Hadamard transform techniques in photothermal spectroscopy

Hadamard transform imaging is shown to be generally applicable to any linear spectroscopy and to be useful where locally high power densities are undesirable. Application to transverse photothermal deflection and Raman spectroscopies is reviewed. The modulation transfer functions (MTF) of both source‐encoded and signal‐encoded Hadamard imagers are described. Preliminary results from a signal‐encoded imager are presented.