What is an IR Detector?

IR Detector or Infrared detector

An infrared detector is a detector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic (photodetectors).

The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena. Bolometers and microbolometers are based on changes in resistance. Thermocouples and thermopiles use the thermoelectric effect. Golay cells follow thermal expansion. In IR spectrometers the pyroelectric detectors are the most widespread.

The response time and sensitivity of photonic detectors can be much higher, but usually these have to be cooled to cut thermal noise. The materials in these are semiconductors with narrow band gaps. Incident IR photons can cause electronic excitations. In photoconductive detectors, the resistivity of the detector element is monitored. Photovoltaic detectors contain a p-n junction on which photoelectric current appears upon illumination.

How do IR Detectors Work?

Infrared sensors, as mentioned above, work with infrared radiations. The functioning depends on if the sensor is active or passive (PIR).

Active infrared sensors work with radar technology and they both emit and receive infrared radiation. This radiation hits the objects nearby and bounces back to the receiver of the device. Through this technology, the sensor can not only detect movement in an environment but also how far the object is from the device. This is especially useful in robotics to detect proximity.

Why is there a need for IR detectors?

Powerful laser sources, mainly high-power CO2 and solid-state lasers, have for many years been used on quick and precise hard material treatment, large format cutting, engraving, cleaning and welding markets. Such sources operate within the mid infrared range, as high absorptivity of that type of radiation enables contact-free modification of materials by means of heating. A natural consequence of that situation is a demand for sensors operating within the same range of spectrum as lasers do, and enabling control of beam power and position.