title: Sinusoidal phase-modulating self-mixing interferometer with nanometer resolution and improved measurement velocity range.
abstract: A new signal-processing method based on an electronic frequency down-conversion technique has been introduced into a sinusoidal phase-modulating, self-mixing interferometer. The developed interferometer employs an electro-optical crystal placed in the external cavity of a He-Ne laser to generate the sinusoidal phase modulation with high modulation rate and ultralow insertion loss. Phase quadrature signals which have been amplitude-modulated by the sine and cosine functions, respectively, of the measured displacement can be extracted from the high-density optical fringes through the use of dual-channel multiplier/filter circuits. Therefore, the displacement of the external target can be retrieved from the phase quadrature signals with nanometer resolution and high computational efficiency. Moreover, a much-improved measurement speed from 2.5 to 22  mm/s has been realized owing to the simplified signal-processing method. The performance of the proposed interferometer has been experimentally verified by comparison to an Agilent 5529A dual-frequency laser interferometer. The measurement results from the two instruments agree well, and we therefore expect that our new technique offers a powerful instrument for high-speed metrology sciences.
authors.forename: Wei
authors.initials: W
authors.lastname: Xia
authors.forename: Qiang
authors.initials: Q
authors.lastname: Liu
authors.forename: Hui
authors.initials: H
authors.lastname: Hao
authors.forename: Dongmei
authors.initials: D
authors.lastname: Guo
authors.forename: Ming
authors.initials: M
authors.lastname: Wang
authors.forename: Xuzong
authors.initials: X
authors.lastname: Chen