Ultrasonic length measuring apparatus and method for coordinate input

• US 20030144814A1
• Filed: 01/30/2003
• Published: 07/31/2003
• Est. Priority Date: 01/31/2002
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Fujii, Akira, Sekiguchi, Hidenori, Hama, Soichi
• Granted Patent: US 6,944,557 B2
• Time in Patent Office: Days
• US Class Current: 702/159
• CPC Class Codes: G06F 3/03545 Pens or stylus
• 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

Abstract

An ultrasonic length measuring apparatus measures the number of times of crossing of the waveform of an ultrasonic wave signal with the threshold value, detects the crossing timing at, for example, the waveform having the maximal amplitude after a predetermined number of times counting from a crossing point crossing first, measures the time period from the transmission start of the ultrasonic wave by the transmission unit to the detected crossing timing and calculates the length based on the time measured. A coordinate inputting apparatus comprises a pen for transmitting an ultrasonic wave and a coordinate inputting apparatus for inputting coordinate positions of the pen based on a propagation time of the ultrasonic wave transmitted by the pen and received by a plurality of ultrasonic wave receivers and the receiver comprises at least a pair of ultrasonic receivers for receiving the ultrasonic wave transmitted by the pen and a clip mechanism for pinching a corner of a sheet. Malfunctioning due to the sound of collision generated by the contact of pen by delaying the transmission timing of the signal from the pen-shaped mover.

Claims

1. An ultrasonic length measuring apparatus comprising:

a transmission unit for transmitting an ultrasonic wave;

at least one receiving unit for receiving an ultrasonic wave and converting it into an electric signal;

a timing detection unit for measuring the number of times of the crossing of the waveform of the received ultrasonic wave signal from the receiving unit over a predetermined threshold value and for detecting a crossing timing after predetermined times from a crossing point of a first crossing;

a time measuring unit for measuring the time period from the start of transmission of the ultrasonic wave by the transmission unit to the crossing timing detected; and

a length measuring unit for calculating a length based on the time measured.

3. An ultrasonic length measuring apparatus according to claim 1 or 2, wherein the crossing point after predetermined times is a crossing point of a vibration having the maximal amplitude of the waveform of the received ultrasonic wave with a threshold value or a crossing point of the vibration one vibration immediately before or after the above vibration with the threshold value.

4. An ultrasonic length measuring apparatus according to claim 1 or 2, wherein the crossing point after predetermined times is a crossing point of the nth vibration of the waveform of the received ultrasonic wave with a threshold value or a crossing point of the n±

1th vibration with the threshold value when the integer Q-value of the receiving unit is n.

7. An ultrasonic length measuring apparatus according to claims 1 and 2, wherein

the transmission unit comprises a transmission notifying unit which issues electromagnetic waves in synchronism with the start of transmission of ultrasonic waves, and wherein

the time measuring unit receives a beam or electromagnetic wave from the transmission notifying unit, and detects a transmission starting timing of the ultrasonic wave.

8. An ultrasonic length measuring apparatus according to any one of claims 1 to 7, wherein

the apparatus comprises at least two (2) systems of the receiving unit, the timing detection unit, the time measuring unit and the length measuring unit, and further comprises a coordinate measuring unit for calculating the position of the transmission unit as two (2)-dimensional coordinates based on two (2) lengths obtained by each of the length measuring unit.

2. An ultrasonic length measuring apparatus comprising:

a transmission unit for transmitting an ultrasonic wave;

at least one receiving unit for receiving an ultrasonic wave and converting it into an electric signal;

a timing detection unit for measuring the number of times of the crossing of the waveform of the received ultrasonic wave signal from the receiving unit over a predetermined threshold value and for detecting each crossing timing for predetermined times from the crossing point after predetermined times from the crossing point of first crossing;

a time measuring unit for measuring the time period from the start of transmission of the ultrasonic wave by the transmission unit to the each crossing timing detected, and obtaining the arithmetic mean of each time measured; and

a length measuring unit for calculating a length based on the time obtained as the arithmetic mean.

5. An ultrasonic length measuring apparatus according to claim 2, wherein

the timing detection unit measures the number of times of crossing of the waveform of the received ultrasonic wave received by the receiving unit, with the threshold value with the threshold value set on both of the polarities relative to the center of the vibration, and detects each crossing timing for a predetermined number of times from the crossing point of both of the polarities after predetermined times counting from the crossing point of the first crossing, and wherein

the time measuring unit obtains the time by measuring and obtaining the arithmetic mean of each of the time from the start of transmitting the ultrasonic wave by the transmission unit to each detected crossing timing of both polarities.

