| US 7,489,308 B2 | ||
| Determining the location of the tip of an electronic stylus | ||
| Andrew Blake, Stapleford (United Kingdom); Lyndsay Williams, Cambridge (United Kingdom); James Srinivasan, West Yorkshire (United Kingdom); and William Vablais, Springfield, Ill. (US) | ||
| Assigned to Microsoft Corporation, Redmond, Wash. (US) | ||
| Filed on Feb. 14, 2003, as Appl. No. 10/367,485. | ||
| Prior Publication US 2004/0160429 A1, Aug. 19, 2004 | ||
| Int. Cl. G09G 5/00 (2006.01) | ||
| U.S. Cl. 345—179 [345/173; 345/177; 178/18.04; 178/19.02; 178/19.07] | 16 Claims |
| 1. A method comprising:
determining a locus of positions of a first ultrasonic transmitter in an electronic stylus relative to a given reference point;
determining a locus of positions of a second ultrasonic transmitter in the electronic stylus relative to the given reference
point; and
determining a position of a writing tip in the electronic stylus relative to the given reference point using the determined
locus of positions of the first ultrasonic transmitter, determined locus of positions of the second ultrasonic transmitter,
and relative positions of the first ultrasonic transmitter, the second ultrasonic transmitter, and the writing tip within
the stylus, wherein determining the locus of positions of the first ultrasonic transmitter comprises:
emitting an electromagnetic signal from an electromagnetic transmitter in the electronic stylus;
receiving the electromagnetic signal at a first electromagnetic receiver;
emitting an ultrasonic signal from the first ultrasonic transmitter;
receiving the ultrasonic signal at a first ultrasonic receiver, wherein the electromagnetic signal specifies from which of
the first and second ultrasonic transmitters the received ultrasonic signal was emitted; and
calculating a distance (d11) between the first ultrasonic transmitter and the first ultrasonic receiver based on a difference in time between when the
electromagnetic signal was received and when the ultrasonic signal was received,
wherein the first ultrasonic transmitter and the second ultrasonic transmitter alternately transmit ultrasonic signals indicating
that the writing tip is in contact with a writing material.
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