High performance scanning miniature star camera system

Patent metadata

Field	Value
Publication number	US-9648252-B2
Application number	US-201414211210-A
Country	US
Kind code	B2
Filing date	Mar 14, 2014
Priority date	Mar 14, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A star camera system that includes an optical system configured to focus radiation from a star to be imaged onto a collector that is in the form of an electron bombarded active pixel sensor (EBAPS) configured to provide high gain. The EBAPS comprising a photocathode disposed in a vacuum is configured to release electrons into the vacuum when exposed to radiation focused thereon by the optical system. The EBAPS includes an active pixel sensor anode disposed distant from the photocathode in the vacuum. An electric field is generated by a voltage source to direct the electrons from the photocathode to the active pixel sensor anode. Furthermore, the collector is mounted on a translation device configured to move the collector relative to the optical system by a predetermined amount of less than pixel size in the focal plane of the optical system to increase image resolution of a plurality of images.

First claim

The invention claimed is:

1. A star camera system, comprising:
an optical system configured to focus radiation from a star to be imaged onto a collector disposed at the focal plane of the optical system; and
a collector in the form of an electron bombarded active pixel sensor, the collector including:
a photocathode disposed in a vacuum and configured to release electrons into the vacuum when exposed to radiation focused thereon by the optical system;
an active pixel sensor anode having pixels of a predetermined size disposed distant from the photocathode in the vacuum; and
a voltage source to generate an electric field between the photocathode and the active pixel sensor anode configured to direct the electrons from the photocathode to the active pixel sensor anode to generate an image of the star,

wherein the collector is mounted on a translation device configured to move the collector relative to the optical system by a predetermined amount of less than pixel size in the focal plane of the optical system,
thereby increasing image resolution when a plurality of images taken at different relative positions are compared.

2. The star camera system of claim 1 , wherein the optical system is a centro symmetric folded structure.

3. The star camera system of claim 1 , wherein:
the optical system is configured to focus ultraviolet radiation from the start to be imaged onto the collector,
the electron bombarded active pixel sensor is an ultraviolet sensitive electron bombarded active pixel sensor, including:
an ultraviolet sensitive photocathode,
wherein the electric field is generated between the ultraviolet sensitive photocathode and the active pixel sensor anode.

4. The star camera system of claim 3 , wherein the ultraviolet sensitive photocathode comprises gallium nitride.

5. The star camera system of claim 1 , wherein:
the optical system is configured to focus infrared radiation from the star to be imaged onto the collector,
the photocathode is an infrared sensitive photocathode, and
the electric field is generated between the infrared sensitive photocathode and the active pixel sensor anode.

6. The star camera system of claim 5 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

7. A method of capturing a star image for celestial navigation, orientation, position and attitude measurement, and solution correction, comprising:
projecting the star image onto a collector in the form of an electron bombarded active pixel sensor, the electron bombarded active pixel sensor, including:
a photocathode disposed in a vacuum to release electrons in the vacuum when exposed to radiation from the star focused thereon by an optical system;
an active pixel sensor anode distant from the photocathode in the vacuum to detect the image of the electrons released from the photocathode; and
a voltage source to generate an electric field between the photocathode and the active pixel sensor anode to move the electrons from the photocathode to the active pixel sensor anode;

outputting a first signal indicative of a first image from the active pixel sensor anode;
moving the collector having pixels of a predetermined size within the focal plane of the optical system by an amount less than pixel size relative to the optical system using a translation device on which the collector is mounted;
outputting a second signal indicative of a second image from the active pixel sensor anode; and
integrating the first signal and the second signal to increase image resolution.

8. The method of claim 7 , wherein:
the optical system is configured to focus ultraviolet radiation from the start to be imaged onto the collector,
the electron bombarded active pixel sensor is an ultraviolet sensitive electron bombarded active pixel sensor, including:
an ultraviolet sensitive photocathode,
wherein the electric field is generated between the ultraviolet sensitive photocathode and the active pixel sensor anode.

9. The method of claim 8 , wherein the ultraviolet sensitive photocathode comprises gallium nitride.

10. The method of claim 7 , wherein:
the optical system is configured to focus infrared radiation from the star to be imaged onto the collector,
the photocathode is an infrared sensitive photocathode, and
the electric field is generated between the infrared sensitive photocathode and the active pixel sensor anode.

11. The method of claim 10 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

12. A star camera, comprising:
an optical system configured to focus radiation from a star to be imaged onto a collector; and
a collector in the form of an electron bombarded active pixel sensor, comprising:
a photocathode disposed in a vacuum and configured to release electrons into the vacuum when exposed to radiation focused thereon by the optical system;
an active pixel sensor anode having pixels of a predetermined size disposed distant from the photocathode in the vacuum; and
a voltage source to generate an electric field between the photocathode and the active pixel sensor anode configured to direct the electrons from the photocathode to the active pixel sensor anode to generate an image of the star,

wherein the optical system is mounted on a translation device configured to move the optical system relative to the collector by a predetermined amount of less than pixel size in the focal plane of the optical system,
thereby increasing image resolution when a plurality of images taken at different relative positions are compared.

13. The star camera system of claim 12 , wherein the optical system is a centro symmetric folded structure.

14. The star camera system of claim 12 , wherein:
the optical system is configured to focus ultraviolet radiation from the start to be imaged onto the collector,
the electron bombarded active pixel sensor is an ultraviolet sensitive electron bombarded active pixel sensor, including:
an ultraviolet sensitive photocathode,
wherein the electric field is generated between the ultraviolet sensitive photocathode and the active pixel sensor anode.

15. The star camera system of claim 14 , wherein the ultraviolet sensitive photocathode comprises gallium nitride.

16. The star camera system of claim 12 , wherein:
the optical system is configured to focus infrared radiation from the star to be imaged onto the collector,
the photocathode is an infrared sensitive photocathode, and
the electric field is generated between the infrared sensitive photocathode and the active pixel sensor anode.

17. The star camera system of claim 16 , wherein the electron bombarded active pixel sensor comprises a silicon germanium layer.

18. A method of capturing a star image for celestial navigation, orientation, position and attitude measurement, and solution correction, comprising:
focusing an optical system of an imager toward a star;
projecting a star image onto a collector in the form of an electron bombarded active pixel sensor, the electron bombarded active pixel sensor, comprising:
a photocathode disposed in a vacuum to release electrons in the vacuum;
an active pixel sensor anode having pixels of a predetermined size distant from the photocathode in the vacuum to detect the electrons released from the photocathode; and
a voltage source to direct the electrons from the photocathode to the active pixel sensor anode;

outputting a first signal from the active pixel sensor anode;
moving the optical system in the focal plane of the collector using a translat

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Laine Juha-Pekka J
• Blasche Gregory
• Boyle John J
• Bohn Paul
• Dawson Robin M
• Lane Benjamin F
• Waldron Erik L

Classifications

• H01J31/26 Primary

  Image pick-up tubes having an input of visible light and electric output (tubes without defined electron beams and having a light ray scanning photo-emissive screen H01J40/20) · CPC title

• H04N23/20

  for generating image signals from infrared radiation only · CPC title

• H01J31/501

  with an electrostatic electron optic system (H01J31/52 - H01J31/56 take precedence) · CPC title

• H04N5/33

  Transforming infrared radiation (cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20) · CPC title

• H04N5/30 Primary

  Transforming light or analogous information into electric information (scanning details H04N3/00; cameras or camera modules comprising electronic image sensors, or control thereof H04N23/00; circuitry of solid-state image sensors [SSIS] or control thereof H04N25/00) · CPC title