Low-Cost Interactive Active Monocular Range Finder

This paper describes a low-cost interactive active monocular range finder and illustrates the effect of introducing interactivity to the range acquisition process. The rangefinder consists of only one camera and a laser pointel; to which three LEDs are attached. When a user scans the laser along s u ~ a c e s ofobjects, the camera captures the image of spots (one from the lasel; and the others from LEDs), and triangulation is carried out using the camera's viewing direction and the optical ax is of the laser. The user interaction allows the rangefinder to acquire range data in which the sampling rate varies across the object depending on the underlying surface structures, Moreovel; the processes of separating objects from the background ador f ind ing parts in the object can be achieved using the operator's knowledge of the objects. 1 . A user can select surfaces or even contours which need to be measured. Unwanted surfaces are simply not scanned. This means that the environment does not need to be controlled. 2. The sampling rate can be changed depending on the complexity of surface structures. Highly structured surfaces are represented by very dense 3-D points, and simple surfaces are described with a small number of points. 3. Some segmentation processes can be carried out by measuring each surface segment separately. This feature is especially useful when prior knowledge of surfaces or objects is available. In the next section, we review some range finding systems closely related to the one described in this paper. The method of the interactive active monocular range finding system is then described, followed by experimental results.