2-D straight-scan on imaging surface with a raster polygon

A method of constructing a two-dimensional scanning system that includes an imaging surface, multiple light sources configured to generate multiple light beams, each beam for illuminating a distinct portion of the imaging surface and the multiple light beams together imaging a two-dimensional portion of the imaging surface, and a rotatable polygon mirror positioned in an optical path between the multiple light sources and the imaging surface to direct the multiple light beams to the imaging surface, the method comprising:

• determining pin-cushion scan-line distortion of multiple scan lines followed by the multiple light beams across the imaging surface as the rotatable polygon mirror rotates;
• and
• positioning a scan lens in an optical path between the rotatable polygon mirror and the imaging surface;
• wherein the scan lens is configured to introduce barrel scan-line distortion of the multiple scan lines that compensates for the pin-cushion scan-line distortion of the multiple scan lines such that the multiple scan lines are substantially straight and parallel lines on the imaging surface, and wherein the scan lens is configured to compensate for the pin-cushion distortion using only spherical lens elements;
• wherein the rotatable raster polygon mirror has multiple reflective facets that are each inclined at a different angle with respect to a rotational axis of the rotatable polygon mirror;
• wherein the rotational axis of the rotational raster polygon is inclined toward the scan lens;
• wherein a first approach angle of the multiple light beams is selected to position a convergence point of the multiple laser beams proximate a reflective facet of the rotatable raster polygon, a second approach angle being the angle formed between the multiple light beams approaching the rotatable raster polygon and the optical axis of the scan lens;
• wherein determining a magnitude of the second approach angle is based on a height of the imaging surface, a width of the multiple light beams, and a pupil distance;
• wherein selecting an angle of the inclined rotational axis of the rotational raster polygon scanner is based on the second approach angle and the pupil distance between the rotational raster polygon scanner and the scan lens;
• wherein the angle of the inclined rotational axis of the rotational raster polygon scanner is selected so that a pin-cushion distortion pattern produced by multiple scan lines on the imaging surface is positioned symmetrically around a centerline of the imaging surface;
• wherein a centerline of the multiple light beams is substantially aligned with the centerline of the imaging surface;
• wherein the multiple light beams reflected from a first facet of the rotatable raster polygon is along a first optical path through a first portion of the scan lens at a first incident angle and are incident on the imaging surface at a first vertical position;
• and
• wherein the multiple light beams reflected from a second facet of the rotatable raster polygon is along a second optical path through a second portion of the scan lens at a second incident angle different from the first incident angle and are incident on the imaging surface at a second vertical position different from the first vertical position.