6. An ultrasonic length measuring apparatus according to claims 2 and 5, wherein

the timing detection unit measures the number of times of crossing at the rises and fall-downs of the waveform of the received ultrasonic wave received by the receiving unit, with a predetermined threshold, and detects each crossing timing for a predetermined number of times after a predetermined number of times counting from the crossing point of the first crossing, and wherein

the time measuring unit obtains the time obtained by measuring each time period from the start of transmission of the ultrasonic wave to each crossing timing of the detected rises and fall-downs and obtaining their arithmetic mean.

9. An ultrasonic length measuring method comprising:

a transmission step transmitting an ultrasonic wave;

a receiving step receiving an ultrasonic wave by use of at least one receiving unit and converting the ultrasonic wave into an electric signal;

a timing detection step measuring the number of times of the crossing of the waveform of the received ultrasonic wave signal over a predetermined threshold value and detecting a crossing timing after predetermined times from a crossing point of a first crossing;

a time measuring step measuring the time period from the start of transmission of the ultrasonic wave to the crossing timing detected; and

a length measuring step calculating a length based on the time measured.

10. An ultrasonic length measuring method comprising:

a transmission step transmitting an ultrasonic wave;

a receiving step receiving an ultrasonic wave by use of at least one receiving unit and converting the ultrasonic wave into an electric signal;

a timing detection step measuring the number of times of the crossing of the waveform of the received ultrasonic wave signal over a predetermined threshold value and for detecting each crossing timing for predetermined times from the crossing point after predetermined times from the crossing point of first crossing;

a time measuring step measuring the time period from the start of transmission of the ultrasonic wave to the each crossing timing detected, and obtaining the arithmetic mean of each time measured; and

a length measuring step calculating a length based on the time obtained as the arithmetic mean.

11. An ultrasonic length measuring method according to claim 9 or 10, wherein the crossing point after predetermined times is a crossing point of a vibration having the maximal amplitude of the waveform of the received ultrasonic wave with a threshold value or a crossing point of the vibration one vibration immediately before or after the above vibration with the threshold value.

12. An ultrasonic length measuring method according to claim 9 or 10, wherein the crossing point after predetermined times is a crossing point of the nth vibration of the waveform of the received ultrasonic wave with a threshold value or a crossing point of the n±

1th vibration with the threshold value when the integer Q-value of the receiving step is n.

13. An ultrasonic length measuring method according to claim 10, wherein

the timing detection step measures the number of times of crossing of the waveform of the received ultrasonic wave with the threshold value with the threshold value set on both of the polarities relative to the center of the vibration, and detects each crossing timing for a predetermined number of times from the crossing point of both of the polarities after predetermined times counting from the crossing point of the first crossing, and wherein

the time measuring step obtains the time by measuring and obtaining the arithmetic mean of each of the time from the start of transmitting the ultrasonic wave to each detected crossing timing of both polarities.

14. An ultrasonic length measuring method according to claims 10 and 13, wherein

the timing detection step measures the number of times of crossing at the rises and fall-downs of the waveform of the received ultrasonic wave with a predetermined threshold, and detects each crossing timing for a predetermined number of times after a predetermined number of times counting from the crossing point of the first crossing, and wherein

the time measuring step obtains the time obtained by measuring each time period from the start of transmission of the ultrasonic wave to each crossing timing of the detected rises and fall-downs and obtaining their arithmetic mean.

15. A method according to claim 9 or 10, wherein the time measurement step detects the transmission start timing by receiving a beam or an electromagnetic wave radiated from the transmission unit in synchronism with the ultrasonic wave transmission start.

16. A method according to any one of claims 9 to 15, wherein the method further comprises a coordinate measurement step for calculating a transmission position as a two (2)-dimensional coordinate based on the two lengths obtained in the timing detection step, the time measurement step and the length measurement step for the waveform of the received ultrasonic wave received by at least two (2) systems of the receiving unit.

17. A coordinate inputting apparatus comprising:

a pen transmitting an ultrasonic wave; and

a receiver for receiving the ultrasonic wave transmitted from the pen by at least a pair of ultrasonic wave receivers and for inputting a coordinate position of the pen based on the propagation time periods of the ultrasonic wave received respectively by each of the ultrasonic wave receivers;

wherein

the receiver includes;

a plurality of ultrasonic wave receivers for receiving the ultrasonic wave transmitted from the pen; and

a clip mechanism for pinching a corner of a predetermined sheet.

