Deformation measuring method and device using cross-correlation

Details Deformation measuring method and device using cross-correlation Deformation measuring method and device using cross-correlation

1989-06-19

1990-10-30

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

356376, G01V 904

Patent

active

049670930

ABSTRACT:
In a deformation measuring method and device in which an object is irradiated with a laser beam before and after deformation of the object to obtain speckle patterns, the speckle patterns thus obtained are photoelectrically converted into electrical signals, and the cross-correlation function between the speckle patterns is calculated using the electrical signals to obtain displacement of the speckle pattern on the basis of the shift of position of the extreme value of the mutual-correlation function and to determine the amount of deformation of the object from the displacement of the speckle pattern, (1) the reference speckle pattern data for calculation of the cross-correlation function is renewed when the extreme value of the cross-correlation function is lower in level than a predetermined value or when the position of the extreme value is out of a predetermined range, or (2) the reference speckle pattern data is renewed when the extreme value of the cross-correlation function is lower in level than a predetermined value and a calculation range for calculating the cross-correlation function is shifted when the position of the extreme value is out of a predetermined range.

REFERENCES:
patent: 3617625 (1971-11-01), Redpath
patent: 4539651 (1985-09-01), Ludman
patent: 4636069 (1987-01-01), Balasubramanian
patent: 4641972 (1987-02-01), Halioua et al.
patent: 4657393 (1987-04-01), Stern
patent: 4678920 (1987-07-01), Iadipaolo et al.
patent: 4802759 (1989-02-01), Matsumoto et al.
"Laser Science Research," No. 6, pp. 152-154 (1984).
"Latest Precision Measurement Technology," Jul. 1, 1987, pp. 241-244.

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