In light-field microscopy, a single point emitter gives rise to a complex diffraction pattern, which varies with the position of the emitter in object space. In order to use deconvolution-based wave-optical reconstruction schemes for light-field imaging systems, established methods rely on theoretical estimation of such diffraction patterns. In this paper we propose a novel method for direct experimental estimation of the light-field point spread function. Our approach relies on a modified reversed micro-Hartmann test to acquire a composite light-field point spread function of several thousand point emitters in the object plane simultaneously. By using fiducial markers and a custom image processing algorithm we separate the contributions of individual point emitters directly in raw light-field images and allow the construction of the forward imaging process without any prior assumption about the optical system required. The constructed forward imaging model can finally be applied in the 3D-deconvolution based wave-optical reconstruction scheme.
In addition to the two-dimensional intensity distribution in the image plane, light field microscopes capture information about the angle of the incident radiation. This information can be used to extract depth information about the object, calculate all-in-focus images and perform three-dimensional reconstructions from a single exposure. In combination with automated microscopy setups, this makes the technique a promising tool for high-throughput, three-dimensional cell assay evaluation which could substantially improve drug development and screening. To this end, we have developed a novel generalized calibration and three-dimensional reconstruction scheme for a lightfield fluorescence microscope setup. The scheme can handle Keplerian and Galilean light field camera configurations added to infinity corrected microscopes configured to be telecentric as well as non-telecentric or hypercentric. The latter provides a significant advantage over the state of the art as it allows for an application specific optimization of lateral and axial resolution, field-of-view, and depth-of-focus. The reconstruction itself is performed iteratively using an expectation maximization algorithm. Super-resolved reconstructions can be achieved by including experimentally measured pointspread- functions. To reduce the required computational power, sparsity and periodicity of the system matrix relating object space to light field space is exploited. This is particularly challenging for the non-telecentric cases, where the voxel size of the reconstructed object space depends on the axial coordinate. We provide details on the experimental setup and the reconstruction algorithm, and present results on the experimental verification of theoretical performance parameters as well as successful reconstructions of fluorescent beads and three-dimensional cell spheroids.
In this work, we provide an initial characterization of a novel twin robotic X-ray system. This system is equipped
with two motor-driven telescopic arms carrying X-ray tube and flat-panel detector, respectively. 2D radiographs
and fluoroscopic image sequences can be obtained from different viewing angles. Projection data for 3D cone-beam
CT reconstruction can be acquired during simultaneous movement of the arms along dedicated scanning
trajectories. We provide an initial evaluation of the 3D image quality based on phantom scans and clinical
images. Furthermore, initial evaluation of patient dose is conducted. The results show that the system delivers
high image quality for a range of medical applications. In particular, high spatial resolution enables adequate
visualization of bone structures. This system allows 3D X-ray scanning of patients in standing and weight-bearing
position. It could enable new 2D/3D imaging workflows in musculoskeletal imaging and improve diagnosis of
Profiling structured beams produced by X-ray free-electron lasers (FELs) is crucial to both maximizing signal intensity for weakly scattering targets and interpreting their scattering patterns. Earlier ablative imprint studies describe how to infer the X-ray beam profile from the damage that an attenuated beam inflicts on a substrate. However, the beams in-situ profile is not directly accessible with imprint studies because the damage profile could be different from the actual beam profile. On the other hand, although a Shack-Hartmann sensor is capable of in-situ profiling, its lenses may be quickly damaged at the intense focus of hard X-ray FEL beams. We describe a new approach that probes the in-situ morphology of the intense FEL focus. By studying the translations in diffraction patterns from an ensemble of randomly injected sub-micron latex spheres, we were able to determine the non-Gaussian nature of the intense FEL beam at the Linac Coherent Light Source (SLAC National Laboratory) near the FEL focus. We discuss an experimental application of such a beam-profiling technique, and the limitations we need to overcome before it can be widely applied.
Results of coherent diffractive imaging experiments performed with soft X-rays (1-2 keV) at the Linac Coherent
Light Source are presented. Both organic and inorganic nano-sized objects were injected into the XFEL beam
as an aerosol focused with an aerodynamic lens. The high intensity and femtosecond duration of X-ray pulses
produced by the Linac Coherent Light Source allow structural information to be recorded by X-ray diffraction
before the particle is destroyed. Images were formed by using iterative methods to phase single shot diffraction
patterns. Strategies for improving the reconstruction methods have been developed. This technique opens
up exciting opportunities for biological imaging, allowing structure determination without freezing, staining or