Fixed-Source Array Test Station for Calibration of a Semi-Active Laser (SAL) Seeker

• US 20120143551A1
• Filed: 11/16/2010
• Published: 06/07/2012
• Est. Priority Date: 11/16/2010
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Streuber, Casey T., Burkland, Michael K., Tvedt, Kristofer E.
• Granted Patent: US 8,392,143 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: F41G 7/002 target simulators
• CPC Class Codes: F41G 7/226 Semi-active homing systems, i.e. comprising a receiver and involving auxiliary illuminating means, e.g. using auxiliary guiding missiles
• CPC Class Codes: F41G 7/2293 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 3/7803 Means for monitoring or calibrating

Abstract

A fixed-source array test station provides a cost-effective high-throughput test bed for testing optical sensors that require stimulus at fixed angular positions. A SAL seeker requires stimulus at fixed angular position across its FOV to calibrate its spatial transfer function (STF). An array of fixed collimated sources at different angular positions is aligned so that their beams overlap the entrance pupil of the sensor under test. Each source may comprise an inexpensive light emitting diode (LED) or vertical cavity surface emitting laser (VCSEL) and collimator. To simplify alignment the sources may be positioned on and perpendicular to the surface of a sphere with the seeker'"'"'s entrance pupil located at the center of the sphere. The sources are activated in accordance with an activation profile in order to calibrate or otherwise test the sensor.

Claims

1. A test station for calibrating a semi-active laser (SAL) seeker including a SAL detector, comprising:

a fixture for mounting the SAL seeker, said seeker having an entrance pupil to detect optical energy over a field of view (FOV) and focus the optical energy into a spot on the SAL detector;

an array of fixed collimated optical sources that generate respective temporally pulsed optical beams, said sources positioned over the FOV of the seeker and co-aligned so that their respective optical beams overlap the entrance pupil of the seeker;

a memory that stores a first source activation profile to generate a transfer function for the SAL detector, said transfer function mapping a spatial displacement Δ

X and Δ

Y in orthogonal axes of a centroid of the spot to azimuth and elevation angles for the source of the spot;

a controller responsive to the first source activation profile to activate the sources one at a time in a phase delayed manner to implement the activation profile; and

a computing device responsive to the measured spatial displacement Δ

X and Δ

Y for each source as the source is activated to create a table entry for the transfer function in a calibration table that maps the measured Δ

X and Δ

Y to the known azimuth and elevation angles of the activated source.

2. The test station of claim 1, wherein said optical source comprises a Light Emitted Diode (LED), a Vertical Cavity Surface Emitting Laser (VCSEL) or a fiber-coupled laser.

3. The test station of claim 2, wherein said LED or VCSEL comprises electronics to vary the pulse width so that the wavelength of the beam is in a lower noise region of the SAL detector.

4. The test station of claim 2, wherein said LED or VCSEL emit a diverging beam, said optical source comprising a single optical component that collimates a portion of the diverging beam of the size of the entrance pupil.

5. The test station of claim 4, wherein the single optical component comprises a single lens element.

6. The test station of claim 5, wherein said single lens element comprises a plano-convex lens.

7. The test station of claim 1, wherein said fixed collimated optical sources are positioned in a two-dimensional array over the FOV, said fixture on which the SAL seeker is mounted is fixed during calibration of the SAL seeker.

8. The test station of claim 1, wherein said fixed collimated optical sources are positioned in a one-dimensional array over the FOV, said fixture on which the SAL seeker is mounted rotates about an axis during calibration of the SAL seeker.

9. The test station of claim 1, wherein said fixed collimated optical sources are positioned on and substantially perpendicular to the surface of a sphere in which the entrance pupil of the SAL seeker is positioned at substantially the center of the sphere.

10. The test station of claim 1, wherein said controller activates the sources with a phase delay of less than 100 milliseconds.

11. The test station of claim 10, wherein the average test time per source is less than 100 milliseconds.

12. The test station of claim 1, wherein said memory stores a second activation pattern to simulate a targeting scenario, said targeting scenario requiring the sequential activation of at least a plurality of the sources with a phase delay of less than 100 micro seconds, said controller responsive to the second activation pattern to activate the sources to simulate the targeting scenario, said computing device responsive to the measured spatial displacement Δ

X and Δ

Y for each source to either verify whether the SAL seeker performs as designed or to characterize how the SAL seeker performs.

