Infrared Sensor – IR Sensor
An infrared sensor (IR sensor) is a radiation-sensitive optoelectronic component with a spectral sensitivity in the infrared wavelength range 780 nm … 50 µm. IR sensors are now widely used in motion detectors, which are used in building services to switch on lamps or in alarm systems to detect unwelcome guests. In a defined angle range, the sensor elements detect the emitted IR radiation (heat radiation) that changes over time and space due to the movement of people. Such infrared sensors only have to meet relatively low requirements and are low-cost mass-produced items. InfraTec does not supply such products, InfraTec develops, produces and sells pyroelectric detectors.
Working Principle of Infrared Sensors
Pyroelectric detectors are passive infrared sensors. They do not send out IR light like active infrared sensors and therefore they have a very low energy consumption. They can only detect changes in temperature.
The core of a pyroelectric detector is the pyro chip, made of a crystalline material with polar properties. In many crystals, positive and negative charge centres do not coincide, creating polarization. Pyroelectric crystals also have a single polar axis and their polarization changes with temperature. This so-called pyroelectric effect is used in sensing technology.
The pyroelectric detector contains a thin crystal coated with electrodes perpendicular to the polar axis, and an absorbing black layer on the upper electrode. When infrared light hits this layer, the pyroelectric material heats up and surface charges are generated. When the radiation is switched off, charges of opposite polarity are generated, amplified and converted into a signal voltage. Since the detector only reacts to changes in radiation, the source is usually modulated, except for self-fluctuating emitters like flames.
Pyroelectric detectors offer broad spectral sensitivity, from UV to terahertz wavelengths, depending on the absorption coating. As all pyroelectric materials are also piezoelectric, they respond to vibrations (microphonic effect). InfraTec minimizes this through a patented mounting, reducing noise in all directions. Thermal compensation further stabilizes the detector by reducing the influence of ambient temperature changes.
Sensor Types and their Features
The pyroelectric IR sensor uses a wavelength range from 2 to 14 µm. InfraTec uses special absorption layers so that the infrared sensors can even work as large-area, long-term stable receivers for UV radiation (e.g. 193 nm) but also for THz radiation in the range of 100 µm … 1 mm.
Further infrared sensors are Golay cells, bolometers and thermopiles, which also belong to the thermal IR sensors. The change in pressure of a gas volume is evaluated in a Golay cell and the change in temperature of a solid is evaluated in a bolometer. Thermopiles basically represent a series connection of thermocouples with an absorption layer and use the Seebeck effect. Photodiodes use the inner photo effect. At the same time, radiation quanta generate charge carrier pairs within a semiconductor. In the case of photoresistors, the radiation changes the electrical resistance.
Would You Like to Know More?
It is not unusual for tasks to be associated with special requirements. Discuss your specific application needs with our experienced engineers, receive further technical information or learn more about our additional services.
Use in Low and High Temperature Ranges
Depending on the basic physical principle, an IR sensor can work in a wide temperature range without cooling (so-called thermal infrared sensor) or must be cooled or at least thermally stabilized (semiconductor resistor or semiconductor diode) to achieve a good signal-to-noise ratio (detectivity).
A pyroelectric infrared sensor from InfraTec can basically work in the temperature range from - 55 to + 200 ° C. The pyroelectric sensor element made of lithium tantalate (LiTaO3) has a Curie temperature of over 600 ° C, which would also enable significantly higher operating temperatures. The temperature-limiting elements of a pyroelectric infrared sensor are the infrared window or infrared filter as well as integrated, extremely low-noise and low-leakage preamplifier technology.
Detector Search
InfraTec offers different product groups including approximately 50 standard pyroelectric detectors. Detectors with reduced microphone technology and integrated operational amplifier as well as digital detectors are part of our product range.
Choose your suitable infrared detectors with the help of our detailed detector search.
