Optics: measuring and testing – Material strain analysis – By light interference detector
Patent
1989-10-23
1991-04-30
Turner, Samuel
Optics: measuring and testing
Material strain analysis
By light interference detector
356345, 356360, G01B 902
Patent
active
050112805
ABSTRACT:
A test object is analyzed electronically, i.e. without the use of photographic film. The invention generates a pair of laterally-displaced images of the object which interfere with each other to produce a pattern that can be recorded without a high-resolution detector. The object is illuminated with at least partially coherent light. Reflected light from the object is directed through a birefringent material, a lens system, a polarizer, and then to an image detector, such as a video camera. The birefringent material causes non-parallel beams originating from a unique pair of points on the object to become nearly parallel, and orthogonally polarized. The polarizer modifies the polarization of the parallel beams so that they will interfere with each other. Because the intefering light beams are nearly parallel, the spatial frequency of the interference pattern is sufficiently low that the pattern can be recorded by a low-resolution detector, such as a video camera. Interference patterns due to the superposition of two laterally-displaced images of the same object are recorded while the object is in an undeformed and a deformed state. A computer compares these interference patterns and produces a resultant pattern which depicts the deformation of the test object. Because photographic film is not needed, the invention can analyze objects very rapidly. Also, since the interference pattern is derived from pairs of distinct points on the object, the invention directly provides information on strain.
REFERENCES:
patent: 3316649 (1974-06-01), Butters
patent: 3318916 (1965-11-01), Saunders
patent: 3487227 (1969-12-01), Kinzly
patent: 3532431 (1970-10-01), Bryngdahl
patent: 3626753 (1971-12-01), Aprahamian
patent: 3767308 (1973-10-01), Duffy
patent: 3829219 (1974-08-01), Wyant
patent: 3849003 (1974-11-01), Velzel
patent: 3911729 (1975-10-01), Collins
patent: 4118124 (1978-10-01), Matsuda
patent: 4125314 (1978-11-01), Haskell
patent: 4139302 (1979-02-01), Hung
patent: 4425039 (1984-01-01), Grant
patent: 4523469 (1985-06-01), Scott
patent: 4541280 (1985-09-01), Cielo
patent: 4620223 (1986-10-01), Haskell
patent: 4633715 (1987-01-01), Monchalin
patent: 4650302 (1987-03-01), Grant
patent: 4690552 (1987-09-01), Grant
patent: 4702594 (1987-10-01), Grant
Hung, "Shearography: A New Optical Method for Strain Measurement and Nondestructive Testing", Optical Engineering, May/Jun. 1982, p. 391.
"Laser Polarizers", in The Optical Industry and Systems Purchasing Directory (1982).
Hung et al, "Speckle-Shearing Interferometric Technique: a Full-Field Strain Gauge", in Applied Optics, vol. 14, No. 3, Mar., 1975, pp. 618-622.
Hung et al, "Measurement of Slopes of Structural Deflections by Speckle-Shearing Interferometry", in Experimental Mechanics, vol. 14, No. 7, 7/74.
Balas, "Some Applications of Experimental Analysis of Models and Structures" in Experimental Mechanics, Mar., 1967, pp. 127-139.
Nakadate et al, "Digital Speckle-Pattern Shearing Interferometry", Applied Optics, vol. 19, No. 24, 12/15/80, pp. 4241-4246.
Eilberg William H.
Turner Samuel
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