JP2011186252A - Polarization converting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization converting element which can be miniaturized and manufactured at low cost. <P>SOLUTION: The polarization converting element includes: a first deflecting part 11 for deflecting incident light in two directions to emit deflected light beams where a first region 11a for deflecting the light in one of the two directions and a second region 11b for deflecting the light in the other direction are alternately formed with a prescribed width; a polarization separating part 12 which emits the light of polarized components orthogonal to each other at different angles; a second deflecting part 14 for emitting light at different incident angles as light at an emission angle in approximately the same direction; and a polarization rotating part 15 where 1/4 retardation parts are formed with the prescribed width at intervals of the same lengths as the prescribed width. The polarization separating part and the second deflecting part are spaced by a prescribed gap, and the first deflecting part, the polarization separating part, the second deflecting part, and the polarization rotating part are all formed on a transparent substrate surface or formed of a film structure formed on the transparent substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polarization conversion element.

  A conventional polarization conversion element will be described based on the elemental technology of the polarization conversion element described below.

  Polarized light is light in which the direction of vibration is uniform with respect to white light in which the vibration direction of light's electric vibration (or magnetic vibration orthogonal to the electric signal) is random.

  A typical polarization control element is a polarization selection element, for example, a polarizing plate. This polarizing plate is an element that extracts a specific polarization component from naturally-polarized light or polarized light, and transmits only one of the two orthogonally polarized components of incident light and shields it by absorbing, reflecting, or scattering the other. Is. In a liquid crystal panel that is widely used at present, an image is displayed by using a polarizing plate. Such a polarizing plate is formed by stretching a polymer film containing iodine or an organic dye in a specific direction, and transmits only linearly polarized light in a certain direction. A film-type polarizing plate having a structure that absorbs polarized light orthogonal to this light has been widely put into practical use (for example, Patent Document 1).

  Another polarization control element is a polarization separation element. The polarization separation element is an element having a function of separating the emission angle of each polarization component by utilizing the difference in reflectance and transmittance between the two polarization components with respect to the incident angle.

  As an example, a prism type polarizer utilizing the birefringence of a crystal is known. A polarizer using birefringence is formed of an optical crystal material, and is usually formed by precisely processing an expensive crystal such as rutile or calcite into a wedge shape or a prism shape. The element formed in this way is extremely expensive, and requires a predetermined size, so that it is difficult to reduce the size, and there is a problem that a usable wavelength region is limited.

  As an element using such a crystal, a polarizing beam splitter using a dielectric multilayer film can be obtained at a low cost although the separation performance is inferior. As such a polarizing beam splitter, one in which a dielectric multilayer film is laminated on a glass prism surface or a substrate surface is known. By setting the film structure and incident angle so that the Brewster angles are at each interface of the film, P-polarized light (polarized light parallel to the incident surface) is transmitted through the multilayer film and S-polarized light (incident on the incident surface). Since the vertical polarized light is reflected, the light can be separated according to the polarization direction.

  Another polarization control element is used as a retardation plate such as a half-wave plate or a quarter-wave plate. The retardation plate is made of a birefringent material, and modulates the polarization state by the difference in refractive index between ordinary light and extraordinary light depending on crystal orientation. A half-wave plate is a half-wave plate in which the optical path difference between the ordinary ray and the extraordinary ray is ½ of the wavelength, and a quarter-wave plate (quarter) is the quarter of the wavelength. -wave plate). Examples of such a material exhibiting birefringence include polymer films widely used in video equipment such as liquid crystal projectors. Such a polymer film is generally formed by stretching a transparent film of polyvinyl alcohol or polycarbonate in a certain direction to form a retardation, and laminating it so as to obtain a retardance (refractive index anisotropy). Is. However, such a resin film is susceptible to ultraviolet rays, and has a problem in reliability such as deterioration in characteristics and transparency due to long-term use. Further, the temperature conditions during use are severe, and when used in a liquid crystal projector or the like, it is necessary to provide a cooling mechanism or the like for air cooling in order to prevent temperature rise in the usage environment. However, when such a cooling mechanism or the like is used, dust or the like adheres to the polarization control element or the optical system, thereby degrading the quality of the displayed image.

