JP2010181717A - Polarizing illumination optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing illumination optical element which can suitably convert light made incident with an inclination into linear polarized light. <P>SOLUTION: The polarizing illumination optical element comprises a polarizing beam splitter array 10. The polarizing beam splitter array 10 is provided with: a first prism set 14 obtained by combining rectangular prisms 20, 21; and a second prism set 15 composed in a similar way. The prism sets 14, 15 are arranged by rectangularly crossing the slants of the rectangular prisms 20, 21, and the slants of the rectangular prisms 22, 23. The space between the rectangular prisms 20, 21 is provided with a polarizing separation film 16 transmitting P polarized light and reflecting S polarized light. The space between the rectangular prisms 22, 23 is also provided with a polarizing separation film 17 in a similar way. The space between the respective prism sets 14, 15 is provided with an angle selection film 18 transmitting light made incident at a narrow incidence angle and reflecting light made incident at a wide incidence angle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarization illumination optical element that converts non-polarized incident light into linearly polarized light having a certain polarization direction.

  Various liquid crystal projectors that illuminate an image displayed on a liquid crystal display panel with light from a light source lamp and project the image onto a screen have been commercialized. As is well known, a liquid crystal display panel includes a liquid crystal layer having a predetermined thickness in which liquid crystal molecules are encapsulated, and a polarizer and an analyzer disposed on the incident surface side and the output surface side, respectively. The polarizer and the analyzer are arranged so that their polarization directions are orthogonal or parallel to each other, and control the passage of linearly polarized light incident on the liquid crystal layer according to the orientation of the liquid crystal molecules, and pass through the analyzer. The light amount of the linearly polarized light to be emitted is adjusted.

  On the other hand, in a light source device of a liquid crystal projector, a polarization illumination optical element that converts non-polarized light from a light source into linearly polarized light having the same polarization direction as that of a polarizer of a liquid crystal display panel is usually used. As such a polarization illumination optical element, as known from Patent Document 1, a prism array in which a polarization beam splitter and a λ / 2 phase difference plate are combined is frequently used. The polarization beam splitter includes a polarization separation surface that transmits one of two types of linearly polarized light whose polarization directions are orthogonal to each other and reflects the other, and any one of the two types of linearly polarized light separated by the polarization separation surface. After rotating the polarization direction by 90 degrees through the λ / 2 phase difference plate, it is combined with the other linearly polarized light to obtain linearly polarized light having the same polarization direction.

JP 2000-194068 A

  In a light source device of a liquid crystal projector, illumination light irradiated from a light source is converted into a parallel light beam by a lens array and then incident on a polarization illumination optical element. However, even if the illumination light is converted into a parallel light beam by the lens array, not all of the illumination light is parallel to the optical axis, and some light rays are incident on the polarization illumination optical element with an inclination of about 5 degrees. . The illumination light incident on the polarization illumination optical element with such an inclination is reflected inside the polarization illumination optical element and returns to the light source side, does not enter the polarization separation surface, and two types of polarization directions are orthogonal to each other. In some cases, linearly polarized light is emitted from the polarized illumination optical element in a mixed state, which has been a factor of reducing the conversion efficiency of the polarized illumination optical element into linearly polarized light.

  The present invention has been made in view of the above problems, and in a polarized illumination optical element used in a light source device of a liquid crystal projector, illumination light incident with an inclination can be appropriately converted into linearly polarized light. For the purpose.

  In order to achieve the above object, the polarized illumination optical element of the present invention includes a first prism set formed into a quadrangular prism shape by combining a pair of right-angle prisms, and is configured substantially the same as the first prism set, and has a side surface. A second prism set disposed adjacent to the first prism set so as to be aligned, and the pair of right-angle prisms of the first prism set, and one of P-polarized light or S-polarized linearly polarized light A polarization separation film that is transmitted and emitted from the first prism set, and the other is reflected and incident on the second prism set, and is emitted in the same direction as the linearly polarized light emitted from the first prism set As described above, the optical path changing means for changing the optical path of the linearly polarized light incident on the second prism set, and the P-polarized light or Between each prism set and a polarization conversion means for aligning linearly polarized light emitted from each prism set to one of P-polarized light or S-polarized light by rotating one polarization direction of S-polarized linearly polarized light by 90 degrees And an angle selection film having a characteristic of transmitting light incident at a small incident angle and reflecting light incident at a large incident angle.

