Patent ID: 6573921
Filing Date: 2003-06-03
Classification: B41J,G02B

Abstract:
An optical scanning device for optically scanning a surface of a photoconductor to form an electrostatic latent image thereupon, comprising:a light source including a semiconductor laser having an oscillating wavelength greater than 380 nm and smaller than 670 nm, said light source configured to emit a light flux and to pulse modulate the light flux by a pulse modulation method; a deflector configured to deflect the light flux from the light source; and a scanning image formation element configured to condense the light flux deflected by the deflector, to form a scanning beam spot on the scanned surface, and to scan the scanning beam spot across the scanned surface thereby to form the electrostatic latent image on the scanned surface, wherein the scanning image formation element configures the scanning beam spot such that a stationary beam spot, formed by stationary light flux on the scanned surface, has a stationary beam spot diameter &ohgr;m in a main scanning direction that is smaller than a stationary beam spot diameter &ohgr;s in a sub-scanning direction, the scanning beam spot on the scanned surface is configured to move substantially in the main scanning direction, and the diameter &ohgr;m and the diameter &ohgr;s satisfy a following formula, 0.9Ã—[(&ohgr;m{circumflex over ( )}2+D{circumflex over ( )}2)Ã—[{(&ohgr;m+D)/&ohgr;m}{circumflex over ( )}(&frac18;)]]s<1.1Ã—[(&ohgr;m{circumflex over ( )}2+D{circumflex over ( )}2)Ã—[{(&ohgr;m+D)/&ohgr;m}{circumflex over ( )}(&frac18;)]], where D=DoÃ—Duty/100, Do is a size of a picture element, and Duty is a duty percentage in pulse modulating the light flux at the light source.