Near-IR imaging microscopy using an acousto-optic tunable filter (AOTF)

Abstract

Near-infrared spectroscopy is a sensitive and non-invasive probe for chemical analyses. The integration of spectroscopic and imaging technologies is a potent tool for the study of a wide range of biological materials.Continuously tunable acousto-optic filters operable in the ultraviolet, visible and infrared are now widely available. These computer controlled notch filters provide random wavelength access, wide spectral coverage and moderate spectral resolution. AOTFs potentially have a wide range of spectroscopic applications. We employ AOTF technology for visible/NIR absorption microscopy between 600-2000 nm.The microscope is constructed around an acousto-optic device coupled to an infinity corrected microscope employing either silicon or indium antinomide focal-plane array detectors. In operation, the AOTF is used to spectrally filter a quartz halogen light source. Under computer control the AOTF is swept through a wavelength range and at predetermined intervals images are recorded. Hundreds of frames may be collected, and the spectral image data set can readily comprise many megabytes of data.