A real-time two-color laser speckle-shift strain-measurement system based on the technique of Yamaguchi is utilized to detect 1D strain in small diameter structural fibers. These measurements were performed using the dual-wavelength light output from an Argon Ion laser as the light source, coupled into two separate single-mode optical patchcords. The output of each optical patchcord is incident on the test specimen experiencing strain. This structural fiber is pulled in one direction while shifting speckle patterns reflected off the fiber are detected and strain is calculated in real-time (up to 150 frames/second). Two linear CCD arrays detect the speckle pattern with image processing performed by a hardware correlator. The strain resolution of this device is 20 (mu) (epsilon) . Measurements were obtained at room temperature and attempts were made at elevated temperatures. This system is designed to be compact and robust and does not require surface preparation of the structural fibers.
A real-time two-color laser speckle-shift strain measurement system based on Yamaguchi's technique was designed, built, and tested at room temperature. This non-contact 1D system detects surface strain in a structural fiber as it is pulled in a tensile test machine. Interference or speckle patterns from the laser illuminated fiber test specimen are recorded. As the fiber is pulled, its speckle patterns shift in proportion to the strain, translation, and rotation components of the sample deformation. Shifting speckle patterns are detected at real-time rates using 2 linear CCD arrays with image processing performed by a hardware correlator. Surface strain detected in fibers with diameters on the order of 100 micrometers can be resolved to 19 microstrain. This system was designed to be compact and robust and generally does not require surface preparation of the structural fibers.
A two color laser speckle shift strain measurement system based on the technique of Yamaguchi was
designed. The dual wavelength light output from an Argon Ion laser was coupled into two separate
single-mode optical fibers (patchcords). The output of the patchcords is incident on the test specimen
(here a structural fiber). Strain on the fiber, in one direction, is produced using an Instron 4502. Shifting
interference patterns or speckle patterns will be detected at real-time rats using 2 CCD cameras with
image processing performed by a hardware correlator. Strain detected in fibers with diameters from 21
microns to 143 microns is expected to be resolved to 15 pe. This system was designed to be compact
and robust and does not require surface preparation of the structural fibers.
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