Data collection with a dual-band infrared hyperspectral imager

摘要

A novel dual-band hyperspectral imaging system has been used to collect field test data for robotics vision applications. The imaging system can collect full scene hyperspectral images in both the long-wave infrared (LWIR) band (8-10.5 μm) and the mid-wave infrared (MWIR) band (4-5.25 μm) simultaneously. The imager uses a specially designed Ge diffractive lens with a dual-band 320x240 HgCdTe infrared focal plane array (FPA) cooled with a Sterling cooler. The stacked FPA consists of two layers: the top one sensitive in the MWIR region and the bottom one sensitive in the LWIR region. The diffractive lens is designed to focus a first order, single-color (i.e., 8.0 μm) image in the LWIR onto the bottom layer of the FPA while at the same time focusing a second order single-color (i.e., 4.0 μm) image in the MWIR onto the top layer of the FPA. Images at different wavelengths are acquired by moving the lens along its optical axis. Moving the lens over the entire range during data collection allows sequential collection of spectral images in each band resulting in the collection of two complete image cubes. The focal length of the lens is 75 mm at 9 μm. The spectral resolution of the imager is 0.1 μm at the 9 μm wavelength. In general, 128 narrow wavelength bands are collected in each of the two broad spectral regions. After data collection, the images are processed to remove noise, contributions from unfocused wavelengths, and magnification differences. A description of the imager, data collection, noise removal, post-processing, and analysis are presented.