Object Shape Recognition by microwave

An electromagnetic wave upon meeting a boundary between air/dielectric or air/conductor can be dispersed

The dispersion causes the wave to be in part returned back to its source, (reflection), or, turned aside, or, bent from the original propagation direction.
This "mechanism" is the same in any part of spectrum, UV, visible, IR, or microwave. The advantage of microwaves is that the wavelength is comparable with tested objects, so reflection and/or dispersion is intense and predictable.
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To recognize "shape" of various objects, there are many types of sensors, operating with reflected, dispersed or passed-through waves. Some directional antennas are needed, together with mechanical or electrical scanning, to evaluate the field changed by a tested object, and deduce its shape, distance, material, etc.