Laser Doppler velocimetry using a bulk optic Michelson interferometer: A student laboratory experiment

Abstract

The Doppler frequency of reflected light from a moving mirror is measured using a Michelson interferometer and a low cost spectrum analyzer. The experimental data for the Doppler frequency are in agreement with the calculated theoretical values with a standard percent error of 0.54%. The concept of optical mixing of a phase-modulated signal with the Doppler signal is presented, with a derivation of the resulting detected signal power, using the small phase modulation amplitude approximation. An experiment is described using laser Doppler velocimetry to heterodyne the Doppler signal with an acoustic wave. The experiment provides a good illustration of the Doppler effect, spectral analysis, and principles of optical mixing and interferometry in an advanced undergraduate laboratory.

Laser interferometric characterization of a vibrating speaker system

“…The expression for the output voltage V D from the photodetector can be derived from the well-established wave analysis of two-beam interference 6,13 and may be written as…”

“…However, despite the fact that there is extensive coverage on this subject in the technical literature, there are relatively few papers devoted to the use of the laser Doppler technique in undergraduate laboratories. [5][6][7][8] This work presents a very simple laser vibrometer suitable for characterizing electromechanic transducers such as dynamic loudspeakers. The aim is to give the student a general introduction to the Doppler effect, optical interference, and vibration analysis, by illustrating an application of the laser Doppler technique in the field of acoustics.…”

Experimental investigation of acousto-optic communications

“…The reflected beam, containing the Doppler information, is detected and recombined with the RF modulated reference beam within the interferometer. As a result of heterodyne mixing of the laser beams, an analog voltage signal, V, containing Doppler information of the normal surface velocity, v, is then obtained, as indicated in (1). K is the conversion efficiency constant of the optical detection, f 0 is the heterodyne frequency shift of the interferometer reference beam, λ is the optical wavelength, and t is time.…”

“…Interferometric techniques using coherent laser radiation to measure the acoustic signals on a vibrating surface are presented by Belansky and Wasner [1].…”

A Michelson-type radio interferometer for university education

“…[9][10][11][12] Many studies and applications of the Michelson Interferometer have appeared in this journal, [13][14][15][16][17][18][19][20][21][22][23] and it is even currently being applied to the detection of gravitational waves. [24][25][26] The Michelson stellar interferometer is an application of the same physical concept of interference, in this case to a light source in the sky.…”