| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens, whose service life is prolonged by suppressing photochemical reaction which is caused when microscope inspection and observation are performed by having deep ultraviolet-rays as a light source and preventing the deterioration in the optical performance. SOLUTION: In the microscope objective lens 1 provided with lenses 10-14, lens holding frames 20-24 for holding respective lenses 10-14 and a housing 40 for housing respective lens-holding frames 20-24, nitrogen gas is supplied through a gas tube 50 and a coupling 55 and also the nitrogen gas is exhausted from a gas tube 60 and a coupling 65, so that spaces S1-S4 between the lenses 10-14 are replaced with the nitrogen gas, and then plugs 53 and 63 are closed. When the microscope inspection and observation which have the deep ultraviolet- rays as the light source are performed in this state, the photochemical reaction will be hardly caused between the deep ultraviolet-rays and an optical part at the space at the inside of the objective lens 1, and the lenses 10-14 are prevented from becoming cloudy because impurity due to the photochemical reaction sticks to the surfaces of the lenses 10-14, so that the service life is prolonged, while maintaining prescribed optical performance.
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