Projection display

• US 20050030490A1
• Filed: 05/28/2004
• Published: 02/10/2005
• Est. Priority Date: 08/30/2000
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Huibers, Andrew G.
• Granted Patent: US 7,300,162 B2
• Time in Patent Office: Days
• US Class Current: 353/99
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

In order to minimize light diffraction along the direction of switching and more particularly light diffraction into the acceptance cone of the collection optics, in the present invention, micromirrors are provided which are not rectangular. Also, in order to minimize the cost of the illumination optics and the size of the display unit of the present invention, the light source is placed orthogonal to the rows (or columns) of the array, and/or the light source is placed orthogonal to a side of the frame defining the active area of the array. The incident light beam, though orthogonal to the sides of the active area, is not however, orthogonal to any substantial portion of sides of the individual micromirrors in the array. Orthogonal sides cause incident light to diffract along the direction of micromirror switching, and result in light ‘leakage’ into the ‘on’ state even if the micromirror is in the ‘off’ state. This light diffraction decreases the contrast ratio of the micromirror. The micromirrors of the present invention result in an improved contrast ratio, and the arrangement of the light source to micromirror array in the present invention results in a more compact system. Another feature of the invention is the ability of the micromirrors to pivot in opposite direction to on and off positions (the on position directing light to collection optics), where the movement to the on position is greater than movement to the off position. A further feature of the invention is a package for the micromirror array, the package having a window that is not parallel to the substrate upon which the micromirrors are formed. One example of the invention includes all the above features.

Claims

1. A projection display, comprising:

a light source for providing light to an array of micromirrors;

an array of micromirrors, each micromirror having a shape defined by a plurality of micromirror sides;

wherein light from the light source is incident on the array of micromirrors during operation;

wherein the array has four sides and wherein there are no micromirror sides that are parallel to any array sides.

2. The projection display of claim 1, wherein no micromirror sides are parallel to the incident light beam when viewed from above the array.

3. The projection display of claim 1, wherein the incident light beam is incident orthogonally to a side of the array.

4. The projection display of claim 1, wherein the axis of rotation of the micromirrors is parallel to a side of the array.

5. The projection display of claim 1, wherein the micromirrors are square.

6. The projection display of claim 3, wherein the micromirrors are positioned on a lattice aligned at an angle to the X and Y axes of the array.

7. The projection display of claim 1, wherein the micromirrors comprise micromirror plates that are connected via hinges to a substrate, and wherein the substrate, micromirror plates and hinges are disposed in different planes.

8. The projection display of claim 7, wherein a first gap is defined between the hinge and the micromirror plate, and a second gap is defined between the micromirror plate and the substrate.

9. The projection display of claim 7, wherein a first gap is defined between the substrate and the hinge and a second gap is defined between the hinge and the micromirror plate.

10. The projection display off claim 1, wherein a gap between adjacent micromirrors is between 0.1 um and 10 um.

11. The projection display of claim 10, wherein the gap between adjacent micromirrors is around 0.7 um.

12. The projection display of claim 1, wherein the array of micromirrors is disposed in a package having a light transmissive window.

13. The projection display of claim 12, wherein a mask is provided as part of the package.

14. The projection display of claim 13, wherein the mask is formed on the package window and extends around a periphery of the micromirror array.

15. The projection display of claim 12, wherein a molecular scavenger is provided within the package.

16. The projection display of claim 12, wherein a getter is provided within the package.

17. The projection display of claim 12, wherein a source of stiction reducing agent is provided within the package.

18. The projection display of claim 1, which is a front screen projection TV.

19. The projection display of claim 1, which is a rear screen projection TV.

20. The projection display of claim 1, which is a computer monitor.

21. The projection display of claim 1, further comprising a color wheel.

22. The projection display of claim 1, wherein the light beam incident on the micromirror array is from 10 to 50 degrees from a line normal to the plane of the micromirrors.

23. The projection display of claim 1, wherein the micromirrors are capable of pulse width modulation to achieve a gray scale image.

