Touch panel input device and control method thereof

A touch panel input device comprising:

• a panel on which acoustic waves are propagated;
• a surface acoustic wave generation means having an emission transducer for generating surface acoustic waves;
• a plurality of surface acoustic wave reflective arrays provided along the vertical and horizontal axes in circumferential portions on said panel for reflecting at least portions of the surface acoustic waves;
• touch detection means having a reception transducer for receiving the surface acoustic waves and for converting multiple surface acoustic waves that have been reflected by said plurality of reflection arrays into an electrical signal,
• wherein said touch detection means comprises a waveform comparison means for outputting a differential waveform by comparing a waveform of the electrical signal at a time when the contact object is out of contact with said panel, with a waveform of said electrical signal at a time when the object is in contact with said panel;
• threshold level comparison means for comparing the differential waveform with a predetermined threshold level;
• waveform correction means obtaining a corrected waveform by correcting a portion of the differential waveform in proximity of the threshold level;
• position calculation means for calculating a position that the object is in contact with said panel;
• and
• width calculation means for calculating a width of the object of the touched position on said panel in accordance of two intersections of the corrected waveform and the threshold level.

A control method for a touch panel input device having a panel on which an acoustic wave is propagated comprising the steps of:

• generating surface acoustic waves;
• forming reflective arrays along vertical and horizontal axes in circumferential portions on the panel for reflecting at least part of the surface acoustic waves;
• receiving the surface acoustic waves and converting the received surface waves into an electrical signal;
• providing a reference electrical signal indicative of the object not in contact with the panel;
• calculating a differential waveform by comparing the waveform of the electrical signal when the object is in contact, with the reference electrical signal;
• comparing a threshold level comparison with the differential waveform;
• forming a corrected waveform by correcting a part of the differential waveform that is near the threshold level;
• and
• calculating a position of contact of the object in accordance with two intersections of the corrected waveform and the threshold level.

An electronic messaging board comprising:

• a writing surface;
• and
• a touch panel input device disposed on said writing surface comprising:
• a panel capable of propagating surface acoustic waves and in which surface acoustic wave attenuation is caused by a object in contact with said panel;
• emission circuit means for outputting a surface acoustic wave drive;
• an emission transducer for emitting surface acoustic waves in said panel in accordance with the surface wave drive outputted from said emission circuit means;
• a reception transducer for receiving surface acoustic waves in said panel and for outputting a received acoustic signal;
• and
• reception circuit means for receiving the received acoustic wave signal from said reception transducer to detect a position at which the received acoustic wave is attenuated as indicative of a position that the object contacts said panel;
• and
• controller means for controlling said emission circuit and said reception circuit means, comprising:
• computing means for computing a width of the contact by the object on said panel in accordance with a waveform detected by said reception circuit means, and
• judging means for distinguishing a type of object in contact based on the width obtained by said computing means.

A display system comprising:

• projecting means for projecting an image;
• a touch panel input device arranged thereon comprising:
• a panel capable of propagating surface acoustic waves and in which surface acoustic wave attenuation is caused by an object in contact with said panel;
• emission circuit means for outputting a surface acoustic wave drive;
• an emission transducer for emitting surface acoustic waves in said panel in accordance with the surface wave drive outputted from said emission circuit means;
• a reception transducer for receiving surface acoustic waves in said panel and for outputting a received acoustic signal;
• and
• reception circuit means for receiving the received acoustic wave signal from said reception transducer to detect a position at which the received acoustic wave is attenuated as indicative of a position that the object contacts said panel;
• controller means for controlling said emission circuit and said reception circuit means, comprising:
• computing means for computing a width of the contact by the object on said panel in accordance with a waveform detected by said reception circuit means, and
• judging means for distinguishing a type of object in contact based on the width obtained by said computing means;
• and
• controller means responsive to said touch panel for displaying the image on said projection means.

An overhead projector system comprising:

• an overhead projector;
• a touch panel input device comprising:
• a panel capable of propagating surface acoustic waves and in which surface acoustic wave attenuation is caused by a object in contact with said panel;
• emission circuit means for outputting a surface acoustic wave drive;
• an emission transducer for emitting surface acoustic waves in said panel in accordance with the surface wave drive outputted from said emission circuit means;
• a reception transducer for receiving surface acoustic waves in said panel and for outputting a received acoustic signal;
• and
• reception circuit means for receiving the received acoustic wave signal from said reception transducer to detect a position at which the received acoustic wave is attenuated as indicative of a position that the object contacts said panel;
• and
• controller means for controlling said emission circuit and said reception circuit means, comprising:
• computing means for computing a width of the contact by the object on said panel in accordance with a waveform detected by said reception circuit means, and
• judging means for distinguishing a type of object in contact based on the width obtained by said computing means;
• controller responsive to said touch panel for displaying an image on said projection system.

