| 摘要 |
PROBLEM TO BE SOLVED: To reduce facility cost by enabling at least the frame of an optical surface plate to be constituted of stainless alloy, aluminum alloy, or the like which is inexpensive and is easily processed. SOLUTION: This optical surface plate 4 mounts a cavity 1, a transmission mirror 5, and a reflecting mirror 6. Here, the frame 11 for reinforcing the main body 2 of the surface plate is made into a watertight hollow structure and is constituted so that cooling water 7 (coolant) can be supplied to or discharged from the passage 11a formed within the frame 11. It is preferable that the frame 11 constituted of aluminum alloy. |
