Patent ID: 8718505

Claim:
A voltage output apparatus that outputs a voltage to a process member that acts on an image bearing member, comprising: a voltage application part that applies a DC voltage to the process member; a current detection part that detects a detected value corresponding to a current flowing in the process member when the DC voltage is applied to the process member; and a control unit that obtains a surface potential of the image bearing member based on information regarding a voltage difference between a first DC voltage and a second DC voltage different from the first DC voltage, wherein after the image bearing member is charged with a predetermined voltage, the first DC voltage is a voltage applied by the voltage application part to the process member at a time the detected value detected by the current detection part reaches a value corresponding to a current value in which discharge of the image bearing member starts, the first DC voltage being lower than the predetermined voltage, and the second DC voltage is a voltage applied by the voltage application part to the process member at a time the detected value detected by the current detection part reaches a value corresponding to a current value in which discharge of the image bearing member starts, the second DC voltage being higher than the predetermined voltage.