Speckle sizing and sensor dimensions in optical positioning device
First Claim
1. An optical displacement sensor for sensing transverse displacement of a data input device relative to a surface by determining displacement of optical features in a succession of frames, the sensor comprising:
- an illuminator having a coherent light source and illumination optics to illuminate a portion of the surface; and
a detector having imaging optics and at least a first array of photosensitive elements having a periodic distance, wherein the illuminator and the detector are configured to produce on the first array of photosensitive elements an intensity pattern of light reflected from the illuminated portion of the surface, wherein the intensity pattern comprises a plurality of speckles having an average speckle diameter which is between one half and two times the periodic distance of the array.
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Accused Products
Abstract
One embodiment relates to an optical displacement sensor for sensing transverse displacement of a data input device relative to a surface by determining displacement of optical features in a succession of frames. The sensor includes at least a coherent light source, illumination optics to illuminate a portion of the surface, imaging optics, and a first array of photosensitive elements having a periodic distance. The illuminator and the detector are configured to produce on the first array of photosensitive elements an intensity pattern of light reflected from the illuminated portion of the surface. The intensity pattern comprises a plurality of speckles having an average speckle diameter which is between one half and two times the periodic distance of the array.
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Citations
20 Claims
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1. An optical displacement sensor for sensing transverse displacement of a data input device relative to a surface by determining displacement of optical features in a succession of frames, the sensor comprising:
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an illuminator having a coherent light source and illumination optics to illuminate a portion of the surface; and
a detector having imaging optics and at least a first array of photosensitive elements having a periodic distance, wherein the illuminator and the detector are configured to produce on the first array of photosensitive elements an intensity pattern of light reflected from the illuminated portion of the surface, wherein the intensity pattern comprises a plurality of speckles having an average speckle diameter which is between one half and two times the periodic distance of the array. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of sensing movement of a data input device across a surface, the method comprising:
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illuminating a portion of the surface using an illuminator having a coherent light source;
reflecting light from the illuminated portion of the surface;
mapping the light onto an array of detector elements such that the light at the array comprises a speckle pattern with an average speckle diameter;
detecting the speckle pattern by the array, wherein the array comprises a periodicity which is between one half times and two times the average speckle diameter. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An optical positioning device comprising:
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a laser light source illuminating an area of a surface with light of a wavelength;
a detector including a first array having a periodic distance in a first dimension; and
optics comprising a numerical aperture in the first dimension so as to map a speckle pattern with an average speckle diameter in the first dimension from the illuminated area to the detector, wherein the numerical aperture in the first dimension is between one half times and two times the wavelength divided by the periodic distance in the first dimension. - View Dependent Claims (19, 20)
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Specification