Real-time imaging spectrometer

Abstract

An improved AOTF-based imaging spectrometer that has ability to electronically set the bandpass wavelength of an AOTF to any desired value in its wide tuning range, provides significant observational flexibility. This allows observations to be tailored in real-time and enables the spectrometer to address a wide range of objectives and permits real-time modification of the observational parameters, such as in flight or in other situations in which only remote control is possible. Various improvements in optical architecture provide simplified magnification variability, improved image resolution and light throughput efficiency and reduced sensitivity to ambient light. A preferred embodiment employs a camera zoom lens as the input lens. A TeO.sub.2 AOTF and a relay lens are placed at selected distances behind the back focal plane of the input lens, respectively. A charge coupled device (CCD) camera, which comprises a camera, camera zoom lens and a CCD detector is placed at a selected distance behind the relay lens. An RF signal generator is used to drive the AOTF. Two embodiments of the invention are disclosed herein. One operates in the visible/near-infrared domain, in the wavelength range of 0.48 to 0.76 microns. The other operates in the infrared wavelength range of 1.2 to 2.5 microns.