Polarization conversion unit, polarization illumination apparatus provided with the unit, and projector provided with the apparatus

• US 5,381,278 A
• Filed: 11/01/1993
• Issued: 01/10/1995
• Est. Priority Date: 05/07/1991
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kimura, Kazumi, Mitsutake, Hideaki, Shingaki, Junko
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US08/146,801
• Time in Patent Office: 435 Days
• Field of Search: 359/256, 359/495, 359/496, 359/497, 359/499, 359/63, 359/65
• US Class Current: 359/256
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A polarization conversion unit is disclosed. In the unit, a definitely polarized light emitted from a light source is divided into a pair of lights differing in polarized state and are caused to be incident on the optical components including the polarizing beam splitter. The plane of polarization of one of the paired polarized light is rotated to be coincident with the plane of polarization of the other light by the optical components, so that the paired lights with the same plane of polarization are caused to be separately emitted. The optical component has a plano-convex lens which has a positive power and which is arranged at an exit side where the paired lights are separately emitted. The lens has a focal point at a position further than the position of the surface to be illuminated.

Claims

1. A polarization conversion unit, which splits light into a pair of polarized light components having different polarization states, causes the polarization states of the pair of split polarized light components to coincide with each other, respectively outputs the pair of polarized light components having the coinciding polarization states, and illuminates a surface to be illuminated, comprising:

converging means for converging each of said pair of polarized light components onto a converging point,

wherein said converging means has an optical axis which is between central rays of said pair of polarized light components,

wherein said converging point is farther than the surface to be illuminated.

2. A unit according to claim 1, further comprising a polarization plate, which is arranged in an optical path of the pair of polarized light components propagating through said converging means, and has a polarization axis to transmit the pair of polarized light components.

3. A projector comprising:

a light source;

a polarization conversion unit for splitting light emitted from said light source into a pair of polarized light components having different polarization states, causing the polarization states of the pair of split polarized light components to coincide with each other, and respectively outputting the pair of polarized light components having the coinciding polarization states,

said polarization conversion unit having converging means for converging each of said pair of polarized light components onto a converging point,

wherein said converging means has an optical axis which is between central rays of said pair of polarized light components,

wherein said converging point is farther than the surface to be illuminated;

an image generator for modulating the pair of polarized light components emerging from said polarization conversion unit to generate an image; and

a projection optical system for projecting the image.

4. A projector according to claim 3, further comprising a polarization plate, which is arranged in an optical path of the pair of polarized light components propagating through said converging means, and between said converging means and said image generator, and has a polarization axis to transmit the pair of polarized light components.

5. A polarization conversion unit for splitting light into a pair of polarized light components having different polarization states, causing the polarization states of the pair of split polarized light components to coincide with each other, and separately outputting the pair of polarized light components having the coinciding polarization states, comprising at least one of:

a first optical element for converging the polarized light component having a smaller light amount per unit sectional area than that of the other polarized light component of the pair of polarized light components, and a second optical element for diverging the polarized light component having a larger light amount per unit sectional area than that of the other polarized light component of the pair of polarized light components.

6. A unit according to claim 5, further comprising a polarization plate, which is arranged in an optical path of the pair of emerging polarized light components, and has an optical axis to transmit both the polarized light components.

7. A projector comprising:

a light source;

a polarization conversion unit for splitting light emitted from said light source into a pair of polarized light components having different polarization states, causing the polarization states of the pair of split polarized light components to coincide with each other, and separately outputting the pair of polarized light components having the coinciding polarization states,

said polarization conversion unit having at least one of a first optical element for converging the polarized light component having a smaller light amount per unit sectional area than that of the other polarized light component of the pair of polarized light components, and a second optical element for diverging the polarized light component having a larger light amount per unit sectional area than that of the other polarized light component of the pair of polarized light components;

an image generator for modulating the pair of emerging polarized light components to generate an image; and

a projection optical system for projecting the image.

8. A projector according to claim 7, further comprising a polarization plate, which is arranged in an optical path of the pair of polarized light components emerging from said polarization conversion unit, and has an optical axis to transmit both the polarized light components.

9. A polarization illumination apparatus comprising:

illumination means for emitting light;

a pair of polarization splitting surfaces for splitting some light components of the light into reflection light and transmission light, which have different polarization states, said pair of polarization splitting surfaces being obliquely arranged in an optical path of the light to face each other, so that one end of one polarization splitting surface contacts one end of the other polarization splitting surface;

a pair of λ

/4 optical phase plates for changing the polarization state of the reflection light to cause the polarization states of the reflection light and the transmission light to coincide with each other, said pair of λ

/4 optical phase plates being arranged at an incident side of the light of said pair of polarization splitting surfaces to be substantially parallel to said pair of polarization splitting surfaces, respectively;

a pair of reflection surfaces for reflecting the reflection light from one of said pair of polarization splitting surfaces in substantially the same direction as a propagation direction of the transmission light through said pair of λ

/4 optical phase plates and the other polarization splitting surface, said pair of reflection surfaces being arranged to sandwich said pair of polarization splitting surfaces therebetween;

reflectors for reflecting remaining light components of the light incident on a portion other than said pair of polarization splitting surfaces, and returning the reflected light components to said illumination means, said reflectors being arranged to be perpendicular to the light emitted from said illumination means and at a side, facing said illumination means, of said reflection surfaces; and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light.

