About active infrared sensor

Active infrared sensors contain a transmitter and a receiver. Most often, LEDs or laser diodes are used as light sources. Use LEDs for non-imaging infrared sensors and laser diodes for imaging infrared sensors.

Active infrared sensor

Active infrared sensors work by radiating energy, which is received and detected by a detector and further processed by a signal processor to obtain the required information.

Examples of active infrared sensors: interrupted beam sensors, reflective sensors.

Infrared sensors apply three basic laws of physics

· Planck’s Law of Radiation: Any object with a temperature not equal to absolute zero (0 Kelvin) emits radiation.
· Stefan Boltzmann's law: The total energy emitted by a black body at all wavelengths is related to the absolute temperature.
· Wen's shift law: The spectra emitted by objects at different temperatures reach peaks at different wavelengths that are inversely proportional to the temperature.

Key elements of active infrared detection systems

The key elements of an infrared detection system are:

Infrared transmitter

IR emitters act as sources of IR radiation. According to Planck's radiation law, every object is a source of infrared radiation at a temperature T above 0 Kelvin. In most cases, blackbody radiators, tungsten lamps, silicon carbide, infrared lasers, LEDs of infrared wavelengths are used as light sources.

Transmission medium

As the name suggests, the transmission medium provides a path for radiation to travel from an infrared transmitter to an infrared receiver. Use vacuum, atmosphere and fiber optics as media.

Infrared receiver

Typically IR receivers are photodiodes and phototransistors. They are able to detect infrared radiation. Therefore, IR receiver is also called IR detector. A variety of receivers are available based on wavelength, voltage and packaging.

IR transmitter and receiver selection matching parameters

Some of the determining specifications of a receiver are light sensitivity or responsivity, noise equivalent power, and detection.

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