Tracking motion of a writing instrument
First Claim
Patent Images
1. A method comprisingreceiving, from a writing instrument, light including a modulation frequency,sensing the light at each of two or more sensors each comprising sensitive pixels and generating a sequence of signals representative of the sensed light,determining the modulation frequency from the sensor signals using a phase lock loop,sampling a sensor signal at the times triggered by the phase lock loop, anddetermining a location of the writing instrument based on the sampled sensor signals.
3 Assignments
0 Petitions
Accused Products
Abstract
Motion of a writing instrument is tracked from sensors located in the vicinity. The signals generated from the sensors are processed and used in a wide variety of ways.
183 Citations
40 Claims
-
1. A method comprising
receiving, from a writing instrument, light including a modulation frequency, sensing the light at each of two or more sensors each comprising sensitive pixels and generating a sequence of signals representative of the sensed light, determining the modulation frequency from the sensor signals using a phase lock loop, sampling a sensor signal at the times triggered by the phase lock loop, and determining a location of the writing instrument based on the sampled sensor signals.
-
23. A method comprising
receiving, from a writing instrument, light including periods of lower frequency modulation and bursts of higher frequency modulation, sensing the light at each of two or more sensors each comprising sensitive pixels and generating a sequence of signals representative of the sensed light, using the sensor signal associated with the higher frequency bursts to lock onto a modulation clock, and determining a location of the writing instrument based on the sampled sensor signals.
-
24. Apparatus comprising
a sensor comprising a linear array of sensitive pixels configured to receive light from a moving writing instrument and generate signals representative of the light, optics that are configured to enhance optical power of the light received from the writing instrument and that enable calculation of a position of the light along the linear array of the sensor at a resolution that is higher than a pixel resolution of the sensor along the linear array, and algorithmic processes that enhance immunity of the calculation to instability in the signals and variations in the intensity of the received light, in which the processes determine the integral power of the overall signal distribution on the sensor and calculate a position of the light at a resolution that is higher than the resolution of the pixels based on half of the integral power position.
-
25. Apparatus comprising
a sensor comprising a linear array of sensitive pixels configured to receive light from a moving writing instrument and generate signals representative of the light, optics that are configured to enhance optical power of the light received from the writing instrument and that enable calculation of a position of the light only along the linear array of the sensor at a resolution that is higher than a pixel resolution of the sensor along the linear array, and algorithmic processes that enhance the immunity of the calculation to instability in the signals and variations in the intensity of the received light, in which the processes use a polynomial approximation on the signal distribution and calculate a position of the light at a resolution that is higher than the resolution of the pixels as a function of approximated maximum.
-
33. A method comprising
receiving light from a moving light source on a writing instrument as an indication of a location and path of the writing instrument on a two-dimensional writing surface, sensing the light at each of two or more sensors each comprising a linear array of sensitive pixels and generating a sequence of signals representative of the sensed light, and calculating from the signals positions of the light along the linear array of each of the two or more sensors at a resolution that is higher than a pixel resolution of the sensor by determining the integral power of the overall signal distribution on the sensor, and calculating a position of the light based on half of the integral power position.
-
34. A method comprising
receiving light from a moving light source on a writing instrument as an indication of a location and path of the writing instrument on a two-dimensional writing surface, sensing the light at each of two or more sensors each comprising a linear array of sensitive pixels and generating a sequence of signals representative of the sensed light, calculating from the signals positions of the light along the linear array of each of the two or more sensors at a resolution that is higher than a pixel resolution of the sensor using a polynomial approximation on the signal distribution and calculating the positions as a function of approximated maximum.
-
36. An apparatus comprising
a sensor comprising a linear array of sensitive pixels configured to receive light from a writing instrument moving across an X-Y writing surface, the light including a modulation frequency, a phase lock loop configured to determine the modulation frequency from signals generated by the sensor, and optics that enable calculation of a position of the light along the linear array of the sensor at a resolution that is higher than a pixel resolution of the sensor along the linear array, in which the sensor signal is sampled at times triggered by the phase lock loop.
-
37. An apparatus comprising
a sensor comprising a linear array of sensitive pixels configured to receive light from a writing instrument moving across an X-Y writing surface, the light including periods of lower frequency modulation and bursts of higher frequency modulation, and optics that enable calculation of a position of the light only along the linear array of the sensor at a resolution that is higher than a pixel resolution of the sensor along the linear array, in which the sensor signal associated with the higher frequency bursts is used to lock onto a modulation clock.
Specification