Jingshan Zhong

Projects

Jingshan Zhong
Title:

Associate research scientist

Office Address

Shenzhen institute of artificial intelligence and robotics for society, Shenzhen, Guangdong, China

Teaching Area

computational imaging, optics, optimization

Research

computational imaging, phase imaging, optimizaiton, machine learning,

phase recovery from through focus intensity images

In traditional microscopy, phase imaging could be implemented with specific hardware designs, for example phase contrast microscopy, and differential interference contrast microscopy. In this project, phase is computationally reconstructed from a series of through focus intensity images. It has advantages of simple experiment setup and provides quantitative phase. The information of phase is nonlinearly transferred into intensity measurements by defocusing. We have developed multiple techniques to solve the issues in the inverse problem.


 

(1) Instead of equally spaced defocusing distances, the through focus intensity images could be distanced exponentially. In this way, fewer intensity images are measured for phase recovery.

Z. Jingshan, R. A. Claus, J. Dauwels, L. Tian, and L. Waller, Transport of intensity phase imaging by intensity spectrum fitting of exponentially spaced defocus planes, Opt. Express 22, 10661-10674 (2014).

 

(2) Transport of intensity equation relates phase to the first derivative of intensity images with respect to the defocus (z axis). The intensity spectrum over z follows sinusoidal pattern variations. We use Gaussian process regression to fit the intensity spectrum and estimate the intensity derivative.

Z. Jingshan, R. A. Claus, J. Dauwels, L. Tian, and L. Waller, Transport of intensity phase imaging by intensity spectrum fitting of exponentially spaced defocus planes, Opt. Express 22, 10661-10674 (2014).

 

(3) Optimization methods such as Kalman filtering and nonlinear optimization have been applied to solve the inverse problem of phase recovery. Kalman filtering models the noise in the intensity measurements and updates the phase recursively. Besides, we formulate the phase recovery as a least square error problem and solve the optimization with quasi-Newton methods.

Z. Jingshan, L. Tian, P. Varma and L. Waller, Partially coherent phase retrieval and arbitrary source shape estimation by nonlinear optimization, IEEE Trans. Comput. Imag 2(3), 310-322 (2016).

Z. Jingshan, J. Dauwels, M. A. Vázquez, and L. Waller, Sparse ACEKF for phase reconstruction, Opt. Express 21, 18125-18137 (2013).

 

(4) The effects of partially coherent illumination degrade the quality of recovered phase when a coherent model is used in the inverse problem. We solve the issue of model mismatch by considering the effects of partially coherent illumination.

Z. Jingshan, L. Tian, P. Varma and L. Waller, Partially coherent phase retrieval and arbitrary source shape estimation by nonlinear optimization, IEEE Trans. Comput. Imag 2(3), 310-322 (2016).

Z. Jingshan, L. Tian, J. Dauwels, and L. Waller, Partially coherent phase imaging with simultaneous source recovery, Bio. Opt. Express 6, 257-265 (2015).



phase space/light field imaging

For quasi-monochromatic light, a 4D function such as optical phase-space function is required to describe the optical properties of a 2D space. It records the outcome of light interaction with 3D scene. We work on several 3D imaging projects under the framework of phase-space optics.

 

In the experiment, we add an SLMspatial light modulatorin the Fourier space of a 4f system, and measure intensity images by applying coded aperture patterns on the SLM. The forward model and the data acquisition scheme is derived under phase-space optics. A large-volume high-resolution 3D fluorescent object is reconstructed from the multiplexed phase-space measurements by optimization algorithms. We also apply the phase-space imaging on 3D localization of point sources through scattering.




H. Liu, Z. Jingshan, and L. Waller, Multiplexed phase-space imaging for 3D fluorescence microscopy, Opt. Express 23, 33214-33240 (2017).

H. Liu, E. Jonas, L. Tian, Z. Jingshan, B. Recht and L. Waller, 3D imaging in volumetric scattering media using phase-space measurements, Opt. Express 23, 14461-14471 (2015).