Design and comparison of multi- and hyper-spectral imaging systems

Abstract

Based on the requirements in several applications of object and surface remote identification, and considering the advantages of using multispectral techniques, several systems that allow image acquisition in both specific subbands and single wavelengths have been developed by our group. These systems are based on different techniques. They comprise visible and NIR ranges, with different spectral resolution. Three experimental setups have been developed. The first system is a camera with a filter wheel to choose different spectral bands. The second setup consists of a high-speed camera in which a 1 nm-resolution liquid crystal tunable filter has been assembled. The full system is automatic and allows a fast scan of visible subbands. The third setup uses the same imaging sensor as system #2, but in this case the filter has been substituted by a slit-spectrograph which splits the visible radiation into the different wavelengths that compose the small area observed. The desired wavelength is therefore selected by extracting the appropriate columns of the image acquired from the sensor. The correlation between wavelengths and the CCD array is determined in previous calibration steps. An additional rotatory stage allows the scanning of scenes. Software has been developed to control the systems and make automatic measurements. A new file format specially developed for this project allows the storage of all the images acquired in a single file, which allows a faster ulterior spectral analysis. A bands selection application simplifies the image acquisition depending on the observed scene. The images obtained by the systems will be analyzed in some subsequent stages: qualitative and behavioural study of the elements in the scene, comparison of resolution and operation capabilities of the different configurations and image calibration.