JP2016139050A - Polarization conversion element and optical apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization conversion element that increases use efficiency of illumination light to a transmissive liquid crystal panel, and an optical apparatus using the element.SOLUTION: The polarization conversion element includes: a polarization separation part to separate incident light into a first polarized beam and a second polarized beam having polarization directions orthogonal to each other; a first polarization direction conversion part to convert the polarization direction of at least the first polarized beam; and a second polarization direction conversion part to convert the polarization direction of at least the second polarized beam; and a polarization direction control part to align the polarization direction of the first polarized beam to the polarization direction of the second polarized beam and to allow an exiting beam to exit with a polarization direction rotated by a predetermined angle with respect to either polarization direction of the first polarized beam and the second polarized beam separated by the polarization separation part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarization conversion element and an optical apparatus using the same.

  For example, a projector, a head-up display (HUD), and the like are known as optical devices that project illumination light onto a transmissive liquid crystal panel and project and display the transmitted light on a screen or the like. FIG. 7 shows an example of an illumination optical system that is currently commonly used in such an apparatus. According to this, the light emitted from a plurality of white light sources 101 such as white LEDs arranged in a line is converted into a parallel light beam or a light beam whose beam diameter is expanded by the corresponding lens 102, and this is changed to the diffusion plate 103. The transmissive liquid crystal panel 104 is irradiated as light having high uniformity without being diffused. The light incident on the transmissive liquid crystal panel 104 by irradiation of illumination light and transmitted therethrough is projected as an image on a screen or the like. However, the transmissive liquid crystal panel 104 transmits only the light of the linearly polarized component in the direction along the transmission axis, and does not transmit the polarized component orthogonal thereto. For this reason, in the case of non-polarized light in which the polarization direction of the illumination light is uniformly distributed in all directions, only about half of the light is transmitted at the maximum. For this reason, the utilization efficiency of illumination light falls and the projected image becomes dark. Note that the double-headed arrow in the figure indicates the direction of polarization.

  Therefore, the light from the light source is separated into two linearly polarized light whose polarization directions are orthogonal to each other, and the polarization direction of one of the linearly polarized light is rotated by 90 ° by an optical rotation element (1/2 wavelength plate), and then the other straight line There has been proposed a method in which polarized light and a single light beam are combined and incident on a liquid crystal panel (see, for example, Patent Document 1). Here, by making the polarization direction of the combined luminous flux parallel to the transmission axis of the liquid crystal display panel, the utilization efficiency of light from the light source can be increased.

JP-A-6-43453

  As described above, a polarization conversion element can be used to separate incident light into two orthogonally polarized lights and align them in one polarization direction by a half-wave plate. An example of an optical system including a polarization conversion element will be described with reference to FIGS. FIG. 8 is a diagram showing a schematic configuration of an example of an illumination optical system of a transmissive liquid crystal panel using a polarization conversion element based on the study by the present inventors. FIG. 9 is a schematic cross-sectional view of the optical system of FIG. 8 viewed from the x direction. The polarization conversion element 105 includes a polarization separation member 108 having a polarization separation film 106 and a reflection film 107 in a transparent substrate, and a half-wave plate 109 selectively disposed on the output surface of the polarization separation member 108. It consists of. The illumination light L101 emitted from the light source 110 becomes a substantially parallel light beam by the lens 102 and enters the polarization separation member 108. In the illumination light incident on the polarization separation member 108, P-polarized light is transmitted through the polarization separation film 106, and S-polarized light is reflected by the polarization separation film 106. The P-polarized illumination light L102 that has passed through the polarization separation film 106 is incident on a half-wave plate 109 that is bonded to the exit surface of the polarization separation member 108. On the other hand, the S-polarized illumination light L103 reflected by the polarization separation film 106 is further reflected by the reflection film 107 in the polarization separation member 108, and the area where the half-wave plate 109 on the exit surface is not disposed. It is emitted from. The P-polarized illumination light L102 incident on the half-wave plate 109 is rotated by 90 ° in the polarization direction so that the polarization direction is aligned with the S-polarized light emitted from the region not transmitting the half-wave plate 109. As a result, the illumination light L102 and L103 whose polarization directions are aligned in one direction can be diffused by the diffusion plate 103 so that the light intensity becomes uniform, and can be applied to the transmissive liquid crystal panel 104.

