Always-on low-power optical system for skin-based touchless machine control

Embedded vision systems are smart energy efficient devices that capture and process a visual signal in order to extract high level information about the surrounding observed world. Thanks to these capabilities, embedded vision systems attract more and more interest from research and industry. In this work, we present a novel low power optical embedded system tailored to detect the human skin under various illuminant conditions. We employ the presented sensor as a smart switch to activate one or more appliances connected to it. The system is composed by an always on low power RGB color sensor, a proximity sensor and an energy efficient microcontroller (MCU). The architecture of the color sensor allows a hardware pre-processing of the RGB signal, which is converted into the $rg$ space directly on chip reducing the power consumption. The $rg$ signal is delivered to the MCU, where it is classified as skin or non-skin. Each time the signal is classified as skin, the proximity sensor is activated to check the distance of the detected object. If it appears to be in the desired proximity range, the system detects the interaction and switches on/off the connected appliances. The experimental validation of the proposed system on a prototype shows that processing both distance and color remarkably improves the performance of the two separated components. This makes the system a promising tool for energy efficient, touchless control of machines.