Patent ID: 7959291

Claim:
A telecentric lens system comprising: a front lens group; a rear lens group having a front focal point coinciding with a rear focal point of the front lens group; and diaphragm mechanisms, each of which is disposed at a position where the rear focal point of the front lens group coincides with the front focal point of the rear lens group, wherein one of the front lens group and the rear lens group includes a plurality of variable magnification lens groups, the diaphragm mechanisms are provided corresponding to the plurality of variable magnification lens groups, respectively, and a magnification switching mechanism is provided to selectively move a pair of one of the plurality of variable magnification 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, wherein the magnification switching mechanism includes a slide plate, a guide mechanism that supports the slide plate to be slidable in a direction approximately orthogonal to the optical axis of the other of the front lens group and the rear lens group, and a magnification switching unit for sliding the slide plate, a plurality of pairs of the variable magnification lens groups and the corresponding diaphragm mechanisms are arranged in the sliding direction of the slide plate, each of the diaphragm mechanisms includes a numerical aperture changer including: a first diaphragm disposed on the optical axis of the other of the front lens group and the rear lens group; a swing lever having a middle portion supported to be swingable and an end supported to be retractable from a position of the first diaphragm; and a second diaphragm formed on the end of the swing lever and having a smaller diameter than a diameter of the first diaphragm, the numerical aperture changer changing a numerical aperture by switching the first diaphragm and the second diaphragm, a numerical aperture switching unit is provided to rotatably connect a base end of the swing lever of the diaphragm mechanisms and swing the swing lever thereof about a swinging supporting point, and the magnification switching unit and the numerical aperture switching unit are provided on the slide plate to protrude in directions parallel to the sliding direction of the slide plate, the directions being mutually in a same direction.