13. The test station of claim 1, wherein said detector is mounted on a gimbal in said SAL seeker, said memory stores a second activation pattern that activates the sources in a phase delayed manner, said controller responsive to said second activation pattern to activate the sources in the phase delayed manner in concert with the rotation of the gimbal to center each source on the SAL detector boresight.

14. The test station of claim 1, wherein each said source comprises a SAL source and a miniature blackbody emitter, wherein said SAL Seeker comprises an IR detector that is mounted on a gimbal in said SAL seeker, said memory stores a second activation pattern that activates the emitters in a phase delayed manner, said controller responsive to said second activation pattern to activate the emitters in the phase delayed manner in concert with the rotation of the gimbal to center each emitter on the IR detector boresight.

15. The test station of claim 1, wherein each said source comprises a SAL source and a miniature blackbody emitter, wherein said SAL seeker comprises an IR detector, said memory stores a second activation pattern for the IR detector and SAL detector to calibrate IR to SAL alignment, said controller activating the emitters to implement the activation profile, said computing device responsive to data from said IR and SAL detectors to calculate a calibration of the IR to SAL alignment.

16. The test station of claim 1, wherein the source comprises a SAL source and a miniature blackbody emitter, wherein said SAL seeker comprises an IR detector, said memory stores a second activation pattern for the IR detector that turns multiple emitters on simultaneously to calibrate IR distortion, said controller activating the emitters to implement the activation profile, said computing device responsive to data from said IR detectors to calculate distortion of the IR detector across the FOV.

17. A test station for calibrating a semi-active laser (SAL) seeker including a SAL detector, comprising:

a fixture for mounting the SAL seeker, said seeker having an entrance pupil to detect optical energy over a field of view (FOV) and focus the optical energy into a spot on the SAL detector;

an array of fixed collimated optical sources that generate respective temporally pulsed optical beams, said sources positioned over the FOV of the seeker on and substantially perpendicular to the surface of a sphere and co-aligned so that their respective optical beams overlap the entrance pupil of the seeker positioned at the center of the sphere, each said source comprising an LED or VCSEL that generates a pulsed diverging beam and a single optical-component that collimates the pulsed beam;

a memory that stores a first source activation profile to generate a transfer function for the SAL detector, said transfer function mapping a spatial displacement Δ

X and Δ

Y in orthogonal axes of a centroid of the spot to azimuth and elevation angles for the source of the spot;

a controller responsive to the first source activation profile to activate the sources one at a time in a phase delayed manner to implement the activation profile, said phase delay between activation of subsequent sources being less than 5 milliseconds; and

a computing device responsive to the measured spatial displacement Δ

X and Δ

Y for each source as it is activated to create a table entry for the transfer function in a calibration table that maps the measured Δ

X and Δ

Y to the known azimuth and elevation angles of the activated source, the average time per table entry being less than 100 milliseconds.

18. A test station for an optical sensor, comprising:

a stage for mounting the optical sensor, said optical sensor having an entrance pupil to detect optical energy over a field of view;

an array of fixed collimated optical sources distributed over the FOV of the sensor and co-aligned so that their respective temporally pulsed optical beams overlap the entrance pupil of the sensor;

a memory that stores one or more source activation profiles to perform different tests;

a controller responsive to a source activation profile to activate the sources to implement the activation profile, said controller capable of activating subsequent sources with a phase delay of less than 5 milli seconds; and

a computer that selects the source activation profile for a particular test, retrieves it from memory and provides it to the controller and is responsive to sensor data recorded for each source to process the data to perform the test, on average said computer processing the data per source in less than 100 milli seconds.

19. The test station of claim 18, wherein said optical source comprises a Light Emitted Diode (LED), a Vertical Cavity Surface Emitting Laser (VCSEL), a fiber-coupled laser or a miniature blackbody emitter.

20. The test station of claim 18, wherein said fixed collimated optical sources are positioned in a two-dimensional array over the FOV, said stage on which the optical sensor is mounted is fixed during testing.

21. The test station of claim 18, wherein said fixed collimated optical sources are positioned on and substantially perpendicular to the surface of a sphere in which the entrance pupil of the optical sensor is positioned at substantially the center of the sphere.

22. The test station of claim 18, wherein said control activates at least a plurality of sources with a phase delay of less than 5 milliseconds to implement the activation profile.