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Data input device and method for detecting an off-surface condition by a laser speckle size characteristic

  • US 7,221,356 B2
  • Filed: 02/26/2004
  • Issued: 05/22/2007
  • Est. Priority Date: 02/26/2004
  • Status: Expired due to Fees
First Claim
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1. A data input device for use with a tracking surface, said tracking surface having light-scattering properties with respect to said device, said device comprising:

  • a coherent light source for projecting a coherent light beam onto said tracking surface, said tracking surface scattering the coherent light beam striking said tracking surface;

    a detector associated with the coherent light source for detecting at least a portion of said scattered light, said detected portion comprising a speckle pattern; and

    a controller configured to respond to the detected speckle pattern and operate the device in one of a tracking mode and a non-tracking mode depending upon a speckle size characteristic of the detected speckle pattern as determined by said controller, wherein said controller is configured to perform a spatial frequency analysis of said detected speckle pattern to determine said speckle size characteristic.

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