2. Microwave holography

2.1 Principle

Microwave holography is a three-dimensional imaging technique that uses electromagnetic waves with wavelengths longer than visible light, generally in the microwave range extending to THz (1 GHz to 1 THz). Its principle is similar to that of optical holography; a reference wave is combined with a wave scattered by the object, forming an interference pattern recorded by a detector, usually digital. Unlike optical holography, it does not require photosensitive media, but uses electronic sensors to capture the signals.

Thanks to the longer wavelength of microwaves, this technique can penetrate certain materials that are opaque to light, such as walls or biological tissues. It is used in radar imaging, telecommunications, and hidden object detection....