| 摘要 |
PURPOSE:To increase a cooling effect by providing an objective lens, driving coil and optical element in a sealed case and by sealing a gas having a specific thermal conductivity at ordinary temperature and normal pressure as lower limit in the sealed case. CONSTITUTION:An objective lens 1, elastic body 4, and cover glass 8 arranged in a carriage 3 are arranged in a case 9 completely sealed by the carriage 3. A gas such as hydrogen gas (1815X10<-4>Wm<-1>K<-1>) or helium gas (1499X10<-4>Wm<-1>K<-1>) being higher in thermal conductivity than the air (265X10<-4>Wm-1K<-1>) and having a thermal conductivity of 260X10<-4>Wm<-1>K-1 as lower limit is sealed in this case 9. The thermal conductivity of the gas sealed in the case 9 is as high as about 7 times that of air in the case of hydrogen gas and 6 time that of air in the case of helium gas. Therefore, the heat of a driving coil 5 is quickly transmitted to the gas within the case 9 and the heat of the gas is transmitted to the case 9. Because the case 9 has a surface area much larger than that of the driving coil 5, it can quickly dissipate the heat to the outside. |
