume change) are unique to the material. Once this relationship is obtained, the phase difference can be obtained by Δnd. It is not necessary to obtain the relationship with the voltage, and a uniform phase difference can be modulated with a simple structure. In addition, significant man-hour reduction is realized. Furthermore, the deformable material and the elastic material are sandwiched between the pair of substrates, and the elastic material can be deformed in accordance with the deformation of the deformable material. When the manufacturing cost of the deformable material is high, the optical element can be configured with a small amount of the deformable material by replacing a part with an elastic material. In addition, in the case of a deformable material having a large volume, if sufficient deformation characteristics cannot be obtained, small scratches and cracks may be generated and the material may be torn during deformation. By replacing a part of the deformable material with an elastic material having high flexibility, the above-described problem can be avoided.

  Application Example 3 In the optical element according to the application example described above, the deformable material changes in shape and volume by at least one of heat, electricity, and light.

  According to this application example, the deformable material is a material that changes in volume by external stimulation of heat, electricity, and light, and examples thereof include a liquid crystal polymer and an ion exchange resin. By using these deformable materials, the volume of the space between the substrates can be changed without undergoing a mechanical operation such as disassembling and reassembling the substrates.

  Application Example 4 In the optical element according to the application example described above, the elastic material is formed of a stretchable material such as rubber or silicon rubber.

  According to this application example, the manufacturing cost of the optical element can be significantly reduced by combining the deformable material and the inexpensive and easily available elastic material. Further, when sufficient flexibility is not obtained with the deformable material, it is possible to avoid tearing during deformation by replacing a part with a highly flexible elastic material.

  Application Example 5 In the optical element according to the application example described above, the optical element includes a liquid crystal supply unit filled with liquid crystal, and a communication unit that communicates the liquid crystal supply unit with the optical region. According to a change in volume inside the pair of substrates, liquid crystal is supplied to and received from the optical region.

  According to this application example, by providing the liquid crystal supply unit, it is possible to supply and receive liquid crystal according to the volume change between the pair of substrates. Thereby, the amount of liquid crystal can be adjusted in accordance with the volume change between the pair of substrates that occurs according to the movement of the actuator.

  Application Example 6 In the optical element according to the application example, the communication portion is provided in the deformable material.

  According to this application example, the liquid crystal can be freely moved between the liquid crystal supply unit and the pair of substrates by providing the communication part in a part of the deformable material.

  Application Example 7 In the optical element according to the application example described above, the communication portion is provided with a protrusion.

  According to this application example, since the area of the communication portion can be secured by providing the protrusion inside the communication portion, the deformation material is deformed, and the movement of the liquid crystal is stopped by blocking the communication portion. be able to.

  Application Example 8 In the optical element according to the application example described above, the optical element includes a rotation stage that rotates the pair of substrates, the rotation stage includes a transparent region, and fixes the pair of substrates. The substrate is rotated in the same plane.

  According to this application example, since the entire substrate can be freely rotated in the same plane by the rotation stage, the direction of the polarization axis of the incident polarized light can be arbitrarily changed.

  Application Example 9 In the optical element according to the application example described above, the pair of substrates is subjected to surface treatment so that directors in the optical region are oriented in the same direction.

  According to this application example, the liquid crystal directors are aligned in the same direction, so that the liquid crystal is aligned in the same direction, and the phase difference plate that can determine the phase difference given by Δnd only by the film thickness is formed. can do. Here, Δn is the refractive index anisotropy of the liquid crystal, and d is the thickness of the liquid crystal sandwiched between the pair of substrates.

  The above-described configurations can be combined with each other without departing from the spirit of the present invention.

The disassembled perspective view which shows the optical element which concerns on 1st Embodiment. FIG. 2 is a plan view and a cross-sectional view showing the phase difference modulation element according to the first embodiment. FIG. 2 is a plan view and a cross-sectional view showing the phase difference modulation element according to the first embodiment. Sectional drawing which shows operation | movement of the phase difference modulation element which concerns on 1st Embodiment. The top view and sectional drawing which show the phase difference modulation element which concerns on 2nd Embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. Note that the drawings to be used are appropriately enlarged or reduced so that the part to be described can be recognized.

