Image projection system with a polarizing beam splitter

• US 6,447,120 B2
• Filed: 05/21/2001
• Issued: 09/10/2002
• Est. Priority Date: 07/28/1999
• Status: Expired due to Term

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Gardner, Eric, Hansen, Douglas P., Perkins, Raymond T.
• Primary Examiner(s): Dowling, William
• Application Number:
  US09/862,183
• Publication Number:
  US 20020015135A1
• Time in Patent Office: 477 Days
• Field of Search: 353/20, 353/31, 353/33, 353/34, 353/37, 353/122, 349/5, 349/8, 349/9, 359/486
• US Class Current: 353/20
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/2073 Polarisers in the lamp house peculiar to electronic spatial light modulators H04N9/3197

Abstract

An image projection system has a wire grid polarizing beam splitter which functions as both the polarizer and the analyzer in the system. A light source produces a source light beam directed at the beam splitter which reflects one polarization and transmits the other. A liquid crystal array is disposed in either the reflected or transmitted beam. The array modulates the polarization of the beam, encoding image information thereon, and directs the modulated beam back to the beam splitter. The beam splitter again reflects one polarization and transmits the other so that the encoded image is either reflected or transmitted to a screen. The beam splitter can be an embedded wire grid polarizer with an array of parallel, elongated, spaced-apart elements sandwiched between first and second layers. The elements form a plurality of gaps between the elements which provide a refractive index less than the refractive index of the first or second layers.

Claims

1. An image projection system, comprising:

a) a light source capable of producing a visible light beam;

b) a polarizing beam splitter, located near the light source in the light beam and oriented at an angle with respect to the light beam, the beam splitter comprising;

1) a first transparent substrate having a first surface located in the light beam with the light beam striking the first surface at an angle, and having a refractive index;

2) a second layer, separate from the first transparent substrate, having a refractive index; and

3) a generally parallel arrangement of thin, elongated, spaced-apart elements disposed between the first transparent substrate and the second layer, and forming a plurality of gaps between the elements, the gaps providing a refractive index less than the refractive index of the first transparent substrate or the second layer, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

c) a reflective array located near the polarizing beam splitter in either the reflected or transmitted beam, the array modulating the polarization of the beam by selectively altering the polarization of the beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

d) the beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam, and the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam, to separate out the unaltered polarization from the modulated beam;

e) a screen located in either the second reflected beam or the second transmitted beam for displaying the encoded image information.

2. A system in accordance with claim 1, wherein the transparent substrate has a thickness less than approximately 5 millimeters.

3. A system in accordance with claim 1, wherein the transparent substrate has a flatness less than approximately 3 standard wavelengths deviation per inch.

4. A system in accordance with claim 1, wherein the first transmitted beam has a geometric distortion less than approximately 3 wavelengths deviation per inch.

5. A system in accordance with claim 1, wherein the gaps between the elements include air.

6. A system in accordance with claim 1, wherein the gaps between the elements have a vacuum.

7. A system in accordance with claim 1, wherein the gaps between the elements include a material different from materials of the first transparent substrate and the second layer.

8. A system in accordance with claim 1, wherein the gaps include a material that is a same material as the second layer.

9. A system in accordance with claim 1, wherein the gaps include a material that is a same material as the first transparent substrate.

10. A system in accordance with claim 1, wherein the gaps between the elements include water.

11. A system in accordance with claim 1, wherein the gaps between the elements include magnesium fluoride.

12. A system in accordance with claim 1, wherein the gaps between the elements include oil.

13. A system in accordance with claim 1, wherein the gaps between the elements include hydrocarbon compounds.

14. A system in accordance with claim 1, wherein the gaps between the elements include plastic.

15. A system in accordance with claim 1, wherein the gaps between the elements include fluorinated hydrocarbon.

16. A system in accordance with claim 1, wherein the arrangement has a configuration and the elements have a size which would normally create a resonance effect in combination with one of the layer or the substrate within the visible spectrum;

and wherein the gaps with a lower refractive index than the refractive index of one of the layer or the substrate causes a shift of the normally occurring resonance effect to a lower wavelength, thereby broadening a band of visible wavelengths in which no resonance effect occurs.

