Kenichi Kugai

Fabrication Of Nonaxisymmetric Aspheric Lenses For Laser Printers

A new fabrication technique for nonaxissymmetric aspheric glass lenses is developed. In a laser printer, a combination lens system consisting of spherical lenses and a long cylindrical lens is used for the F-e conversion system. However, the conventional F-e lens system has a large aberration characteristic In its wide beam scanning. Aberration-free characteristics can be achieved using a nonaxissymmetric aspheric surface on a normal toroidal lens. This configuration results in a surface similar to a toroidal figure, but with the short radius gradually varied along the main axis. However, this type of nonaxissymmetric lens is difficult to produce with the conventiona lapping method. To overcome this problem, a new numerically controlled aspheric surface generator is constructed. Pairs of glass blanks are set around a turntable that rotates continuously at about 4 rpm. The surfaces of the blanks are machined with a grinding wheel, while the grinding spindle swings to generate the short radius of a basic toroidal figure. Furthermore, the grinding depth is dynamically controlled by actuating the turntable position through linkage with the rotation angle of the turntable. With this figure-generating principle, pairs of lenses with arbitrary surfaces can be machined at the same time. A 115 mm x 16 mm modified toroidal lens with an aspheric length of 80 Am is machined. Machining time for a lens is 45 minutes, and a figure accuracy of ± 0. 2 P.M and a surface roughness of 0.05 (Lm Rmax are achieved.