| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging lens system which is capable of focusing without changing a total length of an optical system and offers a wide view angle, a low F value, short total optical system length relative to an image height, compactness, a small distortion aberration, and high performance.SOLUTION: An imaging lens system comprises: a positive first lens group Gr1 having a positive lens with a convex surface on the object side and a negative lens with a concave surface on the imaging plane side; an aperture stop AP; a positive second lens group Gr2, whose most imaging plane side surface is convex, having a negative lens with a concave surface on the object side and two positive lenses with convex surfaces on the imaging plane side; and a negative third lens group Gr3 having a negative lens with a concave surface on the object side, arranged in order from the object side. Focusing is done by moving only the second lens group Gr2 along an optical axis without changing the total length of the optical system. A focal distance f1 of the Gr1, a focal distance f2 of the Gr2, a focal distance f3 of the Gr3, a focal distance f of the entire optical system, a distance L from a most object side surface of the Gr1 to the imaging plane, and a maximum image height Y' satisfy specific conditional expressions. |
