An Object Position And Orientation Ic With Embedded Imager

An analog VLSI chip that determines the position and orientation of an object against a dark background implements an algorithm based on finding the first and second moments of the spatial intensity distribution of the object. 1 These moments allow the centroid (an indicator of position) and the axis of least inertia (an indicator of orientation) to be computed. (Figure 1) The chip has a self-contained array of phototransistors, which are available in CMOS, so that the input is acquired by focussing the scene directly onto the chip surface.2 Using a scheme proposed by Horn, the moments are computed by using a uniform grid of linear resistors.3 Only eight measurements are required. Resistive sheets have been used in earlier systems to determine the position of objects, e.g. a small, bright spot.3 Also, the analog VLSI chip by DeWeerth et al. finds the centroid of an object, though using a different method.' Neither performs the orientation task, which is the primary emphasis of the design presented here.