Detection of Foreign Bodies in Soft Foods Employing Tactile Image Sensor

Abstract

In the inspection work involving foodstuffs in food factories, there are cases where people not only visually inspect foodstuffs, but must also physically touch foodstuffs with their hands to find foreign or undesirable objects mixed in the product. To contribute to the automation of the inspection process, this paper proposes a method for detecting foreign objects in food based on differences in hardness using a camera-based tactile image sensor. Because the foreign objects to be detected are often small, the tactile sensor requires a high spatial resolution. In addition, inspection work in food factories requires a sufficient inspection speed. The proposed cylindrical tactile image sensor meets these requirements because it can efficiently acquire high-resolution tactile images with a camera mounted inside while rolling the cylindrical sensor surface over the target object. By analyzing the images obtained from the tactile image sensor, we detected the presence of foreign objects and their locations. By using a reflective membrane-type sensor surface with high sensitivity, small and hard foreign bodies of sub-millimeter size mixed in with soft food were successfully detected. The effectiveness of the proposed method was confirmed through experiments to detect shell fragments left on the surface of raw shrimp and bones left in fish fillets.

Detection and prevention of foreign material in food: A review

“…Some FMs are difficult to detect and often the final inspection is performed by human eyes or by touch [ 66 ]. For example, a bone in a soft fish filet may only be found with touch and thus requires human resources and time [ 66 ].…”

Tactile-Sensing Technologies: Trends, Challenges and Outlook in Agri-Food Manipulation

“…Tactile sensation has been used to identify foreign objects in food items Shimonomura et al [34]. By rolling a tactile sensor over the item, hardness measures were mapped to the image space and could be identified.…”

“…Tactile sensing is also experiencing increased interest in food preparation tasks, such as robotic cooking, where the qualities applied to harvesting and handling are similarly utilised. Tactile sensing allows for measurements without requiring a line of sight, enabling sensing in problems like food item cutting and pouring items from within packaging [30][31][32][33][34][35].…”

Vision-Based Contact Adhesion Measurement Method on Soft Matter Surfaces

“…Vision-based tactile sensors provide a better solution for measuring the contact force on soft matters, but they have not yet been applied to the measurement of adhesion force. Most of the related studies have focused on planar structures and pressure measurements. , Although the curved structures were able to achieve a 360° sensing range, , they were not sufficiently miniaturized (i.e., millimeter level) for local detection in in vivo environments. In fact, the earliest vision-based tactile sensors were based on the optical waveguide .…”