  By the way, the transmissive liquid crystal panel is employed in various optical devices used outdoors such as an in-vehicle display device such as a HUD. In display devices for automobiles, aircraft cabins, etc., it is necessary not to reduce the visibility even when the user wears polarized sunglasses when used in an environment with strong external light. . The transmission axis of polarized sunglasses is set in the vertical direction in a normal wearing state, and if this transmission axis and the transmission axis of the liquid crystal display panel are orthogonal, the image of the liquid crystal display panel is blocked by the polarized sunglasses, and the image Disappears or disappears. For this reason, the transmission axis of the liquid crystal is often inclined at an angle such as 45 ° or 135 ° with respect to the vertical and horizontal directions of the outer shape of the rectangular panel.

  However, the conventional polarization conversion element as described above does not consider that the transmission axis of the transmission type liquid crystal panel is inclined. For this reason, there is a concern that the polarization direction of the illumination light emitted from the polarization conversion element does not coincide with the direction of the transmission axis of the transmissive liquid crystal panel, and the light use efficiency decreases. The configuration of the optical system according to the prior art disclosed in the cited document 1 also has the same problem because the transmission axis of the liquid crystal display panel coincides with the lateral direction of the rectangular outer shape of the liquid crystal display panel.

  Therefore, in order to make the transmission axis of the transmissive liquid crystal panel coincide with the polarization direction of the emitted illumination light, the entire light source, lens, and polarization conversion element are rotated by 45 ° or 135 ° about the traveling direction of the illumination light. If this is done, the entire apparatus will not fit, and if the entire transmissive liquid crystal panel is to be illuminated, the polarization conversion element will increase in size and a part of the illumination light will be irradiated outside the transmissive liquid crystal panel.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide a polarization conversion element with improved use efficiency of illumination light to a transmissive liquid crystal panel and an optical apparatus using the same.

Means for solving the above problems are as follows. That is,
<1> a polarization separation unit that separates incident light into first polarized light and second polarized light whose polarization directions are orthogonal to each other;
A first polarization direction conversion unit that converts at least the polarization direction of the first polarization; and a second polarization direction conversion unit that converts at least the polarization direction of the second polarization, the first polarization and The polarization direction of the second polarized light is matched, and the polarization direction of the emitted light is set to a predetermined value with respect to any polarization direction of the first polarized light and the second polarized light separated by the polarization separation unit. And a polarization direction control unit that emits light at an angle rotated by an angle.

<2> The polarization direction control member is configured to emit light at an angle obtained by rotating the polarization direction of the emitted light by 45 ° with respect to the polarization direction of any of the first polarization and the second polarization. The polarization conversion element according to <1>.

<3> Only the first polarized light is incident on the first polarization direction conversion unit, and the first polarization is transmitted to the second polarization direction conversion unit through the first polarization conversion unit. And the polarization conversion element according to <1> or <2>, which is configured to make the second polarized light incident.

<4> Only the first polarized light is incident on the first polarization direction converter, and only the second polarized light is incident on the second polarization direction converter < The polarization conversion element according to 1> or <2>.

<5> The first polarization direction conversion unit and the second polarization direction conversion unit are configured by a half-wave plate, and the polarization direction control unit includes the first polarization direction conversion unit and the The polarization conversion element according to <4>, wherein the polarization conversion element is a plate-like member combined with a second polarization direction conversion unit.

<6> A transmissive liquid crystal panel and the polarization conversion element according to any one of <1> to <5>, which receives incident light from a light source and emits the incident light to the transmissive liquid crystal panel.
The polarization conversion element is an optical device that receives light from the light source and emits it as light polarized in the same direction as the transmission axis of the transmissive liquid crystal panel.

  According to the present invention, there are provided a polarization conversion element that can solve the above-mentioned problems and can achieve the above-described object, and has improved the use efficiency of illumination light to a transmissive liquid crystal panel, and an optical device using the same. can do.

