IMAGE FORMING APPARATUS AND METHOD CAPABLE OF WEAKENING ELECTRIC FIELD FORMED UNDER PRINTING HEAD

An image forming apparatus includes a printing device; a printing medium conveying unit to convey a printing medium, a first electric charger to charge the printing medium conveying unit, a second electric charger to charge the printing medium conveyed by the printing medium conveying unit, a first surface potential detector to detect a surface potential of the printing medium bearing the electric charge, a second surface potential detector to detect a surface potential of the printing medium bearing the electric charge, and a controller to adjust a power supply voltage supplied to each of the first and second electric chargers in accordance with each of surface potentials detected by the first and second surface potential detectors. The first and second surface potential detectors are located at different positions in a conveying direction in which the printing medium is conveyed by the printing medium conveying unit.