Telecentric lens system and vision measuring instrument

摘要

A telecentric lens optical system includes: a front lens group; a rear lens group having a front focal point coinciding with a rear focal point of the front lens unit; and diaphragm mechanisms, each of which is disposed at a position where the rear focal point of the front lens unit and the front focal point of the rear lens unit coincide with each other. One of the front lens group and the rear lens group is provided by a plurality of variable magnification lens groups. The diaphragm mechanisms are provided corresponding to the variable magnification lens groups, respectively. A magnification switching mechanism is provided to selectively move a pair of one of the variable lens groups and one of the corresponding diaphragm mechanisms to be disposed on an optical axis of the other of the front lens group and the rear lens group.