In this work, an optical method to characterize a turbulent liquid will be presented; it comes to measuring the content of a suspension in a liquid by laser scattering.
A laser beam transmitted through a transparent rectangular glass container including the emulsion of plaster is imaged using CCD camera, and the resulting image is processed to calculate the scattering intensity. Thus, a relationship between the concentration of the particles in the liquid and the full width at half maximum (FWHM) of the intensity profile of the scattered laser will be determined.
Furthermore, a measure of the contrast of an interference pattern obtained by Mach-Zehnder interferometer is achieved; the object beam passes through the glass container comprising the turbulent liquid. A correlation between the FWHM determined above and the contrast of the interference pattern as a function of the concentration of the emulsion will be deduced.
The present work aims to analyze and characterize the macro-geometrical defects of surfaces.
As a way of characterization an optical method is used, which is the projection of fringes that is a technique of non-destructive measurement.
The location, depth and size of surface defects can be determined automatically by projection of four figures of rectilinear fringes shifted in phase on the surface to be tested. An optical mounting of triangulation to project the fringes is then performed.
After projection, the projected gratings images are captured by a CCD camera, digitized and stored in computer memory. The application of phase shifting algorithm with four steps is achieved to determine the initial phase that contains the "measurand", which is the difference in shape. Pieces with different forms were tested.
Optical coherence tomography (OCT) is a powerful optical method, noninvasive and noncontact diagnostic method.
Although it is usually used for medical examinations, particularly in ocular exploration; it can also be used in optical
metrology as measure technique. In this work, we use OCT to measure thicknesses of films.
In OCT, depth profiles are constructed by measuring the time delay of back reflected light by interferometry
measurements. Frequency in k-space is proportional to optical path difference.
Then the reflectivity profile is obtained by a Fourier transformation, and the difference between two successive peaks of
the resulting spectrum gives the film thickness.
Several films, food-type, of different thicknesses were investigated and the results were very accurate.
Continuous Paul Wavelet is a suitable tool for direct phase distribution evaluation in the case of digital interferograms. The method is based on the correlation in the Fourier domain between the digitized ineterferogram and the optical Paul wavelet filter spectrums. This correlation can be made directly with a computer or in optical set-up using an addressable liquid crystals display. We present the technique and the obtained results on simulated interferograms.
Ellipsometry is a technique of surfaces analysis, founded on the measure of light polarization state after reflection on a plane surface. Work consists in characterizing the surface quality of polished optical glass by ellipsometry. The measured ellipsometric parameters enabled us to lead to a correlation with roughness while being based on the theory of Maxwell-Garnett to determine the optical properties of the effective milieu.
One of the most important properties of a laser resonator is the highly collimated or spatially coherent nature of the laser output beam. The spatial beam quality of the output beam, namely beam diameter and propagation factor M2 are critical parameters in a wide range of practical laser applications. This is because the spatial beam quality determines how tightly the beam can be focused or how well the beam propagates over long distances without significant spreading. It was investigated by many authors in previous years how to define and on how to measure the laser beam quality. An ISO working Draft Committee has also been organized to set-up a standard for definitions and test methods of the laser beam quality. In this work, the quality factor is studied with different methods.