Optical Measurement Techniques

Sirohi, R. S.

doi:10.1007/3-540-29303-5_1

Cited by 2 publications

(1 citation statement)

References 39 publications

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“…The displacement of the target can easily be determined by counting the number of fringes and multiplying this value to the light source wavelength. In order to find out the direction of the target displacement as well as the target displacement, the interferometer should provide quadrature signals which can be produced by using two slits with two detectors on the fringe patterns or by separating horizontal and vertical components using the polarization technique [4]. The operation of a phase-shifted quadrature using the Fabry-Perot fiber-optic sensor is demonstrated for detecting the amplitude and the relative polarity of the dynamically varying system [5].…”

Section: Introductionmentioning

confidence: 99%

A laser interferometer encoder with two micromachined gratings generating phase-shifted quadrature

Shin¹,

Kim²

2011

J. Micromech. Microeng.

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This paper presents a laser interferometer encoder which generates a quadrature signal by using two gratings with a phase difference. The phase difference comes from an 86 nm step difference between the gratings. The step is about 1/8 of the wavelength of the laser. Thus, two diffracted optical signals generated from the two gratings have about 90° phase difference from each other. The two gratings are fabricated on a quartz wafer with two different periods, 4 and 6 µm, to avoid the overlapping of the two diffraction signals in detection. Simulation results using propagation of an angular spectrum of the laser source through the gratings are compared with experiment results for displacement measurement. The comparison of both results shows very close correlation. It also confirms that the resolution of the developed sensor is 1/8 of the wavelength of the HeNe laser by using the quadrature signals.

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Section: Introductionmentioning

confidence: 99%

A laser interferometer encoder with two micromachined gratings generating phase-shifted quadrature

Shin¹,

Kim²

2011

J. Micromech. Microeng.

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Specific features for the analysis of fringe images

et al. 2008

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In optical nondestructive testing, a novel solution is presented for fault detection based on the interpretation of fringe images. These images can be acquired using different optical methods, such as structured lighting or interferometry. We propose a set of eight special features adapted to the problem of surface inspection using structured illumination. These characteristics are combined with six further features specially developed for the classification of faults using interferometric images. We apply two kinds of decision rules: the Bayesian and the nearest neighbor classifiers. The proposed features are evaluated using a noisy and a noise-free image data set. All patterns were obtained by means of structured lighting. Concerning the noisy data set, we obtain better classification rates when all the 14 features are used in combination with a one-nearest-neighbor classifier. In case of a noise-free data set, we show that similar classification rates are obtained when the 14 features or only the 8 specific features are involved. The methods described are designed to address a broad range of optical nondestructive applications involving the interpretation and classification of fringe patterns

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Optical Measurement Techniques

Cited by 2 publications

References 39 publications

A laser interferometer encoder with two micromachined gratings generating phase-shifted quadrature

A laser interferometer encoder with two micromachined gratings generating phase-shifted quadrature

Specific features for the analysis of fringe images

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