In a light scanning optical system having a first optical system for causing a
beam emitted from light source means to be incident on the deflecting surface of
a light deflector at a predetermined angle in the sub-scanning cross-section, and
a second optical system for imaging the beam reflected and deflected by the light
deflector on a surface to be scanned and bringing the deflecting surface of the
light deflector and the surface to be scanned into a substantially conjugate relation
in the sub-scanning cross-section, when the maximum value and minimum value of
the peak intensity in the effective scanning area of a spot imaged on the surface
to be scanned by the second optical system are defined as EMAX and EMIN,
respectively, to satisfy the condition that 0.8EMIN/EMAX.
