LIGHT PICKUP LENS, LIGHT EMITTING ELEMENT ASSEMBLY, SURFACE LIGHT SOURCE DEVICE, AND COLOR LIQUID CRYSTAL DISPLAY UNIT ASSEMBLY

摘要

A light pickup lens having a surface light source (13) having a finite size disposed at the center of a bottom surface (11), wherein a top surface (15) consists of an aspherical surface that is used to totally reflecting part of a radiation light component having a polar angle smaller than an polar angle T₀ at the intersection between a side surface (14) and the top surface (15) and is rotary-symmetrical with respect to z-axis, and the side surface (14) consists of an aspherical surface that is used to transmit a radiation light component having a polar angle larger than an polar angle T₀ and a radiation light component totally reflected by the top surface (15) and is rotary-symmetric with respect to z-axis, and has, in a function r=f_S(z) with z representing the side surface (14) being as a variable, at least one point at which the function r=f_S(z) increases monotonously when z decreases in a closed interval of 0=z=z₁ (the z coordinate of a portion where the side surface (14) and the top surface (15) cross each other), and at which |d²r/dz²| is maximal in the closed interval.