Light quantity adjusting device and imaging apparatus

A light quantity adjusting device that adjusts a size of a diaphragm opening centered on an optical axis of an optical system, the light quantity adjusting device comprising:

• a first pair of rectilinear diaphragm blades configured to include a first rectilinear diaphragm blade and a second rectilinear diaphragm blade that are slidably arranged at positions opposing across the diaphragm opening in a direction moving closer to and separating from the optical axis on a plane orthogonal to the optical axis;
• a second pair of rectilinear diaphragm blades configured to include a third rectilinear diaphragm blade and a fourth rectilinear diaphragm blade that are centered on an axis parallel to the optical axis and are slidably arranged at positions opposing across the diaphragm opening in a direction orthogonal to a direction in which the first pair of rectilinear diaphragm blades move and in a direction moving closer to and separating from the optical axis;
• and
• a driving arm configured to be coupled to the first, the second, the third, and the fourth rectilinear diaphragm blades as the two pairs of rectilinear diaphragm blades and to rotate about an axis different from the optical axis and parallel to the optical axis so as to slide the first, the second, the third, and the fourth rectilinear diaphragm blades and adjust a size of the diaphragm opening;
• a driving motor configured to drive the driving arm, wherein
• a rotation of the driving arm causes the first, the second, the third, and the fourth rectilinear diaphragm blades to adjustably form and maintain, as nearly similar shapes, a shape of an opening perimeter of the diaphragm opening.