Patent ID: 7990616

Claim:
An optical multilayer film filter having an inorganic thin film composed of a plurality of layers on a substrate, comprising: the inorganic thin film being constituted by a low-density formation section and a high-density formation section; a fluorinated organic silicon compound film being formed on a surface of the inorganic thin film; the low-density formation section being formed such that one of a most superficial layer of the inorganic thin film and a plurality of layers including the most superficial layer is formed of at least one of a low-density titanium oxide layer and a low-density silicon oxide layer; the high-density formation section being formed between the low-density formation section and the substrate by stacking silicon oxide layers with a density higher than the low-density silicon oxide and titanium oxide layers with a density higher than the low-density titanium oxide layer; a total film thickness of the low-density formation section being within 280 nm; density of the low-density silicon oxide layer being in a range of 1.9 through 2.1 g/cm 3 ; density of the low-density titanium oxide layer being in a range of 4.1 through 4.8 g/cm 3 ; the most superficial layer of the inorganic thin film being formed of the low-density silicon oxide layer; and the number of layers of the low-density formation section being formed by selecting one of two through four.