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.