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A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses ( elements ), usually arranged along a common axis.
Opaque projector. An episcope which was used in a University of Cambridge lecture hall in the late 1800s. The opaque projector, or episcope is a device which displays opaque materials by shining a bright lamp onto the object from above. The episcope must be distinguished from the diascope, which is a projector used for projecting images of ...
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- ( a-) meaning "without" and ...
Reflector (cipher machine) A reflector, in cryptology, is a component of some rotor cipher machines, such as the Enigma machine, that sends electrical impulses that have reached it from the machine's rotors, back in reverse order through those rotors. The reflector simplified using the same machine setup for encryption and decryption, but it ...
Orthokeratology, also referred to as Night lenses, Ortho-K, OK, Overnight Vision Correction, Corneal Refractive Therapy (CRT), Accelerated Orthokeretology, Cornea Corrective Contacts, Eccentricity Zero Molding, and Gentle Vision Shaping System (GVSS), is the use of gas-permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia, hyperopia, and ...
A catadioptric optical system is one where refraction and reflection are combined in an optical system, usually via lenses ( dioptrics) and curved mirrors ( catoptrics ). Catadioptric combinations are used in focusing systems such as searchlights, headlamps, early lighthouse focusing systems, optical telescopes, microscopes, and telephoto lenses.
Wray (Optical Works) Ltd. Wray (Optical Works) Ltd. was a British camera and lens manufacturer based in Ashgrove Road, Bromley, Kent, UK. It operated from 1850 to 1971, making lenses for cameras, photographic enlargers, reconnaissance, mapping, microchip replication, and an anamorphic projection system for cinemas. It also made binoculars.
A prism was placed in front of the lens to reverse the image. After a 10-second exposure, the paper was directed to developing and fixing baths, then either air- or machine-dried. Since the print was directly exposed, without the use of an intermediate film, the result was a negative print. A typical typewritten document would appear on the ...