SENSOR A LED-ARRAY-BASED DIMENSIONAL SHAPE MEASUREMENTS

An angular scan triangulation range sensor using an integrated array o f light-emitting diodes (LEDs) and a lateral-effect position-sensing d etector is described here. A range map is obtained by means of fast el ectronic scanning of the LEDs of the array. No moving parts are needed for the scanning. The sensor consists of a transmitter, a receiver an d control electronics. The source used by the transmitter module is an array of 32 LED chips. Collimating optics are attached to the source. The receiver includes focusing optics and a one-dimensional position- sensing detector. The transmitter and receiver modules are connected t o a computer, which controls the operation of the transmitter by super vising the sequential scanning of the sources in the array and determi ning the speed of scanning, and of the receiver by providing gain cont rol, reading of the detector output signals and executing signal proce ssing. The sensor output is a set of object surface coordinates or oth er parameters describing the shape, size and position of the object. I n the tests the sensor has been used for profile measurements of cylin drical objects. For a wooden log surface placed at a distance of about 1200 mm, the diameter is estimated with an accuracy better than 2%. B ased on the experimental tests of the scanner within the range 0.2-2 m , it is found that the performance of the sensor is sufficient for man y applications in profile measurement and obstacle detection in roboti cs and machine automation.