| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a zoom lens system composed of three groups of lenses which are negative, positive, and positive with variable power ratio of about 4 to 5. <P>SOLUTION: The zoom lens system is composed of: a first lens group having negative refractive power; a second lens group having positive refractive power; and a third lens group having positive refractive power in this order from the object side. In this case, when varying power, a space between the first lens group and the second lens group is reduced, the first lens group or the third lens group is moved in the direction of the optical axis so that a space between the second lens group and the third lens group is increased and the following conditional expressions (1), (2) and (3) are satisfied. (1) d3Iw-d3Im>0 (2)0<(d3Iw-d3It)/ft<0.2 (3)(d12w+d23w)/ft<1.0 when d3Iw: a space between the third lens group of short focal distance end and an imaging surface, d3Im: a space between the third lens group of medium focal distance fm and the imaging surface, d3It: a space between the third lens group of long focal distance end and the imaging surface, d12w: a space between the first and second lens groups of short focal distance end, d23w: a space between the second and third lens groups of the short focal distance end, and ft: the focal distance of the total system of the long focal distance end. <P>COPYRIGHT: (C)2012,JPO&INPIT |
