| 摘要 |
PURPOSE:To effectively adjust the pressure difference between the inside and outside of a lens barrel so as to obtain a stable optical performance by providing an extending and contracting member which is deformed under a pressure to part of the lens barrel. CONSTITUTION:An extending and contracting member 5 is composed of a thin film of vinyl, etc., having a good contraction and expansion properties and supported by a supporting member 6 provided on the periphery of the hole section 7 of a lens barrel 2. When a difference is produced between the air pressure PI in the lens space 8 of the barrel 2 and the external atmospheric pressure P0 due to the variation of the atmospheric pressure or the internal pressure associated with the variation of the internal temperature, the member 5 is deformed in corresponding to the pressure difference. As the member 5 is deformed, the enclosed volume in the sealed lens space 8 varies and the deformation of the member 5 continues until the internal pressure PI becomes equal to the external pressure P0. Therefore the internal pressure PI of the lens space 8 is balanced with the external atmospheric pressure P0. 2'. |
