CONFOCAL OPTICAL PROTRACTOR

• US 20200132443A1
• Filed: 10/26/2018
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: RUMALA, YISA S.
• Granted Patent: US 10,670,391 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01B 9/00 Measuring instruments characterised by the use of optical techniques
• CPC Class Codes: G01C 1/00 Measuring angles
• CPC Class Codes: G01D 5/266 by interferometric means G01D5/353 takes precedence
• CPC Class Codes: G01P 3/36 Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light G01P3/68 takes precedence; gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams G01C19/64
• CPC Class Codes: G02B 17/004 Systems comprising a plurality of reflections between two or more surfaces, e.g. cells, resonators multipass arrangements for optical cuvettes G01N21/031; laser resonators H01S3/05
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 27/0927 Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
• CPC Class Codes: G02B 5/04 Prisms
• CPC Class Codes: H01S 3/08045 Single-mode emission

Abstract

A confocal optical protractor for simultaneously measuring roll angle, pitch angle and yaw angle of an element that includes a tunable laser source generating a laser beam and an SPPR device responsive to the laser beam. The protractor also includes a beam splitter receiving and splitting an output beam from the SPPR device, and a lens being responsive to and projecting the split beam onto the element and being responsive to a reflected beam from the element. The protractor further includes a measurement detector responsive to the reflected beam from the element, where the reflected beam is imaged by the lens onto the measurement detector, and a processor receiving and processing image data from the measurement detector and generating the pitch, yaw and roll angles from the data, where the image data includes an orientation of an vortex intensity pattern in the split beam.

Claims

1. An optical system for measuring pitch, yaw and roll angles of an element, said system comprising:

a tunable laser source generating a laser beam;

a spiral phase plate resonator (SPPR) device responsive to the laser beam, said SPPR device including opposing reflective surfaces that reflect the laser beam back and forth in the device, wherein one of the reflective surfaces includes a spiral step index that causes multiple reflected amplitudes having different phases to be combined and generate an optical vortex intensity pattern defined by the phases of the multiple amplitudes, where the intensity pattern includes a singularity and radial light peaks, said SPPR device reflecting a first beam back towards the laser source and transmitting a second beam away from the laser source;

a first beam splitter receiving and splitting either the first beam or the second beam and generating a split measurement beam;

a lens being responsive to and projecting the first split measurement beam onto the element and being responsive to a reflected beam from the element;

a measurement detector responsive to the reflected beam from the element, where the reflected beam is imaged by the lens onto the measurement detector; and

a processor receiving and processing image data from the measurement detector and generating the pitch, yaw and roll angles from the data, wherein the image data includes an orientation of the vortex intensity pattern.

2. The optical system according to claim 1 wherein the vortex intensity pattern includes one intensity peak in each of four quadrants.

3. The optical system according to claim 1 wherein the pitch angle is determined by a shift of the vortex intensity pattern in one plane, the yaw angle is determined by a shift of the vortex intensity pattern in another plane orthogonal to the one plane, and the roll angle is determined by a rotation of the vortex intensity pattern.

4. The optical system according to claim 1 further comprising a second beam splitter receiving and directing the split measurement beam to the lens, wherein the second beam splitter receives and directs the reflected beam to the measurement detector.

5. The optical system according to claim 4 further comprising a shutter through which the split measurement beam propagates from the lens to the element.

6. The optical system according to claim 5 further comprising a detector that is responsive to a split reflected beam from the second beam splitter when the shutter is closed, said detector keeping track of the orientation of the reflected beam and the intensity of the first or second beam.

7. The optical system according to claim 6 wherein the detector is a multiple pixel detector or a single pixel detector array including multiple single pixel detectors arrange in a circle.

8. The optical system according to claim 1 wherein the SPPR device is a low reflectivity device and the first beam splitter receives the first beam.

9. The optical system according to claim 8 further comprising an intensity detector responsive to a split beam from the first beam splitter, said intensity detector monitoring beam intensity.

