Enhanced effective refractive index total internal reflection image display

• US 6,304,365 B1
• Filed: 06/02/2000
• Issued: 10/16/2001
• Est. Priority Date: 06/02/2000
• Status: Expired due to Term

• Current Assignee: Concord HK International Education Limited
• Original Assignee: University of British Columbia
• Inventors: Whitehead, Lorne A.
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Lucas, Michael A.
• Application Number:
  US09/585,552
• Time in Patent Office: 501 Days
• Field of Search: 359/296, 359/228, 359/222, 359/263, 359/618, 359/619, 359/621, 359/291
• US Class Current: 359/296
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/195 by using frustrated reflection digital reflection using controlled total internal reflection G02F1/315
• CPC Class Codes: G02F 2203/026 attenuated or frustrated internal reflection

Abstract

The invention provides an image display for viewing images in a preferred viewing direction. The display has parallel, macroscopically planar, structured surface, non-light absorptive light deflecting and reflecting portions which are longitudinally symmetrical in mutually perpendicular directions, both of which are perpendicular to the preferred viewing direction. A liquid containing a plurality of movable members contacts the light reflecting portion. A controller applies an electromagnetic force to selectively move the members into an evanescent wave region adjacent the light reflecting portion to frustrate TIR of light rays at selected points on the light reflecting portion. The structured surfaces on the light deflecting portion deflect light rays incident in the preferred viewing direction toward the light reflecting portion by imparting to the rays a directional component in the direction of longitudinal symmetry of the light reflecting portion. The structured surfaces on the light reflecting portion totally internally reflect the deflected light rays toward the light deflecting portion at points other than the selected points at which TIR is frustrated. Then, the structured surfaces on the light deflecting portion again deflect the totally internally reflected light rays, cancelling the directional component therefrom, such that the deflected totally internally reflected light rays emerge from the display in a direction substantially parallel to the preferred viewing direction.

Claims

1. An image display having a preferred viewing direction, said image display comprising:

(a) a substantially macroscopically planar light deflecting portion having longitudinal symmetry in a first direction substantially perpendicular to said preferred viewing direction;

(b) a substantially macroscopically planar light reflecting portion having longitudinal symmetry in a second direction substantially perpendicular to said first direction and substantially perpendicular to said preferred viewing direction, said light reflecting portion substantially parallel to said light deflecting portion;

(c) a liquid contacting said light reflecting portion;

(d) a plurality of movable members in said liquid;

(e) a controller for applying an electromagnetic force to said members to selectively move said members into an evanescent wave region adjacent said light reflecting portion to frustrate total internal reflection of light rays at selected points on said light reflecting portion;

wherein;

(i) said light deflecting portion is substantially non-light absorptive and has structured surfaces which deflect light rays incident upon said display in said preferred viewing direction toward said light reflecting portion by imparting to said incident light rays a directional component in said second direction;

(ii) said light reflecting portion is substantially non-light absorptive and has structured surfaces which totally internally reflect said deflected light rays toward said light deflecting portion at points other than said selected points; and

,

(iii) said light deflecting portion structured surfaces deflect said totally internally reflected light rays by cancelling said directional component from said totally internally reflected light rays, such that said deflected totally internally reflected light rays emerge from said image display in a direction substantially parallel to said preferred viewing direction.

2. An image display as defined in claim 1, wherein:

(a) said structured surfaces are prismatic surfaces;

(b) said light deflecting portion further comprises an outward sheet surface bearing a first plurality of prisms extending parallel to one another; and

,

(c) said light reflecting portion further comprises an inward surface of said sheet bearing a second plurality of prisms extending parallel to one another and extending substantially perpendicular to said first plurality of prisms.

3. An image display as defined in claim 2, wherein said sheet is formed of a material having a refractive index greater than about 1.65.

4. An image display as defined in claim 3, wherein said liquid is an electrophoretic medium having a refractive index of about 1.27.

5. An image display as defined in claim 3, wherein said liquid is Fluorinert™

Electronic Liquid and said movable members are particles suspended in said liquid.

6. An image display device as defined in claim 3, wherein said movable members are particles having a particle diameter less than or equal to about one micron.

7. An image display device as defined in claim 3, wherein said movable members are particles having a particle diameter of about 100 nm.

8. An image display as defined in claim 2, wherein said sheet is formed of a composite polymer material having a refractive index of about 1.73.

9. An image display as defined in claim 8, wherein said liquid is an electrophoretic medium having a refractive index of about 1.27 and said movable members are particles suspended in said electrophoretic medium.

10. An image display as defined in claim 8, wherein said liquid is Fluorinert™

Electronic Liquid and said movable members are particles suspended in said liquid.

11. An image display device as defined in claim 8, wherein said movable members are particles having a particle diameter less than or equal to about one micron.

12. An image display device as defined in claim 8, wherein said movable members are particles having a particle diameter of about 100 nm.

13. An image display as defined in claim 2, wherein said first plurality of prisms are 60°

angle isosceles prisms and said second plurality of prisms are right angle isosceles prisms.

14. An image display as defined in claim 1, wherein:

(a) said structured surfaces are prismatic surfaces;

(b) said light deflecting portion further comprises;

(i) a first sheet having an outward surface bearing a first plurality of prisms extending parallel to one another and having an opposed flat inward surface;

(ii) an outward surface of a second sheet substantially parallel to said first sheet, said second sheet outward surface bearing a second plurality of prisms extending parallel to one another and extending parallel to said first plurality of prisms;

(iii) an air gap between said first and second sheets; and

,

(c) said light reflecting portion further comprises a third plurality of prisms on an inward surface of said second sheet, said third plurality of prisms extending parallel to one another and extending substantially perpendicular to said first and said second pluralities of prisms.

