Patent ID: 8384996

Claim:
A double-lens imaging optical system comprising: a meniscus concave lens; and a convex lens having a diffraction grating provided thereon, wherein the double-lens imaging optical system satisfies the following expression (1): 4.5 <P 1=(1 −f/f a )· v d <9.0 (1), where f is an effective focal length of the double-lens imaging optical system; f a is an effective focal length of the double-lens imaging optical system excluding the diffraction grating; and v d is an Abbe number of a material of the convex lens with respect to the d-line, wherein, an angle of view is 145° or more; the meniscus concave lens satisfies the following expression (4): 2.8 <P 2=( Cl 1 /Cl 2 )− n d1 <4.5 (4), where Cl 1 is an effective radius of an imaging target-side surface of the meniscus concave lens; Cl 2 is an effective radius of an image-side surface of the meniscus concave lens; and n d1 is a refractive index of the meniscus concave lens with respect to the d-line.