Patent ID: 6960749
Filing Date: 2005-11-01
Classification: G02B

Abstract:
1. An automatic focusing mechanism for mounting on a measuring device having a telescope for sighting a leveling rod with pattern marks marked thereon at an equal pitch between each mark, and a photoelectric device for converting an image sighted by said telescope into an electric signal with a set range to thereby automatically adjust a focus on the leveling rod, said mechanism comprising: driving means for moving a focusing lens of said telescope from one end toward an opposite end of a movable range of said focusing lens; pitch computing means for obtaining only the pitch of the pattern marks of the leveling rod at a position on said photoelectric device which is capable of obtaining the pitch in a state before said focusing lens is focused on the leveling rod to thereby obtain a distance to the leveling rod based only on the pitch obtained by said pitch computing means, without moving the focusing lens in a reciprocating motion around a focus point; and fine adjusting means for moving said focusing lens to a position corresponding to the distance.