Image projection apparatus

• US 5,184,248 A
• Filed: 09/24/1991
• Issued: 02/02/1993
• Est. Priority Date: 07/16/1990
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: de Vaan, Adrianus J. S. M., van den Brandt, Adrianus H. J.
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): Wise, Robert E.
• Application Number:
  US07/764,667
• Time in Patent Office: 497 Days
• Field of Search: 359/483, 359/494, 359/495, 359/496, 353/33, 353/34, 353/81, 353/82
• US Class Current: 359/487.04
• CPC Class Codes: G02B 27/283 used for beam splitting or combining

Abstract

An image projection apparatus is described, which comprises an illumination system (100, 101, 54, 57, 62) having a first, round lens plate (54) and a second, half-round lens plate (57). A combination of a special polarization-sensitive beam splitter (20) and a polarization rotator (31) is arranged in the path of the beam supplied by this system and converts the beam into two sub-beams having the same state of polarization which jointly illuminate a display panel (1) in a uniform manner and optimally fill the surface area of this panel and a subsequent projection lens system (C).

Claims

1. An image projection apparatus comprising an illumination system, an image display system having at least one display panel for generating an image to be projected, in which the direction of polarization of an illumination beam supplied by the illumination system is modulated with the image information, a projection lens system for projecting the image formed by the image display system on a projection screen and a polarization-sensitive beam splitter arranged between the illumination system and the image display system for splitting the illumination beam into two differently polarized sub-beams the first of which is directly suitable to be modulated by the image display system and a polarization-rotating element for converting the second sub-beam into a beam having the same state of polarization as the first sub-beam, said first and second sub-beams being incident on the image display system, characterized in that the polarization-sensitive beam splitter comprises an oriented layer of birefringent material, in that the illumination beam directed towards the beam splitter has a semi-circular cross-section in a plane proximate to the beam splitter, in that the sub-beams traverse the same optical path length through the beam splitter and in that the sub-beams exiting from the combination of beam splitter and polarization-rotating element have a semi-circular cross-section and both fit within a circle.

2. An image projection apparatus as claimed in claim 1, characterized in that the beam splitter comprises a first prism having a first face which is parallel to the chief ray of the illumination beam incident on the beam splitter and a second prism having a first face which is parallel to the chief ray, which prisms have the same refractive index, in that the layer of birefringent material is located between the first faces of the prisms, while one of the refractive indices of said material is substantially equal to that of the prisms, in that a second and a third face of the first prism, which faces extend at equally large but opposite angles to the first face, constitute the entrance face and a first exit face, respectively, of the beam splitter, and in that a second face of the second prism, which face is parallel to the second face of the first prism, constitutes a second exit face of the beam splitter.

3. An image projection apparatus as claimed in claim 2, in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

4. An image projection apparatus as claimed in claim 2, characterized in that the polarization-rotating element is arranged on one of the exit faces of the beam splitter.

5. An image projection apparatus as claimed in claim 4, characterized in that the birefringent material is a liquid crystalline material.

6. An image projection apparatus as claimed in claim 4, characterized in that the layer of birefringent material is a birefringent adhesive layer.

7. An image projection apparatus as claimed in claim 4, in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

8. An image projection apparatus as claimed in claim 2, characterized in that the birefringent material is a liquid crystalline material.

9. An image projection apparatus as claimed in claim 8 in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

10. An image projection apparatus as claimed in claim 2 or 4, characterized in that the layer of birefringent material is a birefringent adhesive layer.

11. An image projection apparatus as claimed in claim 10 in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

12. An image projection apparatus as claimed in claim 10, characterized in that the adhesive layer is a uniaxially oriented polymer layer.

13. An image projection apparatus as claimed in claim 12, in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

14. An image projection apparatus as claimed in claim 12, characterized in that the polymer layer is formed from a cured liquid crystalline monomer composition.

15. An image projection apparatus as claimed in claim 14, in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

16. An image projection apparatus as claimed in claim 1, characterized in that the beam splitter comprises a layer of cholesteric material arranged at an angle of approximately 45°

to the principal axis, which layer splits the illumination beam into a first, reflected sub-beam of circularly polarized light having a first direction of rotation and into a second, on-going sub-beam of circularly polarized light having a second, opposite direction of rotation, and is further provided with a first reflector arranged in the path of the first sub-beam and being parallel to the chief ray of the illumination beam incident on the beam splitter, and with a second reflector arranged in the path of the second sub-beam at an angle of approximately 90°

to the cholesteric layer, and in that one of the reflectors reverses the direction of rotation of the sub-beam incident thereon.

