Single-shot lensless masked imaging with enhanced self-calibrated phase retrieval.

Single-shot lensless imaging with a binary amplitude mask enables a low-cost and miniaturized configuration for wave field recovery. However, the mask only allows a part of the wave field to be captured, and thus the inverse decoding process becomes a highly ill-posed problem. Here we propose an enhanced self-calibrated phase retrieval (eSCPR) method to realize single-shot joint recovery of mask distribution and the sample's wavefront. In our method, a sparse regularized phase retrieval (SrPR) algorithm is designed to calibrate the mask distribution. Then, a denoising regularized phase retrieval (DrPR) algorithm is constructed to reconstruct the wavefront of the sample. Compared to conventional single-shot methods, our method shows robust and flexible image recovery. Experimental results of different samples are given to demonstrate the superiority of our method.

Fourier ptychographic microscopy with adaptive resolution strategy.

Fourier ptychographic microscopy (FPM) is a method capable of reconstructing a high-resolution, wide field-of-view (FOV) image, where dark-field images provide the high-frequency information required for the iterative process. Theoretically, using more dark-field images can lead to results with higher resolution. However, the resolution required to clearly detect samples with different microscales varies. For certain samples, the limit resolution of the imaging system may exceed the one required to resolve the details. This suggests that simply increasing the number of dark-field images will not improve the recognition capability for such samples and may instead significantly increase the computational cost. To address this issue, this Letter proposes an adaptive resolution strategy that automatically assigns the resolution required for the sample. Based on a Tenengrad approach, this strategy determines the number of images required for reconstruction by evaluating a series of differential images among the reconstructions for a certain subregion and then efficiently completes the full-FOV reconstruction according to the determined resolution. We conducted the full-FOV reconstruction utilizing feature-domain FPM for both the USAF resolution test chart and a human red blood cell sample. Employing the adaptive resolution strategy, the preservation of reconstruction resolution can be ensured while respectively economizing approximately 76% and 89% of the time.

Fourier Ptychographic Microscopy 10 Years on: A Review.

Fourier ptychographic microscopy (FPM) emerged as a prominent imaging technique in 2013, attracting significant interest due to its remarkable features such as precise phase retrieval, expansive field of view (FOV), and superior resolution. Over the past decade, FPM has become an essential tool in microscopy, with applications in metrology, scientific research, biomedicine, and inspection. This achievement arises from its ability to effectively address the persistent challenge of achieving a trade-off between FOV and resolution in imaging systems. It has a wide range of applications, including label-free imaging, drug screening, and digital pathology. In this comprehensive review, we present a concise overview of the fundamental principles of FPM and compare it with similar imaging techniques. In addition, we present a study on achieving colorization of restored photographs and enhancing the speed of FPM. Subsequently, we showcase several FPM applications utilizing the previously described technologies, with a specific focus on digital pathology, drug screening, and three-dimensional imaging. We thoroughly examine the benefits and challenges associated with integrating deep learning and FPM. To summarize, we express our own viewpoints on the technological progress of FPM and explore prospective avenues for its future developments.