| 摘要 |
PCT No. PCT/US92/00874 Sec. 371 Date Oct. 4, 1993 Sec. 102(e) Date Oct. 4, 1993 PCT Filed Jan. 31, 1992 PCT Pub. No. WO92/14034 PCT Pub. Date Aug. 20, 1992.An optic system is provided for a down hole camera. The system includes an elongated tubular housing constructed from thermal insulating material. A front lens group and rear lens group are mounted within the housing adjacent opposite ends. The front and rear lens groups are thermally isolated from one another through the provision of two spaced windows therebetween that extend across and seal a light pathway running through the tubular housing. Preferably, the windows are sealingly mounted within the housing so as to define a vacuum chamber therebetween within the wall of the housing.
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