  Furthermore, there is an optical rotation element as another example. The optical rotatory element is an element that arbitrarily rotates the polarization plane of linearly polarized light and emits the linearly polarized light as it is. Such a polarization control element is used, for example, for on / off control of pixels in a liquid crystal panel or an organic EL (Electro Luminescence) display. Other applications include optical measurement techniques such as ellipsometry (polarization analysis), laser interferometers, optical shutters, and the like, which are used in various optical instruments or measuring instruments. In particular, the demand for optical rotatory elements is increasing as used in image projection apparatuses such as liquid crystal projectors.

  Many polarization selective elements used in liquid crystal panels and the like obtain absorption dichroism by dyeing, adsorbing, stretching and orienting dichroic materials such as iodine and organic dyes on a substrate film such as polyvinyl alcohol. It is something that can be done.

  By the way, as a method for solving the above-described problems in the half-wave plate, there is a phase modulation element using an inorganic glass material instead of the polymer film. Specifically, a sub-wavelength structure (SWS: Sub) in which two media having different refractive indices (for example, one is air and the other isotropic medium) has a periodic structure shorter than the wavelength of light. Optical elements having a wavelength structure have been widely developed. Patent Documents 2 to 4 and Non-Patent Document 1 describe techniques relating to such a periodic structure shorter than the wavelength of light.

  An optical element having this sub-wavelength structure has characteristics that are largely different from that of a diffractive optical element formed by a structure having a period equal to or greater than the wavelength, and in particular, the period is shorter than the wavelength of light. The diffraction grating is called a subwavelength diffraction grating. Among them, a grating having a period with a shorter period in which only 0th-order diffracted light appears in both transmission and reflection is called a 0th-order grating. Such a zero-order grating has no energy loss caused by high-order diffracted light because there is no high-order diffracted light. Therefore, the optical element has high light utilization efficiency.

  As described above, it is known that the 0th-order diffracted light transmitted through the optical element having the sub-wavelength structure undergoes phase modulation due to the refractive index change caused by the grating structure. For example, an element that controls the wavefront of transmitted light and condenses the transmitted light by modulating the area ratio between the concave and convex portions per unit period (fill factor modulation) has been realized. .

  Similarly, Patent Document 2 discloses a diffractive optical element having a structure in which phase is spatially modulated by performing fill factor modulation of a periodic structure and dividing a region of the structure.

  Patent Document 3 discloses a phase modulation optical element obtained by using a cylindrical sub-wavelength structure and similarly modulating the area occupied by the cylindrical structure per unit area.

  In addition, as the polarization selection element, there is an element using a fine periodic structure such as a wire grid structure. As a polarization control element made of an inorganic material, a wire grid polarizer in which a gold or aluminum fine wire is formed on a transparent substrate has been proposed. Such a polarizer has high mass productivity, can be manufactured at low cost, and has excellent heat resistance. This polarizer has been known as a polarizing element that functions with respect to infrared light having a wavelength of several μm. However, because of recent advances in microfabrication technology, a visible wavelength (400 to 700 nm as shown in Patent Document 5) is known. ) Also discloses a wire grid structure that functions.

  By the way, the polarization conversion element is formed by combining the above-described polarization control elements, and is widely used for improving the light utilization efficiency. Such a polarization conversion element separates a random polarization component emitted from a lamp light source or an LED (Light Emitting Diode) light source into two orthogonal polarization components, and rotates the polarization plane of one linear polarization component by 90 degrees. And has a function of aligning the polarization components in a specific polarization direction. Thereby, it is possible to obtain a light use efficiency of 50% or more with respect to polarized light in a specific direction. Therefore, it is preferable to use it in an optical apparatus using linear polarized light in a specific direction.

  As such an element, as shown in Patent Document 6 or the like, an element that condenses polarized light components that have undergone polarization separation and optical path branching by a lens array, and transmits only a specific polarized light component through the polarization rotating unit to align the polarization direction. And a device using a polarization beam splitter array and a polarization rotation unit as disclosed in Patent Document 7 and the like.

  However, such an element requires a plurality of polarization control elements, and it is difficult to reduce the number of optical elements, so that it becomes expensive and tends to increase in size.

  That is, in the case of the element described in Patent Document 6 or the like, it is a converging / diffusing optical system using a lens or the like, and since the optical path length becomes long, the structure of the entire element becomes large, and the element is downsized. It is difficult. Further, since the alignment of the lens optical system is complicated, there is a problem that the manufacturing cost of the element becomes high. In addition, in the case of what is described in Patent Document 7 and the like, it is mainly composed of a cube prism array. However, since the prism itself is expensive and it is necessary to perform an adhesion process for arraying, the manufacturing cost is low. Becomes very expensive. In addition, since the prism array needs a certain size, there is a limit to downsizing, and since it is bonded by an adhesive, it is easily affected by the external environment, and the performance over time is reduced. Degradation is also likely to occur.

