Provided is an exposure head controller that controls, via pulse width
modulation control, the emission quantity of each light emitting element
in an exposure head having a light emitting element array formed by
arranging a plurality of light emitting elements in a main scanning
direction and a sub scanning direction orthogonal thereto, comprising: a
data retention unit that retains dot gathering control data showing
whether to emit each light emitting element at the starting point side,
terminal point side or in the middle of an emission period corresponding
to a 1 pixel pitch in the sub scanning direction, or to divide and emit
each light emitting element at the starting point side and terminal point
side, emission time data showing the emission time of each light emitting
element, and skew data showing the skew quantity of each light emitting
element a dot gathering operation circuit provided to each light emitting
element and which operates the time in which the light emitting element
is to be retained in a non-emission state from the starting point of the
emission based on the dot gathering control data input from the data
retention unit; a delay time measurement circuit that acquires the skew
data from the data retention unit and acquires the non-emission time data
showing the retention time in the non-emission state from the dot
gathering operation circuit, adding these to seek the delay time to be
set before starting the emission of the light emitting element, measuring
the delay time, and outputting a prescribed signal after the lapse of the
delay time; and an emission instruction circuit that outputs to a light
emitting element drive circuit an emission instruction signal for
instructing the emission of the light emitting element from the point in
time the emission time data is acquired from the data retention unit and
a prescribed signal is output from the delay time measurement circuit up
to the elapse of the emission time indicated by the emission time data.