Improvement of imaging characteristics by pupil apodization in a laser scanning system for electro-photography

It is well known that imaging characteristics such as beam spot size and focal depth can be improved by applying apodization of amplitude and phase at the entrance pupil of an optical system. As an optical system for the electro-photography continuously requires highly resolved dot image and extended focal length to obtain more delicate expression with adequate production stability. Advantages from apodization technique can improve system performance and supply high degree of reliability of the optical system. However, issues on reduction in absolute optical power and on side-lobe of beam spot profile have been technical barrier for its useful implementation to imaging optics for commercial devices. Thorough this paper, theoretical feasibility of application of a pupil apodization to a laser scanning optical unit is mainly discussed in the aspects of optical power reduction and side-lobe of spot profile, as well as enhancement of optical resolution and focal depth. In addition, fundamental experimental results on beam spot profile through focal region are followed to uphold feasibility analysis.