BINARIZATION DEVICE OF IMAGE SIGNAL

摘要

PROBLEM TO BE SOLVED: To prevent the recognition rate of an image from being lowered even if lighting nonuniformity, shading, shadow, etc., exist in the original image by setting thresholds in accordance with the levels of envelopes on the peak and bottom sides of an image signal. SOLUTION: A camera 2 scans an original image 1 horizontally H in the control of a controlling part 6 and an image signal V1 outputted from the camera 2 is successively stored in an image memory 3. A peak side envelope detection circuit 11 detects a peak side envelope Vhp of a horizontal image signal Vh read from the memory 3. A bottom side envelope detection circuit 12 detects a bottom side envelope Vhb of the signal Vh. A horizontal peak and bottom middle level generation circuit 13 generates intermediate levels of the envelopes Vhp and Vhb of the peak and bottom sides as threshold Vth. A binarization circuit 5 inputs the signal Vh and the threshold Vth and outputs a binarized image signal V2.