Simple phase shifting by polarizer rotations in a cube beam-splitter interferometer.

A simple and low-cost method for phase-shifting interferometry by the rotation of a polarizer is presented. This proposal takes advantage of the polarization aberration in a cube beam splitter due to its geometry, to the angular dependence with the coating, and to the polarization angle of the input beam. The interferometric setup performs as a two-window common-path interferometer in which the added phase shifting is achieved by simply rotating a polarizer at the interferometer output. The viability of the proposal is sustained with experimental results in which the phase-shift value and the resulting wavefront are calculated with Farrel's technique and the three-step PSI algorithm, respectively.

Phase shifting by wavelength modulation in a cube beam splitter interferometer.

A low-cost and fully automated process for phase-shifting interferometry by continuously changing the input voltage of a laser diode under the scheme of a cube beam splitter interferometer, performing as a two-window common-path interferometric setup, is presented. The input signal of a laser diode is controlled by a data acquisition device which permits a change in its wavelength according to its tunability features. The automation and data analysis is done using LabVIEW in combination with MATLAB. By using the Carré algorithm, the phase map is obtained. Measurements of visibility and phase shift to verify the phase-shifting interferometry requirements are also shown.

Fully automated low-cost setup for fringe projection profilometry.

In this paper an alternative low-cost, easy-to-use, and fully automated profilometry setup is proposed. The setup is based on a phase-shifting fringe projection technique with four projected fringe parameters. It uses the well-known triangulation arrangement and low-cost electronic and image acquisition components such as a data acquisition board, a motor controller board, a printer rail, a CMOS webcam, and an LCD projector. The position of the camera, the generation of the fringe pattern, the acquisition of the images, and the calculation of the wrapped and unwrapped phase are all performed in LabVIEW. The setup is portable and can be perfectly adapted to be used in other profilometry techniques such as electronic speckle pattern interferometry and laser scanning profilometry.

Phase shifting and phase retrieval with a fully automated laser diode system.

A low-cost and fully automated process for phase-shifting interferometry (PSI) by continuously changing the input voltage of a laser diode (LD) under the scheme of an unbalanced Twyman-Green interferometer (TGI) setup is presented. The input signal of a LD is controlled by a data acquisition (NI-DAQ) device that allows it to change its wavelength according to its tunability features. The automation and data analysis will be done using LabVIEW in combination with MATLAB. The phase map is obtained using the Carré algorithm. Measurements of visibility and phase shift to verify the PSI requirements are shown. It is demonstrated with experimental results and statistical analysis that the phase retrieval can be successfully achieved without calibration and using minimal optical devices.

Inhomogeneous phase-visibility modulating interferometry by space on-off non-quadrature amplitude modulation.

A new method in interferometry based on on-off non-quadrature amplitude modulation for object phase retrieval is presented. Although the technique introduces inhomogeneous visibility and phase variations in the interferogram, it is shown that the phase retrieval of a given object is still possible. This method is implemented by using three beams and two Mach-Zehnder interferometers in series. One of the arms of the system is used as a probe beam and the other two are used as reference beams, yielding from their sum the conventional reference beam of a two-beam interferometer. We demonstrate that, if there is a phase difference within the range of (0,π) between these two beams, the effect of modulation in both amplitude and phase is generated for the case of on-off non-quadrature amplitude modulation. An analytical discussion is provided to sustain this method. Numerical and experimental results are also shown.

Double aperture common-path phase-shifting interferometry by translating a ruling at the input plane.

A method for introducing phase steps in an interferogram based on translating a ruling at the input plane of a double aperture common-path interferometer is presented. The setup is built on a 4f optical system consisting of two apertures at the input plane and a Ronchi ruling in the Fourier plane, where at each aperture a Ronchi ruling is also placed. By filtering at the Fourier plane a single diffraction order of the spectrum from the rulings in the object plane, we demonstrate that a phase step is generated when one of the rulings in the input plane is translated. The principal advantage of this proposal lies in improving the resolution in the phase step. We develop a theoretical model and show experimental results.

Phase-shifting interferometry by wave amplitude modulation.

A new method for phase-shifting interferometry based on wave amplitude modulation is proposed and discussed. This proposal is based on the interference of three waves, where two waves attend as two reference waves and the other wave attends as a probe wave. Thereby, three interference terms are obtained, but because a phase difference of π/2 between the two references is kept constant, one of the three terms will be dropped, while the two remaining will be put in quadrature. Under these conditions, the resulting pattern is mathematically modeled by an interferogram of two waves, where an additional phase is given by the amplitude variations of the reference waves. In this Letter, both a theoretical model and some numerical simulations are presented.