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Lasers and Image Intensifiers

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Matthew Kelleher

on 28 April 2010

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Transcript of Lasers and Image Intensifiers

LASERS, Light amplification by stimulated emission of radiation An atom can become excited when it absorbs enough energy in the form of heat, light, or electricity. However, atoms like to stay in its ground state as it is more stable. Therefore, atoms that are excited usually return to their ground state relatively quickly, within nanoseconds. Before an excited electron can return to its ground state, it must first release the absorbed energy. The energy released is equal to the difference between the two energy levels of transition (E = E2 E1) and is released in the form of a photon, the basic unit of light! This is known as spontaneous emission. This concept is named rather appropriately as excited electrons “de-excites” quite randomly and the photon released is also non-directional (it shoots out in random directions).

An Image Intensifier is a vacuum tube that amplifies a low light-level scene to observable levels. The object lens collects light and focuses it onto the Image Intensifier. At the photocathode of the Image Intensifier the incoming light is converted into photo-electrons.

These photo-electrons are accelerated in an electric field and multiplied by a Micro Channel Plate (MCP). An MCP is a very thin plate of conductive glass containing millions of small holes.

An electron entering a channel strikes the wall and creates additional electrons, which in turn create more electrons (secondary electrons), again and again. Subsequently the highly intensified photo-electrons strike the phosphor screen and a bright image is emitted that you can see.
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