Polarization forming optical device and polarization beam splitter

• US 5,124,841 A
• Filed: 10/15/1990
• Issued: 06/23/1992
• Est. Priority Date: 10/13/1989
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Original Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Inventors: Oishi, Noriji
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/597,819
• Time in Patent Office: 617 Days
• Field of Search: 350/394, 350/401, 350/402, 350/286, 359/487, 359/495, 359/496
• US Class Current: 359/485.02
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/285 comprising arrays of elements, e.g. microprisms
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/13355 Polarising beam splitters [PBS]

Abstract

An optical device for forming a linear polarized light by dividing a light beam from a light source into two linear polarized light components, and rotating a plane of polarization of one of the light components at 90° to follow joining of both the light components. Further, a polarization beam splitter for dividing a light beam into two linear polarized light components is employed in such an optical device.

Claims

1. A polarization forming optical device comprising:

a polarization beam splitter for reflecting one of an s-polarization component and a p-polarization component of light to be emitted from a light source and transmitting the other;

a prism reflecting surface for receiving one of a reflected light and a transmitted light from said polarization beam splitter and rotating a plane of polarization at 90°

to obtain a reflected light component; and

means for deflecting the light advancing from said polarization beam splitter to said prism reflecting surface, the reflected light component from said prism reflecting surface, and/or the other of said reflected light and said transmitted light from said polarization beam splitter, so as to make an advancing direction of an outgoing light based on said reflected light from said polarization beam splitter coincident with an advancing direction of an outgoing light based on said transmitted light from said polarization beam splitter;

wherein said prism reflecting surface comprises a plurality of reflecting mirror surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting mirror surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism reflecting surface.

2. A polarization forming optical device as defined in claim 1, wherein said light source comprises a beam light source for emitting a random polarized light;

first and second polarization beam splitters are laid on an optical axis of said beam light source;

said first and second polarization beam splitters have reflecting surfaces inclined at 45°

with respect to said optical axis of said beam light source and inclined at 90°

with respect to each other; and

said prism reflecting surface is located behind said first and second polarization beam splitters so as to perpendicularly intersect said optical axis of said beam light source;

whereby assuming that Y-axis is parallel to said optical axis of said beam light source;

X-axis is perpendicular to said Y-axis;

X-Y plane is perpendicular to each said reflecting surface; and

Z-axis is perpendicular to said X-Y plane, a light beam of said random polarized light from said beam light source is converted into a linear polarized light having a plane of polarization parallel to said X-Y plane to obtain a light beam outgoing in a direction parallel to said X-axis.

3. A polarization forming optical device as defined in claim 1, wherein said light source comprises a beam light source for emitting a random polarized light;

a single polarization beam splitter is laid on an optical axis of said beam light source;

a reflecting mirror is laid on said optical axis of said beam light source;

said polarization beam splitter has a reflecting surface inclined at 45°

with respect to said optical axis of said beam light source;

said prism reflecting surface is located so that the reflected light from said reflecting surface of said polarization beam splitter enters perpendicularly to said prism reflecting surface; and

said reflecting mirror is inclined at 45°

with respect to said optical axis of said beam light source and inclined at 90°

with respect to said reflecting surface of said polarization beam splitter;

whereby assuming that Y-axis is parallel to said optical axis of said beam light source;

X-axis is perpendicular to said Y-axis;

X-Y plane is perpendicular to both said reflecting surface and said reflecting mirror; and

Z-axis is perpendicular to said X-Y plane, a light beam of said random polarized light from said beam light source is converted into a linear polarized light having a plane of polarization parallel to X-Z plane to obtain a light beam outgoing in a direction parallel to said X-axis.

