Double-Roller Tactile Image Sensor for Simultaneous Double-Sided Inspection

This paper proposes a surface inspection method using a double-roller tactile image sensor. The roller-type tactile image sensor provides high spatial resolution by employing a camera and enables continuous contact with the object surface via the rollers. However, a single sensor can acquire a contact image from only one side of the object. To address this limitation, we developed a double-roller tactile image sensor capable of capturing contact images from both sides by sandwiching the object between two rollers. The relationship between applied force and image response was investigated through sensitivity experiments using a force gauge and nylon thread. Experiments using models simulating food and foreign objects revealed that a sufficiently large response was obtained with a pressing force of 0.1 N even for small objects with a diameter of 0.25 mm, while differences in material hardness and foreign object size resulted in differences in the contact image. Furthermore, we performed an experiment using shrimp as an example of food inspection and confirmed that the proposed sensor can successfully capture images of shell fragments remaining on the shrimp.