24. The projection display of claim 1, wherein the micromirrors are digitally addressed.

25. The projection display of claim 1, wherein the micromirrors are disposed on a semiconductor substrate.

26. The projection display of claim 25, wherein the semiconductor substrate is a silicon substrate.

27. The projection display of claim 1, wherein the micromirrors are disposed on a light transmissive substrate.

28. The projection display of claim 27, wherein the light transmissive substrate is glass.

29. The projection display of claim 27, wherein the light transmissive substrate is quartz or sapphire.

30. The projection display of claim 12, wherein the light transmissive window is glass.

31. The projection display of claim 12, wherein the light transmissive window is quartz.

33. The projection display of claim 12, wherein the light transmissive window is display quality glass.

34. The projection display of claim 1, wherein the micromirrors are capable of rotating at least +12 degrees to the ON position.

35. The projection display of claim 1, wherein an ON position of the micromirrors is from 10 to 15 degrees from a non-deflected position.

36. The projection display of claim 1, wherein the light source is an arc lamp.

37. The projection display of claim 1, wherein the ON and OFF positions of the micromirrors are defined by structure against which the micromirrors impinge.

38. The projection display of claim 1, further comprising a screen upon which the pattern of ON and OFF mirrors is incident.

39. The projection display of claim 1, further comprising a color filter for providing a series of sequential colors onto the micromirror array.

40. The projection display of claim 1, further comprising a device for improving the evenness of light distribution onto the micromirror array.

41. The projection display of claim 1, further comprising collection optics including a plurality of lenses disposed so as to project the pattern of light from the micromirror array onto a target.

42. The projection display of claim 1, further comprising one or more micromirrors or lenses for directing and focusing a cone of light onto the micromirror array.

43. The projection display of claim 1, further comprising a color wheel, a light pipe and a screen.

44. The projection display of claim 1, wherein the ON and OFF positions of the micromirrors are defined by the micromirrors abutting one and/or a second substrate or structure thereon.

45. The projection display of claim 1, wherein the micromirrors are formed on a substrate adjacent circuitry and electrodes, at least two electrodes are disposed adjacent each micromirror, one electrode for electrostatically pulling the adjacent micromirror to an off position, and another electrode for electrostatically pulling the adjacent micromirror to an on position.

46. The projection display of claim 1, wherein the circuitry and electrodes are formed on the same substrate as the micromirrors.

47. The projection display of claim 1, wherein the circuitry and electrodes are formed on a second substrate that is bonded to said substrate.

48. The projection display of claim 1, further comprising additional electrodes for stopping movement of the adjacent micromirror when the micromirror arrives at the on or off position.

49. The projection display of claim 48, wherein the additional electrodes are at the same potential as the adjacent micromirror.

50. The projection display of claim 1, wherein the micromirrors comprise metal and a dielectric material.

51. The projection display of claim 50, wherein the dielectric material is a nitride, carbide or oxide of silicon.

52. The projection display of claim 1, wherein the package is a hermetic package.

53. The projection display of claim 1, wherein the package is a partially hermetic package.

54. The projection display of claim 1 wherein the micromirror array is disposed in a package and comprises circuitry and electrodes on a semiconductor substrate, and bond wires for electrically connecting the substrate to the package.

55. The projection display of claim 1, wherein hinges of the micromirrors extend perpendicularly to the direction of the incident light beam.

56. The projection display of claim 1, wherein hinges of the micromirrors extend parallel to leading and trailing sides of the micromirror array.

57. The projection display of claim 1, wherein hinges of the micromirrors allow for an axis of rotation of the micromirrors that is perpendicular to the direction of the incident light beam.

58. The projection display of claim 1, wherein when viewed from above the micromirror array, a line defining the light beam incident on the micromirror array is not parallel to any sides of the micromirrors.

59. The projection display of claim 1, wherein at least 1000 micromirrors are in the micromirror array.

60. The projection display of claim 1, wherein the micromirrors have four predominant sides.

61. The projection display of claim 1, wherein the micromirrors are L-shaped.

62. The projection display of claim 1, wherein the sides of the micromirrors are of equal lengths.

63. The projection display of claim 1 ,wherein the micromirrors are in the shape of a trapezoid.

64. The projection display of claim 1, wherein the micromirrors are tiled together.

65. The projection display of claim 1, wherein the four sided array is rectangular and wherein light from the light source in the form of a beam of light is directed to the leading side of the rectangular array at an angle of 90 degrees plus or minus 40 degrees.