4. A polarization forming optical device as defined in claim 1, wherein said light source comprises a beam light source for emitting a random polarized light;

a first polarization beam splitter is laid on an optical axis of said beam light source and a second polarization beam splitter is laid on an optical path of a reflected light beam from said first polarization beam splitter;

said first and second polarization beam splitters have reflecting surfaces inclined at 45°

with respect to an incident light beam thereon and inclined at 90°

with respect to each other; and

said prism reflecting surface is located so that the reflected light from said reflecting surface of said second polarization beam splitter enters perpendicularly to said prism reflecting surface;

whereby assuming that X-axis is parallel to said optical axis of said beam light source;

Y-axis is perpendicular to said X-axis;

X-Y plane is perpendicular to each said reflecting surface; and

Z-axis is perpendicular to said X-Y plane, a light beam of said random polarized light from said beam light source is converted into a linear polarized light having a plane of polarization parallel to X-Z plane to obtain a light beam outgoing in a direction parallel to said X-axis.

5. A polarization forming optical device as defined in claim 1, wherein said light source comprises a beam light source for emitting a random polarized light;

a single polarization beam splitter is laid on an optical axis of said beam light source;

said prism reflecting surface is laid on an optical path of a reflected light beam from said polarization beam splitter;

a reflecting mirror is laid on an optical path of a transmitted light beam through said polarization beam splitter after reflected on said prism reflecting surface;

said polarization beam splitter has a reflecting surface inclined at 45°

with respect to an incident light beam thereon;

said reflecting mirror is inclined at 45°

with respect to an incident light beam thereon;

said reflecting surface of said polarization beam splitter is inclined at 90°

with respect to said reflecting mirror; and

said prism reflecting surface is located so that the reflected light from said reflecting surface of said polarization beam splitter enters perpendicularly to said prism reflecting surface;

whereby assuming that X-axis is parallel to said optical axis of said beam light source;

Y-axis is perpendicular to said X-axis;

X-Y plane is perpendicular to each said reflecting surface; and

Z-axis is perpendicular to said X-Y plane, a light beam of said random polarized light from said beam light source is converted into a linear polarized light having a plane of polarization parallel to X-Z plane to obtain a light beam outgoing in a direction parallel to said X-axis.

6. A polarization forming optical device comprising:

two polarization members, each said polarization member including;

a polarization beam splitter for reflecting one of an s-polarization component and a p-polarization component of light emitted from a light source and transmitting the other component;

a prism reflecting surface for receiving one of a reflected light and a transmitted light from said polarization beam splitter and rotating a plane of polarization at 90°

to obtain a reflected light component; and

means for deflecting the light advancing from said polarization beam splitter to said prism reflecting surface, the reflected light component from said prism reflecting surface, and/or the other of said reflected light and said transmitted light from said polarization beam splitter, so as to make an advancing direction of an ongoing light based on said transmitted light from said polarization beam splitter;

wherein said prism reflecting surface comprises a plurality of reflecting mirror surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism deflecting surface;

wherein said light source comprises a beam light source for emitting a random polarized light, and a first polarization beam splitter is located on an optical axis of said beam light source and a second polarization beam splitter is located on an optical path of a reflected light beam from said first polarization beam splitter, said first and second polarization beam splitters having reflecting surfaces inclined at 45°

with respect to an incident light beam thereon and inclined at 90°

with respect to each other, and said prism reflecting surface is located so that the reflected light from said reflecting surface of said second polarization beam splitter enters perpendicularly to said prism reflecting surface, whereby assuming that X-axis is parallel to said optical axis of said beam light source, Y-axis is perpendicular to said X-axis, X-Y plane is perpendicular to each said reflecting surface, and Z-axis is perpendicular to said X-Y plane, a light beam of said random polarized light from said beam light source is converted into a linear polarized light having a plane of polarization parallel to X-Z plane to obtain a light beam outgoing in a direction parallel to said X-axis;

said two polarization members being combined together in symmetrical relationship with respect to said X-Z plane so that two of said first polarization beam splitter are located adjacent to each other, and said beam light source is commonly provided for said two members.

