Patent attributes
An image pickup optical system includes, in order from the object side, a front unit having at least one reflecting surface with power that is rotationally asymmetrical, an aperture stop, and a rear unit having at least one reflecting surface with power that is rotationally asymmetrical. In this case, F-numbers in two directions perpendicular to each other on a plane perpendicular to the optical axis are different. Decentration takes place in one of the two directions and the F-number in a direction perpendicular to a decentering direction is smaller than that in the decentering direction. When the F-number in the decentering direction is represented by FNY and the F-number in the direction perpendicular to the decentering direction is represented by FNX, the optical system satisfies the following condition:1.1<FNY/FNX<2.0.