17. An image projection apparatus as claimed in claim 16, in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

18. An image projection apparatus as claimed in claim 1, in which the illumination system comprises a radiation source, a concave reflector for concentrating light from the source and a lens system arranged in the path of the concentrated light, characterized in that the lens system successively comprises a first lens plate provided with a plurality of first lenses which, in a plane perpendicular to the principal axis, have a uniform width in a first direction and a uniform height in a second direction perpendicular to the first direction, a second lens plate provided with a plurality of second lenses whose number is proportional to the number of first lenses, and a third lens, the first lens plate dividing a radiation beam incident thereon into a number of sub-beams proportional to the number of second lenses, which sub-beams have their smallest constriction in the plane of the second lenses and whose chief rays are directed towards the centers of the second lenses, the second lenses imaging the radiation spots formed on the first lens plate in a superimposed form in an intermediate image and the third lens forming an image of the second lens plate in a plane proximate to the exit face of the beam splitter, in that the width/height ratio of the first lenses corresponds to that of a display panel and in that the second lenses are arranged within a half circle.

19. An image projection apparatus as claimed in claim 18, characterized in that at least one of the lenses of at least one of the lens plates is aspherical.

20. An image projection apparatus as claimed in claim 19, characterized in that the number of first lenses is equal to the number of second lenses.

21. An image projection apparatus as claimed in claim 19, characterized in that the first lenses have such a size and are arranged in such a way that the surface of the first lens plate is approximately equal to the cross-section of the illumination beam incident thereon.

22. An image projection apparatus as claimed in claim 19, characterized in that the first lens plate is arranged in a plane in which a first image of the light source is formed and in that said image is reimaged in an intermediate image by the second lens plate.

23. An image projection apparatus as claimed in claim 19, characterized in that a reduced image of the light source is formed on each one of the second lenses.

24. An image projection apparatus as claimed in claim 19, characterized in that the first lens plate, together with an associated lens, is integrated in one optical element having at least one curved surface.

25. An image projection apparatus as claimed in claim 18, characterized in that the number of first lenses is equal to the number of second lenses.

26. An image projection apparatus as claimed in claim 25, characterized in that the first lenses have such a size and are arranged in such a way that the surface of the first lens plate is approximately equal to the cross-section of the illumination beam incident thereon.

27. An image projection apparatus as claimed in claim 25, characterized in that the first lens plate is arranged in a plane in which a first image of the light source is formed and in that said image is reimaged in an intermediate image by the second lens plate.

28. An image projection apparatus as claimed in claim 25, characterized in that a reduced image of the light source is formed on each one of the second lenses.

29. An image projection apparatus as claimed in claim 25, characterized in that the first lens plate, together with an associated lens, is integrated in one optical element having at least one curved surface.

30. An image projection apparatus as claimed in claim 18, characterized in that the first lenses have such a size and are arranged in such a way that the surface of the first lens plate is approximately equal to the cross-section of the illumination beam incident thereon.

31. An image projection apparatus as claimed in claim 30, characterized in that the first lens plate is arranged in a plane in which a first image of the light source is formed and in that said image is reimaged in an intermediate image by the second lens plate.

32. An image projection apparatus as claimed in claim 30, characterized in that a reduced image of the light source is formed on each one of the second lenses.

33. An image projection apparatus as claimed in claim 30, characterized in that the first lens plate, together with an associated lens, is integrated in one optical element having at least one curved surface.

34. An image projection apparatus as claimed in claim 18, characterized in that the first lens plate is arranged in a plane in which a first image of the light source is formed and in that said image is reimaged in an intermediate image by the second lens plate.

35. An image projection apparatus as claimed in claim 34, characterized in that the first lens plate, together with an associated lens, is integrated in one optical element having at least one curved surface.

36. An image projection apparatus as claimed in claim 18, characterized in that a reduced image of the light source is formed on each one of the second lenses.

