Pyroelectric Infrared Detectors (PIR)convert the changes in incoming infrared light to electric signals. Pyroelectric materials are characterized by having spontaneous electric polarization, which is altered by temperature changes as infrared light illuminates the elements. Since our sensor series uses this effect they can be used at ambient temperature even in the presence of thermal noise. By choosing appropriate IR receiving electrodes, they serve a wide range of application.
| High Sensitivity |
| Versatile selection of IR wavelength filters |
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Unlike semiconductor detectors, pyroelectric detectors are thermal detectors working with a thermally isolated chip which is covered by a black absorption coating. This coating converts the infrared radiation falling on the chip to heat. The chip changes its temperature in the order of magnitude of µK … mK and, as a result of the pyroelectric effect, produces the electrical signal desired. Thermopiles, too, belong to the group of thermal detectors, however, the measuring effect is less significant. While pyroelectric detectors show a good signal/noise ratio up to modulation frequencies of 4 kHz, e.g. in FTIR spectrometers, thermopiles produce good results up to modulation frequencies of specific Hertz only.
Pyroelectric detectors with integrated beamsplittieogy InfraTec
In addition to the pyroelectric crystal, pyroelectric detectors by InfraTec contain optical and micro-mechanical components. Two-channel and four-channel pyroelectric detectors with integrated beamsplitter and integrated CMOS amplifier are micro-systemsconsisting of components which function thermally, electronically and optically.
As pyroelectricity is a characteristic of a subgroup of piezoelectric crystals, pyroelectric detectors react to airborne and solid-borne sound. This effect is often called microphony. However, a patented fastening of the pyroelectric chip by InfraTec reduces these negative ffects for pyroelectric detectors dramatically so that in many cases these negative effects are in the order of magnitude of other interference voltage or of the inherent noise of the detector only
How does a pyroelectric detector work?
When light radiation (UV, VIS, IR, THz) is applied to a thin pyroelectric crystal (<40µm) its temperature increases by fractions of a degree centigrade. Turning on the radiation an electrical charge is generated by heating, turning off the light the crystal cools down and an opposite charge is generated. These very small electrical charges are generally converted within the detector housing to convenient signal voltages by use of extremely low noise and low leakage Field Effect Transistors (JFET) or CMOS operational amplifiers (OpAmp). It is very important to remember that only modulated radiation creates a signal, therefore either pulsed or mechanically chopped IR sources are used and unmodulated disturbing background radiation is filtered out.
In what wavelength range do pyroelectric detectors operate?
As the thermal effect of the incoming radiation is used to produce the electrical detector response, electromagnetic radiation from deep UV (100nm) over the visible range to the far infrared up to the THz range (1000µm) can be detected, as long as the pyroelectric crystal is covered with a suitable absorption layer. InfraTec use two different coating technologies for black absorbing layers. The polymer black coating is used for most detectors and offers extremely stable long term absorption from UV up to 100µm IR even for high...