17. A system in accordance with claim 1, wherein the second layer includes a film.

18. A system in accordance with claim 1, wherein the second layer includes a plurality of films.

19. A system in accordance with claim 1, wherein the second layer includes a vacuum deposited film selected from the group consisting of:

silicon dioxide, silicon nitride, magnesium fluoride, and titanium oxide.

20. A system in accordance with claim 1, wherein the second layer includes a sheet of glass.

21. A system in accordance with claim 1, wherein the second layer includes a sheet of plastic.

22. A system in accordance with claim 1, wherein the second layer includes a film of hexamethal disilazane.

23. A system in accordance with claim 1, wherein the beam splitter is a generally planar sheet.

24. A system in accordance with claim 1, wherein the beam splitter is oriented with respect to the light beam or the modulated beam at an incident angle between approximately 0 to 80 degrees.

25. A system in accordance with claim 1, wherein the beam splitter is oriented with respect to the light beam or the modulated beam at incidence angles greater than 47 degrees or less than 43 degrees.

26. A system in accordance with claim 1, wherein the light beam has a useful divergent cone with a half angle between approximately 10 and 25°

.

27. A system in accordance with claim 1, wherein the beam splitter is used at an F-number less than approximately f/2.5.

28. A system in accordance with claim 1, wherein the beam splitter has a throughput of at least 50% defined by the product of the fractional amount of p-polarization transmitted light and the fractional amount of s-polarization reflected light;

and wherein the s-polarization transmitted light and p-polarization reflected light are both less than 5%.

29. A system in accordance with claim 1, wherein the beam splitter has a throughput of at least 50% defined by the product of the fractional amount of s-polarization transmitted light and the fractional amount of p-polarization reflected light;

and wherein the p-polarization transmitted light and s-polarization reflected light are both less than 5%.

30. A system in accordance with claim 1, wherein the beam splitter has a throughput for the light beam of at least 65%, defined by the product of the fractional amount of reflected light and the fractional amount of transmitted light;

and wherein the percent of reflected light or the percent of transmitted light is greater than approximately 67%.

31. A system in accordance with claim 1, further comprising a pre-polarizer disposed between the light source and the beam splitter.

32. A system in accordance with claim 1, further comprising a post-polarizer disposed between the beam splitter and the screen.

33. A system in accordance with claim 1, wherein the array is disposed in the reflected beam;

and wherein the screen is disposed in the second transmitted beam.

34. A system in accordance with claim 1, wherein the array is disposed in the transmitted beam;

and wherein the screen is disposed in the second reflected beam.

35. A system in accordance with claim 1, wherein

a) the arrangement of elements has a period less than approximately 0.21 microns,

b) the elements have a thickness between approximately 0.04 to 0.5 microns, and

c) the elements have a width of between approximately 30 to 76% of the period.

36. A system in accordance of claim 1, wherein the elements each have a cross section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form an angle with respect to the base greater than approximately 68 degrees.

37. A method for projecting an image, the method comprising:

a) producing a source light beam having a wavelength in a range between approximately 0.4 to 0.7 microns using a light source;

b) substantially separating polarizations of the source light beam using a polarizing beam splitter disposed in the source light beam, the polarizing beam splitter including;

1) a first layer having a refractive index;

2) a second layer, separate from the first layer, having a refractive index;

3) a generally parallel arrangement of thin, elongated, spaced-apart elements, disposed between the first and second layers, configured and sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization orientation that lies in the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

4) a plurality of gaps, formed between the elements and the first and second layers, configured to provide a refractive index less than the refractive index of the first or second layers;

c) modulating either the transmitted or reflected beam and creating a modulated beam by selectively altering the polarization of the beam using an array disposed in either the transmitted or reflected beam;

d) substantially separating the polarizations of the modulated beam using the polarizing beam splitter disposed in the modulated beam, the elements interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization orientation that lies in the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam; and

e) displaying either the second transmitted beam or the second reflected beam on a screen.

