Optical encoders using non-patterned targets
AssigneeHewlett-Packard Company
InventorsBarclay J. Tullis, Mark T. Smith, Larry McColloch
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Abstract
An optical encoder can detect relative movement of a target without the use of a systematic pattern on the target. Natural features of different areas of the target are imaged by a photosensor array. The photosensor array generates a sequence of data frames of the imaged areas, and a processor processes patterns in the data frames of the imaged areas to detect a relative motion or displacement of the target. The processor can determine incremental relative motion or rate of relative motion.
Claims18
A method of using a photosensor as an encoder for determining an amount of movement of a target of a machine, a surface of the target having a plurality of natural surface features, the method comprising:
- using the photosensor to image the natural surface features of the target, the photosensor generating a sequence of data frames of imaged areas;
- and
- processing the data frames of the imaged areas to detect the amount of movement of the target.
An encoder for detecting a relative motion of a target of a machine, a surface of the target having a plurality of natural surface features, the encoder comprising:
- a two-dimensional photosensor array for imaging the natural surface features of the target, the photosensor array generating a sequence of data frames of imaged areas;
- and
- a processor for processing patterns of the natural features in the sequence of data frames, the processor processing the patterns by correlating the patterns of an aggregate of data frames to compute the motion of the target.
- 11.The encoder of claim 10, further comprising an illuminator for illuminating the imaged areas.
A printer comprising:
- a target;
- means for imaging natural surface features of the target, the imaging means generating a sequence of data frames of the imaged areas;
- and
- means, responsive to the data frames, for processing patterns of the natural surface features to detect a relative movement between the target and the imaging means, the processing means generating a signal indicating relative movement of the target.
- 19.The printer of claim 18, wherein the target is rotatable relative to the imaging means.
The printer of claim 21, wherein imaged areas are illuminated at a grazing angle.
A processor for a device including a photosensor array for receiving an image of at least a portion of a target, the processor comprising:
- means for receiving a plurality of data frames from the photosensor array
- means for detecting a correlation between first and subsequent patterns in the data frames, wherein relative motion of the target causes the subsequent patterns to be updated;
- and
- means for generating a pulse when a correlation is found, the pulse indicating an incremental displacement of the target.
Dependencies are inferred from the claim text.