To obtain an optical scanning device in which timing of a scanning start position
on a surface to be scanned (hereinafter referred to as object surface) is stabilized
and detection precision of a synchronous signal by a synchronous position detecting
unit is improved, with the result that an image with higher definition can be obtained.
The optical scanning device includes an aperture stop for limiting a light flux
width of a plurality of light fluxes, an optical deflector for deflecting the light
fluxes passing through the aperture stop, a scanning optical system for guiding
the plurality of light fluxes deflected by the optical deflector onto an object
surface, and a synchronous position detecting unit for detecting the plurality
of light fluxes deflected by the optical deflector to obtain the synchronous signal,
which includes a synchronous detection element, and in the optical scanning device,
the synchronous position detecting unit further includes an imaging element and
a synchronous position determining unit for determining a light flux position in
a main scanning direction on the synchronous detection element disposed in an imaging
position of the imaging element or vicinities thereof, and a conjugate point of
the imaging element with the synchronous position determining unit is set between
a deflection surface of the optical deflector and the aperture stop within a sub-scanning section.
