Robust one-beam interferometer with phase-delay control.
TL;DR: In this paper, a robust one-beam interferometer with external phase-delay control is described, where the two arms are together in one collimated beam, and an additional phase delay is introduced by application of an electrical current to the Faraday rotator or by rotation of the polarizer (the latter being of topological origin).
Abstract: A robust one-beam interferometer with external phase-delay control is described. The device resembles a Mach-Zehnder interferometer in which the two arms are together in one collimated beam. However, the proposed device is not an amplitude-division interferometer but a wave-front division one. The phase-delay control occurs at the interferometer output with the help of two polarizing beam splitters, a quarter-wave plate, a Faraday rotator, and a polarizer. An additional phase delay is introduced by application of an electrical current to the Faraday rotator or by rotation of the polarizer (the latter is of topological origin), which permits the use of techniques of phase-stepping interferometry.
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TL;DR: In this paper, a phase difference between orthogonal polarizations is used to record two phase-shifted holograms simultaneously, by combining the holograms with the distributions of a reference wave and an object wave, the complex field of the object's wavefront can be obtained.
Abstract: Phase-shifting digital holography with a phase difference between orthogonal polarizations is proposed. The use of orthogonal polarizations can make it possible to record two phase-shifted holograms simultaneously. By combining the holograms with the distributions of a reference wave and an object wave, the complex field of the object's wavefront can be obtained. Preliminary experimental results are shown to confirm the proposed method.
122 citations
TL;DR: In this article, a beam-splitter cube is used to produce two interferograms with a relative phase shift of π (rad) for spatial-carrier interferometry and flexible writing of fiber Bragg gratings.
43 citations
TL;DR: An off-axis, wide-field, low-coherence and dual-channel interferometric imaging system, which is based on a simple-to-align, common-path interferometer, is introduced and high quality depth profiles of fingerprint templates are produced.
Abstract: We introduce an off-axis, wide-field, low-coherence and dual-channel interferometric imaging system, which is based on a simple-to-align, common-path interferometer. The system requires no optical-path-difference matching between the interferometric arms in order to obtain interference with low-coherence light source, and is capable of achieving two channels of off-axis interference with high spatial frequency. The two 180°-phase-shifted interferograms are acquired simultaneously using a single digital camera, and processed into a single, noise-reduced and DC-suppressed interferogram. We demonstrate using the proposed system for phase imaging of fingerprint templates. Due to the fact that conventional phase unwrapping algorithms cannot handle the complex and deep surface topography imposed by fingerprint templates, we experimentally implemented two-wavelength phase unwrapping using a supercontinuum laser coupled to acousto-optical tunable filter, together functioning as a low-coherence tunable light source. From the unwrapped phase map, we produced high quality depth profiles of fingerprint templates.
39 citations
TL;DR: A simple method for visualization of phase objects placed between a printed two-dimensional periodic pattern and a CCD camera that has potential application for detection of gas leaks in industrial environments.
Abstract: We describe a simple method for visualization of phase objects The phase object is placed between a printed two-dimensional periodic pattern and a CCD camera The ray deflection that is due to the phase object distorts the image of the pattern This image is subtracted from a reference image and then, by squaring and low-pass filtering, a measurement of the two-dimensional refractive-index changes is obtained Because the optical system does not require special alignment or illumination, the method presented has potential application for detection of gas leaks in industrial environments
35 citations
TL;DR: In this paper, a new approach for deriving the analytic phase-to-height model is presented, which is not restricted to the system's geometry nor to the type of structured light projection employed.
Abstract: Non-contact shape measurement using structured light optical techniques has found many applications in health care and industry. The process of shape measurement consists of various stages, starting with the projection of structured light patterns and ending with the conversion of the measured phase of the captured intensity images to the required object height. Although various phase-to-height models exist in the literature, these models are usually restricted to a certain optical arrangement dedicated by the system components. Furthermore, the different approaches adopted in deriving these models employ numerous assumptions in order to simplify the analysis. This could make the derived models very sensitive to parameter variations of the model inputs. This paper presents a new approach for deriving the analytic phase-to-height model. This approach is not restricted to the system's geometry nor to the type of structured light projection employed. Therefore, it will allow us to better understand the various effects of system parameters on the measurement accuracy.
31 citations
References
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TL;DR: In this article, it was shown that the Aharonov-Bohm effect can be interpreted as a geometrical phase factor and a general formula for γ(C) was derived in terms of the spectrum and eigen states of the Hamiltonian over a surface spanning C.
Abstract: A quantal system in an eigenstate, slowly transported round a circuit C by varying parameters R in its Hamiltonian Ĥ(R), will acquire a geometrical phase factor exp{iγ(C)} in addition to the familiar dynamical phase factor. An explicit general formula for γ(C) is derived in terms of the spectrum and eigenstates of Ĥ(R) over a surface spanning C. If C lies near a degeneracy of Ĥ, γ(C) takes a simple form which includes as a special case the sign change of eigenfunctions of real symmetric matrices round a degeneracy. As an illustration γ(C) is calculated for spinning particles in slowly-changing magnetic fields; although the sign reversal of spinors on rotation is a special case, the effect is predicted to occur for bosons as well as fermions, and a method for observing it is proposed. It is shown that the Aharonov-Bohm effect can be interpreted as a geometrical phase factor.
7,425 citations
TL;DR: This work presents a remarkable optical ``nonlinearity'' of certain polarizing interferometers, which is discovered by using the concept of the topological phase on the Poincar\'e sphere and is demonstrated with a simple experiment.
Abstract: Since Berry introduced topological phases to describe the adiabatic transport of the spin of particles in parameter space, they have become a practical and descriptive concept for understanding interference phenomena in many quantum mechanical systems. For the photon two different applications of this concept were found in crystal optics: (1) the optical activity of helically wound optical fibers and (2) the development of the state of polarization on the Poincar\'e sphere. We present a remarkable optical ``nonlinearity'' of certain polarizing interferometers, which we discovered by using the concept of the topological phase on the Poincar\'e sphere and we demonstrate it with a simple experiment.
48 citations
TL;DR: In this paper, a phase-shifting apparatus based on polarization techniques is developed, which changes phase only by rotating a polarizer using a precise step motor and a specially designed decelerator.
Abstract: A new computer-controlled phase-shifting apparatus based on polarization techniques is developed. This apparatus changes phase only by rotating a polarizer using a precise step motor and a specially designed decelerator. The precision of this method can be higher than other methods because of the accurate control of the rotating angle. Four applications of this technique to optical interlerometry and 3-D shape measurements are presented.
23 citations
TL;DR: In this article, a phase step interferometry system using polarization shifting is described, which is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization travelling through the other arm.
Abstract: A phase step interferometry system using polarization shifting is described. The device is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization of light travelling through the other arm. At the interferometer output we place a quarter-wave plate with its fast axis at with respect to the polarization directions and a polarizer. By rotating the polarizer, the interfering waves acquire an extra phase (of topological origin) to that expected from the calculations of optical path lengths, and thus, arbitrary phase shifts can be induced. Then, from a set of interferograms recorded while the reference phase is changed, the `dynamical' phase difference (e.g. the phase profile of an object placed in one of the interferometer arms) can be reconstructed by using techniques of phase-shifting interferometry.
20 citations