JP2012053376A - Polarization element and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization element capable of reducing a loss of retrieved current owing to a resistance of electrode in a longitudinal direction, and to provide a projector.SOLUTION: A polarization element is a wire grid type polarization element 1 that includes a substrate 10 and multiple linear wire grid elements 15 provided on the substrate 10. The wire grid element 15 includes multiple sub-grid elements 15S arranged in a longitudinal direction of the wire grid element 15. The sub-grid element 15S includes: a lower electrode 11 formed on the substrate 10; a semiconductor layer 13 that is formed on the lower electrode and converts light energy into electric energy in reaction to exposure to light; and an upper electrode 12 formed on the semiconductor layer 13. The upper electrode 12 and the lower electrode 11 in the sub-grid element 15S that lie next to each other in a longitudinal direction of the wire grid element 15 are connected electrically.

Description

  The present invention relates to a polarizing element and a projector.

  As polarizing elements used in projectors, polarizing elements described in Non-Patent Documents 1 and 2 are known. This polarizing element is a wire grid type polarizing element, has a polarization separation function, and receives light irradiation to convert light energy into electric energy.

  The polarizing elements of Non-Patent Documents 1 and 2 include a substrate, a plurality of linear wire grid elements provided on the substrate, a first common electrode connected to one end of the plurality of wire grid elements, and a plurality of wires. A second common electrode connected to the other end of the grid element. The wire grid element includes a lower electrode formed on a substrate, a semiconductor layer formed on the lower electrode that receives light irradiation and converts light energy into electric energy, and an upper electrode formed on the semiconductor layer. And. The polarization element transmits a component having a polarization axis perpendicular to the longitudinal direction of the wire grid element (TM polarization component) of incident light and a component having a polarization axis parallel to the longitudinal direction of the wire grid element that does not transmit the polarization element. (TE-polarized component) is converted into electrical energy, and a current is taken out from the common electrode and actively used for power generation.

Kenichiro Hirose, 6 others, “Polarized transmission type photovoltaic film device using wire grid type silicon photodiode”, Document P52, Issue No. IN-10, [online], University of Tokyo “Ultrafine Lithography / Nano Measurement Center” "HP link, [Search August 20, 2009], Internet <URL: http://nanotechnet.tu-tokyo.ac.jp/EB07.pdf> Yoshio Mita and 11 others, “MEMS Integrated Nano and Flexible Electron Devices by Deep Reactive Ion Etching Technology”, [online], link within Shibata / Mita Laboratory HP, University of Tokyo, [Search August 24, 2009], Internet <URL: http://www.if.tu-tokyo.ac.jp/~mita/Papers/GCOE_Symp_Mita2007.pdf>

  However, in the techniques of Non-Patent Documents 1 and 2, since the wire grid element (electrode) is extremely thin and long, the resistance in the longitudinal direction of the electrode is large. Thereby, when an electric current is taken out in the longitudinal direction of the electrode, the electric current taken out may be lost due to the influence of the resistance in the longitudinal direction of the electrode.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polarizing element and a projector capable of suppressing the loss of current taken out due to the influence of the resistance in the longitudinal direction of the electrode. To do.

  In order to solve the above problems, a polarizing device of the present invention is a wire grid type polarizing element, and includes a substrate and a plurality of linear wire grid elements provided on the substrate, The plurality of wire grid elements are arranged with a period shorter than the wavelength of visible light in a direction orthogonal to the longitudinal direction of the wire grid elements, and the wire grid elements are arranged in the longitudinal direction of the wire grid elements. A plurality of subgrid elements, wherein the subgrid element is a lower electrode formed on the substrate, and a semiconductor formed on the lower electrode that receives light irradiation and converts light energy into electric energy And an upper electrode formed on the semiconductor layer, and the upper portion of the subgrid element at a position adjacent to the wire grid element in the longitudinal direction. The pole To the lower electrode, characterized in that it is electrically connected.

  According to this polarizing element, a component (TM polarized component) having a polarization axis orthogonal to the longitudinal direction of the wire grid element in the incident light is transmitted through the polarizing element. On the other hand, a component (TE polarization component) having a polarization axis parallel to the longitudinal direction of the wire grid element that does not pass through the polarization element in the incident light is converted into electric energy by the semiconductor layer. The electric energy converted by the semiconductor layer is taken out as a current through a plurality of subgrids arranged in the longitudinal direction of the wire grid element. Specifically, the electrical energy converted by the semiconductor layer, along the longitudinal direction of the wire grid element, lower electrode, upper electrode, semiconductor layer, lower electrode, upper electrode, semiconductor layer, ..., lower electrode, The electric current is taken out via the upper electrode. Thus, since the electrodes (lower electrode and upper electrode) that are current paths are divided for each subgrid, the resistance in the longitudinal direction of the electrodes does not increase. Therefore, it is possible to provide a polarizing element capable of suppressing the loss of current taken out due to the influence of the resistance in the longitudinal direction of the electrode.

  In the polarizing element, the semiconductor layer may include an n-type semiconductor layer and a p-type semiconductor layer that is stacked on the n-type semiconductor layer.

  According to this polarizing element, when light having an energy larger than the forbidden band (band gap) is incident on a pn junction region where the p-type region and the n-type region are in contact with each other in the semiconductor layer, electrons are emitted from the valence band. Excited. The excited electrons become conduction electrons, and a photovoltaic effect (internal photoelectric effect) is generated that is attracted to the built-in electric field and increases the drift current. Therefore, the TE polarized component that does not transmit through the polarizing element in the incident light can be converted into electric energy.

