Color separating optical system and image pickup apparatus including the same

Abstract

A color separating optical system includes a first prism including a second surface for separating an beam into reflected and transmitted beams; and a second prism including a third surface disposed to have an air gap interposed between the third and second surfaces and a fourth surface for separating a beam from the third surface into reflected and transmitted beams. At least one of the second and third surfaces has a multi-layer film, and 0.70<nd×cos θ2A/(λ/4)<1.2 is satisfied, where θ2A=sin{(Ng/Nm)sin(θ2)}, λ central wavelength in a wavelength range of the beam to be separated by the second prism, nd thickness of an outermost layer of the multi-layer film, Nm refractive index of the outermost layer for the central wavelength, Ng refractive index of a glass material of the second prism for the central wavelength in the wavelength range of color light to be separated, and θ2 apex angle of the second prism.