THREE DIMENSIONAL IMAGING IN SCANNING SOFT X-RAY MICROSCOPY.

In 3-D image reconstruction, a complete set of 2-D image projections is required to give a unique and unambiguous object reconstruction. In practice, particularly for a scanning X-ray microscope, the tilting angle of the object is geometrically restricted and the reconstruction from an incomplete projection set will be spatially distorted. One way to improve this is to use a priori information. For a scanning X-ray microscope, a fan beam illumination and a linear array detector will be adequate to provide a set of 2-D projections. An alternative, which may place less stringent requirements on the scanning and tilting mechanism, is to use cone beam illumination and a 2-D array detector. The differences in image reconstruction using these two systems can be investigated using a geometrically scaled optical analogue.