Illumination system and projector

• US 6,513,953 B1
• Filed: 02/22/2000
• Issued: 02/04/2003
• Est. Priority Date: 02/23/1999
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Itoh, Yoshitaka
• Primary Examiner(s): Tso, Laura K.
• Application Number:
  US09/510,678
• Time in Patent Office: 1,078 Days
• Field of Search: 362/19, 362/331, 362/308, 359/487, 353/20
• US Class Current: 362/331
• 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: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G02B 3/0068 arranged in a single integral body or plate, e.g. laminates or hybrid structures with other optical elements G02B5/1885, G02B17/002, G02B30/27 take precedence
• 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

Abstract

An illumination system includes a light source that emits unpolarized light, a power variation optical relay system that changes the size of a light beam emitted by the light source, a superposition optical system that effects illumination of an illumination region by an incident light beam, a polarization conversion system that is provided at a selected position along a light path from the incident surface of the power variation optical relay system to the exit surface of the superposition optical system to convert an incident beam of unpolarized light to a light beam having linearly polarized components with one type of polarization direction and emits the converted light beam. The size of a light beam entering the polarization conversion system in a prescribed direction is reduced by the power variation optical relay system. The illumination system includes an integrator optical system and polarization conversion system that uses a light source lamp with a higher output than a conventional lamp, and allows the light output to be increased without decreasing the utilization efficiency of the illumination system.

Claims

1. An illumination system that illuminates a light incident surface of an optical device as an illumination region, the system comprising:

a light source that emits unpolarized light,

a power variation optical relay system that changes a size of a light beam emitted by the light source,

a superposition optical system that effects illumination of the illumination region by a given incident light beam, and

a polarization conversion system that is provided at a selected position along a light path from an incident surface of the power variation optical relay system to an exit surface of the superposition optical system to convert an incident beam of unpolarized light to a light beam having a linearly polarized component with one type of polarization direction and emits the converted light beam,

wherein a size of a light beam entering the polarization conversion system is reduced in a prescribed direction by the power variation optical relay system.

2. The illumination system according to claim 1, wherein the power variation optical relay system includes:

a first lens array having a plurality of first small lenses,

a relay lens array having a plurality of relay lenses that is disposed on a light emission side of the first lens array, and

a second lens array having a plurality of second small lenses that is disposed on a light emission side of the relay lens array,

wherein the first lens array and the second lens array are disposed at conjugate points of the relay lens array, and

wherein the polarization conversion system includes;

a polarization beam splitter array that has a plurality of pairs of mutually parallel polarization splitting film and reflecting film in an inclined state along the prescribed direction and separates the incident beam of unpolarized light into a plurality of partial light beams of two types of linearly polarized light, and

a polarization conversion device that converts a polarization direction of a first type of linearly polarized light of the two types of linearly polarized light to a same polarization direction as a second type of linearly polarized light,

wherein a light beam entering the polarization conversion device is split by the power variation optical relay system into a plurality of partial light beams, and the size of each of the plurality of partial light beams in the prescribed direction is reduced by the power variation optical relay system.

3. The illumination system according to claim 2, wherein the superposition optical system includes:

a third lens array having a plurality of third small lenses on which the plurality of partial light beams entering the superposition optical system impinge,

a fourth lens array having a plurality of fourth small lenses corresponding to the plurality of third small lenses, and

a superposition lens that superposes onto the illumination region a plurality of partial light beams passing through the third lens array and the fourth lens array.

4. The illumination system according to claim 3, wherein the polarization conversion system is disposed between the third lens array and the fourth lens array.

5. The illumination system according to claim 4, wherein the second lens array and the third lens array are optically integrated.

6. The illumination system according to claim 2, wherein the superposition optical system includes:

a third lens array having a plurality of small lenses that superposes the plurality of partial light beams substantially on the illumination region, and

a fourth lens array having a plurality of fourth small lenses corresponding to the plurality of third small lenses.

7. The illumination system according to claim 6, wherein the polarization conversion system is disposed between the third lens array and the fourth lens array.

8. The illumination system according to claim 7, wherein the second lens array and the third lens array are optically integrated.

9. The illumination system according to claim 2, wherein the polarization conversion system is disposed between the power variation optical relay system and the superposition optical system.

10. The illumination system according to claim 2, wherein the polarization conversion system is disposed between the relay lens array and the second lens array of the power variation optical relay system.

