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Encoder for providing incremental and absolute position data

  • US 6,175,109 B1
  • Filed: 12/16/1998
  • Issued: 01/16/2001
  • Est. Priority Date: 12/16/1998
  • Status: Expired due to Term
First Claim
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1. An optical encoder for providing absolute and incremental position information of an object which moves along a certain measuring direction, the encoder comprising:

  • a single data track positioned along the measuring direction having a fine incremental track with a defined incremental graduation period and a plurality of separate coarse code tracks overlying said incremental graduation;

    a light source for emitting light in the direction of the data track;

    a first detecting unit arranged with respect to the data track for receiving light modulated by said incremental track;

    wherein said first detecting unit comprises an array of separate photodetectors, each of the photodetectors of said first detecting unit providing phase shifted incremental output signals;

    a second detecting unit arranged with respect to the data track for receiving light modulated by said plurality of code tracks;

    wherein said second detecting unit having a number of separate photodetectors and the number of photodetectors being equal to the number of code tracks;

    wherein the combination of the output signals of the photodetectors of said second detecting unit provides absolute position information.

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