Amplitude and phase modulation (AM-PM) wide-band photothermal spectrometry. I. Theory

Power, J. F.
January 1990
Review of Scientific Instruments;Jan1990, Vol. 61 Issue 1, p90
Academic Journal
Amplitude and phase modulation (AM-PM) wide-band photothermal spectrometry is a new technique of excitation and signal recovery with extensive applications in thermal-wave imaging using linear photoacoustic and photothermal techniques. The excitation waveform consists of the superposition of two orthogonal amplitude-modulated frequency sweeps, and exhibits an optimally fiat input autospectrum over an arbitrary bandwidth. Signal quality is greatly superior to earlier wide-band photothermal methods based on linear frequency sweep excitation. The new methodology also permits "multiband acquisition" in which several arbitrary narrow-band segments or "slices" of the photothermal frequency response are acquired, a capability that is missing in conventional linear FM measurements. This multiband acquisition capability has many potential applications for information recovery in thermal-wave imaging.


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