Interference Confocal Microscope Integrated with Spatial Phase Shifter.

Weibo Wang,Xiaoyu You,Kang Gu,Jian Liu,Jiubin Tan

doi:10.3390/s16091358

Abstract

We present an interference confocal microscope (ICM) with a new single-body four-step simultaneous phase-shifter device designed to obtain high immunity to vibration. The proposed ICM combines the respective advantages of simultaneous phase shifting interferometry and bipolar differential confocal microscopy to obtain high axis resolution, large dynamic range, and reduce the sensitivity to vibration and reflectance disturbance seamlessly. A compact single body spatial phase shifter is added to capture four phase-shifted interference signals simultaneously without time delay and construct a stable and space-saving simplified interference confocal microscope system. The test result can be obtained by combining the interference phase response and the bipolar property of differential confocal microscopy without phase unwrapping. Experiments prove that the proposed microscope is capable of providing stable measurements with 1 nm of axial depth resolution for either low- or high-numerical aperture objective lenses.

Highlights

For the non-contact 3D measurement of Micro-Electro-Mechanical System (MEMS) and micro-optics, both deep micro-topographic structures and surface roughness have to be controlled during the same measurement procedure, preferably with the same instrument
We present a phase-shifting confocal microscope using a complicated novel single-body wavelength modulation
An interference confocal microscope integrated with a new single-body four-step simultaneous

Summary

Introduction

For the non-contact 3D measurement of Micro-Electro-Mechanical System (MEMS) and micro-optics, both deep micro-topographic structures and surface roughness have to be controlled during the same measurement procedure, preferably with the same instrument. Confocal Microscopy has a very large dynamic range and an optical sectioning capability of less than 1 to 2 microns [1,2], and Phase Shift Interferometry (PSI) has a very high resolution inside a very short dynamic range. To obtain high axis resolution and large dynamic range similar to coherence scanning interferometry (CSI)—e.g., Bruker’s Contour Elite 3D Optical Microscope (combining vertical resolution with a sub-nanometer to greater than 10 mm vertical range) and ZYGO’s NewViewTM 7000 Series surface profiling system (Surface Topography Repeatability (STR) is sub-nanometer, Max. Step Height is up to. The basic property of optical sectioning inherent to confocal imaging is well-adapted to PSI, since it automatically solves the critical and time consuming problem of phase unwrapping computation [4]

Methods

Results

Conclusion