Image reading apparatus

#1. Field of the Invention

#The present invention relates to an image reading apparatus, particularly, to an image reading apparatus in which a target object to be detected is brought into contact with a photosensor array prepared by arranging a plurality of photosensors in a matrix so as to read an image pattern of the object.

#2. Description of the Related Art

#The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

#FIG. 1 is a cross sectional view schematically showing the basic construction of a double gate type photosensor used in an image reading apparatus according to one embodiment of the present invention;

#FIG. 2 is an equivalent circuit diagram of the double gate type photosensor shown in FIG. 1;

#The two dimensional image reading apparatus according to some embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

#First of all, let us describe the construction of a photosensor that is satisfactory when applied to the two dimensional image reading apparatus of the present invention.

#A solid-state image pickup device such as a CCD (Charge Coupled Device) can be used as a photosensor included in the two dimensional image reading apparatus of the present invention. As widely known to the art, the CCD is formed by arranging photosensors such as photodiodes or thin film transistors (TFT) in the form of a matrix. In the CCD, the amount of the electron-hole pairs (amount of charge) generated in accordance with the amount of light irradiating the light receiving section of each photosensor is detected by a horizontal scanning circuit and a vertical scanning circuit so as to detect the brightness of the irradiating light.