| 摘要 |
A lens system comprising a cylindrical carrier for the lens, a body assembly, and a sleeve internally threaded to match external threads of a cylindrical body of the assembly. The lens is carried coaxially inside the carrier which has a helical cam slot and a longitudinal slot. The carrier is held coaxially and slidably within the interior of the cylindrical body. A pin in the body enters the helical slot, and a pin sealed fluid-tight in the sleeve is inserted through a circumferential opening in the cylindrical body and enters the carrier longitudinal slot. The ends of the cylindrical body are sealed fluid-tight with optical windows. The sleeve spans the circumferential opening. The opening and hence the interior of the body assembly is sealed from external fluid by a suitable lubricant between the external threads of the body and the internal threads of the sleeve. By turning the sleeve, the carrier and lens are cammed longitudinally in the body.
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