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.
Highlights
Food safety is a major concern for consumers
The nylon thread pieces were placed on top of the urethane gel or solid plate, and the sensor output image was acquired by pressing the tactile image sensor to the thread
The experimental results indicated that the larger the diameter of the nylon thread and the harder the object placed under the nylon thread, the greater the response of the tactile image sensor
Summary
Food safety is a major concern for consumers. for companies engaged in food production and processing, quality control of food products is among the most important issues. Food pretreatment process such as washing, removal of inedible parts, and cutting of food materials takes place. In this process, the detection of foreign bodies can be an important consideration. The captured image can be analyzed to distinguish between foreign objects and other objects, and X-ray inspection machines can detect a wider range of objects than metal detectors, such as stones, glass, bones, and plastics. Such machines can check for cracks and chips in weight and appearance
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