Video-rate quantitative phase imaging with dynamic acousto-optic defocusing

Various quantitative phase imaging techniques exist capable of characterizing transparent and low-contrast sam-ples without the addition of dyes or fluorescent probes. Among them, the transport of intensity equation (TIE) allows phase retrieval by capturing information from different focal planes without complex inteferometric setups. However, current implementations can be limited in speed or accuracy by the lack of optical systems suitable for fast, reliable, and customizable focal plane selection. Here, we report how combining acousto-optics with pulsed illumination enables accurate and on-demand electronic defocus control suitable for TIE phase imaging at speeds only limited by the camera frame rate. The system exhibits diffraction-limited spatial resolution and high reconstruction fidelity, undistinguishable from traditional mechanical defocusing. We demonstrate its feasibility by measuring different dynamic events at rates as high as 100 phase maps per second. The tunability and ease of implementation of our system can pave the way to democratizing quantitative phase imaging in histopathology, fluid dynamics, and other fields involving thin transparent samples.

Automated summary

Various quantitative phase imaging techniques are capable of characterizing transparent and low-contrast samples without the need for dyes or probes. However, current implementations can be limited by the lack of suitable optical systems for fast and customizable focal plane selection. In this study, we combine acousto-optics with pulsed illumination to enable accurate and on-demand electronic defocus control for phase imaging, achieving diffraction-limited spatial resolution and high reconstruction fidelity. The system demonstrates feasibility by measuring dynamic events at rates as high as 100 phase maps per second, paving the way for quantitative phase imaging in various fields.