Editing Infrared (section)

=== Sensor response division scheme ===

[[File:Atmosfaerisk spredning-en.svg|thumb|Plot of atmospheric transmittance in part of the infrared region]]

A third scheme divides up the band based on the response of various detectors:<ref name="Miller">Miller, ''Principles of Infrared Technology'' (Van Nostrand Reinhold, 1992), and Miller and Friedman, ''Photonic Rules of Thumb'', 2004. {{ISBN|978-0-442-01210-6}}{{Page needed|date=September 2010}}</ref>
* Near-infrared: from 0.7 to 1.0&nbsp;μm (from the approximate end of the response of the human eye to that of silicon).
* Short-wave infrared: 1.0 to 3&nbsp;μm (from the cut-off of silicon to that of the MWIR atmospheric window). [[InGaAs]] covers to about 1.8&nbsp;μm; the less sensitive lead salts cover this region. Cryogenically cooled [[Mercury cadmium telluride|MCT]] detectors can cover the region of 1.0–2.5{{nbsp}}μm.
* Mid-wave infrared: 3 to 5&nbsp;μm (defined by the atmospheric window and covered by [[indium antimonide]], InSb and [[mercury cadmium telluride]], HgCdTe, and partially by [[lead selenide]], PbSe).
* Long-wave infrared: 8 to 12, or 7 to 14&nbsp;μm (this is the atmospheric window covered by HgCdTe and [[microbolometer]]s).
* Very-long wave infrared (VLWIR) (12 to about 30&nbsp;μm, covered by doped silicon).

Near-infrared is the region closest in wavelength to the radiation detectable by the human eye. mid- and far-infrared are progressively further from the visible spectrum. Other definitions follow different physical mechanisms (emission peaks, vs. bands, water absorption) and the newest follow technical reasons (the common [[silicon]] detectors are sensitive to about 1,050&nbsp;nm, while [[InGaAs]]'s sensitivity starts around 950&nbsp;nm and ends between 1,700 and 2,600&nbsp;nm, depending on the specific configuration). No international standards for these specifications are currently available.

The onset of infrared is defined (according to different standards) at various values typically between 700&nbsp;nm and 800&nbsp;nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700&nbsp;nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. Particularly intense near-IR light (e.g., from [[laser]]s, LEDs or bright daylight with the visible light filtered out) can be detected up to approximately 780&nbsp;nm, and will be perceived as red light. Intense light sources providing wavelengths as long as 1,050&nbsp;nm can be seen as a dull red glow, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). Leaves are particularly bright in the near IR, and if all visible light leaks from around an IR-filter are blocked, and the eye is given a moment to adjust to the extremely dim image coming through a visually opaque IR-passing photographic filter, it is possible to see the [[Wood effect]] that consists of IR-glowing foliage.<ref>{{Cite journal |last=Griffin |first=Donald R. |last2=Hubbard |first2=Ruth |last3=Wald |first3=George |year=1947 |title=The Sensitivity of the Human Eye to Infra-Red Radiation |journal=Journal of the Optical Society of America |volume=37 |issue=7 |pages=546–553 |bibcode=1947JOSA...37..546G |doi=10.1364/JOSA.37.000546 |pmid=20256359}}</ref>