PURPOSE: To remove effectively flare light in a light emitting wave length of an LED, and reduce crosstalk when it is arrayed by arranging a dye layer on a side surface so as to absorb light having a specific wave length.
CONSTITUTION: In a light transmitting body having a radius (r) and a circular cross section, the refractive index distribution within range of 0.3r to 0.7r has the refractive index distribution almost approximate to a quadratic curve regulated by an expression toward an outer peripheral surface from the center axis. A layer composed of light absorbing dye capable of cutting off effectively light of 630 to 850nm, is arranged on the outer periphery of the light transmitting body having a characteristic value of (1.4≤n0≤1.6, 0.2mm≤r≤0.6mm and 0.15mm-1≤G≤0.7mm-1). It has also a characteristic value of which an MTF value measured by forming a grid image of four line pair/mm on a CCD line sensor through the light transmitting body becomes 70% or more. In the expression, (n0) represents a refractive index of a center axis part of a primary body of the light transmitting body, and n(r) represents a refractive index of a position part of a radius (r) on the center axis side of the primary body of the light transmitting body, and G represents a refractive index distribution constant of the primary body of the light transmitting body, and (r) represents a distance (mm) on the center axis side of the primary body of the light transmitting body.
IEDA YOSHIHIRO