Infrared (IR) sensors are used in night vision cameras and goggles to detect heat emitted by objects. Since ambient light is absent, radiations emitted by the object are picked up by the sensors and used to form an image of the object. These devices can detect the presence of an intruder and are very important in guarding sensitive infrastructure. They are also used for non-contact temperature measurement.
How it works:
Red color has the longest wavelength and infrared means the wavelengths below this visible red. The IR detecting unit uses a silicon photodiode as the light-detecting source to convert the infrared radiation into an electric current. Since an object like a human body has different temperature zones, the electric current that is produced will also vary and can be used to form a map of temperatures or varying infrared colors from dark red to blue.
Selection:
The following factors are useful in selection:
- Responsivity - the responsivity at different frequency range measured in mV
- Sensitivity is a very crucial factor in infrared sensors and it should be very high and efficient.
- Field of view - the circular range in which the unit can sense radiation
- Stability
- Type of electrode
- Response time is the time taken by the sensor to detect, sense the object and send response.
- IR sensors are used to build cameras or radiation detecting units, night vision goggles, and security and monitoring equipment.
- IR sensors find usage in process industries where the temperature can be between –30 deg C to 3000 deg C. Some of the process industries are paper, glass, metals, plastics, cement, chemical, food, petrochemical, textiles, etc.
- They also help firefighters to see smoke and save lives. PDAs and other computers and digital cameras use infrared technology to send and receive data.
- They are also used in motion detection and other equipment.
Author: Ashutosh Saini (Component Engr.)
