We extrapolated the lucky imaging technique, mostly used in astronomy, to the field of interferometry for displacement measurement. From the batch of interferograms generated by a Twyman-Green-type interferometer and acquired by a CCD camera, those with high overall contrast were selected and fitted to a sinusoidal function. The high-contrast interferograms showed a significantly lower dispersion and, consequently, a lower uncertainty of the measured displacement.
Stationary Fizeau fringes, phase shift interferometric fringes, fringes obtained in Murty lateral shear interferometry, vibration interference pattern as seen by digital speckle pattern interferometer all are digitally captured in specific interferometer set- ups. IntelliWave software produced by Engineering Synthesis Design, Inc. (ESDI) is used to process the fringe patterns. For all these fringe patterns the physical principle and set up for obtaining them are described. This could be a resume for student and young researcher guiding in experimental interferometry.
Precise three-dimensional (3D) information is demanded by many new industries such as: semiconductor, photonics, MEMS, communications, microprocessing etc. [1, 2]. The problem is to select the proper measurement methods for material characteristics in the measurement field, from the point of view of the measurement accuracy and errors that can appear [1, 4, 3, 5]. There are several optical 3D measurements approaches, e.g.: triangulation, grating projection with phase shift, moiré with phase shift, confocal and (white light) interferometry (WLI) [2, 3]. They can measures: surface profile, roughness, step height, microstructure, and other surface parameters. The white light interferometers allows generally surface profiling with high accuracy with no phase ambiguity errors, making them more suitable for profiling stepped or discontinuous surfaces. WLI technique to determine the thickness of thin coating on reflective materials is very effective. One of the first techniques to utilize the short coherence of the white light source was the scanning interference microscope. There are on the market a variety of scanning white light interferometers. Measurement calibration is done using the short coherence feature of white light. Some of the presented applications in nanometrology are thin films thickness measurements of: carbons films on glass, metallic films on Silicon, ablated small holes diameter, and profiles of micro / nanostructure.
A laser strainmeter for in-situ monitoring of an important actively seismic area of Europe, namely Vrancea region in
Romania is proposed. Six groups from four different countries (Romania, Czech Republic, Italy and Greece) with
various areas of expertise (e.g. geophysics, lasers, optics, interferometry, and mechanics) are involved in order to sustain
the complexity of the project. This paper presents some preliminary laboratory experiments related to measuring relative
displacements with a stable interferometer. Displacements of the order of tens to hundreds of nanometers (80 to 285 nm)
were measured with uncertainty of ±1 nm. A computer algorithm was used to process the interferograms.