Optical path element, optical switching element, spatial light modulator and image display apparatus

• US 20030016905A1
• Filed: 03/18/2002
• Published: 01/23/2003
• Est. Priority Date: 03/21/2001
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Tomono, Hidenori, Kawashima, Ikue, Kondoh, Hitoshi
• Granted Patent: US 6,707,514 B2
• Time in Patent Office: Days
• US Class Current: 385/18
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/315 based on the use of controlled internal reflection

Abstract

An optical switching element, comprising a light transmitting element, a reflection substrate, and index variable material. The light transmitting element has a first light incident surface, a second light incident surface not parallel to the first light incident surface, and a light outgoing surface. The reflection substrate is arranged opposite to the second light incident surface and has a reflection surface with an angle that is not parallel to the second light incident surface, wherein a reflected light passes through the light transmitting element and the reflection substrate and then is reflected by the reflection surface. The index variable material is sandwiched between the light transmitting element and the reflection substrate and has an index of refraction varied according to an external signal. By varying the index of refraction of the index variable material, an angle formed by the reflected light and a normal line of the light outgoing surface is changed such that the emitting direction of the reflected light is changed.

Claims

1. An optical switching element, comprising:

a first light transmitting element, having a first light incident surface, a second light incident surface that is not parallel to the first light incident surface, and a light outgoing surface;

a reflection substrate, arranged opposite to the second light incident surface of the first light transmitting element and having a first reflection surface with a predetermined angle that is not parallel to the second light incident surface, wherein a reflected light passes through the first light transmitting element and the reflection substrate and then is reflected by the first reflection surface of the reflection substrate; and

an index variable material, sandwiched between the first light transmitting element and the reflection substrate and having an index of refraction that is variable according to an external signal applied,

wherein by varying the index of refraction of the index variable material, an angle formed by the reflected light and a normal line of the light outgoing surface is changed such that an emitting direction of the reflected light is changed.

2. The optical switching element of claim 1, wherein the second light incident surface and the light outgoing surface of the first light transmitting element are not in parallel.

3. The optical switching element of claim 1, wherein the optical switching element is switched between a first state and a second state, wherein the first state satisfies sin φ

₁≧

n_a/n₁, and the second state satisfies sin φ

₁<

n_a/n₁, in which n₁ is the index of refraction of the first light transmitting element, n_a is an index of refraction of a material surrounding the first light transmitting element, and φ

₁ is the angle formed by the reflected light and a normal line of the light outgoing surface.

4. The optical switching element of claim 1, further comprising a second light transmitting element that at least has

a light incident surface that is substantially parallel and opposite to the light outgoing surface of the first light transmitting element with a predetermined distance;

and

a light outgoing surface that is not parallel to the light incident surface of the second light transmitting element.

5. The optical switching element of claim 1, further comprising a light transmitting plate that is optically in contact with the second light incident surface of the first light transmitting element and has an index of refraction substantially the same as that of the first light transmitting element.

6. The optical switching element of claim 1, wherein the reflection substrate further comprises a second reflection surface having a tilt angle less than 90°

-θ

_2max tilted from the reflection substrate and a common edge shared with the first tilt surface, wherein the angle θ

_2max is defined as a maximum of an angle formed between a normal line of the second light incident surface and an incident light that enters the index variable material from the second light incident surface of the first light transmitting element.

7. The optical switching element of claim 1, wherein a plurality of reflection surfaces is formed on the reflection substrate, wherein reflection surfaces correspond respectively to elements used for applying external signals to the index variable material.

8. The optical switching element of claim 1, wherein the index variable material comprises a liquid crystal.

9. The optical switching element of claim 1, wherein the index variable material comprises a compound of a polymer and a liquid crystal such that the liquid crystal is dispersed in a polymer matrix.

10. The optical switching element of claim 9, wherein the liquid crystal is a droplet having a grain size below one-fifth wavelength of the incident light.

11. The optical switching element of claim 8, wherein all liquid crystal molecules are substantially aligned in one direction when no voltage is applied.

