DEVICE FOR THE ELECTRONIC RECORDING OF THE INSTANTANEOUS LOCATION OF A SENSING PROBE ON THE SURFACE OF A PLATE

• US 3,808,364 A
• Filed: 03/30/1972
• Issued: 04/30/1974
• Est. Priority Date: 03/30/1971
• Status: Expired due to Term

• Current Assignee: Richard Veith
• Original Assignee: Richard Veith
• Inventors: Veith, Richard
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/239,640
• Time in Patent Office: 761 Days
• Field of Search: 178/18,17,20 310/9.8,9.7,3.6 340/146.3SY 346/139C
• US Class Current: 178/18.04
• 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: G06V 10/12 Details of acquisition arrangements; Constructional details thereof
• CPC Class Codes: H01G 7/026 with ceramic dielectric

Abstract

A device for electronically registering the instantaneous location of a probe on the surface of a plate made of piezoelectric material in which essentially strip-shaped electrodes are arranged at least at two sides of one surface of the plate with an electrode or electrodes opposite thereto on the other side of such plate, such strip-shaped electrodes being positioned at an angle with respect to each other. The probe is provided with an electrode at its tip. The device is designed in particular for the instantaneous recording of a character pattern which is written with a probe, such as a pen or stylus. Electric pulses are supplied across the probe electrode and the electrode on the underside of said plate which produce mechanical wave trains whose fronts travel across the plate to the edges having the strip-shaped electrode. The mechanically vibrating piezoelectric material between said strip-shaped electrodes and said opposite electrode on the underside of said plate produces an alternating voltage across each strip-shaped electrode and its opposite electrode. This voltage is transferred to the registering device where the time of its reception and the time of the probe excitation voltage is compared to measure the transit times of the mechanical wave trains. By measuring the relative transit time of each set of electrode pairs, the exact location of the probe at each instant of time is determined.

Claims

1. A piezoelectric sensing device for continuously registering the location of a moving probe over a surface which comprises a plate of piezoelectric material having an area of the surface over which the probe is to be selectively moved, said area having at least two edges angularly oriented with respect to each other, electrodes located at said edges on said surface over which said probe is to be moved, electrode means substantially covering the underside of said plate, whereby electrode pairs are provided by said first mentioned electrodes and said underside electrode, said probe having an electrode formed in its tip, whereby a probe electrode pair is provided by said probe and said underside electrode, means for electrically pulsing said probe electrode to provide a mechanical wave train in said plate, connection lines for transmitting the pulses piezoelectrically produced in said edge located electrode pairs to a registering and storage device.

2. A device according to claim 1 in which said first mentioned electrodes are in the form of strips extending substantially along the length of the edge of said area with which each is associated.

3. A device according to claim 2 in which said electrodes are vapor deposited thin film electrodes.

4. A device according to claim 3 in which a thin film slightly conductive coating overlies substantially all of the upper surface of said plate in a position spaced from said strip electrodes.

5. A device according to claim 4 in which said thin film upper coating has a conductivity satisfied by the equation sigma epsilon /T . d1/d2

6. A device according to claim 1 in which said piezoelectric material plate has a thickness of 0.1 to 1.0 mm.

7. A device according to claim 1 in which said piezoelectric material plate has a thickness of approximately 0.3 mm.

8. A device according to claim 1 in which said piezoelectric plate is vertically polarized in a direction vertical to the surface.

9. A device according to claIm 1 in which said probe is in the form of a ball point pen.

10. A device according to claim 5 in which the thickness of said coating is less than 0.2 mm.

11. A device according to claim 4 in which said coating is integral with said plate.

12. The device of claim 1 in which the voltage pulses applied to said probe are rectangular voltage pulses having a duration between 0.2 and 1 Mu sec.

13. The device of claim 1 in which the voltage pulses applied to said probe are rectangular voltage pulses having a duration of approximately 0.4 Mu sec.

14. The device according to claim 13 in which said wave track is essentially only one oscillation.

15. A device for recording the instantaneous location of a sensing probe on the surface of a plate of piezoelectric or magnetostrictive material in which a succession of internally excited mechanical wave fronts move from the probe towards two adjacent edges in an x- and y-direction, and sensing means at said two edges for generating electric pulses from the mechanical vibration of said plate resulting from the arrival of the wave fronts at the said two adjacent edges, and means for measuring the time of the generated pulses with the time of excitation of said probe.

16. A device for electronic recording of the instantaneous location of a sensing probe on the surface of a plate comprising:

a plate of piezo electric material, two electrodes deposited on the surface, each in the form of a strip extending substantially along two edges of a predetermined writing area of the surface of said plate, a third electrode covering substantially the whole under side of said plate including the area opposite to said writing area as well as opposite to said strip electrodes and forming with said two electrodes, two pairs of electrodes, a probe having a single electrode in its tip and forming with said electrode on the under side of said plate a third pair of electrodes, electric circuit means for producing electric pulses and supplying them to said third pair of electrodes, and means for evaluating signals connected to said two pairs of electrodes to determine the position of said probe from said signals.