SOFT-X-RAY MICROSCOPE USING FOURIER-TRANSFORM HOLOGRAPHY

A Fourier transform holographic microscope with an anticipated resolution of better than 100 nm has been built. Extensive testing of the apparatus has begun. Preliminary results include the recording of interference fringes using 3.6-nm X-rays. The microscope employs a charge-coupled-device (CCD) detector array of 576 × 384 elements. The system is illuminated by soft X-rays from a high-brightness undulator. The reference point source is formed by a Fresnel zone plate with a finest outer zone width of 50 nm. Sufficient temporal coherence for hologram formation is obtained by a spherical grating monochromator. The X-ray hologram intensities at the recording plane are to be collected, digitized and reconstructed by computer. Data acquisition is under CAMAC control, while image display and off-line processing takes place on a VAX graphics workstation. Computational models of Fourier transform hologram synthesis, and reconstruction in the presence of noise, have demonstrated that numerical methods in two dimensions are feasible and that three-dimensional information is potentially recoverable. © 1990.