Hagen, C. L. Fundamentals of Transient Thermal-Light Absorption Spectroscopy and Application To Optical Sensing in HCCI Engines. University of Wisconsin-Madison, 2006.
A set of equations is developed for evaluating absorption spectroscopy based on thermal emitters such as lamps. The noise sources considered are photon (shot) noise and beating (wave interference) noise; signal-to-noise ratio limits for transient sensing with thermal light are also defined as a result of the analysis herein.
The set of equations developed is used to evaluate three real absorption experiments: one which uses a thermal emitter, another which uses an external cavity diode laser, and one more which uses a supercontinuum source. In each experiment species concentration measurements are made in a homogenous charge compression ignition engine.