| 摘要 |
PURPOSE:To improve light transmittance by specifying the refractive index of SiO which forms the 1st layer of plastic optical parts subjected to multi-coatings by using SiO at a specific value or above. CONSTITUTION:The surface of a plastic base material, for example, a styrene lens 4 is subjected to three-layered multi-coatings consisting of an SiO layer 5 having an optical film thickness lambda0/4, a ZrO2 layer 6 having an optical film thickness lambda0/2 and an MgF2 layer 7 having an optical film thickness lambda0/4 and the transmittances of light with respective wavelengths when the refractive indices of SiO are specified respectively at 1.70, 1.60, 1.56, 1.50 give respectively curves 61-64. These curves reveal that an extremely good transmission characteristic of >=99% is obtainable by specifying the refractive index of SiO at >=1.55. Since the refractive index of polycarbonate is 1.58 in the case of a polycarbonate lens, roughly the same result as in the case of the styrene lens is obtd. and the good transmission characteristic is obtainable when the refractive index of SiO is 1.55. |
