Chip-scale star tracker

Patent metadata

Field	Value
Publication number	US-9891305-B2
Application number	US-201615172481-A
Country	US
Kind code	B2
Filing date	Jun 3, 2016
Priority date	Jun 28, 2013
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A chip scale star tracker that couples starlight into a lightguide such that the angle of incidence partially determines the mode of propagation of the starlight in the lightguide. A baffle system integrated with the lightguide prevents propagation of light incident from a predetermined range of angles.

First claim

What is claimed is:

1. A star tracker comprising:
a lightguide;
a coupling structure disposed on a surface of the lightguide and configured to couple starlight into the lightguide such that a mode of propagation of the starlight in the lightguide is at least partially determined by an angle of incidence of the starlight on the coupling system; and
a baffle system integrated with the lightguide and configured to prevent propagation in the lightguide of light incident on the coupling structure from a predetermined range of angles of incidence.

2. The star tracker of claim 1 wherein the lightguide includes a dielectric material and the baffle system comprises a tapered refractive index of the dielectric material.

3. The star tracker of claim 1 wherein a dielectric material of at least one of the lightguide, the coupling structure, and the baffle system includes a tunable refractive index.

4. The star tracker of claim 1 further comprising a detector system coupled to the lightguide and configured to analyze the starlight propagated in the lightguide to determine at least one of an azimuth angle and an elevation angle of a star that is a source of the starlight.

5. The star tracker of claim 1 wherein the lightguide includes a plurality of output apertures, and further comprising an interferometer coupled to the lightguide and configured to determine phase information of the starlight propagated through at least two output apertures of the plurality of output apertures.

6. The star tracker of claim 1 further comprising:
a plurality of optical apertures coupled to the lightguide;
an interferometer selectively coupled to a pair of the plurality of optical apertures and configured to determine a phase difference between the starlight propagated via the lightguide to each of the pair of the plurality of optical apertures; and
an optical switch coupled to the plurality of optical apertures and configured to selectively couple the pair of the plurality of optical apertures to the interferometer.

7. A star tracker comprising:
a lightguide;
a coupling structure disposed on a surface of the lightguide and configured to couple starlight into the lightguide such that a mode of propagation of the starlight in the lightguide is at least partially determined by an angle of incidence of the starlight on the coupling system;
a pair of optical apertures coupled to the lightguide, each configured to propagate a portion of the starlight; and
an interferometer configured to determine phase information of the starlight propagated through each of the pair of optical apertures.

8. The star tracker of claim 7 wherein a dielectric material of at least one of the lightguide, the coupling structure, and the interferometer includes a tunable refractive index.

9. The star tracker of claim 7 further comprising a processor coupled to the interferometer and configured to construct an image based on the phase information.

10. The star tracker of claim 7 further comprising a detector system coupled to the lightguide and configured to analyze the starlight propagated in the lightguide to determine at least one of an azimuth angle and an elevation angle of a star that is a source of the starlight.

11. A method of capturing starlight comprising:
coupling starlight from at least one star into a lightguide;
propagating the starlight via the lightguide, wherein a mode of propagation of the starlight in the lightguide is based at least in part on an angle of incidence of the starlight on a surface of the lightguide
providing the starlight, propagated via the lightguide, at a pair of optical apertures; and
determining phase information of the starlight provided at the pair of optical apertures.

12. The method of claim 11 further comprising determining at least one of an azimuth angle and an elevation angle of the at least one star based on detected characteristics of the starlight.

13. The method of claim 11 further comprising spectrally sampling the starlight into one or more spectral bands.

14. The method of claim 11 further comprising tuning a refractive index of a dielectric material of the lightguide.

15. The method of claim 11 further comprising controlling an optical path length of the starlight provided at at least one of the pair of optical apertures.

16. The method of claim 11 further comprising constructing an image using the phase information.

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Laine Juha Pekka
• Blasche Gregory P
• Chaparala Murali V
• Dawson Robin
• Lane Benjamin
• Smith Stephen P
• Waldron Erik

Classifications

• G02B6/0288

  Multimode fibre, e.g. graded index core for compensating modal dispersion · CPC title

• G01C21/025

  with the use of startrackers · CPC title

• G01S3/785

  using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system · CPC title

• G01S3/7867 Primary

  Star trackers (navigation using star trackers G01C21/025) · CPC title

• G01B2290/10

  Astronomic interferometers · CPC title