Hard X-ray holographic microscopy using refractive prism and Fresnel zone plate objective

Imaging holography in hard x-ray region is realized by combining imaging microscopy with a refractive prism interferometer. The prism is placed behind the back-focal-plane of objective lens in order to configure a wavefront-division interferometer, and a magnified interferogram of object image is generated at an image plane. Spatial resolution of the image hologram is essentially determined by the performance of objective lens. However, speckle noise is a serious problem for fully coherent illumination. We have tried "asymmetric spatial coherence" to reduce the speckle noise. A synchrotron radiation light source with small coupling constant is very suitable for this purpose. The spatial coherence is sufficiently high in the vertical direction to make an interterogram, and low enough in the horizontal direction to suppress the speckle noise. Preliminary experiments at BL20XU of SPring-8 are shown.