  The second prism set is arranged so that the slopes of the pair of right-angle prisms of the first prism set and the slopes of the pair of right-angle prisms of the second prism set are orthogonal to each other, and the optical path changing means is A polarization separation film provided between the pair of right-angle prisms of the second prism set and having the same characteristics as the polarization separation film provided in the first prism set; A plurality of right angle prism elements arranged such that the ridge lines are parallel to each other and arranged on the same plane, and the ridge lines are inclined by 45 degrees with respect to the polarization directions of the linearly polarized light of P-polarized light and S-polarized light. The polarization direction of the linearly polarized light is provided on the side surface on the incident side of the two prism sets, and the total linear reflection of the incident linearly polarized light by the pair of inclined surfaces of the right-angle prism element. The is rotated 90 degrees, is causing it is preferable emit linearly polarized light after conversion to the incident direction and opposite.

  Further, the second prism set is arranged so that the inclined surfaces of the pair of right-angle prisms of the first prism set are parallel to the inclined surfaces of the pair of right-angle prisms of the second prism set, and the optical path change The means is a reflection film provided between the pair of right-angle prisms of the second prism set, and reflects the incident linearly polarized light, and the polarization conversion means is provided on one of the exit side surfaces of the prism sets. A λ / 2 retardation film that is provided and rotates the polarization direction of transmitted linearly polarized light by 90 degrees may be used.

  According to the present invention, since the angle selection film having the characteristic of transmitting the light incident at a small incident angle and reflecting the light incident at a large incident angle is provided between the prism sets, the light is incident with an inclination. Non-polarized incident light can be appropriately converted into linearly polarized light.

It is explanatory drawing which shows schematically the structure of the light source device of a liquid crystal projector. It is an external view of a polarization illumination optical element. It is a graph which shows the characteristic of the angle selection film | membrane with respect to 0-10 degree incident light. It is a graph which shows the characteristic of the angle selection film | membrane with respect to 80-90 degree incident light. It is a partially broken perspective view which shows the structure of a polarization illumination optical element. It is explanatory drawing which shows the optical path of the light which injected perpendicularly | vertically. It is explanatory drawing which shows the optical path of the light which inclined and entered. It is explanatory drawing which shows the case where there is no angle selection film | membrane. It is explanatory drawing which shows the example which has arrange | positioned each prism set so that the inclined surface of each right angle prism may become parallel. It is explanatory drawing which shows the optical path of the light which inclined and entered. It is explanatory drawing which shows the case where there is no angle selection film | membrane.

  As shown in FIG. 1, the light source device of the liquid crystal projector includes a light source lamp 2 used together with the reflector 3. As the light source lamp 2, a high-intensity lamp such as an ultra-high pressure mercury lamp is used. In the illumination optical path, a filter 4 for cutting infrared rays and ultraviolet rays is provided, and unpolarized / visible illumination light obtained by combining various polarized lights is incident on the first lens array 5. The first lens array 5 is formed by arranging a plurality of segment lenses in a rectangular matrix so as to follow the rectangular shape of the liquid crystal display panel. Divide into multiple luminous fluxes.

  The illumination light emitted from each segment lens of the second lens array 6 enters the polarization illumination optical element 7 as a substantially parallel light beam. The polarized illumination optical element 7 has a function of separating linearly polarized light having a polarization direction perpendicular to the paper surface from unpolarized illumination light including various polarized light and making it incident on the illumination lens 8. The illumination lens 8 guides the linearly polarized light emitted from the polarization illumination optical element 7 into the effective screen of the liquid crystal display panel, and thereby can efficiently illuminate the liquid crystal display panel with the linearly polarized light.

