ORIGINAL READING LENS, ORIGINAL READING LENS UNIT, ORIGINAL READING MODULE, ORIGINAL READING METHOD, ORIGINAL READER, AND IMAGE INFORMATION PROCESSOR

摘要

PROBLEM TO BE SOLVED: To provide an original reading lens consisting of the smaller number of lenses, namely, three to five lenses, as compared with a Gaussian type and having performance equivalent to or higher than the Gaussian type. SOLUTION: The lens for reading out an original image is constituted of a front group GF arranged on the object side ad a rear group GR arranged on the image side, the front group GF is constituted of two to four lenses including one or more positive lenses and the rear group GR is constituted of a negative lens. Back focus B in a real using state is <=30% of the whole lens length A and an air interval C between the front group GF and the rear group GR is >=50% of the whole lens length.