Dual beat-frequencies laser Doppler interferometer

Abstract

A dual beat-frequencies laser Doppler interferometer which can measure high speed back and forth motion is proposed and demonstrated. In this interferometer, the two frequencies, f(1) and f(2), emitted by a Zeeman laser are introduced into the signal beams. They are changed to f(1)' and f(2)' by Doppler shift f(Doppler), which is proportional to the velocity of the object. The use of the two beat signals of |f(1)' - f(2)| and |f(1) - f(2)'| appearing at two photodetectors enables to measure the velocity over the limitation v(c) = λ(f(1) - f(2))/2.

Micro-Movement Measured by Laser Heterodyne Interferometer Based on Acousto-Optic Effect

“…The laser heterodyne interferometer can measure the displacement, velocity, and acceleration of vibration target in real-time [1][2][3]. It has the characteristics of non-contact, anti-interference, high precision, and so on, and has been widely used in the precision displacement measurement of micronano devices [4,5].…”

High-speed impact test using an inertial mass and an optical interferometer

“…11 In DB-LDI, two laser beams with different frequencies are both used as reference and signal beams, which produce two beat signals. Although the velocity calculated from one of the beat frequencies reaches the critical velocity, the velocity calculated from the other beat frequencies is far from the critical velocity.…”

Frequency difference lock-in phenomenon’s weakening by transverse magnetic field in Y-shaped cavity dual-frequency laser

“…Orthogonally polarized dual-frequency lasers are widely applied in two-frequency interferometers, ellipsometers, displacement measurement, wave plate measurement, and other measuring systems [1][2][3][4][5] . However, for the He-Ne laser transitions there exists a lock-in frequency difference below which one of the polarized waves dies because of the strong competition among waves [6,7] .…”