Types of IR Sensors
Infrared sensors can be classified into passive or active
infrared sensors.
1) Passive infrared
sensor
These are IR sensors which do not have an infrared
source but detects energy emitted by obstacles. They are of two types namely:
- Thermal infrared sensor: use infrared energy as a source of heat and are independent of wavelength.
- Quantum infrared sensor: The photo-sensitivity of quantum type detectors is dependent on the wavelength and are perform better than thermal infrared sensors.
 |
| Passive infrared sensor |
2) Active infrared
sensors
These are IR sensors which contains an infrared source
and infrared detector. The infrared source is an IR LED and the receiver can be
a photodiodes or a phototransistors.
These sensors can be used in object sensing, obstacle
avoidance robot, motion detectors, measurement of distance, smoke detection
etc.
The figure below show a typical photodiode infrared
sensor.
 |
| A typical infrared sensor |