A touch panel input device comprising:

• a panel having a surface capable of propagating surface acoustic waves, such that a touch of a region on the surface by a touch input device causes perturbation of at least a partial absorption of energy of a surface wave propagating through the region of the touch;
• surface acoustic wave scanning means for scanning said surface with a timed succession of surface acoustic waves directed along parallel paths across said surface in at least one predetermined first direction;
• receiving means for receiving the surface acoustic waves and for convening the received waves into an electrical signal having an amplitude variation indicative of an energy absorption state at said parallel paths;
• and
• signal processing means for detecting a position of the touch of said surface in a second direction substantially perpendicular to the first direction, in accordance with the electrical signal having the amplitude variation,
• said signal processing means comprises:
• comparison means for deriving, as an attenuation waveform, an amplitude difference between a reference electric signal obtained from said receiving means when the panel is not touched and the electric signal obtained from said receiving means when the panel is touched,
• threshold means for comparing the attenuation waveform with a predetermined threshold level,
• intersection detection means responsive to said threshold means for detecting intersections between said attenuation waveform and said threshold level, and
• calculating means responsive to said intersection detection means for calculating a point of time intermediate between the intersections as being representative of the position of the touch.

A method of generating an input signal for an electronic information processing device by means of a touch panel input device having a panel with a surface capable of propagating surface acoustic waves, such that a touch of the surface by a touch input device causes perturbation of at least a partial absorption of energy of a surface wave propagating through the region of the touch, the method comprising the steps of:

• (a) obtaining the electric signal under the condition of no touch of the panel, and storing the signal as reference signal,
• (b) obtaining the electric signal under the condition of touch of said panel, and
• (c) generating an attenuation waveform representing an amplitude difference between the signal obtained in step (b) and the signal stored in step (a),
• (d) comparing the attenuation waveform with a specified threshold level, and generating a corrected attenuation waveform by linearizing parts of the attenuation waveform that are near the threshold level,
• (e) finding two successive intersections of the corrected attenuation waveform with the threshold level,
• (f) calculating the interval between the start of the signal obtained in step (b) and a point between said two intersections, and
• (g) outputting the input signal a position signal representing the result obtained in step (f).

An electronic messaging board comprising:

• a writing surface;
• and
• a touch panel input device comprising:
• a panel having a surface capable of propagating surface acoustic waves, such that a touch of a region on the surface by a touch input device causes perturbation of at least a partial absorption of energy of a surface wave propagating through the region of the touch;
• surface acoustic wave scanning means for scanning said surface with a timed succession of surface acoustic waves directed along parallel paths across said surface in at least one predetermined first direction;
• receiving means for receiving the surface acoustic waves and for converting the received waves into an electrical signal having an amplitude variation indicative of an energy absorption state at said parallel paths;
• and
• signal processing means for detecting a position of the touch of said surface in a second direction substantially perpendicular to the first direction, in accordance with the electrical signal having the amplitude variation,
• said signal processing means comprises:
• comparison means for deriving, as an attenuation waveform, an amplitude difference between a reference electric signal obtained from said receiving means when the panel is not touched and the electric signal obtained from said receiving means when the panel is touched,
• threshold means for comparing the attenuation waveform with a predetermined threshold level,
• intersection detection means responsive to said threshold means for detecting intersections between said attenuation waveform and said threshold level, and
• calculating means responsive to said intersection detection means for calculating a point of time intermediate between the intersections as being representative of the position of the touch.

A display system comprising:

• projecting means for projecting an image;
• and
• a touch panel input device comprising:
• a panel having a surface capable of propagating surface acoustic waves, such that a touch of a region on the surface by a touch input device causes perturbation of at least a partial absorption of energy of a surface wave propagating through the region of the touch;
• surface acoustic wave scanning means for scanning said surface with a timed succession of surface acoustic waves directed along parallel paths across said surface in at least one predetermined first direction;
• receiving means for receiving the surface acoustic waves and for converting the received waves into an electrical signal having an amplitude variation indicative of an energy absorption state at said parallel paths;
• and
• signal processing means for detecting a position of the touch of said surface in a second direction substantially perpendicular to the first direction, in accordance with the electrical signal having the amplitude variation,
• said signal processing means comprises:
• comparison means for deriving, as an attenuation waveform, an amplitude difference between a reference electric signal obtained from said receiving means when the panel is not touched and the electric signal obtained from said receiving means when the panel is touched,
• threshold means for comparing the attenuation waveform with a predetermined threshold level,
• intersection detection means responsive to said threshold means for detecting intersections between said attenuation waveform and said threshold level, and
• calculating means responsive to said intersection detection means for calculating a point of time intermediate between the intersections as being representative of the position of the touch.

An overhead projector system comprising:

• an overhead projector;
• and
• a touch panel input device comprising:
• a panel having a surface capable of propagating surface acoustic waves, such that a touch of a region on the surface by a touch input device causes perturbation of at least a partial absorption of energy of a surface wave propagating through the region of the touch;
• surface acoustic wave scanning means for scanning said surface with a timed succession of surface acoustic waves directed along parallel paths across said surface in at least one predetermined first direction;
• receiving means for receiving the surface acoustic waves and for converting the received waves into an electrical signal having an amplitude variation indicative of an energy absorption state at said parallel paths;
• and
• signal processing means for detecting a position of the touch of said surface in a second direction substantially perpendicular to the first direction, in accordance with the electrical signal having the amplitude variation,
• said signal processing means comprises:
• comparison means for deriving, as an attenuation waveform, an amplitude difference between a reference electric signal obtained from said receiving means when the panel is not touched and the electric signal obtained from said receiving means when the panel is touched,
• threshold means for comparing the attenuation waveform with a predetermined threshold level,
• intersection detection means responsive to said threshold means for detecting intersections between said attenuation waveform and said threshold level, and
• calculating means responsive to said intersection detection means for calculating a point of time intermediate between the intersections as being representative of the position of the touch.