Method and apparatus for tracking a hand-held writing instrument with multiple sensors that are calibrated by placing the writing instrument in predetermined positions with respect to the writing surface
First Claim
1. A method comprising:
- obtaining sensor readings for each of a plurality of predefined positions of a writing instrument generating a mapping of sensor outputs to writing instrument positions based, at least in part, on the sensor readings at the plurality of predefined positions with respect to a writing surface; and
generating a mapping of possible sensor outputs to possible writing instrument positions comprises determining a polynomial approximation of future writing instrument positions corresponding to future sensor outputs based on sensor outputs at the predetermined positions, wherein the polynomial approximation includes the sensor outputs for each predefined position.
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Accused Products
Abstract
One embodiment of the writing instrument described herein comprises a pen-like device containing three accelerometers and three gyroscopes. Data from these sensors are processed via an Euler transform. Prior to using the writing instrument, the user holds the writing instrument in multiple predefined positions and sensor readings are taken. The sensor readings are mapped to the corresponding predefined positions. In addition, the sensor readings are compared to expected sensor readings to compensate for environmental variations such as altitude or temperature as well as for the possible tilt of a writing surface. The sensor readings are interpolated to map sensor readings other than those at the predefined positions to other writing instrument positions. When the user writes with the writing instrument, sensor outputs are used to track the writing instrument to define strokes made by the user. The data describing the strokes may be stored or processed to accomplish a variety of tasks including faxing a message, recording information, etc.
301 Citations
17 Claims
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1. A method comprising:
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obtaining sensor readings for each of a plurality of predefined positions of a writing instrument generating a mapping of sensor outputs to writing instrument positions based, at least in part, on the sensor readings at the plurality of predefined positions with respect to a writing surface; and
generating a mapping of possible sensor outputs to possible writing instrument positions comprises determining a polynomial approximation of future writing instrument positions corresponding to future sensor outputs based on sensor outputs at the predetermined positions, wherein the polynomial approximation includes the sensor outputs for each predefined position. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising:
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obtaining sensor readings for each of a plurality of predefined positions of a writing instrument with respect to a writing surface; and
generating a mapping of sensor outputs to writing instrument positions based, at least in part, on the sensor readings at the plurality of predefined positions and the elected sensor readings at the plurality of predefined positions with respect to the writing surface, wherein generating a mapping of possible sensor outputs to possible writing instrument positions comprises;
mapping a first voltage output by a first sensor when the writing instrument is in a first predetermined position with respect to the writing surface; and
mapping a second voltage output by a second sensor when the writing instrument is in a second predetermined position with respect to the writing surface; and
mapping sensor output voltages between the first voltage and the second voltage to positions of the writing instrument between the first predetermined position and the second predetermined position. - View Dependent Claims (8, 9, 10, 11, 12, 13)
mapping a third voltage output by a third sensor when the writing instrument is in a third predetermined position with respect to the writing surface; and
mapping sensor output voltages between the second voltage and the third voltage to positions of the writing instrument between the second predetermined position and the third predetermined position.
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9. The method of claim 8, wherein the third predetermined position is at a second right angle to the second predetermined position and at a third right angle to the first predetermined position.
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10. The method of claim 8 wherein the third predetermined position a third accelerometer is substantially perpendicular to gravity.
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11. The method of claim 7, wherein the first predetermined position is at a first right angle to the second predetermined position.
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12. The method of claim 7 wherein the first predetermined position a first accelerometer is substantially perpendicular to gravity.
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13. The method of claim 12 wherein the second predetermined position a second accelerometer is substantially perpendicular to gravity.
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14. A system comprising:
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a plurality of accelerometers that generate output voltages in response to accelerations in a corresponding direction; and
a calibration circuit to map the accelerometer output voltages to position data based on accelerometer output voltages when the writing instrument is in a plurality predetermined positions and to generate a mapping of possible sensor outputs to possible writing instrument positions comprises determining a polynomial approximation of future writing instrument positions corresponding to future sensor outputs based on sensor outputs at the predetermined positions, wherein the polynomial approximation includes the sensor outputs for each predefined position. - View Dependent Claims (15, 16, 17)
a first accelerometer that outputs a first voltage when the writing instrument is in a first predetermined position and a second voltage when the writing instrument is in a second predetermined position; and
a second accelerometer that outputs a third voltage when the writing instrument is in the first predetermined position and a fourth voltage when the writing instrument is in the second predetermined position;
wherein the calibration circuit maps the first voltage and the third voltage to the first predetermined position and maps the second voltage and the fourth voltage to the second predetermined position, further wherein the calibration circuit maps voltages between the first voltage and second voltage and voltages between the third voltage and the fourth voltage to positions of the writing instrument between the first predetermined position and the second predetermined position.
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16. The system of claim 15 wherein the first predetermined position is at a first right angle with respect to the second predetermined position.
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17. The system of claim 15 further comprising:
a third accelerometer that outputs a fifth voltage when the writing instrument is in the first predetermined position and a sixth voltage when the writing instrument is in the second predetermined position, and wherein the calibration circuit maps the fifth voltage to the first predetermined position and the sixth voltage to the second predetermined position, and further wherein the calibration circuit maps voltages between the fifth voltage and the sixth voltage to positions between the first predetermined position and the second predetermined position.
Specification