A CCD Camera-based Hyperspectral Imaging System for Stationary and Airborne Applications

This paper describes a CCD (charge coupled device) camera-based hyperspectral imaging system designed for both stationary and airborne remote sensing applications. The system consists of a high performance digital CCD camera, an imaging spectrograph, an optional focal plane scanner, and a PC computer equipped with a frame grabbing board and camera utility software. The CCD camera provides 1280(h) x 1024(v) pixel resolution and true 12-bit dynamic range. The imaging spectrograph is attached to the camera via an adapter to disperse radiation into a range of spectral bands. The effective spectral range resulting from this integration is from 457.2 nm to 921.7 nm. The optional focal plane scanner can be attached to the front of the spectrograph via another adapter for stationary image acquisition. The camera and the frame grabbing board are connected via a double coaxial cable, and the utility software allows for complete camera control and image acquisition. The imaging system captures one line image for all the bands at a time and an aircraft or the focal plane scanner serves as a mobile platform to carry out pushbroom scanning in the along-track direction. The horizontal and vertical binning capability of the camera makes it possible to obtain images with various spatial (160, 320, 640 and 1280 pixels in image width) and spectral (32, 64, 128, 256, 512 and 1024 bands) resolutions. Formulas are presented to show the relationships among binning factors, spatial resolutions, and flight height and speed. Images with all 24 possible combinations of binning factors were collected in a laboratory setting. Airborne images with 128 bands and a width of 640 pixels were also obtained from agricultural fields, rangelands and waterways. Procedures were developed to correct geometric distortions of the airborne hyperspectral imagery. Preliminary image acquisition testing trials indicate that this CCD camera-based hyperspectral imaging system has potential for agricultural and natural resources applications. Geocarto International, Vol. 18, No. 2, June 2003 E-mail: [email protected] Published by Geocarto International Centre, G.P.O. Box 4122, Hong Kong. Website: http://www.geocarto.com 72 spectrographs, and tunable wavelength filters. The integration of a PGP spectrograph and a focal plane scanner is an innovative approach to airborne and laboratory pushbroom hyperspectral imaging (Mao, 1999, 2000). The hyperspectral focal plane scanner scans an input image within the focal plane of a front lens to accomplish the task of pushbroom scanning, while the PGP spectrograph disperses an input line image vertically, as a function of the spectral wavelengths, and focuses a two dimensional output spectral matrix onto the sensor surface of a CCD camera. This integration eliminates the need for a mobile platform for ground and laboratory data acquisition and allows the imaging system to be used for both airborne and laboratory applications. Through a research agreement, ITD/Spectral Visions at Stennis Space Center, Mississippi, developed a CCD camera-based hyperspectral imaging system for research use at the USDA-ARS Kika de la Garza Subtropical Agricultural Research Center at Weslaco, Texas. This paper describes the hyperspectral imaging system and demonstrates with sample imagery its potential for agricultural and natural resources applications.