A compact "double winged" laser diode (LD) optical system for use in a laser printeK for computer graphics scans a width of 515 mm using two beams and focuses an 80 um (1/e z) diameter spot to produce a resolution of 480 dpi over the entire width. The system was developed by using a scanning module which combines two preobjective scanning units with one polygon. The configuration of two preobjective scanning is symmetrical with respect to a single 12-facet polygon. Each preobjective scanning module includes a compact LD module, an f0 lens, and a flat mirror. The LD module consists of a laser diode, a collimating lens, and a beam-shaped prism. This system has two scanning beams and each beam scans a half recording width. The paper discusses how the left and right scanning images are apposed at the image center. This system features compactness, greater image width, higher resolution, and a reduced need for high-precision polygon fabrication.
Fumitaka Abe, Satoshi Itami, Tohru Satoh, Tadashi Matsuda, "Double Winged LD Beam Scanning System For Computer Graphics," Proc. SPIE 0457, Advances in Display Technology IV, (14 May 1984);