| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system in which chromatic aberrations can be excellently corrected and in which variation in the chromatic aberration is small, which thereby maintains high optical performance in spite of environmental changes. SOLUTION: The optical system includes: a plurality of optical elements each having refractive surfaces located in a light incident side and a light exit side; and an aperture stop. When an extraordinary partial dispersion ratio on a g-line and an F-line is defined asΔθgF, the optical element satisfying 0.0272<¾ΔθgF¾ is set as an l-th optical element and the optical element satisfying ¾ΔθgF¾<0.0272 is set as an r-th optical element, and a focal length, an Abbe number of a material, and the extraordinary partial dispersion ratio of each of the l-th optical element and the r-th optical element which are arranged on either the object side or the image side from the aperture stop are suitably set. COPYRIGHT: (C)2010,JPO&INPIT
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