1. R. S. Mezrich, K. F. Etzold, D. H. R. Vilkomerson, “System for Visualizing and Measuring Ultrasonic Wavefronts;” Acoustical Holography, Vol. 6, N. Booth, Ed., Plenum Press, N. Y. (1975).
2. R. Mezrich, D. Vilkomerson, K. Etzold, “Ultrasonic waves: their interferometric measurement and display,” Appl. Optics 15, 1499 (1976).
3. A peak-detector can consist of a diode in series with a capacitor; the highest positive voltage charges up the capacitor to that value and it remains at the peak value until reset.
4. D. Vilkomerson, “Measuring Pulsed Picometer-Displacement Vibrations by Optical Interferometry,” Aopl. Phys. Lett. 29, 183 (1976).
5. M. Born and E Wolf, “Principles of Optics,” 3rd Ed. Pergamon Press, IvT, Y. (1965), page 691.