Anti-aliasing high resolution quantitative phase microscopy based on differential phase contrast imaging

Abstract

Differential phase contrast (DPC) imaging is a popular spatially partially coherent imaging method, which pro- vides high-quality, speckle-free 3D reconstructions with lateral resolution up to twice the coherent diffraction limit, under the precondition that the pixel size of the imaging sensor is small enough to prevent spatial alias- ing/undersampling. However, cameras are in general designed to have a large pixel size so that the intensity information transmitted by the optical system cannot be adequately sampled or digitized. On the other hand, using an image sensor with smaller pixel size or adding a magnification camera adapter to the camera can re- solve the undersampling at the expense of a reduced field of view (FOV). To solve this tradeoff, we introduce a new variation of quantitative DPC approach, termed anti-aliased DPC (AADPC), which uses several aliased intensity images under asymmetric illuminations to recover wide-field aliasing-free phase images. AADPC starts from an initial phase estimate obtained by a DPC-like deconvolution based on the systems weak phase transfer function. Then the obtained initial phase map is further refined by the iterative de-multiplexing algorithm to overcome pixel-aliasing and improve the imaging resolution. The data redundancy requirement as well as the optimal illumination scheme of AADPC are analyzed and discussed, suggesting the spatial undersampling can be mitigated through the iterative algorithm that uses only 4 images, yielding a nearly 4-fold increase in the space-bandwidth product (SBP) compared to conventional DPC approach.