An Adaptive High-Speed Automatic Binarizing Method by Analog Processing.

Abstract

A binaraized image processing is often used by many measurement systems. It is important to select the suitable threshold level corresponding to measuring surroundings and measuring objects. The digital adaptive binarizing methods are difficult to binarize the image data at high-speed and to measure successively for a long time. In addition it is difficult to construct the simple binarizing system. This paper describes an adaptive high-speed automatic binarizing method by analog processing. A principle of the method is to detect the peak value and valley value of the CCD sensor outputs, and is to set the threshold level automatically by using their values. The features of the method are: (1) to distinguish between opaque and transparent objects; (2) to set threshold level automatically according to measuring surroundings. We constructed the prototype system by using analog electric circuit and applied the system to dimension measurement of both transparent and opaque objects. The binaraized outputs to opaque object by the system are accurate within 5 pixel and that of transparent object are accurate within 9 pixel. This results are sufficient precision compared with non-adaptive method. When the proposed method is applied to one dimensional CCD, the sampling time is twice as long as the scanning time of CCD. And the sampling time in the case of two dimensional CCD is equal to video frame time (about 33 ms). As a result, it is shown that the proposed method is effective for an adaptive high-speed automatic binarizing method.