COORDINATE DETECTING DEVICE, WRITING INSTRUMENT, AND COORDINATE INPUTTING SYSTEM

Abstract

A pen includes a first speaker that outputs a first signal and a second speaker that outputs a second signal. The first and second speakers are located away from a tip of the pen at respectively different locations. The second signal is delayed with respect to the first signal by a time shorter than a cycle of the first signal. An interpolation time is set between the times of generation of the first and second signals. Interpolated positions of the first and second speakers at the interpolation time are estimated, and position of the tip of the pen is calculated from the interpolated positions of the first and second speakers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a coordinate inputting system according to a first embodiment of the present invention;

FIG. 2 is a timechart for explaining transmitting timings of infrared pulses and ultrasonic waves from a writing instrument according to the first embodiment of the invention;

FIG. 3 is a block diagram of a coordinate detecting device in the coordinate inputting system according to the first embodiment of the invention;

FIG. 4 is a block diagram of a speaker position detector in the coordinate inputting system according to the first embodiment of the invention;

FIG. 5 is a block diagram of a speaker position interpolator in the coordinate inputting system according to the first embodiment of the invention;

FIG. 6 is a schematic for explaining estimation of a pen tip position by the coordinate inputting system according to the first embodiment of the invention;

FIG. 7 is a diagram of pen-tip interpolation times when the speaker position interpolator interpolates a speaker position in the coordinate inputting system according to the first embodiment of the invention;

FIG. 8 is a diagram of speakers and pen tip coordinates used to calculate the pen tip position from the speaker positions in the coordinate inputting system according to the first embodiment of the invention;

FIG. 9 is a diagram of another example of the estimation of the pen tip position when the writing instrument is rotated at a constant speed, while the pen is tilted and fixed with the pen tip as the center, in the coordinate inputting system according to the first embodiment of the invention;

FIG. 10 is a diagram of another example of the pen-tip interpolation times when the speaker position interpolator interpolates the speaker position in the coordinate inputting system according to the first embodiment of the invention;

FIG. 11 is a diagram of pen-tip position estimation errors caused by an interpolation method used in the coordinate inputting system according to the first embodiment of the invention and a relationship between sampling frequencies and pen-tip position estimation errors according to the present method and a conventional method when a delay time C is 0.5;

FIG. 12 is a diagram of the pen-tip position estimation errors caused by an interpolation method used in the coordinate inputting system according to the first embodiment of the invention and a relationship between a delay (c) and the pen-tip position estimation errors according to the present method and the conventional method when a sampling frequency n is 2;

FIG. 13 is a diagram of the pen-tip position estimation errors caused by an interpolation method used in the coordinate inputting system according to the first embodiment of the invention and a relationship between the delay (c) and the pen-tip position estimation errors according to the present method and the conventional method when the sampling frequency n is 4;

FIG. 14 is a diagram of the pen-tip position estimation errors caused by an interpolation method used in the coordinate inputting system according to the first embodiment of the invention and a relationship between the delay (c) and the pen-tip position estimation errors according to the present method and the conventional method when the sampling frequency n is 8;

FIG. 15 is a diagram of the pen-tip position estimation errors caused by an interpolation method used in the coordinate inputting system according to the first embodiment of the invention and a relationship between the delay (c) and the pen-tip position estimation errors according to the present method and the conventional method when the sampling frequency n is 16;

FIG. 16 is a block diagram of a coordinate detecting device in a coordinate inputting system according to a second embodiment of the invention;

FIG. 17 is a diagram of transmitting timings of infrared pulses and ultrasonic waves from a writing instrument according to the second embodiment of the invention;

FIG. 18 is a block diagram of a frequency detector in the coordinate inputting system according to the second embodiment of the invention;

FIG. 19 is a diagram of a signal inputted into a speaker position interpolator in the coordinate inputting system according to the second embodiment of the invention;

FIG. 20 is a diagram of an estimation of a pen tip position when the writing instrument is rotated at a constant speed, while a pen is tilted and fixed with the pen tip as the center, in a conventional coordinate inputting system; and

FIG. 21 is a diagram of pen-tip interpolation times when the conventional coordinate inputting system interpolates a speaker position.

Claims

1. A coordinate detecting device comprising: a first receiving unit that receives a first signal from a first generating unit and a second signal from a second generating unit, the second signal received at a delayed timing of receiving the first signal;a second receiving unit that is located at a position different from that of the first receiving unit and receives the first signal and the second signal;a position calculating unit that calculates a first position that is a position of the first generating unit based on a time at which the first receiving unit receives the first signal and a time at which the second receiving unit receives the first signal, and calculates a second position that is a position of the second generating unit based on a time at which the first receiving unit receives the second signal and a time at which the second receiving unit receives the second signal;an interpolating unit that calculates an interpolated position of the first generating unit and an interpolated position of the second generating unit from the first position and the second position; andan estimating unit that estimates a position on a predetermined coordinate plane that is away from the first generating unit and the second generating unit based on the interpolated positions of the first generating unit and the second generating unit calculated by the interpolating unit.

2. The coordinate detecting device according to claim 1, wherein the interpolating unit includes an interpolation-time calculating unit that calculates an interpolation time based on times of generation of the first signal and the second signal; andan interpolation-position calculating unit that calculated the interpolated positions of the first generating unit and the second generating unit at the interpolation time.

3. The coordinate detecting device according to claim 1, wherein the interpolating unit calculates a time point between a generation timing of the first generating unit and a generation timing of the second position as the interpolated time point.

