Variable focus lens for compact camera, with negative first lens group, positive second lens group and negative third lens group

摘要

Variable focus lens has negative first lens group (10), positive second lens group (20) and negative third lens group (30) in this sequence from object side. Distance between first and second lens groups, their focal lengths, resultant focal length and third lens group focal length fulfill specific conditions to ensure compact structure. Distance between negative first lens group (10) and positive second lens group (20), for short focus width, is arranged so entire length of variable focus lens is reduced. Focal length of first and second lens groups are arranged so amount of distance change on variable displacement between first and second lens groups is less. Resultant focal length of negative first lens group and positive second lens group is set so displacement amount is less. Focal length of negative third lens group (30) ensures less amount of displacement of negative third lens group.