FIG. 1 is a perspective view showing a schematic configuration of a polarization conversion element of the present invention according to a first embodiment and an illumination optical system of a transmissive liquid crystal panel using the same. FIG. 2 is a schematic cross-sectional view of the optical system of FIG. 1 viewed from the y direction. FIG. 3 is a schematic cross-sectional view of the optical system of FIG. 1 viewed from the x direction. FIG. 4 is a perspective view showing a schematic configuration of the polarization conversion element of the present invention according to the second embodiment and the illumination optical system of a transmissive liquid crystal panel using the same. FIG. 5 is a schematic cross-sectional view of the optical system of FIG. 4 viewed from the y direction. FIG. 6 is a schematic cross-sectional view of the optical system of FIG. 4 viewed from the x direction. FIG. 7 is a perspective view showing a schematic configuration of an illumination optical system of a transmissive liquid crystal panel in the prior art. FIG. 8 is a diagram showing a schematic configuration of an illumination optical system of a transmissive liquid crystal panel using a polarization conversion element in the prior art. FIG. 9 is a schematic cross-sectional view of the optical system of FIG. 8 viewed from the x direction.

(Polarization conversion element)
As described above, the polarization conversion element of the present invention includes at least a polarization separation unit and a polarization direction control unit, and further includes other components as necessary.

<Polarization separation unit>
The polarization separation unit separates incident light into a first polarization and a second polarization orthogonal to each other. For example, the polarization separation unit includes a prism having a polarization separation film formed therein, and further, if necessary. A reflective film formed in the prism is included. The polarization separation film is, for example, a dielectric multilayer film formed by vapor deposition or the like. As the reflective film, a film in which a metal such as aluminum is deposited can be used.

<Polarization direction control unit>
The polarization direction control unit includes at least a first polarization direction conversion unit and a second polarization direction conversion unit, and further includes other configurations as necessary. Each of the first and second polarization direction conversion units includes, for example, a half-wave plate. The direction of the optical axis of the half-wave plate is the polarization direction of the first polarization or the second polarization separated in the polarization direction so that the polarization direction of the light emitted from the polarization separation unit is aligned and tilted by a predetermined angle. Are inclined at a predetermined angle. The first polarization direction conversion unit and the second polarization direction conversion unit may be configured as a single plate-like member, and further, the polarization conversion element is integrally formed by being combined with the polarization separation unit. A single member can be used.

(Optical equipment)
As described above, the optical apparatus of the present invention includes at least a transmissive liquid crystal panel and the above-described polarization conversion element, and further includes other components as necessary. For example, the optical apparatus can include a light source that emits white light, a lens that uses illumination light from the light source as a parallel light flux, a diffuser plate that uniformizes the illumination light, and the like. Examples of the optical device include an automobile HUD and a projector.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing a schematic configuration of a polarization conversion element of the present invention according to a first embodiment and an illumination optical system of a transmissive liquid crystal panel using the same. The illumination optical system includes a light source unit 11, a polarization conversion element 12, and a diffusion plate 13. 1 and the following FIGS. 2 to 6, each element such as the light source unit 11, the polarization conversion element 12, the diffuser plate 13, and the transmissive liquid crystal panel 14 is held by a holding mechanism (not shown), and the mutual positional relationship is fixed. Has been. The arrows shown in FIG. 1 indicate the direction of polarization. The polarization conversion element 12 tilts the non-polarized illumination light emitted from the light source unit 11 by 45 ° (predetermined angle) with respect to the vertical or horizontal direction of the rectangular outer shape of the transmissive liquid crystal panel 14. Irradiated as illumination light polarized in one direction. The polarization conversion element 12 includes a polarization conversion member 15 and a half-wave plate 16 (second polarization direction conversion unit). The transmissive liquid crystal panel 14 is used, for example, in a vehicle-mounted HUD, and the transmission axis is inclined 45 ° with respect to the lateral direction of the outer shape of the liquid crystal panel.

  The details of the illumination optical system shown in FIG. 1 will be described below with reference to FIGS. FIG. 2 is a schematic cross-sectional view of the optical system of FIG. 1 viewed from the y direction. FIG. 3 is a schematic cross-sectional view of the optical system of FIG. 1 viewed from the x direction. 1 to 3, the direction along the illumination light emitted from the light source unit 11 and directed to the transmissive liquid crystal panel 14 is defined as the z direction, which is two directions orthogonal to the z direction and orthogonal to each other. The direction along the horizontal direction of the outer shape of the liquid crystal panel 14 is defined as the x direction, and the direction along the vertical direction is defined as the y direction.

  The light source unit 11 includes a plurality of light sources 17 such as white LEDs and lenses 18 provided corresponding to the respective light sources 17. Each light source 17 is arranged side by side in one direction corresponding to the horizontally long panel of the transmissive liquid crystal panel 14. The lens 18 converts the diffusing illumination light emitted from the corresponding light source 17 into a substantially parallel light beam. The illumination light L1 emitted from the light source unit 11 by the white LED is in a non-polarized state that vibrates in various directions within the xy plane orthogonal to the traveling direction of the light.

