Digital Hilbert transformation for separation measurement of thicknesses and refractive indices of layered objects by use of a wavelength-scanning heterodyne interference confocal microscope

被引：0

作者：

Watanabe, Yuuki ^{[1
]}

Yamaguchi, Ichirou ^{[1
]}

机构：

[1] Optical Engineering Laboratory, RIKEN, Inst. of Physical and Chemical Res., 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

来源：

Applied Optics | 2002年 / 41卷 / 22期

关键词：

Demodulation - Digital signal processing - Heterodyning - Phase locked loops - Radio interference - Scanning - Spurious signal noise;

D O I：

暂无

中图分类号：

学科分类号：

摘要：

A wavelength-scanning heterodyne interference confocal microscope quickly accomplishes the simultaneous measurement of the thickness and the refractive index of a sample by detection of the amplitude and the phase of the interference signal during a sample scan. However, the measurement range of the optical path difference (OPD) that is obtained from the phase changes is limited by the time response of the phase-locked loop circuit in the FM demodulator. To overcome this limitation and to improve the accuracy of the separation measurement, we propose an OPD detection using digital signal processing with a Hilbert transform. The measurement range is extended approximately five times, and the resolution of the OPD is improved to 5.5 from 9 μm without the electrical noise of the FM demodulator circuit. By applying this method for simultaneous measurement of thickness and the refractive index, we can measure samples 20-30-μm thick with refractive indices between 1 and 1.5. © 2002 Optical Society of America.

引用

页码：4497 / 4502