US Patent 7149005 Depth of field control device

A depth of field control device is provided. The depth of field control device is installed on an automatic document feeder having a scan glass surface. The depth of field control device comprises a plate member having at least one protrusion on its front side and a hook structure at its backside, wherein the hook structure at the backside of the plate member hooks the automatic document feeder and the protrusion is in contact with the scan glass surface; a reflection sheet attached to the plate member and fixed on the automatic document feeder; and a flexible device biasing the plate member at the backside of the plate member.