7. A polarization forming optical device comprising:

two polarization members, each said polarization member including;

a polarization beam splitter for reflecting one of an s-polarization component and a p-polarization component of light emitted from a light source and transmitting the other component;

a prism reflecting surface for receiving one of a reflected light and a transmitted light from said polarization beam splitter and rotating a plane of polarization at 90°

to obtain a reflected light component; and

means for deflecting the light advancing from said polarization beam splitter to said prism reflecting surface, the reflected light component from said prism reflecting surface, and/or the other of said reflected light and said transmitted light from said polarization beam splitter, so as to make an advancing direction of an ongoing light based on said transmitted light from said polarization beam splitter;

wherein said prism reflecting surface comprises a plurality of reflecting mirror surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism deflecting surface;

wherein said light source comprises a beam light source for emitting a random polarized light, and a single polarization beam splitter is located on an optical axis of said beam light source, said prism reflecting surface being located on an optical path of a reflected light beam from said polarization beam splitter, a reflecting mirror being located on an optical path of a transmitted light beam through said polarized beam splitter after reflected on said prism reflecting surface, said polarization beam splitter having a reflecting surface inclined at 45°

with respect to an incident light beam thereon, said reflecting mirror being inclined at 45°

with respect to an incident light beam thereon, said reflecting surface of said polarized beam splitter being inclined at 90°

with respect to said reflecting mirror, and said prism reflecting surface being located so that the reflected light from said reflecting surface of said polarization beam splitter enters perpendicularly to said prism reflecting surface, whereby assuming that X-axis is parallel to said optical axis of said beam light source, Y-axis is perpendicular to said X-axis, X-Y plane is perpendicular to each said reflecting surface, and Z-axis is perpendicular to said X-Y plane, a light beam of said random polarized light from said beam light source is converted into a linear polarized light having a plane of polarization parallel to X-Z plane to obtain a light beam outgoing in a direction parallel to said X-axis;

said two polarization members being combined together in symmetrical relationship with respect to said X-Z plane so that two of said prism reflecting surface are located adjacent to each other, and said beam light source is commonly provided for said two members.

8. A polarization forming optical device comprising:

a polarization beam splitter for reflecting one of a p-polarization component and an s-polarization component of light to be emitted from a light source and transmitting the other;

a prism reflecting surface for receiving a reflected light from said polarization beam splitter and rotating a plane of polarization at 90°

to obtain a reflected light component; and

a prism for making an advancing direction of a transmitted light from said polarization beam splitter based on said reflected light component from said prism reflecting surface coincident with an advancing direction of a transmitted light from said polarization beam splitter based on an incident light directly from said light source;

wherein said prism reflecting surface comprises a plurality of reflecting mirror, surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting mirror surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism reflecting surface.

9. A polarization forming optical device as defined in claim 8, wherein said light source comprises a beam light source for emitting a random polarized light;

said polarization beam splitter comprises a mirror type polarization beam splitter laid on an optical axis of said beam light source;

said prism comprises a prism formed plate located at a position where both said transmitted lights pass;

said prism formed plate is a transparent plate having one surface formed with a plurality of prism elements arranged in parallel rows and having the other surface which is planar;

each of said prism elements has two adjacent surfaces inclined at an angle θ

with respect to a normal to said planar surface of said prism formed plate and inclined at an angle 2θ

with respect to each other, said prism elements having a refractive index n;

said prism formed plate is located in such a manner that said planar surface faces said polarization beam splitter, and that a ridgeline of said each prism element is perpendicular to an incident light to said each prism element; and

said angle θ

is related with an incident angle β

of an incident light from said beam light source to said polarization beam splitter so as to satisfy the following equation (1);

space="preserve" listing-type="equation">n sin α

=sin β

space="preserve" listing-type="equation">n cos (α

+θ

)+cos θ

(1)

10. A polarization forming optical device as defined in claim 9, wherein said incident angle β

is 45°

.

11. A polarization forming optical device as defined in claim 10, wherein said mirror type polarization beam splitter includes two transparent plates and a polarizing film interposed between said two transparent plates, each of said transparent plates being formed on its outer side surface with a plurality of prism elements arranged in parallel rows, each of said prism elements having two adjacent surfaces inclined at 45°

with respect to a normal to an inner side surface of each said transparent plate and inclinded at 90°

with respect to each other.

