1. Field of the Invention
This invention relates to an optical device such as lens barrels used in image pickup devices, and more particularly to a support mechanism for supporting the optical device.
2. Prior Art
Conventionally, an image pickup device has been proposed which is provided with a zoom mechanism having lens barrels composed of a fixed barrel rigidly fixed to the body of the image pickup device and having a cam groove formed in an inner peripheral surface thereof, and a moving cam ring fitted in the cam groove, wherein the moving cam ring is driven for rotation by a motor so as to move a zoom lens.
In the image pickup device of this kind, the moving cam ring is supportedly fitted in the cam groove of the fixed barrel only by means of three followers formed with tapers.
Therefore, when an external force, e.g. an impact, is applied to the lens barrel in an extended position, there is a fear that the moving cam ring becomes disengaged from the cam groove of the fixed barrel.
One way to solve this problem may be to employ a method of using followers with no tapers for supporting the moving cam ring in the fixed barrel. This method, however, has the disadvantage that the lens barrel can be broken, although disengagement of the moving cam ring can be prevented. Further, another problem may arise, that is, the moving cam ring cannot be centered.