Research

Soft x-ray microscopy allows researchers to bridge the gap between the high resolution, low sample fidelity realm of electron microscopy and the low resolution, high sample fidelity realm of visible light microscopy[i],[ii].  While a biologist can view a cell easily in a visible light microscope that same cell must be stained, dried or frozen, and thinly sliced to be observed in an electron microscope.  A microscope using 0.2 to 1 keV x-rays is able to image unfixed, whole cells in an aqueous environment.  While the idea of an x-ray microscope dates to the early part of the 21^st century it has only been in the last 25 years that practical soft x-ray microscopes have been built and only in the last decade have they become useful workhorses for researchers[iii].  The desire now is to develop methods to obtain 3D images using soft x-ray microscopes.  One promising technique is to record a tilt series of x-ray holograms[iv] of a specimen in a method known as diffraction tomography[v].  This method has been nicely demonstrated in optical experiments[vi],[vii] but significant technical and conceptual problems need to be addressed in order to use x-rays.

Recently groups at LLNL and SUNY Stony Brook have pushed this idea even further to eliminate the need for lenses.  The basic idea was first proposed by David Sayre quite a while back.  The basic idea is to collect a diffraction pattern from a non-periodic object (like a cell).  Now all you have to do is figure out how to back propagate your wave-field to reconstruct your object.  This is not an easy problem.  With multiple views this problem becomes slightly easier since the signal from the object reinforces. 

[Note: I plan to update this section with more references.]