| 摘要 |
PURPOSE:To obtain a photoelectric detection signal with a good SN ratio by irradiating a linear or beltlike detection area on the surface of a body with beam light which becomes linear or beltlike on the body surface. CONSTITUTION:A laser 51, a condenser lens 52, a cylindrical lens 53, beam splitter 54 which guides light to a visual observation system behind 71, a beam splitter 56 which guides light to an optical system for photoelectric detection behind a condenser lens 66, a beam splitter 58, the pupil 59 of an objective, etc., are provided as an optical illumination system. Then, the lens 53 is divided into a section which operates as a parallel plane plate and a section which is perpendicular to it and has the largest curvature; the former forms an image of laser beam on the pupil 59 and the latter forms an image of light from a light source nearby a field lens 55 temporarily and operates so that luminous flux passed through a relay lens 57 becomes parallel and enters the lens. This optical illumination system irradiates a mask 61 and a wafer 62 as the body surface with the light from the light source in a linear or beltlike shape and also guides scattered light to an image sensor 70. |
