| 摘要 |
PURPOSE:To detect a foreign matter bearing surface on a substrate in a short time with high accuracy by preventing the line of intersection of two optical planes among plural planes formed by pieces luminous flux scanning on respective measurement surface from crossing the measurement surfaces. CONSTITUTION:A pericle top surface 2a and a reticle reverse surface 1b are scanned by luminous flux 3 and a pericle reverse surface 2b and a reticle top surface 1a are scanned by luminous flux 4; and the planes formed by the pieces of luminous flux 3 and 4 are equalized and the line l of intersection of the two planes crosses none of the measurement surfaces. Scattered light generated isotropically when the luminous flux 3 impinges on foreign matter P on a measurement surface 2a is converged on the optical member 5a of a detecting means 9a and outputted from a photodetector 9a after being increased Scattered luminous flux from the foreign matter P is cut off visual field stops 6b, 6c, and 6d arranged nearby the conjugation position of measurement surfaces 1b, 1a, and 2b to make the outputs of photodetectors 8b, 8c, and 8d of detecting means 9b, 9c, and 9d constant. Consequently, the presence of the foreign matter is detected with the output signals of the photodetectors 8a-8d and the size of the foreign matter is decided from the levels of the output signals. |
