Patent ID: 8588631

Claim:
An image forming apparatus comprising: a rotatable image bearing member including an electroconductive base member and a photosensitive member formed on the electroconductive base member; a contact charging device for electrically charging the photosensitive member; a DC voltage applying device for applying a DC voltage to said contact charging device; an exposure device for exposing the charged photosensitive member to light; a current detecting device for detecting a current passing from said contact charging device to the electroconductive base member of said image bearing member; and a control device capable of executing an operation in a humidity detecting mode in which an area of the photosensitive member is electrically charged by applying a DC voltage to said contact charging device and the photosensitive member is rotated without exposing the area to the light by said exposure device and then the area is electrically charged again by applying the DC voltage to said contact charging device, wherein said control device detects information on humidity on the basis of a current detected by said current detecting device when the area is electrically charged again by applying the DC voltage to said contact charging device.