  The polarization conversion member 15 of the polarization conversion element 12 includes a polarization separation unit 19 and a half-wave plate 20 (first polarization conversion unit). Here, the half-wave plate 20 constitutes the polarization direction control unit 21 together with the half-wave plate 16.

  The polarization separation unit 19 is formed of a transparent base material such as glass, and all of them extend long in the x direction. The first prism 22, the second prism 23, the third prism 24, the fourth prism 25, and the first prism 5 prisms 26 are joined.

  The first prism 22 is a triangular prism whose yz section has a substantially right-angled isosceles triangle shape. The first prism 22 has an apex that forms a substantially right angle of the cross section facing the light source 17 direction, and two surfaces sandwiching the substantially right angle are arranged to form about 45 ° with respect to the z direction. Furthermore, the first polarizing beam splitter film 27 and the second polarizing beam splitter film 28 which are polarization separation films are formed on the two surfaces sandwiching the right angle. The polarization separation film is, for example, a dielectric multilayer film formed by vapor deposition or the like. The first polarizing beam splitter film 27 and the second polarizing beam splitter film 28 transmit P-polarized light of incident light and reflect S-polarized light. P-polarized light and S-polarized light are orthogonal to each other. Of the illumination light L1, the illumination light L2 that has passed through the polarizing beam splitter film 28 is referred to as first polarization, and the reflected illumination light L3 is referred to as second polarization.

  The second prism 23 and the third prism 24 have a parallelogram shape in the yz section, and each surface has the first polarizing beam splitter film 27 and the second polarizing beam splitter of the first prism 22, respectively. The surface having the film 28 is joined.

  The fourth prism 25 and the fifth prism 26 are triangular prisms having a yz section having a substantially right-angled isosceles triangle shape, and a first metal in which a metal such as aluminum is vapor-deposited on the inclined surface facing the substantially right-angle. The reflective film 29 and the second reflective film 30 are formed. The fourth prism 25 and the fifth prism 26 have surfaces on which the first reflective film 29 and the second reflective film 30 are formed with respect to the second prism 23 and the third prism 24, respectively. The first beam splitter film 27 and the second beam splitter film 28 are coupled to face each other.

  In this way, the polarization separation unit 19 includes the first beam splitter film 27 and the first reflection film 29 facing each other at an angle of about 45 ° with respect to the z direction and the xy plane, and the second beam. The splitter film 28 and the second reflective film 30 are formed as members. Hereinafter, the surface on the light source unit 11 side of the polarization separation unit 19 is appropriately referred to as an “incident surface”, and the surface on the transmissive liquid crystal panel 14 side is referred to as an “exit surface”.

  The half-wave plate 20 is selectively provided on the exit surface of the polarization separation unit 19. More specifically, the half-wave plate 20 is disposed on the emission surface on the first prism 22 from which P-polarized light is emitted. That is, only P-polarized light out of P-polarized light and S-polarized light is incident on the half-wave plate. In this case, the half-wave plate 20 converts P-polarized light into S-polarized light, and matches the polarization direction with the S-polarized light.

  The half-wave plate 16 is disposed to face the entire emission surface of the polarization separation unit 19 to which the half-wave plate 20 is selectively bonded. The half-wave plate 16 is disposed so that the polarization direction of linearly polarized light is inclined by a predetermined angle by inclining the optical axis in the xy plane. Specifically, S-polarized illumination light whose electric field vibrates in the x direction in FIG. When the illumination light is tilted at an angle rotated by 45 ° with respect to the x direction, which is the polarization direction of S-polarized light, the optical axis of the half-wave plate 20 may be tilted by 22.5 ° with respect to the x direction. .

  The diffusion plate 13 is a plate-like member that diffuses illumination light and emits it as uniform light. For example, the diffusion plate 13 is formed by adding fine particles having light diffusibility to a transparent resin. The transmissive liquid crystal panel 14 is a liquid crystal panel that performs display by receiving illumination from the back. The transmissive liquid crystal panel 14 has a rectangular outer shape. For example, in FIGS. 1 to 3, the x direction is the horizontal direction of the display unit, and the y direction is the vertical direction of the display unit. The transmission axis of the transmissive liquid crystal panel 14 is inclined by about 45 ° with respect to the x direction.