66. The projection display of claim 1, wherein the micromirror comprises a reflective material selected from gold or titanium.

67. The projection display of claim 1, wherein the micromirror comprises a reflective material that comprises aluminum.

68. The projection display of claim 1, wherein the micromirror comprises a reflective material that comprises silver.

69. The projection display of claim 1, wherein the OFF state of the micromirrors is at an angle less than the opposite angle of the micromirrors in the ON state.

70. The projection display of claim 1, wherein light is incident on the micromirrors where the beam of light is not orthogonal to any sides of the micromirrors and is orthogonal to the leading and trailing sides of the array.

71. The projection display off claim 70, wherein the beam of light is orthogonal to the axis of rotation of the micromirrors.

72. The projection display of claim 1, wherein millions of micromirrors are provided.

73. The projection display of claim 1, wherein each micromirror has a switching axis substantially parallel to at least one side of the array.

74. The projection display of claim 73, wherein each micromirror has a switching axis that is at an angle of from 35 to 60 degrees to all sides of the micromirror.

75. The projection display of claim 1, wherein the light beam is not incident orthogonally to any sides of the micromirrors.

76. The projection display of claim 1, wherein each micromirror comprises a hinge and micromirror plate that are disposed in different planes, and wherein the hinge has a width of from 0.1 to 10 um.

77. The projection display of claim 76, wherein the thickness of the micromirror plate is from 200 to 7300 angstroms.

78. The projection display of claim 1, wherein the micromirrors have a single point on the leading edge upon which light is incident.

79. The projection display of claim 1, wherein the micromirrors are formed on the same substrate as the micromirror actuation circuitry and electrodes.

80. The projection display of claim 1, wherein both the ON and OFF states of the micromirrors are in a position other than a flat non-deflected state.

81. The projection display of claim 1, wherein the micromirrors are connected via underlying hinges to a substrate by means of an electrically conductive material.

82. The projection display of claim 81, wherein the electrically conductive material is aluminum, metal alloys or a conductive ceramic compound.

83. The projection display of claim 1, wherein each micromirror is provided with a first electrode for deflecting the micromirror in a one direction, a second electrode for deflecting the micromirror in a second direction, and a third electrode for stopping movement of the micromirror.

84. The projection display of claim 1, further comprising a light absorbing layer under the micromirrors to decrease light scatter through the gaps between the micromirrors.

85. The projection display of claim 1, wherein from 64,000 to 2,000,000 micromirrors are provided in the array.

86. The projection display of claim 1, further comprising a TIR prism.

87. The projection display of claim 1, further comprising a light pipe.

88. The projection display of claim 1, wherein from 2,000,000 to 3,000,000 micromirrors are provided in the array.

89. The projection display of claim 1, wherein sides of the micromirrors are disposed at an angle less than 80 degrees in relation to the incident light beam axis projected onto the micromirror plane.

90. The projection display of claim 89, wherein sides of the micromirrors are disposed at an angle of 55 degrees or less in relation to the incident light beam axis projected onto the micromirror plane.

91. The projection display of claim 90, wherein sides of the micromirrors are disposed at an angle of 45 degrees or less in relation to the incident light beam axis projected onto the micromirror plane.

92. The projection display of claim 90, wherein sides of the micromirrors are disposed at an angle of 40 degrees or less in relation to the incident light beam axis projected onto the micromirror plane.

93. The projection display of claim 1, wherein the micromirror array has an area of from 1 cm² to 1 in².

94. The projection display of claim 1, wherein the micromirror has a resolution of 1,920,000 or higher.

95. The projection display of claim 1, having HDTV format.

96. The projection display of claim 1, having QXGA format.

97. The projection display of claim 1, having UXGA format.

98. The projection display of claim 1, wherein there are no substantial micromirror sides that are perpendicular to any array sides.

99. The projection display of claim 1, wherein each micromirror has four substantially straight sides, none of which are parallel to leading or trailing sides of the array which is rectangular.

100. The projection display of claim 1, wherein the micromirrors have the shape of a convex polygon.

101. The projection display of claim 1, wherein the micromirrors have two polygon sides that form an angle therebetween of less than 90 degrees.

32. The projection display of claim 32, wherein the light transmissive window is a polymer.