  As shown in FIG. 2, the polarization illumination optical element 7 has a rectangular parallelepiped appearance, and includes a polarization beam splitter array 10 and a plurality of prism sheets (polarization conversion means) 12 bonded to the light incident surface side. It is composed of The polarizing beam splitter array 10 includes a first prism set 14 in which a pair of right-angle prisms 20 and 21 is combined, and a second prism set 15 in which a pair of right-angle prisms 22 and 23 are similarly combined. Are arranged in a row alternately in a direction perpendicular to the optical axis. The right-angle prisms 20 to 23 are formed as right-angled isosceles triangular prisms having the same shape. For the right-angle prisms 20 to 23, for example, optical glass (BK7) having a refractive index of 1.52 is used.

  The first prism set 14 forms an outer shape of a regular quadrangular prism by combining and joining the right-angle prisms 20 and 21 so as to match the slopes of each other. Similarly, the second prism set 15 has an outer shape of a regular quadratic prism by combining and joining the right-angle prisms 22 and 23 so as to match the slopes of each other. The prism sets 14 and 15 are joined adjacently so that the side surfaces are aligned. Here, the inclined surfaces of the right-angle prisms 20 to 23 are surfaces including the oblique sides of both the top surface and the bottom surface formed in a right-angled isosceles triangle.

  The polarization beam splitter array 10 is formed in a rectangular parallelepiped shape by joining a plurality of prism sets 14 and 15 in this way. Further, in the polarization beam splitter array 10, the prism sets 14 and 15 are joined with their orientation determined so that the inclined surfaces of the right-angle prisms 20 and 21 and the inclined surfaces of the right-angle prisms 22 and 23 are orthogonal to each other.

  Between the right-angle prisms 20 and 21 of the first prism set 14, a polarization separation film 16 made of a dielectric multilayer film is provided. A similar polarization separation film (optical path changing means) 17 is also provided between the right-angle prisms 22 and 23 of the second prism set 15. The polarization separation films 16 and 17 transmit linearly polarized light having a P polarization component (having a polarization direction parallel to a plane including the normal line of the polarization separation films 16 and 17 and the incident light) and linearly polarized light having an S polarization component. It has the property of reflecting light (having a polarization direction orthogonal to the polarization direction of linearly polarized light of the P-polarized component).

  In addition, an angle selection film 18 having a property of transmitting or reflecting the incident light according to the incident angle of the incident light is provided between the prism sets 14 and 15. As shown in FIG. 3, when light in the visible range of 400 to 700 nm is incident at an incident angle of 0 to 10 degrees, the angle selection film 18 transmits almost 100% of the light. On the other hand, as shown in FIG. 4, when the light in the visible range of 400 to 700 nm is incident at an incident angle of 80 to 90 degrees, the angle selection film 18 reflects the light almost 100%. Here, the incident angle is an angle formed by the incident light beam with respect to the normal line set at the incident point, and therefore, the light incident at the incident angle of 0 degrees is the normal line to the surface of the angle selection film 18. The light is incident in parallel with the light (light incident perpendicular to the surface).

Thus, the angle selection film 18 has a characteristic of transmitting light incident at a small incident angle and reflecting light incident at a large incident angle. The angle selection film 18 is formed by, for example, forming a single layer film of silicon oxide (SiO ₂ ) having a refractive index of 1.46 with a thickness of about 0.5 μm.

  The prism sheet 12 is provided corresponding to each second prism set 15 included in the polarization beam splitter array 10. The prism sheet 12 is formed in a strip shape having substantially the same outer shape as the side surface of the right-angle prism 22, and is joined to the right-angle prism 22 so as to cover the incident side surface. The prism sheet 12 can be made of transparent plastic or glass.

