Ultrasonic length measuring apparatus and method for coordinate input
First Claim
1. An ultrasonic length measuring apparatus comprising:
- a transmission unit for transmitting an ultrasonic wave signal;
at least one receiving unit for receiving the ultrasonic wave signal and converting it into an electrical signal;
a timing detection unit for measuring a number of times a waveform of the ultrasonic wave signal received by the receiving unit crosses a predetermined threshold value, for detecting a first crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a first time, and for detecting a crossing timing corresponding to a second crossing point when the ultrasonic wave signal crosses the predetermined threshold value a predetermined number of times after the first crossing point;
a time measuring unit for measuring a time period from a start of transmission of the ultrasonic wave signal by the transmission unit to the crossing timing detected; and
a length measuring unit for calculating a length based on the measured time period.
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Accused Products
Abstract
An ultrasonic length measuring apparatus measures the number of times a waveform of an ultrasonic wave signal crosses a threshold value, detects the crossing timing at, for example, a waveform having a maximal amplitude after a predetermined number of times counting from a first crossing point, 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 includes 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. The receiver includes at least a pair of ultrasonic receivers for receiving the ultrasonic wave transmitted by the pen.
34 Citations
16 Claims
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1. An ultrasonic length measuring apparatus comprising:
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a transmission unit for transmitting an ultrasonic wave signal;
at least one receiving unit for receiving the ultrasonic wave signal and converting it into an electrical signal;
a timing detection unit for measuring a number of times a waveform of the ultrasonic wave signal received by the receiving unit crosses a predetermined threshold value, for detecting a first crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a first time, and for detecting a crossing timing corresponding to a second crossing point when the ultrasonic wave signal crosses the predetermined threshold value a predetermined number of times after the first crossing point;
a time measuring unit for measuring a time period from a start of transmission of the ultrasonic wave signal by the transmission unit to the crossing timing detected; and
a length measuring unit for calculating a length based on the measured time period. - View Dependent Claims (3, 4, 7, 8)
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2. An ultrasonic length measuring apparatus comprising:
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a transmission unit for transmitting an ultrasonic wave signal;
at least one receiving unit for receiving the ultrasonic wave signal and converting it into an electrical signal;
a timing detection unit for measuring a number of times a waveform of the ultrasonic wave signal received by the receiving unit crosses a predetermined threshold value, for detecting a first crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a first time, for detecting a second crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a predetermined number of times after the first crossing point, and for detecting each crossing timing corresponding to the ultrasonic wave signal crossing the predetermined threshold value a predetermined number of times after the second crossing point;
a time measuring unit for measuring time periods from a start of transmission of the ultrasonic wave signal by the transmission unit to each crossing timing detected, and obtaining an arithmetic mean of each time period measured; and
a length measuring unit for calculating a length based on the time obtained as the arithmetic mean. - View Dependent Claims (5, 6)
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9. An ultrasonic length measuring method comprising:
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transmitting an ultrasonic wave signal;
receiving the ultrasonic wave signal by use of at least one receiving unit and converting the ultrasonic wave signal into an electrical signal;
detecting a number of times a waveform of the received ultrasonic wave signal crosses over a predetermined threshold value, detecting a first crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a first time, and detecting a crossing timing corresponding to a second crossing point when the ultrasonic wave signal crosses the predetermined threshold value a predetermined number of times after the first crossing point;
measuring a time period from a start of transmission of the ultrasonic wave signal to the crossing timing detected; and
calculating a length based on the time period measured.
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10. An ultrasonic length measuring method comprising:
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transmitting an ultrasonic wave signal;
receiving an ultrasonic wave signal by use of at least one receiving unit and converting the ultrasonic wave signal into an electrical signal;
detecting a number of times a waveform of the received ultrasonic wave signal crosses a predetermined threshold value, detecting a first crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a first time, detecting a second crossing point corresponding to the ultrasonic wave signal crossing the predetermined threshold value a predetermined number of times after the first crossing point, and detecting each crossing timing corresponding to the ultrasonic wave signal crossing the predetermined threshold value a predetermined number of times after the second crossing point;
measuring a time period from a start of transmission of the ultrasonic wave signal to each crossing timing detected, and obtaining an arithmetic mean of each time period measured; and
calculating a length based on the time obtained as the arithmetic mean. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification