Method for setting quantity of light of light-emitting element array

摘要

A method for setting the amount of light in an array of light-emitting thyristors, each thyristor having I-L characteristic in which a luminous efficiency is decreased in a lower current field, is provided. According to the method, the amount of light emitted from a light-emitting thyristor is set so that a predetermined exposure energy may be obtained without decreasing a luminous efficiency of a light-emitting thyristor. The density D of a current to be supplied to the light-emitting thyristor to obtain a predetermined exposure energy is selected so as to satisfy the range of 3xDth<D<100 MA/m2, wherein Dth is a threshold current density for light emission which is defined as a current density corresponding to the value of a current at a point where a tangent drawn at the value of a current corresponding to a current density of 50 MA/m2 with respect to the curve of the I-L characteristic intersects a current axis.