Nonoptical

Nonoptical is an adjective used to describe phenomena, devices, methods, or systems that do not rely on optical processes or visible light to function. In practice, the term is often used to distinguish non-photonic techniques from optical or photonic approaches that depend on photons to transfer information, form images, or measure properties.

The scope of nonoptical methods is broad. Nonoptical sensing relies on signals such as electricity, magnetism, acoustics, or mechanics rather than light. Examples include ultrasound imaging, magnetic resonance imaging, radar or other radio-frequency imaging, and various electrical or piezoelectric sensors. In materials science and nondestructive testing, nonoptical techniques are used to assess composition, structure, or integrity without requiring optical access. Nonoptical communication methods use radio or other non-light signals rather than optical carriers.

The boundary between optical and nonoptical can be imperfect. Some instruments combine optical and nonoptical subsystems, and certain modalities involve radiation outside the visible range that is still described as optical in some contexts. Overall, nonoptical emphasizes the use of non-photonic signals or mechanisms, serving as a useful contrast in discussions of measurement, imaging, and sensing technologies.