Abstract
A snapshot multi-wavelength interference microscope is proposed for high-speed measurement of large vertical range discontinuous microstructures and surface roughness. A polarization CMOS camera with a linear micro-polarizer array and Bayer filter accomplishes snapshot multi-wavelength phase-shifting measurement. Four interferograms with 𝜋/2 phase shift are captured at each wavelength for phase measurement, the 2𝜋 ambiguities are removed by using two or three wavelengths.
Highlights
Interference microscopes are commonly used to measure the surface shape and roughness of continuous and discontinuous surfaces [1]
One of the limitations in single wavelength interference microscopy is that the optical path difference (OPD) between two adjacent measured points must be less than λλ/2
The measure results of surface root mean square (RMS) are 8.62 nm from the R channel shown in Fig. 7(a), 8.78 nm from the G channel shown in Fig. 7(b), and 8.74 nm from the B channel shown in Fig. 7(c), compared to 8.36 nm measured by Zygo white light interference microscope Newview 8300
Summary
Interference microscopes are commonly used to measure the surface shape and roughness of continuous and discontinuous surfaces [1]. A polarization masked camera has been developed to achieve a snapshot phase shift measurement in both interferometry [9, 16] and interference microscopy [17], but multi-wavelength measurement can only be achieved sequentially due to the lack of a color sensitive polarization camera. We propose a snapshot multi-wavelength interference microscope to achieve high-speed measurement of large vertical range discontinuous structure and surface roughness, using a custom CMOS camera with linear micro-polarizer array and Bayer filters [18]. Phase-shifted interferograms of different color channels are captured in a single shot This system has the advantages of high speed and large vertical measurement range, suitable for high dynamic measurement environment. Our system can measure the surface roughness in a single shot
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