IMPROVEMENT OF SELF-MIXING SEMICONDUCTOR LASER RANGE FINDER AND ITS APPLICATION TO RANGE-IMAGE RECOGNITION OF SLOWLY MOVING OBJECT

An infrared range finder using a self-mixing laser diode (SM-LD), which has been proposed and developed by the authors, can measure not only a range of a moving target but its velocity simultaneously. In this paper, described is that the precise mode-hop pulse train can be obtained by employing a new signal processing circuit even when the backscattered light returning into the SM-LD is much more weaker. As a result, the distance to a tilted square sheet made from aluminium or white paper, which is placed 10 ㎝ through 60 ㎝ from the SM-LD, is measured with accuracy of a few percent even when the tilting angle is less than 75 degrees or 85 degrees, respectively. And in this paper, described is the range-image recognition of a plane object under the condition of standstill. The output laser beam is scanned by scanning two plane mirrors equipped with each stepping motor. And we succeeded in the acquisition of the range-image of a plane object in a few tens of seconds. Furthermore, described is a feasibility study about the range-image recognition of a slowly moving plane object.