Computational illumination for high-speed in vitro Fourier ptychographic microscopy

We demonstrate a new computational illumination technique that achieves large space-bandwidth-time product, for quantitative phase imaging of unstained live samples in vitro. Microscope lenses can have either large field of view (FOV) or high resolution, not both. Fourier ptychographic microscopy (FPM) is a new computational imaging technique that circumvents this limit by fusing information from multiple images taken with different illumination angles. The result is a gigapixel-scale image having both wide FOV and high resolution, i.e. large space-bandwidth product (SBP). FPM has enormous potential for revolutionizing microscopy and has already found application in digital pathology. However, it suffers from long acquisition times (on the order of minutes), limiting throughput. Faster capture times would not only improve imaging speed, but also allow studies of live samples, where motion artifacts degrade results. In contrast to fixed (e.g. pathology) slides, live samples are continuously evolving at various spatial and temporal scales. Here, we present a new source coding scheme, along with real-time hardware control, to achieve 0.8 NA resolution across a 4x FOV with sub-second capture times. We propose an improved algorithm and new initialization scheme, which allow robust phase reconstruction over long time-lapse experiments. We present the first FPM results for both growing and confluent in vitro cell cultures, capturing videos of subcellular dynamical phenomena in popular cell lines undergoing division and migration. Our method opens up FPM to applications with live samples, for observing rare events in both space and time

KINEMATICAL RESEARCH ON HURDLE CLEARANCE TECHNIQUES OF ELITE CHINESE ATHLETE IN 100M HURDLES

INTRODUCTION: Although Jing Liu was the champion of women’s 100m Hurdle in 2007 Asian Games, the performance did not get the level of the world elite athletes. This investigation was conducted to find the technique defects and thus to serve athletic training through kinematical analysis to hurdle clearance techniques of Jing Liu

Phase imaging based on wavefront propagation

Light is a wave which has both amplitude and phase. Since the vibration of the wave is too fast, phase needs to be recovered from the time–averaged energy—intensity by computational methods. In this thesis, we choose defocus as a way to mix phase into measured intensity images, because it is not only efficient in transferring phase to intensity but also advantageous due to its simplicity and flexibility in the experiment. In this thesis, we develop computational methods to recover phase from defocused intensity images which contain phase information. We first propose methods based on complex Kalman filtering, which updates the complex field from the noisy intensity images by maintaining pair–wise pixel error correlation. We prove that the pixel–wise correlation is sparse and it reduces computational complexity of the method from cubic to linear of the total number of the pixel numbers. Secondly, we introduce an exponential spacing measurement scheme to efficiently re-duce the number of defocused intensity images. We perform Gaussian process regres-sion over the exponentially spaced intensity images to estimate the axial derivative in the transport of intensity equation (TIE) phase retrieval. It alleviates the nonlinear-ity error in the derivative estimation by using the prior knowledge of how intensity varies with defocus propagation in the spatial frequency domain. Finally, we also consider the phase recovery of partially coherent illumination created by any arbitrary source shape in K¨ohler geometry. By extending the Kalman filtering algorithms to the partially coherent case, we recover not only the phase but also an estimate of the unknown illumination source shape. In conclusion, we consider the issues of noise, intensity measurement scheme, nonlinearity error in TIE and partially coherent illumination. We validate our techniques experimentally with a brightfield microscope. Since the measurement of defocused in-tensity images is experimentally simple and flexible, the methods in this thesis should find use in optical, X–ray and other phase imaging systems.DOCTOR OF PHILOSOPHY (EEE

Partially coherent phase imaging with simultaneous source recovery.

We propose a new method for phase retrieval that uses partially coherent illumination created by any arbitrary source shape in Köhler geometry. Using a stack of defocused intensity images, we recover not only the phase and amplitude of the sample, but also an estimate of the unknown source shape, which describes the spatial coherence of the illumination. Our algorithm uses a Kalman filtering approach which is fast, accurate and robust to noise. The method is experimentally simple and flexible, so should find use in optical, electron, X-ray and other phase imaging systems which employ partially coherent light. We provide an experimental demonstration in an optical microscope with various condenser apertures

Partially coherent phase imaging with simultaneous source recovery.

We propose a new method for phase retrieval that uses partially coherent illumination created by any arbitrary source shape in Köhler geometry. Using a stack of defocused intensity images, we recover not only the phase and amplitude of the sample, but also an estimate of the unknown source shape, which describes the spatial coherence of the illumination. Our algorithm uses a Kalman filtering approach which is fast, accurate and robust to noise. The method is experimentally simple and flexible, so should find use in optical, electron, X-ray and other phase imaging systems which employ partially coherent light. We provide an experimental demonstration in an optical microscope with various condenser apertures