Development of a Compact Tactile Sensor Using a Pinhole RGB Camera

Miniaturized vision-based tactile sensors (VBTSs) are essential for compact and high-resolution surface perception in constrained environments. However, conventional lens-based imaging systems are often bulky and difficult to integrate into thin sensor modules. To address this, we propose a novel VBTS design based on pinhole imaging, which eliminates lens assemblies and reduces overall sensor thickness from 34 to 15 mm. The sensor integrates active illumination and a reflective elastomer layer, enabling the photometric reconstruction of dense surface geometry from a single RGB image. We evaluate the system on representative objects with diverse surface features and compare it against a conventional lens-based sensor. Quantitative analysis using Tenengrad and high-frequency energy ratio metrics shows that, despite increased noise, the lensless design maintains sufficient texture clarity and exhibits heightened sensitivity to fine surface gradients. These results demonstrate the potential of pinhole-based VBTSs for compact, low-cost, and high-resolution tactile sensing through vision-based depth reconstruction.