| 摘要 |
PROBLEM TO BE SOLVED: To reduce generation of visual field movement due to thermal expansion by detecting temperature around a visual field moving device and of a lens coil and controlling temperature and amount of cooling water. SOLUTION: A circulating device 16 cools in an objective lens part for reducing visual field movement caused by the thermal expansion of a mechanism system accompanied by temperature rise. Rapid control for temperature is, however, difficult because of control accuracy of a temperature sensor 20 and a water temperature control heater (2) 19 provided in a cooling water tank 15, the capacity of the water tank 15, and the like. The terminal voltage of an objective lens 2 is accordingly used as a temperature detecting signal 5, and a temperature control circuit 6 controls opening of a valve 12 for controlling the amount of the cooling water. Otherwise, a temperature control tank 21 is newly provided, and the amount of water and the temperature of the cooling water are controlled, corresponding to temperature change by providing a heater (1) 14 for controlling the water temperature in the water tank 21. The visual field movement due to the thermal expansion generated by fine thermal change can be thereby restricted.
|