  In the polarizing element, the semiconductor layer may be configured by sandwiching an intrinsic semiconductor layer between the n-type semiconductor layer and the p-type semiconductor layer.

  According to this polarizing element, since the space charge region (depletion layer) that forms the built-in electric field is increased, the conversion efficiency from light energy to electric energy can be improved. Therefore, the TE-polarized component of the incident light that does not pass through the polarizing element can be smoothly converted into electric energy.

  In the polarizing element, the upper electrode may be formed from one end of the lower electrode to the semiconductor layer.

  According to this polarizing element, the manufacturing process can be simplified as compared with the case where the upper electrode and the lower electrode are electrically connected through, for example, a separate conductor.

  In the polarizing element, the upper electrode constituting one of the two subgrid elements at a position adjacent to the longitudinal direction of the wire grid element, and the semiconductor layer constituting the other subgrid element An insulator layer may be formed between the two.

  According to this polarizing element, the upper electrode formed in one subgrid element of the two subgrid elements adjacent to each other in the longitudinal direction of the wire grid element, and the semiconductor layer formed in the other subgrid element Can be prevented from conducting, and it is possible to suppress the occurrence of problems such as a short circuit occurring and a large current exceeding the design value flowing through the electrode. Therefore, a highly reliable polarizing element can be provided.

  In the polarizing element, the plurality of sub-grid elements may be arranged at a constant period in a longitudinal direction of the wire grid element.

  In the polarizing element, the arrangement period of the sub-grid elements in the longitudinal direction of the wire grid elements may be different between adjacent wire grid elements.

  According to this polarizing element, the light transmitted through the polarizing element can be made uniform as compared with the case where the arrangement periods of the sub-grid elements are the same between adjacent wire grid elements. For example, when the arrangement period of the sub-grid elements in the longitudinal direction of the wire grid elements is the same between adjacent wire grid elements, the interval between the wire grid elements (the interval between two adjacent sub-grid elements) is also adjacent. The matching wire grid elements are periodically arranged at the same pitch. As a result, light is transmitted relatively concentrated from the cuts periodically arranged at the same pitch, and the distribution of light transmitted through the polarizing element becomes non-uniform as a whole. Therefore, by making the arrangement period of the sub-grid elements different between adjacent wire grid elements, it is possible to make the light transmitted through the polarizing element uniform.

  In the polarizing element, a first light absorber that absorbs incident light may be formed between the upper electrodes of the two sub grid elements at positions adjacent to each other in the longitudinal direction of the wire grid element.

  According to this polarizing element, it is possible to suppress incident light from passing between two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. Therefore, it is possible to suppress the leakage of unnecessary light transmitted through the polarizing element (the leakage of visible light).

  In the polarizing element, in the first light absorber, the length in the longitudinal direction of the wire grid element may be longer than the wavelength of visible light.

  When the first light absorber is formed with a length shorter than the wavelength of visible light in the longitudinal direction of the wire grid element, visible light passes between two subgrid elements adjacent to each other in the longitudinal direction of the wire grid element. May be transmitted. In order to suppress the leakage of visible light, it is desirable that the length of the first light absorber is a length that can be recognized as a visible light absorber, that is, a length equal to or greater than that of visible light. If the length of the first light absorber is too short, visible light will be transmitted without recognizing the first light absorber as an absorber. Therefore, when forming a polarizing element for visible light, the length of the first light absorber is preferably longer than the wavelength of visible light.

  In the polarizing element, a second light absorber that absorbs incident light may be formed between the lower electrodes of the two sub grid elements at positions adjacent to each other in the longitudinal direction of the wire grid element.

  According to this polarizing element, it is possible to suppress incident light from passing between two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. Therefore, it is possible to suppress the leakage of unnecessary light transmitted through the polarizing element (the leakage of visible light).

  In the polarizing element, in the second light absorber, the length of the wire grid element in the longitudinal direction may be longer than the wavelength of visible light.

  When the second light absorber is formed with a length shorter than the wavelength of visible light in the longitudinal direction of the wire grid element, visible light passes between two subgrid elements adjacent to each other in the longitudinal direction of the wire grid element. May be transmitted. In order to suppress the leakage of visible light, it is desirable that the length of the second light absorber is a length that can be recognized as a visible light absorber, that is, a length equal to or greater than that of visible light. If the length of the second light absorber is too short, visible light will be transmitted without recognizing the second light absorber as an absorber. Therefore, when forming a polarizing element for visible light, the length of the second light absorber is preferably longer than the wavelength of visible light.

  The projector of the present invention includes an illumination optical system that emits light, a light modulation device that modulates the light, the above-described polarizing element that receives light modulated by the light modulation device, and polarized light that has passed through the polarizing element. A projection optical system for projecting light onto a projection surface.

  According to this projector, since the polarizing element described above is provided, it is possible to provide a projector capable of suppressing the loss of the current taken out due to the influence of the resistance in the longitudinal direction of the electrode.

