| 摘要 |
PURPOSE:To make images formed on forms for respective copies accurately constant in magnification by varying a polygon mirror rotating speed and a modulation frequency according to the expansion/contraction rate of a form passing through a fixing device. CONSTITUTION:The expansion/contraction rate of the form having passed through the fixing device depends upon the relation between the stripe direction and conveying direction of a fiber and can be confirmed experimentally in advance. The magnification of a laser beam optical device 20 in the axial direction of a photosensitive drum is varied according to the modulation frequency fo of a laser diode 21 and the magnification in the rotating direction of the photosensitive drum is varied according to the rotating speed fr of a polygon mirror 23. For the purpose, the expansion/contraction rates in the long-side and short-side directions of the form which are obtained previously are stored in a storage means to vary the polygon mirror rotating speed fr and modulation frequency fo automatically according to the stored elongation/contraction rate values when an image is formed on the same form for 2nd and succeeding times, thus forming the image. |
