Noncontact Sensing of Surface Hardness Using Pulsating Air Jet

Abstract

This paper describes a new remote sensor for noncontact surface hardness evaluation. Pulsated air jet is generated by acoustic device which drives small area of object surface. The induced vibration is measured with laser interferometry, and the surface hardness is evaluated from it. This process is done without any mechanical contact. The new sensor has some merits over the ones which we have previously reported: firstly, it is less dependent upon surface geometry, secondly, it is not necessary to set the sensor so near the surface, and last, wider rangeability of hardness is realized. The sensor can be applied to robot for soft griping of delicate works, and also to estimation of ripeness of foods such as fluits, or of dryness of painted wet surface. Both sensor and object can get rid of any damage and problems due to mechanical contact in tactile sensing.