A Drop-in, Focus-Extending Phase Mask Simplifies Microscopic and Microfluidic Imaging Systems for Cost-Effective Point-of-Care Diagnostics

Abstract

Microscopic imaging and imaging flow cytometry have wide potential in point-of-care assays; however, their narrow depth of focus necessitates precise mechanical or fluidic focus control of a sample in order to acquire high-quality images that can be used for downstream analysis, increasing the cost and complexity of the imaging system. This complexity represents a barrier to miniaturization and translation of point-of-care assays based on microscopic imaging or imaging flow cytometry. To address this challenge, we present a simple drop-in phase mask with a physics-informed, circularly symmetric asphere phase profile that extends the depth of focus by >5-fold while largely preserving the image quality compared to other depth extending methods. We show that such a focus-extended system overcomes manufacturing tolerances in low-cost sample chambers, enlarges the useable field-of-view of low-cost objectives, and permits increased throughput and precision in flow imaging systems without the need for complex flow-focusing. As the image quality is preserved without the need for postacquisition image restoration, our solution is also highly appropriate for on-line applications such as cell sorting.

Advances in Microfluidics: Technical Innovations and Applications in Diagnostics and Therapeutics

“…The high-speed images are processed and analyzed to extract information about cell size and deformability. Meng et al introduced a focus-extending phase mask that can extend the depth of focus by at least 5-fold for high-quality image acquisition in microfluidic imaging systems . The phase mask eliminates the need for frequent refocusing between samples, extends the field-of-view for low-cost objectives, and enables flow cytometry without flow focusing.…”

“…Meng et al introduced a focus-extending phase mask that can extend the depth of focus by at least 5-fold for high-quality image acquisition in microfluidic imaging systems. 85 The phase mask eliminates the need for frequent refocusing between samples, extends the field-of-view for lowcost objectives, and enables flow cytometry without flow focusing. Mandracchia et al reported optofluidic scanning microscopy for super-resolution, live cell imaging.…”

E2E-BPF microscope: extended depth-of-field microscopy using learning-based implementation of binary phase filter and image deconvolution

“…The DoF defines the depth range of an object that can be sharply imaged by a given optical imaging system, and is determined by the operating wavelength, effective focal length and aperture size of the imaging lens. In many biomedical imaging applications, such as in cytometry 1 , 2 , histology 3 , and endoscopy 4 – 6 , high-resolution imaging over a large spatial scale is often desired; for instance, a pathological examination is typically performed with a high numerical-aperture ( ) objective to visualize cellular and subcellular features of tissue specimens, but it is accompanied by limited field-of-view (FoV) and DoF. Therefore, to image large-area pathological/cytology slides, either objects or imaging optics should be scanned and refocused repetitively, which is costly and labor-intensive.…”