Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1992-06-15
1993-10-26
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356 355, 356345, 73800, G01B 902
Patent
active
052570894
ABSTRACT:
An optical head for a shearography system includes any standard TV camera lens 56, such as a wide-angle lens, which views a region of a test object 50 that is illuminated by coherent light 52. The lens 56 creates an image at an image plane where a field lens 80 is located. The field lens 80 redirects the light so as to allow substantially all the light of the image to pass through a first relay lens 86, thereby projecting the image with uniform brightness, i.e, no vignetting. The lens 86 provides collimated light 88,90 to a shearing element, such as a Michelson interferometer, comprising a beamsplitter 92 and two mirrors 94,96. Use of collimated light minimizes aberrations typically caused by beamsplitters. Collimated output light 102,104 from the shearing element is refocused onto a TV camera sensor plate 112 where the sheared interfered image is electronically detected for processing and viewing. The invention allows the shearing element to be sized independent of the size of the region on the object 50 to be imaged.
REFERENCES:
patent: 3816649 (1974-06-01), Butters et al.
patent: 4887899 (1989-12-01), Hung
patent: 5094528 (1992-03-01), Tyson, II et al.
Y. Y. Hung et al., "Measurement of Slopes of Structural Deflections by Speckle-shearing Interferometry", Experimental Mechanics, Jul. 1984, pp. 281-285.
J. S. Leendertz et al., "An Image-Shearing speckle-pattern interferometer for measuring bending moments", Journal of Physics E: Scientific Instruments, vol. 6, 1973, pp. 1107-1110.
DePardo Gerald L.
Kim Robert
Turner Samuel A.
United Technologies Corporation
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