| Abstract: |
The amplitude, frequency, direction or phase of the light scattered bya medium provides a means for determining characteristics of the mediumwithout physical contact, and this principle has been used in spec-trometers, interferometers, and numerous other laboratory applications.In the decade since the introduction of the laser, the interest inthese techniques has been greatly intensified by the availability ofan intense light source with well-defined frequency and phase charac-teristics, and of specific interest is the use of these properties toprovide velocity measurements. Various arrangements have been devisedfor measuring the Doppler shift of the scattered laser light which isthen related to the velocity of the scatterer by physical constants ofthe system, and the analysis of these techniques has been exclusivelylimited to Doppler principles. It is interesting to consider thesedevices from the viewpoint of diffraction theory, rather than Doppler,and examine the effects of various parameter variations in terms ofthe resulting models. In the following discussion, diffraction modelsare developed for the most common techniques of velocity measurementusing gas lasers.
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