Surface Texture Characterization Using Optical and Tactile Combined Sensor

Measurements of the surface texture of objects, including optical and tactile features, using a multimodal micro-electromechanical systems (MEMS) sensor are reported in this paper. The proposed MEMS sensor has two functions in its structure: light sensitivity of the MOS structure in the Si substrate and force sensitivity of the strain resistance gauge on microcantilevers embedded in the elastomer. Deflection of the cantilever, induced by an applied force, can be detected as a DC resistance change of the strain gauge film, which depends on the tactile texture including hardness, thickness, and surface roughness of the object. On the other hand, reflected light from the object, detected as AC impedance change at 5 MHz, depends on the color of the object. It is confirmed that the resistance and impedance changes correlate with the physical and optical properties of the object, respectively. Therefore, it has been demonstrated that the surface texture of the object, including optical and tactile features, can be characterized using a single MEMS sensor.