"Wave CT" as a Short-Range Sensing with Superresolution

Abstract

We proposed a superresolved "Wave CT" which utilizes fundamental properties of the wave, i.e. diffraction, refraction, reflection, and attenuation. It solves the Helmholtz equation which has a complex wave number including both refractive index and attenuation coefficient, and reconstructs superresolved complex images of the objects. The fundamentals of the wave CT are the following two points: first, the wavelength of the wave used is much longer than the structure of the object to be imaged; second, the phase information of the wave traveled through the object contributes much more to the image reconstruction than the amplitude information. Just as the X-ray CT is the extremum of the short-wavelength imaging, which may be called "Particle CT," the wave CT is the extremum of the long-wavelength imaging. Therefore, we named it "Wave CT." The mathematical method of the wave CT cannot be independent of itself, and we proposed a combination of FEM and BEM. It is not a perturbation method unlike the so-called diffraction tomography. Therefore, the dynamic range of the reconstructed image is unlimited in principle, but it is limited in practice by numerical problems. This paper reports a development of the numerical calculation, i.e. very exact and wide dynamic range images are reconstructed, which is relatively insensitive to the noise component of the projections. As an example, human body tomography by the wave CT is considered with radio wave of about 100MHz.