38. An image display system for producing a visible image, the system comprising:

a) a light source configured to emit a source light beam having a wavelength in a range between approximately 0.4 to 0.7 microns;

b) a liquid crystal array positioned and oriented to receive and modulate at least a portion of the source light beam to create a modulated beam containing image information;

c) a screen positioned and oriented to receive and display at least a portion of the modulated beam; and

d) a polarizing beam splitter positioned and oriented to receive both the source light beam and the modulated beam, the polarizing beam splitter including;

1) a first layer having a refractive index;

2) a second layer, separate from the first layer, having a refractive index;

3) a generally parallel arrangement of thin, elongated, spaced-apart elements, disposed between the first and second layers, configured and sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization orientation that lies in the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam, and interacts with the electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the modulated light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization orientation that lies in the plane that includes at least one of the elements and the direction of the modulated light beam, defining a second reflected beam; and

4) a plurality of gaps, formed between the elements and the first and second layers, configured to provide a refractive index less than the refractive index of the first or second layers.

39. A system in accordance with claim 38, wherein the first layer is a substrate having a thickness less than approximately 5 millimeters.

40. A system in accordance with claim 38, wherein the first layer is a substrate having a flatness less than approximately 3 standard wavelengths deviation per inch.

41. A system in accordance with claim 38, wherein the either of the first or second transmitted beams has a geometric distortion less than approximately 3 wavelengths deviation per inch.

42. A system in accordance with claim 38, wherein the gaps between the elements include air.

43. A system in accordance with claim 38, wherein the gaps between the elements have a vacuum.

44. A system in accordance with claim 38, wherein the gaps between the elements include a material different from materials of the first transparent substrate and the second layer.

45. A system in accordance with claim 38, wherein the gaps include a material that is a same material as the second layer.

46. A system in accordance with claim 38, wherein the gaps include a material that is a same material as the first transparent substrate.

47. A system in accordance with claim 38, wherein the gaps between the elements include water.

48. A system in accordance with claim 38, wherein the gaps between the elements include magnesium fluoride.

49. A system in accordance with claim 38, wherein the gaps between the elements include oil.

50. A system in accordance with claim 38, wherein the gaps between the elements include hydrocarbon compounds.

51. A system in accordance with claim 38, wherein the gaps between the elements include plastic.

52. A system in accordance with claim 38, wherein the gaps between the elements include fluorinated hydrocarbon.

53. A system in accordance with claim 38, wherein the arrangement has a configuration and the elements have a size which would normally create a resonance effect in combination with one of the layers within the visible spectrum;

and wherein the gaps with a lower refractive index than the refractive index of one of the layers causes a shift of the normally occurring resonance effect to a lower wavelength, thereby broadening a band of visible wavelengths in which no resonance effect occurs.

54. A system in accordance with claim 38, wherein the second layer includes a film.

55. A system in accordance with claim 38, wherein the second layer includes a plurality of films.

56. A system in accordance with claim 38, wherein the second layer includes a vacuum deposited film selected from the group consisting of:

silicon dioxide, silicon nitride, magnesium fluoride, and titanium oxide.

57. A system in accordance with claim 38, wherein the second layer includes a sheet of glass.

58. A system in accordance with claim 38, wherein the second layer includes a sheet of plastic.

59. A system in accordance with claim 38, wherein the second layer includes a film of hexamethal disilazane.

60. A system in accordance with claim 38, wherein

a) the arrangement of elements has a period less than approximately 0.21 microns,

b) the elements have a thickness between approximately 0.04 to 0.5 microns, and

c) the elements have a width of between approximately 30 to 76% of the period.

61. A system in accordance with claim 38, wherein the array is disposed in the reflected beam, and wherein the screen is disposed in the second transmitted beam.

62. A system in accordance with claim 38, wherein the array is disposed in the transmitted beam, and wherein the screen is disposed in the second reflected beam.