It is a top view which shows schematic structure of the polarizing element which concerns on 1st Embodiment of this invention. It is sectional drawing along the AA line of FIG. It is a schematic diagram which shows the polarization separation of the light which injects into a polarizing element. It is a figure which shows the preparation processes of a polarizing element. It is a figure which shows the preparation processes of the polarizing element following FIG. It is a figure which shows the preparation processes of the polarizing element following FIG. It is a figure which shows the preparation processes of the polarizing element seen from the direction different from FIG. It is a figure which shows the preparation processes of the polarizing element following FIG. It is a figure which shows the preparation processes of the polarizing element following FIG. It is a top view which shows schematic structure of the polarizing element which concerns on 2nd Embodiment of this invention. It is a top view which shows schematic structure of the polarizing element which concerns on 3rd Embodiment of this invention. It is sectional drawing along the BB line of FIG. It is sectional drawing which shows schematic structure of the polarizing element which concerns on 4th Embodiment of this invention. It is a schematic diagram which shows an example of a projector.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, a number, and the like in each structure are different.

  In the following description, the XYZ rectangular coordinate system shown in FIG. 1 is set, and each member will be described with reference to this XYZ rectangular coordinate system. In the XYZ Cartesian coordinate system, the X axis is set in the longitudinal direction of the wire grid element, the Y axis is set in the direction perpendicular to the longitudinal direction of the wire grid element, and the Z axis is set as the optical axis of light passing through the polarizing element. Has been. The optical axis refers to a virtual light beam that is representative of the light beam transmitted through the polarizing element.

(First embodiment)
FIG. 1 is a plan view showing a schematic configuration of a polarizing element 1 according to the first embodiment of the present invention. In FIG. 1, the code | symbol P1 is a period of a wire grid element.
FIG. 2 is a cross-sectional view taken along line AA in FIG. In FIG. 2, the symbol P2 is the period of the subgrid element.

  The polarizing element 1 is a wire grid type polarizing element, has a polarization separation function, and has a structure that converts light energy into electric energy upon receiving light irradiation. The polarizing element 1 includes a substrate 10, a plurality of linear wire grid elements 15 provided on the substrate 10, and a first terminal connected to one end (end on the −X direction side) of the plurality of wire grid elements 15. A common electrode 21 and a second common electrode 22 connected to the other end (the end on the + X direction side) of the plurality of wire grid elements 15 are provided.

  For the substrate 10, a material having high heat resistance and a light-transmitting property with respect to visible light (for example, light having a wavelength range of 360 nm to 830 nm) is used as a forming material. In the present embodiment, a quartz substrate made of colorless and transparent quartz (quartz) is used as the substrate 10.

  The wire grid element 15 is formed to extend in one direction (X-axis direction) between the first common electrode 21 and the second common electrode 22. The wire grid element 15 is shorter than the wavelength of visible light (for example, the shorter wavelength side of the visible light wavelength: 360 nm) in the direction (Y axis direction) orthogonal to the longitudinal direction (X axis direction) of the wire grid element 15. It arrange | positions with the period P1. The wire grid element 15 is sufficiently longer than the wavelength of visible light in the longitudinal direction. The wire grid element 15 has a linear shape (line shape in plan view) having a predetermined width in a direction orthogonal to the longitudinal direction of the wire grid element 15 when viewed from the direction perpendicular to the plane of the substrate 10 (Z-axis direction). ing. Here, the planar view shape of the wire grid element 15 is shown as a linear shape, but the wire grid element 15 has a rectangular or quadrangular plan view shape having a long length in the longitudinal direction with respect to the width direction (short direction). It can be said that.

  The wire grid element 15 has a plurality of sub-grid elements 15S (see FIG. 2) arranged at a constant period in a direction parallel to the longitudinal direction (X-axis direction) of the wire grid element 15. The arrangement period P2 of the sub-grid elements 15S in the longitudinal direction of the wire grid elements 15 is the same between the adjacent wire grid elements 15. The period P2 is the sum of the length of the lower electrode 11 in the longitudinal direction of the wire grid element 15 and the distance between two adjacent lower electrodes 11.

  The subgrid element 15S includes a lower electrode 11 formed on the substrate 10, a semiconductor layer 13 formed on the lower electrode 11, and an upper electrode 12 formed on the semiconductor layer 13. Yes. For example, the length of the subgrid element 15S in the longitudinal direction is set to about 100 μm.

  The lower electrode 11 is formed on the upper surface of the substrate 10. As a material for forming the lower electrode 11, for example, a non-translucent metal material such as aluminum (Al) can be used. By using Al as the material for forming the lower electrode 11, the reflection characteristics of the polarizing element 1 in the visible region can be enhanced.

  The distance between two adjacent lower electrodes 11 is set to 50 nm or less, for example. Thereby, it can suppress that a part of incident light leaks from the break of the wire grid element 15. On the other hand, when the distance between two adjacent lower electrodes 11 exceeds 50 nm, it is difficult to suppress a part of incident light from leaking from the breaks of the wire grid element 15.

  The semiconductor layer 13 is formed between the lower electrode 11 and the upper electrode 12. The semiconductor layer 13 includes an n-type semiconductor layer 13n and a p-type semiconductor layer 13p that is stacked on the n-type semiconductor layer 13n. The semiconductor layer 13 is arranged in the order of the n-type semiconductor layer 13n and the p-type semiconductor layer 13p from the lower electrode 11 side. As a material for forming the p-type semiconductor layer 13p, for example, p-type amorphous silicon (p-type a-Si) can be used. As a material for forming the n-type semiconductor layer 13n, for example, n-type amorphous silicon (n-type a-Si) can be used.

  Accordingly, when light having energy larger than the forbidden band (band gap) is incident on the pn junction region where the p-type semiconductor layer 13p and the n-type semiconductor layer 13n are in contact with each other in the semiconductor layer 13, electrons are excited from the valence band. Is done. The excited electrons become conduction electrons, and a photovoltaic effect (internal photoelectric effect) is generated that is attracted to the built-in electric field and increases the drift current. Therefore, the light energy of the light incident on the semiconductor layer 13 is converted into electric energy.

