Patent ID: 7922404

Claim:
A diaphragm unit comprising: a pair of straight-moving diaphragm blades and a pair of swing diaphragm blades overlapping with each other in an optical axis direction of an optical system and forming a diaphragm opening centered on the optical axis by moving in directions in which the diaphragm blades get close to and apart from the optical axis along a plane perpendicular to the optical axis; a receiving member receiving the pair of straight-moving diaphragm blades and the pair of swing diaphragm blades; and a diaphragm driving mechanism adjusting the size of the diaphragm opening by moving the diaphragm blades, wherein the receiving member has a pair of side surfaces facing each other in the optical axis direction, wherein one of the pair of straight-moving diaphragm blades and one of the pair of swing diaphragm blades are disposed on one of the pair of side surfaces, wherein the other of the pair of straight-moving diaphragm blades and the other of the pair of swing diaphragm blades are disposed on the other of the pair of side surfaces, and wherein a concave portion which is concave toward the other of the pair of side surfaces is disposed on one of the pair of side surfaces outside the moving locus of one of the pair of straight-moving diaphragm blades and one of the pair of swing diaphragm blades in a state where a space is secured in the optical axis direction between the other of the pair of straight-moving diaphragm blades and the other of the pair of swing diaphragm blades.