Digital micromirror device-based laser-illumination Fourier ptychographic microscopy

Abstract

Abstract:We report a novel approach to Fourier ptychographic microscopy (FPM) by using a digital micromirror device (DMD) and a coherent laser source (532 nm) for generating spatially modulated sample illumination. Previously demonstrated FPM systems are all based on partially-coherent illumination, which offers limited throughput due to insufficient brightness. Our FPM employs a high power coherent laser source to enable shot-noise limited high-speed imaging. For the first time, a digital micromirror device (DMD), imaged onto the back focal plane of the illumination objective, is used to generate spatially modulated sample illumination field for ptychography. By coding the on/off states of the micromirrors, the illumination plane wave angle can be varied at speeds more than 4 kHz. A set of intensity images, resulting from different oblique illuminations, are used to numerically reconstruct one high-resolution image without obvious laser speckle. Experiments were conducted using a USAF resolution target and a fiber sample, demonstrating high-resolution imaging capability of our system. We envision that our approach, if combined with a coded-aperture compressive-sensing algorithm, will further improve the imaging speed in DMD-based FPM systems.

Rapid in‐focus corrections on quantitative amplitude and phase imaging using transport of intensity equation method

“…In order to realize high-contrast and quantitative label-free cellular observation, phase imaging focusing on sample phase retrieval is proposed (Mir et al, 2012). Classical approaches as Gerchberg-Saxton algorithm (Gerchberg & Saxton, 1971) and Ptychographic methods including ptychographic iterative engine (Rodenburg & Faulkner, 2004;Rodenburg et al, 2007;Yu et al, 2016a,b>) and Fourier ptychographic microscopy (Horstmeyer et al, 2012;Horstmeyer & Yang, 2014;Kuang et al, 2015;Tian et al, 2015;Yeh et al, 2015;Zheng et al, 2013;Zhang et al, 2015a,b) acquire quantitative phase distributions from diffraction via iterative numerical wavefront propagations. Their lens-free systems are simple especially suiting for short-wavelength imaging.…”

Ultra-high speed digital micro-mirror device based ptychographic iterative engine method

“…DMD has been used in other imaging techniques including the tomographic phase microscopy and Fourier ptychographic microscopy to realize the phase measurement, where it was adopted mainly to avoid the rotating of the sample or to reduce the position-error of the light source by forming multidirectional illumination on the sample [34,35]. Quite different from these two existing techniques, our proposed method uses the on/off switching of the micro-mirrors of DMD to replace the mechanical scanning of the sample in common PIE.…”

Wide-field Fourier ptychographic microscopy using laser illumination source

“…Ref. [29] demonstrated for the first time using a high-power laser beam coupled with a DMD which allowed for shot-noise-limited image capturing process, overcoming the power limitation of LEDs. All these methods address the slow capture issue, but they are not without downsides.…”

“…In Ref. [29], although the power of illumination is easily scalable by using a stronger laser, the on-state mirrors only constitute a small portion of the entire DMD area. Given n desired illumination angles, only 1/n of the DMD-incident collimated laser beam is utilized per illumination angle.…”

“…[29] or a set of microlens arrays as suggested by Ref. [31] to guide the illumination beam is that the illuminating wavefront does not suffer from additional aberrations induced by the additional lenses needed for f-theta scanning.…”