Encoder for providing incremental and absolute position data
First Claim
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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Accused Products
Abstract
An optical encoder has a single data track which is scanned photoelectrically by a scanning unit. The data track consists of an incremental track and a plurality of overlying code tracks so that it is possible to generate incremental output signals as well as at least coarse absolute positional information by scanning only one track. The scanning unit comprises a first detecting unit with a phased array of photodetectors to scan the incremental graduation. A second detecting unit with a plurality of photodetectors is provided for scanning the code tracks. The code tracks can be used to generate commutation signals for brushless motors.
28 Citations
24 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An optical rotary encoder for providing incremental output signals and commutation output signals suitable for controlling a brushless motor, the encoder comprising:
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a single circular data track arranged on a code wheel, having a fine incremental track with a defined incremental graduation period and three separate concentrically arranged 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;
wherein those photodetectors of said first detecting unit are connected electrically with each other which provide output signals with the same phase relationship;
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 has three separate photodetectors;
wherein the combination of the output signals of the photodetectors of said second detecting unit provides absolute position information within a certain angular range. - View Dependent Claims (19, 20, 21, 22)
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23. An optical encoder for providing absolute and incremental position information of an object which moves along a certain measuring direction, the encoder comprising:
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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 first detecting unit arranged with respect to the data track for receiving light modulated by said incremental track;
a second detecting unit having a number of separate photodetectors and arranged with respect to the data track for receiving light modulated by said plurality of code tracks;
wherein the combination of the output signals of the photodetectors of said second detecting unit provides absolute position information. - View Dependent Claims (24)
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Specification