  The upper electrode 12 is formed on the upper surface of the semiconductor layer 13 (p-type semiconductor layer 13p). As a material for forming the upper electrode 12, for example, a translucent metal material such as indium tin oxide (ITO) can be used. Thereby, a part of the incident light passes through the upper electrode 12 and is irradiated to the semiconductor layer 13 (p-type semiconductor layer 13p).

  The upper electrode 12 and the lower electrode 11 of the sub grid element 15S at positions adjacent to each other in the longitudinal direction of the wire grid element 15 are electrically connected. Thereby, the electric energy converted by the semiconductor layer 13 is arranged along the longitudinal direction of the wire grid element 15 with the lower electrode 11, the upper electrode 12, the semiconductor layer 13, the lower electrode 11, the upper electrode 12, the semiconductor layer 13,. The current is taken out from the common electrode (the first common electrode 21 or the second common electrode 22) via the lower electrode 11 and the upper electrode 12.

  The current extracted from the common electrode (the first common electrode 21 or the second common electrode 22) is used, for example, for power generation by an air cooling fan that cools the polarizing element 1. Thereby, the high temperature of the polarizing element 1 can be suppressed.

  The upper electrode 12 is formed from one end of the lower electrode 11 over the semiconductor layer 13 (p-type semiconductor layer 13p).

Between the upper electrode 12 which comprises one subgrid element 15S of the two subgrid elements 15S of the position adjacent to the longitudinal direction of the wire grid element 15, and the semiconductor layer 13 which comprises the other subgrid element 15S Insulator layer 14 is formed. As a material for forming the insulator layer 14, for example, an insulating material such as silicon dioxide (SiO ₂ ) can be used. Thereby, the upper electrode 12 which comprises one subgrid element 15S of the two subgrid elements 15S of the position adjacent to the longitudinal direction of the wire grid element 15 and the semiconductor layer 13 which comprises the other subgrid element 15S. Can be prevented from conducting.

  An insulator layer 14 is also formed between the upper electrode 12, the lower electrode 11, and the semiconductor layer 13 of the subgrid element 15 </ b> S in the longitudinal direction of the wire grid element 15. Thereby, it can suppress that the upper electrode 12 which comprises the subgrid element 15S, the lower electrode 11, and the semiconductor layer 13 conduct | electrically_connect.

  FIG. 3 is a schematic diagram illustrating polarization separation of light incident on the polarizing element 1. FIG. 3A shows a case where linearly polarized light TM (Transverse Magnetic) that vibrates in the direction orthogonal to the longitudinal direction of the wire grid element 15 is incident on the polarizing element 1. FIG. 3B shows a case where linearly polarized light TE (Transverse Electric) that vibrates in the longitudinal direction of the wire grid element 15 is incident on the polarizing element 1. In FIG. 3, for the sake of convenience, the configuration of the wire grid 15 (for example, the lower electrode 11, the semiconductor layer 13, and the upper electrode 12) is not shown.

  As shown in FIG. 3A, the incident light G1 to the polarization element 1 has a component s (TM polarization component) having a polarization axis orthogonal to the longitudinal direction (X-axis direction) of each wire grid element 15. ing. When the linearly polarized light TM is incident on the polarizing element 1, only the polarization separation function works for the incident light G1. For this reason, most of the incident light G1 is transmitted through the polarizing element 1.

  As shown in FIG. 3B, the incident light G2 to the polarization element 1 has a component p (TE polarization component) having a polarization axis parallel to the longitudinal direction (X-axis direction) of each wire grid element 15. ing. When the linearly polarized light TE is incident on the polarizing element 1, the polarization separation function functions originally with respect to the incident light G <b> 2 having the polarization axis p, and most of the incident light G <b> 2 is reflected. The energy of the incident light G2 is consumed for conversion into electrical energy by 13. Thereby, the reflected light is reduced. Therefore, the linearly polarized light TE incident on the polarizing element 1 can be selectively absorbed by photoelectric conversion by the semiconductor layer 13.

  4 to 9 are diagrams showing a manufacturing process of the polarizing element. 4 to 6 show a manufacturing process of the polarizing element viewed from the longitudinal direction (X-axis direction) of the wire grid element 15. 7 to 9 show the manufacturing process of the polarizing element viewed from the direction (Y-axis direction) orthogonal to the longitudinal direction of the wire grid element 15.

  First, an Al film 11a is formed on the quartz substrate 10 by a method such as vapor deposition or sputtering (see FIGS. 4A and 7A).

  Next, an n-type a-Si film 13na is formed on the Al film 11a by a method such as plasma CVD. Next, a p-type a-Si film 13pa is formed on the n-type a-Si film 13na by a method such as plasma CVD (see FIGS. 4B and 7B).

  Next, a resist is applied on the p-type a-Si film 13pa by a method such as spin coating, and a resist pattern 31 is formed by a method such as two-beam interference exposure (FIGS. 4C and 7C). reference). The method for forming the resist pattern 31 is not limited to this. For example, transfer such as nanoimprint can be used.

  Next, an etching process such as dry etching or wet etching is performed using the resist pattern 31 as a mask. The p-type a-Si film 13pa and the n-type a-Si film 13na are anisotropically etched until the upper surface of the Al film 11a is exposed. Thereby, an opening 13h is formed in the p-type a-Si film 13pa and the n-type a-Si film 13na. Thereafter, the resist pattern 31 is removed (see FIGS. 4D and 7D).

