Lu, Chuang;
Liang, Ziting;
Stoyanov, Danail;
Stilli, Agostino;
(2025)
GelPoLight: A Novel Visual Tactile Sensor Based on Photometric Stereo with Point Lighting.
IEEE Sensors Journal
10.1109/jsen.2025.3535080.
(In press).
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Abstract
Visual tactile sensors based on photometric stereo (VTS-PS) have attracted much attention due to their sensitivity to subtle contact forces and their capability of providing real-time, high-resolution depth maps of contact geometry at a low cost. Conventional VTS-PS, such as Gelsight, typically assume directional and uniform illumination to simplify the algorithm of photometric stereo. However, this assumption poses stringent requirement on the hardware side and limits the sensors in shape, size and flexibility for various applications. Additionally, the configuration of directional lighting exacerbates the issue of cast shadowing. In this paper, We analyse the benefits of point lighting over conventional directional lighting for VTS-PS, and propose GelPoLight: a novel VTS-PS with point lighting, which can help handle or alleviate the aforementioned problems. GelPoLight does not assume ideal diffuse reflectance for the reflective membrane and considers the varying influencing factors of light intensity, light directions, and reflectance factors in the estimation of surface normal vectors. Accordingly, we developed a new calibration method for this approach. We also corrected image distortions caused by light refraction, which is a prevalent issue in visual tactile sensors (VTS). The final results demonstrate that GelPoLight can effectively generate the contact depth map, with errors of approximately 5% in planar direction and 8% in depth direction.
| Type: | Article |
|---|---|
| Title: | GelPoLight: A Novel Visual Tactile Sensor Based on Photometric Stereo with Point Lighting |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1109/jsen.2025.3535080 |
| Publisher version: | https://doi.org/10.1109/jsen.2025.3535080 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. - This work was supported in part by the Wellcome/EPSRC Centre for Interventional and Surgical Sciences (WEISS) under Grant 203145/A/16/Z and in part by the Royal Academy of Engineering Chair in Emerging Technologies Scheme under Grant CiET1819/2/36. For the purpose of open access, the authors have applied a CC BY public copyright licence to any author accepted manuscript version arising from this submission. |
| Keywords: | visual tactile sensor, photometric stereo, Gelsight, directional lighting, point lighting, cast shadowing, surface normal vector, light refraction, depth maps, diffuse reflectance |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Computer Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10204702 |
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