Variation of Angular Profile and Dividing Angle of the Polygon Mirror Caused by Scanning Beam Diameter.

This paper describes the influence of scanning beam diameter on the angular profile of a polygon mirror. The beam diameter is adjusted to φ2mm, φ3.5mm and φ5mm to obtain two-dimensional angular profile of the polygon mirror surface. The developed system was used to measure a 24-sided polygon mirror (face dimension : 15 X 20mm) and the following results were obtained : (1) The angular profile of the polygon mirror depends on the area of scanned cross section or the diameter of the scanning beam. (2) The difference of the accumulation error obtained by the developed system with the φ5mm beam from that with the conventional measurement method provided by JIS was about 1 s (arc) in RMS. (3) The maximum differences between the dividing error obtained by the developed system with the φ2mm, φ3.5mm and φ5mm beam and that with the conventional measurement method was about ±2.7, ±2.4, ±2.0s (arc) respectively. These results suggest that the conventional measurement method is not robust enough to estimate the accuracy of polygon mirror to be used with a scanning beam having a small diameter.