Patent ID: 8465709

Claim:
A retention mechanism for an immersion medium, for use in a device which observes/measures a sample by use of an immersion objective lens, the immersion objective lens being formed of a tip portion, a lens ring portion and a lens outer frame, the lens ring portion being formed of an entire surface inclined from the lens of the tip portion to the lens outer frame, the retention mechanism comprising: a bottom plate which has an opening portion to be engaged around the immersion objective lens; a wall plate arranged along a periphery of the bottom plate; an immersion medium supply unit which supplies the immersion medium to the tip portion of the immersion objective lens; and a drip draining unit of the immersion medium provided on the bottom plate in vicinity of the wall plate, which drains a drip of the immersion medium from the tip portion of the immersion objective lens, the bottom plate comprising a first ring-member formed of a first material for retaining the immersion medium and arranged to surround the opening portion, the bottom plate being inclined to make a side of the opening portion higher than a side of the wall plate, an affinity of the first ring-member with the immersion medium being lower than an affinity of an inner member of the first ring-member with the immersion medium.