A prerequisite for correct radiometric measurements is the precise calibration of the spectrometer used. With its Calaris software module, Instrument Systems provides a versatile calibration software package for maintenance and recalibration.

Within the SpecWin Pro software the optional Calaris module will guide you chronologically and reliably through the various calibration steps. It will enable you to calibrate all current array spectrometers of the CAS series from Instrument Systems with accessories, thus avoiding the time-consuming return of your spectrometer.

Essentially, spectroradiometer are calibrated in three steps:

Wavelength calibration

A defined wavelength value is assigned to the individual pixels on the CCD sensor. Particularly in the case of array spectrometers, as many calibration points as possible should be evenly distributed over the entire spectral range. Gas discharge lamps or lasers can be used for the calibration.

Spectral calibration
In this calibration step the relative spectral sensitivity of the spectrometer is determined. The latter is measured primarily from the sensitivity of the detector, grating and optical probe used. A broadband light source (e.g. FEL lamp) with known spectral data that is traceable to a national calibration lab is used for the calibration.

Absolute calibration
Here the spectral calibration is adjusted by a correction factor so that the radiometric or photometric value determined for a measured light source matches the correct absolute value of the light source. FEL lamps or LEDs that are traceable to a national calibration lab are used as light sources.

Depending on the spectrometer type or accessories used, further calibration steps may be necessary for density filters or TOP accessories.

The Calaris module operates with so-called calibration projects, in which all calibrations of an instrument are stored. The file format for calibration projects is *.icp (Instrument Systems Calibration Project).

For carrying out calibrations the following prerequisites must be met:

• A calibration project or configuration and calibration file for your spectrometer.
• The necessary calibration equipment (radiation sources, apertures, etc.).