  Therefore, in view of the above-described conventional technology, an object of the present invention is to provide a polarization conversion element that can be miniaturized and can be manufactured at low cost.

  The present invention deflects and emits incident light in two directions, and a first region that deflects in one of the two directions and a second region that deflects in the other direction. The first deflecting unit alternately formed with a predetermined width, the polarization separating unit that emits the light of the polarization components orthogonal to each other at different angles, and the light with different incident angles in substantially the same direction A second deflection unit that emits light having an emission angle; and a polarization rotation unit in which the ¼ phase difference unit is formed with the predetermined width and the same length as the predetermined width. The polarization separation unit and the second deflection unit are arranged at a predetermined gap interval, and the optical axis direction of the light incident on the first deflection unit, the one direction, and the other direction are all A direction in the same plane, the other direction being through the optical axis, The first deflection unit, the polarization separation unit, the second deflection unit, and the polarization rotation unit are all formed on a transparent substrate surface, respectively. Alternatively, it is characterized by being formed by a film structure formed on a transparent substrate.

  Further, the present invention includes a first substrate and a second substrate that transmit light, and emits light by deflecting incident light in two directions on one surface of the first substrate. Of the two directions, a first region deflected in one direction and a second region deflected in the other direction are alternately arranged with a predetermined width, respectively. And a polarization separation unit that emits light of polarization components orthogonal to each other at different angles, and is formed on the other surface of the first substrate. A second deflecting portion that emits light having different incident angles as light having an emission angle in substantially the same direction is formed on one surface, and ¼ is formed on the other surface of the second substrate. A polarization rotator is formed in which the phase difference portion is formed with the predetermined width and the same length as the predetermined width. In other words, the other surface of the first substrate and the one surface of the second substrate are arranged to face each other with a predetermined gap interval, and the optical axis direction of the light incident on the first deflection unit The one direction and the other direction are all in the same plane, and the other direction is opposite to the one direction through the optical axis. To do.

  Further, the present invention is characterized in that an angle formed between the optical axis and the one direction is equal to an angle formed between the optical axis and the other direction.

  Further, according to the present invention, the gap C is defined as C = W / (2 when W is the predetermined width and θ is an angle between the optical axis and the one direction or the other direction. X tan θ).

  In the invention, it is preferable that the polarization separation unit is configured to straighten light of one polarization component among the polarization components orthogonal to each other and deflect light of the other polarization component.

  In the invention, it is preferable that a diffraction grating having a period shorter than or equal to the wavelength of the incident light is formed in the polarization separation unit.

  In the invention, it is preferable that the polarization separation unit emits 0th-order diffracted light and 1st-order diffracted light of the light incident on the polarization separation unit.

  In the present invention, the first region and the second region of the first deflecting section are each formed with a refracting surface having an inclination with respect to the substrate surface.

  In the invention, it is preferable that a diffraction grating for deflecting the incident light in different directions is formed in the first region and the second region of the first deflection unit. And

  In the invention, it is preferable that a diffraction grating having a period longer than the wavelength of the incident light is formed in the second deflecting unit.

  Further, according to the present invention, the light of one polarization component out of the light of the polarization components orthogonal to each other emitted from the second deflection unit is incident on the ¼ phase difference unit, and the light of the other polarization component The polarization rotation part is installed so that the light enters the region where the ¼ phase difference part is not formed.

  Further, the present invention is characterized in that a polarization selection unit is provided that allows light emitted from the polarization rotation unit to enter and emit only light having a predetermined polarization direction.

  In the invention, it is preferable that the polarization selection unit is formed of a thin metal wire structure having a period shorter than the wavelength of the incident light.

  ADVANTAGE OF THE INVENTION According to this invention, the polarization conversion element which can be reduced in size and can be manufactured at low cost can be provided.

