AUTOMATIC WAVELENGTH CALIBRATION PROCEDURE FOR USE WITH AN OPTICAL SPECTROMETER AND ARRAY DETECTOR

Echelle spectrometers with cross-dispersion ate often used in emission spectroscopy owing to their high spectral resolution and good light t hroughput. The resultant two-dimensional dispersion plane is ideally s uited to array detectors such as the charge-injection device (CID) or charge-coupled device (CCD). The successful coupling of an echelle spe ctrometer with an array detector permits true simultaneous spectroscop y to be performed over a large spectral range. In order to correctly i dentify spectral features it is necessary to have an accurate waveleng th calibration function which maps the CCD/CID pixel co-ordinates to w avelength. A new approach to the wavelength calibration of optical spe ctrometers with array detection is proposed that does not involve a di rect modelling of the spectrometer dispersion. Instead, the difference between an ideal conceptual spectrometer and the physical instrument is modelled. The procedure is able to compensate for the effects of ma nufacturing tolerances and local temperature and pressure conditions. Preliminary results, obtained by simulation with a computer-modelled e chelle spectrometer, has shown that a sub-pixel accuracy in the predic ted position of spectral lines can be achieved over a temperature rang e 5-35 degrees C.