High-Speed Sorting of Grains by Color and Surface Texture

A high-speed, low-cost, image-based sorting device was developed to detect and separate grains with different colors/textures. The device directly combines a complementary metal-oxide-semiconductor (CMOS) color image sensor with a field-programmable gate array (FPGA) that was programmed to execute image processing in real-time without the need for an external computer. The spatial resolution of the imaging system is approximately 16 pixels/mm. The system utilizes the inherent parallel processing capabilities of FPGA's to inspect three separate streams of grain with a single camera/FPGA combination. Kernels are imaged immediately after dropping off the end of a chute and are diverted by activating an air valve. The system has a throughput rate of approximately 225 kernels/s overall, which is much higher than previously developed image inspection systems. This throughput rate corresponds to an inspection rate of approximately 25 kg/h of wheat. Testing of the system resulted in accuracies of 96% for separating red wheat from white wheat, 93% accuracy for separating barley from durum, and 92% for separating brown flax from yellow flax. The sorter should find use in removing other defects found in grain, such as scab-damaged and bunted wheat. Parts for the system cost less than 2, 000, so it may be economical to run several systems in parallel to keep up with processing plant rates.