Developer residue detecting device, developing unit, processing unit and image forming equipment

The invention relates to a developer residue detecting device, which is used for detecting the developer residue in a developing unit capable of being detachably arranged in the body of image forming equipment. The developer residue detecting device comprises a detecting unit, a rotating unit and a photo sensor, wherein the detecting unit is arranged in the developing unit and is used for detecting the developer residue in the developing unit; the detecting unit comprises a rotatable detecting part; the rotating angle range of the detecting part is changed along with the change of the developer residue in the developing unit; the rotating unit comprises a rotating part which is arranged outside the developing unit and rotates along with the rotation of the detecting part; the photo sensor is used for detecting the rotation of the rotating part; and through the cooperation of the photo sensor and the rotating unit, that whether the developer residue in the developing unit is in a sufficient state, in a state of being about to run out, or in a run-out state can be determined.