(First embodiment)
A. Configuration of this Embodiment FIG. 1 is an exploded perspective view showing an optical element according to this embodiment. As shown in FIG. 1, the optical element 100 according to the present embodiment includes a phase difference modulation element 101 and a liquid crystal supply unit 102. Among these, the phase difference modulation element 101 includes a pair of substrates 103, an optical region 104 sandwiched between the pair of substrates 103, an artificial muscle portion 105 that is an example of a deformable material that can be deformed by stimulation, a communication portion 106, A connecting portion 107 and a rotary stage 108 are provided. When light travels through a material having an anisotropy in the refractive index, the light traveling speed varies depending on the direction of the vibration surface. The light emitted from the sample has a phase difference corresponding to the passing speed. The polarization state is changed by this phase difference, and modulating the phase difference corresponds to modulating the polarization state. The phase difference modulation element in the present invention is an optical element having a function capable of arbitrarily modulating the polarization state of light.

  The substrate 103 transmits light and can hold the liquid crystal 112 aligned in a desired direction in a thin film shape. The substrate 103 may be made of a transparent material such as glass, quartz, or plastic. However, considering durability, a glass or quartz substrate is desirable. The liquid crystal 112 in the optical region 104 is desirably in a liquid crystal state at room temperature, and a nematic liquid crystal with low viscosity is suitable for high response.

  Artificial muscle is a material or device that converts external stimuli into mechanical force, and is deformed by injecting compressed air into rubber with anisotropic shape, shape memory polymer, shape Examples include a material type using a memory alloy, an ion exchange resin, and a conductive polymer. In particular, the artificial muscle portion 105 in the present embodiment is a material that can convert electrical energy into mechanical energy. Generally, an elastically deformable material sandwiched between a pair of opposing electrodes is an electrode. It is deformed and behaves like a muscle by electrostatic attraction generated between them. Typical examples include silicone resin elastomers and acrylic resin elastomers. It is known that the amount of displacement and the generated force vary with the shape and area of the electrode, but are proportional to the square of the applied voltage. For example, it is known that a deformation pressure of about 0 Pa to 10 MPa is generated in such a material at a voltage in the range of 0 V / m to 440 MV / m. Under these conditions, a line strain of about 50-215% occurs. By using this material, the thickness of the cell into which the liquid crystal 112 is injected can be arbitrarily changed, and the cell can function as the phase difference modulation element 101. As the artificial muscle portion 105, an ion exchange resin in which a sodium salt or a lithium salt is dissolved can be used. An artificial muscle in which a gold electrode is attached to an ion-exchange resin, Nafion 117 ion-exchanged with a sodium salt, shows a displacement of about 10%, and the displacement of the inorganic material zirconate titanate (PZT) is 1. Larger deformation can be expected as compared to less than 6%. There is a shape memory alloy as a material that deforms other than electricity. An alloy of titanium and nickel is generally used, but this changes the shape by changing the temperature. The amount of displacement is about 5%, which is smaller than the above-described ion exchange resin, and the response is low, so it is not suitable for practical use.

  With the structure in which the liquid crystal 112 is filled in the region surrounded by the pair of substrates 103 and the artificial muscle portion 105, the film thickness between the substrates 103 can be arbitrarily changed, and the direction of the polarization axis can be arbitrarily determined by the rotary stage 108. Therefore, polarized light having an arbitrary ellipticity and a polarization axis can be generated. That is, an arbitrary wavelength can be accommodated, and a phase difference plate corresponding to both circularly polarized light and linearly polarized light can be formed.

  By sandwiching and sealing the liquid crystal 112 in the optical region 104 between the pair of substrates 103, the fluid liquid crystal 112 can be fixed in a plate shape.

  When the substrate 103 sandwiching the optical region 104 is previously subjected to an alignment process such as a rubbing process, the liquid crystal 112 can be aligned in a desired direction, and a retardation plate can be formed. The rubbing treatment referred to here is to align the director by subjecting the director, which is the average direction of the major axis of the liquid crystal 112, to rubbing a film of polyimide or the like with cotton.

  FIG. 2 is a plan view and a cross-sectional view showing the phase difference modulation element 101 according to the present embodiment. FIG. 2A is a plan view showing the phase difference modulation element 101. 2B is a cross-sectional view taken along the line II-II ′ of the phase difference modulation element 101 shown in FIG. The artificial muscle portion 105 that separates the pair of substrates 103 is configured to surround the optical region with the same material. However, the communication part 106 is provided in a part of the optical region 104.

