Optical system and optical apparatus including optical system
AssigneeCanon Kabushiki Kaisha
InventorKaoru Eguchi
Life of this patent
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Abstract
Provided are an imaging optical system in which chromatic aberrations are excellently corrected across the entire screen to realize high optical performance, and an optical apparatus including the imaging optical system. In an imaging optical system of which a back focus is longer than a focal length, a lens unit located in a reduction-conjugate side of an aperture stop includes at least one positive lens. A partial dispersion ratio and an Abbe number of the positive lens are set such that a refractive index, a position, and a power satisfy a suitable relationship.
Claims10
An optical system, comprising:
- an aperture stop;
- and
- a first positive lens provided in a reduction-conjugate side of the aperture stop,
- wherein the following conditions are satisfied:
- 0.79<θgFR−(1.00×10−4×νdR2−9.10×10−3×νdR)<0.86,
- 10<νdR<30, and
- 0.5<fGR/f<1.9,
- where fGR indicates a focal length of the first positive lens, f indicates a focal length of the entire optical system, NgR, NFR, NdR, and NCR indicate refractive indices of the first positive lens with respect to a g-line, an F-line, a d-line, and a C-line, respectively, and θgFR and νdR indicate a partial dispersion ratio and an Abbe number of the first positive lens, respectively, and
- where νdR and θgFR are expressed as follows:
- νdR=(NdR−1)/(NFR−NCR)
- θgFR=(NgR−NFR)/(NFR−NCR)
An optical system comprising, in order from a magnifying-conjugate side, a first lens unit having a negative refractive power, and a rear group having one of a positive refractive power and a negative refractive power and including at least one lens unit, wherein each interval between lens units including the first lens unit and the at least one lens unit of the rear group is changed during zooming, the optical system further comprising:
- an aperture stop;
- and
- a first positive lens provided in the reduction-conjugate side of the aperture stop,
- wherein the following conditions are satisfied:
- 0.79<θgFz−(1.00×10−4×νdz2−9.10×10−3×νdz)<0.86,
- 10<νdz<30, and
- 0.5<fGz/√{square root over (fW×fT)}<1.9
- where fGz indicates a focal length of the first positive lens, fW indicates a focal length of the entire optical system at a wide angle end, fT indicates a focal length of the entire optical system at a telephoto end, Ngz, NFz, Ndz, and NCz indicate refractive indices of the first positive lens with respect to a g-line, an F-line, a d-line, and a C-line, respectively, and θgFz and νdz indicate a partial dispersion ratio and an Abbe number of the first positive lens, respectively, and
- where νdz and θgFz are expressed as follows:
- νdz=(Ndz−1)/(NFz−NCZ)
- θgFz=(Ngz−NFz)/(NFz−NCz).
Dependencies are inferred from the claim text.