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

摘要

There is provided a lens formed from a circular bottom face (11), lateral face (14) and top face (15) and having a surface light source (13) of a finite size disposed at the center of the bottom face (11). The top face (15) is an aspheric surface rotational symmetric with respect to a z-axis and which totally reflects a part of a component, whose polar angle is smaller than a polar angle ˜ 0 at the intersection between the lateral face (14) and top face (15), of light emitted from the surface light source (13). The lateral face (14) is an aspheric surface rotational symmetric with respect to the z-axis and pervious to a component, whose polar angle is larger than the polar angle ˜ 0 , and component, totally reflected at the top face (15), of the light emitted from the surface light source (13). A function r = f s (z) where z is a variable representing the lateral face (14) increases monotonously as the variable z decreases in a closed zone defined by 0 ‰ z ‰ z 1 (z-coordinate of an intersection between the lateral face (14) and top face (15)), and has at least one point where a absolute value |d 2 r/dz 2 | is maximum in the closed zone.