Patent ID: 8174554

Claim:
An optical scanning device comprising: an emission unit which emits a light beam; an oscillating mirror which deflects the light beam to reciprocate on a scanning surface in a main scanning direction; and a controller which controls the emission unit to be on and off to form a pattern of dots in each cell of a plurality of cells defined on the scanning surface, each cell being composed of a plurality of pixels, the pattern being formed according to a gradation of the cell and based on a dot-concentrated threshold matrix, wherein the threshold matrix is defined such that the pattern of dots to be formed in the cell includes a plurality of pairs of adjacent dots in a sub-scanning direction, the sub-scanning direction being orthogonal to the main scanning direction, and wherein, among the plurality of pairs of adjacent dots to be formed in each cell, a number of pairs of adjacent dots which are closer than an interval of adjacent ideal scanning lines is equal to a number of pairs of adjacent dots which are further than the interval.