The Comparison of Environmental Effects on Michelson and Fabry-Perot Interferometers Utilized for the Displacement Measurement

The optical structure of general commercial interferometers, e.g., the Michelson interferometers, is based on a non-common optical path. Such interferometers suffer from environmental effects because of the different phase changes induced in different optical paths and consequently the measurement precision will be significantly influenced by tiny variations of the environmental conditions. Fabry-Perot interferometers, which feature common optical paths, are insensitive to environmental disturbances. That would be advantageous for precision displacement measurements under ordinary environmental conditions. To verify and analyze this influence, displacement measurements with the two types of interferometers, i.e., a self-fabricated Fabry-Perot interferometer and a commercial Michelson interferometer, have been performed and compared under various environmental disturbance scenarios. Under several test conditions, the self-fabricated Fabry-Perot interferometer was obviously less sensitive to environmental disturbances than a commercial Michelson interferometer. Experimental results have shown that induced errors from environmental disturbances in a Fabry-Perot interferometer are one fifth of those in a Michelson interferometer. This has proved that an interferometer with the common optical path structure will be much more independent of environmental disturbances than those with a non-common optical path structure. It would be beneficial for the solution of interferometers utilized for precision displacement measurements in ordinary measurement environments

Automatic Calibration System for Precision Angle Measurement Devices

A proposed optomechatronic module is intended for the automatic and efficient calibration procedure of compact autocollimators utilized for high precision angle measurement. Conventional autocollimators have the disadvantages, e.g. the large volume and high cost, hence novel compact autocollimators have been developed in the past decade. To satisfy the practical applications, the measuring performance of a compact autocollimator must be determined and it has become important to offer a proper and efficient calibration module for the compact autocollimator. </p

A novel algorithm for the signal interpolation of the displacement measurement based on a Fabry-Perot interferometer

Current commercial interferometers reveal excellent measurement performances, because of its major advantage which enables the displacement measurement with the characterization of the high resolution under the large measuring range. Fabry-Perot interferometer is a compact interferometer with the structure of common optical path. In comparison with the ordinary commercial laser interferometers having non-common optical path, Fabry-Perot interferometer is more insensitive to environmental disturbances. But the disadvantages of Fabry-Perot interferometer are the limited measuring range and the considerable visibility decadence of the interference pattern. To enlarge the measuring range, the folded Fabry-Perot interferometer in which a corner cube reflector severs as the measurement mirror has been proposed in the previous research. However, either the conventional Fabry-Perot interferometer or the folded Fabry-Perot interferometer still have the problem of the considerable visibility decadence of the interference pattern. When the length of optical cavity is changed, the overlapped state of the laser beams will be varied strongly. Hence, it is indispensible to offer a proper signal interpolation algorithm for various signal distributions during the displacement measurement in the whole measuring range. An advanced signal interpolation algorithm for the above-mentioned Fabry-Perot interferometer has been proposed in this investigation. The novel algorithm is able to solve the problem of the displacement measurement due to the considerable visibility decadence of the interference pattern. With this algorithm, a high precision displacement measurement in the large measuring range can be realized by the folded Fabry-Perot interferomete

Automatic calibration system for micro-displacement devices

With the industrial development and the advances in micro - displacement technology, the demands on piezo transducers are increasing. For piezo transducers, the error inspections of the non-linearity and the hysteresis are necessary procedure before piezo transducers utilized. Due to the possible decline or damage during the employment of the transducers, it is important to provide the automatic calibration system. In this investigation, a self-developed automatic calibration system for micro-displacement devices is proposed. The automatic system according to the international specification of ASTM-E2309 has been developed. This system designed for the calibration of piezo transducers is based on the interferometric structure of the common optical path and possesses the resolution of the nanometer order. The experimental verifications demonstrate that the repeatability of the Fabry-Perot interferometer is less than 11 nm. Experimental results of the synchronic measurement with the self-developed interferometer and a commercial interferometer reveal that the differences of the maximum nonlinearity error and maximum hysteresis error are less than 1%. With the proposed correct equations, the maximum non-linearity error can be minimized to 1% and the maximum hysteresis error will be less than 5.2%

