| 摘要 |
PURPOSE:To prevent the generation of a dew drop, a thermal distortion, etc. to optical parts, etc. by measuring a temperature of the periphery of a dust- proof tube, and adjusting a temperature of a compressed air supplied to the tube. CONSTITUTION:A temperature control device 19 measures a surface temperature of a dust-proof tube 16 and a column by temperature sensors 21, 22, and derives its mean value. Based on its mean value, cooling or heating is executed so that a temperature of a compressed air 23 supplied from a compressor 20 coincides with the mean value. The compressed air 23 which has been adjusted to a mean temperature of the dust-proof tube 16 and the column is supplied into the dust-proof tube 16 through an air supply pipe 17. In this way, a remarkable temperature difference is not generated between the compressed air 23 and optical parts such as reflection mirrors 11, 12, 13, and 14, etc., and a thermal distortion and a dew drop are not generated. |
