Methods for Indexing Stripes in Uncoded Structured Light Scanning Systems

Abstract

This paper presents robust methods for determining the order of a sequence of stripes captured in an uncoded\nstructured light scanning system, i.e. where all the stripes are projected with uniform colour, width and spacing. A\nsingle bitmap image shows a pattern of vertical stripes from a projected source, which are deformed by the surface of\nthe target object. If a correspondence can be determined between the projected stripes and those captured in the\nbitmap, a spatial measurement of the surface can be derived using standard rangefinding methods. Previous work has\nuniquely encoded each stripe, such as by colour or width, in order to avoid ambiguous stripe identification. However,\ncolour coding suffers due to uneven colour reflection, and a variable width code reduces the measured resolution. To\navoid these problems, we simplify the projection as a uniform stripe pattern, and devise novel methods for correctly\nindexing the stripes, including a new common inclination constraint and occlusion classification. We give definitions\nof patches and the continuity of stripes, and measure the success of these methods. Thus we eliminate the need for\ncoding, and reduce the accuracy required of the projected pattern; and, by dealing with stripe continuity and\nocclusions in a new manner, provide general methods which have relevance to many structured light problems.