A pulse current component of a driving current is determined, based on a current-optical
output coefficient derived using average optical output information of a semiconductor
light-emitting element. A bias current component can be set by adjusting an average
optical output of the semiconductor light-emitting element while changing the bias
current component by the driving current including the determined pulse current
component. Since the current-optical output coefficient can be derived based on
the average optical output under wide conditions, both the pulse current component
and the bias current component can be determined under the wide conditions and
without using a quick-response light detector.