10. A projector comprising:

illumination means for emitting light;

a pair of polarization splitting surfaces for splitting some light components of the light into reflection light and transmission light, which have different polarization states, said pair of polarization splitting surfaces being obliquely arranged in an optical path of the light to face each other, so that one end of one polarization splitting surface contacts one end of the other polarization splitting surface;

a pair of λ

/4 optical phase plates for changing the polarization state of the reflection light to cause the polarization states of the reflection light and the transmission light to coincide with each other, said pair of λ

/4 optical phase plates being arranged at an incident side of the light of said pair of polarization splitting surfaces to be substantially parallel to said pair of polarization splitting surfaces, respectively;

a pair of reflection surfaces for reflecting the reflection light from one of said pair of polarization splitting surfaces in substantially the same direction as a propagation direction of the transmission light through said pair of λ

/4 optical phase plates and the other polarization splitting surface, said pair of reflection surfaces being arranged to sandwich said pair of polarization splitting surfaces therebetween;

reflectors for reflecting remaining light components of the light incident on a portion other than said pair of polarization splitting surfaces, and returning the reflected light components to said illumination means, said reflectors being arranged to be perpendicular to the light emitted from said illumination means and at a side, facing said illumination means, of said reflection surfaces;

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light;

an image generator for modulating the reflection light and the transmission light having the coinciding polarization state to generate an image; and

a projection optical system for projecting the image.

11. A polarization illumination apparatus comprising:

illumination means for emitting light; and

a planar polarization conversion unit constituted by a plurality of units which are arranged along a common plane crossing the light,

each of said units comprising

a pair of polarization splitting surfaces for splitting some light components of the light into reflection light and transmission light, which have different polarization states, said pair of polarization splitting surfaces being obliquely arranged in an optical path of the light to face each other, so that one end of one polarization splitting surface contacts one end of the other polarization splitting surface,

a pair of λ

/4 optical phase plates for changing the polarization state of the reflection light to cause the polarization states of the reflection light and the transmission light to coincide with each other, said pair of λ

/4 optical phase plates being arranged at an incident side of the light of said pair of polarization splitting surfaces to be substantially parallel to said pair of polarization splitting surfaces, respectively,

a pair of reflection surfaces for reflecting the reflection light from one of said pair of polarization splitting surfaces in substantially the same direction as a propagation direction of the transmission light through said pair of λ

/4 optical phase plates and the other polarization splitting surface, said pair of reflection surfaces being arranged to sandwich said pair of polarization splitting surfaces therebetween,

reflectors for reflecting remaining light components of the light incident on a portion other than said pair of polarization splitting surfaces, and returning the reflected light components to said illumination means, and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light.

12. An apparatus according to claim 11, wherein said reflectors are arranged to be perpendicular to the light emitted from said illumination means and at a side, facing said illumination means, of said reflection surfaces.

13. An apparatus according to claim 11, wherein said reflectors are arranged on a back side of said reflection surfaces to be parallel to said reflection surfaces.

14. A projector comprising:

illumination means for emitting light;

a planar polarization conversion unit constituted by a plurality of units which are arranged along a common plane crossing the light,

each of said units comprising

a pair of polarization splitting surfaces for splitting some light components of the light into reflection light and transmission light, which have different polarization states, said pair of polarization splitting surfaces being obliquely arranged in an optical path of the light to face each other, so that one end of one polarization splitting surface contacts one end of the other polarization splitting surface,

a pair of λ

/4 optical phase plates for changing the polarization state of the reflection light to cause the polarization states of the reflection light and the transmission light to coincide with each other, said pair of λ

/4 optical phase plates being arranged at an incident side of the light of said pair of polarization splitting surfaces to be substantially parallel to said pair of polarization splitting surfaces, respectively,

a pair of reflection surfaces for reflecting the reflection light from one of said pair of polarization splitting surfaces in substantially the same direction as a propagation direction of the transmission light through said pair of λ

/4 optical phase plates and the other polarization splitting surface, said pair of reflection surfaces being arranged to sandwich said pair of polarization splitting surfaces therebetween,

reflectors for reflecting remaining light components of the light incident on a portion other than said pair of polarization splitting surfaces, and returning the reflected light components to said illumination means, and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light;

an image generator for modulating a pair of modulated light components emerging from said planar polarization conversion unit to generate an image; and

a projection optical system for projecting the image.

15. A projector according to claim 14, wherein said reflectors are arranged to be perpendicular to the light emitted from said illumination means and at a side, facing said illumination means, of said reflection surfaces.

16. A projector according to claim 14, wherein said reflectors are arranged on a back side of said reflection surfaces to be parallel to said reflection surfaces.