Structure diagram of polarization conversion element in first embodiment Explanatory drawing of the polarization conversion element in 1st Embodiment Explanatory drawing of the 1st deflection | deviation part Structure diagram of first deflecting portion formed in prism area Structure diagram of first deflecting portion formed in diffraction grating region Structure diagram of polarization separation unit Illustration of polarization separation unit Structure diagram of second deflecting unit Explanatory drawing of the 2nd deflection | deviation part Structure of polarization rotation unit Explanatory drawing when the quarter phase difference part in the polarization rotation part is formed with a diffraction grating Explanatory drawing of the positional relationship of a 1st deflection | deviation part and a polarization | polarized-light rotation part. Explanation of polarization rotation unit Structure diagram of polarization conversion element in second embodiment Structure diagram of polarization conversion element in third embodiment Structural diagram of another polarization conversion element in the third embodiment

  Embodiments of the present invention will be described.

[First Embodiment]
The first embodiment is a polarization conversion element that emits incident light in a random polarization direction emitted from a light source as outgoing light of linear polarization in a predetermined direction.

  The polarization conversion element in this Embodiment is demonstrated based on FIG. The polarization conversion element in the present embodiment includes a first deflection unit 11, a polarization separation unit 12, a second deflection unit 14, and a polarization rotation unit 15, and the polarization separation unit 12 and the second deflection unit 14. Between the two, a gap region 13 is provided. FIG. 2 shows the state of light in the polarization conversion element in the present embodiment. The incident light 21 incident on the polarization conversion element is light in which S-polarized light and P-polarized light are mixed, or light having a random polarization direction emitted by a light source or the like.

  As shown in FIG. 3, the first deflecting unit 11 includes a plurality of first regions 11a and second regions 11b formed on a transparent substrate such as glass, for example. Each width in the second region 11b is formed to be W. The light 21a incident on the first region 11a is emitted as light 22a in a direction inclined at an angle θ to the left in the drawing with respect to the optical axis of the incident light 21. The light 21b incident on the second region 11b is emitted as light 22b in a direction inclined at an angle θ on the right side of the optical axis of the incident light 21 in the drawing. Therefore, the incident light 21 in the first deflecting unit 11 includes the light 22a and the light in directions inclined in different directions across the optical axis of the incident light 21 in the first region 11a and the second region 11b. It is emitted as 22b. The angle θ of the emitted light 22a and the light 22b with respect to the optical axis of the incident light 21 is preferably in the range of 20 ° to 70 °, and is formed to be 45 ° as shown in FIG. May be. In the present embodiment, a case is described in which the inclination angle of the light 22a emitted from the first region 11a and the inclination angle of the light 22b emitted from the second region 11b are the same angle θ. However, as long as the emitted light 22a and 22b are in opposite directions across the optical axis, the angles may be different from each other. The value of W is preferably about 10 μm to 100 μm.

  As such a 1st deflection | deviation part 11, as shown in FIG. 4, for example, the 1st area | region 11a and the 2nd area | region 11b have several prism area | regions 31a and 31b cut off by the mutually different inclination. What was formed is mentioned. Further, as shown in FIG. 5, the first region 11a and the second region 11b are formed by diffraction grating regions 41a and 41b, and the optical axis of the incident light 21 is formed by the diffraction grating regions 41a and 41b. The light 22a and the light 22b may be emitted in directions inclined in different directions from each other. Note that the diffraction grating regions 41a and 41b are shown in FIG. 5 as triangular diffraction gratings, but the diffraction grating regions 41a and 41b are not limited to triangular shapes, but have rectangular widths. It may be a digital blaze shape that modulates the like.

Such a 1st deflection | deviation part 11 is directly formed in a glass substrate, or is formed on a glass substrate. Specifically, the first deflection unit 11 may be formed by processing a glass substrate, or a film such as TiO ₂ is formed on the glass substrate, and the TiO ₂ or the like is formed. The diffraction grating regions 41a and 41b as shown in FIG. 5 may be formed by processing this film.

  In this way, the light 21 incident on the first deflecting unit 11 is emitted as light 22a emitted from the first region 11a and light 22b emitted from the second region 11b. The light 22a and the light 22b thus emitted are emitted in directions inclined in different directions with the optical axis of the incident light 21 interposed therebetween.

  Next, the polarization separation unit 12 will be described. The polarization separation unit 12 has a function of emitting 0th-order light and first-order diffracted light with respect to light incident on the polarization separation unit 12. For example, as shown in FIG. 6, the polarization separation unit 12 has a diffraction grating having a period A substantially equal to the wavelength λ of the incident light 21 on the surface of the glass substrate. is there. In this polarization splitting section 12, the diffraction grating is formed in a predetermined shape so that the S-polarized component is emitted in the direction inclined by 2θ as the primary light. Of the light incident on the polarization separator 12, the P-polarized component travels straight as it is as the 0th-order light, and the S-polarized component exits in the direction inclined by 2θ as the primary light.

