Image scanning method

An image scanning method applied in an image scanning device capable of scanning a card, the image scanning device including two groups of rollers capable of rotating clockwise and anticlockwise, a lower image sensing element, and an upper image sensing element opposite to the lower image sensing element, a scanning channel being formed between the upper image sensing element and the lower image sensing element, the image scanning method comprising steps of:

• step one:
• recording background values at the time of the card being without being in the scanning channel, and the background values recorded at the time of the card being without being in the scanning channel being regarded as preset values to be a standard range;
• step two:
• before the card is scanned, checking whether the background values in the scanning channel conform to the preset values by virtue of the upper image sensing element and the lower image sensing element, if the background values in the scanning channel conform to the preset values, executing step five, if the background values in the scanning channel are discrepant with the preset values, executing step three;
• step three:
• driving the card to move a distance Y by virtue of the two groups of the rollers rotating, executing step four;
• step four:
• checking whether the background values in the scanning channel conform to the preset values by virtue of the upper image sensing element and the lower image sensing element, if the background values in the scanning channel conform to the preset values, that the card has been taken away from the scanning channel being denoted, and executing step seven, if the background values in the scanning channel are discrepant with the preset values, executing step five;
• step five:
• presetting a preset movement distance, checking whether a movement distance of the card or a distance of accumulated movements of the card exceeds the preset movement distance, if the distance of the accumulated movements of the card is without exceeding the preset movement distance, executing step three again, if the distance of the accumulated movements of the card exceed the preset movement distance, executing step six;
• step six:
• displaying that the card is stuck;
• step seven:
• stopping checking and proceeding an image calibration, and executing step eight;
• step eight:
• starting scanning the card until the card is completed being scanned, executing step nine;
• and
• step nine:
• completing scanning the card and withdrawing the card from the image scanning device.