Optimization of the optical parameters in Fabry-Perot interferometer

Due to insensitivity to the environmental disturbances, Fabry-Perot interferometers are suitable for displacement measurements under ordinary conditions. In the structure of folded Fabry-Perot interferometer, the results of the signal subdivision are affected by the optical parameters in the resonant cavity. In this paper, the analysis of the Fabry-Perot interferometer for the measurement of the micro-displacement and the long-distance are investigated. By considering the reflectance of the planar mirror and the intensity loss in the resonant cavity, the parameters of systematic optimization which are suitable for the measurement of the micro-displacement and the long-distance are proposed. The experimental and simulated results reveal that the intensity loss in the resonant cavity is 86% and the optimized reflectance of the planar mirror is 12%

Preparation, characterization and crystal structure of [Ni(bpy)3][Fe(CN)5(NO)]3H2O and one-dimensional cyano-bridged [Ni(en)2Fe(CN)5(NO)]H2O

[[abstract]]Two new double complexes [Ni(bpy)3][Fe(CN)5(NO)]3H2O (1) and [Ni(en)2Fe(CN)5(NO)]H2O (2) have been isolated from the reactions of the mixture of NiCl2·6H2O and Na2[Fe(CN)5(NO)] in water, with bipyridine (bpy) and ethylenediammine (en) in ethanol, respectively, and have been characterized by X-ray analysis, IR, EPR, Mössbauer spectroscopy and magnetic measurements. Crystallographic data for 1 and 2 areas follows: triclinic, Full-size image (<1 K); 2: triclinic, Full-size image (<1 K). The bond angles of FeNO are nearly linear for 1 (178.3(4)°) and 2 (1i79.4(3)°). The structure of 1 consists of a double complex of a cation [Ni(bpy)3]2+ and an anion [Fe(CN)5(NO)]2−. The structure of 2 consists of a one-dimensional polymeric chain Ni(en)2NCFe(CN)3(NO)CNNi(en)2 in which the Ni(II) and Fe(II) centers are linked by two CN groups. Crymagnetic investigations (4–900 K) reveal a paramagnetic behavior for 1 and the presence of a one-dimensional Heisenberg weak antiferromagnetic chain with J=−0.47 cm−1 for 2. EPR spectra observed at ambient temperature for the Ni(II) ions in both complexes are also reported.[[notice]]補正完畢[[incitationindex]]SC

Small-angle Sensor Based on the SPR Technology and Heterodyne Interferomery

A small-angle sensor based on the surface plasmon resonance (SPR) technology and heterodyne interferometry is proposed. In the paper, we try to measure the phase difference variation between s and p polarizations due to attenuated total reflection (ATR). The phase difference variation depends on the incident angle. Therefore, only evaluating the phase difference variation can perform small-angle measurement. The resolution of the method can reach 2.4 x 10-7 radian. The method has some merits, e.g., a simple optical setup, easy operation, high measurement accuracy, high resolution, rapid measurement, and high stability etc. And its feasibility is demonstrated

Investigation on the Differential Quadrature Fabry–Pérot Interferometer with Variable Measurement Mirrors

Due to the common path structure being insensitive to the environmental disturbances, relevant Fabry&ndash;P&eacute;rot interferometers have been presented for displacement measurement. However, the discontinuous signal distribution exists in the conventional Fabry&ndash;P&eacute;rot interferometer. Although a polarized Fabry&ndash;P&eacute;rot interferometer with low finesse was subsequently proposed, the signal processing is complicated, and the nonlinearity error of sub-micrometer order occurs in this signal. Therefore, a differential quadrature Fabry&ndash;P&eacute;rot interferometer has been proposed for the first time. In this measurement system, the nonlinearity error can be improved effectively, and the DC offset during the measurement procedure can be eliminated. Furthermore, the proposed system also features rapid and convenient replacing the measurement mirrors to meet the inspection requirement in various measuring ranges. In the comparison result between the commercial and self-developed Fabry&ndash;P&eacute;rot interferometer, it reveals that the maximum standard deviation is less than 0.120 &mu;m in the whole measuring range of 600 mm. According to these results, the developed differential Fabry&ndash;P&eacute;rot interferometer is feasible for precise displacement measurement