Preliminary Tests of the Miniaturization of a Novel Concept of Angular Sensors

Lorenzo Iafolla, Lilian Witthauer, Sara Freund, Lorin Fasel, Azhar Zam, Georg Rauter, Philippe C. Cattin

Research output: Chapter in Book/Report/Conference proceedingConference contribution


This work was done in the framework of the MIRACLE project devoted to the development of a flexible, articulated robotic endoscope to perform laser osteotomies (bone cutting). In order to control this robot with the required accuracy of 0.2 mm at the tip position, a tracking system needs to feed back the pose of the tip and the shape of the endoscope. One of the possible designs of such a robotic endoscope is based on an articulated device that can be tracked by measuring the bending angle at each joint. Recently, we presented (Iafolla et al., 2018) a novel angular sensor called ASTRAS (Angular Sensor for TRAcking Systems), which measures a one degree of freedom rotation by processing a shadow image cast through a shadow mask onto an image sensor. One ASTRAS will be placed at each joint of the articulated robotic endoscope in order to measure their bending angles. The planned diameter of the MIRACLE endoscope is 10 mm and it will contain several components such as the optical fiber for the laser, irrigation and sucking systems, and robot control mechanisms. However, the latest version of ASTRAS covered a volume of 40x40x55 mm3. For this reason, the most demanding requirement for the design of the final ASTRAS sensor is its miniaturization to fit the sensor inside the joint of the endoscope. Consequently, in this contribution, we investigated the possibility of miniaturizing ASTRAS and assess its limitations due to some fundamental aspects. In particular, we built a prototype based on a NanEye camera by AMS (1x1x0.5 mm3) and a micro-milled shadow mask with 0.08 mm wide slits. The tests of this prototype showed encouraging results and will be discussed. In particular, at such small dimensions, there are no unexpected optical effects (e.g. optical diffraction due to the mask) worsening the measurement. Indeed, the precision of 5 arcsec and the linearity error of 23 arcsec RMS are comparable to those of the previous bigger prototype. Further considerations and concepts related to the miniaturization of ASTRAS are also discussed in this paper.

Original languageEnglish (US)
Title of host publication2019 IEEE Sensors, SENSORS 2019 - Conference Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781728116341
StatePublished - Oct 2019
Event18th IEEE Sensors, SENSORS 2019 - Montreal, Canada
Duration: Oct 27 2019Oct 30 2019

Publication series

NameProceedings of IEEE Sensors
ISSN (Print)1930-0395
ISSN (Electronic)2168-9229


Conference18th IEEE Sensors, SENSORS 2019


  • Angular Sensor
  • Medical Tracking Systems
  • NanEye Camera
  • Rotary Encoder

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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