Night vision

Night vision is used to describe both biological and technological methods used for seeing in an environment with very low light. Most instances use a combination of two approaches: Enhanced spectral range, and enhanced intensity range.

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Enhanced spectral range is where the viewer is sensitive to light beyond what would be considered normal by a human observer. Human vision is confined to a very small portion of the electromagnetic spectrum which is considered light. This allows the viewer to take advantage of additional sources of light, or make more effective use of the available sources of light.

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Enhanced intensity range is simply the ability to see with very small quantities of light. Although the human visual system can, in theory, detect single photons under ideal conditions the neurological noise filters limit sensitivity to where a few tens of photons are required even in ideal conditions http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html.

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Some animals have achieved improved night vision evolutionarily though the use of a larger optical aperture, improved retina composition which can detect weaker light over a larger spectral range, more photoefficent optics in the eye, and improved neurological filtering which is more tolerant of noise. Enhanced intensity range is achieved via technological means through the use of an image intensifier, photo-multiplier tube, or other very low noise and high sensitivity array of photo-detectors.

Related Topics:
Optical aperture - Image intensifier

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