Data acquisition

One of the most important tasks in preparation for data acquisition is to focus the object under investigation. The wavelength at which the detector has the highest sensitivity or quantum efficiency should initially be selected as the focal point. With known samples, it is of course also possible to focus on a defined wavelength (which is of particular interest for the evaluation). Particularly in the VNIR range, the possibility of binning (spectral and/or spatial summation of pixels on the detector) to increase intensity or minimize noise should also be examined. With higher intensities, in turn, the exposure time can be reduced and the recording frequency increased. In order to achieve a reliable evaluation of the hypercubes, necessary corrections such as bright and dark reference correction should already be carried out during data acquisition.

Typical spectroscopic corrections to avoid detector and system influences in measurements

Bright field correction (or white reference or background correction) is carried out, for example, on optical PTFE, silicon wafers or similar spectrally inert materials. Dark field correction removes the detector offset from the data. Missing pixel detection is also important for MCT detectors. This is used to spectrally interpolate defective pixels (light and dark pixels, indicators) on the detector. 
Depending on the spectral resolution and spatial resolution, the resulting hypercubes can quickly reach sizes of several gigabytes. The way in which the hypercubes are viewed can vary: on the one hand, n images (with n = number of spectral bands/wavelengths) are available for data evaluation while on the other hand x*y spectra are available.