15. An image display as defined in claim 14, wherein said sheets are formed of a material having a refractive index greater than or equal to about 1.6.

16. An image display as defined in claim 15, wherein said liquid is an electrophoretic medium having a refractive index of about 1.27 and said movable members are particles suspended in said electrophoretic medium.

17. An image display device as defined in claim 15, wherein said movable members are particles having a particle diameter less than or equal to about one micron.

18. An image display device as defined in claim 15, wherein said movable members are particles having a particle diameter of about 100 nm.

19. An image display as defined in claim 15, wherein said liquid is Fluorinert™

Electronic Liquid and said movable members are particles suspended in said liquid.

20. An image display as defined in claim 14, wherein:

(a) said first plurality of prisms are isosceles prisms with apices subtending an angle θ

which varies as a function of the refractive index of said first sheet; and

,

(b) said second and said third pluralities of prisms are right angle isosceles prisms.

21. An image display as defined in claim 1, wherein:

(a) said structured surfaces are prismatic surfaces;

(b) said light deflecting portion further comprises;

(i) a first sheet having a flat outward surface and having an opposed inward surface bearing a first plurality of prisms extending parallel to one another;

(ii) a flat outward surface of a second sheet substantially parallel to said first sheet;

(iii) a gap between said first and second sheets containing a low refractive index medium; and

,

(c) said light reflecting portion further comprises a second plurality of prisms on an inward surface of said second sheet, said second plurality of prisms extending parallel to one another and extending substantially perpendicular to said first plurality of prisms.

22. An image display as defined in claim 21, wherein said sheets are formed of a material having a refractive index greater than or equal to about 1.6.

23. An image display as defined in claim 22, wherein said liquid is an electrophoretic medium having a refractive index of about 1.27 and said movable members are particles suspended in said electrophoretic medium.

24. An image display device as defined in claim 22, wherein said movable members are particles having a particle diameter less than or equal to about one micron.

25. An image display device as defined in claim 23, wherein said movable members are particles having a particle diameter of about 100 nm.

26. An image display as defined in claim 23, wherein said liquid is Fluorinert™

Electronic Liquid and said movable members are particles suspended in said liquid.

27. An image display as defined in claim 21, wherein said first plurality of prisms are 60°

isosceles prisms and said second plurality of prisms are right angle isosceles prisms.

28. An image display as defined in claim 21, wherein said low refractive index medium has a refractive index of about 1.27.

29. An image display as defined in claim 21, wherein said low refractive index medium is Fluorinert™

Electronic Liquid.

30. An image display as defined in claim 1, wherein:

(a) said structured surfaces are prismatic surfaces;

(b) said light deflecting portion further comprises a first sheet having a flat outward surface and having an opposed inward surface bearing a first plurality of prisms extending parallel to one another;

(c) said light reflecting portion further comprises a second sheet having a flat inward surface substantially parallel to said first sheet and having an opposed outward surface bearing a second plurality of prisms extending parallel to one another and extending substantially perpendicular to said first plurality of prisms; and

,

(d) said light deflecting portion further comprises a gap between said first and second sheets containing a low refractive index medium.

31. An image display as defined in claim 30, wherein said sheets are formed of a material having a refractive index greater than or equal to about 1.6.

32. An image display as defined in claim 31, wherein said liquid is an electrophoretic medium having a refractive index of about 1.27 and said movable members are particles suspended in said electrophoretic medium.

33. An image display device as defined in claim 31, wherein said movable members are particles having a particle diameter less than or equal to about one micron.

34. An image display device as defined in claim 31, wherein said movable members are particle diameter of about 100 nm.

35. An image display as defined in claim 31, wherein said liquid is Fluorinert™

Electronic Liquid and said movable members are particles suspended in said liquid.

36. An image display as defined in claim 30, wherein said first and second pluralities of prisms are 60°

isosceles prisms.

37. An image display as defined in claim 30, wherein said low refractive index medium has a refractive index of about 1.27.

38. An image display as defined in claim 30, wherein said low refractive index medium is Fluorinert™

Electronic Liquid.

39. An image display as defined in claim 1, wherein said structured surfaces are trapezoidal surfaces.

40. An image display as defined in claim 1, wherein said structured surfaces parabolic surfaces.

41. An image display as defined in claim 1, wherein said light deflecting portion structured surfaces are prismatic surfaces rotated about an axis parallel to said second direction to offset said deflected light rays about 10°

-20°

relative to said preferred viewing direction.

42. An method of displaying images for viewing said images in a preferred viewing direction, said method characterized by:

(a) deflecting light rays incident in said preferred viewing direction through a longitudinally symmetrical deflector toward a longitudinally symmetrical reflector by imparting to said light rays a directional component in a direction of longitudinal symmetry of said reflector;

(b) frustrating total internal reflection of said deflected light rays at selected points on said reflector;

(c) totally internally reflecting said deflected light rays at points on said reflector other than said selected points;

(d) cancelling said directional component from said totally internally reflected light rays by deflecting said totally internally reflected rays through said deflector such that said deflected totally internally reflected light rays are substantially parallel to said preferred viewing direction;

wherein;

(i) said deflector has a direction of longitudinal symmetry substantially perpendicular to said direction of longitudinal symmetry of said reflector; and

,

(ii) said directions of longitudinal symmetry are substantially mutually perpendicular to said preferred viewing direction.

43. A method as defined in claim 42, wherein said frustrating total internal reflection further comprises electrophoretically moving a plurality of particles into an evanescent wave region adjacent said selected points on said reflector.