OPTICAL SYSTEM INCLUDING DIFFRACTIVE OPTICAL ELEMENT AND OPTICAL APPARATUS

摘要

The optical system includes, in order from an object side, a front lens unit LF, an aperture stop S, a rear lens unit LR. The front lens unit includes a diffraction optical element Ldoe. A stop side positive lens Lsp disposed closest to the aperture stop among the rear lens unit satisfies 1.55≦Ndsp≦1.70, 30.0≦νdsp≦50.0, and 5.0×10−4≦ΔθdCsp≦5.0×10−3. Ndsp and νdsp repectively represent a refractive index and an Abbe number of the stop side positive lens for a d-line, and ΔθdCsp is represents a value defined by ΔθdCsp=θdCsp−(−0.17041×θgdsp+0.513577) where Ngsp, NCsp and NFsp respectively represent refractive indices of the stop side positive lens for a g-line, a C-line and an F-line. θdCsp and θgdsp are respectively defined by θdCsp=(Ndsp−NCsp)/(NFsp−NCsp) and θgdsp=(Ngsp−Ndsp)/(NFsp−NCsp).

主权项

1. An optical system comprising, in order from an object side to an image side:
a front lens unit; an aperture stop; and a rear lens unit, wherein: the front lens unit includes a diffractive optical element, the rear lens unit includes at least one positive lens, and among the at least one positive lens, a stop side positive lens disposed closest to the aperture stop is formed of an optical material satisfying the following conditions:
1.55≦Ndsp≦1.7030.0≦νdsp≦50.05.0×10−4≦ΔθdCsp≦5.0×10−3 where Ndsp and νdsp respectively represent a refractive index and an Abbe number of the optical material of the stop side positive lens for a d-line, and ΔθdCsp represents a value defined by
ΔθdCsp=θdCsp−(−0.17041×θgdsp+0.513577)where Ngsp, NCsp and NFsp respectively represent refractive indices of the optical material of the stop side positive lens for a g-line, a C-line and an F-line, and θdCsp and θgdsp are respectively defined by
θdCsp=(Ndsp−NCsp)/(NFsp−NCsp) and θgdsp=(Ngsp−Ndsp)/(NFsp−NCsp).