| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging optical system in which various aberrations including a chromatic aberration can be easily corrected and reduction in size of the whole system and reduction in weight of a lens can be achieved.SOLUTION: The following factors are each appropriately determined: a focal length fof a first lens group; a lens total length L; a focal length f of the whole system; an F number Fn; an absolute value dof the distance on an optical axis from an aperture diaphragm to a lens surface top of a lens unit St; a refractive power φ, an Abbe number νon a d-line basis, and an abnormal partial dispersion ratio Δθof each lens constituting the lens unit St; a refractive power φof each lens located closer to an object than the lens unit St; and an Abbe number νon a di-line basis and an abnormal partial dispersion ratio Δθof each lens located closer to the object than the lens unit St.SELECTED DRAWING: Figure 1 |
