Animals generate heat in the form of infrared radiation. While this heat can be detected naturally through physical touch, infrared radiation is associated with a wavelength of the electromagnetic spectrum that is not visible to the naked eye. Infrared detectors, however, are devices that use sophisticated components -- such as lenses, beam splitters and pyroelectric sensors -- that, when combined, give us a visual representation of the heat generated by animals and objects. This way we can tell what's hot and what's not without ever having to touch it.
Infrared Windows
Composite infrared windows are composed of a polyethylene plastic film attached to a thin silicon substrate. The window provides an external particle impact absorbing layer that is transparent to long wave radiation. If the infrared detector is being used outdoors, it is important that the infrared window be enclosed in a weatherproof casing.
Fresnel Lenses
A Fresnel lens is a Plano convex lens that has been distorted to form a flat lens. Although the lens still maintains its optical characteristics, it is much thinner and, consequently, bears less absorption losses when used in infrared detectors.
Wedge Filters
A wedge filter is an optical filter specifically constructed so that its thickness gradually increases. Wedge filters are used in infrared detectors to modify the intensity of dispersion of radiation beams.
Mirrors
Within infrared detectors, multifaceted mirrors collect infrared radiation and focus it on a single sensing element. Each facet of each mirror should have a concave surface that is oriented to collect radiation from a specific field of view and reflect it onto the sensing element.
Beam Splitters
A beam splitter is an optical instrument that splits a beam of light in two. Infrared beam splitters are typically made out of zinc selenide substrates and then coated with dielectric materials that reflect and transmit extremely short wavelengths.
Pyroelectric Sensors
Pyroelectric sensors are composed of a crystalline material that produces an electric charge on its surface when exposed to thermal radiation. As the amount of radiation contacting the crystal changes, the amount of charge also changes. This difference in charge can be measured by special field-effect transistors (FET) located within the sensor.
Tags: infrared detectors, infrared radiation, beam splitters, sensing element, used infrared, used infrared detectors