Electrophotographic apparatus having pre-exposure means

An electrophotographic apparatus comprising:

• a photosensitive member;
• an electrostatic image forming means for forming an electrostatic image on said photosensitive member, said electrostatic image forming means including charging means for charging said photosensitive member, and image exposure means for effecting image exposure on said photosensitive member charged by said charging means;
• pre-exposure means for pre-exposing said photosensitive member before said photosensitive member is charged by said charging means;
• and
• detecting means for detecting a surface potential of said photosensitive member;
• wherein said apparatus is provided with a sequence in which a dark portion and a light portion are formed on a first portion and a second portion, respectively, on said photosensitive member by said electrostatic image forming means, whereafter said first portion and said second portion are exposed by said pre-exposure means, and then said first portion and said second portion are charged by said charging means, and then the surface potentials of said first portion and said second portion are detected by said detecting means, and an exposure amount at which said photosensitive member is exposed by said pre-exposure means is controlled in conformity with the potential of said first portion and the potential of said second portion detected by said detecting means in said sequence.