  As described above, in the polarizing beam splitter array 10, among the side surfaces of the right-angle prisms 20 and 22 facing the second lens array 6, the side surface of the right-angle prism 20 is exposed to the outside, and the side surface of the right-angle prism 22 is the prism sheet 12. Covered by. In addition, if the part which covers the side surface of the right-angle prism 20 is made into a parallel plane, it is also possible to make one sheet in which a plurality of strip-shaped prism sheets 12 are connected.

  As shown in FIG. 5, the prism sheet 12 is formed with a plurality of right-angle prism elements 26 arranged such that their ridge lines are parallel and on the same plane. The right-angle prism element 26 is formed such that each ridge line is inclined by 45 degrees with respect to each ridge line of the right-angle prisms 20 to 23. The prism sheet 12 is formed on the pair of inclined surfaces of the right-angle prism element 26 when the linearly polarized light of the S-polarized component reflected by the polarization separation film 17 exits from the side surface of the right-angle prism 22 and enters the inclined surface of the right-angle prism element 26. By performing total internal reflection twice, the optical path of the incident linearly polarized light of the S-polarized component is inverted by 180 degrees and emitted in the direction opposite to the incident direction, and the polarization direction is rotated by 90 degrees. As described above, the prism sheet 12 converts the linearly polarized light of the S-polarized component emitted from the side surface of the right-angle prism 22 into the linearly polarized light of the P-polarized component and makes it incident on the polarization separation film 17 again.

  Next, the operation of the polarized illumination optical element 7 will be described. Unpolarized illumination light in which chief rays are emitted from the individual microlenses constituting the second lens array 6 substantially in parallel enters the polarized illumination optical element 7 for each microlens. As shown in FIG. 6, the illumination light emitted from the microlens enters the polarization separation film 16 through the side surface of the right-angle prism 20 of the first prism set 14 at an incident angle of 45 degrees.

  The polarization separation film 16 transmits the linearly polarized light of the P-polarized component from the incident illumination light and reflects the linearly polarized light of the S-polarized component by 90 degrees. The transmitted linearly polarized light of the P-polarized component passes through the right-angle prism 21 as it is and exits from the first prism set 14.

  The linearly polarized light of the S-polarized component reflected by the polarization separation film 16 is incident on the angle selection film 18 at an incident angle of about 0 degrees, is transmitted through the angle selection film 18, and is incident on the right-angle prism 22 of the second prism set 15. To do. Then, the light is reflected again by the polarization separation film 17 of the second prism set 15 facing the polarization separation film 16 at an apex angle of 90 degrees, and is emitted from the side surface of the right-angle prism 22 toward the prism sheet 12.

  This linearly polarized light is polarized light composed of an S-polarized component whose polarization direction (polarization plane) is perpendicular to the paper surface, but is incident on a right-angle prism element 26 whose ridge line is inclined 45 degrees with respect to the polarization direction. Then, the polarization direction is rotated by 90 degrees while the inner surfaces are totally reflected by the pair of inclined surfaces, and the linearly polarized light emitted from the first prism set 14 becomes a linearly polarized light having a P-polarized component whose polarization direction is parallel to the paper surface. To be aligned.

  The converted linearly polarized light of the P-polarized component is incident on the polarization separation film 17 again. Then, the light passes through the polarization separation film 17 and the right-angle prism 23 and is emitted from the second prism set 15 in the same direction as the linearly polarized light of the P-polarized component emitted from the first prism set 14. Accordingly, the linearly polarized light of the S-polarized component separated by the polarization separation film 16 can be used as illumination light for the liquid crystal display panel together with the linearly polarized light of the P-polarized component transmitted through the polarization separation film 16. .

  By the way, the non-polarized illumination light irradiated to the polarized illumination optical element 7 from the second lens array 6 does not all become parallel to the optical axis, and as shown in FIGS. The light beam is incident on the side surface of the right-angle prism 22 with an inclination of about 5 degrees (hereinafter, a light beam incident with an inclination is referred to as an inclined light beam).

