| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact imaging optical system in which color aberration on and outside an axis is suppressed and a curved field and various aberrations such as distortion are excellently corrected, regardless of the fact that an angle is wider and an aperture is larger than those of a conventional imaging optical system. SOLUTION: The imaging optical system comprises a first lens group G1 having positive refractive power, a diaphragm S, a second lens group G2 having positive refractive power and a third lens group G3 having negative refractive power in order from an object side. The first lens group G1 includes a cemented lens comprising a first lens L1 and a second lens L2, the second lens group G2 includes a third lens L3 and the third lens group G3 includes a fourth lens L4. The object side surface of the third lens L3 is concave to the object side on and outside the axis, the image side surface of the third lens L3 is convex to the object side on the axis and the third lens L3 has an aspherical surface having one or more inflection points outside the axis. COPYRIGHT: (C)2010,JPO&INPIT |
