Research

A microscope using Zernike’s phase contrast method and a hard x-ray Gabor hologram

¹ Theranostic Device Research Group, Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, 305-8564, Tsukuba, Ibaraki, Japan
² The graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsu, 431-1202, Nishi-ku, Hamamatsu, Shizuoka, Japan
³ Instituto Nacional de Astrofísica,, Óptica y Electrónica, Luis Enrique Erro #1, Tonantzintla, Puebla, Mexico
⁴ Research Institute for Measurement and Analytical Instrumentation, NMIJ, National Institute of Advance Industrial Science and Technology, 305-8568, Tsukuba, Ibaraki, Japan
⁵ Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, 679-5198, Hyogo, Japan
⁶ Singapore-MIT Alliance for Research and Technology (SMART) Centre1 CREATE Way #09-03, CREATE Tower, 138602, Singapore, Singapore
⁷ Faculty of Technology, University of Oulu, PO Box 7300, 9014, Oulu, Finland

^c m.misawa@aist.go.jp

Received: 25 August 2016
Accepted: 7 November 2016

Abstract

Background: In hard X-ray phase imaging using interferometry, the spatial resolution is limited by the pixel size of digital sensors, inhibiting its use in magnifying observation of a sample.

Methods: To solve this problem, we describe a digital phase contrast microscope that uses Zernike’s phase contrast method with a hard X-ray Gabor holography associated with numerical processing and spatial frequency domain filtering techniques. The hologram is reconstructed by a collimated beam in a computer. The hologram intensity distributions itself become the reconstructed wavefronts. For this transformation, the Rayleigh- Sommerfeld diffraction formula is used.

Results: The hard X-ray wavelength 0.1259 nm (an energy of 9.85 keV) was employed at the SPring-8 facility. We succeeded in obtaining high-resolution images by a CCD sensor with a pixel size of 3.14 μm, even while bound by the need to satisfy the sampling theorem and by the CCD pixel size. The test samples used here were polystyrene beads of 8 μm, and human HeLa cells.

Conclusions: We thus proved that the resolution 0.951 μm smaller than the pixel size of CCD (3.14 μm) was achieved by the proposed reconstruction techniques and coherent image processing in the computer, suggesting even higher resolutions by adopting greater numerical apertures.