Calibration of rotary tables can be performed using autocollimators or laser interferometer systems. In this investigation a comparison between these two methods of calibration as applied on an optical rotary table has been carried out. The calibrated table is a Carl Zeiss optical rotary table of resolution 30 arcsecond. An Elcomat® 3000 autocollimator system and an Agilent® 5529A laser interferometer system have been used in this calibration. A precise indexing table of 360 serrations with accuracy of ± 0.5 arcsecond manufactured by Davis® and a glass polygon of 12 faces with accuracy of ±...
The work introduces a high-resolution displacement measurement method in a nanometer scale using passive Fabry-Perot cavity. The optical frequency of selected resonant mode of the cavity is monitored during changes of the cavity length. It uses an optical mixing the frequency of a tunable laser with frequency teethes of a femtosecond optical synthesizer (optical frequency comb). The tunable laser diode is locked to a selected mode of the optical resonator to monitor the exact mirror distance of Fabry-Perot cavity. Then a laser diode optical frequency is mixed with the beam from the...
In this contribution we present an approach toincremental interferometric measurements of displacements over a limited range where the atmospheric wavelength of the coherent laser source is either directly stabilized to a mechanical reference or is corrected to fit to the reference. The idea comes from the possibility to use a highly stable material for a reference frame, material which can perform thermal expansion coefficients on the level 10 -8 /K within a large temperature range up to 50K. Over a range of several K which may be the practical range for displacement measurements the...
Within the EURAMET joint research project "Absolute Long-distance Measurement in Air" an absolute measuring heterodyne interferometer was developed for a measuring range of 1 km with a targeted accuracy of 0.1 mm. Since one dominating uncertainty source for interferometric length measurement is the refractiveindex of air, especially under outdoor conditions, a two wavelength compensation method is integrated in the set-up. Measurements were performed on a 50 m comparator equipped with a HeNe laser interferometer.
We present the results of far-field nanoscopic investigation on the sub-micrometer localization and characterization of defects in optoelectronic devices (e.g. monocrystalline silicon solar cell structure) due to the material processing. Solar cells are generally prepared from Si-ingots sawed into thin round wafers by metallic wire. Hence, first defects appear on the sites of metallic precipitates, which reduce quantum efficiency of cells. Second type of defects then originates from further fitting of the round wafer into square cells. The latter can be dimensioning by mechanical sawing or...
Phase and group velocities of wave are most frequently used in the research of physical processes and phenomena in dispersion media. The difference existing between phase velocities of ideal harmonic waves and real non-monochromatic waves comes into conflict with their physical interpretation, that sometimes brings some additional errors both in theoretical investigations and the results of physical measurements. The concepts developed at the beginning of the 20th century have not been properly estimated and now they need to be specified and revised.
Surveying instruments have to meet certain specifications in order to provide the necessary accuracy standards for a certain application. The main purpose of testing a used terrestrial laser scanner (TLS) is does an instrument still meets factory accuracy standards or not. This paper outlines the procedures for the investigation of the TLS accuracy in laboratory conditions without high expensive equipment e.g. a calibration track line and a laser interferometer. The test field contains control targets and observation pillars. 3D position of the pillars and the targets are derived from an...
We consider measuring machines (MMs), which use one ore more 2-D laser sensors (2-DLSs) for automated dimensional inspection. In order to transform several measurements from their sensor coordinate frame (CF) into a world or object CF, we need a parameterized model of these transformations. We present a method, which allows for very different MMs to set up a model, to construct a calibration object and to estimate the model parameter from measurements on the calibration object.
Combining contact and non-contact CMM probes provides a promising solution to meet the increasing requirements on complexity and accuracy of dimensional metrology, and benefit inspection performance. However, the automated planning of measurement strategies for such hybrid CMM systems hasn’t been well addressed yet. This paper proposes an automated inspection planning approach for CMM inspection combining tactile probing and laser scanning. The right sensor is first selected for each feature being inspected. According to the selected sensor, the suitable procedures are performed to create...
The lock-in principle is a preferred method to determine the phase difference between elec trical signals of heterodyne interferometer. A phase meter based on this method was devel oped at PTB allowing to detect fractions of an optical fringe in the range of a few picometers, which is verified by experimental results.