  Next, a resist is applied on the p-type a-Si film 13pa in which the opening 13h is formed by a method such as spin coating, and a resist pattern 32 is formed by a method such as two-beam interference exposure (FIG. 4E). ) And FIG. 7 (e)).

  Next, using the resist pattern 32 as a mask, an etching process such as dry etching or wet etching is performed. The Al film 11a is anisotropically etched until the upper surface of the quartz substrate 10 is exposed. Thereby, an opening 11h is formed in the Al film 11a. At this time, the size of the opening 11h (the distance between two adjacent Al films 11a) is set to, for example, 50 nm or less. Thereafter, the resist pattern 32 is removed (see FIGS. 5A and 8A).

Next, a SiO ₂ layer 14a is formed in the opening 11h of the Al film 11a, the opening 13h of the p-type a-Si film 13pa and the n-type a-Si film 13na by a method such as plasma CVD (FIG. 5B). And FIG. 8B).

Next, a resist is applied on the SiO ₂ layer 14a by a method such as spin coating, and a resist pattern 33 is formed by a method such as two-beam interference exposure (see FIGS. 5C and 8C).

Next, an etching process such as dry etching or wet etching is performed using the resist pattern 33 as a mask. The SiO ₂ layer 14a is anisotropically etched until the upper surface of the quartz substrate 10 (Al film 11a) is exposed. Thereby, the opening 14h is formed in the SiO ₂ layer 14a. Thereafter, the resist pattern 33 is removed (see FIGS. 5D and 8D).

Then, Al film 11a formed on the quartz substrate 10, to cover the entire exposed portion of the a-Si film 13Na, 13 Pa and the SiO ₂ layer 14a, an ITO film 12a by deposition or sputtering method (See FIG. 5 (e) and FIG. 8 (e)).

  Next, a resist is applied on the ITO film 12a by a method such as spin coating, and a resist pattern 34 is formed by a method such as two-beam interference exposure (see FIGS. 6A and 9A).

Next, an etching process such as dry etching or wet etching is performed using the resist pattern 34 as a mask. The ITO film 12a is anisotropically etched until the upper surface of the SiO ₂ layer 14a (p-type a-Si film 13pa) is exposed. Thereby, the opening 12h is formed in the ITO film 12a. Thereafter, the resist pattern 34 is removed (see FIGS. 6B and 9B).

  Next, a resist is applied on the ITO film 12a in which the opening 12h is formed by a method such as spin coating, and a resist pattern 35 is formed by a method such as two-beam interference exposure (FIGS. 6C and 9). (See (c)).

Next, an etching process such as dry etching or wet etching is performed using the resist pattern 35 as a mask. The ITO film 12a, the SiO ₂ layer 14a, the p-type a-Si film 13pa, the n-type a-Si film 13na, and the Al film 11a are anisotropically etched until the upper surface of the quartz substrate 10 is exposed. Thereafter, the resist pattern 35 is removed (see FIGS. 6D and 9D). Through the above steps, the polarizing element 1 according to the present invention can be manufactured.

  According to the polarizing element 1 of the present embodiment, the component having the polarization axis perpendicular to the longitudinal direction of the wire grid element 15 (TM polarization component) in the incident light is transmitted through the polarizing element 1. On the other hand, a component having a polarization axis parallel to the longitudinal direction of the wire grid element 15 that does not transmit the polarizing element 1 in the incident light (TE polarized component) is converted into electric energy by the semiconductor layer 13. The electrical energy converted by the semiconductor layer 13 is taken out as current from the common electrodes 21 and 22 via the plurality of subgrids 15S arranged in the longitudinal direction of the wire grid element 15. Specifically, the electrical energy converted by the semiconductor layer 13 is arranged along the longitudinal direction of the wire grid element 15 with the lower electrode 11, the upper electrode 12, the semiconductor layer 13, the lower electrode 11, the upper electrode 12, and the semiconductor layer 13. ,... Are taken out as current from the common electrodes 21 and 22 via the lower electrode 11 and the upper electrode 12. Thus, since the electrodes (lower electrode 11 and upper electrode 12) that are current paths are divided for each subgrid 15S, the resistance in the longitudinal direction of the electrodes does not increase. Therefore, it is possible to provide the polarizing element 1 capable of suppressing the loss of the current taken out due to the influence of the resistance in the longitudinal direction of the electrode.

  In addition, according to this configuration, the semiconductor layer 13 includes the n-type semiconductor layer 13n and the p-type semiconductor layer 13p. For this reason, when light having energy larger than the forbidden band (band gap) is incident on the pn junction region where the p-type region and the n-type region are in contact in the semiconductor layer 13, electrons are excited from the valence band. . The excited electrons become conduction electrons, and a photovoltaic effect (internal photoelectric effect) is generated that is attracted to the built-in electric field and increases the drift current. Therefore, the TE polarized component which does not transmit the polarizing element 1 among incident light can be converted into electric energy.

  Further, according to this configuration, the upper electrode 12 is formed from one end of the lower electrode 11 over the semiconductor layer 13 (p-type semiconductor layer 13p). For this reason, compared with the case where the upper electrode 12 and the lower electrode 11 are electrically connected through a separate conductor, for example, the manufacturing process can be simplified.

