A parallel driving mechanism for an optical chassis in a scanner includes a casing, an optical chassis, a linkage member, a screw bar and a driving member. The casing has two parallel guide rails. The optical chassis has two rollers at two ends movably resting on the guide rails and two pivotal joints. The linkage member has two symmetrical upper links pivotally engaging with two symmetrical lower links on two sleeves which have opposite internal screw threads formed therein. The driving member may rotate the screw bar which moves the sleeves to move toward or against each other so that the upper and lower links may be extended or withdrawn to more the optical chassis moving reciprocally on the guide rails to perform scanning operation.
The invention is a scan device with elastic reserve type and its scan method, mainly applied to the light, thin, short and small scanner, image recorder, etc. The invention includes a guide bar, a chassis, a gear structure, an elastic module, a fastening structure and a sensor device, wherein, a scan module is on the chassis, the gear structure is consisting of at least one gear, the fastening structure is consisting of at least two fasteners and the sensor device is consisting of at least two sensors with one objective. To use the elasticity with the feature of reserving ability and the fastening structure is to move the chassis for scanning. The scanning motion of start and stop is via the sensor device. For combining the function of the above each part, most of them take traditionally mechanical transmission except that scan module is electrical power.