We newly propose the optical micro-coordinate measurement technique based on the fluorescent signal. Surface position is detected based on fluorescent signal emitted from surface of structures by means of the confocal optical detection. Stimulated fluorophore emits fluorescence over wide angular ranges, allowing the confocal microscope to gather the fluorescent signal from steep surface (even from vertical sidewall). Thus this optical method is expected to measure three-dimensional shapes of smaller structures than 100 µm. Previously we reported the detection capability of a vertical surface based on the fluorescent signal with the confocal optical system. This paper deals with feasibility of three-dimensional measurement of micro-structures. Firstly, characteristic of detecting surface with various tilted angles were measured. As a substrate, the flat silicon wafer coated with the fluorescent dye thin film with a thickness of a few micrometers was used. Experimental result shows that the horizontal (0 deg.), vertical (90 deg.) and also undercut surface (120 deg.) could be successfully detected. At next, a cross-sectional shape of a metal wire was measured. A diameter of the wire was about 1 mm. The wire was also coated with fluorescent dye thin film. The result showed that the cross-sectional profile of the wire could be measured although the accuracy could not be ensured yet. We concluded that the proposed method manage to measure three-dimensional shapes of micro-structures.

This paper proposes non-contact pulse interferometer for dimensional metrology using the repetition frequency of the optical frequency comb. The repetition frequency of 100 MHz of a general optical frequency comb is transferred to that of 1 GHz by using a Fabry-Pérot Etalon, which is firstly developed by single mode optical fiber. Therefore, temporal-coherence interference fringes are generated at each several cm and then compact absolute position- measuring system is realized for practical non-contact use with a high accuracy measurement. The stability and accuracy of measurements are compared with commercial incremental laser interferometer. The drifts of both systems are the same tendency. The maximum drift difference between two interferometer systems is about 0.1 µm. And the maximum difference of length measurement of both systems is about 0.18 µm at the length of 150 mm while the maximum standard deviation of pulse interferometer is better than incremental interferometer about 10 times. Then, the pulse interferometer is constructed and a metal sphere ball is used as a target of interferometer. The average standard deviation of distance/length measurement is about 0.6 µm for the measuring length up to 1.5 m. This new technique can provide a high accuracy for non-contact measurement system such as a simple pulse tracking system.

At INRIM a novel absolute long distance interferometer has been developed for application in space missions. The interferometer has been successfully tested for long distance measurements in air. Main limitation of such measurements is the knowledge of refractive index of air which in turn is mainly affected by air temperature. A method to measure average air temperature based on the measure of the speed of sound has been developed and combined with the absolute interferometer achieving measurement uncertainties less than 1 ppm in open air up to a 78 m distances.

Optical frequency comb has various characteristics such as short pulse, broad spectra, many spectral lines, and high temporal coherency. In this present, new absolute length-measuring technique with a high resolution of 0.1 µm is developed by using temporal-coherence interferometry of optical comb and a short translation stage for various length ranges. A new fiber Fabry-Perot etalon of a free spectral range of a frequency of 15 GHz is developed for improving the fine positioning in space. Moreover, interference-fringe-peak is automatically achieved by developing a new analog electric circuit. One position is measured round several milliseconds depending to the SN ratio of the signal detected for various ranges of the lengths measured.

Surface plate characteristics influence the calibration of artifacts, instruments, working gauges and, by extension, the quality of manufactured parts. Industrial surface plates are calibrated periodically. Moody or Union Jack Method is applied to calibrate the surface plate alongside the application of latest laser equipment. This procedure necessitates sophisticated tooling and the pertinent calibration sequence to obtain the reliable results. In this method, the residual height at each position on the surface is expressed in terms of measurement parameters. A statement of uncertainty for the surface plate calibration is needed for conformance testing and for estimating uncertainty in calibrations that rely on the surface plate. The maximum uncertainty is at the center of the surface as per the Moody Method and the calculated bounds compare well with values of closure from actual measurements. The uncertainty of height values is proportional to the measurement positions. Measurement Standards Laboratory (MSL) operates under the Total Quality Management Scheme and in conformity with ISO/IEC-17025: General requirements for the competence of testing and calibration laboratories guidelines. The paper discusses the novel approach towards determining the flatness characteristics of the surface plate measurement uncertainty of flatness measurement applying the universally most reliable Moody Method. Furthermore, the impact of grid parameters such as alignment side, measurement sequence and number of measurement steps on measurement results is evaluated. The reproducibility of the obtained results is ascertained using the laser optics. Subsequently, the measured data points are fed into a stand-alone computer program which displays numeric as well as isometric data plots for the surface plate in measurement.