63. An image projection system, comprising:

a) a light source producing a visible light beam;

b) a polarizing beam splitter located near the light source in the light beam and oriented at an angle with respect to the light beam, the beam splitter comprising;

1) a first transparent substrate having a first surface located in the light beam with the light beam striking the first surface at an angle;

2) the first transparent substrate having a thickness less than approximately 5 millimeters; and

3) a generally parallel arrangement of thin, elongated, spaced-apart elements, disposed on the first transparent substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

c) a reflective array located near the polarizing beam splitter in either the reflected or transmitted beam, the array modulating the polarization of the beam by selectively altering the polarization of the beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

d) the beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam, and the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam, to separate out the unaltered polarization from the modulated beam; and

e) a screen located in either the second reflected beam or the second transmitted beam for displaying the encoded image information.

64. A system in accordance with claim 63, further comprising:

a) second layer, separate from the first transparent substrate; and

b) the arrangement of elements being disposed between the first transparent substrate and the second layer; and

c) a plurality of gaps formed between the elements; and

d) the gaps providing a refractive index less than a refractive index of the first transparent substrate or the second layer.

65. A system in accordance with claim 63, wherein the first transparent substrate having a flatness less than approximately 3 standard wavelengths deviation per inch.

66. A system in accordance with claim 63, wherein either the first or second transmitted beams have a geometric distortion less than approximately 3 wavelengths deviation per inch.

67. An image projection system, comprising:

a) a light source producing a visible light beam;

b) a polarizing beam splitter located near the light source in the light beam and oriented at an angle with respect to the light beam, the beam splitter comprising;

1) a first transparent substrate having a first surface located in the light beam with the light beam striking the first surface at an angle;

2) the first transparent substrate having a flatness less than approximately 3 standard wavelengths deviation per inch; and

3) a generally parallel arrangement of thin, elongated, spaced-apart elements, disposed on the first transparent substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

c) a reflective array located near the polarizing beam splitter in either the reflected or transmitted beam, the array modulating the polarization of the beam by selectively altering the polarization of the beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

d) the beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam, and the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam, to separate out the unaltered polarization from the modulated beam; and

e) a screen located in either the second reflected beam or the second transmitted beam for displaying the encoded image information.

68. A system in accordance with claim 67, further comprising:

a) a second layer, separate from the first transparent substrate; and

b) the arrangement of elements being disposed between the first transparent substrate and the second layer; and

c) a plurality of gaps formed between the elements; and

d) the gaps providing a refractive index less than a refractive index of the first transparent substrate or the second layer.

69. A system in accordance with claim 67, wherein the first transparent substrate has a thickness less than approximately 5 millimeters.

70. A system in accordance with claim 67, wherein either the first or second transmitted beams have a geometric distortion less than approximately 3 wavelengths deviation per inch.

71. An image projection system, comprising:

a) a light source producing a visible light beam;

b) a polarizing beam splitter located near the light source in the light beam and oriented at an angle with respect to the light beam, the beam splitter comprising;

1) a first transparent substrate having a first surface located in the light beam with the light beam striking the first surface at an angle; and

2) a generally parallel arrangement of thin, elongated, spaced-apart elements, disposed on the first transparent substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

c) a reflective array located near the polarizing beam splitter in either the reflected or transmitted beam, the array modulating the polarization of the beam by selectively altering the polarization of the beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

d) the beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam, and the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam, to separate out the unaltered polarization from the modulated beam; and

e) a screen located in either the second reflected beam or the second transmitted beam for displaying the encoded image information; and

f) the first and second transmitted beams having a geometric distortion less than approximately 3 wavelengths deviation per inch.

72. A system in accordance with claim 71, further comprising:

a) a second layer, separate from the first transparent substrate; and

b) the arrangement of elements being disposed between the first transparent substrate and the second layer; and

c) a plurality of gaps formed between the elements; and

d) the gaps providing a refractive index less than a refractive index of the first transparent substrate or the second layer.

73. A system in accordance with claim 71, wherein the first transparent substrate has a thickness less than approximately 5 millimeters.

74. A system in accordance with claim 71, wherein the first transparent substrate having a flatness less than approximately 3 standard wavelengths deviation per inch.