page_title: Night-vision device
section_title: Generation 3+ (GEN III OMNI IV–VII)
hierarchical_section_title: Night-vision device / History / United States / Generation 3+ (GEN III OMNI IV–VII)
caption_attribution_description: English: Functional diagram of an image intensifier. (See Image intensifier) This graphic was adapted from File:Photomultiplier.JPG. Text was removed from the graphic so it could be used in document written in any language.
context_page_description: A night-vision device, also known as night optical/observation device and night-vision goggles, is an optoelectronic device that allows images to be produced in levels of light approaching total darkness. The image may be a conversion to visible light of both visible light and near-infrared, while by convention detection of thermal infrared is denoted thermal imaging. The image produced is typically monochrome, e.g. shades of green. NVDs are most often used by the military and law enforcement agencies, but are available to civilian users. The term usually refers to a complete unit, including an image intensifier tube, a protective and generally water-resistant housing, and some type of mounting system. Many NVDs include a protective sacrificial lens, or optical components such as telescopic lenses or mirrors. An NVD may have an IR illuminator, making it an active as opposed to passive night-vision device.
  Night-vision devices were first used in World War II and came into wide use during the Vietnam War. The technology has evolved greatly since their introduction, leading to several "generations" of night-vision equipment with performance increases and price reductions.
context_section_description: The US Army Night Vision and Electronic Sensors Directorate (NVESD) is part of the governing body that dictates the name of the generation of night-vision technologies. This was originally the Army Night Vision Laboratory (NVL), which worked within the US Army Research Labs. Although the recent increased performance associated with the GEN-III OMNI-VI/VII components is impressive, the US Army has not yet authorized the use of the name GEN-IV for these components.
  GEN-III OMNI-V–VII devices developed in the 2000s can differ from standard generation 3 in one or both of two important ways. First, an automatic gated power supply system regulates the photocathode voltage, allowing the NVD to instantaneously adapt to changing light conditions. The second is a removed or greatly thinned ion barrier, which decreases the number of electrons that are usually rejected by the standard GEN III MCP, hence resulting in less image noise and the ability to operate with a luminous sensitivity at 2850 K of only 700, compared to operating with a luminous sensitivity of at least 1800 for GEN III image intensifiers.  The disadvantage to a thin or removed ion barrier is the overall decrease in tube life from a theoretical 20000 h mean time to failure (MTTF) for Gen III type, to 15000 h MTTF for GEN IV type. However, this is largely negated by the low number of image intensifier tubes that reach 15000 h of operation before replacement.
  While the consumer market classifies this type of system as generation 4, the United States military describes these systems as generation 3 autogated tubes (GEN-III OMNI-VII). Moreover, as autogating power supplies can now be added to any previous generation of night-vision devices, "autogating" capability does not automatically class the devices as a GEN-III OMNI-VII. Any postnominals appearing after a generation type (i.e., Gen II+, Gen III+) do not change the generation type of the device, but instead indicates an advancement(s) over the original specification's requirements.
  Examples:
  AN/PVS-22
  NVS-22
caption: Generation II, III and IV devices use a microchannel plate for amplification. Photons from a dimly lit source enter the objective lens (on the left) and strike the photocathode (gray plate). The photocathode (which is negatively biased) releases electrons, which are accelerated to the higher-voltage microchannel plate (red). Each electron causes multiple electrons to be released from the microchannel plate. The electrons are drawn to the higher-voltage phosphor screen (green). Electrons that strike the phosphor screen cause the phosphor to produce photons of light viewable through the eyepiece lenses.
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