Optical sorting

Optical sorting (sometimes called digital sorting) is the automated process of sorting solid products using cameras and/or lasers.

Depending on the types of sensors used and the software-driven intelligence of the image processing system, optical sorters can recognize objects' color, size, shape, structural properties and chemical composition. The sorter compares objects to user-defined accept/reject criteria to identify and remove defective products and foreign material (FM) from the production line, or to separate product of different grades or types of materials.

Optical sorters are in widespread use in the food industry worldwide, with the highest adoption in processing harvested foods such as potatoes, fruits, vegetables and nuts where it achieves non-destructive, 100 percent inspection in-line at full production volumes. The technology is also used in pharmaceutical manufacturing and nutraceutical manufacturing, tobacco processing, waste recycling and other industries. Compared to manual sorting, which is subjective and inconsistent, optical sorting helps improve product quality, maximize throughput and increase yields while reducing labor costs.

In general, optical sorters feature four major components: the feed system, the optical system, image processing software and the separation system. The objective of the feed system is to spread product into a uniform monolayer so products are presented to the optical system evenly, without clumps, at a constant velocity. The optical system includes lights and sensors housed above and/or below the flow of the objects being inspected. The image processing system compares objects to user-defined accept/reject thresholds to classify objects and actuate the separation system. The separation system, usually compressed air for small products and mechanical devices for larger products like whole potatoes, pinpoints objects while in-air and deflects the objects to remove into a reject chute while good product continues along its normal trajectory.

The ideal sorter depends on the application, with the product's characteristics and the user's objectives determining the ideal sensors, software-driven capabilities and mechanical platform.

Optical sorters require a compatible combination of light and sensors to illuminate objects and capture images of the objects before the images can be processed and accept/reject decisions made.

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