  The polarization separation unit 12 will be described in more detail with reference to FIG. 7. The light 22a emitted from the first region 11a of the first deflection unit 11 is incident on the polarization separation unit 12 and travels straight as it is. The light is emitted as S-polarized light 23a which becomes light and P-polarized light 23b which is diffracted and becomes primary light. In addition, the light 22b emitted from the second region 11b of the first deflecting unit 11 enters the polarization separating unit 12, and is directly diffracted as S-polarized light 23c, which becomes zero-order light, and diffracted primary light. The P-polarized light 23d is emitted. Here, the P-polarized light 23b, which is the primary light, is diffracted and emitted with an angle of 2θ, and thus is emitted in the same direction as the S-polarized light 23c, which is the 0th-order light. Further, the P-polarized light 23d, which is the primary light, is diffracted and emitted with an angle of 2θ, and thus is emitted in the same direction as the S-polarized light 23a, which is the zero-order light.

  Next, the second deflection unit 14 will be described. The second deflecting unit 14 is a second deflecting plate formed of a glass substrate or the like, and makes the light 23a, 23b, 23c, 23d emitted from the polarization separating unit 12 incident thereon, thereby allowing the optical axis of the incident light 21 to enter. And has a function of emitting light in a direction substantially parallel to.

For example, as shown in FIG. 8, the second deflecting unit 14 is a second deflecting unit 14 in which a diffraction grating having a period B longer than the wavelength of the incident light 21 is formed on a glass substrate. The light incident at θ with respect to the direction perpendicular to the deflection plate can be emitted as light in the vertical direction to the second deflection plate. For this reason, the period B of the diffraction grating formed in the 2nd deflection | deviation part 14 is formed so that the formula shown to following (1) may be satisfy | filled. It should be noted that the height of the formed grating and the like are formed so that the transmission efficiency is high.

B × sin θ = λ (1)

Further, as shown in FIG. 9, the second deflecting unit 14 is installed at a position separated by a predetermined distance C from the polarization separating unit 12 and substantially in parallel with the polarization separating unit 12. Thereby, a region between the polarization separation unit 12 and the second deflection unit 14, that is, a region separated by the distance C becomes the gap region 13. As a result, the S-polarized light 23a and the S-polarized light 23c can be incident on the second deflecting unit 14 at substantially the same position or adjacent positions. The S-polarized light 23a and the S-polarized light 23c thus incident are combined, and the second deflecting unit 14 forms S-polarized light 24a in a direction substantially parallel to the optical axis of the incident light 21. The two deflecting units 14 can emit light in a substantially vertical direction. Similarly, the P-polarized light 23b and the P-polarized light 23d can be incident on the second deflecting unit 14 at substantially the same position or close positions. The P-polarized light 23b and the P-polarized light 23d incident in this way are combined to form a P-polarized light 24b from the second deflecting unit 14 in a direction substantially parallel to the optical axis of the incident light 21. The two deflecting units 14 can emit light in a substantially vertical direction.

The distance C in the gap region 13 is such that the S-polarized light 23a and the S-polarized light 23c are incident on substantially the same position in the second deflecting unit 14, and further, the P-polarized light 23b and the P-polarized light 23c It is preferably set so that the light 23d is incident at substantially the same position, and specifically, it is preferable to satisfy the equation (2).

C = W / (2 × tan θ) (2)

In the second deflecting unit 14, the incident positions of the S-polarized light 23a and the S-polarized light 23c and the incident positions of the P-polarized light 23b and the P-polarized light 23d are close to each other. Since the same effect can be obtained, the range of the value of C may have a predetermined width centered on the value obtained by the equation (2) described above. In the above description, the gap region 13 is a space. However, the gap region 13 may be formed of a dielectric substrate having a predetermined thickness formed of a transparent material.

