| 摘要 |
PURPOSE:To shorten the time required for focus switching and attain high-accuracy focusing by forming different-pitch grooves which are used for focusing at the time of long focal length and short focal length and for focus switching in a shaft having a feed groove. CONSTITUTION:The cam groove formed in the driving shaft 7 is variable at three positions; and a part C is where an engaging pin 6 moves during the focus switching of a lens barrel, and parts B and A are where the engaging pin 6 moves at the time of short focal length and long focal length respectively. When a motor 9 reverses in the opposite direction of an arrow to reverse the shaft 7, a lens barrel earth plate 2 moves in the opposite direction (backward) of an arrow and the motor 9 is powered off at a break of a pattern detected by a contact piece 23, thereby holding the lens barrel base plate 2 at the position. When the motor 9 is powered on again to rotate normally, the lens barrel base plate 2 enters B and moves. Simultaneously, a specific numbers of pulses are counted by contact pieces 15a and 15b which contact a rotating pulse disk and then the motor 9 is powered off to stop the base plate 2. |
