Kraft, Timothy W. Department of Vision Sciences, School of Optometry, University of Alabama, Birmingham, Alabama.
Last reviewed:February 2021
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- Rifle sights
- Aircraft gunsights
- Artillery sights
- Additional Reading
Optical instruments that establish an optical line or axis for the purpose of aiming a weapon. The axis includes the observer's eye, a suitable mark in the instrument, and the target. For a pistol, the traditional iron sights employ a rear notch and a front post with midpoints that are aligned with each other and that of the target, while the flat top of each piece creates a horizon that is aligned with the vertical center of the target (Fig. 1). For dim light conditions, sighting is aided by high-contrast white dots or bars placed on the rear and front sights. Substituting tritium paint or vials of tritium gas creates a light source for superior visibility. “Night vision” aiming is possible with the use of image intensifiers and near-infrared [wavelengths of 820–950 nanometers (nm)] diodes or lasers, or true thermal imaging [using thermal radiation from warm objects at wavelengths greater than 4 micrometers (μm)], all of which require a mounted optical instrument (discussed below). The unaided rifle sight employs front and rear elements far enough apart that the two are not in simultaneous focus. Typically, the rear sight is a ring or loop that appears as a fuzzy circle around the front post. Concentric rings are perceptually easy to center with respect to one another, and thus a front aperture sight is often used (Fig. 2). See also: Infrared imaging devices; Infrared radiation; Light amplifier; Tritium
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