Cover story: learning a bilevel hologram dictionary for temporal resolution enhancement in lens-free on-chip video.


"Dictionary-based phase retrieval for space-time super resolution using lens-free on-chip holographic video"
Zihao Wang, Qiqin Dai, Donghun Ryu, Kuan He, Roarke Horstmeyer, Aggelos Katsaggelos, Oliver S Cossairt
OSA Imaging and Applied Congress, Computational Optical Sensing and Imaging (COSI), June 2017

"4D Tracking of Biological Samples using Lens-free On-chip In-line Holography"
Zihao Wang, Donghun Ryu, Kuan He, Oliver Cossairt, Aggelos K Katsaggelos
OSA Digital Holography and Three-Dimensional Imaging, May 2017


Setup and phase retrieval

The left panel of this image presents our lens-free on-chip imaging setup. On the right, 5 types of protozoa along with the phase retrieval results are presented.

Phase retrieval algorithm

Our "shrink-wrap" phase retrieval algorithm can iteratively recover phase information by gradually estimating the "support" (shape) of the object.

Training a bilevel holographic dictionary

By training a bilevel holographic dictionary, we are capable of recovering high resolution holograms from subsampled holograms. Results show that our subsampled holograms allow imaging at an enhanced frame rate.

Testing results

Our testing results show an improved performance over bicubic interpolation.


Digital refocusing from a holographic snapshot of Paramecium.

By applying the aforementioned phase retrieval method, we are capable of recovering the phase information from the hologram captures.


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