Spectacle lenses of glass

90.01 - Optical fibres and optical fibre bundles; optical fibre cables other than those of heading 85.44; sheets and plates of polaris~ngmaterial; lenses (including contact lenses), prisms, mirrors and other optical elements, of any material, unmounted, other than such elements of glass not optically worked. - Optical fibres, optical fibre bundles and cables 9001.20 - Sheets and plates of polarising material 9001.30 - Contact Ienses 900 1.40 - Spectacle lenses of glass 9001.50 - Spectacle lenses of other materials 9001.90 - Other 900 1.10 This heading covers : (A) Optical fibres and o tical fibre bundles, as well as optical fibre cables other than those of heading 8 5 . d 0 tical fibres consist of concentric layers of glass or lastics of different refractive & ~Flastics,invisible to the naked in 'ces. Those drawn from glass have a ve thin Optical ibres are usual1 resented on eye, which renders the fibres less prone to acture. reels and ma be several kilometers in length. They are used to make optica ibre bundles and optical lbre cables. % TP ? OpticaI fibre bundles may be rigid, in which case the fibres are agglomerated by a binder along their full length, or they may be flexible, in which case they are bound only at their ends, If coherently bundled, they are used for transmission of Images, but if randomly bundled, they are suitable only for transmission of light for illumination. Optical fibre cables of this headin which may be fitted with connectors) consist of a sheath containing one or more optica ibre bundles, the fibres of which are not individually sheathed. el Optical fibre bundles and cables are used primarily in optical apparatus, particularly in endoscopes of heading 90.18. (13) Polarising material in sheets or plates which consist of specially treated sheets or plates of lastics, or of sheets or plates in which a layer of" active "plastics is supported on one ! or 0th sides by other plastics or b lass. This sheet or plate material is cut to shape to make the polarising elements descri e at Item (6) below. 8% (C) Optical elements of glass, optically worked, not permanently mounted. In order tp distinguish between optical elements of glass of this headin and those of Chapter 70 it is necessary to determine whether or not they have been optica ly worked. y elements which have been (D) Optical elements of any material other than glass, whether or not optically worked, not permanently mounted (e.g., elements of quartz (other than fused quartz), fluorspar, plastlcs or metal; optical elements in the form of cultured crystals of magnesium oxide or of the halides of the alkali or the alkaline-earth metals). Optical elements are manufactured in such a way that they roduce a re uired optical effect. An optical element does more than merely allow li ht (vlsi le, ultravio et or mfrared) to pass through it, rather the assage of light must be a tered in some way, for example, by being reflected, attenuated, fi tered, diffracted, collimated, etc. P % Optical elements with a temporary mounting provided solely for protection during transport are considered to be unmounted. Subject to the provisions set out above regarding optical elements of glass, this heading includes : (1) Prisms and lenses (including corn ound prisms and lenses assembled by means of an adhesive cement), whether or not wi% unfntshed edges. (2) Plates and discs with lane or lane-parallel faces (e.g., proof planes or optical flats for checking the flatness o a surface7. P (3) Ophthalmic lenses. These lenses may be aspherical, spherical, sphero-cylindrical, uni-focal, bi-focal or multi-focal. They also include contact lenses. (4) Mirrors constituting optical elements. These are used, for example, in telescopes, projectors, microscopes, medical, dental or surgical instruments, and sometimes as vehicle rear-view mirrors. (5) Colour fdters (e.g., for photographic cameras). (6) Polarising elements (for microscopes or other scientific instruments; for sunglasses; for spectacles for viewing three-dimensional cinernatograph films, etc.). (7) Diffraction gratings. These may be : (a) Highly polished lass on which parallel lines have been cut close together at regular intervals (e.g., 10 lines per millimetre). E (b) " Replica " atings consistin of a thin film of plastics or gelatin on a support such as a plate of g ass. The thin fi m bears an impression of the lines of an original ruled grating. T P These gratings are used in the same way as prisms for study of spectra. (8) Interference filters. These consist of alternate very thin films of, for exam le, magnesium fluoride and silver sandwiched between two lates of lass or between two 5' glass prisms (forming a cube). They are used as colour lters or or splitting a beam of light into two components. R k (9) Halftone or similar printing screens, generally round or rectangular (including square), of carefully olished glass (original screens for photogravure or process engram), cons~sting (i) two plates of lass, etched with very fine arallel lines, rendered opaque with a special % v m ~ s hwhic , are then stuck together so &t the lines are exactly at nght angles; or (ii) a single glass plate on which small hollows, usually square, have been etched and rendered opaque with a special varnish. Some of the optical elements listed above (lenses, prisms, etc.) may be coloured, or coated with an anti-reflectionfilm of cryolite, calcium or magnesium fluoride, etc. This does not affect their classification in this heading. The heading does not cover : (a) Cultured crystals, not being optical elements (generally heading 38.24). (b) Mirrors of heading 70.09, i.e., glass mirrors not optically worked. Simple plane or even curved mirrors (e-g., shaving mirrors and m o r s for powder compacts) are therefore classified in heading 70.09. (c) Optical eIements of glass of heading 70.14, i.e., elements not optically worked (generally moulded) (see Explanatory Note to heading 70.14). (d) Glasses of heading 70.15, not optically worked (e. ., blanks for contact lenses or for corrective spectacle lenses, for goggles, for protecting the dials o measuring instruments, etc.). ! (e) Mirrors, not constituting optical elements, of precious metal (Chapter 71), or of base metal (heading 83.06). (f) Connectors for optical fibres, optical fibre bundles or cables (heading 85.36). (g) Optical fibre cables made up of individually sheathed fibres (heading 85.44).