  With the above configuration, as shown in FIG. 3, unpolarized white light emitted from the plurality of light sources 17 becomes illumination light L <b> 1 (incident light) of a parallel light flux by the lens 18, and the polarization of the polarization conversion member 15. The light enters the incident surface of the separation unit 19. Taking the illumination light L1 incident on the second prism 23 side as an example, the illumination light L1 is incident on the first polarization beam splitter film 27 and transmitted through the first polarization beam splitter film 27. The illumination light L2 (first polarization) and the S-polarized illumination light L3 (second polarization) reflected by the first polarization beam splitter film 27 are separated.

  The illumination light L2 passes through the first prism 22, passes through the half-wave plate 20, and is converted to S-polarized light. The illumination light L 3 travels through the second prism 23, is reflected by the first reflective film 29 in the direction of the transmissive liquid crystal panel 14, and is emitted from the polarization separation unit 19. For this reason, the polarization directions of the illumination lights L2 and L3 emitted from the polarization conversion member 15 are aligned to S polarization (that is, linear polarization in which the vibration direction of the electric field is the x direction). Further, the illumination lights L2 and L3 emitted from the polarization conversion member 15 are rotated by 45 ° with respect to the x direction which is the same direction as the transmission axis of the transmissive liquid crystal panel 14 by the half-wave plate 16. The emitted light is emitted. That is, only the illumination light L2 is incident on the half-wave plate 20, and both the illumination light L2 transmitted through the half-wave plate 20 and the illumination light L3 are incident on the half-wave plate 16. Then, the polarization direction is emitted at an angle rotated by 45 ° with respect to the S-polarized light. Further, the illumination lights L2 and L3 are diffused by the diffusion plate 13 to become uniform light, and illuminate the transmissive liquid crystal panel 14.

  In the above description, the illumination light incident on the second prism 23 side from the light source unit 11 has been described. Similarly, the illumination light incident on the third prism 24 side has the same direction as the transmission axis of the transmissive liquid crystal panel 14. The transmissive liquid crystal panel 14 is illuminated with uniform light. Therefore, the transmissive liquid crystal panel 14 is irradiated with uniform light in the same direction as the transmission axis over the entire surface. Thereby, the light efficiently transmitted through the transmissive liquid crystal panel 14 is projected as an image to the user.

  As described above, according to the present embodiment, the polarization separation unit 19 separates the illumination light L1 into the P-polarized illumination light L2 and the S-polarized illumination light L3, and the half-wave plate 20 illuminates the illumination light. The polarization direction of L2 is matched with the polarization direction of the illumination light L3, and the polarization directions of the illumination light L2 and the illumination light L3 are matched with the direction of the transmission axis of the transmissive liquid crystal panel 14 by the half-wave plate 16. Therefore, it is possible to obtain a brighter image with respect to the amount of light output from the same light source 17.

(Example)
Table 1 measures the illuminance of light emitted from the transmissive liquid crystal panel 14 when illumination light from an optical system different from the present invention is used and when the polarization conversion element 12 according to the first embodiment is used. Is a comparison. Comparative Example 1 has a configuration in which no polarization conversion element is disposed between the light source unit 11 and the transmissive liquid crystal panel 14. In Comparative Example 2, only the polarization conversion member 15 is disposed between the light source unit 11 and the transmissive liquid crystal panel 14. The example has a configuration using the polarization conversion element 12 according to the present embodiment. “Efficiency” indicates the illuminance in% when the illuminance according to Comparative Example 1 is 100%. It has been confirmed that the use efficiency of illumination light is greatly improved by using the polarization conversion element 12 according to the present embodiment.

(Second Embodiment)
FIG. 4 is a perspective view showing a schematic configuration of the polarization conversion element of the present invention according to the second embodiment and the illumination optical system of a transmissive liquid crystal panel using the same. In this illumination optical system, the light source unit 11, the diffusion plate 13, and the transmissive liquid crystal panel 14 are the same components as those in the first embodiment. In the present embodiment, the polarization conversion element 41 is configured as a member in which the polarization separation unit 19 and the polarization direction control unit 42 are integrated.

