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# Detecting Surface Deformities

IP.com Disclosure Number: IPCOM000074732D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 44K

IBM

## Related People

Hammond, CH: AUTHOR [+2]

## Abstract

The system shown in Fig. 1 measures deviation from flatness of a surface. These deformities might be due to faults in the surface or to shaping of the surface by its environment.

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Detecting Surface Deformities

The system shown in Fig. 1 measures deviation from flatness of a surface. These deformities might be due to faults in the surface or to shaping of the surface by its environment.

In operation, surface 10 is illuminated by diffused light from source 12 behind a grid mask 14. Reflected light from the surface 10 is in turn reflected by a mirror 16 to a detector 18. Detector 18 will see the image of the grid 14 as deformed by deformities in the surface 10. The deformity of the grid as seen by the detector 18 is analyzed to determine the actual deformity of the surface 10. Detector 18 might typically be a camera to photograph the deformed grid pattern. The photographed grid pattern is mathematically analyzed on a computer to determine the actual deformity of the surface 10. A mathematical model for the analysis is shown in Fig. 2.

In Fig. 2, a portion of the grid 14 is depicted. This grid lies in the plane represented by line 20. The detector is represented by a camera, which is in turn represented by a lens 22 and a film plane 24. The image of the grid on the film plane is represented by grid pattern 26. Surface 10 is represented by the irregular line correspondingly numbered.

Initially, the geometry of the camera and the grid are set up so as to define the distances a, b, c, and the angle alpha. Angle beta is therefore defined as the bi-section of the angle alpha. Angle theta is defined by the mounting angles of the grid. Knowing the an...