PROCESS AND DEVICE FOR THE CONTACTLESS MEASURING OF THE POSITION IN SITU AND/OR OF THE PROFILES OF ROUGH SURFACES

摘要

The invention is directed to a method and apparatus for the contact-free measurement of the actual position and/or of the profile of coarse surfaces. Laser light generated by a laser has at least two different wavelengths and is directed to the surface to be measured. A beam splitter is placed between the surface to be measured and the laser to split the laser light into a reference beam and a measuring beam. The reference beam is reflected on a reference plane surface. A speckle pattern is formed in the interferogram plane of the reflected light. From the speckle pattern, a bright laser speckle is selected for all wavelengths by means of a measuring diaphragm having a diameter less than that of a laser speckle. Behind the measuring diaphragm, the two wavelenths are separated from each other and the phase difference between the signals of the different wavelengths is measured. The phase difference is transformed into a signal proportional to the distance between the measuring point and the reference surface and is displayed. The reference light beam can be shifted in frequency with respect to the measuring beam by means of a heterodyne device.