Reflectometry uses the reflection of waves at surfaces and interfaces to detect or characterize objects. There are many different forms of reflectometry. They can be classified in several ways: by the used radiation (electromagnetic, ultrasound, particle beams), by the geometry of wave propagation (unguided versus wave guides or cables), by the involved length scales (wavelength and penetration depth versus size of the investigated object), by the method of measurement (continuous versus pulsed, polarization resolved, ...), and by the application domain.
