Jiamin Wu

Spatial-spectral encoded compressive hyperspectral imaging

This paper proposes a novel compressive hyperspectral (HS) imaging approach that allows for high-resolution HS images to be captured in a single image. The proposed architecture comprises three key components: spatial-spectral encoded optical camera design, over-complete HS dictionary learning and sparse-constraint computational reconstruction. Our spatial-spectral encoded sampling scheme provides a higher degree of randomness in the measured projections than previous compressive HS imaging approaches; and a robust nonlinear sparse reconstruction method is employed to recover the HS images from the coded projection with higher performance. To exploit the sparsity constraint on the nature HS images for computational reconstruction, an over-complete HS dictionary is learned to represent the HS images in a sparser way than previous representations. We validate the proposed approach on both synthetic and real captured data, and show successful recovery of HS images for both indoor and outdoor scenes. In addition, we demonstrate other applications for the over-complete HS dictionary and sparse coding techniques, including 3D HS images compression and denoising.

Camera array based light field microscopy.

This paper proposes a novel approach for high-resolution light field microscopy imaging by using a camera array. In this approach, we apply a two-stage relay system for expanding the aperture plane of the microscope into the size of an imaging lens array, and utilize a sensor array for acquiring different sub-apertures images formed by corresponding imaging lenses. By combining the rectified and synchronized images from 5 × 5 viewpoints with our prototype system, we successfully recovered color light field videos for various fast-moving microscopic specimens with a spatial resolution of 0.79 megapixels at 30 frames per second, corresponding to an unprecedented data throughput of 562.5 MB/s for light field microscopy. We also demonstrated the use of the reported platform for different applications, including post-capture refocusing, phase reconstruction, 3D imaging, and optical metrology.

Snapshot Hyperspectral Volumetric Microscopy.

The comprehensive analysis of biological specimens brings about the demand for capturing the spatial, temporal and spectral dimensions of visual information together. However, such high-dimensional video acquisition faces major challenges in developing large data throughput and effective multiplexing techniques. Here, we report the snapshot hyperspectral volumetric microscopy that computationally reconstructs hyperspectral profiles for high-resolution volumes of ~1000 μm × 1000 μm × 500 μm at video rate by a novel four-dimensional (4D) deconvolution algorithm. We validated the proposed approach with both numerical simulations for quantitative evaluation and various real experimental results on the prototype system. Different applications such as biological component analysis in bright field and spectral unmixing of multiple fluorescence are demonstrated. The experiments on moving fluorescent beads and GFP labelled drosophila larvae indicate the great potential of our method for observing multiple fluorescent markers in dynamic specimens.

Camera array based light field microscopy

We present a camera array based light field microscopy that utilizes a camera array to simultaneously capture the different perspectives formed by a two-stage relay system. The proposed method achieves high-resolution light field acquisition with high accuracy and facilitates various applications.

Coded aperture pair for quantitative phase imaging

This Letter proposes a novel quantitative phase-imaging approach by optically encoding light fields into a complementary image pair followed by computational reconstruction. We demonstrate that the axial intensity derivative for phase recovery can be well estimated by a coded-aperture image pair without z axial scanning. The experimental results demonstrate that our approach can achieve higher accuracy and robustness compared with conventional transport-of-intensity equation (TIE) based approaches under partial coherence illumination.

Fourier ptychographic microscopy using wavelength multiplexing

Abstract. Fourier ptychographic microscopy (FPM) is a recently developed technique stitching low-resolution images in Fourier domain to realize wide-field high-resolution imaging. However, the time-consuming process of image acquisition greatly narrows its applications in dynamic imaging. We report a wavelength multiplexing strategy to speed up the acquisition process of FPM several folds. A proof-of-concept system is built to verify its feasibility. Distinguished from many current multiplexing methods in Fourier domain, we explore the potential of high-speed FPM in spectral domain. Compatible with most existing FPM methods, our strategy provides an approach to high-speed gigapixel microscopy. Several experimental results are also presented to validate the strategy.

Emerging theories and technologies on computational imaging

Computational imaging describes the whole imaging process from the perspective of light transport and information transmission, features traditional optical computing capabilities, and assists in breaking through the limitations of visual information recording. Progress in computational imaging promotes the development of diverse basic and applied disciplines. In this review, we provide an overview of the fundamental principles and methods in computational imaging, the history of this field, and the important roles that it plays in the development of science. We review the most recent and promising advances in computational imaging, from the perspective of different dimensions of visual signals, including spatial dimension, temporal dimension, angular dimension, spectral dimension, and phase. We also discuss some topics worth studying for future developments in computational imaging.

Wavelength Multiplexed Fourier Ptychograhic Microscopy

The time-consuming acquisition process of Fourier Ptychographic Microscopy (FPM) greatly limits its application in biological imaging. We report a novel wavelength multiplexed FPM (WMFPM) strategy, compatible with most existing methods, to further speed up the acquisition process.