| 摘要 |
An image reading apparatus that illuminates or irradiates a document by scanning for reading in two orthogonal directions. In a mode preceding a reading mode, it photoelectrically converts transmitted or reflected light into an image signal, employs a stored threshold value for comparison with the image signal, and discriminates document position or size based on the comparison to set a reading area for the document, such as a medical X-ray film. A reading control inhibits the reading mode while the document is irradiated in the sub-scanning direction from its tip edge across a predetermined distance. The discrimination of a possibly faulty position, including some inclination error, of the X-ray film and the setting of the reading area compensates for the faulty position before the subsequent reading mode begins. The setting of the reading area can involve some re-conveying of the document. An alarm is generated if the discrimination determines that an appropriate reading area cannot be set. Different types of amplification are provided for the discrimination and for the subsequent reading by a switching arrangement based on a discrimination of the operating mode.
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