A Thin Format Vision-Based Tactile Sensor With a Microlens Array (MLA)

Vision-based tactile sensors have been widely studied in the robotics field for high spatial resolution and compatibility with machine learning algorithms. However, the currently employed sensor's imaging system is bulky, limiting its further application. Here, we present a microlens array (MLA)-based vision system to achieve a low thickness format of the sensor package with high tactile sensing performance. Multiple micromachined microlens units cover the whole elastic touching layer and provide a stitched clear tactile image, enabling high spatial resolution with a thin thickness of 5 mm. The thermal reflow and the soft lithography method ensure the uniform spherical profile and smooth surface of microlenses. Both optical and mechanical characterizations demonstrated the sensor's stable imaging and excellent tactile sensing, enabling precise 3-D tactile information, such as displacement mapping and force distribution with an ultracompact thin structure.