| 摘要 |
An optical information recording/reproducing optical system, comprising a light source; an optical element converting a laser beam into a substantially collimated beam; and an objective lens, wherein a wavelength λ (unit: nm) of the laser beam falls within a range of 400<λ<410, the optical element and the objective lens are made of same resin materials or different resin materials having a glass transition temperature of Tg>115° C., each of optical surfaces is configured not to have an optical thin film which contains at least one of or elements of titanium, tantalum, hafnium, zirconium, niobium, molybdenum and chromium, each of optical surfaces of the optical element is provided with an antireflection film made of one of or a mixture of at least two of silicon oxide, aluminum oxide, aluminum fluoride and magnesium fluoride, and a following condition is satisfied. ∏ i = 1 n - 1 ( 1 - R ( BL ) i 100 ) - ∏ i = 1 n - 1 ( 1 - R ( UV ) i 100 ) > 0.05 .
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