History
Optical measurement of surfaces on the macro and microscopic scale is becoming very important for scientific and industrial applications. The advantage of optical methods is non contact operation mode, the measurement speed and the damage free data acquisition. Different physical principles are used like time of flight, phase measuring as well as moiré techniques, triangulation, fringe projection, confocal microscopy, interferometry, holography, speckle, etc.
Since the early years at CIOp, several optical applications have been developed in order to measure surface roughness, velocity, refractive index, distances, displacements, deformations, cracks, contouring, etc.
In particular, several optical methods have been proposed in order to measure the statistical parameters associated with the height profile of diffuser surfaces, using the properties of scattered light, and depending on the r.m.s. roughness value of the inspected surface. The r.m.s. surface roughness measuring range is 1-30 microns.
Also, optical non-contacting methods are particularly appropriate for measuring the velocity of moving rough surfaces in industrial applications. We have proposed different speckle methods for measuring the linear velocity of a moving diffuse object. The measuring range is 0-40 m/s.
A fruitful approach to the studies of a liquid free surface was demonstrated. Using optical interferential techniques, the free surface of nonvolatile and volatile confined liquids were analyzed. Various wall container types were investigated. Besides the classical plane wall, experiments were performed by using cylindrical and toroidal walls.
An application for distance measurements based on the moiré optical technique was developed. Hidden grids from the photocopy process were used to produce moiré patterns. Distances in the range of hundred meters were measured with an uncertainty of 2%.