12. A spatial light modulator, comprising a plurality of the optical switching elements in any one of claims 1 to 11, wherein the optical switching elements are arranged in a two-dimensional array.

13. A spatial light modulator, comprising a plurality of the optical switching elements in any one of claims 1 to 11, wherein the optical switching elements are arranged in a one-dimensional array.

14. An image display apparatus, comprising:

a spatial light modulator in claim 12;

a device such that a light is incident to the spatial light modulator; and

a displaying device for projecting an image formed by the spatial light modulator to a screen.

15. An image display apparatus, comprising:

a spatial light modulator in claim 13;

a device such that a light is incident to the spatial light modulator;

a scanning device for scanning a light emitted from spatial light modulator in a direction perpendicular to a line direction of the optical switching elements of the spatial light modulator; and

a displaying device for projecting an image formed by the spatial light modulator to a screen.

17. The optical path element of claim 16, wherein the light incident unit and the light emitting unit are surfaces respectively, wherein both surfaces are not in parallel.

18. The optical path element of claim 16, wherein the optical switching element is switched between a first state and a second state, wherein the first state is that the total reflection occurs at the interface between the light transmitting element and an external material surrounding the light transmitting element, and the second state is that no total reflection occurs.

19. The optical path element of claim 16, further comprising a second light transmitting element that the incident light is emitted through the second light transmitting element.

20. The optical path element of claim 16, further comprising a light transmitting plate that is optically in contact with the light incident unit of the light transmitting element and has an index of refraction substantially the same as that of the light transmitting element.

21. The optical path element of claim 16, wherein the light reflection unit comprises two surfaces with a shared common edge, an angle formed between a normal line of one of the surfaces of the light reflection unit and a normal line of the surface forming the light incident unit is less than 90°

-θ

_2max, wherein the angle θ

_2max is defined as a maximum of an angle formed between the normal line of the surface forming the light incident unit and the incident light that enters the index variable material.

22. The optical path element of claim 16, wherein a plurality of reflection surfaces is formed on the reflection unit, wherein reflection surfaces correspond respectively to elements used for applying external signals to the index variable material.

23. The optical path element of claim 16, wherein the index variable material comprises a liquid crystal.

24. The optical path element of claim 16, wherein the index variable material comprises a compound of a polymer and a liquid crystal such that the liquid crystal is dispersed in a polymer matrix.

25. The optical path element of claim 24, wherein the liquid crystal is a droplet having a grain size below one-fifth wavelength of the incident light.

26. The optical path element of claim 23, wherein all liquid crystal molecules are substantially aligned in one direction when no voltage is applied.

16. An optical path element, comprising:

a light incident unit such that an incident light is incident through a light transmitting element;

a light reflection unit for reflecting the incident light from the light incident unit;

a light emitting unit for emitting a reflection light reflected by the light reflection unit out of the light transmitting element;

an index variable material filled into an optical path in the light reflection unit; and

a signal input device for providing a signal to the index variable material according to information to alter an index of refraction of the index variable material;

wherein the index of refraction of the index variable material is varied to a range such that the incident light is not totally reflected at an interface between the light transmitting element and the index variable material.

27. A spatial light modulator, comprising a plurality of the optical path elements in any one of claims 16 to 26, wherein the optical switching elements are arranged in a two-dimensional array.

28. A spatial light modulator, comprising a plurality of the optical path elements in any one of claims 16 to 26, wherein the optical path elements are arranged in a one-dimensional array.

29. An image display apparatus, comprising:

a spatial light modulator in claim 27;

a device such that a light is incident to the spatial light modulator; and

a displaying device for projecting an image formed by the spatial light modulator to a screen.

30. An image display apparatus, comprising:

a spatial light modulator in claim 28;

a device such that a light is incident to the spatial light modulator;

a scanning device for scanning a light emitted from spatial light modulator in a direction perpendicular to a line direction of the optical path elements of the spatial light modulator; and

a displaying device for projecting an image formed by the spatial light modulator to a screen.