Patent ID: 8559112

Claim:
A method comprising: forming an aspherical optical surface of an optical element by a press molding method, wherein the optical element is made of a glass containing at least one of an alkali metal and an alkali earth metal; forming a film on the aspherical optical surface by a sol-gel process, wherein the film is made of a material containing at least one of an aluminum or an aluminum oxide; and forming an antireflection structure including a minute uneven structure on the aspherical optical surface by immerging the film into warm water having temperature of between 40° C. and 100° C., wherein the minute uneven structure has an average pitch of 400 nm or less, and wherein the optical element is made of a glass having a refractive index of 1.583, a refractive index dispersion of 59.4 and transition point of 506° C.