  Next, the S-polarized light 24 a and the P-polarized light 24 b are incident on the polarization rotating unit 15. The polarization rotator 15 is formed by a third region 15a that transmits light without changing the polarization direction and a fourth region 15b that emits light while changing the polarization direction. For example, as shown in FIG. 10, in the fourth region 15b on the glass substrate 51, a ¼ phase difference portion 52 made of a ¼ wavelength plate or the like is formed, and the third region 15a is ¼th. The phase difference portion 52 is not formed. The quarter phase difference portion 52 is formed so that the width is W and the interval is W. That is, the third region 15a and the fourth region 15b are formed so that each width is W. The quarter phase difference portion 52 may form a normal quarter phase difference portion made of a dye-containing polymer or the like, or may be formed by a sub-wavelength structure, a phase modulation structure, an optical rotatory element, or the like. is there. From the viewpoint of miniaturization and transmission efficiency, it is preferable to form with a sub-wavelength structure, a phase modulation structure, an optical rotation element, or the like. For this reason, the quarter phase difference portion 52 formed in the polarization rotation portion 15 is preferably formed by a diffraction grating having a periodic structure having a wavelength λ or less of the incident light 21 as shown in FIG.

  Also, as shown in FIG. 12, the polarization rotation unit 15 includes the first region 11 a and the second region of the first deflection unit 11 in the direction in which the quarter phase difference unit 52 is parallel to the incident light 21. Of the boundary portions with the region 11 b, one boundary portion 53 is installed so as to be positioned at the approximate center of the ¼ phase difference portion 52. Therefore, the other boundary portion 54 is disposed so as to be located at the approximate center of the region between the quarter phase difference portions 52. As a result, as shown in FIG. 13, the S-polarized light 24a incident on the polarization rotation unit 15 is emitted as it is as the S-polarized light 25a, and the P-polarized light 24b incident on the polarization rotation unit 15 is polarized. The s-polarized light 25 b is emitted through the ¼ phase difference portion 52 in the portion 15. Accordingly, all of the light 25 (25a, 25b) emitted from the polarization rotating unit 15 is S-polarized light.

  In this manner, the polarization conversion element in the present embodiment can emit light in which P-polarized light and S-polarized light are mixed and light having a random polarization direction as light having a predetermined polarization direction.

  In the present embodiment, among the incident light 21, P-polarized light can be converted into S-polarized light and emitted as the emitted light 25, so that the light utilization efficiency is 50% or more with respect to the incident light. Obtainable.

  In addition, each of the first deflection unit 11, the polarization separation unit 12, the second deflection unit 14, and the polarization rotation unit 15 processes the surface of a transparent substrate such as glass, or glass on a transparent substrate such as glass. Can be obtained by forming a film having a different refractive index from the above and processing the film. That is, the first deflection unit 11, the polarization separation unit 12, the second deflection unit 14, and the polarization rotation unit 15 for forming the polarization conversion element in the present embodiment are the first deflection plate, the polarization separation plate, It is formed by the second deflecting plate and the polarization rotating plate, does not include a large member such as a prism, and does not require an adhesion process at the time of manufacture, and does not require optical alignment or the like. . Therefore, the polarization conversion element in this embodiment can be easily downsized and can be manufactured at low cost.

  In the above description, the case where the emitted light 25 is emitted as S-polarized light has been described. However, polarized light that emits P-polarized light by changing the position where the polarization rotating unit 15 is installed. It can be set as a conversion element. Specifically, by arranging the position of the region where the quarter phase difference portion 52 is formed in the polarization rotation unit 15 to be opposite to the case where the S-polarized light is emitted, Light can be emitted.

  In the description of the present embodiment described above, the first deflecting unit 11, the polarization separating unit 12, the second deflecting unit 14, and the polarization rotating unit 15 are replaced with the first deflecting plate, the polarizing separating plate, and the second Although the description has been given of the one formed by the deflection plate and the polarization rotation plate, the first deflection unit 11, the polarization separation unit 12, the second deflection unit 14, and the polarization rotation unit 15 can be formed by a film structure. . For example, a predetermined diffraction grating is formed by a film structure for each of the first deflection unit 11 and the polarization separation unit 12 on the substrate, and similarly, each of the second deflection unit 14 and the polarization rotation unit 15 is also formed. A structure in which a predetermined diffraction grating is formed by a film structure may be used.

  In addition, the gap region 13 is formed of a transparent glass substrate, the polarization separation unit 12 and the first deflection unit 11 are stacked on one surface of the glass substrate with a film structure, and the second surface is formed on the other surface. The deflection unit 14 and the polarization rotation unit 15 may be formed by a film structure.

[Second Embodiment]
Next, a second embodiment will be described. The present embodiment is a polarization conversion element having a configuration different from that of the first embodiment.

