The present invention relates to a correction method of document inclination angle for an image reading apparatus such as a scanner, facsimile device, digital copier in which a document is placed on an image reading position, and an image of the document is read, and specifically to an image reading apparatus in which, even when the placed document is inclined, it can be corrected.
In an image reading apparatus such as a scanner, facsimile device, digital copier in which a document is placed on an image reading position, and an image of the document is read, there is a case in which the document is placed while being inclined. When the inclined document is read, for example, copied (image formation), as it is, there is a possibility that some portions of the image are lost.
Accordingly, in the conventional image reading apparatus, an inclination angle of the document is detected by detecting an inclination of a row of characters from image information obtained from the inclined document, and the inclination angle is corrected corresponding to obtained image information.
In the above method, in order to detect the inclination angle of the document, it is necessary that image information is read (pre-scanned) after the document is previously set on a reading position. Therefore, a long period of time is necessary for detecting the inclination angle, and thereby, image reading efficiency is lowered. Further, in order to detect the inclination of a character row, it takes a long time because complicated calculation is necessary, and further, cost is increased because many memories are used for calculation.