| 摘要 |
<p>A conversion arrangement for mounting optical units on a camera such as a film or television camera has a generally cylindrical mounting body (12, 14) for attachment to the camera body, a generally cylindrical carrier (B) for attachment to the optical unit, the carrier being coaxially coupled to the mounting body for axial mouvement relative to the mounting body, and a focusing ring (22) which is coaxial with and coupled to both the mounting body (12, 14) and the carrier (B). The focusing ring is rotatable relative to the mounting body and carrier to move the carrier axially of the mounting body to focus the optical unit. Backflash during focusing is reduced to nil or negligible proportions by use of a gapped movement ring (34) which has a radially outer screw-thread engaging a cooperating screw-thread in a radially inner surface of the focusing ring. The movement ring (34) is secured against axial and rotational movement relative to the carrier (B) but is biased radially outwardly into positive engagement with the focusing ring. This avoids the need for very precise machining of the screw-threads on the focusing ring (22) and movement ring (34).</p> |
