Abstracts Category : Other

Laser printer scan lenses with diffractiveoptics

by Kevin Joseph McIntyre

The primary objective of this research is toestablish a role for diffractive optics in the design andfabrication of laser printer scan lenses. Virtually all ofthe laserprinter systems in the world today use either a toroidal lens orcylindrical field mirror to provide the necessary field curvaturecorrection. We have discovered a new class of scan lenses that doesnot require the use of either ofthese optical components. In ournew designs these complex elements are replaced with a singlerotationally-symmetric diffractive surface allowing for compacttwo-element lenses. The diffractive surface also plays a role incorrecting chromatic aberration in order to accommodate laser diodespectral variation. We demonstrate the validity of these designs byfabricating and testing a prototype scan lens suitable for use in a600 dpi laser printer. This prototype makes use of a new hybriddiode collimating lens. Experimental results reveal excellentcorrelation with theory. In addition to the diffractive designs, wehave found a similar class of designs based onrotationally-symmetric refractive aspheric surfaces. </br>A first-order theory for the design of scanlenses is established and includes an analysis of chromaticaberration correction. Several new design equations, that includethe effects of adding diffractive power, are derived. A review ofcritical design issues associated with polygon scanners ispresented including facet translation, polygon wobble, Gaussianbeam modeling, and field curvature correction. We present a new setof polygon design equations that does not require approximations. </br>The use of cascaded diffractive lenses isexamined for systems with multiple narrowband sources. We derive ageneral design rule for cascading diffractive surfaces and providea description of first-order imaging properties. Calculation ofdiffraction efficiency is also described. We propose using cascadeddiffractive lenses for color laser printer systems. Severalfirst-order design examples are provided.