Patent ID: 8253991

Claim:
A duplex scanning apparatus for scanning a document to obtain a document image, said duplex scanning apparatus comprising: an automatic document feeder for feeding said document, said automatic document feeder comprising a first scanning module, wherein when said document is fed by said automatic document feeder, said first scanning module scans a second side of said document, thereby obtaining a second-side image of said document image; and a flatbed scanner disposed under said automatic document feeder, and comprising: a glass platform for placing said document; a second scanning module for scanning a first side of said document, thereby obtaining a first-side image of said document image; a first calibration plate disposed on said second scanning module, and comprising a calibration plate first end, a calibration plate second end and a calibration plate middle part, wherein a first included angle is defined between said calibration plate first end and said calibration plate middle part, and a second included angle is defined between said calibration plate second end and said calibration plate middle part, so that each of a distance between said calibration plate first end and said first scanning module and a distance between said calibration plate second end and said first scanning module is shorter than a distance between said calibration plate middle part and said first scanning module; and a second calibration plate disposed on said glass platform.