Ball joint gimbal imaging system with an off-gimbal directional electro-optic component

Patent metadata

Field	Value
Publication number	US-9372340-B2
Application number	US-201414267437-A
Country	US
Kind code	B2
Filing date	May 1, 2014
Priority date	May 1, 2014
Publication date	Jun 21, 2016
Grant date	Jun 21, 2016

Abstract

A ball joint gimbal imaging system includes on-gimbal optics that reimage a front optical aperture to a smaller back optical aperture that moves with the rotation of the inner ball. Relay optics are configured to relay the back optical aperture to an electro-optic component mounted on the platform, off-gimbal. Relay optics includes a first two-axis steering element (on or off-gimbal) that is positioned and sized to cover the range of motion of the beam from the back optical aperture across the range of gimbal motion. The first two-axis steering element is controlled to steer the optical beam passing through the back optical aperture into a second off-gimbal two-axis steering element that is controlled to tilt the optical beam to align light along the central axis of the electro-optic element with the central axis of the front optical aperture on the inner ball, which is coincident with the gimbal pointing axis.

First claim

I claim:

1. A ball joint gimbal electro-optic system, comprising:
a platform;
a ball gimbal mounted on the platform, said ball gimbal including a socket fixedly mounted on the platform and an inner ball captured within the socket and free to rotate about combinations of three orthogonal axes to point a pointing axis within a range of gimbal motion;
a directional electro-optic element mounted on the platform, off-gimbal;
optics mounted within the inner ball, said optics having a central axis substantially coincident with the pointing axis, said optics configured to reimage an optical beam from a front optical aperture to a smaller back optical aperture that moves relative to the platform with the rotation of the inner ball;
a motor configured to apply forces to rotate the inner ball within the socket to point the pointing axis;
a position measurement device configured to determine a rotational position of the inner ball with respect to the platform; and
a relay optics system in an optical path of the optical beam between the back optical aperture and the directional electro-optic element to relay the optical beam from the back optical aperture to the electro-optic element, said relay optics system comprising,
a first two-axis steering element that is positioned and sized to cover any beam formed from the back optical aperture across the range of gimbal motion; and
a second two-axis steering element mounted to the platform; and
a controller configured to drive the first and second steering elements;
wherein said controller is responsive to the rotational position of the inner ball to drive the first steering element to steer the optical beam passing through the back optical aperture into the second two-axis steering element and to drive the second two-axis steering element to tilt the optical beam to align light along a central axis of the electro-optic element substantially with the central axis of the front optical aperture on the inner ball.

2. The ball joint gimbal electro-optic system of claim 1 , wherein there is no other physical element between the inner ball and the socket or there is a bearing between the inner ball and socket.

3. The ball joint gimbal electro-optic system of claim 1 , wherein the first two-axis steering element is mounted on the platform, off-gimbal.

4. The ball joint gimbal electro-optic system of claim 1 , wherein the first two-axis steering element is mounted on the inner ball, on-gimbal.

5. The ball joint gimbal electro-optic system of claim 1 , wherein the controller is configured to drive the first steering element to pre-compensate for wander of an input aperture of the second steering element as the steering of the second steering element changes.

6. The ball joint gimbal electro-optic system of claim 1 , further comprising:
an alignment measurement element configured to measure residual misalignment of the optical path through the first and second steering elements between the central axis of the front optical aperture and an axis of the directional electro-optic element, said controller responds to the residual misalignment to drive the first and second two-axis steering elements to reduce the residual misalignment.

7. The ball joint gimbal electro-optic system of claim 1 , wherein the position measurement device comprises a non-contacting position measurement device.

8. The ball joint gimbal electro-optic system of claim 1 , wherein the motor comprises at least first and second ultrasonic drive motors placed in direct contact with the inner ball to apply rotational forces about control points along first and second orthogonal axes.

9. The ball joint gimbal electro-optic system of claim 1 , wherein the motor comprises a spherical planar motor having a plurality of two-dimensional drive elements configured to apply non-contacting electro-magnetic forces in planes tangential to the inner ball at at least two control points on different positions of a surface of the inner ball and not at opposite ends of a line through the center of the inner ball in commanded two-dimensional directions to rotate the inner ball within the socket to point the pointing axis.

10. The ball joint gimbal electro-optic system of claim 3 , wherein there are no electrically powered components mounted on-gimbal.

11. The ball joint gimbal electro-optic system of claim 4 , wherein the first two-axis steering element comprises roll-nod prisms.

12. The ball joint gimbal electro-optic system of claim 4 , further comprising:
a non-contacting power source configured to power the first two-axis steering element on the inner ball; and
a non-contacting data path from the controller on the platform to the inner ball to provide control data to drive the first two-axis steering element.

13. The ball joint gimbal electro-optic system of claim 6 , wherein the alignment measurement element comprises an optical auto-collimator folded in to share the optical path between the directional electro-optic element and the front aperture, passing through the first and second steering elements and into a reflector on the inner ball, and configured to measure the misalignment between the pointing axis and the axis of the directional electro-optic element.

14. The ball joint gimbal electro-optic system of claim 6 , also comprising an angle rate sensor mounted on the inner ball, wherein the controller is configured to drive at least one of said first and second two-axis steering elements based upon a signal from the alignment measurement element and the rate sensor to provide Vernier stabilization for scene motion across the directional electro-optic element.

15. The ball joint gimbal electro-optic system of claim 9 , wherein said spherical planar motor comprises:
one or more rotor elements formed in the surface of the inner ball, each said rotor element comprising a two-dimensional pattern of rotor teeth;
at least two of said two-dimensional drive elements positioned adjacent to the control points on different positions of the surface of the inner ball, each said drive element comprising a two-dimensional array of controllable drive heads arranged substantially parallel to, but non-contacting, the adjacent portion of the inner ball and the two-dimensional pattern of rotor teeth;
a processor configured to determine from a pointing command and the rotational position of the ball the energization of the drive heads within each drive element that act upon the adjacent rotor teeth to produce commanded two-dimensional forces in planes tangent to the inner ball substantially at the at least two control points to rotate the inner ball within the socket to point the pointing axis; and
a motor controller configured to apply the determined energization to the drive heads.

16. The ball joint gimbal electro-optic system of claim 15 , wherein a center-to-center spacing of the drive heads in each drive element is less than a center-to-center spacing of the rotor teeth.

Assignees

• Raytheon Co

Inventors

• Williams Darin S

Classifications

• G02B7/005 Primary

  Motorised alignment · CPC title

• G01B11/272 Primary

  using photoelectric detection means · CPC title

• G02B7/1821

  for rotating or oscillating mirrors · CPC title

• G02B26/08 Primary

  for controlling the direction of light (in light guides G02B6/35) · CPC title

• F41G7/2293

  using electromagnetic waves other than radio waves · CPC title