| Summary: | 碩士 === 清雲科技大學 === 電子工程研究所 === 94 === In this research, a novel instrument for measuring small displacement by uses of the
surface plasma resonance (SPR) technology, the principles of total internal reflection (TIR) and heterodyne interferometry is presented.
As a heterodyne light source focuses on a mirror which is drived by a PZT, the reflected light is incident on a beam-splitter and then its reflected light is refracted into the hypotenuse of a right-angle prism. At first, the light is incident on a side of the right-angle prism (the surface of the side is uncoated metal). And then, the reflected light is incident on the other side that is coated with two layes of metal films. Finally, the light is detected by a photo-detector when it passes through the hypotenuse of the right-angle prism and an analyzer. We can achieve the phase difference variation between the s- and p-polarizations by a lock-in amplifier. For many noncommon-path optical measurement systems, the turbulence of environment, such as air interference or mechanical vibration, will interfere the results, and decreases the measurement resolution. With the novel instrument a small displacement can be obtained by measuring the phase difference between s- and p-polarizations. The displacement resolution of the method can reach 0.1 nm by numerical simulation. The method has some merits, e.g., a simple optical setup, high resolution, high sensitivity, rapid measurement, and high stability, etc.
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