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FIIG:  T150-F

Entry Date:  Apr-01-1974

Concept:  3

Status:  A

Applicability:  FA

Type:  0

Definition:  An auxiliary lens which is used in combination with a regular lens to increase or decrease focal length.

Basic INC:  70157

Basic Name:  LENS

Description:  1. A transparent optical element, or a combination of elements, usually made from optical glass having polished major surfaces, of which at least one is convex or concave in shape and usually spherical. The polished major surfaces are shaped so that they serve to change the degree of convergence or divergence of the transmitted rays. For a single element, or a combination of elements contained in a CELL, OPTICAL ELEMENT, see CELL ASSEMBLY, OPTICAL INSTRUMENT. For lenses designed specifically for photographic function, see Lens (3). 3. a transparent optical element, or a combination of elements, usually made from optical glass, designed to contorl, modify, and contribute to the formulation of an optical image on a photographic emulsion, diode gun tube, on light sensitive semiconductor elements, or on a screen for viewing. It is composed of a Lens (1), but it may be inclosed in a structural member, such as cell, barrel, cone, shutter, or any combination predicated on the engineered function of the item name. It may include provisions for focusing, photoflash synchronization, and it usually includes a diaphragm for light transmission control. For lenses designed for standard optical instruments, see Lens (1).