Optimization for complex optical system

Aberration retrieval and spatial coherence property measurement for imaging system

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Summary

In this research, we try to find the aberration of a complex optical system from only image measurements by solving optimization problems. Besides, we develop methods for measuring the the spatial coherence property of the light and for diffractive imaging.

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Research description

The image formed by an imaging system is often blurred by aberrations. We aim to retrieve the aberrations from only the blurred images using sophisticated computational methods, instead of using complicated setup such as interferometry or wavefront-sensor. In this project, we study the retrieval of shift-invariant aberrations from through-focus images of an extended object, and the retrieval of shift-variant aberrations of lithography system from the intensity measurements generated using a pair of matched periodic mask.

Spatial coherence is among the fundamental properties of light. It describes the statistical correlation between fields at a pair of locations. However, the measurement of spatial coherence is remarkably challenging, which limits the control and the optimization of spatial coherence in a broad range of key applications. In our research, we investigate the following problem: illuminating a complex-valued object by spatially partially coherent light , how do we reconstruct the transmission/reflection of the object and retrieve the mutual coherence function of the illumination from only the far-field diffraction pattern.

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