SpectraTac: A Compact Camera-Free Optical Tactile Sensor with Distributed Color Sensing
2026-08-31 • Robotics
Robotics
AI summaryⓘ
The authors developed SpectraTac, a small and cheap sensor that can feel touch without needing a camera. It uses colored lights and a special squishy clear material to detect how something presses on it by measuring color changes with tiny sensors. This helps the device figure out how strong the touch is in 3D and where it happens with good accuracy. The sensor is simple, low-cost, and can be used in robots or devices that interact with people. Their tests showed it works well for tracking forces and touch locations in real-time.
Tactile sensingOptical sensorElastomerRGB illumination3D force measurementContact region classificationColor sensingHuman-machine interactionLow-dimensional sensingData-driven decoding
Authors
Hao Wu, Haotian Guo, Yu Feng, Yutong Wang, Yanzhe Wang, Jianshu Zhou
Abstract
Tactile sensing is essential for physical interaction in robotics and human--machine systems. However, combining rich tactile information with compact hardware, low cost, and low computational overhead remains challenging. This work presents SpectraTac, a compact, camera-free optical tactile sensor that combines active red--green--blue (RGB) illumination with spatially distributed color sensing. Contact deforms a compliant transparent elastomer and modulates its internal light field, producing spatially differentiated changes in color and intensity. Three distributed color sensors capture these responses as low-dimensional spatio-spectral features, avoiding cameras, imaging optics, and high-dimensional image processing. The device measures 19.2 mm in diameter and 4 mm in height, with a material cost below USD~5. A data-driven decoding framework simultaneously estimates three-dimensional (3D) force and the contact region from the optical measurements. For 3D force prediction, the sensor achieved mean absolute errors (MAEs) of 0.161, 0.164, and 0.429 N along the x-, y-, and z-axes, respectively. The nine-region contact-classification accuracy was 99.9%. We further evaluated real-time 3D force tracking and contact-region-based human--machine interaction through an interactive control task. These results indicate that distributed color-resolved optical sensing offers a compact, low-cost alternative to camera-based tactile sensing for robotics, wearable sensing, and interactive systems.