| Popis: |
AC interferometers based on modificated Michelson's scheme allow to terminate disadvantages of DC interferometers, such as a high level of photo-detector noises, an instability of laser output radiation and other noises of low frequency nature. In the scheme of AC interferometer laser beam in supporting channel is shifted at the rate of frequency relative to laser beam in measuring channel by means of devices, which are shifting frequency or converting one frequency coherent radiation into two frequency ones. They allow to carry the spectrum of interferometer signal to higher frequency region of discrimination of low frequency noises. The main problem of AC laser interferometers is the choice of effective converters, because the characteristics of last ones determine the accuracy, the dynamic range, the overall dimensions and the cost of the first ones. The goal of this paper is to compare metrological features of interferometers with two converters -- piezo-mirror and electro-optical device -- used by us in measuring practice. The questions which are considered: effect of coherent nature of laser radiation, extreme values of measuring frequency and amplitude of vibrations, extreme values of SNR and distance from testing surfaces, restrictions on view field and design parameters, most effective application areas. |
