To provide an image reading device which neither makes a user feel dazzle when detecting a size of an original, nor reduces work efficiency, and in which energy consumption of a light source is reduced, and a long life is achieved.
An image reading device 30 is equipped with: a line sensor 53 that is an image pickup device; a contact glass 32 on which an original D is placed and a reference point A is set with which the corner of the original D is aligned for the placement of the original D; a light source 43 which is disposed under the contact glass 32, in which a plurality of point light sources 43a are arranged in line from one end corresponding to the reference point A in a main scanning direction, and which emits the light to the original D; an optical member such as a first mirror 44 or the like for guiding reflection light from the original D to the line sensor 53; and a read control unit 33 which turns on the point light sources 43a from the point light source 43a corresponding to the one end of the light source 43 to the other end thereof in the main scanning direction in turn and turns off the light source 43 when the edge of the original D is identified based on information from the line sensor 53 receiving the reflection light.
Inoue On
Nishimori Norio
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