Structured illumination surface profiling and ranging systems and methods

• US 4,948,258 A
• Filed: 06/27/1988
• Issued: 08/14/1990
• Est. Priority Date: 06/27/1988
• Status: Expired due to Fees

• Current Assignee: Harbor Branch Oceanographics Institution Incorporated FT Pierce FL
• Original Assignee: Harbor Branch Oceanographic Institution, Inc.
• Inventors: Caimi, Frank M.
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US07/211,586
• Time in Patent Office: 778 Days
• Field of Search: 356/1, 356/4, 356/375, 356/376, 356/354, 356/356
• US Class Current: 356/603
• CPC Class Codes: G01B 11/2441 using interferometry
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4814 of transmitters alone

Abstract

Range and/or profile of a test surface, particularly a submarine surface, are determined by passing a laser beam through a holographic grating structured to emit a divergent light beam defining a two dimensional array of dots in a predetermined pattern and projecting such beam on the test surface. A receiving device, e.g., video camera, ascertains the positions of the dots in the pattern reflected from the test surface and comparison is made of such positions relative to the positions of the respective dots previously reflected in like manner from a datum surface. The values of the displacements of test surface dots from datum surface dots are used to determine the range or orientation of the test surface relative to the grating or the profile of the test surface.

Claims

1. A structured illumination method for determining characteristics of a surface which comprises:

projecting a beam of collimated rays from a ray source along a longitudinal axis,

converting said beam into a divergent array of spaced dots of said rays in a predetermined pattern by passage of said beam through a holographic grating that intersects said longitudinal axis,

projecting at least a portion of said divergent array of spaced dots onto a test surface remote from said grating a distance of R_p +dR,

forming an image of the pattern of dots reflected from said test surface in recorder means that substantially intersects said longitudinal axis at a distance R_F +dR along said axis from said test surface, with the proviso that R_p shall not equal R_F,

projecting a similar divergent array of spaced dots onto a datum surface remote from said grating a distance of R_p,

forming an datum image of the pattern of dots reflected from said datum surface in recorder means that substantially intersects said longitudinal axis at a distance R_F along said axis from said test surface,

comparing the positions of said dots in said test image to the positions of the respective dots in said datum image to obtain values of the displacements of individual dots in said test image from the respective individual dots in said datum image, and

using said individual dot displacement values to determine one or more characteristics of said surface.

2. The method of claim 1 wherein said characteristics are the distance of said recorder means to said test surface and the orientation of said longitudinal axis relative to said test surface.

3. The method of claim 1 wherein said characteristics are the profile of said test surface.

4. The method of claim 1 wherein R_P =0.9R_F.

5. A device for determining characteristics of a surface using structured illumination which comprises:

a ray source for projecting a beam of collimated rays along a longitudinal axis,

a holographic grating that intersects said longitudinal axis for converting said beam into a divergent array of spaced dots of said rays in a predetermined pattern and project at least a portion of said divergent array of spaced dots onto a surface remote from said grating,

recorder means positioned substantially on said longitudinal axis a distance R_F +dR from said test surface different from the distance R_P +dR of said grating to said test surface for recording a test image of the pattern of dots reflected from said test surface,

means for comparing the positions of said dots in said test image to the positions of the respective dots in a preselected datum image previously reflected and recorded in like manner from a datum surface positioned at a distance R_F from said recorder means and a distance R_P from said grating to obtain values of displacements of said test image dots from the respective datum image dots, and

means using said displacement values to determine one or more characteristics of said surface.

6. The device of claim 5 wherein said characteristics are the distance of said recorder means to said test surface and the orientation of said longitudinal axis relative to said test surface.

7. The device of claim 5 wherein said characteristics are the profile of said test surface.

8. The device of claim 5 wherein R_P =0.9R_F.