| 摘要 |
PROBLEM TO BE SOLVED: To obtain a multi-beam scanning optical device capable of compacting an optical system for synchronism detection and enhancing the precision of synchronism detection by preventing spatial overlap of plural spots, and to provide an image forming device using the optical device. SOLUTION: Images of plural luminous fluxes which are independently optically modulated and emitted from a light source having plural light emission points which are arranged apart from each other in the main scanning direction are formed on a scan object surface through deflecting elements by scanning optical elements to scan the scan object surface with plural luminous fluxes, and a part of plural luminous fluxes which have passed deflecting elements is converged into a spot in a synchronous detection position and is transmitted onto a synchronism detection element surface; and when a signal from a synchronism detection element is used to control the timing of the scanning start position on the scan object surface for every plural luminous fluxes, spot intervals in the main scanning direction between adjacent luminous fluxes in the synchronism detection position is made shorter than that on the scan object surface.
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