Chromatic confocal microscopy with a novel wavelength detection method using transmittance

Taejoong Kim,Sang Hoon Kim,DaeGab Gweon,Hongki Yoo,DukHo Do

doi:10.1364/oe.21.006286

Abstract

Chromatic confocal microscopy (CCM) is a promising technology that enables high-speed three-dimensional surface profiling without mechanical depth scanning. However, the spectrometer, which measures depth information encoded by axial color, limits the speed of three-dimensional imaging. We present a novel method for chromatic confocal microscopy with transmittance detection. Depth information can be instantaneously obtained by the ratio of intensity signals from two photomultiplier tubes by detecting a peak wavelength using transmittance of a color filter. This non-destructive and high-speed surface profiling method might be useful in many fields, including the semiconductor and flat panel display industries, and in material science.

Highlights

The demand for fast three-dimensional (3D) microscopy has been growing in many industrial fields, including the manufacturing process of semiconductors and flat panel displays [1]
We proposed a novel method of detecting a peak wavelength for confocal microscopy (CCM) using an optical filter
We successfully demonstrated 3D surface profiling of a standard sample with a step height

Summary

Introduction

The demand for fast three-dimensional (3D) microscopy has been growing in many industrial fields, including the manufacturing process of semiconductors and flat panel displays [1]. White light interferometry provides nanometer depth resolution, but the surface profiling speed is not as fast due to the need for mechanical axial scanning [4]. Confocal scanning microscopy provides submicrometer resolution with high-speed surface profiling, 3D speed is still limited due to mechanical axial scanning [5]. The method for depth measurement with the use of axial chromatic aberration was applied to confocal microscopy [10,11,12]. While utilizing the same basic concept of an axial chromatic aberration as previously presented, depth information is acquired by use of the optical filter instead of using dispersion grating and a line array detector. Since the transmittance of light can be measured much faster than the whole spectrum, the proposed method has great potential for ultrahighspeed 3D surface profiling

Principles

Depth measurement process

Source

Optical filter

System performance

Conclusion