Implementation of microwave diffraction tomography for measurement of dielectric constant distribution

Diffraction tomography is a process that can infer the internal structure of an object from multiple views of its diffraction shadow. The procedure is sensitive to variations in the object´s refractive index and there is interest in using the technique to measure permittivity distributions within dielectric objects and to image soft tissues for biomedical applications. To allow the inversion to proceed, a number of conditions have to be met. These determine the type of object to be studied, the geometry of the microwave system and surrounding environment. The optimal resolution distance obtainable is half a wavelength, but this can rarely be achieved because of practical limitations. Some procedures, however, are available to improve the practical resolution. One, which is suitable for microwave tomography, is to use multifrequency data and to combine the resulting images. A system operating over the X-Band microwave frequency range is described and some results for test objects in air are given