11. The illumination system according to claim 2, wherein the plurality of first small lenses of the first lens array each has a different optical axis position in a direction perpendicular to the prescribed direction so that a plurality of partial light beams entering the polarization conversion system are mutually adjacent in at least the direction perpendicular to the prescribed direction.

12. The illumination system according to claim 11, wherein a plurality of partial light beams arrayed in the prescribed direction are each reduced in the power variation optical relay system by a reduction ratio that differs according to an array position of each partial light beam.

13. The illumination system according to claim 2, wherein the relay lenses are constituted by a composite lens comprising at least two lenses.

14. A projector for displaying projected images, comprising:

an illumination system according to any one of claims 1 to 13,

an electro-optical device that converts light received from the illumination system to light for forming images responsive to image signals and emits the light thus converted, and

a projection optical system that projects light emitted from the electro-optical device.

15. The projector according to claim 14, further comprising:

a color separator that separates light emitted from the illumination system into a plurality of color components,

a plurality of the electro-optical devices for separately receiving each of the color components separated by the color separator, and

a color combiner for combining light of each color component emitted by the plurality of electro-optical devices,

wherein the projection optical system projects the combined light emerging from the color combiner.

16. The projector according to claim 15,

wherein, assuming x, y, z as three mutually orthogonal directional axes where z is a direction parallel to an optical axis of light emerging from the illumination system, the color separator has a color separation surface plane that is substantially perpendicular to plane xz and is inclined by a prescribed angle with respect to plane yz, and

the illumination system is positioned so that the prescribed direction in which a plurality of pairs of polarization splitting film and reflecting film included in the polarization conversion system are arrayed is substantially identical to the y direction.

17. The projector according to claim 15,

wherein, assuming x, y, z as three mutually orthogonal directional axes where z is a direction parallel to an optical axis of light emerging from the illumination system, the color combiner has a color combining surface plane that is substantially perpendicular to plane xz and is inclined by a prescribed angle with respect to plane yz, and

the illumination system is positioned so that the prescribed direction in which the plurality of pairs of polarization splitting film and reflecting film are arrayed is substantially identical to direction y.

18. A projector for displaying projected images, comprising:

an illumination system according to any one of claims 1 to 13,

a reflecting type electro-optical device that converts incident light to light for forming images responsive to received image signals while reflecting the light,

a projection optical system that projects light emitted from the reflecting type electro-optical device, and

a polarization splitting device that directs first linearly polarized light received from the illumination system toward the reflecting type electro-optical device and also directs toward the projection optical system second linearly polarized light that is received from the reflecting type electro-optical device and that is polarized in a direction perpendicular to the first linearly polarized light.

19. The projector according to claim 18,

wherein, assuming x, y, z as three mutually orthogonal directional axes where z is a direction parallel to an optical axis of light emerging from the illumination system, the polarization beam splitter element has a polarized light separation surface plane that is substantially perpendicular to plane xz and is inclined by a prescribed angle with respect to plane yz, and

the illumination system is positioned so that the prescribed direction in which a plurality of sets of polarization splitting film and reflecting film included in the polarization conversion system are arrayed is substantially identical to the x direction.

20. A projector for displaying projected images, comprising:

an illumination system according to any one of claims 1 to 13,

an electro-optical device that includes a plurality of pixels each including a plurality of sub-pixels corresponding to light of each of a plurality of colors and a condenser optical system comprising a plurality of small condenser lenses corresponding to each pixel, the electro-optical device converting light transmitted by each pixel to light for forming image of each pixel responsive to given image information,

a color separator that separates light emerging from the illumination system into a plurality of color components and also directs light of each of the plurality of color components in a mutually different direction to impinge on the sub-pixels corresponding to the respective color components, and

a projection optical system for projecting light emitted from the electro-optical device.

21. The projector according to claim 20,

wherein, assuming x, y, z as three mutually orthogonal directional axes where z is a direction parallel to an optical axis of light emerging from the illumination system, the color separator has a plurality of color separation surface planes for selectively separating light into a plurality of color components that is substantially perpendicular to plane xz and is inclined by a different prescribed angle with respect to plane yz, and

the illumination system is positioned so that the prescribed direction in which a plurality of pairs of polarization splitting film and reflecting film included in the polarization conversion system are arrayed is substantially identical to the y direction.

22. The projector according to claim 20, wherein the illumination system is positioned so that the prescribed direction in which a plurality of pairs of polarization splitting film and reflecting film are arrayed is substantially identical to a direction that is perpendicular to a direction in which the plurality of sub-pixels of each pixel are aligned.