Program for performing photometric calibration of reflectance data

The program below allows you to perform photometric calibration of reflectance data from SHINE and SHADOWS goniometers.

• It can read the 13-column “full” file format provided by the goniometer software.
• It takes the measurement geometry into account in the calibration. The values must be entered manually or can be read automatically from the file name for BRDF measurement series.
• It allows the “dark” signal (without illumination) to be subtracted from the two detectors: visible (Si) and near-infrared (cooled InSb). Their values can be provided in the header of the input file or manually. The detector change wavelength must be provided with “VIS-NIR transition”.
• It performs:
  1) absolute reflectance calibration with the measurement of the “Spectralon” reference target in the visible and very near-infrared ranges.
  2) relative calibration of the rest of the near-infrared range with the “Infragold” reference target, which it then calibrates absolutely to the “Spectralon-Infragold” transition wavelength chosen by the user in “reference transition”.
• It provides a standard set of spectral calibration files for the “Spectralon” and “Infragold” targets, as well as the BRDF of the “Spectralon”, but it is also possible to replace them with your own curves.
• It can perform this calibration on one or more spectra, as well as on series of spectra with variable temperature or variable angles (BRDF). In the latter case, it can also perform calibration with a series of measurements at the same angles of the Spectralon reference target.
• The graphical tool allows you to visualise the measured signal and the calibrated reflectance.
• In the case of series of BRDF or temperature spectra, the export provides a choice between individual saving of the spectra in the initial “full” format and/or a synthetic file that compiles all the spectra in the series (“reflectance + error”). The order of priority of the angles of incidence and azimuth can also be chosen.
• It also allows you to convert the measurement angles given in the “remote sensing” angular reference into “physical” values when saving the file.

The following document presents all the details of the calibration procedure :

The “SpectroCalibration” programme must be unzipped to run, keeping the “calibration_references” directory next to the executable file:

After calibration you can perform a ’correction of grating and detector shifts’ and/or a ’correction of multiple reflections between sample and window’ if you used a cryogenic or thermal cell.