Electronically variable light attenuator

• US 6,525,860 B1
• Filed: 05/18/2000
• Issued: 02/25/2003
• Est. Priority Date: 05/18/2000
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Holz, Michael, Corkum, David L.
• Primary Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US09/574,357
• Time in Patent Office: 1,013 Days
• Field of Search: 359/250, 359/251, 359/252, 359/253, 359/254, 349/129
• US Class Current: 359/251
• CPC Class Codes: G02F 1/1326 Liquid crystal optical waveguides or liquid crystal cells specially adapted for gating or modulating between optical waveguides
• CPC Class Codes: G02F 1/133757 with different alignment orientations
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• 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 1/2955 by controlled diffraction or phased-array beam steering controlled diffraction for optical waveguide switching G02F1/313
• CPC Class Codes: G02F 2201/305 diffraction grating
• CPC Class Codes: G02F 2203/22 diffractive
• CPC Class Codes: G02F 2203/48 Variable attenuator

Abstract

An electronically variable light attenuator and method for electronically attenuating light. The attenuator has an array of liquid crystal regions. The regions in a first set thereof are interspersed with the regions in a second set thereof. The array is adapted to receive a beam of light directed along an axis. A pair of electrodes is provided. At least one of the sets of regions is disposed between the electrodes. The regions in the first set are configured to produce a first diffraction pattern in response to the received light and the regions in the second set are configured to produce a second diffraction pattern in response to the received light. The pair of electrodes are arranged to enable the first and second diffraction patterns to combine with a degree of interference along an axis selected in accordance with an electric field produced between the pair of electrodes and through the at least one of the sets of regions. The array degree of interference is greatest in the absence of the electric field. With such an arrangement, a relatively low cost, high power, fail-safe, electronically variable light attenuator is provided.

Claims

1. An electronically variable light attenuator, comprising:

an array of liquid crystal regions, the regions in a first set thereof being interspersed with the regions in a second set thereof, such array being adapted to receive a beam of light directed along an axis;

a pair of electrodes, at least one of the sets of liquid crystal regions being disposed between the pair of electrodes, such pair of electrodes being disposed along a common surface of the array of liquid crystal regions to produce an electric field having components disposed parallel to such common surface;

wherein the regions in the first set are configured to produce a first diffraction pattern in response to the received light and the regions in the second set are configured to produce a second diffraction pattern in response to the received light; and

wherein the pair of electrodes are arranged to enable the first and second diffraction patterns to combine with a degree of interference along an axis selected in accordance with an electric field produced through the at least one of the sets liquid crystal regions disposed between the pair of electrodes.

3. The attenuator recited in claim 1 wherein the degree of interference is greatest in the absence of the electric field.

4. The attenuator recited in claim 1 wherein the degree of interference is independent of the polarization of the received light.

5. The attenuator recited in claim 4 wherein the degree of interference is greatest in the absence of the electric field.

6. The attenuator recited in claim 1 wherein the regions comprise molecules, such molecules being elongated along a director field axis, and wherein the director field axis of the molecules in the first set is orthogonal to the director field axis of the molecules in the second set.

7. The attenuator recited in claim 6 wherein the director field axis of the molecules in the first set and the director field axis of the molecules in the second set are both orthogonal to the direction of the received light.

8. The attenuator recited in claim 1 wherein the regions in the first set provide an nπ

phase shift to the received light relative to the phase shift provided to the received light by the regions in the second set, where n is an odd integer.

9. The attenuator recited in claim 1 wherein the regions in the first set provide an nπ

phase shift to the received light relative to the phase shift provided to the received light by the regions in the second set, where n is an odd integer in the absence of an electric field between the pair of electrodes.

2. An electronically variable light attenuator, comprising:

an array of liquid crystal regions, the regions comprising a plurality of sets thereof, each one of the sets having a plurality of subsets of the regions, such subsets being interspersed within the set thereof, such array being adapted to receive a beam of light directed along an axis;

a pair of electrodes, at least one of the sets of liquid crystal regions being disposed between the pair of electrodes;

wherein the regions in the subsets of each set thereof are configured to produce a corresponding diffraction pattern in response to the received light; and

wherein the pair of electrodes are arranged to enable the corresponding diffraction pattern of the subsets combine with a degree of interference along an axis selected in accordance with an electric field produced between the pair of electrodes.

10. A method for electronically varying light attenuation, comprising:

providing a pair of electrodes with at least one set of a first and second set of regions of an array of liquid crystal regions therebetween, such pair of electrodes being disposed along a common surface of the array of liquid crystal regions to produce an electric field having components disposed parallel to such common surface;

the regions in the first set thereof being interspersed with the regions in the second set thereof, such array being adapted to receive a beam of light directed along an axis, the regions in the first set are configured to produce a first diffraction pattern in response to the received light and the regions in the second set are configured to produce a second diffraction pattern in response to the received light; and

varying an electric field between the electrodes and passing through the at least one of the sets of regions producing the first and second diffraction patterns with a varying degree of interference along the axis.

11. The method recited in claim 10 wherein the array degree of interference produced is greatest in the absence of the electric field.

12. The method recited in claim 10 wherein the degree of interference produced is independent of the polarization of the received light.

13. The method recited in claim 12 wherein the array degree of interference produced is greatest in the absence of the electric field.

14. The method recited in claim 10 wherein the regions is provided with molecules, such molecules being elongated along a director field axis, and wherein the director field axis of the molecules in the first set is orthogonal to the director field axis of the molecules in the second set in the absence of the electric field.

15. The method recited in claim 14 wherein the director field axis of the molecules in the first set and the director field axis of the molecules in the second set are both oriented orthogonal to the direction of the received light in the absence of the electric field.

16. The method recited in claim 10 wherein the regions in the first set provide an nπ

phase shift to the received light relative to the phase shift provided to the received light by the regions in the second set, where n is an odd integer.

17. The method recited in claim 10 wherein the regions in the first set provide an nπ

phase shift to the received light relative to the phase shift provided to the received light by the regions in the second set, where n is an odd integer in the absence of an electric field between the pair of electrodes.

18. A structure comprising:

an array of liquid crystal regions, the regions in a first set thereof being interspersed with the regions in a second set thereof;

a pair of electrodes, at least one of the sets of liquid crystal regions being disposed between the pair of electrodes, such pair of electrodes being disposed along a common surface of the array of liquid crystal regions to produce an electric field having components disposed parallel to such common surface.