  As shown in FIG. 8, when the angle selection film 18 is not provided between the prism sets 14 and 15, the inclined light beam passes through the boundary portion of the right-angle prisms 20 and 22, and the first prism set 14. The incident light may enter the polarization separation film 17 on the second prism set 15 side instead of the polarization separation film 16 on the side. When the inclined light beam enters the polarization separation film 17 in this way, the linearly polarized light of the S-polarized component contained in the inclined light beam is reflected by the polarization separation films 16 and 17 and then emitted from the side surface of the right-angle prism 20 to the light source side. It becomes unnecessary light.

  On the other hand, when the angle selection film 18 is provided between the prism sets 14 and 15, as shown in FIG. 7, the inclined light beam incident from the side surface of the right-angle prism 20 with an inclination of about 5 degrees is about The light enters the angle selection film 18 at an incident angle of 85 degrees, is reflected by the angle selection film 18, and enters the polarization separation film 16. Then, after entering the polarization splitting film 16, it follows the same path as the light ray perpendicularly incident on the side surface of the right-angle prism 20 (see FIG. 6), and is converted into the linearly polarized light of the P-polarized component. The light is emitted from the prism set 15.

  As described above, if the angle selection film 18 is provided between the prism sets 14 and 15, it is possible to prevent the linearly polarized light of the S-polarized component contained in the inclined light rays from being emitted to the light source side and becoming unnecessary light. It can be appropriately converted into linearly polarized light of the polarization component. By using this polarized illumination optical element 7, it becomes possible to extract linearly polarized light of P-polarized component from the illumination light irradiated from the light source lamp 2 as non-polarized light with almost no loss. The panel can be illuminated efficiently.

  Next, a second embodiment of the present invention will be described. Note that the same functions and configurations as those of the above embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The polarization illumination optical element 40 of this embodiment includes a polarization beam splitter array 42. Similarly to the first embodiment, the polarization beam splitter array 42 includes a first prism set 44 that combines a pair of right-angle prisms 50 and 51, and a second prism set 45 that combines a pair of right-angle prisms 52 and 53. And a plurality of these are alternately arranged. Further, in the polarizing beam splitter array 42 of the present embodiment, the prism sets 44 and 45 are joined by determining the direction so that the inclined surfaces of the right-angle prisms 50 and 51 and the inclined surfaces of the right-angle prisms 52 and 53 are parallel. .

  Between the right-angle prisms 50 and 51 of the first prism set 44, there is provided a polarization separation film 46 having the characteristics of transmitting linearly polarized light of P-polarized component and reflecting linearly polarized light of S-polarized component. Between the right-angle prisms 52 and 53 of the second prism set 45, a reflection film (optical path changing means) 47 that reflects incident P-polarized component or S-polarized component linearly polarized light is provided. An angle selection film 48 having the same characteristics as the angle selection film 18 of the first embodiment is provided between the prism sets 44 and 45.

  A light shielding film 56 is provided on the side surface of the right-angle prism 52 facing the second lens array 6 to prevent unpolarized illumination light irradiated from the second lens array 6 from entering. On the other hand, the side surface of the right-angle prism 50 facing the second lens array 6 is exposed to the outside. Accordingly, the illumination light is incident only on the first prism set 44. Further, on the side surface of the right-angle prism 53, there is provided a λ / 2 retardation film (polarization conversion means) 58 for rotating the polarization direction by 90 degrees when the P-polarized component or the S-polarized component linearly polarized light is transmitted. ing.

  Next, the operation of this embodiment will be described. The non-polarized illumination light irradiated by the second lens array 6 enters the polarization separation film 46 through the side surface of the right-angle prism 50 of the first prism set 44 at an incident angle of 45 degrees. The polarization separation film 46 transmits the linearly polarized light of the P-polarized component from the incident illumination light and reflects the linearly polarized light of the S-polarized component by 90 degrees. The transmitted linearly polarized light of the P-polarized component passes through the right-angle prism 51 and is emitted from the first prism set 44 as it is.

