Imaging system and method using partial-coherence speckle interference tomography

• US 8,780,182 B2
• Filed: 03/31/2010
• Issued: 07/15/2014
• Est. Priority Date: 03/31/2010
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Byren, Robert W.
• Primary Examiner(s): Holder, Anner
• Assistant Examiner(s): Mung, On S
• Application Number:
  US12/751,298
• Publication Number:
  US 20110242285A1
• Time in Patent Office: 1,567 Days
• Field of Search: 348/47, 348/124, 348/100, 348/325, 348/511, 382/100, 382/124, 382/325, 356/511
• US Class Current: 348/47
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 9/02009 by using two or more low coherence lengths using different or varying spectral width
• CPC Class Codes: G01B 9/02096 detecting a contour or curvature
• CPC Class Codes: G06V 10/10 Image acquisition document image scanning and transmission H04N1/00; control of digital cameras H04N23/60
• CPC Class Codes: G06V 40/161 Detection; Localisation; Normalisation

Abstract

A system for generating an image of contoured surface includes a light source that is configured to project an electromagnetic radiation beam onto the contoured surface, wherein the projected beam generates first radiation reflected from a first portion of the contoured surface to form a speckle pattern, and second radiation reflected from a second portion of the contoured surface which is substantially uniform in intensity. The reflected first and second reflected radiation is received by an optical detector, and may be processed. The processing is configured to (1) generate a plurality of images from the first and second reflected radiation, with each image being generated using different coherence length electromagnetic radiation from the light source, and (2) generate a 3-D image of the contoured surface from the plurality of images. Methods for generating a 3-D image of a contoured surface are also disclosed.

Claims

1. A system for imaging a contoured surface comprising:

a light source configured to project a beam of partially coherent electromagnetic radiation onto the contoured surface, wherein the projected beam-generates first radiation scattered from a first portion of the contoured surface to form a speckle pattern, and second radiation scattered from a second portion of the contoured surface to form a pattern which is substantially uniform in intensity;

an optical detector configured to receive the first and second scattered radiation from the contoured surface, wherein a coherence length of the light source is greater than a depth of the first portion of the contoured surface and less than a depth of the second portion of the contoured surface, when imaged within a single pixel of the optical detector; and

a processor configured to (1) generate a plurality of images from the first and second scattered radiation, with each image being generated using different coherence length electromagnetic radiation from the light source, and (2) generate a 3-D image of the contoured surface from the plurality of images.

2. The system according to claim 1, wherein the light source is a pulsed laser.

3. The system according to claim 1, wherein the light source is a partially coherent laser.

4. The system according to claim 1, wherein the light source is configured to project partially coherent electromagnetic radiation that is generally undetectable by a human eye under ambient conditions.

5. The system according to claim 1, wherein a coherence length of the light source may be selectable in a range from a fraction of a millimeter to more than a centimeter.

6. The system according to claim 1, further comprising:

a second light source configured to project a second beam of partially coherent electromagnetic radiation beam onto the contoured surface, wherein the second projected beam generates third radiation scattered from the first portion of the contoured surface to form a speckle pattern, and fourth radiation scattered from the second portion of the contoured surface to form a pattern which is substantially uniform in intensity pattern; and

a second optical detector configured to receive the third and fourth scattered radiation from the contoured surface.

7. The system according to claim 6, wherein the processor is configured to combine an image of the first and second scattered radiation and the image of the third and fourth scattered radiation.

8. The system according to claim 7, wherein the processor uses frame subtraction so as to substantially eliminate imagery features from combined image of said second portion of the contoured surface.

9. The system according to claim 6, wherein the second beam has a different wavelength than the first electromagnetic radiation beam.

10. The system according to claim 1, wherein a coherence length of the light source is raised or lowered approximately 1 mm for each image.

11. A method for imaging a contoured surface, comprising:

generating a plurality of images by;

projecting a beam of partially coherent electromagnetic radiation onto the contoured surface, wherein the projected beam generates first radiation scattered from a first portion of the contoured surface to form a speckle pattern, and second radiation scattered from a second portion of the contoured surface to form a pattern which is substantially uniform in intensity; and

receiving, with an optical detector, the first and second scattered radiation from the contoured surface, wherein each image is generated using different coherence length electromagnetic radiation from the light source, wherein a coherence length of the light source is greater than a depth of the first portion of the contoured surface and less than a depth of the second portion of the contoured surface, when imaged within a single pixel of the optical detector, and

generating, with a processor, a 3-D image of the contoured surface from the plurality of images.

12. The method according to claim 11, further comprising generating the electromagnetic radiation with a pulsed laser.

13. The method according to claim 11, wherein the projected partially coherent electromagnetic radiation is a partially coherent laser beam.

14. The method according to claim 11, wherein the projected partially coherent electromagnetic radiation is generally undetectable by a human eye under ambient conditions.

15. The method according to claim 11, wherein a coherence length of the light source may be selectable in a range from a fraction of a millimeter to more than a centimeter.

16. The method according to claim 11, further comprising:

projecting a second beam of partially coherent electromagnetic radiation onto the contoured surface, wherein the projected beam generates third radiation scattered from the first portion of the contoured surface to form a speckle pattern, and second radiation scattered from the second portion of the contoured surface to form a pattern which is substantially uniform in intensity; and

receiving, with a second optical detector, the third and fourth scattered radiation from the contoured surface.

17. The method according to claim 16, further comprising:

processing the third and fourth scattered radiation, with a processor, to generate an image.

18. The method according to claim 17, wherein the processing comprising combining an image of the first and second scattered radiation and the image of the third and fourth scattered radiation.

19. The method according to claim 18, wherein the processing comprises frame subtraction so as to substantially eliminate imagery features from combined image of said second portion of the contoured surface.

20. The system according to claim 16, wherein the second partially coherent electromagnetic radiation beam has a different wavelength than the first partially coherent electromagnetic radiation beam.