International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 5. Hakodate 1998 
PHASE IMAGING WITH AN X-RAY SHEARING INTERFEROMETER 
Koichi IWATA, 
Professor, Department of Mechanical Engineering, 
College of Engineering, Osaka Prefecture University, 
1-1, Gakuen-cho, Sakai, Osaka, 599-8531 
E-mail: k-wata@measure.mecha.osakafu-u.ac.jp 
Hiroyuki TADANO, Hisao KIKUTA, 
College of Engineering, Osaka Prefecture University, 
Takashi NAKANO 
National Institute for Advanced Interdisciplinary Research, 
Hideki HAGINO 
Technology Research Institute of Osaka Prefecture, 
Yoshiaki KIMURA 
Konica Corporation 
JAPAN 
Commission V, Working Group 1 
KEY WORDS: X-ray, Shearing Interferometer, Phase, Refractive Index, Non-destructive Measurement 
ABSTRACT 
In this paper, we investigate a shearing type of X-ray interferometer, where two slightly sheared X-ray 
beams are produced and both of them are transmitted through the object. The two beams are superposed 
and interfered after they are transmitted through the interferometer. The interfered beams show intensity 
variation with high contrast due to the phase difference between them. Conventional X-ray sources can be 
used in this interferometer because the phase difference is small. Phase image is obtained by mechanical 
scanning or with an X-ray camera. Some simple objects of acrylic resin are measured with good contrast, 
showing the validity of the interferometer. Possibility of more efficient imaging schemes is discussed on the 
basis of the experimental results. 
1. INTRODUCTION 
In the conventional X-ray imaging such as computer 
tomography or radiography, we measure intensity of the 
X-rays which pass through the object to be measured. The 
intensity distribution reflects the distribution of absorption 
coefficient inside the object. However, absorption 
becomes low for materials of low atomic number and for 
hard X-rays. In such cases high contrast images are 
difficult to obtain (Hendee and Ritenour, 1992). 
An alternative way is to measure distribution of refractive 
index for X-rays. Spatial variation of refractive index 
causes spatial variation in the phase of the transmitted X- 
rays. By observing the phase variation, we can get images 
containing information of the inside of the object. This is 
70 
called phase imaging. 
Two methods are being investigated for observing the 
phase of X-rays. The first method corresponds to Shlieren 
method or shadowgraphy adopted for visualizing flow of 
transparent fluid with the visible rays (Merzkirch, 1974a). 
They measure the deviation of propagation direction of 
rays from the incident direction, which corresponds to the 
spatial differentiation of phase distribution. These methods 
give us high contrast X-ray images in a relatively easy way 
(Davis et al., 1995), but the resultant intensity is difficult to 
evaluate quantitatively. The other method is interferometry 
(Bonse & Hart, 1965) which is also used in flow 
visualization in the visible spectrum (Merzkirch, 1974b). 
Quantitative phase can be obtained. In the usual Mach- 
Zehnder type of X-ray interferometer, however, one of the 
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