  The details of the illumination optical system of FIG. 4 will be described below with reference to FIGS. 5 and 6. FIG. 5 is a schematic cross-sectional view of the optical system of FIG. 4 viewed from the y direction. FIG. 6 is a schematic cross-sectional view of the optical system of FIG. 4 viewed from the x direction. 4 to 6, the x, y, and z directions indicate the same directions as in the first embodiment. Also, the same or corresponding components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The polarization conversion element 41 of the present embodiment replaces the half-wave plate 16 and the half-wave plate 20 in the polarization conversion element 12 of the first embodiment. A polarization direction control unit 42 including a polarization direction conversion unit) and two half-wave plates 44 (second polarization direction conversion unit). Here, the half-wave plate 43 and the half-wave plate 44 are coupled to each other in the in-plane direction (in the y direction), and the polarization direction control unit 42 is formed as a single plate-like member. Furthermore, the polarization direction control unit 42 is coupled to the exit surface of the polarization separation unit 19 in the normal direction (z direction).

  The half-wave plate 43 is disposed so that the polarization direction of the P-polarized light is tilted by a predetermined angle by tilting the optical axis. Specifically, P-polarized illumination light whose electric field oscillates in the y direction in FIG. 6 is incident on the half-wave plate 43, and this illumination light is aligned with the transmission axis of the transmissive liquid crystal panel 14. The optical axis of the half-wave plate 43 is tilted in the xy plane so that the P-polarized light is rotated by 135 °. The half-wave plate 44 is arranged so that the polarization direction of the S-polarized light is tilted by a predetermined angle by tilting the optical axis. Specifically, S-polarized illumination light whose electric field oscillates in the x direction in FIG. 6 is incident on the half-wave plate 44, and this illumination light is aligned with the transmission axis of the transmissive liquid crystal panel 14. The optical axis of the half-wave plate 43 is inclined with respect to the x direction in the xy plane so that the S-polarized light is rotated by 45 °.

  Other configurations are the same as those of the first embodiment.

  With the configuration described above, as shown in FIG. 6, the white light emitted from the light source 17 becomes parallel light illumination light by the lens 18 and enters the incident surface of the polarization separation unit 19 of the polarization conversion element 41. Taking the illumination light L1 incident from the second prism 23 side as an example, the illumination light L1 enters the first polarization beam splitter film 27 as in the first embodiment, and this first polarization beam. P-polarized illumination light L2 (first polarization) that is transmitted through the splitter film 27 and S-polarized illumination light L3 (second polarization) that is reflected by the first polarization beam splitter film 27 are separated. The illumination light L2 passes through the first prism 22, passes through the half-wave plate 43, and is emitted as linearly polarized light rotated by 45 ° with respect to the x direction. The illumination light L3 travels through the second prism 23, is reflected in the direction of the transmissive liquid crystal panel 14 by the first reflective film 29, passes through the half-wave plate 44, and is rotated by 45 ° with respect to the x direction. Is output as linearly polarized light. Thereby, the illumination lights L2 and L3 emitted from the polarization conversion element 41 are emitted as linearly polarized light whose direction of polarization is the same as the transmission axis of the transmissive liquid crystal panel 14 and rotated by 45 ° with respect to the x direction. The That is, only the illumination light L2 is incident on the half-wave plate 43, and only the illumination light L3 is incident on the half-wave plate 44, and the polarization direction is rotated by 45 ° with respect to the S-polarized light. The light is emitted at an angle. Thereby, the light efficiently transmitted through the transmissive liquid crystal panel 14 is projected as an image to the user.

  As described above, according to the present embodiment, only the first illumination light L 2 that is P-polarized light is incident on the half-wave plate 43 of the polarization direction control unit 42, and the half-wave plate 44. Since only the second illumination light L3, which is S-polarized light, is made incident, and the polarization directions of the emitted illumination light L2 and the illumination light L3 are formed at an angle of 45 ° with respect to the x direction. The same effect as the embodiment can be obtained. In addition, since the polarization direction control unit 42 is integrally formed, as compared with a configuration in which two half-wave plates are arranged to overlap in the traveling direction of the illumination light as in the first embodiment, 1 / There is no decrease in the amount of light due to passing through the two-wavelength plate twice, and the cost can be suppressed by reducing the number of members.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, although a half-wave plate is used as the polarization direction conversion unit, the polarization direction conversion unit is not limited to a half-wave plate as long as the polarization direction is changed. For example, an optical rotator using an optical rotatory material such as a nematic liquid crystal, a wave plate using a polymer material, a wave plate using an optical crystal having birefringence such as quartz can be used.

