Banding Reduction in an Electrophotographic Printer

摘要

Banding is an image artifact that appears as light and dark bands periodically across a page. Banding can be classified into two categories: fine and rough. A fine banding artifact could be caused by the periodic vibration or motion of optical devices in the optical path with the excitation frequency of the polygon mirror motor. This periodic vibration is mainly related to excitation force due to an imbalance of the rotor part of the polygon mirror motor or structural weakness of laser scanning unit. It is mainly caused by pyramidal errors of the polygon mirror motor. A rough banding artifact in printed images could be caused by the inaccurate motion or vibration of the organic photoconductor (OPC) part or the fusing part of the engine driven by the main driving unit. Printed image patterns have several frequencies, which can be obtained from the position of dots in a specific pattern in a printed image and Fast Fourier Transform (FFT) analysis of the position data. The identified frequencies can be confirmed by referring to the tooth frequencies of the parts on the gearing table. This article proposes a secure way to identify the causes of banding from FFT of the measured position data of dots in a specific pattern of printed images. The experiments were conducted to verify the identified causes of bandings.