[Paper Review] Single-shot deterministic complex amplitude imaging with a single-layer metalens

Liu Li, Shuai Wang+8 more|arXiv (Cornell University)|Sep 28, 2023

Optical measurement and interference techniques4 citations

TL;DR

This paper presents a single-shot, deterministic complex amplitude imaging system using a single-layer metalens that generates spatially multiplexed, polarization-phase-shifted point spread functions. By combining the metalens with a polarization camera, the system captures four interference patterns in one exposure, enabling full complex amplitude reconstruction of light fields without iterative algorithms or prior knowledge, demonstrated with incoherent LED illumination for static and dynamic objects with tailored magnification and field of view.

ABSTRACT

Conventional imaging systems can only capture light intensity. Meanwhile, the lost phase information may be critical for a variety of applications such as label-free microscopy and optical metrology. Existing phase retrieval techniques typically require a bulky setup, multi-frame measurements, or prior information of the target scene. Here, we proposed an extremely compact system for complex amplitude imaging, leveraging the extreme versatility of a single-layer metalens to generate spatially-multiplexed and polarization-phase-shifted point spread functions. Combining the metalens with a polarization camera, the system can simultaneously record four polarization shearing interference patterns along both in-plane directions, thus allowing the deterministic reconstruction of the complex amplitude light field in a single shot. Using an incoherent light-emitting diode as the illumination, we experimentally demonstrated speckle-noise-free complex amplitude imaging for both static and moving objects with tailored magnification ratio and field-of-view. The miniaturized and robust system may open the door for complex amplitude imaging in portable devices for point-of-care applications.

Motivation & Objective

• To overcome the limitation of conventional imaging systems that only capture intensity, losing critical phase information.
• To eliminate the need for multi-frame measurements, bulky setups, or prior scene knowledge in phase retrieval.
• To develop a miniaturized, robust, and deterministic complex amplitude imaging system suitable for portable applications.
• To leverage the wavefront engineering capabilities of a single-layer metalens for spatially multiplexed, polarization-encoded interference patterns.
• To enable speckle-noise-free imaging of both static and moving objects using incoherent illumination.

Proposed method

• A single-layer metalens is designed to produce four distinct, spatially multiplexed point spread functions with orthogonal polarization states and phase shifts.
• The metalens is combined with a polarization-sensitive camera to simultaneously record four interference patterns corresponding to in-plane shearing in two orthogonal directions.
• The recorded interference patterns encode both amplitude and phase information of the input light field through polarization-dependent phase shifts.
• A deterministic reconstruction algorithm is applied to the four recorded patterns to retrieve the complex amplitude field without iterative optimization or prior assumptions.
• The system uses incoherent light-emitting diodes as illumination, enabling speckle-free imaging for dynamic scenes.
• The magnification ratio and field of view are tunable through the design of the metalens and optical configuration.

Experimental results

Research questions

• RQ1 Can a single-layer metalens be engineered to generate multiple phase-shifted, polarization-multiplexed point spread functions for complex amplitude imaging?
• RQ2 Is it possible to achieve deterministic complex amplitude reconstruction from a single exposure using only a metalens and a polarization camera?
• RQ3 Can the system provide speckle-noise-free imaging of dynamic objects using incoherent illumination?
• RQ4 How does the system's performance compare to conventional multi-shot or iterative phase retrieval techniques in terms of compactness and robustness?
• RQ5 Can the system be miniaturized and adapted for point-of-care or portable optical diagnostics?

Key findings

• The system achieves single-shot, deterministic complex amplitude imaging without requiring iterative algorithms or prior knowledge of the object.
• Four polarization-shearing interference patterns are captured simultaneously using a single-layer metalens and a polarization camera, enabling full complex field reconstruction.
• The method enables speckle-noise-free imaging of both static and moving objects under incoherent LED illumination.
• The system demonstrates tailored magnification ratio and field of view through metalens design, offering flexibility for different imaging applications.
• The compact, robust, and single-shot nature of the system makes it suitable for integration into portable devices for point-of-care diagnostics.
• Experimental results confirm the feasibility and accuracy of the complex amplitude reconstruction across various test scenes.