Phase locked loop based topography measurement of ultraprecision machined surface using the ball lensed and tapered fiber
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This paper presents the phase locked loop-based metrology concept using the lensed fibers for on-machine surface topography measurement. The shape of a single mode fiber at the endface was designed using an ABCD matrix method and two designed lensed fibers, ball type and tapered type, were fabricated and its performance was evaluated, respectively. In order to achieve the on-machine measurement of the surface tophography with a high resolution, each fiber was characterized under the following conditions; small beam spot size, long working distance and high coupling efficiency. A piece of coreless silica fiber was spliced to a single mode fiber and a micro-sized lens or tapered shape on coreless fiber endface was formed for the ball lensed fiber. As a result, the interferometric fringe was not found in the case of the ball lensed fiber, but the ultraprecision machined Cu surface could be measured by autofocusing and intensity methods. Two results were well agreed. On the other hand, very clear Fizeau interferometric fringe was observed in the case of the tapered lensed fiber. Its performance was compared with the results of the capacitance sensor and a commercially available white-light interferometer. Two results were well agreed. As a result, it was confirmed that the PLL based surface profile measurement using the tapered and ball lensed fibers can be applied for on-machine surface topography measurement. © 2012 SPIE.
author list (cited authors)
Lee, C., Kang, J., Joo, J., & Lee, S.