Patent ID: 6557762
Filing Date: 2003-05-06
Classification: G06K

Abstract:
A method for increasing depth of scanning field of a scanning device, said scanning device comprising a scanning module comprising an image generating means, lens and a glass plate, the steps of said method comprising:arranging said scanning module to fix the shape of an MTF-DF curve, and determining a tolerant value of MTF, an optimal point of the depth of field, a lowest point and a highest point of a tolerant range of the depth of field; fixing said image generating means at a predetermined position; fixing said glass plate at a distance away from said image generating means and placing a correction document on said glass plate; adjusting the position of said lens in order to form the image of said correction document on said image generating means, further permanently fixing the position of said lens at a point which is between said optimal point of the depth of field and said lowest point of the tolerant range of the depth of field; removing said correction document; and finishing the assembly of said scanning device.