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Vincent Toal

Publications and source records attributed to Vincent Toal.

4 recordsLinked to original sources
PubMed2004

Simple phase-shifting lateral shearing interferometer.

A phase-shifting electronic speckle pattern shearing interferometer with a very simple shearing device is proposed. Two partially reflective glass plates are used to introduce the shear in this new interferometer. The reflection coefficients of the coatings on the two plates are 0.3 and 0.7. The distance between the two glass plates controls the size of the shear. The proposed new interferometric system is simple, flexible, and low cost.

Journal Article↗
PubMed2004

Investigation of the diffusion processes in a self-processing acrylamide-based photopolymer system.

Results from the investigation of the diffusion processes in a dry acrylamide-based photopolymer system are presented. The investigation is carried out in the context of experimental research on optimization of the high-spatial-frequency response of the photopolymer. Tracing the transmission holographic grating dynamics at short times of exposure is utilized to measure diffusion coefficients. The results reveal that two different diffusion processes contribute with opposite sign to the refractive-index modulation responsible for the diffraction grating buildup. Monomer diffusion from dark to bright fringe areas increases the refractive-index modulation. It is characterized with diffusion constant D0 = 1.6 x 10(-7) cm2/s. A second diffusion process takes place during the recording. It decreases the refractive-index modulation and we ascribe it to diffusion of short-chain polymer molecules or radicals from bright to dark fringe areas. The estimated diffusion coefficient for this process is D0 = 6.35 x 10(-10) cm2/s. The presence of the second process could be responsible for the poor high-spatial-frequency response of the investigated photopolymer system. Comparison with the diffusion in photopolymer systems known for their good response at high spatial frequencies shows that both investigated diffusion processes occur in a much faster time scale.

Journal Article↗
PubMed2004

Electronic speckle pattern shearing interferometer with a photopolymer holographic grating.

A photopolymer holographic grating is used to produce the two sheared images in an electronic speckle pattern shearing interferometer. A ground glass screen following the grating eliminates unwanted diffraction orders and removes the requirement for the CCD camera to resolve the diffraction grating's pitch. The sheared images on the ground glass are further imaged onto the CCD camera. The fringe pattern contrast was estimated to be above 90%. A validation of the system was done by comparing the theoretical phase difference distribution with the experimental data from the three-point bending test.

Journal Article↗