Reduced-phase dual-illumination interferometer for measuring large stepped objects

Behnam Tayebi, Mohammad Reza Jafarfard, Farnaz Sharif, Yoon Sung Bae, Seyyed Hossein Hosseini Shokuh, Dug Young Kim

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


We present a reduced-phase dual-illumination interferometer (RPDII) that measures the topography of a sample with large step height variation. We experimentally demonstrate the basic principle and the feasibility of this novel single-shot quantitative phase imaging. Two beams of this interferometer illuminate a sample at different incident angles, and two phases of the different incident angles and their phase difference are simultaneously recorded using three spatial frequencies. The relative phase difference between two beams of an RPDII can be controlled by adjusting the angle such that the maximum phase difference is smaller than 2π, and thus there is no phase wrapping ambiguity in the reconstructed phase. One 4f optical system with a transmission grating is used to illuminate the sample with two collimated beams incident at different angles. The feasibility of this technique is demonstrated by measuring the thicknesses of two stepped metal layers with heights of 150 and 660 μm. Although the change in stepped height is more than 1000 times the wavelength of the laser used in our interferometer, the thicknesses of these two metal layers are successfully obtained without the use of an unwrapping algorithm.

Original languageEnglish
Pages (from-to)5740-5743
Number of pages4
JournalOptics Letters
Issue number19
Publication statusPublished - 2014 Oct 1

Bibliographical note

Publisher Copyright:
© 2014 Optical Society of America.

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics


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