4. The coordinate detecting device according to claim 3, wherein the interpolating unit calculates a time point half way between the generation timing of the first generating unit and the generation timing of the second position as the interpolated time point.

5. The coordinate detecting device according to claim 1, further comprising a cycle detecting unit that detects a cycle of the first signal and a cycle of the second signal, wherein the position calculating unit calculates the first position and the second position based on the cycle of the first signal and the cycle of the second signal detected by the cycle detecting unit.

6. The coordinate detecting device according to claim 1, further comprising a third receiving unit that receives a third signal transmitted from a third generating unit located at a position different from that of the first generating unit and the second generating unit, a cycle of the third signal being same as that of the first signal, wherein the coordinate detecting device further includes a resetting unit that resets input of the first signal and input of the second signal when the third receiving unit receives the third signal.

7. The coordinate detecting device according to claim 6, wherein the first signal and the second signal are ultrasonic waves and the third signal is any one of an infrared pulse and an electromagnetic wave.

8. A writing instrument used in a coordinate detecting device, the coordinate detecting device including a first receiving unit that receives a first signal from a first generating unit and a second signal from a second generating unit, the second signal being delayed with respect to the first signal; a second receiving unit that is located at a position different from that of the first receiving unit and receives the first signal and the second signal; a position calculating unit that calculates a first position that is a position of the first generating unit based on a time at which the first receiving unit receives the first signal and a time at which the second receiving unit receives the first signal, and calculates a second position that is a position of the second generating unit based on a time at which the first receiving unit receives the second signal and a time at which the second receiving unit receives the second signal; an interpolating unit that calculates an interpolated position of the first generating unit and an interpolated position of the second generating unit from the first position and the second position; and an estimating unit that estimates a position on a predetermined coordinate plane that is away from the first generating unit and the second generating unit based on the interpolated positions of the first generating unit and the second generating unit calculated by the interpolating unit, the writing instrument comprising: a body having a tip and that can be held by a user;the first generating unit arranged at a position away from the tip of the body and that generates the first signal; andthe second generating unit arranged at a position different from that of the first generating unit and that generates the second signal.

9. The writing instrument according to claim 8, further comprising a cycle adjusting unit that adjusts cycles of generation of the first signal and the second signal.

10. The writing instrument according to claim 8, further comprising: a writing state detecting unit that detects whether the body is being used for writing; anda third generating unit that generates a third signal at same cycle as that of the first signal when the writing state detecting unit judges that the body is being used for writing, whereinthe first generating unit generates the first signal at a timing at which the third generating unit generates the third signal, andthe first signal and the second signal are ultrasonic waves and the third signal is any one of an infrared pulse and an electromagnetic wave.

11. A coordinate inputting system including a writing instrument and a coordinate detecting device that detects pen tip coordinates, wherein the writing instrument includes a body having a tip and that can be held by a user;a first generating unit arranged at a position away from the tip of the body and that generates a first signal; anda second generating unit arranged at a position different from that of the first generating unit and generates a second signal, the second signal being delayed with respect to the first signal, andthe coordinate detecting device includes a first receiving unit that receives the first signal from the first generating unit and the second signal from the second generating unit;a second receiving unit located at a position different from that of the first receiving unit and receives the first signal and the second signal;a position calculating unit that calculates a first position that is a position of the first generating unit based on a time at which the first receiving unit receives the first signal and a time at which the second receiving unit receives the first signal, and calculates a second position that is a position of the second generating unit based on a time at which the first receiving unit receives the second signal and a time at which the second receiving unit receives the second signal;a interpolating unit that calculates an interpolated position of the first generating unit and an interpolated position of the second generating unit from the first position and the second position; andan estimating unit that estimates a position on a predetermined coordinate plane that is away from the first generating unit and the second generating unit based on the interpolated positions of the first generating unit and the second generating unit calculated by the interpolating unit.

12. The coordinate inputting system according to claim 11, wherein the interpolating unit includes an interpolation-time calculating unit that calculates an interpolation time based on times of generation of the first signal and the second signal; andan interpolation-position calculating unit that calculated the interpolated positions of the first generating unit and the second generating unit at the interpolation time.

13. The coordinate inputting system according to claim 11, wherein the interpolating unit calculates a position between the first position and the second position as the interpolated positions of the first generating unit and the second generating unit.

14. The coordinate inputting system according to claim 13, wherein the interpolating unit calculates a position half way between the first position and the second position as the interpolated positions.

15. The coordinate inputting system according to claim 11, wherein the writing instrument further includes a cycle adjusting unit that adjusts cycles of generation of the first signal and the second signal,the coordinate detecting device includes a cycle detecting unit that detects a cycle of the first signal and a cycle of the second signal, andthe position calculating unit calculates the first position and the second position based on the cycle of the first signal and the cycle of the second signal detected by the cycle detecting unit.

16. The coordinate inputting system according to claim 11, wherein the writing instrument includes a writing state detecting unit that detects whether the body is being used for writing; anda third generating unit that generates a third signal at same cycle as that of the first signal when the writing state detecting unit judges that the body is being used for writing, whereinthe first generating unit generates the first signal at a timing at which the third generating unit generates the third signal,the coordinate detecting unit includes a third receiving unit that receives the third signal from the third generating unit, andthe position calculating unit includes a resetting unit that resets input of the first signal and input of the second signal when the third receiving unit receives the third signal.

17. The coordinate inputting system according to claim 16, wherein the first signal and the second signal are ultrasonic waves and the third signal is any one of an infrared pulse and an electromagnetic wave.