  Based on FIG. 14, the polarization conversion element in this Embodiment is demonstrated. The polarization conversion element in the present embodiment is formed by a first substrate 61 and a second substrate which are transparent substrates made of glass or the like.

  On one surface of the first substrate 61, a first deflection region 71 for deflecting incident light is formed. The first deflection region 71 includes a first region 71a and a second region 71b that are processed into a shape such as a diffraction grating or a prism so that emitted light is in different directions. The first region 71a and the second region 71b are formed so that the width becomes W alternately. The first deflection region 71 has a function as the first deflection unit 11 in the first embodiment. In addition, a polarization separation region 72 in which a diffraction grating having a period of about the wavelength λ of the incident light 21 is formed on the other surface of the first substrate 61. The polarization separation region 72 has a function as the polarization separation unit 12 in the first embodiment.

  A second deflection region 74 in which a diffraction grating having a period longer than the wavelength λ of the incident light 21 is formed on one surface of the second substrate 62. The second deflection region 74 has a function as the second deflection unit 14 in the first embodiment. A polarization rotation region 75 is formed on the other surface of the second substrate 62. The polarization rotation region 75 is formed so that the quarter phase difference portion 75a having a width W is W and the interval between the quarter phase difference portions 75a is W. The polarization rotation region 75 has a function as the polarization rotation region 15 in the first embodiment.

  The first substrate 61 and the second substrate 62 are arranged so that the other surface of the first substrate 61 and one surface of the second substrate face each other. A gap region 73 is formed between the two substrates 62. The gap region 73 is the same as the gap region 13 in the first embodiment.

  In the present embodiment, the incident light 21 enters from one surface of the first substrate 61, exits from the other surface of the first substrate 61, and further enters one surface of the second substrate 62. Then, the light is emitted as emitted light 25 from the other surface of the second substrate 62. Therefore, the incident light 21 is emitted as outgoing light 25 through the first deflection region 71, the polarization separation region 72, the gap region 73, the second deflection region 74, and the polarization rotation region 75.

  In this embodiment, since the polarization conversion element is formed using two glass substrates or the like, it can be manufactured at a lower cost and can be further downsized.

[Third Embodiment]
Next, a third embodiment will be described. The polarization conversion element in the present embodiment has a structure in which a polarization selection unit 80 is provided in the polarization conversion element in the first embodiment and the second embodiment.

  For example, as shown in FIG. 15, the polarization conversion element in the present embodiment includes a first deflection unit 11, a polarization separation unit 12, and a second deflection unit that constitute the polarization conversion element in the first embodiment. 14, the polarization rotation unit 15 is further provided with a polarization selection unit 80. A gap region 13 having a predetermined interval is provided between the polarization separation unit 12 and the second deflection unit 14. In such a polarization conversion element, the incident light 21 can be incident from the first deflection unit 11 and can be emitted from the polarization selection unit 80 as the outgoing light 26.

  In addition, as shown in FIG. 16, the polarization conversion element in the present embodiment includes a second substrate 62 and a second substrate 62 constituting the polarization conversion element in the second embodiment. In this structure, the polarization selector 80 is provided on the surface of the substrate 62 where the polarization rotation region 75 is formed. A gap region 73 having a predetermined interval is provided between the first substrate 61 and the second substrate 62. In such a polarization conversion element, the incident light 21 can be made incident from the first substrate 61 and emitted as the emitted light 26 from the polarization selection unit 80.

  The polarization selector 80 is a polarizer that transmits polarized light in a predetermined direction, and is preferably a wire grid polarizer having a metal thin wire structure. Moreover, when the incident light 21 is light in the visible region (wavelength: 0.4 μm to 0.7 μm), the metal material forming the metal thin wire structure is preferably aluminum (Al).

