Acoustic writing combination, comprising a stylus with an associated writing tablet

• US 4,246,439 A
• Filed: 04/06/1979
• Issued: 01/20/1981
• Est. Priority Date: 04/10/1978
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Romein, Jacob J.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US06/027,579
• Time in Patent Office: 655 Days
• Field of Search: 178/18, 178/19, 367/129, 367/124, 33/1 P, 33/1 HH, 181/111, 343/112 PT, 340/16 R, 340/17 R, 340/15.5 TN, 346/139 C
• US Class Current: 178/19.02
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/043 using propagating acoustic waves

Abstract

An acoustic writing combination, includes a stylus with an associated writing tablet. The stylus is provided with two ultrasonic sound sources which upon contact of the stylus with the writing tablet emit pulse-shaped sound signals which are picked up by at least two microphones which are located at the edge of the writing tablet. The two sound sources are situated at different distances from the stylus tip and are operated to alternately produce ultrasonic signals. Point-shaped or circular sound sources may be employed. The circular sound sources may then comprise piezo-electric ceramic rings.

Claims

1. An acoustic writing combination comprising, a writing tablet, a stylus movable about a surface of said tablet and provided with first and second ultrasonic sound sources situated on the stylus at different distances from the stylus tip, at least two microphones located at an edge of the writing tablet for receiving sound signals emitted by said first and second sound sources, and means for operating the sound sources to alternately emit pulsatory ultrasonic sound signals.

2. An acoustic writing combination as claimed in claim 1 wherein the first and second sound sources are substantially point-shaped and are located in a straight line with the stylus tip.

3. An acoustic writing combination as claimed in claim 2 wherein each sound source comprises two electrodes adapted to be coupled to a source of voltage and having confronting terminals forming an air gap and between which a spark discharge is produced, said electrodes being located in a plastic block which contains a piezo-electric ceramic insert disposed substantially opposite the location of the spark discharge.

4. An acoustic writing combination as claimed in claim 2 or 3 wherein the distance between the first and second sound sources is substantially equal to the distance between the sound source closest to the stylus tip and the stylus tip.

5. An acoustic writing combination as claimed in claim 1 wherein the sound sources are each circular and comprise first and second piezo-electric ceramic rings having inner and outer surfaces provided with electrodes.

6. An acoustic position indicator for determining the coordinate positions of a writing stylus over the surface of a writing tablet comprising, a writing tablet having first and second orthogonally extending edges and a surface data area, a stylus having a tip at one end adapted for movement adjacent to said surface of the tablet and provided with first and second ultrasonic sound sources each situated on the stylus spaced from and at a different distance from the stylus tip, first and second microphones located along said first and second edges of the tablet for receiving sound signals emitted by said first and second sound sources, and means for operating the sound sources to alternately emit pulsatory ultrasonic sound signals whereby the position of the stylus tip over the tablet data surface can be determined independent of the angle of tilt of the stylus.

7. An acoustic position indicator as claimed in claim 6 wherein the first and second sound sources are substantially point shaped and located along a straight line formed with the stylus tip.

8. An acoustic position indicator as claimed in claim 6 or 7 wherein the distance of the stylus tip to at least one of said microphones is given by the expression:

##EQU2## where;

r=distance between stylus tip and said one microphone

a=distance between stylus tip and said first sound source

b=distance between first and second sound sources

q=distance between first sound source and said one microphone

p=distance between second sound source and said one microphone.

10. An acoustic position indicator as claimed in claim 6 or 7 wherein the first sound source is located intermediate the stylus tip and the second sound source and the distance between the first and second sound sources is substantially equal to the distance between the first sound source and the stylus tip.

11. An acoustic position indicator as claimed in claim 6 or 7 wherein each sound source comprises first and second elongate electrodes supported within a plastic block and having end terminals extending therefrom in confronting relationship to form an air gap to produce a spark discharge, said plastic block including a piezoelectric ceramic member disposed adjacent the air gap so that its dimensions vary in response to an electric field produced by a voltage applied to said electrodes.

12. An acoustic position indicator as claimed in claim 6 wherein said first and second sound sources comprise first and second axially spaced piezoelectric ceramic rings axially aligned with the stylus tip and having inner and outer surfaces provided with electrodes for connection to a source of voltage.

9. An acoustic position indicator as claimed in claim 9 wherein a=b so that r=2q-p.