IMAGING LENS

PROBLEM TO BE SOLVED: To provide an imaging lens that has good optical characteristics, is composed of compact two lenses having narrow angles of view, and is used for biometric authentication such as iris authentication in a wavelength region of 750-900 nm.SOLUTION: An imaging lens used for biometric authentication includes a first lens having positive power and a second lens having negative power that are arranged in order from an object side, and satisfies a predetermined conditional expression: -0.92≤f1/f2≤-0.68 (1), 0.10≤d1/f≤0.20 (2), 0.24≤d2/f≤0.50 (3), -3.50≤(R1+R2)/(R1-R2)≤-1.80 (4), where f represents a focal length of an entire lens system, f1 represents a focal length of the first lens, f2 represents a focal length of the second lens, d1 represents a center thickness of the first lens, d2 represents an axial length from an image surface side surface of the first lens to an object side surface of the second lens, R1 represents a curvature radius of an object side surface of the first lens, and R2 represents a curvature radius of the image surface side surface of the first lens.SELECTED DRAWING: Figure 1 【課題】良好な光学特性を有し、小型で画角が狭角な２枚のレンズで構成され、７５０ｎｍ〜９００ｎｍの波長域での虹彩認証等の生体認証に用いられる撮像レンズを提供する。【解決手段】生体認証に用いられる撮像レンズは、物体から順に、正パワーの第１レンズ、負パワーの第２レンズが配置されており、所定の条件式を満足する。−０．９２≦ｆ１／ｆ２≦−０．６８（１）０．１０≦ｄ１／ｆ≦０．２０ （２）０．２４≦ｄ２／ｆ≦０．５０ （３）−３．５０≦（Ｒ１＋Ｒ２）／（Ｒ１−Ｒ２）≦−１．８０ （４）但し、ｆ：レンズ系全体の焦点距離；ｆ１：第１レンズの焦点距離；ｆ２：第２レンズの焦点距離；ｄ１：第１レンズの中心厚；ｄ２：第１レンズ像面側面から第２レンズの物体側面までの軸上距離；Ｒ１：第１レンズの物体側面の曲率半径；Ｒ２：第１レンズの像面側面の曲率半径【選択図】図１