There is provided an image input device in which a carriage mounted with an image sensor and three types of light source is moved in a sub-scanning direction of a document by a motor and the document is read in a line sequential manner. In one configuration, a lookup table of adhesion factors is used to predict the occurrence of wheel slipskid. The device is designed and sized to be mobile. The tubular body has an outer sleeve adjustably receiving an inner sleeve at the distal end of the tubular body.