| 摘要 |
PURPOSE:To detect the micro-foreign matter on a pellicle in a high-sensitivity range by approximately perpendicularly irradiating the pellicle with light and receiving the forward scattered light from a defect by two photoelectric detectors provided in the symmetrical positions on opposite sides. CONSTITUTION:The pellicle 1 stretched on a frame 2 is approximately perpendicularly irradiated with a luminous flux 11 from a light source 10 from above. Of the scattered light rays of the foreign matter by this irradiation light 15, the forward scattered light rays 20, 30 are received by the two photoelectric detectors 23, 33 provided in the symmetrical positions on both sides of the pellicle 1. The output signals of the detectors 23, 33 are switched in the switching part of a signal processing circuit and are stored in a memory. After the entire surface of the pellicle 1 is inspected by a prescribed control section, the information on the foreign matter is read out of the memory and the various levels by each picture element are compared with a reference level. The presence or absence of the foreign matter and the detection position thereof are displayed on a display section. |
