Figure 3.
The two-axis optical sensor. (a) the 3D design produced in SolidWorks 2015 (DS SolidWorks Corp., Waltham, MS, USA); (b) a photograph of the complete optical sensor and the two rectangular hollow parts glued on the adhesive plasters; (c) an example of the sensor’s placement on the metacarpophalangeal joint of the left index finger.