Digital pen using ultrasonic tracking

• US 6,703,570 B1
• Filed: 05/10/2000
• Issued: 03/09/2004
• Est. Priority Date: 05/10/2000
• Status: Expired due to Fees

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Russell, Gregory Fraser, Smith, Barton Allen, Zimmerman, Thomas Guthrie
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): ABDULSELAM, ABBAS I
• Application Number:
  US09/567,720
• Time in Patent Office: 1,399 Days
• Field of Search: 178/19.03, 178/19.05, 178/20.01, 178/19.02, 178/18.01, 178/18.02, 178/18.03, 178/18.04, 345/173, 345/175, 345/177, 345/179, 345/157, 345/158, 345/159, 367/907
• US Class Current: 178/19.03
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G06F 3/0354 with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
• CPC Class Codes: G06F 3/0433 in which the acoustic waves are either generated by a movable member and propagated within a surface layer or propagated within a surface layer and captured by a movable member
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

A digital pen that has a writing tip includes an ultrasonic (US) transducer on a pen body that generates frames of US pulses toward a receiver base in response to an infrared (IR) synchronizing signal from the base. The first pulse of a frame is adjusted by a modulo of the US period τ when the time of arrival (TOA) of the first pulse varies from an expected TOA by more than one-half τ. The TOAs of successive i^th pulses in the frame, which are one wavelength apart from each other, are adjusted forward in time by subtracting from each pulse TOA (i−1)τ, and then several of the adjusted pulse TOAs in a single frame are averaged together to determine a frame TOA. The frame TOAs from plural receivers on the base are then triangulated to determine a pen position for that frame, with the pen positions being input to a handwriting recognition module.

Claims

1. A digital pen system, comprising:

an elongated pen defining a writing tip;

an ultrasonic (US) transducer oriented on the pen to direct frames of US energy outwardly from the pen;

at least two detectors on a base receiving the US energy and outputting plural pulses, each pulse being associated with at least one pulse time of arrival (TOA) relative to at least one detector; and

a processor on the base and receiving signals from the detectors and in response thereto outputting position signals representative of positions of the pen based on at least one frame TOA, the processor determining the frame TOA based at least in part on at least one of;

determining that a TOA of a first pulse in a frame deviates from an expected TOA by at least a predetermined time period, and averaging together plural pulse TOAs associated with pulses in a single frame.

2. The system of claim 1, wherein the US energy defines a US period τ

, and the predetermined time period is at least one-half the US period τ

.

3. The system of claim 2, wherein the processor modifies one of:

the expected TOA, and the TOA of the first pulse, by a modulo of the US period τ

when the predetermined time period is deviated from.

4. The system of claim 1, wherein the processor stores plural frame TOAs, and the processor modifies stored frame TOAs when the TOA of the first pulse is earlier than the expected TOA by at least the predetermined time period.

5. The system of claim 1, wherein the processor subtracts from at least some pulse TOAs a period equal to an integer times τ

to render respective adjusted pulse TOAs.

6. The system of claim 5, wherein the processor averages together at least two adjusted pulse TOAs to establish the frame TOA.

7. The system of claim 3, wherein the processor subtracts from at least some pulse TOAs a period equal to an integer times τ

to render respective adjusted pulse TOAs, the processor averaging together at least two adjusted pulse TOAs to establish the frame TOA.

8. The system of claim 1, further comprising a pen electromagnetic (EM) device on the pen and a base EM device on the base for communicating an EM synchronizing signal therebetween, the US energy being synchronized with the synchronizing signal.

9. The system of claim 8, wherein the base EM device transmits the synchronizing signal to the pen.

10. The system of claim 8, further comprising a contact sensor on the pen for generating a contact signal representative of the tip contacting a surface, the pen generating frames based at least in part on the contact signal.

11. The system of claim 8, further comprising a contact sensor on the pen for generating a contact signal proportional to a pressure on the tip, and the pulse width of the signal generated by the pen EM device is proportional to the contact signal.

12. The system of claim 1, further comprising a grip sensor on the pen and a voltage source on the pen for energizing the US transducer, the grip sensor generating an enabling signal for the voltage source.

13. The system of claim 1, wherein the processor determines whether the expected TOA is within a lull period, and the processor adjusts a frame repetition rate based at least partially thereon.

14. The system of claim 1, wherein at least one pulse is characterized by a leading edge, a center, and a trailing edge, and the pulse TOA associated therewith is a TOA of the center of the pulse.

15. The system of claim 1, wherein the pen is movable against a substrate including visible form fields, the processor having access to an electronically stored facsimile of the substrate for electronically correlating pen positions to virtual fields.

16. The system of claim 1, wherein the detectors are attached to a laptop computer.

17. In a base associated with an ultrasonic (US) pen, a processor including logic for undertaking method acts comprising:

receiving frames of US pulses from the pen; and

for each frame, modifying a time of arrival (TOA) of at least one pulse based on at least one US period to generate a frame TOA.

18. The processor of claim 17, wherein each pulse is associated with at least one pulse time of arrival (TOA) relative to at least one detector on the base, and the method acts undertaken by the logic further comprise:

outputting position signals representative of positions of the pen based on at least one frame TOA, the processor determining the frame TOA based at least in part on at least one of;

determining that a TOA of a first pulse in a frame deviates from an expected TOA by at least a predetermined time period, and averaging together plural pulse TOAs associated with pulses in a single frame.

19. The processor of claim 18, wherein the predetermined time period is at least one-half the US period, and the processor modifies one of:

the expected TOA, and the TOA of the first pulse, by a modulo of the US period when the predetermined time period is deviated from.

20. The processor of claim 18, wherein the method acts undertaken by the logic include storing plural frame TOAs, and modifying stored frame TOAs when the TOA of the first pulse is earlier than the expected TOA by at least the predetermined time period.

21. The processor of claim 18, wherein the method acts undertaken by the logic further include:

subtracting from at least some pulse TOAs a period equal to an integer times (US period) to render respective adjusted pulse TOAs; and

averaging together at least two adjusted pulse TOAs to establish the frame TOA.

22. The processor of claim 18, wherein the method acts undertaken by the logic further comprise:

determining whether the expected TOA is within a lull period; and

adjusting a frame repetition rate based at least partially thereon.

23. The processor of claim 18, wherein at least one pulse is characterized by a leading edge, a center, and a trailing edge, and the pulse TOA associated therewith is a TOA of the center of the pulse.

24. The processor of claim 18, wherein the pen is movable against a substrate including visible form fields, the processor having access to an electronically stored facsimile of the substrate for electronically correlating pen positions to virtual fields.