Patent ID: 8294755

Claim:
A light source apparatus including a light source and a light quantity adjusting portion for limiting light flux from the light source using an aperture blade, the light quantity adjusting portion comprising: the aperture blade configured to be driven to rotate in a vertical plane about a pivot and has a center of gravity, the center of gravity being decentered from the pivot; a position detecting portion for detecting a position of the aperture blade; a driving portion for driving the aperture blade to rotate; and a controlling portion for controlling the driving portion, wherein the controlling portion controls the driving portion based on the position of the aperture blade detected by the position detecting portion and a rotation direction wherein the controlling portion is configured to perform the control such that a speed of movement is constant independently of the rotation direction and the position of the aperture blade, using a correction coefficient based on a rotation direction component of self-weight of the aperture blade.