Patent ID: 7616352

Claim:
A document reading device comprising: a document table having a contact glass on which a document is placed; a reading unit including a contact type image sensor which is contained in a case body and adapted to read said document positioned on said contact glass, and a guide shaft which is arranged in said case body to guide movements of said reading unit, wherein: said reading unit includes a chassis attached to a base which is mounted on said guide shaft, and a contact type image sensor which is provided in said chassis, said contact type image sensor having its upper part kept in contact with a reference plane of the chassis by way of a positioning stopper, and being pushed upwardly by means of a compression spring provided in its lower part; said guide shaft is held at a determined length from a reading face of the document, while a length from said guide shaft to said reference plane of the chassis is set so as to obtain an optimum focal length of the contact type image sensor with respect to said document, and said reading unit is positioned apart from said contact glass, and adapted to conduct reading by scanning from a home position to a final reading position in a non-contact manner, and to reciprocally move from the final reading position to the home position; and said base of said reading unit has a through hole whose inner peripheral face is in contact with said guide shaft at three points, as seen in a sectional view.