METHOD AND DEVICE FOR THE CONTACT-FREE MEASUREMENT OF THE ACTUAL POSITION AND/OR THE PROFILE OF ROUGH SURFACES

摘要

Laser light having at least two different wavelengths is directed to the surface (8) to be measured. On the path of the light beams there is arranged a ray divider (4) generating a reference light beam which is reflected on a reference plane surface (5). In the interference plane of the reflected light a frange pattern is formed amongst which a bright laser frange is selected for all wavelengths by means of a measuring diaphragm (31) of which the diameter is smaller than that of a laser frange. Behind the measuring diaphragm (21), the two wavelengths are separated from each other and the phase difference between the signals of the different wavelengths is measured. Said phase difference is transformed into a signal proportional to the distance between the measuring point and the reference surface and is displayed. It is advisable to frequency-shift the reference light beam with respect to the object light by means of a heterodyne device (7).