Photonics Dictionary

active infrared system

An active infrared (IR) system is a type of technology that uses infrared radiation actively emitted and detected by sensors for various purposes. Here are the key features and applications of active infrared systems:

Principle: Active IR systems operate by emitting infrared radiation from a transmitter (often an IR LED) and detecting the reflected or interrupted IR radiation with a receiver (usually an IR photodiode or sensor). The presence or absence of the IR signal, as well as changes in its intensity or pattern, can be used to detect objects, motion, or other phenomena.


Security systems: Used in motion detectors and perimeter security systems to detect intrusions or movement in designated areas.

Automatic door systems: Employed in automatic door openers to sense the presence of individuals approaching the door.

Object detection and ranging: Used in robotics and automation for proximity sensing and obstacle detection.

Data transmission: Utilized in IR communication systems where data is transmitted using modulated IR signals.


Active IR systems can provide precise detection and ranging capabilities.

Robustness: They are less affected by ambient light conditions compared to passive IR systems.

Versatility: Suitable for various indoor and outdoor applications due to adjustable sensitivity and range settings.

Components: Typical components of an active IR system include IR transmitters, receivers, lenses for focusing IR beams, and signal processing electronics to interpret the received IR signals.

Limitations: Active IR systems may be susceptible to interference from other IR sources or reflective surfaces, and their effectiveness can be influenced by environmental factors such as weather conditions.
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