2個の高輝度LEDと垂直走査型干渉計を用いる高速nm精度形状計測

概要

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We propose a high-speed vertical scanning profilometry which has nanometric height precision. The proposed profilometry is equipped with two short-coherent-light sources, which are made of extremely-high-power light emitting diodes (LED). In 3-D profile measurements, the profilometry acquires many interferograms while vertically scanning a Mirau-type objective with 0.407-μm movement/interferogram and alternately-flashing LED. Odd-numbered interferograms are acquired with 503-nm LED and even-numbered interferograms are with 591-nm LED. Regarding the acquired interferograms, a computer calculates phase and modulation contrast using a phase-shifting technique. As two movements are repeated between acquirements of the same-color interferograms, phase step corresponds to approximately 6π+π/2 with 503nm and approximately 6π-π/2 with 591nm respectively. After searching the interferogram having a contrast peak, the computer extracts optical path difference of the searched interferogram with nanometric resolution from the phase information. From the vertical movement length of 0.407μm and a frame rate of 111Hz, a vertical scanning speed is given as 45.2μm/s. Nanometric height precision of the profilometry is checked using the measured data of a step height standard.
社団法人精密工学会の論文
2005-11-05