A proposal of new contactless layered sensor for material identification

This paper proposes an optical and electrical layered sensor as a new contactless sensor for material identification. In the proposed sensor, the optical properties of the material are measured by a light emitting diode (LED) and a phototransistor, and the electrical properties are measured by indium tin oxide (ITO) film electrodes with the transparent conductive properties arranged on the surfaces of the LED and phototransistor. Therefore, the optical and electrical properties of the material can be simultaneously measured by the single sensor. To test the sensor experimentally, six material samples - clear, white, and black acrylic, clear glass, white polytetrafluoroethylene (PTFE), and silver aluminium - were prepared, and identification of their sample materials and detection of distance between the sensor and the surface of material were demonstrated by using measurement values of the optical and electrical properties in the proposed sensor. In addition, the measurement values of optical properties with and without ITO film electrodes and those of electrical properties using the ITO film electrodes and the stainless steel film electrodes were compared. The results suggested that it is possible to measure both optical and electrical properties using the proposed sensor, although there are still some problems that must be addressed.