A Pyroelectric sensor is an infrared-sensitive optoelectronic component exclusively used for detecting any electromagnetic radiation found on a wavelength range of between 2 to 14 µm. The main, and undoubtedly most important, part of a pyroelectric sensor is the receiver chip, made up of single-crystalline lithium tantalite. It has a curie temperature of 620 °C. This curie temperature guarantees an extremely low-temperature coefficient with excellent long-term stability of the signal voltage.
How It Works
Before understanding how the pyroelectric sensor works, one must first know the science behind pyroelectric crystals and their nature. Pyroelectric crystals have a single polar axis, which gives them a rare asymmetry. This brings about the pyroelectric effect caused by a change of polarization with temperature change. The aforementioned pyroelectric effect is what enables the pyroelectric sensor to function in the way that it.
How the Pyroelectric Sensor Incorporates the Pyroelectric Effect?
Typically, the pyroelectric crystal will be coated with electrodes at a right angle to the polar axis. A black surface, or any other absorbing layer, will be applied on the upper electrode. The surface needs to be a heat absorber for this to work. Once the layer catches any hint of infrared radiation, the pyroelectric layer will heat up, thus causing a surface charge. When the radiation is switched off or dies down, an extremely low charge of the opposite polarity originates.
Before the charges are equalized by the finite internal resistance of the crystal, an operational amplifier, or extremely low-noise and low leakage current field-effect transistors (JFET) convert the charges into a signal voltage.
Pyroelectric Sensor with Integrated Beam Splitter
Other than the pyroelectric crystal, some pyroelectric infrared sensors have optical and micro-mechanical components, two-channel and four-channel pyroelectric sensors, to be specific. They have integrated beam splitters, and integrated CMOS amplifiers as well as micro-systems consisting of elements which function thermally, electronically and optically.
Application of The Pyroelectric Effect
There are dozens of ways in which one can make use of the pyroelectric effect. The applications range from those of an advanced technology nature, for example, interplanetary probes and radiometers in weather satellites to simple thermal detectors that have extensive commercial and industrial applications.
The technology also makes important contributions to infrared spectroscopy, absolute radiometry, as well as laser research. Other than its use in simple thermal imaging systems, the pyroelectric vidicon is now widely used in laser interferometers and other applications that require a two-dimensional detector.
Pros of Using A Pyroelectric Detector
In comparison to the Golay cell, which more or less serves the same purpose, the pyroelectric sensor is almost as sensitive but can be used either windowless or with windows. It also has a black absorber, which enables a flat spectral response. In addition, it is inherently fast, has a wide operating temperature range, is small, therefore easy to carry around, and can be operated off either batteries or an AC supply.
Pyroelectric sensors are, without a doubt, one of the best thermal detectors on the market, which is owed to the fact that they incorporate cutting edge technology and are also very efficient and accurate at what they do.