Patent ID: 7149445

Claim:
An electrophotographic printing machine comprising: an image-bearing member, having image frame areas for receiving developed images, said image frame areas separated by interframe areas; a charger for forming a latent image on said image-bearing member; a development station containing toner particles for developing said latent image so as to create a toner image on said image-bearing member, said toner image being created in said image frame area on said image-bearing member for subsequent transfer of said toner image to a receiver member; an optical detector for monitoring and measuring a low coverage of toner particles on said image-bearing member, said low coverage of toner particles relating to a background area of said toner image; a signal produced by said optical detector, representative of the low coverage of toner particles on said image-bearing member; and a control device for controlling said electrophotographic printing machine when said low coverage of toner particles exceeds a certain coverage, said certain coverage including a threshold coverage and a pre-selected coverage.