Effect of beam quality on tilt measurement using cyclic interferometer
28 Aug 2016-Proceedings of SPIE (International Society for Optics and Photonics)-Vol. 9960, pp 153-159
TL;DR: In this paper, the effect of aberration of the input beam on the accuracy of tilt measurement was investigated using multiple reflections in a cyclic interferometer, and the results on this study are presented in this paper.
Abstract: Accurate measurement of angles is extremely important in various metrological applications. Interferometry has always
been an excellent technique for accurate measurements. Several methods have been proposed for accurate tilt measurement
using interferometric techniques. Almost all of them use the Michelson configuration which is extremely sensitive to
environmental vibrations and turbulences. We know that a cyclic interferometer is extremely stable. Even though it is not
sensitive to displacement changes, it is twice sensitive to tilt compared to that of a Michelson interferometer. We have
enhanced the sensitivity to measure tilt using multiple reflections in a cyclic interferometer. Since the input beam is
collimated, we have studied the effect of aberration of the input beam on the accuracy of tilt measurement. Experimental
results on this study are presented in this paper.
Citations
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15 Jun 2018
TL;DR: In this article, the effect of the misalignment of the quarter wave plate on the visibility of the fringes and consequently on the accurcy of the measurement was numerically investigated and a new scheme of polarizing phase shifting techique was developed which is rather simpler compared to those reported in the literature.
Abstract: Precise measurement of extremely small tilt angles is of immense importance in various scientific and technological applications. Interferometry has always been a tool of great importance in such applications. Most of the conventional interferometric techniques use a Michelson configuration and the problem with this interferometer is that it is extremely sensitive to environmental turbulances and vibrations. In our privious works, we had introduced a cyclic interferometer for the measurement of tilt angles which showed excellent stability against environmental turbulances and vibrations as well as twice the sensitivity. Also, with the introduction of multiple reflections, sensitivity as low as 5 micro radian had been achieved by us. To improve the sensitivity further, we had employed phase shifting techniques. The cyclic configuration being a same path interferometer, we used a polarizing phase shifting technique. For acieving this, we developed a new scheme of polarizing phase shifting techique which is rather simpler compared to those reported in the literature. With this we could precisely measure angles as low as 2 nano radians. However, in these measurements we found that the precise alignment of the quarter wave plate plays an important role in the visibility of the fringes which affects the accuracy of measurement. In this work, we numerically investigate the effect of the misalignment of the quarter wave plate on the visibility of the fringes and consequently on the accurcy of the measurement.
2 citations
DOI•
09 Mar 2022
TL;DR: In this paper , the thickness of the material and fringes pattern are fundamental parameters in such measurement, and the phase shift and reflected angles can be found and employed for refractive index determination using multiple light reflections with modified Sagnac interferometer.
Abstract: Refractive index finding using multiple light reflections with modified Sagnac interferometer is proposed here. The thickness of the material and fringes pattern are fundamental parameters in such measurement. In this proposed technique, multiple light reflections, by the two parallel mirrors attached to a piezo-electric transducer (PZT) vibrating at a frequency of 420Hz, introduced the phase retardation. The phase retardation and reflected angles could be found and employed for refractive index determination. Four identical interferograms were obtained by a half-wave plate (HWP) oriented at 0, π/2, π and 3π/2 rad with respect to the incident plane. The intensities at their respective patterns were evaluated and the phase shift could be computed. Using numerous reflections with a Sagnac interferometer, this technique is presented to obtain multiple fringes with a sample fixed in position at certain carrier frequencies.
TL;DR: In this paper , the Sagnac interferometer was modified with phase shifting approach for the determination of thin-film thickness, and the results showed that the phase-shifting technique using three-polarization settings is more suitable for the thickness measurement of the transparent thin film.
Abstract: This paper presents the comparison of three-, four- and five-step techniques for measuring transparent thin-film thickness of Ta2O5 and WO3 deposited on BK-7 substrates. The Sagnac interferometer was modified with phase shifting approach for the determination of thin-film thickness. The input light beam was split into reference and testing beams. Before the output light reaching the balanced photodetectors, the real-time signal detection was performed to obtain the output intensities of both beams using three-, four-, and five-polarization settings of an analyzer. The thicknesses could then be efficiently translated from the measured intensities. Thicknesses from three-, four- and five-stepping algorithms were compared with ones from the conventional FE-SEM measurement, and it was discovered that the former performed better with less errors. The findings show that the phase-shifting technique using three-polarization settings is more suitable for the thickness measurement of the transparent thin film.
