Biomedical subjects

Eugenio Garbusi

Publications and source records attributed to Eugenio Garbusi.

9 recordsLinked to original sources

PubMed2005

Phase-shifting (Sagnac) interferometer with external phase control.

A novel ring configuration for phase-shifting interferometry with external phase-shifting control is presented. The device is a polarization (ring) interferometer, in which the reference and test arms are parts of the same collimated beam. The key point is to manage the polarization of the light such that orthogonal linear polarizations describe counterpropagating paths in the ring interferometer. The phase shift between the two waves is externally controlled with a Pockels cell, which permits fast phase modulation without the need for moving parts inside the interferometer.

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PubMed2005

Harmonic suppression and defect enhancement using Schlieren processing.

The Schlieren technique is a well-known coherent processing method that is usually applied to the visualization of phase objects. In this paper, we demonstrate that, when the Schlieren processing is applied to a light wave modulated in amplitude and possessing some periodicity, the harmonic contents of the resultant image decreases (i.e., the higher harmonics are suppressed). Also, we show that, when the amplitude-modulated (periodic) light wave possesses faults, the Schlieren processing produces an enhancement of the faults relative to the periodic carrier. This technique can be applied to defect detection in periodic structures such as photomasks used for LCD panels, integrated-circuit masks, or semiconductor wafers.

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PubMed2005

Spatial self-filtering with polarizer sheets.

A method for phase visualization and edge enhancement by spatial self-filtering by use of a polarizer sheet in the Fourier plane of an optical processor is described. Light absorbed by the polarizer sheet induces a thermal lens, which, in turn, produces selective action on certain spatial frequencies of the image to be processed. Some experiments that demonstrate the self-filtering action of the proposed system are presented.

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PubMed2004

Linear focusing by a plane grating with curved grooves.

We study the field diffracted by a plane grating with curved (parabolic) grooves. We will demonstrate that when a monochromatic plane wave is incident on a grating with parabolic grooves the diffracted field has a focal line whose position depends on the curvature radius of the parabolas and the incidence angle of the light onto the grating. The effect described has potential applications in grating-based devices for focusing light without requiring any additional optics.

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PubMed2004

Comment on "Phase-shift extraction and wave-front reconstruction in phase-shifting interferometry with arbitrary phase steps".

We comment on the recent Letter by Cai et al. [Opt. Lett. 28, 1808 (2003)] in which an approach to phase-shifting interferometry with arbitrary phase steps was proposed. Cai et al. based their method of phase shifting on the idea that the intensities of the reference and object beams can be measured previously, which actually makes the whole posterior phase-shifting procedure absolutely unnecessary. Their method is also based on the statement that the phase of the Fresnel diffraction pattern of a test object if generally a spatially random distribution, which in most situations is wrong.

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PubMed2004

Phase modulation by polarization recording in bacteriorhodopsin: application to phase-shifting interferometry.

A novel phase-control method with application to phase-shifting interferometry is presented. The linear polarization state of an external (green) light beam is recorded on a bacteriorhodopsin film, and this polarization state is read by a circular polarized (red) laser beam. By reading the bacteriorhodopsin film, the original (red) wave reverses its circularity and becomes phase shifted by an amount that is dependent on the polarization of the external (green) beam. This method of phase control can be applied in a two-beam interferometer in which the test and reference waves are orthogonally polarized, which allows one to obtain phase modulation without moving parts inside the interferometer.

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PubMed2003

Enhancing the phase profile and contrast of an interferogram by polarization recording in bacteriorhodopsin.

Interferometry is a technique for reconstructing the profiles of phase objects. We present a novel interferometric setup for generating interferograms with doubled phase profile and enhanced contrast compared with the standard interferogram. The proposed system consists of a two-beam interferometer in which the reference and test waves are circularly polarized orthogonally to each other. They are superposed upon a bacteriorhodopsin film, creating a polarization grating that is distorted by the phase of the test object. This polarization pattern is read by a polarized He-Ne beam. We show analytically and experimentally that, when the zero diffraction order is removed, an interferogram with doubled phase profile and enhanced contrast is obtained.

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PubMed2003

Harmonic-based gain compensation method in optic sensors with separate light paths.

We describe a method for the compensation of gain unbalance in optical sensors with separate light path that involve two separate detection and conditioning electronic devices. The method is based on the digital measurement of harmonics of the output intensities from each path by means of the fast Fourier transform algorithm. The quotient of the amplitude of harmonics allows us to calculate the unbalance between paths and to compensate for it. In particular, this method can be applied electric power and current sensors that use Faraday and Pockels cells to measure current and voltage, respectively.

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PubMed2003

Generation of nondiffracting beams by spiral fields.

In this paper we demonstrate that spiral fields generate nondiffracting dark beams. A collimated laser beam incident on a compact disc, i.e., a commercial CD, was used as mask for the generation of spiral fields. We study theoretically and experimentally the intensity distribution near the axis of the optical system.

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