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Internal focusing, which focuses binoculars by moving internal mounted optical lenses located between the objective lens group and the prism assembly – or rarely located between the prism assembly and eyepiece lens assembly – within the housing without changing the volume of the binoculars. The addition of a focusing lens reduces the light ...
PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. [1] [2] [3] The program is also known by the SIGAD US-984XN. [4] [5] PRISM collects stored internet communications based on demands made to internet companies such as Google LLC ...
Adjustable focus eyeglasses are eyeglasses with an adjustable focal length. They compensate for refractive errors (such as presbyopia) by providing variable focusing, allowing users to adjust them for desired distance or prescription, or both. Current bifocals and progressive lenses are static, in that the user has to change their eye position ...
Single lenses have a variety of applications including photographic lenses, corrective lenses, and magnifying glasses while single mirrors are used in parabolic reflectors and rear-view mirrors. Combining a number of mirrors, prisms, and lenses produces compound optical instruments which have practical uses.
The simplest compound prism is a doublet, consisting of two elements in contact, as shown in the figure at right. A ray of light passing through the prism is refracted at the first air-glass interface, again at the interface between the two glasses, and a final time at the exiting glass-air interface. The deviation angle of the ray is given by ...
An aspheric lens or asphere (often labeled ASPH on eye pieces) is a lens whose surface profiles are not portions of a sphere or cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens . The asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce ...