Laser and sound scanner for non-contact 3D volume measurement and surface texture analysis

Non-invasive three-dimensional measurement of volume and analysis of surface texture is desired in various medical applications, particularly wound healing measurements. In this paper we present a PC-based non-contact laser scanner for volume measurements, and a sound scanner that can accurately measure volumes and analyse surface textures. The non-invasive laser and sound sensors, which are lightweight, are mounted inverted on an X-Y table and the sensor heads are held at a distance of 3 cm from the object to be scanned. Volumes of various shapes on different materials, simulating depth profiles and surfaces of wounds, have been measured accurately and surface textures of varying softness have been analysed. The ratios of measured to actual volume range between 0.8 for the sound sensor and 1.1 for the laser sensor. A linear relation between hardness of 50%-20% concentration gelatin gel surfaces and amplitude of reflected sound waves is also observed. The average time per pass of a scan, for a distance of 3 cm, is 4 s and the computation time for measuring volume and reconstruction of a 3D image using ten passes per scan is 1 min. The unique features of this scanner are its speed, portability, accuracy and simple operation as well as its ability to be used on both soft and hard surfaces.