Tea sorted by selective vision system

After harvest, herbs and tea plants become mingled with foreign material such as grit, stems, and plastic that must be removed before packaging. Traditional sorting methods have failed to yield satisfactory purity or discarded too much valuable material. Researchers at the Fraunhofer Institute for Information and Data Processing (IITB; Karlsruhe, Germany; www.iitb.fhg.de) working on behalf of health-product manufacturer Salus Haus (Bruckmühl, Germany; www.salus.de), have solved this separation problem by adding a high-speed vision system to the optomechanical sorting process. "The process used for separating waste glass or bulk minerals has now been applied to herbs," says project manager Kai-Uwe Vieth. "Only 1% of useful material is lost."

Dried and shredded plants are shaken to distribute them evenly on a conveyer belt. This layer is imaged by a 2k RGB linescan camera and the images transferred to a custom-made frame grabber and analyzed by software written by IITB. If the color range of an object falls outside the specified range, then the system checks its geometry. If this exceeds a specified length and width, the system activates the appropriate nozzle to blow the object into a receptacle. Tea producers have been able to purify 100 kg of plants an hour in the pilot plant, and a demonstration plant has been set up in Karlsruhe to interest other herb-processing firms.