Polarization device to polarize and further control light

• US 7,800,823 B2
• Filed: 12/15/2006
• Issued: 09/21/2010
• Est. Priority Date: 12/06/2004
• Status: Active Grant

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Perkins, Raymond T.
• Primary Examiner(s): Lavarias; Arnel C
• Application Number:
  US11/640,112
• Publication Number:
  US 20080266662A1
• Time in Patent Office: 1,376 Days
• Field of Search: None
• US Class Current: 359/485.05
• CPC Class Codes: G02B 27/4261 having a diffractive element with major polarization dependent properties
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: G02B 5/286 having four or fewer layers, e.g. for achieving a colour effect
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles

Abstract

A polarization device includes an optical stack with a diffraction grating and a wire grid polarizer with one disposed over the other. The wire grid polarizer includes an array of elongated, parallel conductive wires in accordance with P_WGP<λ/2 where P_WGP is the period of the wires and λ is the wavelength of the light. The diffraction grating includes an array of elongated parallel dielectric ribs in accordance with P_DG>λ/2 where P_DG is the period of the ribs.

Claims

1. A polarization device configured to polarize and further control light incident on the device, comprising:

an optical stack with a diffraction grating and a wire grid polarizer with one disposed over the other and configured to be disposed in the light,

the wire grid polarizer including an array of elongated, parallel conductive wires in accordance with P_WGP<

λ

/2 where P_WGP is a period of the wires and λ

is a wavelength of the light, to polarize the light by substantially reflecting light having an s-polarization orientation and substantially transmitting light having a p-polarization orientation, and

the diffraction grating including an array of elongated parallel dielectric ribs in accordance with P_DG>

λ

/2 where P_DG is a period of the ribs, to substantially diffract light with s-polarization orientation of non-zero order at a non-orthogonal angle, so that the diffraction grating and the wire grid polarizer together pass light having p-polarization orientation while diffracting light having s-polarization orientation.

2. A device in accordance with claim 1, wherein the period of the wires is less than about 0.21 microns;

and wherein the period of the ribs is greater than 0.21 microns and less than 0.7 microns.

3. A device in accordance with claim 1, wherein the period of the diffraction grating is approximately five times greater than the period of the wire grid polarizer.

4. A device in accordance with claim 1, wherein the diffraction grating is stacked over the wire grid polarizer with the incident light incident on the diffraction grating;

and wherein the diffraction grating diffracts reflected light with the s-polarization orientation of non-zero order.

5. A device in accordance with claim 1, wherein the wire grid polarizer is stacked over the diffraction grating with the incident light incident on the wire grid polarizer;

and

wherein the diffraction grating diffracts transmitted light with p-polarization.

6. A device in accordance with claim 1, further comprising:

a continuous layer disposed between the wire grid polarizer and the diffraction grating, and having a refractive index less than a refractive index of a supporting substrate.

7. A device in accordance with claim 1, further comprising:

at least two continuous layers disposed between the wire grid polarizer and the diffraction grating, including an upper layer with a refractive index greater than a refractive index of a lower layer.

8. A device in accordance with claim 7, wherein the lower layer extends into spaces between the wires of the wire grid polarizer.

9. A device in accordance with claim 1, wherein the array of conductive wires of the wire grid and the array of dielectric ribs of the diffraction grating are parallel with one another.

10. A device in accordance with claim 1, wherein the device substantially transmits light with p-polarization orientation and substantially diffracts light with s-polarization orientation of non-zero order, without substantially back reflecting light with s-polarization orientation of zero order.

11. A device in accordance with claim 1, wherein the ribs of the diffraction grating are split into two ribs.

12. A device in accordance with claim 1, further comprising an imaging system including:

a spatial light modulator including a liquid crystal material; and

a polarization beam splitter.

13. A polarization device configured to control light of a visible light beam having a wavelength between 0.4-0.7 microns incident on the device, comprising:

an optical stack with a diffraction grating stacked over a wire grid polarizer, with the visible light beam incident on the diffraction grating at substantially an orthogonal orientation,

the wire grid polarizer including an array of elongated, parallel conductive wires in accordance with P_WGP<

λ

/2 where P_WGP is a period of the wires and λ

is the wavelength of the visible light beam, to polarize the visible light beam by substantially reflecting light having an s-polarization orientation and substantially transmitting light having a p-polarization orientation, and

the diffraction grating including an array of elongated parallel dielectric ribs in accordance with P_DG>

λ

/2 where P_DG is a period of the ribs, to substantially diffract light with s-polarization orientation of non-zero order at a non-orthogonal angle, so that the diffraction grating and the wire grid polarizer together pass light having p-polarization orientation while diffracting light having s-polarization orientation.

14. A device in accordance with claim 13, wherein the period of the diffraction grating is approximately five times greater than the period of the wire grid polarizer.

15. A device in accordance with claim 13, further comprising:

a continuous layer disposed between the wire grid and the diffraction grating, and having a refractive index less than a refractive index of a supporting substrate.

16. A device in accordance with claim 13, further comprising:

at least two continuous layers disposed between the wire grid polarizer and the diffraction grating, including an upper layer with a refractive index greater than a refractive index of a lower layer.

17. A device in accordance with claim 16, wherein the lower layer extends into spaces between the wires of the wire grid polarizer.

18. A device in accordance with claim 13, wherein the array of conductive wires of the wire grid and the array of dielectric ribs of the diffraction grating are parallel with one another.

19. A device in accordance with claim 13, wherein the device substantially transmits light with p-polarization orientation and substantially diffracts light with s-polarization orientation of non-zero order, without substantially back reflecting light with s-polarization orientation of zero order.

20. A device in accordance with claim 13, wherein the ribs of the diffraction grating are split into two ribs.

21. A device in accordance with claim 13, wherein the period of the wires is less than about 0.21 microns;

and wherein the period of the ribs is greater than 0.21 microns and less than 0.7 microns.

22. A device in accordance with claim 13, further comprising an imaging system including:

a spatial light modulator including a liquid crystal material; and

a polarization beam splitter.

23. A method for polarizing a visible light beam while reducing back reflection and unwanted astigmatism in an optical path defined by the visible light beam, comprising:

disposing a diffraction grating and wire grid polarizer stack in the optical path with the visible light beam incident on the diffraction grating, and

orienting the stack substantially orthogonally with respect to the visible light beam incident on the diffraction grating,

the wire grid polarizer substantially polarizing the visible light beam by substantially reflecting light having an s-polarization orientation and substantially transmitting light having a p-polarization orientation, with an array of elongated, parallel conductive wires with a period less than about 0.21 microns,

the diffraction grating substantially diffracting light with s-polarization orientation having non-zero order at a non-orthogonal angle, with an array of elongated parallel dielectric ribs with a period greater than 0.21 microns, the diffraction grating and the wire grid polarizer together thereby passing light having p-polarization orientation while diffracting light having s-polarization orientation with non-zero order.