High spatial and temporal resolution synthetic aperture phase microscopy

Cheng Zheng,Yanping He,Renjie Zhou,Peter T C So,Juejun Hu,Hongtao Lin,Di Jin,Zahid Yaqoob

doi:10.1117/1.ap.2.6.065002

Abstract

A new optical microscopy technique, termed high spatial and temporal resolution synthetic aperture phase microscopy (HISTR-SAPM), is proposed to improve the lateral resolution of wide-field coherent imaging. Under plane wave illumination, the resolution is increased by twofold to around 260 nm, while achieving millisecond-level temporal resolution. In HISTR-SAPM, digital micromirror devices are used to actively change the sample illumination beam angle at high speed with high stability. An off-axis interferometer is used to measure the sample scattered complex fields, which are then processed to reconstruct high-resolution phase images. Using HISTR-SAPM, we are able to map the height profiles of subwavelength photonic structures and resolve the period structures that have 198 nm linewidth and 132 nm gap (i.e., a full pitch of 330 nm). As the reconstruction averages out laser speckle noise while maintaining high temporal resolution, HISTR-SAPM further enables imaging and quantification of nanoscale dynamics of live cells, such as red blood cell membrane fluctuations and subcellular structure dynamics within nucleated cells. We envision that HISTR-SAPM will broadly benefit research in material science and biology.

Highlights

High-speed and high-resolution imaging techniques have been long sought for material metrology and biological structure observation
Such examples include the inspection of large area subwavelength structures and optical metasurfaces widely used in integrated photonics,[1,2] monitoring fast semiconductor wet etching process,[3] microdroplet evaporation dynamics,[4] observation of live cell morphology, fast dynamics in a large cell population,[5,6] and tracking of high-speed cell motions.[7,8]
We note that (i) our phase imaging quality is not affected by laser speckle (Fig. S2 in the Supplemental Materials), and, (ii) as our spectrum synthesis process does not require much overlapping, we can significantly reduce the number of illumination angles without compromising image quality to achieve even higher imaging speed (Fig. S3 in the Supplemental Materials)

Summary

Introduction

High-speed and high-resolution imaging techniques have been long sought for material metrology and biological structure observation. Fluorescence-based imaging techniques are usually slow, limiting their use in high-speed imaging applications. QPM has been increasingly applied to semiconductor wafer defects detection, semiconductors etching monitoring in material science,[10,11] and cell growth, mechanics, and metabolism modeling in biological imaging.[12,13] the lateral resolution of plane wave illumination coherent imaging techniques is limited to λ∕NA by diffraction. There is a great need to improve the imaging resolution and speed to meet emerging application demands in material science and biology, including but not limited to profiling large area subwavelength structures and quantifying fast subcellular dynamics

Methods

Results

Conclusion