Method for aligning charge coupled device of a scanner

A method for setting an effective scanning range of a scanner, said scanner comprising a housing having a transparent window for placing a document to be scanned, a test region installed in the housing having a positioning mark in it, a scanning module movably mounted in the housing for scanning the document, the scanning module comprising a charge coupled device (CCD) having an array of optic sensors for converting a line image into an analog signal array, and an analog-to-digital (A/D) converter for converting the analog signal array into an image data array, the method comprising the following steps of:

• (1) moving the scanning module to the test region;
• (2) generating an image data array which comprises the image of the test region in it by using the CCD and the A/D converter;
• (3) identifying the positioning mark from the image data array;
• and
• (4) setting an effective scanning range along the array of optic sensors which defines the start and stop positions of valid image data within the image data array according to the identified positioning mark.