LIGHT SOURCE UNIT AND IMAGE FORMING APPARATUS USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a light source unit configured to maintain peak intensity of a main lobe at a high value before and after a focal position on an optical axis.SOLUTION: A light source unit 1 includes: a laser beam source 11 which emits a laser beam; a phase modulation region where a part of a wavefront of the laser beam is made incident; and a non-phase modulation region where the other part of the wavefront is made incident. In the phase modulation region, a phase optical element 14 for modulating a phase of the laser beam and an imaging optical system 15 for imaging the light passing through the phase optical element 14 in a focal position are provided. The phase optical element 14 has surface patterns of a first region and a second region set so that peak intensity of a main lobe in a light intensity profile in a focal point F is smaller than or equal to peak intensity of the main lobe in the light intensity profile in a non-focal position apart from the focal position by a predetermined distance in an optical axis AX direction.