Shutter calibration document size detection.

摘要

An apparatus in which shutters used to occlude the region of the platen not supporting the original document being reproduced are calibrated. After the fully open position (112 or 114) of the shutters is determined, the size (LxW) of each original document being reproduced may be determined. In calibrating the shutters, an original document having a predetermined size is positioned on the platen with one set of perpendicular edges thereof being located at a registration position. The shutters are moved from the fully open position to another set of perpendicular edges of the document. The distance (L min or W min )that the shutters move between the open position and the edges of the document is measured. With this information, the distance (R or Q) between the open position and the registration position may be determined as a function (L + L min or W + W min )of the size of the original document and the distance that the shutters move. After the location of the open position of the shutters has been calibrated, the size of other original documents may be determined. The original document of unknown size is positioned with one set of perpendicular edges thereof located at the registration position on the platen. The shutter is moved from the open position to the other set of perpendicular edges of the original document. The distance that the shutter moves from the open position (L min or W min ) to the edges of the document is measured and the size of the document (L or W) calculated as a function (R-L min or Q-W min ) of the shutter distance moved and the calibrated distance between the open position and the registration position.