| 摘要 |
PROBLEM TO BE SOLVED: To detect the true height of an original by reducing the possibility of mis-detection of the height of the original even when an external noise such as an external light enters into an image to be read. SOLUTION: A luminance threshold value is decided from image data on a front side of an original to detect an edge face on the original and the end face edge of the original is detected on the basis of the luminance threshold value. Since the threshold value LB to detect the edge face on the original is not a fixed value but decided on the basis of the image data on the front side of the original, a threshold value close to the luminance of the end face on the original can be obtained from each original and an original edge HP of the end face on the original can be detected on the basis thereof. Thus, an external noise is eliminated and height data of the original can stably be obtained.
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