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Sparsity-Based Multi-Height Phase Recovery In Holographic Microscopy

Technology Benefits

Improves the throughput of imaging system without scarifying for the reconstructed image quality

Technology Application

Holographic microscopyOther coherent imaging systems that require multiple illumination angles or wavelengths to increase the throughput and speed of imaging

Detailed Technology Description

Knowing that images of most natural objects, such as biological specimen can be sparsely represented in some wavelet domain, researchers at UCLA have developed a novel sparsity-based phase reconstruction technique that takes advantage of a sparsity constraint in the wavelet domain, improving multi-height based phase retrieval, to significantly reduce the required number of holographic measurements while maintaining the quality of the reconstructed phase and amplitude images of the objects. When sparsity constraints are applied during the iterative reconstruction process, 2 in-line holograms with different sample-to-sensor distances are sufficient for image reconstruction, which provide image quality that is comparable to the ones that are constructed from >6-8 different measurements using conventional multi-height phase recovery methods.

Others

State Of Development

This method has been successfully tested by imaging clinically relevant dense samples, including highly connected pathology slides of Papanicolaou smears and breast tissue slides.

Background

Lensfree digital in-line holographic microscopy is a rapidly emerging computational imaging technique that allows highly compact and high-throughput microscope designs, and it is adopted by the on-chip holographic image acquisition platform to achieve a compact imaging setup. In-line holographic imaging measures the intensity of the interference pattern between the scattered object field and the un-scattered reference beam while these two beams are co-propagating in the same direction. Because the recorded hologram only contains the intensity information of the complex optical field, direct back-propagation of this in-line hologram to the object plane will generate a spatial artifact called twin image on top of the object’s original image.

The negative impact of this artifact on image quality is further amplified owing to the small sample-to-sensor distances that are used in on-chip implementations of digital in-line holographic microscopy, where the sample field-of-view is equal to the sensor active area. Although twin image artifact in digital in-line holography can be computationally eliminated by imposing physical constraints that the twin image does not satisfy, this approach works well with relatively isolated objects but is difficult to implement when dealing with dense and spatially connected samples, such as pathology slides and tissue samples.

Therefore, high-resolution imaging of densely connected samples using digital in-line holographic microscopy requires the acquisition of several holograms at different sample-to-sensor distances, or with different illumination angles and wavelengths in order to achieve robust phase recovery and coherent imaging of specimen. This not only increases the number of measurements, but also increases the data acquisition and processing time, limiting the throughput of the imaging system. Reducing the number of these holographic measurements tends to result in reconstruction artifacts and loss of image quality, which could be detrimental especially for biomedical and diagnostic-related applications.

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Tech ID/UC Case

28820/2017-173-0

Related Cases

2017-173-0

*Abstract

UCLA researchers in the Department of Electrical Engineering have developed a sparsity-based phase reconstruction technique implemented in wavelet domain to achieve more than 3-fold reduction in the number of holographic measurements for coherent imaging of densely connected samples with minimal impact on the reconstructed image quality.

*Principal Investigator

Name: Aydogan Ozcan

Department:

Name: Yair Rivenson

Department:

Name: Yichen Wu

Department:

Country/Region

USA