Journal Article•
TL;DR: Naderishahab et al. as mentioned in this paper used a cyclic interferometer with four mirrors to measure tilt angles as small as a few nanoradians, and a simple method of phase shift by polarization was developed to enhance measurement sensitivity and accuracy.
Abstract: Naderishahab, Tahereh M.S.O.E July 2017 High accuracy tilt or roll angle measurement is required for a variety of engineering and scientific applications. Optical interferometry is normally used because it is non-contact and can measure tilt with a very high degree of accuracy. In this thesis, a cyclic interferometer has been developed with four mirrors to measure tilt angles as small as a few nanoradians. To measure the phase, a novel and simple method of phase shift by polarization was developed to enhance measurement sensitivity and accuracy. Since the cyclic interferometer is insensitive to external vibrations and turbulences, polarization phase step was accomplished with relative ease. To introduce the phase shift, a quarter wave plate and a half wave plate were used with a polarized laser beam. Multiple reflections were also introduced in the cyclic interferometer to enhance tilt measurement capability. A new method was developed to evaluate phase and eventually measure the tilt even in the case of changing fringe visibility. The results of these studies show that the multiple reflection cyclic interferometer can be used to measure object tilts in the order of 0.2 nanoradians or 10 arc second.
Cites background from "Effect of beam quality on tilt meas..."
...Further studies of the influence of aberrations on the tilt measurement were carried out and shown that spherical aberration will introduce large errors in the measurement of tilt [23]....
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References
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TL;DR: The earliest prediction of the Sagnac effect, and of the possibility of detecting the Earth's rotation with an interferometer of square kilometer area, is by Lodge (1893, 1897) as mentioned in this paper.
Abstract: The earliest prediction of the Sagnac effect, and of the possibility of detecting the Earth’s rotation with an interferometer of square kilometer area, is by Lodge (1893, 1897). We illustrate the extraordinary range of theoretical motivations for the experimental study of the Sagnac effect, starting with previously unpublished correspondence between Lodge and Larmor, and ending with present (and planned) ring interferometer experiments whose sensitivity to the Earth’s rotation is of the order of parts per million (billion, respectively).
144 citations
TL;DR: A new interferometric device for measuring small angles or rotations with high accuracy is described, which works by counting fringes formed by the rotation of a flat-parallel plate of glass illuminated with a collimated beam from a gas laser.
Abstract: A new interferometric device for measuring small angles or rotations with high accuracy is described. This instrument works by counting fringes formed by the rotation of a flat-parallel plate of glass illuminated with a collimated beam from a gas laser. Some possible applications are given.
83 citations
TL;DR: To measure small-angle rotations, the two mirrors of a Michelson interferometer are replaced by right-angle prisms and rotation of the latter shifts the interference pattern.
Abstract: To measure small-angle rotations, the two mirrors of a Michelson interferometer are replaced by right-angle prisms. Rotation of the latter shifts the interference pattern. Measurement of that shift gives, after calibration, the rotation. The experimental setup is insensitive to vibrations, provides good linearity between +5 degrees and -5 degrees , and has a resolution of 10(-4) deg.
79 citations
TL;DR: In this article, an angle measuring interferometer of the Michelson type, constructed for use primarily with a gamma diffraction spectrometer, is described, which has a sensitivity of 0.1 sec of arc on a measuring range of 30 deg, is designed with plane mirrors as end reflectors and a cube corner prism as the movable unit.
Abstract: S>An angle measuring interferometer of the Michelson type, constructed for use primarily with a gamma diffraction spectrometer, is described. The interferometer, which has a sensitivity of 0.1 sec of arc on a measuring range of 30 deg , is designed with plane mirrors as end reflectors and a cube corner prism as the movable unit. The interferometer operates with a continuously varying glass compensation. Several geometrically different arrangements of the components are possible. (C.E.S.)
62 citations
TL;DR: An interferometers designed to measure and/or generate angles with high precision and accuracy is described and the experimental performance of a prototype interferometer is discussed.
Abstract: An interferometer designed to measure and/or generate angles with high precision and accuracy is described. Design criteria and equations are developed and the experimental performance of a prototype interferometer is discussed.
62 citations