METHOD AND DEVICE FOR DETECTING FOREIGN MATTER

摘要

PROBLEM TO BE SOLVED: To provide a method and a device for positively detecting a foreign matter with excellent safety. SOLUTION: Radio waves are radiated to a concave mirror, and reflected waves from the concave mirror are focused in front. The reflected waves from the focus position are received by the concave mirror, and receive waves reflected from the concave mirror are signal-processed to detect the presence of the foreign matter in the focus position.