10. The optical system according to claim 8 wherein the reflectivity of the SPPR device is about 0.04.

11. The optical system according to claim 1 wherein the SPPR device is a high reflectivity device and the first beam splitter receives the second beam.

12. The optical system according to claim 11 wherein the reflectivity of the device is about 0.5.

13. The optical system according to claim 1 wherein the SPPR device generates a reference beam transmitted through the SPPR device, said reference beam being projected onto a calibration detector for generating a reference orientation of the vortex intensity pattern.

14. The optical system according to claim 13 wherein the measurement and calibration detectors are CCD cameras.

15. An optical system for measuring pitch, yaw and roll angles of an element, said system comprising:

a tunable laser source generating a laser beam;

a spiral phase plate resonator (SPPR) device responsive to the laser beam, said SPPR device including opposing reflective surfaces that reflect the laser beam back and forth in the device, wherein one of the reflective surfaces includes a spiral step index that causes multiple reflected amplitudes having different phases to be combined and generate an optical vortex intensity pattern defined by the phases of the multiple amplitudes, where the intensity pattern includes a singularity and radial light peaks, said SPPR device reflecting a first beam back towards the laser source and transmitting a second beam away from the laser source;

a calibration detector responsive to the second beam and generating a reference orientation of the vortex intensity pattern;

a first beam splitter receiving and splitting the first beam and generating a split measurement beam;

a lens being responsive to and projecting the first split measurement beam onto the element and being responsive to a reflected beam from the element;

a measurement detector responsive to the reflected beam from the element, where the reflected beam is imaged by the lens onto the measurement detector; and

a processor receiving and processing image data from the measurement detector and the reference orientation of the vortex intensity pattern and generating the pitch, yaw and roll angles from the data, wherein the image data includes an orientation of the vortex intensity pattern, and wherein the pitch angle is determined by a shift of the vortex intensity pattern in one plane, the yaw angle is determined by a shift of the vortex intensity pattern in another plane orthogonal to the one plane, and the roll angle is determined by a rotation of the vortex intensity pattern.

16. The optical system according to claim 15 wherein the vortex intensity pattern includes one intensity peak in each of four quadrants.

17. The optical system according to claim 15 further comprising a second beam splitter receiving and directing the split measurement beam to the lens, wherein the second beam splitter receives and directs the reflected beam to the measurement detector.

18. The optical system according to claim 17 further comprising a shutter through which the split measurement beam propagates from the lens to the element.

19. The optical system according to claim 18 further comprising a detector that is responsive to a split reflected beam from the second beam splitter when the shutter is closed, said detector providing beam calibration.

20. The optical system according to claim 15 further comprising an intensity detector responsive to a split beam from the first beam splitter, said intensity detector monitoring beam intensity.

21. An optical system for measuring pitch, yaw and roll angles of an element, said system comprising:

a tunable laser source generating a laser beam;

a spiral phase plate resonator (SPPR) device responsive to the laser beam, said SPPR device including opposing reflective surfaces that reflect the laser beam back and forth in the device, wherein one of the reflective surfaces includes a spiral step index that causes multiple reflected amplitudes having different phases to be combined and generate an optical vortex intensity pattern defined by the phases of the multiple amplitudes, where the intensity pattern includes a singularity and radial light peaks, said SPPR device outputting a vortex beam;

a beam splitter receiving and splitting the vortex beam into a measurement beam and a calibration beam;

a calibration detector responsive to the calibration beam and generating a reference orientation of the vortex intensity pattern;

a lens being responsive to and projecting the measurement beam onto the element and being responsive to a reflected beam from the element;

a measurement detector responsive to the reflected beam from the element, where the reflected beam is imaged by the lens onto the measurement detector; and

a processor receiving and processing image data from the measurement detector and the reference orientation of the vortex intensity pattern and generating the pitch, yaw and roll angles from the data, wherein the image data includes an orientation of the vortex intensity pattern, and wherein the pitch angle is determined by a shift of the vortex intensity pattern in one plane, the yaw angle is determined by a shift of the vortex intensity pattern in another plane orthogonal to the one plane, and the roll angle is determined by a rotation of the vortex intensity pattern.