| 摘要 |
1,225,999. Colour correction filters. LIBBEY-OWENS-FORD Co. Aug. 19, 1968 [Aug. 30, 1967], No.39552/68. Heading G2J. A colour correction light transmitting filter comprising a transparent substrate to a major surface of which is applied a multi-layer coating for altering the apparent colour temperature of an incandescent light source from 3200‹K. to 5500‹K., consists essentially of alternate layers of high and low index of refraction materials of one-quarter wave optical thickness for 650mu light with the first and last layers being of the high index material and a final layer of a low index of refraction material applied to the last layer of high index material at an optical thickness of one-quarter wavelength for 450mu light. The incandescent light source may a tungsten-iodine lamp 12 enclosed in a housing 10 having a reflective backing and an opening closed by a double-convex lens 16 to the outer surface of which is applied the multi-layer coating (e.g. 6 or 10 layers). The lens may be replaced by a flat transparent heat-resistant plate having the multi-layer coating on its inner surface. The high index of refraction layers 27 may be a metallic oxide or sulphide (e.g. alluminium oxide, titanium dioxide, zirconium dioxide, zinc sulphide, antimony tri-sulphide) and the low index of refraction layers 28 and 29 may be magnesium fluoride, quartz or cryolite for example. The filter is constructed to have a spectral transmission in excess of 90% at 450mu with about 20% transmission at 625mu. |
