Scanner

A scanner, comprising,

• a calibration strip having a top surface and a bottom surface;
• an automatic document feeder (ADF) step glass having a top surface, the calibration strip coupled to the top surface of the ADF step glass in an ADF scan area;
• a duplex scan sensor fixed in position in an ADF, the ADF coupled to the scanner such that the duplex scan sensor is located above, and can view, the calibration strip, where the top surface of the calibration strip is used to calibrate the duplex scan sensor;
• a flatbed scan sensor movably positioned along a bottom surface of the ADF step glass, where the flatbed scan sensor can view the bottom surface of the calibration strip when the flatbed scan sensor is located in a calibration position, where the bottom surface of the calibration strip is used to calibrate the flatbed scan sensor;
• wherein the flatbed scan sensor has a calibration distance and an ADF scan distance and where the ADF scan distance is longer than the calibration distance by 0.6 mm or less.

A method of calibrating a duplex scanner, comprising:

• scanning a top surface of a single calibration strip with a duplex scan sensor to produce duplex calibration data;
• scanning a bottom surface of the single calibration strip with a flatbed scan sensor to create flatbed calibration data;
• adjusting stored calibration values for the duplex scan sensor and the flatbed scan sensor using the duplex scan data and the flatbed scan data respectively;
• wherein the duplex scan sensor has a calibration distance and a scan distance and where the scan distance is shorter than the calibration distance by 0.4 mm or less.