1 April 1998 Characteristics of a high-resolution displacement sensor using mode interference in the optical waveguide
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A high-resolution optical displacement sensing system using an optical waveguide is fabricated and characterized. The measurement principle is based on interference between an even and odd modes in the double-mode waveguide. After the light from a laser light source is focused onto the object to be measured, a wavefront gradient in the converged reflected light beam from the object gives a phase asymmetry at the entrance of the double-mode (DM) waveguide. A change of the phase asymmetry due to the displacement of the object along the optical axis is detected as a change of light intensity distribution at the exit of the DM waveguide. Although the optical system is very simple, experimental results using Ti-indiffused LiNbO3 waveguide device shows a very high resolution less than 1 nm. Next, a compact-type displacement sensor module using silica waveguide is fabricated and shows an identical high resolution. In conclusion, it will be very useful as a built-in component for various kinds of the industrial equipment.
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Yutaka Iwasaki, Yutaka Iwasaki, Masaaki Doi, Masaaki Doi, Takashi Shionoya, Takashi Shionoya, Kazuya Okamoto, Kazuya Okamoto, } "Characteristics of a high-resolution displacement sensor using mode interference in the optical waveguide", Proc. SPIE 3275, Flatness, Roughness, and Discrete Defects Characterization for Computer Disks, Wafers, and Flat Panel Displays II, (1 April 1998); doi: 10.1117/12.304390; https://doi.org/10.1117/12.304390

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