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Auto focusing mechanism of surveying instrument

  • US 20060192074A1
  • Filed: 12/28/2005
  • Published: 08/31/2006
  • Est. Priority Date: 02/25/2005
  • Status: Active Grant
First Claim
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1. An auto focusing mechanism for use with a surveying instrument equipped with a telescope having a collimating optical system that includes, between an objective lens and an eyepiece thereof, a focusing plate and a focusing lens for forming on said focusing plate an image of a staff serving as a (targeted) collimating object, said staff having thereon multiple pattern marked at equal intervals, said auto focusing mechanism adapted to automatically focus said telescope on said staff, said auto focusing mechanism comprising:

  • drive means for moving said focusing lens in the direction of the optical axis of said collimating optical system;

    position detection means for detecting the position of said focusing lens in said collimating optical system;

    photoelectric conversion means for converting into an electric signal the image formed on said focusing plate;

    frequency detection means for detecting the frequencies of said electric signal outputted from said photoelectric conversion means;

    distance calculation means for calculating the distance from said telescope to said staff based on the output signal received from said photoelectric conversion means, said distance calculation means adapted to monitor the position of said focusing lens detected by said position detection means and the frequencies detected by said frequency detection means to thereby determine said distance when a particular frequency for a focusing position is detected by said frequency detection means during a process of varying the position of said focusing lens; and

    drive control means for controlling said drive means to position said focusing lens at a focusing position based on the distance calculated by said distance calculation means and the position detected by said position detection means.

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