Patent attributes
An imaging optical system, including an imaging lens group, an image side prism having an entrance surface a reflection surface and an exit surface from which light exits toward an image pickup device, and a first shielding member shielding at least a part of a region on the entrance surface, wherein the region on the entrance surface is located from an edge line of an apex between the entrance surface and the exit surface to a position corresponding to a height h from the edge line, and when L represents a length of the exit surface, α represents an angle formed between the reflection surface and the exit surface, n represents a refractive index of a surrounding area of the image side prism, and n′ represents a refractive index of the image side prism, the height h satisfies a following condition: h=L×cos {α+sin−1(n/n′)}.
