| 摘要 |
PURPOSE:To stably perform measurement due to laser beam with high accuracy, by a method wherein the front and the rear of the position where the image of object made by an objective lens is formed in a mirror cylinder are blocked by light pervious members and this blocked space is brought to a hermetically closed space held under vacuum or filled with inert gas. CONSTITUTION:The focus position of an objective lens 2 where the image I of an object is formed is present in the space sealed under vacuum by two parallel transparent flat plates 3a, 3b and a cylinder supporting both of them. In addition, in place of evacuating the internal mirror cylinder, air break can be prevented by filling inert gas. By this inventive relay optical apparatus, because the light converging point of laser beam is present in vacuum or the inert gas, air break is not generated even when laser with large output is used and various kinds of measurements due to laser beam can be stably performed with high accuracy. |
