Patent ID: 7864453

Claim:
An optical system, comprising: a plurality of optical elements each having refractive surfaces located on a light incident side and a light exit side; and an aperture stop, wherein letting an l-th optical element be an optical element of the plurality of optical elements which satisfies 0.0272<|Î”Î¸gF|, and letting an r-th optical element be an optical element which satisfies |Î”Î¸gF|<0.0272, where Î”Î¸gF represents an extraordinary partial dispersion ratio with respect to a g-line and an F-line, the l-th optical element and the r-th optical element are located in one of an object side and an image side with respect to the aperture stop, wherein, for the l-th optical element, letting an i-th optical element (where i=1, 2, . . . , m) be an optical element located at an i-th position from the light incident side; and, for the r-th optical element, letting a j-th optical element (where j=1, 2, . . . , n) be an optical element located at a j-th position from the light incident side, the following conditions are satisfied: Î£(1 /fnr j )/Î£(1 /fnl i )<0 5.0<|Î£((Î”Î¸gFnl i /Î½dnl i )/ fnl i )/Î£((Î”Î¸ gFnr j /Î½dnr j )/ fnr j )| where fnl i indicates a focal length of the i-th optical element, Î½dnl i indicates an Abbe number of a material of the i-th optical element, Î”Î¸gFnl i indicates an extraordinary partial dispersion ratio with respect to the g-line and the F-line in the i-th optical element, fnr j indicates a focal length of the j-th optical element, Î½dnr j indicates an Abbe number of a material of the j-th optical element, and Î”Î¸gFnr j indicates an extraordinary partial dispersion ratio with respect to the g-line and the F-line in the j-th optical element.