  3A and 3B are a plan view and a cross-sectional view showing the phase difference modulation element 101 according to the present embodiment. FIG. 3A is a plan view showing the phase difference modulation element 101. FIG. 3B is a cross-sectional view taken along the line III-III ′ of the phase difference modulation element 101 shown in FIG. In other words, it is a cross-sectional view showing the vicinity of the communication portion 106. A part of the artificial muscle portion 105 is provided with a communication portion 106, and the liquid crystal 112 can freely enter and exit according to the volume change of the space of the optical region 104 filled with the liquid crystal 112 in the phase difference modulation element 101. . With the deformation of the artificial muscle portion 105, the shape of the communication portion 106 also changes. For example, when the artificial muscle portion 105 expands, the area of the communication portion 106 becomes small, and the liquid crystal 112 may not move sufficiently. In such a case, as shown in FIG. 3B, a small protrusion 109 is provided inside the communication portion 106 to suppress the deformation of the artificial muscle portion 105 and ensure a certain opening area. Can do. According to this, since the cross-sectional area of the communication part 106 can be ensured by providing the protrusion 109 inside the communication part 106, the artificial muscle part 105 is deformed and the liquid crystal 112 is moved by blocking the communication part 106. Can be avoided. In FIG. 3A, the protrusion 109 is shown as a cylinder, but the shape is not limited to this shape as long as the communication portion 106 is not blocked even when the artificial muscle portion 105 is expanded most. In addition to this, by installing a rigid ring without contractibility inside the communication portion 106, the minimum area through which the liquid crystal 112 passes through the communication portion 106 is ensured even when the artificial muscle portion is expanded to the maximum. be able to.

  The liquid crystal supply unit 102 is filled with a liquid crystal 112 in a stretchable container, and is connected and sealed with the phase difference modulation element 101 through the connection unit 107. With this configuration, the liquid crystal can freely move between the liquid crystal supply unit 102 and the connecting unit 107, no foreign matter or bubbles are mixed, and the liquid crystal 112 does not leak outside the phase difference modulation element 101. .

  The rotary stage 108 is composed of a plate that is transparent at least in a portion overlapping the operation region of the phase difference modulation element 101.

  By using a transparent plate, light can be transmitted through the liquid crystal 112, and polarization control using the optical anisotropy of the liquid crystal 112 can be performed.

  By moving the rotary stage 108, the alignment direction of the liquid crystal 112 between the pair of substrates 103 can be arbitrarily changed, so that an arbitrary polarization axis can be set.

B. Operation of the present embodiment Next, the operation of the present embodiment will be described.
FIG. 4 is a cross-sectional view showing the operation of the phase difference modulation element 101 according to this embodiment.
As shown in FIG. 4, the film thickness of the liquid crystal 112 in the optical region 104 inside the phase difference modulation element 101 changes due to the expansion and contraction of the artificial muscle portion 105. Thereby, the phase difference defined by Δnd can be changed. Further, by the operation of the rotary stage 108, the alignment direction of the liquid crystal 112 inside the phase difference modulation element 101 and the polarization direction of the incident light beam can be made to form a desired angle. For example, as shown in FIG. 4A, a circularly polarizing plate can be used when Δnd is set to 1 / 4λ, and as a linearly polarizing plate when it is set to 1 / 2λ as shown in FIG. 4B.

  As the volume of the artificial muscle portion 105 increases, the volume of the region sandwiched between the artificial muscle portion 105 and the pair of substrates 103 increases. Along with this, the pressure in this region decreases, and the liquid crystal 112 is injected into the phase difference modulation element 101 from the liquid crystal supply unit 102 via the connecting unit 107.

  As the volume of the artificial muscle portion 105 decreases, the volume of the region sandwiched between the artificial muscle portion 105 and the pair of substrates 103 decreases. Along with this, the pressure in this region increases, and the liquid crystal 112 is injected from the phase difference modulation element 101 into the liquid crystal supply unit 102 via the connecting unit 107.

