The new version of the Photonfocus HyperSpectral SDK is a software tool designed to test hyperspectral imaging (HSI) cameras and guide the generation of hypercubes. The tool supports all vendor cameras using IMEC (Leuven, Belgium) HSI mosaic and line scan sensors. The SDK includes a wizard to guide the calibration process and code examples to help the user in the first implementation steps.
Hyperspectral sensors are designed to work in a specific spectral range. Bandpass optical filters are used avoid spectral leaking and unwanted second order responses outside of the sensor's active spectral range. IMEC HSI sensors are calibrated with previous knowledge of the filters used to compensate the possible errors or mismatches due to the filter effect. The SDK is able to parse the information of the XML calibration file provided by IMEC and use it for the spectral correction.
Reflectance calculation reduces the influence of the light source spectra, avoids saturation and optimizes the dynamic range of the hyperspectral imaging system. The computed reflectance enables the comparison of the object spectra with available databases. In addition, demosaicing is used to compensate the effects of the mosaic pattern in the hyperspectral image. This is done by resampling the data of each band into the same regular grid, so that all bands of the spectral image are aligned.
Spectral correction recomposes a raw spectrum into a corrected spectrum, removing higher-order and cross-talk signals from the spectrum and avoiding spectral contributions from unwanted bands. Once the spectral correction is applied to the reflectance hypercube, the available bands change in frequency and number.
The resultant hypercubes are stored in a ENVI Band Sequential (BSQ) file format, which contains a header file with the system setup and sensor information and a file containing the hyperspectral data. ENVI output files can be opened and analyzed by numerous image processing tools, such as Matlab.