  By disposing such a polarization selector 80 at the final stage, a specific polarization component can be obtained with a higher extinction ratio.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

11 First deflection unit 11a First region 11b Second region 12 Polarization separation unit 13 Gap region 14 Second deflection unit 15 Polarization rotation unit 15a Third region 15b Fourth region 21 Incident light 25 Emission light 31a Prism region 31b Prism region 41a Diffraction grating region 41b Diffraction grating region 51 Glass substrate 52 1/4 phase difference portion 61 First substrate 62 Second substrate 71 First deflection region 72 Polarization separation region 73 Gap region 74 Second Deflection area 75 Polarization rotation area 80 Polarization selector

JP 2002-122733 A JP 2001-318217 A JP 2004-61905 A Japanese Patent Laying-Open No. 2005-10377 Special table 2003-502708 gazette JP 2000-171754 A JP 2005-128241 A

“Rigorous concept for the design of diffractive microlenses with high numerical apertures” Journal of the Optical Society of America A, Vol 14 (4), pp901-906 (1997))

Claims (13)

The incident light is deflected in two directions and emitted, and a first region deflected in one of the two directions and a second region deflected in the other direction are respectively First deflecting portions alternately formed with a predetermined width;
A polarization separation unit that emits light of polarization components orthogonal to each other at different angles;
A second deflection unit that emits light having different incident angles as light having an emission angle in substantially the same direction;
A polarization rotator in which a ¼ phase difference portion is formed at an interval of the predetermined width and the same length as the predetermined width;
Have
The polarization separation unit and the second deflection unit are arranged at a predetermined gap interval,
The optical axis direction of the light incident on the first deflecting unit, the one direction, and the other direction are all in the same plane, and the other direction passes through the optical axis, The direction is opposite to the direction,
The first deflection unit, the polarization separation unit, the second deflection unit, and the polarization rotation unit are all formed on a transparent substrate surface, or a film structure formed on a transparent substrate. The polarization conversion element characterized by being formed by. A first substrate that transmits light and a second substrate;
One surface of the first substrate deflects incident light in two directions and emits light, and includes a first region deflected in one of the two directions The first deflection section is formed in which the second regions deflected in the other direction are alternately arranged with a predetermined width, respectively.
On the other surface of the first substrate, there is formed a polarization separation unit that emits light of polarization components orthogonal to each other at different angles,
On one surface of the second substrate, a second deflecting unit that emits light having different incident angles as light having an emission angle in substantially the same direction is formed.
On the other surface of the second substrate, there is formed a polarization rotation portion in which a quarter phase difference portion is formed with the predetermined width and the same length as the predetermined width,
The other surface of the first substrate and the one surface of the second substrate are arranged to face each other with a predetermined gap interval,
The optical axis direction of the light incident on the first deflecting unit, the one direction, and the other direction are all in the same plane, and the other direction passes through the optical axis, A polarization conversion element having a direction opposite to the direction.   3. The polarization conversion element according to claim 1, wherein an angle formed between the optical axis and the one direction is equal to an angle formed between the optical axis and the other direction. When the gap C is the angle between W as the predetermined width and θ as the optical axis and the one direction or the other direction,
C = W / (2 × tan θ)
The polarization conversion element according to claim 3, wherein:   5. The polarization separation unit according to any one of claims 1 to 4, wherein the polarization separation unit is configured to straighten light of one polarization component among the polarization components orthogonal to each other and deflect light of the other polarization component. A polarization conversion element according to any one of the above.   6. The polarization conversion element according to claim 1, wherein a diffraction grating having a period shorter than or equal to the wavelength of the incident light is formed in the polarization separation unit.   The polarization conversion element according to claim 1, wherein the polarization separation unit emits zero-order diffracted light and first-order diffracted light of light incident on the polarization separation unit.   The refracting surface which inclines with respect to the said substrate surface is each formed in the said 1st area | region and the said 2nd area | region in a said 1st deflection | deviation part, The any one of Claim 1 to 7 characterized by the above-mentioned. A polarization conversion element according to any one of the above.   The diffraction grating for deflecting the incident light in different directions is formed in the first region and the second region of the first deflecting unit, respectively. The polarization conversion element according to any one of 7.   10. The polarization conversion element according to claim 1, wherein a diffraction grating having a period longer than a wavelength of the incident light is formed in the second deflecting unit. 11.   Of the polarized light components orthogonal to each other emitted from the second deflecting unit, one polarized component light is incident on the ¼ phase difference unit, and the other polarized light component is incident on the ¼ position. 11. The polarization conversion element according to claim 1, wherein the polarization rotation unit is installed so as to be incident on a region where no phase difference part is formed.   The polarization conversion element according to any one of claims 1 to 11, further comprising a polarization selection unit that allows light emitted from the polarization rotation unit to enter and emit only light having a predetermined polarization direction.   The polarization conversion element according to claim 12, wherein the polarization selection unit is formed of a thin metal wire structure having a period shorter than a wavelength of the incident light.

Images