| 摘要 |
PURPOSE:To protect optical parts against sticking of dust and dirt contained in the ambient atmosphere by utilizing a cylindrical body having double structures to form a toric outflow port and adjusting the quantity of the dry air to be discharged to a specific value. CONSTITUTION:The dry air is supplied to the gap B formed to a circumferential shape through plural pieces of supply ports 6 circumferentially at equal intervals on the outside cylinder 4 having a cylindrical shape so that this dry air leaks from between the open end part of the inside cylinder and the optical parts to fill the inside of the cylindrical body. The dry air forms the flow heading toward the outside over the entire area of the cylindrical body 5 when the flow rate of the dry air is so adjusted that the Reynolds number attains 200<=Re<=500. The stagnation of very slight fine powder is then merely generated in the central part at the outlet of the inside cylinder 5 and the infiltration thereof into the deep inside part is obviated. Sticking of the dust in the ambient atmosphere to the optical parts is thereby averted and the degradation in output and the deterioration of the optical parts are prevented. |
