Apple scanner uses UV and infrared to identify defects

US Department of Agriculture (USDA) scientists have developed and patented an optical scanning system to scrutinise defects in apples before they are packed.

The system can provide evidence of certain kinds of defects, such as cuts and bruises, or contaminants, such as specks of fertiliser from orchard or field soil.

As the apples travel along a conveyor, each apple is simultaneously exposed to two forms of illumination: ultraviolet (UV) light from a fluorescent lamp and near-infrared light from a halogen lamp. Positioned above the conveyor belt, a high-speed multi-spectral line scanner captures images of each apple.

The near-infrared light is then analysed for tell-tale patterns of defects, while the UV light discloses the whereabouts of contaminants.

When linked to a pass/fail rejection mechanism, the system can separate the problem apples from others.

At present, the system offers — at the rate of about three to four apples per second — a 180° view of each apple’s exterior. The scientists are now working to improve the process, so that it will provide a 360° whole-surface view for thorough inspection.

Last year, the developers of the scanner — USDA biophysicist Moon Kim, agricultural engineers Yud-Ren Chen and Kuanglin Chao and biomedical engineer Alan Lefcourt — received a patent for the system.