  Moreover, according to this structure, the upper electrode 12 which comprises one subgrid element 15S of the two subgrid elements 15S of the position adjacent to the longitudinal direction of the wire grid element 15 and the other subgrid element 15S are provided. An insulator layer 14 is formed between the constituent semiconductor layers 13. For this reason, the upper electrode 12 formed on one subgrid element 15S of the two subgrid elements 15S adjacent to the longitudinal direction of the wire grid element 15 and the semiconductor formed on the other subgrid element 15S. It is possible to suppress conduction with the layer 13 and to suppress occurrence of problems such as a short circuit and a large current exceeding the design value flowing in the electrode. Therefore, the highly reliable polarizing element 1 can be provided.

  In the polarizing element 1 of the present embodiment, the semiconductor layer is configured to include an n-type semiconductor layer and a p-type semiconductor layer, but is not limited thereto. For example, the semiconductor layer may be configured with an intrinsic semiconductor layer sandwiched between an n-type semiconductor layer and a p-type semiconductor layer. As a result, the space charge region (depletion layer) that forms the built-in electric field is increased, so that the conversion efficiency from light energy to electrical energy can be improved. Therefore, the TE-polarized component of the incident light that does not pass through the polarizing element can be smoothly converted into electric energy.

(Second Embodiment)
FIG. 10 is a plan view showing a schematic configuration of the polarizing element 2 according to the second embodiment of the present invention, corresponding to FIG. As shown in FIG. 10, the polarizing element 2 according to the present embodiment has the above-described first embodiment in that the arrangement period of the subgrid elements in the longitudinal direction of the wire grid elements is different between adjacent wire grid elements. This is different from the polarizing element 1 according to the above. Since the other points are the same as the above-described configuration, the same elements as those in FIG.

  The polarizing element 2 includes a substrate 10, a plurality of linear wire grid elements 115 provided on the substrate 10, and a first terminal connected to one end (end on the −X direction side) of the plurality of wire grid elements 115. A common electrode 21 and a second common electrode 22 connected to the other end (the end on the + X direction side) of the plurality of wire grid elements 115 are configured.

  The wire grid element 115 has a plurality of sub-grid elements 115 </ b> S arranged in the longitudinal direction (X-axis direction) of the wire grid element 115. The subgrid element 115S includes a lower electrode 111 formed on the substrate 10, a semiconductor layer 113 formed on the lower electrode 111, and an upper electrode 112 formed on the semiconductor layer 113. Yes. The arrangement period of the sub-grid elements 115 </ b> S in the longitudinal direction of the wire grid elements 115 is different between adjacent wire grid elements 115.

  According to the polarizing element 2 of the present embodiment, the light transmitted through the polarizing element 2 can be made uniform as compared with the case where the arrangement periods of the sub-grid elements are the same between adjacent wire grid elements. . For example, when the arrangement period of the sub-grid elements in the longitudinal direction of the wire grid elements is the same between adjacent wire grid elements, the interval between the wire grid elements (the interval between two adjacent sub-grid elements) is also adjacent. The matching wire grid elements are periodically arranged at the same pitch. As a result, light is transmitted relatively concentrated from the cuts periodically arranged at the same pitch, and the distribution of light transmitted through the polarizing element becomes non-uniform as a whole. Therefore, by making the arrangement period of the sub-grid elements 115S different between the adjacent wire grid elements 115, the light transmitted through the polarizing element 2 can be made uniform.

(Third embodiment)
FIG. 11 is a plan view showing a schematic configuration of the polarizing element 3 according to the third embodiment of the present invention, corresponding to FIG. 12 is a cross-sectional view taken along line BB in FIG. As shown in FIGS. 11 and 12, the polarizing element 3 according to this embodiment absorbs light incident between the upper electrodes of two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. It differs from the polarizing element 1 according to the first embodiment described above in that a light absorber is formed. Since the other points are the same as the above-described configuration, the same elements as those in FIGS. In FIG. 12, the symbol L is the length of the first light absorber 41.

  The polarizing element 3 includes a substrate 10, a plurality of linear wire grid elements 215 provided on the substrate 10, and a first terminal connected to one end (end on the −X direction side) of the plurality of wire grid elements 215. A common electrode 21 and a second common electrode 22 connected to the other end (the end on the + X direction side) of the plurality of wire grid elements 215 are provided.

  The wire grid element 215 includes a plurality of sub-grid elements 15S arranged at a constant period in the longitudinal direction (X-axis direction) of the wire grid element 215, and two sub-positions adjacent to each other in the longitudinal direction of the wire grid element 215. A first light absorber 41 disposed between the upper electrodes 12 of the grid element 15S. The subgrid element 15S includes a lower electrode 11 formed on the substrate 10, a semiconductor layer 13 formed on the lower electrode 11, and an upper electrode 12 formed on the semiconductor layer 13. Yes.

  As the first light absorber 41, for example, an intrinsic semiconductor such as germanium (Ge) or silicon (Si), an intrinsic semiconductor that exhibits light absorption characteristics in the visible region, or an insulator that exhibits light absorption properties in the visible region is used as a forming material. . The first light absorber 41 is formed so as to cover at least a gap between two adjacent lower electrodes 11. The first light absorber 41 is formed such that the length of the wire grid element 215 in the longitudinal direction is longer than the wavelength of visible light. For example, the length L of the first light absorber 41 is 500 nm or more.

  According to the polarizing element 3 of the present embodiment, the first light absorber 41 is formed between the upper electrodes 12 of the two subgrid elements 15 </ b> S located adjacent to each other in the longitudinal direction of the wire grid element 215. For this reason, it can suppress that incident light passes between the two subgrid elements 15S of the position adjacent to the longitudinal direction of the wire grid element 215. FIG. Therefore, it is possible to suppress leakage of unnecessary light transmitted through the polarizing element 3 (leakage of visible light).

