Projection TV with improved micromirror array

• US 20040233392A1
• Filed: 05/28/2004
• Published: 11/25/2004
• 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 7,018,052 B2
• Time in Patent Office: Days
• US Class Current: 353/31
• 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 rear or front projection TV, comprising:

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

an array of micromirrors;

a screen on which an image to be viewed is displayed;

wherein light from the light source is incident on the array of micromirrors during operation and directed as a rectangular image to the screen;

wherein the micromirrors are capable of movement between an OFF state and an ON state by pulse width modulation to achieve a gray scale image on the screen; and

wherein each micromirror corresponds to a pixel in a viewed image on the screen; and

wherein the viewed image has four sides and wherein each micromirror forms a corresponding micromirror image on the screen that has a single convex protrusion in the direction of a side of the rectangular image on the screen and has no substantial sides parallel to said side of the rectangular image;

wherein a horizontal row of micromirrors extends corner to corner in the row parallel to a side of the rectangular image, and wherein vertical lines corresponding to addressing columns extend from each micromirror in the row and connect to every other row of micromirrors; and

wherein a vertical column of micromirrors extends corner to corner in the column parallel to a side of the rectangular image, and wherein horizontal lines corresponding to addressing rows extend from each micromirror in the column and connect to every other column of micromirrors.

2. the projection TV of claim 1, further comprising a color wheel.

3. The projection TV of claim 2, further comprising a light pipe.

4. The projection TV of claim 3, wherein the light source is an arc lamp.

5. The projection TV of claim 1, which is a rear projection TV.

6. The projection TV of claim 4, which is a front projection TV.

7. The projection TV of claim 5, wherein no micromirror sides are parallel to the incident light beam when viewed from above the array.

8. The projection TV of claim 4, wherein the incident light beam is incident orthogonally to a side of the array.

9. The projection TV of claim 5, wherein the micromirrors are positioned micromirror side to micromirror side on a lattice aligned at an angle to the X and Y axes of the array.

10. The projection TV of claim 5, 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.

11. The projection TV of claim 10, 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.

12. The projection TV of claim 10, 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.

13. The projection TV of claim 5, wherein the array of micromirrors is disposed in a package having a light transmissive window.

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

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

16. The projection TV of claim 13, wherein a molecular scavenger is provided within the package.

17. The projection TV of claim 13, wherein a getter is provided within the package.

18. The projection TV of claim 13, wherein a source of stiction reducing agent is provided within the package.

19. The projection TV of claim 5, 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.

20. The projection TV of claim 19, wherein the micromirrors are capable of rotating at least +12 degrees to the ON position.

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

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

23. The projection TV of claim 5, further comprising optics including a plurality of lenses disposed so as to project the pattern of light from the micromirror array onto the screen.

24. The projection TV of claim 5, further comprising one or more lenses for directing and focusing a cone of light onto the micromirror array.

25. The projection TV of claim 1, further comprising a color wheel, a light pipe and a TIR prism.

26. The projection TV of claim 1, wherein the micromirrors comprise metal and a dielectric material, wherein the dielectric material is a nitride, carbide or oxide of silicon.

27. The projection TV of claim 5, wherein the package is a hermetic package.

28. The projection TV of claim 4, wherein the package is a partially hermetic package.

29. The projection TV of claim 27, 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.

30. The projection TV of claim 4, wherein hinges of the micromirrors extend parallel to leading and trailing sides of the micromirror array.

31. The projection TV of claim 5, wherein at least 1000 micromirros are in the micromirror array.

32. The projection TV of claim 5, wherein the micromirrors are tiled together.

33. The projection TV of claim 32, 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.

34. The projection TV of claim 6, wherein millions of micromirrors are provided.

35. The projection TV of claim 3, wherein each micromirror has a switching axis substantially parallel to at least one side of the array.

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

37. The projection TV of claim 36, wherein the light beam is not incident orthogonally to any sides of the micromirrors.

38. The projection TV 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.

39. The projection TV of claim 1, wherein the thickness of the micromirror plate is from 200 to 7300 angstroms.

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

41. The projection TV of claim 4, wherein from 64,000 to 2,000,000 micromirrors are provided in the array.

42. The projection TV of claim 6, further comprising a TIR prism.

43. The projection TV of claim 34, wherein from 2,000,000 to 3,000,000 micromirror are provided in the array.

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

45. The projection TV of claim 3, wherein the micromirror has a resolution of 1,920,000 or higher.

46. The projection TV of claim 5 having HDTV format.

47. The projection TV of claim 5, having QXGA format.

48. The projection TV of claim 5, having UXGA format.

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