Coordinate data entry device

• US 6,788,296 B2
• Filed: 06/11/2002
• Issued: 09/07/2004
• Est. Priority Date: 06/13/2001
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ikeda, Masaki, Tasaki, Katsu
• Primary Examiner(s): Chang, Kent
• Application Number:
  US10/167,736
• Publication Number:
  US 20030014138A1
• Time in Patent Office: 819 Days
• Field of Search: 345/173, 345/177, 345/178, 178/18.01, 178/18.02, 178/18.03, 178/18.04, 178/20.01, 178/20.03, 178/20.04
• US Class Current: 345/177
• CPC Class Codes: G06F 3/043 using propagating acoustic waves

Abstract

The present invention provides a coordinate data entry device comprising a plurality of receivers disposed in the vicinity of a board surface, and a position indicator to transmit signals, at least one of which employs ultrasonic waves, to the receivers, thereby detecting the position of the position indicator on the board surface and making the coordinate position thereof available for entry, in which the signal employing ultrasonic waves is transmitted at an arbitrary time interval, and an ultrasonic oscillating circuit transmitting the signal employing ultrasonic waves comprises a resonant circuit formed of an ultrasonic resonator and a coil, which are connected in parallel with each other, and the amplitude of a start current of the ultrasonic resonant circuit is made variable according to the lapse of time, thus allowing the variations in performance of the resonant circuit including the ultrasonic resonator to be smoothed out and making stabilized positional detection possible.

Claims

1. A coordinate data entry device comprising:

a plurality of receivers disposed near a board surface; and

a position indicator to transmit signals, at least one of which employs ultrasonic waves, to said receivers, thereby detecting a position of said position indicator on said board surface and making a coordinate position of said position indicator available for entry,

wherein said signal employing ultrasonic waves is transmitted at an arbitrary time interval,

an ultrasonic oscillating circuit generating said signal employing ultrasonic waves comprises a resonant circuit formed of an ultrasonic resonator and a coil, which are connected in parallel with each other, and

an amplitude of a start current of said resonant circuit is made variable according to a lapse of time.

2. A coordinate data entry device comprising:

a plurality of receivers disposed near a board surface; and

a position indicator to transmit signals, at least one of which employs ultrasonic waves, to said receivers, thereby detecting a position of said position indicator on said board surface and making a coordinate position of said position indicator available for entry,

wherein said signal employing ultrasonic waves is transmitted at an arbitrary time interval,

an ultrasonic oscillating circuit generating said signal employing ultrasonic waves comprises a resonant circuit formed of an ultrasonic resonator and a coil, which are connected in parallel with each other, and

a period of time, during which an electric current flows in said coil, is made variable.

3. The coordinate data entry device according to claim 2, wherein said ultrasonic oscillating circuit comprises said resonant circuit formed of said ultrasonic resonator and coil, which are connected in parallel with each other, and a diode connected in series with said ultrasonic resonant circuit.

4. The coordinate data entry device according to claim 3, wherein an amplitude of a start current of said ultrasonic resonant circuit is made variable by making a period of time, during which an electric current flows in said coil, variable.

5. A coordinate data entry device comprising:

a plurality of receivers disposed near a board surface; and

a position indicator to transmit signals, at least one of which employs ultrasonic waves, to said receivers, thereby detecting a position of said position indicator on said board surface and making a coordinate position of said position indicator available for entry,

wherein said signal employing ultrasonic waves is transmitted at an arbitrary time interval, and

an ultrasonic oscillating circuit transmitting said signal employing ultrasonic waves allows a phase or frequency of said signal employing ultrasonic waves to be switch-selectable at an arbitrary time interval after starting of an ultrasonic oscillation.

6. The coordinate data entry device according to claim 5, wherein said ultrasonic oscillating circuit is revered in phase for every fixed oscillation period.

7. An ultrasonic oscillating circuit comprising:

a resonant circuit for generating a signal employing ultrasonic waves, said resonant circuit including an ultrasonic resonator and a coil coupled in parallel with each other;

a switch coupled to said coil,

said switch causing a resonance start current to flow in said coil for at least one of a plurality of time intervals, said resonance start current having an amplitude,

wherein the resonant circuit generates the signal when the amplitude of the resonance start current reaches a high value, and

wherein the amplitude of the high value of the resonance start current depends upon the length of the at least one of a plurality of time intervals.