Star tracker with adjustable light shield

Patent metadata

Field	Value
Publication number	US-12130141-B2
Application number	US-202017072716-A
Country	US
Kind code	B2
Filing date	Oct 16, 2020
Priority date	May 14, 2013
Publication date	Oct 29, 2024
Grant date	Oct 29, 2024

Abstract

A navigation system includes a star camera having a field of view. The star camera includes a sun shields that selectively block portions of the star camera's field of view, to prevent unwanted light, such as light from the sun or moon, reaching image sensors of the star cameras. Some sun shields include x-y stages or r-θ stages to selectively position a light blocker to block the unwanted light. Some sun shields use positionable partially overlapping orthogonally polarized filters to block the unwanted light. Some sun shields use counter-wound spiral windows that are selectively rotated to block the unwanted light. Some sun shields a curved surface that defines a plurality of apertures fitted with individual mechanical or electronic shutters.

First claim

What is claimed is:

1. A star camera comprising:
a lens having a focal length and a field of view;
a pixelated digital image sensor oriented toward the lens and disposed a distance from the lens equal to the focal length of the lens, such that the lens projects an image of the field of view onto the sensor, thereby defining a light path from the field of view to the sensor;
a light blocker disposed within the light path; and
a mechanical positioner coupled to the light blocker and configured to position the light blocker with at least two degrees of freedom at an electronically selectable location within the light path, such that the light blocker blocks visibility by the sensor of a selectable portion of the field of view; wherein
the light blocker has a size such that the portion of the field of view blocked by the light blocker has an angular diameter of at least 30′ and at most 45′.

2. The star camera according to claim 1 , wherein the size of the light blocker is fixed.

3. The star camera according to claim 1 , wherein the size of the light blocker is variable.

4. The star camera according to claim 1 , wherein the mechanical positioner comprises an x-y stage.

5. The star camera according to claim 4 , wherein the light blocker translates along a plane.

6. The star camera according to claim 5 wherein the light blocker is disposed between the lens and the pixelated digital image sensor.

7. The star camera according to claim 5 , wherein the light blocker is disposed between the lens and the field of view of the lens.

8. The star camera according to claim 1 , wherein the mechanical positioner comprises:
a motorized turntable configured to translate the light blocker along an arc; and
a linear actuator mechanically coupled between the light blocker and the motorized turntable and configured to translate the light blocker radially from the motorized turntable.

9. The star camera according to claim 1 , wherein the mechanical positioner comprises an r-θ stage.

10. The star camera according to claim 8 , wherein the light blocker translates along a plane.

11. the star camera according to claim 8 , wherein the light blocker translates along a curved surface.

12. The star camera according to claim 11 , wherein the mechanical positioner comprises:
a curved track;
a first actuator couple to the curved track and configured to pivot the curved track about a pivot axis; and
a second actuator coupled between the curved track and the light blocker and configured to translate the light blocker along the curved track.

13. The star camera according to claim 1 , wherein:
the light blocker comprises:
a first polarized filter having a first axis of polarization; and
a second polarized filter having a second axis of polarization, the second polarized filter partially overlapping the first polarized filter, the second axis of polarization being perpendicular to the first axis of polarization; and

the mechanical positioner comprises:
a first actuator coupled to the first polarized filter and configured to translate the first polarized filter along a first axis of translation; and
a second actuator coupled to the second polarizing filter and configured to translate the second polarized filter along a second axis of translation, the second axis of translation being perpendicular to the first axis of translation.

14. The star camera according to claim 1 , wherein:
the light blocker comprises:
a first polarized filter having a first axis of polarization; and
a second polarized filter having a second axis of polarization, the second polarized filter partially overlapping the first polarized filter, the second axis of polarization being perpendicular to the first axis of polarization; and

the mechanical positioner comprises:
a first actuator coupled to the first polarized filter and configured to rotate the first polarized filter about a first axis of rotation; and
a second actuator coupled to the second polarizing filter and configured to rotate the second polarized filter about a second axis of rotation, the second axis of rotation being perpendicular to the first axis of rotation.

15. The star camera according to claim 1 , wherein:
the light blocker has a common axis, and the light blocker comprises, centered thereon:
a first set of leaves;
a second set of leaves coupled to, in synchrony with, and disposed below the first set of leaves;

a central disk coupled to and disposed below the second set of leaves; and
a driver wheel disposed between and coupled to the first and second sets of leaves, the driver wheel disposed above and coupled to the central disk, the driver wheel configured to expand or collapse, by rotation along the common axis, particular leaves of the first set of leaves and particular leaves of the second set of leaves, the expansion or the collapse affecting the portion of the field of view blocked by the light blocker by modification of passage of light through the central disk based on increase or decrease of apertures between the particular leaves of the first set of leaves and corresponding apertures between the particular leaves of the second set of leaves.

16. The star camera according to claim 1 , wherein the pixelated digital image sensor is sensitive to light within a range of wavelengths and the light blocker comprises a material that is opaque to light within the range of wavelengths.

17. The star camera according to claim 1 , wherein:
the light blocker comprises:
a first mask defining a first spiral transparent aperture, the first mask being otherwise opaque at predefined wavelengths; and
a second mask defining a second spiral transparent aperture, the second mask being otherwise opaque at the predefined wavelengths, the second spiral aperture being wound opposite the first spiral transparent aperture; and

the mechanical positioner comprises:
a first actuator coupled to the first mask and configured to rotate the first mask about an axis of rotation; and
a second actuator coupled to the second mask and configured to rotate the second mask about the axis of rotation.

18. A star camera comprising:
a lens having a focal length and a field of view;
a pixelated digital image sensor oriented toward the lens and disposed a distance from the lens equal to the focal length of the lens, such that the lens projects an image of the field of view onto the sensor, thereby defining a light path from the field of view to the sensor;
a light blocker disposed within the light path, the light blocker comprising:
a curved surface defining a plurality of transparent apertures, the curved surface being otherwise opaque; and
a plurality of shutters, each shutter being disposed adjacent a respective aperture of the plurality of apertures and selectively controlling passage of light through the aperture, wherein each shutter has a first mode, in which the aperture is rendered transparent, and a second mode, in which the aperture is rendered opaque.

19. The star camera according to claim 18 , wherein each shutter comprises a respective mechanical door.

20. The star camera according to claim 18 , wherein each shutter comprises a respective LCD element.

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Dawson Robin Mark Adrian
• Laine Juha-Pekka J
• Lane Benjamin F
• Chaparala Murali V
• Arant Charles F
• Jamula Matthew T

Classifications

• B64C39/024

  of the remote controlled vehicle type, i.e. RPV · CPC title

• H04N23/60

  Control of cameras or camera modules · CPC title

• H04N23/58

  Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors · CPC title

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• H04N23/54

  Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils · CPC title