12. A polarization forming optical device as defined in claim 10, wherein said mirror type polarization beam splitter includes a single transparent plate, rectangular prism and a polarizing film interposed between an inner side surface of said transparent plate and a slant surface of said rectangular prism, said transparent plate being formed on its outer side surface with a plurality of prism elements arranged in parallel rows, each of said prism elements having two adjacent surfaces inclined at 45°

with respect to a normal to said inner side surface of said transparent plate and inclined at 90°

with respect to each other.

13. A polarization forming optical device as defined in claim 8, further comprising a phase plate located before said prism reflecting surface.

14. A polarization forming optical device comprising:

a first prism for dividing light to be emitted from a light source into two light beams;

a polarization beam splitter for reflecting one of a p-polarization component and an s-polarization component of each of said two light beams and transmitting the other;

a prism reflecting surface for receiving a reflected light from said polarization beam splitter and rotating a plane of polarization at 90°

to obtain a reflected light component; and

a second prism for making an advancing direction of a transmitted light from said polarization beam splitter based on said reflected light component from said prism reflecting surface coincident with an advancing direction of a transmitted light from said polarization beam splitter based on an incident light directly from said first prism;

wherein said prism reflecting surface comprises a plurality of reflecting mirror surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting mirror surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism reflecting surface.

15. A polarization forming optical device as defined in claim 14, wherein said polarization beam splitter includes two transparent plates and a polarizing film interposed between said two transparent plates, each of said transparent plates being formed on its outer side surface with a plurality of prism elements arranged in parallel rows, each of said prism elements having two adjacent surfaces inclined at 45°

with respect to a normal to an inner side surface of each said transparent plate and inclined at 90°

with respect to each other.

16. A polarization forming optical device as defined in claim 14, further comprising a phase plate located before said prism reflecting surface.

17. A polarization forming optical device comprising:

a first prism for dividing light to be emitted from a light source into two light beams;

a polarization beam splitter for reflecting one of a p-polarization component and an s-polarization component of each of said two light beams and transmitting the other;

a prism reflecting surface for receiving a reflected light from said polarization beam splitter and rotating a plane of polarization at 90°

to obtain a reflected light component; and

a second prism for making an advancing direction of a transmitted light from said polarization beam splitter based on said reflected light component from said prism reflecting surface coincident with an advancing direction of a transmitted light from said polarization beam splitter based on an incident light directly from said first prism;

one of said first prism and said second prism comprising a prism formed plate having one surface formed with a plurality of prism elements arranged in rows;

wherein said prism reflecting surface comprises a plurality of reflecting mirror surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting mirror surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism reflecting surface.

18. A polarization forming optical device comprising:

a polarizing film for reflecting one of a p-polarization component and an s-polarization component of light to be emitted from a light source and transmitting the other;

a prism reflecting surface for receiving a reflected light from said polarizing film and rotating a plane of polarization at 90°

to obtain a reflected light component;

a reflecting mirror for changing an advancing direction of one of a transmitted light from said polarizing film based on said reflected light component from said prism reflecting surface and a transmitted light from said polarizing film based on an incident light directly from said light source in such a manner that both said transmitted lights intersect each other; and

a prism for making advancing directions of both said transmitted lights intersected coincident with each other to synthesize both said transmitted lights;

wherein said prism reflecting surface comprises a plurality of reflecting mirror surfaces, adjacent ones of which are perpendicular to each other, said reflecting mirror surfaces being arranged in rows in a direction perpendicular to a ridgeline formed between said adjacent reflecting mirror surfaces, said direction of arrangement of said rows of said reflecting mirror surfaces being inclined at 45°

with respect to said plane of polarization of the incident light on said prism reflecting surface.

19. A polarization forming optical device as defined in claim 18, further comprising a phase plate located before said prism reflecting surface.