| 摘要 |
PROBLEM TO BE SOLVED: To provide a foreign object detection device which surely detects a foreign object on an inspection surface of a subject.SOLUTION: A foreign object detection device comprises: an irradiation system that irradiates measurement light on an inspection surface RG of a subject R; and a light reception system that has a condensing optical system 85 for condensing scattered light Lfrom the inspection surface RG, and a light reception element 84 for receiving the scattered light Lthrough the condensing optical system 85, and receives the scattered light Lin at least two focus states of the condensing optical system 85. Then, as to each of the at least two focus states, information about an intensity distribution of the scattered light is obtained, and presence/absence of a foreign object on the inspection surface is detected by using the information. |
