Design and implementation of a scanner with stitching of multiple image capture

Instead of the flatbed scanner which moves slowly as it scans, we propose in this paper a new design of a high-speed and low-power scanner with a stitching of multiple image capture. We divide the area to be scanned into four parts, capture each image and then stitch these into a whole. Our design uses the compact camera module (CCM) advantages of high integrity, white balance, advanced calibration, and auto exposure for color and luminance, all of which reduce the software post-processing time. To solve the light reflection problem we propose an interleaved light source compensation method. To reduce power consumption and prevent light reflection among the four scan areas, we scan the four images one by one, during which a single CCM is turned on while the others are turned off. We use field of view (FOV) calculation to obtain the overlap area used by the stitching algorithms.

I. Introduction

A typical flatbed scanner causes some inconvenience during use, such as low speed and high power consumption. For example, the scanner's cold cathode fluorescent lamp (CCFL) needs to be preheated for several dozen seconds until it reaches normal color temperature. While scanning, the traditionally designed scanner also produces a mechanical noise because of the stepping motor. In addition, the moving mechanical parts of the flatbed scanner may produce the phenomenon of picture discontinuity if, as a result of wear, the stepping motor loses a step. As the flatbed scanner also consumes much power, it requires an extra adaptor to maintain a sufficient supply, thus increasing the weight of the machine and making it more inconvenient. In order both to achieve a good enough picture quality and to scan at the desired speed, we propose a new design of a high-speed and low-power scanner with multiple image capture stitching by using the CCM that is commonly used in mobile phones, thus providing both a small volume and sufficient resolution. This new design uses the camera capture method instead of the contact image sensor (CIS) of the flatbed scanner to obtain the desired image [1]. We use four CCMs to take the four images and then stitch them into a whole. This improves the scanning speed because the scanner requires neither any moving nor any stepping motor and uses light-emitting diodes (LED) instead of CCFL, thus reducing both power consumption and mechanical noise [2].