Patent ID: 8259395

Claim:
An erect life-size lens array comprising: a first lens array in which plural first lenses each having a convex incidence surface and a convex exit surface are arranged in a direction orthogonal to an optical axis; a second lens array in which plural second lenses each having a convex incidence surface and a convex exit surface are arranged to correspond to the plural first lenses in the direction orthogonal to the optical axis and on which a light beam emitted from the exit surface of each lens in the first lens array is incident; and an aperture which includes plural circular holes corresponding to the plural first lenses and the plural second lenses and is disposed in a vicinity of at least one of the exit surface of the first lens array and the incidence surface of the second lens array between the first lens array and the second lens array, wherein when a thickness of the second lens is ξ 1 , a refractive index of the second lens is n, a distance between the exit surface of the second lens and a design image surface is ξ 2 , a radius of the circular hole of the aperture is r a , and a defocus amount is ξ 3 , the erect life-size lens array is for causing an MTF at a spatial frequency (line-pair/mm) ν to become MTF target or more, and satisfies (J 1 (2π·r a ·((n/ξ 1 )+(1/ξ 2 ))·ν·ξ 3 ))/(π·r a ·((n/ξ 1 )+(1/ξ 2 ))·ν·ξ 3 )≧MTF target , where J 1 is a first type first-order Bessel function.