Composite electrophoretically-switchable retro-reflective image display

• US 6,452,734 B1
• Filed: 11/30/2001
• Issued: 09/17/2002
• Est. Priority Date: 11/30/2001
• Status: Active Grant

• Current Assignee: Concord HK International Education Limited
• Original Assignee: University of British Columbia
• Inventors: Whitehead, Lorne A., Mossman, Michele Ann
• Primary Examiner(s): SIKDER, MOHAMMAD YUNUS
• Application Number:
  US09/996,987
• Time in Patent Office: 291 Days
• Field of Search: 359/836, 359/837, 359/833, 359/834, 359/296, 359/228, 359/222, 359/263, 359/618, 359/619, 359/621, 359/291
• US Class Current: 359/836
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/12 Reflex reflectors
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1677 Structural association of cells with optical devices, e.g. reflectors or illuminating devices

Abstract

A light deflector/recombiner is longitudinally symmetrical with respect to an X axis perpendicular to a Z axis. An X and Z vector components inverter longitudinally symmetrical with respect to both the X axis and a Y axis perpendicular to the X and Z axes lies parallel to the deflector/recombiner. A Y vector component inverter longitudinally symmetrical with respect to the X axis lies parallel to and between the deflector/recombiner and the X and Z inverter. The Y inverter has many reflector elements. Light rays incident in the Z direction encounter an element only once during return passage between the deflector/recombiner and the X and Z inverter. The X and Z inverter directionally inverts the rays with respect to the X and Z axes and the reflector element directionally inverts them with respect to the Y axis, such that substantially all incident rays are retro-reflected with respect to the X, Y and Z axes.

Claims

1. A variable image display for retro-reflecting light with respect to mutually perpendicular X, Y and Z axes, said display having a preferred viewing direction parallel to said Z axis, said display comprising:

(a) a substantially macroscopically planar light deflecting/recombining transmitter sheet longitudinally symmetrical with respect to said X axis;

(b) a substantially macroscopically planar X and Z vector components inverting reflector sheet substantially parallel to said light deflecting/recombining transmitter sheet, said X and Z vector components inverting reflector sheet having longitudinal symmetry with respect to said Y axis;

(c) a substantially macroscopically planar Y vector component inverting transmitter sheet longitudinally symmetrical with respect to said X axis, said Y vector component inverting transmitter sheet substantially parallel to and positioned between said light deflecting/recombining transmitter sheet and said X and Z vector components inverting reflector sheet, said Y vector component inverting transmitter sheet further comprising a plurality of reflector elements, each one of said reflector elements having a surface normal substantially parallel to said Y axis, each one of said reflector elements having a height H, each adjacent pair of said reflector elements spaced apart by a separation distance D;

wherein;

(i) each one of said sheets has a macroscopic surface normal substantially parallel to said Z axis;

(ii) light rays incident on said light deflecting/recombining transmitter sheet at an angle α

<

25°

with respect to said Z axis are transmitted by said light deflecting/recombining transmitter sheet toward said Y vector component inverting transmitter sheet and said X and Z vector components inverting reflector sheet at an angle θ

with respect to said Z axis;

(iii) said light rays transmitted by said light deflecting/recombining transmitter sheet are reflected by said X and Z vector components inverting reflector sheet toward said Y vector component inverting transmitter sheet and said light deflecting/recombining transmitter sheet at said angle θ

with respect to said Z axis;

(iv) vector components of substantially all of said light rays reflected by said X and Z vector components inverting reflector sheet are directionally inverted by said X and Z vector components inverting reflector sheet with respect to said X and Z axes; and

,

(v) vector components of substantially all of said light rays transmitted by said light deflecting/recombining transmitter sheet and reflected by said X and Z vector components inverting reflector sheet are directionally inverted with respect to said Y axis by only one reflection at one of said reflector elements, return to said light deflecting/recombining transmitter sheet at said angle θ

with respect to said Z axis, and are transmitted by said light deflecting/recombining transmitter sheet toward said viewer substantially 180°

opposed to said incident light rays and at said angle α

with respect to said Z axis.

2. An image display as defined in claim 1, wherein said angle θ

is within the range of about 30°

to 60°

.

3. An image display as defined in claim 1, wherein said X and Z vector components inverting reflector sheet further comprises a light deflection-maintaining portion longitudinally symmetrical with respect to said X axis, and a light reflecting portion longitudinally symmetrical with respect to said Y axis.

4. An image display as defined in claim 1, wherein said reflector elements have an H:

D aspect ratio selected to maximize the number of said light rays transmitted by said light deflecting/recombining transmitter sheet and reflected by said X and Z vector components inverting reflector sheet which undergo said only one reflection at said one of said reflector elements.

5. An image display as defined in claim 4, wherein said light deflecting/recombining transmitter sheet further comprises a first plurality of prisms extending parallel to said X axis.

6. An image display as defined in claim 5, wherein said first plurality prisms are on an outward face of said light deflecting/recombining transmitter sheet.

7. An image display as defined in claim 5, wherein said first plurality prisms are on an inward face of said light deflecting/recombining transmitter sheet.

8. An image display as defined in claim 6, wherein said first plurality prisms are 60°

included angle isosceles prisms.

9. An image display as defined in claim 7, wherein said first plurality prisms are 60°

included angle isosceles prisms.

10. An image display as defined in claim 8, wherein said first plurality prisms are microstructures formed of a composite polymer sheet material having a refractive index of about 1.73.

11. An image display as defined in claim 9, wherein said first plurality prisms are microstructures formed of a composite polymer sheet material having a refractive index greater than or equal to about 1.59.

12. An image display as defined in claim 6, wherein said first plurality prisms are 70°

included angle isosceles prisms.

13. An image display as defined in claim 7, wherein said first plurality prisms are 70°

included angle isosceles prisms.

14. An image display as defined in claim 12, wherein said first plurality prisms are microstructures formed of a composite polymer sheet material having a refractive index of about 1.59.

15. An image display as defined in claim 13, wherein said first plurality prisms are microstructures formed of a composite polymer sheet material having a refractive index of about 1.59.

16. An image display as defined in claim 5, wherein said first plurality prisms are isosceles prisms with apices subtending an angle φ

which varies as a function of the refractive index of said light deflecting/recombining transmitter sheet.

17. An image display as defined in claim 5, wherein said X and Z vector components inverting reflector sheet light deflecting portion further comprises a second plurality of prisms extending parallel to said X axis, and said X and Z vector components inverting reflector sheet light reflecting portion further comprises a third plurality of prisms extending parallel to said Y axis.

18. An image display as defined in claim 17, wherein said second plurality prisms are microstructures formed on an outward face of said X and Z vector components inverting reflector sheet and said third plurality prisms are microstructures formed on an inward face of said X and Z vector components inverting reflector sheet.

19. An image display as defined in claim 18, wherein said second and third plurality prisms are right angle isosceles prisms.

20. An image display as defined in claim 4, wherein said reflector elements are microstructure ribs extending parallel to said X axis.

21. An image display as defined in claim 4, wherein said reflector elements are microstructure channels extending parallel to said X axis.

22. An image display as defined in claim 6, further comprising a reflective material extending along a thin longitudinal strip at an apex of and on one facet of substantially each one of said first plurality prisms.