Optical modulation element having two-dimensional phase type diffraction grating

• US 5,148,302 A
• Filed: 10/07/1991
• Issued: 09/15/1992
• Est. Priority Date: 04/10/1986
• Status: Expired due to Fees

• Current Assignee: Akihiko Nagano, Fujiwara, Ryoji, Kishi, Etsuro, Masato Yamanobe, Nishimura, Michiyo, Sakata, Hajime, Takayuki Ishii, Yukitoshi Ohkubo
• Original Assignee: Akihiko Nagano, Fujiwara, Ryoji, Kishi, Etsuro, Masato Yamanobe, Nishimura, Michiyo, Sakata, Hajime, Takayuki Ishii, Yukitoshi Ohkubo
• Inventors: Ishii, Takayuki, Nagano, Akihiko, Sakata, Hajime, Fujiwara, Ryoji, Nishimura, Michiyo, Kishi, Etsuro, Yamanobe, Masato, Ohkubo, Yukitoshi
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): PHAN, TRONG Q
• Application Number:
  US07/771,532
• Time in Patent Office: 344 Days
• Field of Search: 350/348, 350/344, 350/347 V, 350/346, 350/162.2
• US Class Current: 349/201
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/292 by controlled diffraction or phased-array beam steering controlled diffraction for optical switching G02F1/31
• CPC Class Codes: G02F 2201/305 diffraction grating
• CPC Class Codes: G02F 2203/22 diffractive

Abstract

An optical modulation element characterized in that a two-dimensional phase type diffraction gratings, whose refractive index changes for each predetermined period along two different directions in a predetermined plane, is adopted, and a changing state of the refractive index is controlled to change characteristics of the diffraction grating, so that a diffraction phenomenon of light incident on the element is controlled.

Claims

1. An optical modulation element comprising:

a first substrate;

a second substrate arranged at a position separated from said first substrate at a predetermined distance;

a pattern defining recesses formed between said first and second substrates, said pattern having a periodic construction forming recesses in a first direction in one plane and forming recesses in a second direction which is different from said first direction and on the same plane as the recesses in said first direction; and

an optical anisotropic medium which is sealed in the recesses of said pattern, a first portion of said medium being sealed by the recesses extending in said first direction and a second portion being sealed by the recesses extending in said second direction, said anisotropic medium having optical axes having directions which are defined according to said first and second directions and differ from each other, whereby said medium and said pattern together form a phase-type diffraction grating.

2. An optical modulation element according to claim 1, wherein said relief pattern is composed of a checkerboard-like pattern having regularly-spaced squares.

3. An optical modulation element according to claim 1, wherein said relief pattern is composed of plural areas having patterns with periodic constructions in directions which differ from each other.

4. An optical modulation element comprising:

first and second substrates, said substrates being separated from each other at a predetermined distance;

a pattern defining recesses formed between said first and second substrates, said pattern having a periodic

a first substrate;

a second substrate arranged at a position separated from said first substrate at a predetermined distance;

a pattern defining recesses formed between said first and second substrates, said pattern having a periodic construction forming recesses in a first direction in one plane and forming recesses in a second direction which is different from said first direction and on the same plane as the recesses in said firs direction; and

an optical anisotropic medium which is sealed in the recesses of said pattern, a first portion of said medium being sealed by the recesses extending in said first direction and a second portion being saddled by the recesses extending in said second direction, said anisotropic medium having optical axes having directions which are defined according to said first and second directions and differ from each other, whereby said medium and said pattern together form a phase-type diffraction grating.

5. An optical modulation element according to claim 4, wherein said relief pattern is composed of a checkerboard-like pattern having regularly-spaced squares.

6. An optical modulation element according to claim 4, wherein said relief pattern is composed of plural areas having patterns with periodic constructions in directions which differ from each other.

7. An optical modulation element according to claim 4, wherein said first and second recesses are fluidly connected with each other.

8. An optical modulation element according to claim 4, wherein each of said first and second substrates, said liquid crystal, said relief pattern and said electrode members are transparent to incident light.

9. An element according to claim 4, wherein a refractive index of said pattern is equal too that of each liquid crystal molecule when each said liquid crystal molecule of each said portion is directed toward a direction perpendicular to a surface of each of said substrates.

10. An element according to claim 4, wherein the changing means directs each said liquid crystal molecule of each said portion toward the perpendicular direction.

11. An element according to claim 4, wherein said pattern is formed by periodically arranging a zigzag pattern in a predetermined direction different from each said direction, and wherein said recesses extending in said first and second directions are alternately formed between each zigzag pattern.

