| biconvex lens | A lens with both surfaces convex. Synonym: convexoconvex lens, double convex lens. (05 Mar 2000) |
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| bifocal lens | A lens used in cases of presbyopia, in which one portion is suited for distant vision, the other for reading and close work in general; the reading addition may be cemented to the lens, fused to the front surface, or ground in one-piece form; other bifocal lens's are the flat-top Franklin type, or blended invisible. (05 Mar 2000) |
| Geneva lens measure | A device for measuring the radii of the curvature of a spectacle lens. Synonym: lens clock. Origin: Geneva, Switzerland (05 Mar 2000) |
| vergence of lens | The reciprocal of the principal focal distance used as a measure of the divergence or convergence of parallel rays. (05 Mar 2000) |
| cataract lens | Any lens prescribed for aphakia. (05 Mar 2000) |
| meniscus lens | A lens having a spherical concave curve on one side and a spherical convex curve on the other. Synonym: meniscus. (05 Mar 2000) |
| periscopic lens | A lens with 1.25 D base curve. (05 Mar 2000) |
| photochromic lens | A light-sensitive spectacle lens that reduces light transmission in sunlight and increases transmission in reduced light. (05 Mar 2000) |
| minus lens | A diverging minus power lens. Synonym: minus lens. (05 Mar 2000) |
| collimating lens | <physics> A lens used to produce a collimated beam from a light source. With a true point source on the axis the beam would be an axial tube of parallel rays With practical sources having real area the beam will be a diverging cone of parallel rays from each light point, this beam still has special properties and can be collected again by a good lens. (05 Aug 1998) |
| compound lens | An optical system of two or more lenses. (05 Mar 2000) |
| concave lens | A diverging minus power lens. Synonym: minus lens. (05 Mar 2000) |
| concavoconcave lens | A lens that is concave on two opposing surfaces. Synonym: concavoconcave lens, double concave lens. (05 Mar 2000) |
| concavoconvex lens | A converging meniscus lens that is concave on one surface and convex on the opposite surface. (05 Mar 2000) |
| condenser or condenser lens | <physics> A term applied to lenses or mirrors designed to collect, control, and concentrate radiation in an illumination system. (05 Aug 1998) |