How infrared sensors work

1.Active infrared sensors

Active infrared sensors work in the following sequence:

· An IR source (emitter) is used to emit radiation of the desired wavelength.

· This radiation reaches the object and is reflected back.

· The reflected radiation is detected by an IR receiver.

· The radiation detected by the IR receiver is then further processed based on its intensity.

Typically, the IR receiver output is small and an amplifier is used to amplify the detected signal.

The typical working of an IR sensor detection system can be understood through the diagram below.

Events in IR detection systems may be direct or indirect. In the case of direct incidence, there are no obstacles between the transmitter and receiver. While in indirect incidence, the infrared transmitter and receiver are placed side by side with the object in front of them.

2.Passive infrared sensor

Passive infrared sensors only contain detectors. There will be no transmitter component.

These types of sensors use objects as infrared sources/emitters. Objects radiate energy and are detected by infrared receivers. A signal processor is then used to interpret the signal to obtain the required information.

Examples of passive infrared sensors: thermocouple-thermopile, microbolometer, pyroelectric detector, etc. Microbolometer, also called infrared focal plane detector, is one of the sensors that can realize infrared thermal imaging and infrared temperature measurement.

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