| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that the image quality may be largely damaged because of occurrence of banding by spectrum components which appear in a low-frequency band when a plurality of light sources are used. SOLUTION: The image forming device is provided with an image processing device 4 which has a half tone processor for generating halftone image signals corresponding to an input image signal according to a dot pattern in a periodical structure composing a dot screen, and a scanning optical system 6 which scans and exposes a photoreceptor 7 by using several laser light sources 51-54. The dot screen is formed on condition that, when the number of light sources is N and the density of scanning lines in the vertical scanning direction is R (lines/ inch), the frequency components of the whole frequency spectrums which are produced by convoluting the frequency spectrum corresponding to the wave of R/N cycle in one and the other of the vertical scanning direction to the frequency spectrum obtained by Fourier transformation of the dot pattern is 100 (lines/inch) or more, or 0, and is 1/4 or more, or 0 of the frequency component of the dot pattern. |
