Contrast enhancement and three-dimensional computed tomography in projection X-ray microscopy

We have developed a projection X-ray microscope by modifying a scanning electron microscope (SEM), thus simplifying optical alignment and focusing process. When the object was much larger than the resolution of this microscope (0.1 mum), the edge of the image was enhanced due to Fresnel diffraction of partially coherent light. Thus the projection images such as thin filaments in biological objects showed enough contrast even their absorption contrast was very low. Because there are no optical elements for X-ray (e.g. zone plate), this microscope has long focal depth. This means we can obtain the projection image of thick sample at one time without preparing thin sections of the sample. Taking this advantage we have applied this microscope for three-dimensional structure analysis by means of computed tomography.