Showing papers by "Pietro Ferraro published in 1997"

Reflective grating interferometer: a versatile and simple system for education in optics

Abstract: Recently has been developed a two component interferometer that has several advantages when used for eduction and training in optics. It is a wavefront division interferometer based on the use of a reflective grating that is used for recombination of two portion of one plane wavefront, obtained using a low cost parabolic mirror of commercial telescopes. The alignment operation is performed setting the mirror and the reflective grating at 90 degree each other. Interference fringe pattern are presented in all the volume in front the reflective grating interferometer and a screen or a CCD camera without lens can be used to visualize fringes. The interferometer being made of only two components is also very stable. Fringe pattern spacing and orientation can be simply changed rotating the mirror on a vertical axis or tilting it respectively. The fact that mirror and the grating are adjacent has some advantages on the pedagogical side because students can understand better how relative movements of the two components affect the changes in the fringe pattern. This interferometer is used not only to study interferometry but can be used also to study geometrical optics using the fringe pattern as a grid to perform Ronchi test. In such a way it is possible to conduct investigation on aberrations of optical components (Spherical, astigmatism and coma) or determine focal lengths lenses by using Moire effect. In conclusion the RGI is a system that comprises, at same time, in its operation different areas of the optics: interferometry, diffraction, wavefront picture of light, geometrical optics, testing. Examples of application for education purposes are described.

Evaluation of rigid rotations in flexural loading tests by holographic interferometry

Abstract: The authors develop a simple method based on holographic interferometry for determining the Poisson's ratio and the Young's modulus for a specimen subjected to four-point flexural testing that evaluates and eliminates the effects of the unwanted rigid-body rotations. In the experimental setup, they use an additional mirror to record the underside and the front surface of the specimen simultaneously. The theoretical analysis shows that it is possible to correlate the holographic fringe pattern of the underside and front surface of the sample. Each rotation angle can be evaluated by counting the fringe orders between two points chosen on the two fringe patterns.