37. An image projection apparatus as claimed in claim 36, characterized in that the first lens plate, together with an associated lens, is integrated in one optical element having at least one curved surface.

38. An image projection apparatus as claimed in claim 18, characterized in that the first lens plate, together with an associated lens, is integrated in one optical element having at least one curved surface.

39. An image projection apparatus as claimed in claim 38 in which the associated lens is planoconvex, characterized in that the first lenses are arranged on the flat refractive surface of the lens.

40. An image projection apparatus as claimed in claim 38, characterized in that the first lenses are arranged on a curved refractive surface of the lens.

41. An image projection apparatus as claimed in claim 38, characterized in that a curved refractive surface of the lens is replaced by a principally flat surface on which the first lenses are arranged each having a curvature which is related to the curvature, at the location of the relevant lens, of the original curved refractive surface.

42. An image projection apparatus as claimed in claim 18, characterized in that the reflector is a spherical reflector which only collects light emitted by the source at one side of the plane through the centre of the radiation source and perpendicular to the optical axis of the system, and in that a condensor lens system is arranged at the other side of said plane and in front of the first lens plate.

43. An image projection apparatus as claimed in claim 42, characterized in that each condensor lens system comprises at least one lens, at least one refractive surface of which is aspherical.

44. An image projection apparatus as claimed in claim 43, characterized in that the first lens plate is divided into two first plates which are arranged in the first and the second condensor lens system, respectively.

45. An image projection apparatus as claimed in claim 42, characterized in that each condensor lens system comprises a main condensor lens which is succeeded by at least one extra lens element.

46. An image projection apparatus as claimed in claim 45, characterized in that the first lens plate is divided into two first plates which are arranged in the first and the second condensor lens system, respectively.

47. An image projection apparatus as claimed in claim 18, characterized in that the reflector is a spherical reflector which only collects light emitted by the source at one side of the plane through the centre of the radiation source and perpendicular to optical axis of the system, and in that two condensor lens systems are arranged at the other side of said plane and in front of the first lens plate, each system capturing a different part of the light originating from the source and the reflector.

48. An image projection apparatus as claimed in claim 47, characterized in that each condensor lens system comprises at least one lens, at least one refractive surface of which is asperical.

49. An image projection apparatus as claimed in claim 47, characterized in that each condensor lens system comprises a main condensor lens which is succeeded by at least one extra lens element.

50. An image projection apparatus as claimed in claim 47, characterized in that the first lens plate is divided into two first plates which are arranged in the first and the second condensor lens system, respectively.

51. An image projection apparatus as claimed in claim 18, characterized in that the reflector is a parabolic reflector which surrounds the greater part of the light source.

52. An image projection apparatus as claimed in claim 51, in which the radiation source is elongate, characterized in that the longitudinal direction of the source is parallel to the principal axis.

53. An image projection apparatus as claimed in claim 18, characterized in that the reflector is an elliptic reflector which surrounds the greater part of the light source.

54. An image projection apparatus as claimed in claim 53, in which the radiation source is elongate, characterized in that the longitudinal direction of the source is parallel to the principal axis.

55. An image projection apparatus as claimed in claim 53, characterized in that a collimator lens is arranged between the reflector and the first lens plate.

56. An image projection apparatus as claimed in claim 55, in which the radiation source is elongate, characterized in that the longitudinal direction of the source is parallel to the principal axis.

57. An image projection apparatus as claimed in claim 18, characterized in that the reflector is a hyperbolic reflector.

58. An image projection apparatus as claimed in claim 57, in which the radiation source is elongate, characterized in that the longitudinal direction of the source is parallel to the principal axis.

59. An image projection apparatus as claimed in claim 57, characterized in that a collimator lens is arranged between the reflector and the first lens plate.

60. An image projection apparatus as claimed in claim 59, in which the radiation source is elongate, characterized in that the longitudinal direction of the source is parallel to the principal axis.

61. A colour image projection apparatus having three colour channels for the three primary colours red, green and blue, each colour channel comprising a separate display panel, characterized in that it comprises one image projection apparatus as claimed in claim 1 for supplying separate beams for the three colour channels via colour-splitting means.

62. A colour image projection apparatus having three colour channels for the three primary colours red, green and blue, each channel comprising a separate display panel, characterized in that each colour channel comprises a separate image projection apparatus as claimed in claim 1.