12. An element according to claim 4, wherein depths of said recesses and height of a liquid crystal layer sealed between each of said substrates are substantially equal to each other.

13. An element according to claim 4, wherein said pattern defining recesses is formed on one of said substrates.

14. An element according to claim 4, wherein the changing means includes means for applying an electric field to said liquid crystals of said portions.

15. An optical modulation element comprising two types of periodic recesses with an optical anisotropic medium sealed between a pair of substrates for diffracting incident light toward said element by a phase-type diffraction grating comprising said periodic recesses and said medium, wherein:

said two types of periodical recesses are coplanar and formed in directions which are substantially perpendicular to each other, said plane being parallel to the substrate surfaces of said substrates; and

said phase-type diffraction grating diffracts polarized components of said incident light which are substantially perpendicular to each other, and wherein one of said components is diffracted by said phase-type diffraction grating formed by one of said two types of periodical recesses and said medium and the other of said components is diffracted by said phase-type diffraction grating formed by the other of said two types of periodical recesses and said medium.

16. An element according to claim 15, wherein said direction has optical axes and

(i) a predetermined portion of said medium is sealed by recesses formed along one of said directions;

and the optical axis of said predetermined portion is directed toward the one direction in a predetermined state, and

(ii) a portion of said medium other than said predetermined portion is sealed by recesses formed along the other portion is directed toward the other direction in said predetermined state.

17. An element according to claim 16, further comprising electrode means for applying voltage for changing said optical axes of said portions of said medium so as to adjust refractive indexes thereof.

18. An element according to claim 17, wherein said medium comprises a liquid crystal, and molecules of said liquid crystal at each of said portions are arranged in a direction corresponding to each said portion.

19. An element according to claim 17, wherein the electrode means is able to make the directions of said optical axes of each said portion substantially perpendicular to each of said substrate surfaces in a state other than said predetermined state, and wherein said predetermined portion and said portion other than said predetermined portion have the same refractive indexes.

20. An element according to claim 19, wherein said member is formed by arranging a zigzag pattern in another predetermined direction different from each said direction.

21. An optical modulation element comprising:

first and second substrates, said substrates being separated from each other at a predetermined distance;

a pattern defining a plurality of grooves formed between said first and second substrates, said pattern being formed by arranging a plurality of zigzag patterns in a predetermined direction, wherein a groove extending in a first direction and a groove extending in a second direction substantially perpendicular to said first direction are alternately formed between each of said zigzag patterns;

a liquid crystal layer sealed between said first and second substrates, wherein a first portion of said liquid crystal layer is sealed by said groove extending in said first direction, and liquid crystal molecules of said first portion are arranged along said first direction in a predetermined state, and wherein a second portion of said liquid crystal layer is sealed by said groove extending in said second direction and liquid crystal molecules of said second portion are arranged along said second direction in said predetermined state; and

electrode means for applying voltage changing arrangement directions of liquid crystal molecules of each of said portions so as to change a refractive index of said liquid crystal layer.

22. An element according to claim 21, wherein depths of said plurality of grooves and a height of said liquid crystal layer are substantially equal to each other.

23. An element according to claim 22, wherein a refractive index of each of said portions and that of a material forming said pattern are substantially equal to each other in a state where said liquid crystal molecules are each of said portions are arranged in a direction substantially perpendicular to a substrate surface of each of said substrates.

24. An optical modulation device comprising a pair of substrates, a pattern formed to arrange a plurality of recesses between said pair of substrates, an optical anisotropic medium sealed between said plurality of recesses, and means for changing directions of optical axes of said medium in such a manner that in a first state, said medium and said pattern have substantially matched refractive indexes and in a second state, said medium and said pattern have mismatched refractive indexes, and further in the first state, an incident light beam is substantially transmitted through said optical device without being diffracted and in the second state, said incident light beam is scattered, said optical modulation device comprising said plurality of recesses constituted in combination with recesses extending in directions different from each other along a common plane.

25. A device according to claim 24, wherein said medium comprises a liquid crystal.

26. A device according to claim 24, wherein said combination of said recesses constitutes a grating.

27. A device according to claim 24, wherein said directions include directions perpendicular to each other.

28. A device according to claim 24, wherein said directions are randomly set up.

29. A device according to claim 26, 27 or 28, wherein said pattern is set up so as to regularly form said plurality of recesses so that said incident light beam may be scattered with being refracted in the second state.