  Further, according to this configuration, the first light absorber 41 is formed in the longitudinal direction of the wire grid element 215 with a length longer than the wavelength of visible light, so that the position adjacent to the longitudinal direction of the wire grid element 215 It is possible to suppress the passage of visible light between the two subgrid elements 15S. On the other hand, when the first light absorber is formed with a length shorter than the wavelength of visible light in the longitudinal direction of the wire grid element, the gap between two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. Visible light may be transmitted.

(Fourth embodiment)
FIG. 13 is a cross-sectional view showing a schematic configuration of the polarizing element 4 according to the fourth embodiment of the present invention, corresponding to FIG. As shown in FIG. 13, the polarizing element 4 according to the present embodiment is a second light absorber that absorbs light incident between the lower electrodes of two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. Is different from the polarizing element 1 according to the first embodiment described above. Since the other points are the same as the above-described configuration, the same elements as those in FIG.

  The polarizing element 4 includes a substrate 10, a plurality of linear wire grid elements 315 provided on the substrate 10, and a first terminal connected to one end (end on the −X direction side) of the plurality of wire grid elements 315. A common electrode 21 (not shown) and a second common electrode 22 (not shown) connected to the other end (the end on the + X direction side) of the plurality of wire grid elements 315 are configured.

  The wire grid element 315 includes a plurality of sub-grid elements 15S arranged at a constant period in the longitudinal direction (X-axis direction) of the wire grid element 315, and two sub-grids at positions adjacent to the longitudinal direction of the wire grid element 315. A second light absorber 42 disposed between the lower electrodes 11 of the grid element 15S. The subgrid element 15S includes a lower electrode 11 formed on the substrate 10, a semiconductor layer 13 formed on the lower electrode 11, and an upper electrode 12 formed on the semiconductor layer 13. Yes.

  As the second light absorber 42, for example, an intrinsic semiconductor such as germanium (Ge) or silicon (Si), an intrinsic semiconductor that exhibits light absorption characteristics in the visible region, or an insulator that exhibits light absorption properties in the visible region is used as a forming material. . The second light absorber 42 is buried between two adjacent lower electrodes 11. The second light absorber 42 is formed such that the length of the wire grid element 315 in the longitudinal direction is longer than the wavelength of visible light.

  According to the polarizing element 4 of the present embodiment, the second light absorber 42 is formed between the lower electrodes 11 of the two subgrid elements 15S at positions adjacent to each other in the longitudinal direction of the wire grid element 315. For this reason, it can suppress that incident light passes between the two subgrid elements 15S of the position adjacent to the longitudinal direction of the wire grid element 315. FIG. Therefore, it is possible to suppress leakage of unnecessary light transmitted through the polarizing element 4 (leakage of visible light).

  Further, according to this configuration, since the second light absorber 42 is formed in the longitudinal direction of the wire grid element 315 with a length longer than the wavelength of visible light, the position adjacent to the longitudinal direction of the wire grid element 315 It is possible to suppress the passage of visible light between the two subgrid elements 15S. On the other hand, when the second light absorber is formed with a length shorter than the wavelength of visible light in the longitudinal direction of the wire grid element, a gap between two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element is formed. Visible light may pass through.

  In the polarizing element 4 of the present embodiment, the second light absorber is formed between the lower electrodes of the two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element, but is not limited thereto. For example, in the polarizing element in which the second light absorber is formed, the first light absorber may be formed between the upper electrodes of two sub grid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. That is, both the first light absorber and the second light absorber may be formed in the polarizing element. Thereby, it can suppress reliably that incident light passes between the two subgrid elements of the position adjacent to the longitudinal direction of a wire grid element.

(projector)
FIG. 14 is a schematic diagram illustrating an example of a projector including the polarizing element according to the present invention.

  As shown in FIG. 14, the projector 800 includes a light source 810, dichroic mirrors 813 and 814, reflection mirrors 815, 816 and 817, an incident lens 818, a relay lens 819, an exit lens 820, light modulators 822, 823 and 824, a cross. A dichroic prism 825 and a projection lens 826 are provided.

  The light source 810 includes a lamp 811 such as a metal halide and a reflector 812 that reflects the light of the lamp. As the light source 810, besides a metal halide, an ultrahigh pressure mercury lamp, a flash mercury lamp, a high pressure mercury lamp, a deep UV lamp, a xenon lamp, a xenon flash lamp, or the like can be used.

  The dichroic mirror 813 transmits red light contained in white light from the light source 810 and reflects blue light and green light. The transmitted red light is reflected by the reflection mirror 817 and is incident on the light modulation unit 822 for red light. Of the blue light and green light reflected by the dichroic mirror 813, green light is reflected by the dichroic mirror 814 and is incident on the green light light modulation unit 823. The blue light is transmitted through the dichroic mirror 814, and the blue light is transmitted through the relay optical system 821 including the incident lens 818, the relay lens 819, and the emission lens 820 provided to prevent light loss due to a long optical path. Is incident on.

  In the light modulators 822 to 824, an incident side polarization element 840 and an emission side polarization element part 850 are arranged on both sides of the liquid crystal light valve 830. The incident side polarizing element 840 and the exit side polarizing element unit 850 are arranged so that their transmission axes are orthogonal to each other (crossed Nicols arrangement).

