| double convex lens | A lens with both surfaces convex. Synonym: convexoconvex lens, double convex lens. (05 Mar 2000) |
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| immersion lens | An objective (for a microscope) constructed in such a manner that the lower lens may be moved downward into direct contact with a fluid which is placed on the object being examined; by using a fluid with a refractive index closely similar to that of glass, the loss of light is minimised. (05 Mar 2000) |
| immersion of a lens | <physics> With nearly all high-power lenses, it is intended that the spaces between the condenser and the slide, and the specimen and the front lens of the objective be filled with an immersion liquid. Owing to the limitations imposed by the critical-angle phenomenon, numerical apertures are impossible exceeding 1.0 without immersion. In addition, immersion makes possible the use of the naturally aplanatic points of the front lens element of the objective. (05 Aug 1998) |
| omnifocal lens | A lens for near and distant vision in which the reading portion is a continuously variable curve. (05 Mar 2000) |
| orthoscopic lens | A spectacle lens corrected for distortion and curvature of the periphery. (05 Mar 2000) |
| electromagnetic lens | <apparatus> An electromagnet designed to produce a suitably shaped magnetic field for the focusing and deflection of electrons or other charged particles in electron optical instruments (cf. Electrostatic lens.) See: microscope, electron. (05 Aug 1998) |
| electron lens | <physics> A device for focusing an electron beam. (05 Aug 1998) |
| electrostatic lens | <physics> A lens employing a permanent magnet to produce a potential field capable of deflecting electron rays to form an image of an object. (cf. Electromagnetic lens). (05 Aug 1998) |
| toric lens | A lens in which both meridians are curved but not to the same degree. (05 Mar 2000) |
| trifocal lens | A lens with segments of three focal powers: distant, intermediate, and near. (05 Mar 2000) |
| epithelium of lens | The layer of cuboidal cells lying on the anterior surface of the crystalline lens inside the lens capsule. at the equator the cells elongate and give rise to the lens fibres. Synonym: epithelium lentis. (05 Mar 2000) |
| equator of lens | The periphery of the lens lying between the two layers of the ciliary zonule. Synonym: equator lentis. (05 Mar 2000) |
| exfoliation of lens | Sheetlike separation of the capsule of the lens; it may occur if the eyes are exposed to intense heat. (05 Mar 2000) |
| eye lens | <physics> The lens nearest the eye in any ocular. (05 Aug 1998) |
| fibres of lens | <biology, ophthalmology, physiology> The elongated cells of ectodermal origin forming the substance of the crystalline lens of the eye. Synonym: fibrae lentis. (05 Mar 2000) |