Influence of material optical properties in direct ToF LiDAR optical tactile sensing : comprehensive evaluation

Aulika, Ilze (author), Ogurcovs, Andrejs (author), Kemere, Meldra (author), Bundulis, Arturs (author), Butikova, Jelena (author), Kundzins, Karlis (author), Bacher, Emmanuel (author), Laurenzis, Martin (author), Schertzer, Stephane (author), Stopar, Julija (author), Zore, Aleš (author), Kamnik, Roman (author)

Optical tactile sensing is gaining traction as a foundational technology in collaborative and human-interactive robotics, where reliable touch and pressure feedback are critical. Traditional systems based on total internal reflection (TIR) and frustrated TIR (FTIR) often require complex infrared setups and lack adaptability to curved or flexible surfaces. To overcome these limitations, we developed OptoSkin—a novel tactile platform leveraging direct time-of-flight (ToF) LiDAR principles for robust contact and pressure detection. In this extended study, we systematically evaluate how key optical properties of waveguide materials affect ToF signal behavior and sensing fidelity. We examine a diverse set of materials, characterized by varying light transmission (82–92)%, scattering coefficients (0.02–1.1) cm−1, diffuse reflectance (0.17–7.40)%, and refractive indices 1.398–1.537 at the ToF emitter wavelength of 940 nm. Through systematic evaluation, we demonstrate that controlled light scattering within the material significantly enhances ToF signal quality for both direct touch and near-proximity sensing. These findings underscore the critical role of material selection in designing efficient, low-cost, and geometry-independent optical tactile systems.

• Language: English
• Keywords: optical tactile sensing, time-of-flight (ToF) LiDAR, frustrated total internal reflection (FTIR), waveguide materials, light scattering, diffuse reflectance, refractive index, contact detection, proximity sensing, silicone resin, 3D-printed polymer materials, acrylic glass
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 18 str.
• Numbering: Vol. 18, iss. 14, art. 3287
• PID: 20.500.12556/RUL-170829
• UDC: 681.5
• ISSN on article: 1996-1944
• DOI: 10.3390/ma18143287
• COBISS.SI-ID: 242765571
• Publication date in RUL: 17.07.2025

Record is a part of a journal

• Title: Materials
• Shortened title: Materials
• Publisher: MDPI
• ISSN: 1996-1944
• COBISS.SI-ID: 33588485

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: optično krmilno zaznavanje, čas preleta (ToF) Lidar, interni popolni odboj (FTIR, material za optično vodilo, sipanje svetlobe, difuzna refleksija, lomni količnik, zaznavanje dotika, silikon, 3D natisnjeni polimerni materiali, akrilno steklo

Projects

• Funder: EC - European Commission
• Project number: 101070310
• Name: Physical Cognition for Intelligent Control and Safe Human-Robot Interaction
• Acronym: Sestosenso

• Funder: EC - European Commission
• Project number: 739508
• Name: Centre of Advanced Materials Research and Technology Transfer CAMART²
• Acronym: CAMART2