  The incident side polarization element 840 is a reflection type polarization element, and reflects light in a vibration direction orthogonal to the transmission axis.

  On the other hand, the exit-side polarizing element unit 850 includes a first polarizing element (pre-polarizing plate, pre-polarizer) 852 and a second polarizing element 854. As the first polarizing element 852, the above-described polarizing element of the present invention having high heat resistance is used. The second polarizing element 854 is a polarizing element using an organic material as a forming material. The exit side polarization element section 850 is an absorption type polarization element that absorbs light in the polarization direction orthogonal to the transmission axis.

  In general, an absorption-type polarizing element formed of an organic material is easily deteriorated by heat, so that it is difficult to use it as a polarizing means for a high-power projector that requires high luminance. However, in the projector 800 of the present invention, the first polarizing element 852 made of an inorganic material having high heat resistance is disposed between the second polarizing element 854 and the liquid crystal light valve 830. Therefore, deterioration of the second polarizing element 854 formed of an organic material can be suppressed. Further, the return light to the liquid crystal light valve 830 can be reduced, and the heat generation of the liquid crystal light valve 830 can be suppressed.

  Further, each first polarizing element 852 converts the light energy of the absorbed light into electric energy, and is used, for example, for power generation by an air cooling fan (not shown) that cools each first polarizing element 852. Therefore, efficient light utilization is possible.

  The three color lights modulated by the respective light modulation units 822 to 824 are incident on the cross dichroic prism 825. The cross dichroic prism 825 is formed by bonding four right-angle prisms. A dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in an X shape at the interface. Yes. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto a screen 827 by a projection lens 826 that is a projection optical system, and an image is enlarged and displayed.

  Since the projector 800 having the above-described configuration includes the above-described polarizing element of the present invention in the exit-side polarizing element unit 850, it is possible to suppress the loss of current taken out due to the influence of the resistance in the longitudinal direction of the electrode. It is possible to provide a projector 800 that can

  The present invention is applicable not only when applied to a front projection type projector that projects from the side that observes the projected image, but also when applied to a rear projection type projector that projects from the side opposite to the side that observes the projected image. can do.

DESCRIPTION OF SYMBOLS 1, 2, 3, 4 ... Polarizing element, 10 ... Board | substrate, 11,111 ... Lower electrode, 12,112 ... Upper electrode, 13,113 ... Semiconductor layer, 13p ... P-type semiconductor layer, 13n ... N-type semiconductor layer, 14, 114 ... insulator layer, 15, 115, 215, 315 ... wire grid element, 15S, 115S ... subgrid element, 21 ... first common electrode, 21 ... second common electrode, 41 ... first light absorber, 42 ... second light absorber, 800 ... projector, 810 ... light source (illumination optical system), 826 ... projection lens (projection optical system), 830 ... liquid crystal light valve, 852 ... first polarizing element (polarizing element), P1 ... Period of wire grid element, P2 ... Period of subgrid element

Claims (12)

A wire grid type polarizing element,
A substrate,
A plurality of linear wire grid elements provided on the substrate,
The plurality of wire grid elements are arranged with a period shorter than the wavelength of visible light in a direction orthogonal to the longitudinal direction of the wire grid elements,
The wire grid element has a plurality of sub-grid elements arranged in the longitudinal direction of the wire grid element,
The subgrid element is
A lower electrode formed on the substrate;
A semiconductor layer formed on the lower electrode, which receives light irradiation and converts light energy into electrical energy;
An upper electrode formed on the semiconductor layer,
The polarizing element, wherein the upper electrode and the lower electrode of the sub grid element at positions adjacent to each other in the longitudinal direction of the wire grid element are electrically connected.   The polarizing element according to claim 1, wherein the semiconductor layer includes an n-type semiconductor layer and a p-type semiconductor layer disposed on the n-type semiconductor layer.   The polarizing element according to claim 2, wherein the semiconductor layer is configured by sandwiching an intrinsic semiconductor layer between the n-type semiconductor layer and the p-type semiconductor layer.   The polarizing element according to claim 1, wherein the upper electrode is formed from one end of the lower electrode to the semiconductor layer.   Between the upper electrode constituting one subgrid element of the two subgrid elements at positions adjacent to each other in the longitudinal direction of the wire grid element and the semiconductor layer constituting the other subgrid element. The polarizing element according to claim 1, wherein an insulating layer is formed.   The polarizing element according to claim 1, wherein the plurality of sub-grid elements are arranged at a constant period in a longitudinal direction of the wire grid element.   The polarizing element according to claim 6, wherein an arrangement period of the sub-grid elements in a longitudinal direction of the wire grid elements is different between adjacent wire grid elements.   2. The first light absorber that absorbs incident light is formed between the upper electrodes of two sub grid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. The polarizing element of any one of -7.   The polarizing element according to claim 8, wherein the first light absorber has a length in a longitudinal direction of the wire grid element longer than a wavelength of visible light.   2. A second light absorber that absorbs incident light is formed between the lower electrodes of two sub grid elements at positions adjacent to each other in the longitudinal direction of the wire grid element. The polarizing element of any one of -9.   The polarizing element according to claim 10, wherein the second light absorber has a length in a longitudinal direction of the wire grid element longer than a wavelength of visible light. An illumination optical system that emits light;
A light modulation device for modulating the light;
The polarizing element according to any one of claims 1 to 11, wherein light modulated by the light modulation device is incident;
A projection optical system that projects polarized light transmitted through the polarizing element onto a projection surface;
A projector comprising:

Images