Pyroelectric detectors are sensors of radiation based on their pyroelectric effect. The detectors are usually sensitive to wavelengths within the infrared region of the spectrum. The name pyroelectric is derived from two words, Pyr, a Greek word meaning fire and electricity. Pyroelectric crystals are naturally electrically polarized and used in the manufacture of pyroelectric detectors. These crystals generate a temporary voltage when subjected to temperature changes. The voltage changes occur when the position of atoms within the structure of the crystal changes due to temperature changes. At a stable temperature, the voltage in the pyroelectric crystals gradually disappears due to leakage current.
Applications of Pyroelectric detectors
Pyroelectric detectors are applied in various fields. Some of the most popular applications are;
Manufacture Of Contactless Thermometers
Contactless, also known as infrared, thermometers are among the modern developments in the medical field. The thermometers are made with photoelectric detectors linked to a calibrated scale. Once the thermometer is pointed at an individual’s exposed body part, especially the head, the detectors pick up the body’s heat. The heat radiated by an individual causes generation of a voltage in the pyroelectric detectors, which in turn record the amount of heat received in the form of degree Celsius.
Infrared cameras are very important in research and rescue missions. The cameras can be used to tell the position of people or objects if the site of view is blocked. The pyroelectric detectors in an infrared camera pick up heat energy radiated by objects. The heat generates a current in the photoelectric detectors. The current generated is then translated to give visible shapes depending on the frequency of the radiation received by the detectors. In some cases, the radiation received is matched with available frequencies to determine the possibility of the presence of what is being sought for.
Face And Shape Recognition Systems
Pyroelectric detector played a significant role in the technological advancement of security systems. Face recognition is among the latest security features for electronics, such as phones. Face detection algorithms are made to record the heat radiation emitted from different parts of an individual’s face. Once a pattern has been established, the device can be unlocked if the heat radiation pattern matches the initial one received by the pyroelectric detectors. In security scanners, such as in airports and malls, photoelectric sensors generate images of what is contained in bags and parcels. Items have different radiation emission frequencies; the radiation is projected on pyroelectric surfaces forming shapes of different items contained in the bags and parcels. The same principle is used to scan people.
There are many other applications of pyroelectric detectors. These include carbon dioxide detection by rescue teams to determine whether a victim is still alive. However, using these detectors have several disadvantages. Other than the high costs of acquiring and maintaining pyroelectric devices, the continued use of these devices exposes an individual to harm by the radiation involved. For instance, the radiation projected on individuals at scanning points could be harmful to body cells.