17. A polarization illumination apparatus comprising:

illumination means for emitting light; and

a planar polarization conversion unit constituted by a plurality of units which are arranged along a common plane crossing the light,

each of said units comprising

a pair of polarization splitting surfaces for splitting some light components of the light into reflection light and transmission light, which have different polarization states, said pair of polarization splitting surfaces being obliquely arranged in an optical path of the light to face each other, so that one end of one polarization splitting surface contacts one end of the other polarization splitting surface,

a pair of λ

/2 optical phase plates for changing the polarization state of the reflection light to cause the polarization states of the reflection light and the transmission light to coincide with each other, said pair of λ

/2 optical phase plates being arranged between said pair of polarization splitting surfaces,

a pair of reflection surfaces for reflecting the reflection light from one of said pair of polarization splitting surfaces in substantially the same direction as a propagation direction of the transmission light through said pair of λ

/2 optical phase plates and the other polarization splitting surface, said pair of reflection surfaces being arranged to sandwich said pair of polarization splitting surfaces therebetween,

reflectors for reflecting remaining light components of the light incident on a portion other than said pair of polarization splitting surfaces, and returning the reflected light components to said illumination means, and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light.

18. A polarization illumination apparatus comprising:

illumination means for emitting light; and

a planar polarization conversion unit constituted by a plurality of units which are arranged along a common plane crossing the light,

each of said units comprising

a polarization splitting surface for splitting some light components of the light into reflection light and transmission light having different polarization states, said polarization splitting surface being obliquely arranged in an optical path of the light,

a λ

/2 optical phase plate for causing the polarization states of the reflection light and the transmission light to coincide with each other, said λ

/2 optical phase plate being arranged in an optical path of one of the reflection light and the transmission light,

a reflection surface for reflecting the reflection light from said polarization splitting surface in a direction substantially the same as a propagation direction of the transmission light, said reflection surface being arranged to be almost parallel to said polarization splitting surface,

a reflector for reflecting remaining light components of the light incident on a portion other than said polarization splitting surface, and returning the reflected light components to said illumination means, and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light.

19. An apparatus according to claim 18, wherein said λ

/2 optical phase plate is arranged in an optical path of the reflection light reflected by said reflection surface.

20. An apparatus according to claim 18, wherein said λ

/2 optical phase plate is arranged between said polarization splitting surface and said reflection surface.

21. A projector comprising:

illumination means for emitting light;

a color separation system for separating the light from said illumination light into red, green, and blue color light components;

three planar polarization conversion units, which correspond to the color light components, and each of which is constituted by a plurality of units arranged along a common plane crossing the corresponding color light component,

each of said units comprising

a polarization splitting surface for splitting some light components of the light into reflection light and transmission light having different polarization states,

an optical phase plate for changing the polarization state of at least one of the reflection light and the transmission light to cause the polarization states of the reflection light and the transmission light to coincide with each other,

a reflection surface for reflecting the reflection light in a direction substantially the same as a propagation direction of the transmission light,

means for reflecting remaining light components of the light incident on a portion other than said polarization splitting surface, and returning the reflected light components to said illumination means, at least some light components of the light returned to said illumination means being incident on said polarization splitting surface, and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light;

an image generator for modulating red, blue, and green reflection and transmission light components emerging from said three polarization conversion units to generate an image; and

a projection optical system for projecting the image.

22. A projector comprising:

illumination means for emitting light;

a color separation system for separating the light from said illumination light into red, green, and blue color light components;

two planar polarization conversion units, which are respectively arranged in a common optical path of the two color light components of the three color light components, and an optical path of the remaining color light component, and each of which is constituted by a plurality of units arranged along a common plane crossing the corresponding color light component,

each of said units comprising

a polarization splitting surface for splitting some light components of the light into reflection light and transmission light having different polarization states,

an optical phase plate for changing the polarization state of at least one of the reflection light and the transmission light to cause the polarization states of the reflection light and the transmission light to coincide with each other,

a reflection surface for reflecting the reflection light in a direction substantially the same as a propagation direction of the transmission light,

means for reflecting remaining light components of the light incident on a portion other than said polarization splitting surface, and returning the reflected light components to said illumination means, at least some light components of the light returned to said illumination means being incident on said polarization splitting surface, and

an optical element comprising at least one of a first optical element, arranged in an optical path of the reflection light, for converging the reflection light, and a second optical element, arranged in an optical path of the transmission light, for diverging the reflection light;

an image generator for modulating red, blue, and green reflection and transmission light components emerging from said three polarization conversion units to generate an image; and

a projection optical system for projecting the image.

23. A polarization conversion unit, which splits light into a pair of polarized light components having different polarization states, causes the polarization states of the pair of split polarized light components to coincide with each other, respectively outputs the pair of polarized light components having the coinciding polarization states, and illuminates a surface to be illuminated, comprising:

a convex lens for converging each of said pair of polarized light components onto a converging point,

wherein said converging means has an optical axis which is between central rays of said pair of polarized light components,

wherein said converging point is farther than the surface to be illuminated.