  Among the polarized lights separated by the polarization separation unit, the P polarized light is the first polarized light and the S polarized light is the second polarized light. The S polarized light is the first polarized light and the P polarized light is the second polarized light. It can also be. Furthermore, the arrangement of the half-wave plate and the rotation angle of the polarization direction can be variously set. For example, in the first embodiment, the half-wave plate 20 is disposed on the emission surface of the first prism 22, but the half-wave plate 20 includes the second prism 23 that emits S-polarized light and The half-wave plate 20 may be disposed on the exit surface of the third prism 24. In this case, the half-wave plate 20 converts the S-polarized light into the P-polarized light so that the polarization direction coincides with the P-polarized light. be able to. The optical axis of the half-wave plate 16 is set so that the polarization direction of P-polarized light coincides with the transmission axis of the transmissive liquid crystal panel 14.

  Furthermore, the shape and arrangement of the prisms of the polarization conversion member and the directions of the polarization beam splitter film and the reflection film shown in the first and second embodiments are examples. For example, the angle formed by the polarization beam splitter film and the reflection film with the incident surface of the polarization conversion member is not limited to 45 °. Furthermore, in the illumination optical system, an optical element such as a further lens for expanding the illumination light beam can be arranged.

  The polarization conversion element and the optical apparatus of the present invention can be suitably used as a polarization conversion element and an optical apparatus that increase the light use efficiency in the transmission type liquid crystal panel of the optical apparatus.

DESCRIPTION OF SYMBOLS 11 Light source part 12 Polarization conversion element 13 Diffusion plate 14 Transmission type liquid crystal panel 15 Polarization conversion member 16 1/2 wavelength plate (2nd polarization direction conversion part)
17 Light source 18 Lens 19 Polarization separator 20 Half-wave plate (first polarization direction converter)
DESCRIPTION OF SYMBOLS 21 Polarization direction control part 22 1st prism 23 2nd prism 24 3rd prism 25 4th prism 26 5th prism 27 1st polarizing beam splitter film | membrane 28 2nd polarizing beam splitter film | membrane 29 1st Reflective film 30 Second reflective film 41 Polarization conversion element 42 Polarization direction control unit 43 1/2 wavelength plate (first polarization direction conversion unit)
44 1/2 wavelength plate (second polarization direction conversion unit)
L1 illumination light L2 illumination light (first polarization)
L3 Illumination light (second polarization)

Claims (6)

A polarization separation unit that separates incident light into first polarized light and second polarized light whose polarization directions are orthogonal to each other;
A first polarization direction conversion unit that converts at least the polarization direction of the first polarization; and a second polarization direction conversion unit that converts at least the polarization direction of the second polarization, the first polarization and The polarization direction of the second polarized light is matched, and the polarization direction of the emitted light is set to a predetermined value with respect to any polarization direction of the first polarized light and the second polarized light separated by the polarization separation unit. A polarization conversion element comprising: a polarization direction control unit that emits light at an angle rotated by an angle.   The polarization direction control member is configured to emit light at an angle obtained by rotating the polarization direction of the emitted light by 45 ° with respect to any polarization direction of the first polarized light and the second polarized light. Item 2. The polarization conversion element according to Item 1.   Only the first polarized light is incident on the first polarization direction converter, the first polarized light transmitted through the first polarization converter is input to the second polarization direction converter, and The polarization conversion element according to claim 1, wherein the polarization conversion element is configured to make the second polarized light incident.   2. The configuration according to claim 1, wherein only the first polarized light is incident on the first polarization direction converter, and only the second polarized light is incident on the second polarization direction converter. 2. The polarization conversion element according to 2.   The first polarization direction conversion unit and the second polarization direction conversion unit are configured by half-wave plates, and the polarization direction control unit includes the first polarization direction conversion unit and the second polarization direction conversion unit. The polarization conversion element according to claim 4, wherein the polarization conversion element is a plate-like member combined with a polarization direction conversion unit. A transmissive liquid crystal panel and the polarization conversion element according to any one of claims 1 to 5, wherein incident light from a light source is received and emitted to the transmissive liquid crystal panel.
The polarization conversion element is an optical device that receives light from the light source and emits it as light polarized in the same direction as the transmission axis of the transmissive liquid crystal panel.

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