Abstract: A method of shortening multiple image-scanning duration including setting the scanning parameters of each images in a pre-scanning operation, categorizing the images into groups, assigning images belonging to the same group to a scanning region and finally initializing the scanning operation.

Abstract: A single step multi-section exposure scanning method for a scanner. The scanner includes a photo-sensor and a stepper motor. The photo-sensor has N rows of sensor cells that correspond to each primary color. The scanning device is driven forward an exposure distance for each revolution of the stepper motor. The single step multi-section exposure scanning method includes the following steps. First, the photo-sensor moves forward one exposure distance. One row of sensor cells is exposed after moving every 1/Nth of the exposure distance. Thereafter, analogue voltages obtained through the exposed row of sensor cells are transmitted to an analogue/digital converter. The above process is repeated until the entire document is scanned.

Abstract: A method of reducing memory requirement in the compensation memory unit of a scanner. The method includes providing an even compensation data value and an odd compensation data value and averaging the two to produce an odd-even compensation data value. Only half as much memory space is required to hold the averaged odd-even compensation data values.

Abstract: A focus calibrating method for an image scanning device by testing a focus chart is disclosed. The focus chart has a base sheet and a plurality of black bars with different widths arranged in parallel on the base sheet and spaced from each others. The focus chart is adhered on a bottom surface of a top panel supporting the document positioning plate of the scanner and disposed facing the optical scanning module of the scanner. The focus method includes steps of moving the optical scanning module to read the image data of the focus chart, calculating a focal length value of the image data of the focus chart, judging whether a predetermined optimal focal length is reached or not according to the calculated focal length value, repeatedly moving the optical scanning module with respect to the focus chart to adjust the focal length until the optimal focal length is reached.