(Second Embodiment)
FIG. 5 is a plan view and a cross-sectional view showing the phase difference modulation element according to this embodiment. FIG. 5A is a plan view showing the phase difference modulation element 114. FIG. 5B is a cross-sectional view taken along the line VV ′ of the phase difference modulation element 114 shown in FIG. Hereinafter, the structure of the optical element will be described with reference to FIG.

  The phase difference modulation element 114 of the present embodiment is different from the first embodiment in that a structure such as an elastic body part 110 in which the artificial muscle part 105 is partially replaced with an elastic material is formed. Hereinafter, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified here.

  As shown in FIG. 5, the phase difference modulation element 114 according to the present embodiment can form a structure such as an elastic body portion 110 in which the artificial muscle portion 105 is partially replaced with an elastic material. Here, the elastic material is silicon rubber or acrylic rubber, and is usually a material having a deformation characteristic of 5 to 10 times. By using this, there is a possibility that the artificial muscle portion 105 may be torn, but by using an elastic material having more deformation characteristics, it is possible to apply even when there is a larger deformation.

  Thereby, when mass production of the artificial muscle part 105 is difficult, or when manufacturing cost is high, cost can be suppressed by substituting a part with an inexpensive elastic material. In addition, the artificial muscle portion 105 alone does not provide sufficient deformation characteristics, and if a large distortion occurs, the artificial muscle portion 105 may be torn from a small scratch or the like. By connecting to a high elastic material, sufficient deformation characteristics can be obtained while avoiding tearing.

(Third embodiment)
In the phase difference modulation element 101 shown in FIG. 2, the artificial muscle portion 105 is replaced as a deformable material, and an elastic material such as silicon rubber or acrylic rubber is replaced, and the pressure of the liquid crystal supplied from the liquid crystal supply portion 102 shown in FIG. By controlling at, the distance between the pair of substrates 103 and the thickness of the liquid crystal can be changed. With this configuration, further sufficient deformation characteristics can be obtained.

(Fourth embodiment)
In addition to the configuration of the third embodiment, a transparent electrode (not shown) is formed on the pair of substrates 103, and a voltage is applied to the transparent electrode from the outside (not shown) to be applied to the liquid crystal 112. The voltage to be controlled can be controlled. With this configuration, it is possible to realize a phase difference modulation element capable of performing more detailed phase difference control.

  Note that the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof.

  DESCRIPTION OF SYMBOLS 100 ... Optical element 101,114 ... Phase difference modulation element 102 ... Liquid crystal supply part 103 ... Substrate 104 ... Optical area 105 ... Artificial muscle part (deformable material) 106 ... Communication part 107 ... Connection part 108 ... Rotation stage 109 ... Projection part 110 ... elastic body part (elastic material) 112 ... liquid crystal.

Claims (9)

A pair of substrates;
A deformable material provided between the pair of substrates and changing a distance between the pair of substrates;
An optical region surrounded by the pair of substrates and the deformable material and filled with liquid crystal;
An optical element comprising: A pair of substrates;
A deformable material provided between the pair of substrates and changing a distance between the pair of substrates;
An elastic material installed in the same plane as the deformable material and connected to the deformable material;
An optical region surrounded by the pair of substrates, the deformable material, and the elastic material and filled with liquid crystal;
An optical element comprising:   The optical element according to claim 1, wherein the deformable material changes its shape and volume by at least one of heat, electricity, and light.   4. The optical element according to claim 2, wherein the elastic material is made of a stretchable material such as rubber or silicon rubber. A liquid crystal supply unit filled with liquid crystal;
A communication part for communicating the liquid crystal supply part and the optical region;
With
5. The optical element according to claim 1, wherein the liquid crystal supply unit supplies and receives liquid crystal to the optical region in accordance with a change in volume inside the pair of substrates.   The optical element according to claim 5, wherein the communication portion is provided in the deformable material.   The optical element according to claim 6, wherein the communication portion is provided with a protrusion. A rotation stage for rotating the pair of substrates;
The rotating stage comprises a transparent region;
The optical element according to any one of claims 1 to 7, wherein the pair of substrates are fixed, and the pair of substrates are rotated in the same plane.   The optical element according to any one of claims 1 to 8, wherein the pair of substrates is subjected to a surface treatment so that directors of the optical region are oriented in the same direction.

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