Stylus position digitizer using acoustic waves
First Claim
1. A device for providing a digital representation of the location of a stylus on a plate, said device comprising:
- a solid plate;
an untethered stylus for introducing a burst of acoustic waves into said plate;
a plurality of detectors positioned on said plate, each of said detectors for detecting the arrival of said burst of acoustic waves introduced into said plate by said stylus;
a first means for determining a difference in the respective arrival times of said burst at individual detectors in a first pair of said detectors; and
a second means for determining a difference in the respective arrival times of said burst at individual detectors in a second pair of said detectors, wherein at least one of said detectors in said second pair of detectors is not included in said first pair of detectors.
2 Assignments
0 Petitions
Accused Products
Abstract
A digitizer uses acoustic waves originating from a stylus to determine the position of the stylus on a plate. The acoustic waves are introduced into the plate from the tip of the stylus and are detected by a plurality of detectors positioned at various points along the periphery of the plate. By sensing differences in the arrival times of the acoustic waves at the detectors, a microprocessor calculates the position of the stylus. In a preferred embodiment using a non-tethered stylus, four detectors are positioned at the corners of a rectangle, and the time differences are used as addresses in a lookup table, which is programmed to contain x and y coordinates corresponding to the time differences, Different embodiments may detect only the "fast" symmetrical waves or only the "slow" antisymmetrical waves generated in the plate, or may use the arrival times of both types of waves to determine the stylus position.
91 Citations
44 Claims
-
1. A device for providing a digital representation of the location of a stylus on a plate, said device comprising:
- a solid plate;
an untethered stylus for introducing a burst of acoustic waves into said plate; a plurality of detectors positioned on said plate, each of said detectors for detecting the arrival of said burst of acoustic waves introduced into said plate by said stylus; a first means for determining a difference in the respective arrival times of said burst at individual detectors in a first pair of said detectors; and a second means for determining a difference in the respective arrival times of said burst at individual detectors in a second pair of said detectors, wherein at least one of said detectors in said second pair of detectors is not included in said first pair of detectors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 32, 33, 34, 35, 36, 37, 38, 39, 44)
- a solid plate;
- 29. The device of claim i wherein said acoustic waves are Lamb waves of the symmetrical mode.
-
40. A device for providing a digital representation of the location of a stylus on a plate, said device comprising:
-
a solid plate; a stylus including a vibrating element; a plurality of acoustic wave detectors located on said plate; a first counter, said first counter being triggered by the arrival of an acoustic wave at one of said detectors in a first pair of said detectors and being stopped by the arrival of said acoustic wave at the other detector in said first pair of said detectors; a second counter, said second counter being triggered by the arrival of an acoustic wave at one of said detectors in a second pair of said detectors and being stopped by the arrival of said acoustic wave at the other detector in said second pair of said detectors, wherein said second pair of said detectors includes at least one of said detectors that is not included in said first pair of said detectors; and a microprocessor connected to said first and second counters, said microprocessor being programmed so as to compute a position of said stylus on said plate. - View Dependent Claims (41, 42)
-
-
43. A method of generating an electrical signal representative of the position of a stylus on a plate, said method comprising the steps of:
-
providing a plate; providing a memory having a plurality of data storage locations, each of said data storage locations being identified by a pair of addresses; programming each of said data storage locations of said memory with coordinates representing a position on said plate; positioning a stylus such that a tip of said stylus is in contact with said plate, a point of contact between said tip and said plate defining a position of said stylus on said plate; generating two binary words approximating the position of said stylus on said plate; removing a predetermined number of bits from each of said binary words, leaving truncated binary words; using said truncated binary words to address a first data storage location in said memory; reading a first set of coordinates stored at said first data storage location, said first set of coordinates defining a first position on said plate; incrementing said truncated binary words to form incremented truncated binary words; using said incremented truncated binary words to address a second data storage position in said memory; reading a second set of coordinates stored at said second data storage location, said second set of coordinates defining a second position on said plate; using the bits removed from each of said binary words to identify, a third position on said plate, said third position representing the position of said stylus on said plate; and generating an electrical signal representative of said third position on said plate.
-
Specification