SpectroMaster^®

The principle measurement setup is shown above. A fixed collimator is projecting the image of a slit target through the sample prism. An autocollimator mounted to the rotary air bearing goniometer is picking up the slit image and measuring the deviation angle of the refracted light passing through the prism. The illumination of the variable target slit is done by exchangeable spectral lamps, so that the measurements are done at precisely known wavelengths of selected spectral lines. For a better identification of certain spectral lines, narrow band interference filters can be moved into the beam path.

The autocollimator is also used for measuring the apex angle of the prism in reflection. It is supplied with a high-brightness LED illumination.

The sample is positioned on a fixed support centrally above the goniometer. With a rotary table, the incidence angle of the collimator beam with respect to the sample can be controlled. An optional linear stage can be used to move the prism to the optimum pivoting points for the apex angle measurement and the deviation angle measurement. The deviation angle measurements are done differentially on both sides of the collimator axis so that zero offset errors are suppressed.

The SpectroMaster^® UV-VIS-IR models are completely designed with reflective optics, e.g. off-axis parabolic mirrors as focusing elements in the collimator and autocollimator. Special UV-enhanced coatings guarantee high reflectivity over the full spectral range. The extended spectral range also requires the use of additional photo detectors besides the CCD. For the infrared a cooled PbS-detector and for the UV a photomultiplier is used. For a better signal-to-noise ratio, the input beam is chopped by a frequency stabilized chopper wheel and a lock-in amplifier is used to process the detector signal.