Study On HyperSpectral Imager Based On Digital Filter

Spectral imaging technology is a new measure technology which provides spectral images at many different wavelet bands and generates precise optical spectra at every pixel. The data that spectral imager got is called spectral data cube. Because of the spectral dimension and position dimensions, spectral imaging technology provides both the spatial information of sample which is the feature of imaging technology and spectral information that spectral measurement gives. The spectral imaging is used in fields of military affairs, agriculture monitoring, biomedicine and material evidence detection.In laboratory, a monochromator, band filters and electric-adjustable filters are used to build the staring imagers. By using this kind of spectral imager, the image of whole view is imaged at one change. Slit is needed in the spectral imager using prism and grating. The slit width and spectral resolution are contradiction. Slit is not considered in spectral imager using optics filters, the number of which is limit. Recently, spectral imager using liquid crystal tunable filter which can be controlled by computer provides innovative method to get images of continuous wavelength coverage, but the filter has limit spectral range, low transmission rate. In addition, the liquid crystal tunable filter is too expensive to small test experiment. For those questions, an innovative hyperspectral imager is studied in this paper. The hyperspectral imager in the paper provides continuous spectral imaging coverage and tunable band width with advanced luminous flux.The hyperspectral imaging system with easy achieve and low cost adopts reflected WDF Wadsworth monochromator using prism as dispersive device to get continuous spectral channels. The spectral resolution of system can be better than 2nm in the experiment. The slit of WDF Wadsworth monochromator is wiped off to advance the intensity in the surface of object. The change makes the calculation of data cube complex. System calibration and wavelength computation method is designed using traditional calibration method to solve nonlinearity character of prism. Digital filter is used to get spectral data cube. Spectral response of object is calculated by using hyperspectral imager based on digital filter.In this dissertation, hyperspectral imager system composed of WDF Wadsworth monochromator, lens, light source, CCD camera, motor and personal computer is established in laboratory. Software system is programmed for motor controlling, image capturing, storage and processing.Mercury lamp is used for system calibration as light source for calibrate experiment. The error of wavelength calculation is less than 2nm by using calibration parameter, which is acceptable in this experiment. The spectral imaging experiment of green leaf and analogues of green color is done using the hyperspectral imager. The spectral data cube and spectral response are got by using digital filter. The hyperspectral imager can be used in the spectral imaging experiment of small object in visible spectral range for getting unmixed spectral imaging, object identification and discrimination in the lab.Key Words:digital filter; hyperspectral imager; calibration; data cube...