  The linearly polarized light of the S-polarized component reflected by the polarization separation film 46 enters the angle selection film 48 at an incident angle of about 0 degrees, passes through the angle selection film 48, and enters the right-angle prism 53 of the second prism set 45. To do. The linearly polarized light of the S-polarized component incident on the right-angle prism 53 is incident on the reflection film 47 facing the polarization separation film 46 in parallel. The reflection film 47 reflects the incident S-polarized component linearly polarized light in the same direction as the P-polarized component linearly polarized light emitted from the first prism set 44, and enters the λ / 2 retardation film 58. Let The λ / 2 retardation film 58 rotates the polarization direction of the incident S-polarized component linearly polarized light by 90 degrees to convert it into P-polarized component linearly polarized light, and converts it into the linearly polarized light emitted from the first prism set 44. Align the polarization direction. As a result, as in the first embodiment, the linearly polarized light of the S-polarized component separated by the polarization separation film 46 is also illuminated on the liquid crystal display panel together with the linearly polarized light of the P-polarized component transmitted through the polarization separation film 46. It can be used as light.

  By the way, as shown in FIG. 11, when the angle selection film 48 is not provided between the prism sets 44 and 45, the inclined light beam included in the illumination light does not enter the polarization separation film 46, and the right-angle prism. In some cases, the light passes through the boundary between 50 and 53 and enters the λ / 2 retardation film 58. In this case, the linearly polarized light of the P-polarized component contained in the inclined light beam is converted into linearly polarized light of the S-polarized component, and the linearly polarized light of S-polarized component is converted to the linearly polarized light of the P-polarized component, The light is emitted from the polarization illumination optical element 40 as linearly polarized light in which the P-polarized component and the S-polarized component are mixed. Then, the linearly polarized light of the S polarization component cannot be used as illumination light for the liquid crystal display panel, and thus becomes so-called stray light.

  On the other hand, when the angle selection film 48 is provided between the prism sets 44 and 45, the inclined light beam is reflected by the angle selection film 18 and enters the polarization separation film 46 as shown in FIG. Then, after entering the polarization separation film 46, the light follows a path similar to that of light incident perpendicularly to the side surface of the right-angle prism 50 (see FIG. 9), and is converted into linearly polarized light having a P-polarized component to be converted into each prism. The light is emitted from the sets 44 and 45.

  As described above, even when the prism sets 44 and 45 are arranged so that the inclined surfaces of the right-angle prisms 50 and 51 and the inclined surfaces of the right-angle prisms 52 and 53 are parallel, the angle is selected between the prism sets 44 and 45. By providing the film 48, the linearly polarized light in which the P-polarized component and the S-polarized component are mixed is prevented from being emitted from the polarized illumination optical element 40, and the same effect as in the first embodiment is obtained. Obtainable.

  In the second embodiment, the λ / 2 retardation film 58 is provided on the side surface of the right-angle prism 53 of the second prism set 45 so that the illumination light is emitted in alignment with the linearly polarized light of the P-polarized component. However, on the contrary, a λ / 2 retardation film 58 may be provided on the side surface of the right-angle prism 51 of the first prism set 44 so that the illumination light is emitted in alignment with the linearly polarized light of the S polarization component. .

In each of the above embodiments, a single layer film of silicon oxide (SiO ₂ ) is shown as the material of the angle selection films 18 and 48. However, the material of the angle selection films 18 and 48 is not limited to this, and the right-angle prism 20 Any material having a refractive index lower than that of ˜23 and 50˜53 may be used. For example, a single layer film of magnesium fluoride (MgF ₂ ) may be used, or a dielectric multilayer film in which tantalum pentoxide (Ta ₂ O ₅ ) and silicon oxide are alternately stacked may be used. Further, a silicone adhesive having a low refractive index (for example, a refractive index of 1.44) may be used.

