Adaptive Filtering and Hadamard Transform Imaging Spectroscopy with An Acousto-Optic Tunable Filter (AOTF)

The acousto-optic tunable filter (AOTF) is a compact, rugged, solid-state spectrometer well suited to high frequency amplitude control and wavelength selection. The AOTF utilizes radio frequency (rf) acoustic disturbances in transparent materials to establish an electronically controllable diffraction grating. By launching the combination of several rf signals into the AOTF, multiple wavelengths of light can be diffracted simultaneously and light can be adaptively filtered to match the spectral profile of the sample. In addition, Hadamard transform (HT) spectroscopy can be performed with an AOTF serving as the polychromator. The integrated intensity on the detector is the combination of the encoded transmission or reflectance wavelengths. Hadamard transformation mathematics govern the multiplexed sequence allowing the efficient recovery of the spectrum. We describe the multiplexed AOTF spectrometer design as well as the design of a maskless HT imaging system