Document detection apparatus

Abstract

A scanning background member is provided with two or more superimposed line sets or density patterns of having frequencies unrelated to each other that can be detected by a background detection circuit of a document scanner. The multifrequency edge detection arrangement may also control various image movement and modification features that CCD or full-width array sensors may be used to produce accurate edge detection with minimum processing hardware. Detection of differing frequency density patterns or line sets on the scanning background permits the scanner to precisely determine the edges and cutout areas of a scanned original sheet, while employing minimized hardware and software processing requirements. Frequency-related or other edge detection errors that may result from image patterns, moire effects or other inherent, problematic or random sheet/image conditions may be greatly reduced if not eliminated. The edge detection system of the present invention offers improved performance over repetitive symbol and other scanning background schemes which may require greater processing hardware and software while suffering from lower edge resolution and/or higher edge detection error probabilities.

Dependencies are inferred from the claim text.