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1 October 2006 Principle of a novel displacement-sensing He-Ne laser with self-calibration and high resolution
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The principle for utilizing a full-external-cavity He-Ne laser as a displacement sensor is presented. Inserting a quartz plate into the cavity, we split one laser frequency into two orthogonally polarized beams (o light and e light). When one cavity mirror is moved along the laser axis, we obtain power-tuning curves for o light and e light, in which equal-intensity points appear periodically, one period corresponding to λ/2 displacement. Moreover, four different polarization states in the laser output appear periodically. Attaching the moving mirror to the measured object, we realize displacement measurement with resolution of λ/2 through counting the number of equal-intensity points. We measure displacements less than λ/2 by means of a PZT mounted to the other cavity mirror. An increasing voltage is applied to the PZT to displace the mirror. Once the two beams reach the neighboring equal-intensity point, we note down the voltage variation of the PZT to get the true displacement. We discriminate displacement directions by sensing the order of appearance of the four polarization states. This system can be expected to afford a measurement range of ≈ 35 mm and a resolution of 10 nm, and has the capability of self-calibration. The potential error factors are also discussed.
©(2006) Society of Photo-Optical Instrumentation Engineers (SPIE)
Xiaoyan Liu, Shulian Zhang, Weixin Liu, and Xinjun Wan "Principle of a novel displacement-sensing He-Ne laser with self-calibration and high resolution," Optical Engineering 45(10), 103601 (1 October 2006).
Published: 1 October 2006

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