  In each of the above embodiments, the angle selection films 18 and 48 that transmit almost 100% of light incident at an incident angle of 0 to 10 degrees and reflect almost 100% of light incident at an incident angle of 80 to 90 degrees are shown. However, the range of the incident angle that the angle selection films 18 and 48 transmit or reflect is not limited to the above.

  In each of the above embodiments, optical glass having a refractive index of 1.52 is used as the material of the right-angle prisms 20 to 23 and 50 to 53. However, the material and the refractive index of the right-angle prisms 20 to 23 and 50 to 53 are the same. It is not limited to.

  In each of the above embodiments, the example in which the polarized illumination optical element of the present invention is applied to the light source device of the liquid crystal projector has been shown. However, the polarized illumination optical element of the present invention is not limited to this and is applied to other optical devices. May be.

7, 40 Polarization illumination optical element 10, 42 Polarization beam splitter array 12 Prism sheet (polarization conversion means)
14, 44 First prism set 15, 45 Second prism set 16, 46 Polarization separation film 17 Polarization separation film (optical path changing means)
18, 48 Angle selection film 20-23, 50-53 Right angle prism 47 Reflection film (optical path changing means)
58 λ / 2 retardation film (polarization conversion means)

Claims (3)

A first prism set formed into a quadrangular prism by combining a pair of right-angle prisms;
A second prism set that is configured substantially the same as the first prism set and is disposed adjacent to the first prism set so that side surfaces thereof are aligned;
Provided between the pair of right-angle prisms of the first prism set, and transmits one of P-polarized light or S-polarized linearly polarized light to be emitted from the first prism set, and reflects the other to reflect the second. A polarization separation film incident on the prism set;
An optical path changing means for changing an optical path of the linearly polarized light incident on the second prism set so as to be emitted in the same direction as the linearly polarized light emitted from the first prism set;
By rotating one polarization direction of P-polarized light or S-polarized linearly polarized light separated by the polarization separation film by 90 degrees, linearly polarized light emitted from each prism set is aligned with either P-polarized light or S-polarized light. Polarization conversion means;
A polarization illumination optical element comprising an angle selection film provided between the prism sets and having a characteristic of transmitting light incident at a small incident angle and reflecting light incident at a large incident angle . The second prism set is arranged so that the slopes of the pair of right-angle prisms of the first prism set and the slopes of the pair of right-angle prisms of the second prism set are orthogonal to each other,
The optical path changing means is a polarization separation film provided between the pair of right angle prisms of the second prism set and having the same characteristics as the polarization separation film provided in the first prism set,
The polarization converting means includes a plurality of right-angle prism elements arranged such that the ridge lines are parallel to each other and aligned on the same plane, and the ridge lines are in a polarization direction of linearly polarized light of P polarization and S polarization. The linearly polarized light is provided on the incident side surface of the second prism set so as to be inclined at 45 degrees, and the incident linearly polarized light is totally internally reflected by the pair of inclined surfaces of the right-angle prism element, thereby changing the polarization direction of the linearly polarized light. 2. The polarization illumination optical element according to claim 1, wherein the polarization illumination optical element is rotated by 90 degrees and emits the linearly polarized light after conversion in a direction opposite to the incident direction. The second prism set is arranged such that the slopes of the pair of right-angle prisms of the first prism set and the slopes of the pair of right-angle prisms of the second prism set are parallel to each other,
The optical path changing means is a reflective film that is provided between the pair of right-angle prisms of the second prism set and reflects incident linearly polarized light.
2. The phase difference film according to claim 1, wherein the polarization conversion means is a λ / 2 phase difference film that is provided on one of the exit side surfaces of each prism set and rotates the polarization direction of the linearly polarized light that is transmitted by 90 degrees. The polarization illumination optical element described.

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