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Speckle navigation system

  • US 7,737,948 B2
  • Filed: 12/20/2005
  • Issued: 06/15/2010
  • Est. Priority Date: 12/20/2005
  • Status: Active Grant
First Claim
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1. A method of sensing relative movement between a data input device and a surface by determining displacement of optical features in a succession of images of the surface, the method comprising:

  • emitting coherent light from a laser;

    collimating the coherent light so as to form a collimated illumination beam with a predetermined diameter, D, and is transmitted to the surface at a normal angle thereto;

    generating a speckle pattern by impingement of the coherent light from the collimated illumination beam on the surface; and

    detecting the images of the surface using a sensor array comprising a comb array,wherein the laser and the sensor array are both configured on a same planar substrate that is configured to lie parallel to the surface, and the predetermined diameter, D, of the collimated illumination beam satisfies an equation D=(h λ

    )/(ξ

    Λ

    cos2θ

    ), wherein h is a height from the planar substrate to the surface, λ

    is a wavelength of the coherent light, ξ

    is a fraction between 0.25 and 0.5, Λ

    is a period of the comb array, and θ

    is an angle subtended by the beam from a point on the sensor.

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