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Displacement measurement system and method thereof

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TLDR
In this article, a displacement measurement system including a coherent light source, a two-dimensional grating, a photo sensor, and a signal processing apparatus is provided, where a zero-order light beam interferes with two first-order diffraction beams in different directions, so that corresponding interference fringes are formed on the photo sensor.
Abstract
A displacement measurement system including a coherent light source, a two-dimensional grating, a photo sensor, and a signal processing apparatus is provided. After the coherent light beam enters the two-dimensional grating, a zero-order light beam and a plurality of first-order diffraction beams are generated. The zero-order light beam interferes with two of the first-order beams in different directions, so that corresponding interference fringes are formed on the photo sensor. Accordingly, when the two-dimensional grating moves, displacements of the two-dimensional grating in the different directions are obtained by calculating phase differences of the interference fringes in the corresponding directions. Besides, when the two-dimensional grating rotates, the rotational angle of the two-dimensional grating is obtained from the corresponding rotational angle of a diffraction pattern of the first-order diffraction beams.

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Citations
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References
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Optical detection apparatus for detecting information relating to relative displacement of an object on whch a diffraction grating is formed

TL;DR: In this article, the authors propose an apparatus for optically detecting information relating to the relative displacement of an object on which a diffraction grating, arranged in two axial directions with a predetermined pitch, is placed.
Journal ArticleDOI

Simultaneous detection of translational and angular displacements of micromachined elements

TL;DR: In this article, an astigmatic detection system is constructed with a modified digital-versatile-disk optical head, with a detecting spot of ∼1μm, which can simultaneously measure the vertical displacements and two-dimensional angular tilts of micromachined elements.
Patent

Method for measuring two-dimensional displacement using conjugate optics

TL;DR: In this paper, a method for measuring two-dimensional displacement using conjugate optics comprises the steps of emitting an incident beam onto a diffraction element to generate many firstly diffracted beams, selecting two axially symmetric beams of the same order of diffraction from the first diffracted beam, introducing corresponding sets of wavefront reconstruction optics to reflect the two selected beams back onto the same incident spot along the same optical paths and generating many secondly diffracted beacons.
Journal ArticleDOI

Nanoscale displacement measurement in a variable-air-gap optical waveguide

TL;DR: In this paper, an alternative approach by monitoring changes in the intensity of the light reflected from a variable-air-gap optical waveguide is presented in order to detect slight displacement.