Oki 18 Service Manual page 52

(ii) Transfer of correction data to head driver correction data
The LED driver corrects the LED illumination by controlling the LED current. The LED illumination can be set in 16
steps, with 7 steps in the direction of illumination increase in relation to the standard value, and 8 steps in the
direction of decrease. For this reason, the LED correction data is a 4-bit data for each dot.
The relationship between the LED correction data and LED current correction steps with the LED driver used in an
LED head is shown below.