18. An apparatus according to claim 17, wherein the clip mechanism is fixedly attached to a plane-shaped board loaded with a sheet for writing with the pen.

19. An apparatus according to claims 17 and 18, wherein the pen has an infrared ray transmitter for transmitting infrared ray pulses and the receiver further comprises an infrared ray receiver for receiving as a synchronous signal the infrared ray pulses transmitted from the infrared ray transmitter.

20. An apparatus according to any one of claims 17, 18 and 19, wherein the receiver is fixed on the sheet at a position such that an angle is formed by a line connecting a plurality of the receivers and the upper edge of the sheet is in the range of 30 to 60 degrees.

21. An apparatus according to any one of claims 17 to 20, wherein a flexible edge portion set in a direction of approximately 90 degrees pressing a corner of the sheet on either one (1) of the pinching faces of the clip mechanism.

22. An apparatus according to any one of claims 17 to 21, wherein denoting a arrangement spacing of a pair of the ultrasonic wave receivers to each other as W and the length of the diagonal of the sheet being the writing area of the pen as P, the arrangement spacing W of the ultrasonic wave receivers is set such that W is larger than 0.0002P² and smaller than 0.002P².

23. An apparatus according to any one of claims 17 to 21, wherein the direction of the strongest directionality of the ultrasonic wave receiver is set such that the angle formed by the direction and the upper edge of the area for writing of the sheet is in the range of 30 to 60 degrees.

24. A position detecting apparatus comprising:

a mover including means for detecting contacts and means for transmitting intermittently a synchronous signal and length measurement signal having propagation velocities different from each other;

a length calculation unit for receiving these synchronous signal and length measurement signal and for calculating from the difference of receiving timings between these signals the each propagation length of the length measurement signal from the mover to each of a plurality of the predetermined fixed position;

a position calculation unit for calculating the position of the mover from the relative position relationship of a plurality of these propagation length and a plurality of the fixed positions; and

a delay unit for delaying for a predetermined time the transmission start time of the length measurement signal transmitted intermittently by means for transmitting the length measurement signal.

25. An apparatus according to claim 24, wherein the length measurement signal comprises an ultrasonic wave signal and the predetermined time is determined with the time that has passed until echoes generated when the mover and the contact face contacts automatically ceases.

26. A position detecting apparatus comprising:

a mover including means for detecting contacts and means for transmitting intermittently a synchronous signal and length measurement signal having propagation velocities different from each other;

a length calculation unit for receiving synchronous signal and length measurement signal and for calculating from the difference of receiving timings between these signals the each propagation length of the length measurement signal from the mover to each of a plurality of the predetermined fixed position;

a position calculation unit for calculating the position of the mover from the relative position relationship of a plurality of these propagation length and a plurality of the fixed positions; and

a signal processing unit for ignoring data produced by a signal transmitted at the first of a stroke among length measurement signals produced by the stroke of contact of the mover with the contact face.

27. An apparatus according to claim 26, wherein the signal processing unit ignoring the data produced by the signal transmitted first judges the end of the previous stroke by detecting the irregularity of a transmission interval of the synchronous signal transmitted intermittently.

28. An apparatus according to claim 26, wherein

the mover includes means for transmitting a signal indicating a cease of contact stroke, and wherein

the signal processing unit for ignoring the data produced by the signal transmitted first judges the end of the previous stroke by the detected signal from the stroke cease detection unit.

29. A position detecting apparatus comprising:

a mover comprising a detector for detecting contacts and transmitter for transmitting intermittently a synchronous signal and a length measurement signal having propagation velocities different from each other;

a length calculation unit for receiving the synchronous signal and the length measurement signal and for calculating from the difference of the receiving timings between these signals each propagation length of the length measurement signal from the mover to each of a plurality of the predetermined fixed positions; and

a position calculation unit for calculating the position of the mover from the relative position relationship of a plurality of the propagation length and a plurality of the fixed positions;

wherein

the length calculation unit comprises a signal identifying unit for identifying the length measuring signal.

30. An apparatus according to claim 29, wherein the length measurement signal is constituted of an ultrasonic wave and the signal identifying unit for identifying the length measuring signal has a configuration in which the sound of collision generated when the mover and the contact face contact is distinguished from the ultrasonic length measurement signal.

31. An apparatus according to claim 30, wherein the signal identifying unit for identifying the length measurement signal has a configuration in which the length measurement signal is identified by measuring the period of the received sonic wave.