2-DIMENSIONAL MEASUREMENT OF ROTATIONAL SPEED OF A DIFFUSE OBJECT-BASED ON LASER-DOPPLER ANEMOMETRY

A novel measurement method based on laser Doppler anemometry that dete rmines the pure rotational speed of a diffuse object on the condition that its axis of rotation is in a plane perpendicular to the illuminat ing laser lights is described. The rotating object is illuminated by t hree parallel laser lights and its rotational speed is calculated from beat frequencies resulting from the mixing of their backscattered lig hts. To verify the principle, measurements of rotational speed of a br ass cylinder were performed for rotational speeds in the range of 30-5 00 rpm. The measured values have a fairly good agreement with the pres elected values over this range. The present method is useful for detec tion of rotational conditions of machinery components assembled in rot ating or vibrating structures.