Abstract: A method for the determination of characteristic layer parameters by means of spectral-optical measurements, that allow for precise measurements of the sample temperature even under the conditions of industrial growth processes and furthermore avoids the detection of thermal radiation and reflected radiation by means of twofold phase sensitive frequency modulation by using so called chopper and lock-in amplifier respectively. The wobbling and/or rotating of the sample to be measured is compensated and/or the pyrometer optical path and the optical path of the spectral-optical system are guided separately of each other and/or a separation of the radiation signal for the temperature measurement and the radiation signal for the spectral-optical measurement is implemented by blanking of the irradiated light.

Abstract: The invention relates to a device and a method for the measurement of the curvature of a surface (1). It is the object of the present invention to provide a device for the determination of the curvature of a surface (1), that is more exact and less expensive as the devices of the prior art. Therefore the device comprises a light source (2) for the irradiation of a light beam (3) onto the surface (1), in which a birefingent element (4) is arranged between light source (2) and surface (1), in which furthermore a detector (5) is arranged for the detection of the partial beams (6,7), that are reflected at the surface (1), and at least one main axis (17) of the birefringent element (4) is positioned with respect to the light beam (3) of the light source (2) in such a way, that the light beam (3) of the light source (2) is split up into at least two parallel beams (6,7), if necessary with the help of additional optical elements.