Electric potential measuring device and image forming apparatus

An electric potential measuring method comprising the steps of:

• preparing a detection electrode comprised of a conductive material and disposed in opposition to an object to be measured;
• a movable structure comprised of a first solid material portion comprised of a dielectric and a second solid material portion comprised of a material having a relative dielectric constant different from the dielectric or a conductive material and disposed so as to come to the object to be measured side of the detection electrode;
• and
• moving the movable structure in such a way as to change a positional relationship of the first and second solid material portions for the detection electrode in an area between the detection electrode and the object to be measured, whereby a charge induced on the detection electrode by electric lines of force emanating from the object to be measured is modulated, to measure an electric potential of the object to be measured.