Showing papers by "Pietro Ferraro published in 2001"

Whole optical wavefields reconstruction by digital holography.

Abstract: In this paper, we have investigated on the potentialities of digital holography for whole reconstruction of wavefields. We show that this technique can be efficiently used for obtaining quantitative information from the intensity and the phase distributions of the reconstructed field at different locations along the propagation direction. The basic concept and procedure of wavefield reconstruction for digital in-line holography is discussed. Numerical reconstructions of the wavefield from digitally recorded in-line hologram patterns and from simulated test patterns are presented. The potential of the method for analysing aberrated wave front has been exploited by applying the reconstruction procedure to astigmatic hologram patterns.

Correct-image reconstruction in the presence of severe anamorphism by means of digital holography.

Abstract: It is demonstrated for the first time to the authors’ knowledge that digital holographic image reconstruction can be applied to correction of image reconstruction in the presence of severe anamorphism and aberrations. It is shown that anamorphism and aberrations can be taken into account and compensated for separately to yield a correct-image reconstruction. Anamorphism and aberrations are introduced by a holographic recording system based on a reflective grating interferometer (RGI). The strong anamorphic behavior of the RGI prevents reconstruction of a correct image unless that behavior is compensated for in the process of numerical holographic reconstruction.

Digital holographic interferometry for characterization of transparent materials

Abstract: Accurate measurement of the refractive index of solids is of great importance in various field of industrial processes. We present and discuss a method based on digital holographic interferometry for measuring refractive indices of transparent materials. Two recorded digital holograms are added producing a digital double exposure hologram. The numerical reconstruction of the interferogram intensity enables to determine the index of refraction of the sample under investigation. Advantages and limitations of the prosed approach are discussed.

Noise-immune interference fringe analysis by modification of local intensity histogram and 2D Fourier transform method

Abstract: A noise-immune method of phase retrieval of single moire interferometric fringe pattern is presented and discussed. The method is shown to provide accurate recovering of the phase information by combined method based on modification of local histogram of the fringe intensity and two dimensional Fourier transform of enhanced moire fringe pattern. The principle of the method is described and the experimental results of moire interferometric measurements with submicron sensitivity of the in-plane displacement fields of thick carbon fiber/PEEK composite laminates are presented as example of application of the technique.

Two-beam interferometer for measuring aberrations of optical components with axial symmetry.

Abstract: We present a concept of interferometric testing, believed to be novel, that can be applied to measuring aberrations of optical components that have rotational symmetry. The optical configuration uses two coherent, collimated wave fronts that are tilted to impinge upon the optical component being tested such that one beam is on axis and the other is off axis. For small tilt angles the two aberrated wave fronts can be considered to be carrying the same aberrations. Furthermore, the off-axis beam is displaced along a direction orthogonal to the optical axis of the component. Interference between the two aberrated wave fronts produces a fringe pattern that is similar to a lateral shear interference pattern. Moire fringes are obtained by spatial beating of the interference pattern with a CCD TV camera array. Under such conditions it is possible to subtract most of the linear carrier that is intrinsically present in the resultant fringe pattern owing to the large defocus aberration and tilt.

Two-beam shearing interferometric method for testing a conical lens

Abstract: We present a novel interferometric method for testing refractive conical lenses. The optical configuration requires only two mutually coherent plane wave fronts transmitted through the optical component under test. It can be interpreted as reversal shear interferometric technique. The method can also be considered as an interferometric fringe projection method. Measurements have been realized for determining the base angle of the refractive cone under test and the aberrations introduced.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.