Image forming apparatus having magnification capabilities with charge removal outside image area

Claim 1

An image forming apparatus comprising: a platen adapted for putting thereon an original document; means for illuminating the original document put on said platen; a photosensitive medium; charging means for applying electric charge on said photosensitive medium; means for setting a desired magnification; means for forming a latent image corresponding to the illuminated original document on the charged photosensitive medium wherein said latent image is formed at the desired magnification set by said setting means; means for removing charge from a portion of said photosensitive medium, said removing means comprising a plurality of light sources each individually operable; developing means for providing a visible image for the latent image formed on said photosensitive medium; means for transferring the visible image on said photosensitive medium to a recording sheet; a plurality of sensing means each for sensing whether the original document is absent at associated ones of a plurality of predetermined positions on said platen; means for detecting a size of the original document prior to the latent image forming operation by said forming means, said detecting means designating the original document to corresponding to one of a plurality of fixed sizes based on respective outputs of said plurality of sensing means; means for determining light sources to be turned on and light sources to be turned off among said plurality of light sources, and for determining a period of time for the light sources to be turned off on the basis of the combination of the magnification set by said setting means and the size detected by said detecting means; and means for controlling, during the latent image forming operation of said forming means, the operation of said plurality of light sources in accordance with a determination result of said determining means to that charge can be removed from an area on said photosensitive medium other than the area of the latent image corresponding to the original document.