Patent ID: 8038357

Claim:
A diaphragm unit comprising: a plate-like base member having an optical path hole formed therein; a plurality of diaphragm blades overlapping with each other in an optical axis direction of an optical system, being supported by the base member so as to be movable in directions in which the diaphragm blades approach and depart from the optical axis along a plane perpendicular to the optical axis, and forming a diaphragm opening centered on the optical axis inside the optical path hole; and a driving mechanism adjusting the size of the diaphragm opening by moving the plurality of diaphragm blades, wherein the driving mechanism includes an annular plate disposed on the surface of the base member close to the plurality of diaphragm blades so as to be rotatable about the optical axis, a plurality of driving pins protruding from the annular plate to correspond to the plurality of diaphragm blades, a cam groove which is formed in each of the plurality of diaphragm blades and which engages with the corresponding driving pin, and a motor rotating the annular plate, wherein a partition plate having an optical path hole formed therein and separating the annular plate and the plurality of diaphragm blades from each other is disposed between the annular plate and the plurality of diaphragm blades, wherein the partition plate is formed of a steel plate and includes insertion portions into which the driving pins are loosely inserted and a plurality of rails which protrudes to the diaphragm blades and comes in contact with the diaphragm blades to guide movement of the diaphragm blades, wherein the diaphragm blades include a pair of straight-moving diaphragm blades disposed so as to be linearly movable in the directions in which the diaphragm blades approach and depart from the optical axis and a pair of swing diaphragm blades disposed so as to swing in the directions in which the diaphragm blades approach and depart from the optical axis, wherein the rails formed in the partition plate are rails guiding one of the pair of swing diaphragm blades and one of the pair of straight-moving diaphragm blades, and wherein rails coming in contact with the other of the pair of swing diaphragm blades and the other of the pair of straight-moving diaphragm blades and guiding the movements of the diaphragm blades are formed in a cover member.