| 摘要 |
1,265,831. Optical filters. EASTMAN KODAK CO. Feb. 27, 1969 [March 4, 1968], No.10481/69. Heading G2J. [Also in Division C7] An optical filter, particularly for use in sunglasses, comprises a gold or copper foil 12 sandwiched between two transparent layers 14, 16, to filter I.R. and U.V. radiation from one side of the filter, and a metal, semi-metal or alloy layer 18, having a complex refractive index whose real part is within a factor of 10 of its imaginary part, to reduce reflection from the other side of the filter. The various layers 12, 14, 16 and 18 are successively deposited on a plastics or glass substrate 20 by vacuum distillation, or in the case of the gold or copper foil by cathodic sputtering, electrolysis or chemical methods. The order of deposition may be reversed, Fig. (not shown) and a protective plastics or glass layer may be provided at the side remote from the substrate, Figs.5 and 6 (not shown). The layers 14, 16 may consist of the oxides of titanium, lead or bismuth or zinc sulphide, and the layer 18 may be constituted by Ni, Fe, Cr, Ti, Al, La, In, Sn, Pb, Ta, W, Co, Mo, Os, Ir, Pt, Yt, Zr, Ni, Zn, Cd, V, Hf, Re, Tl, Si, Ge, As, Sb, or Te or an alloy or any two or more thereof.
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