JP2005174189A - Receiver, position detection device for electronic pen, position display system for electronic pen, and ultrasonic wave receiving method for receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver which detects a current position of an electronic pen correctly, a position detection device for an electronic pen, a position display system for an electronic pen, and an ultrasonic wave receiving method for the receiver. <P>SOLUTION: The receiver includes; an infrared ray receiving circuit which receives an infrared signal from the electronic pen; an ultrasonic wave receiving circuit having an ultrasonic sensor which receives an ultrasonic signal from the electronic pen; and a detection circuit which detects a generation position of the infrared signal and the ultrasonic signal using difference in arrival time of the infrared signal and the ultrasonic signal. The ultrasonic wave receiving circuit has a filter property for amplifying the same frequency band as the ultrasonic signal of an output signal of the ultrasonic sensor and an amplification factor which makes a superimposed noise of the output signal equal or below a predetermined level, and equipped with a first amplifier to amplify the output signal and a second amplifier to amplify further the amplified signal by the first amplifier. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a receiver, a position detection device for an electronic pen, a position display system for an electronic pen, and an ultrasonic reception method for the receiver.

  An electronic pen position detection device receives an electronic pen that periodically generates a signal that informs the current position when drawing a pictograph or the like on a medium, and a signal that informs the current position generated by the electronic pen and obtains the current position. And a receiver that is displayed on a display afterwards. For example, a device that obtains the current position of an electronic pen using a propagation time difference between an infrared signal and an ultrasonic signal has been proposed.

In the case of an electronic pen position detection device that uses an infrared signal and an ultrasonic signal, the electronic pen includes an infrared generation circuit that generates an infrared signal and an ultrasonic generation circuit that generates an ultrasonic signal. On the other hand, the receiver determines the current position of the electronic pen using an infrared receiving circuit that receives an infrared signal, two ultrasonic receiving circuits that receive an ultrasonic signal, and the arrival time difference between the infrared signal and the ultrasonic signal. And an arithmetic circuit to be obtained. When the electronic pen generates an infrared signal and an ultrasonic signal when drawing a pictograph or the like on the medium, the arithmetic circuit is configured so that one ultrasonic receiving circuit is based on the time when the infrared receiving circuit receives the infrared signal. The time until the ultrasonic signal is received and the time until the other ultrasonic receiving circuit receives the ultrasonic signal are obtained, and the distance between the electronic pen and the two ultrasonic receiving circuits is calculated based on each time. Further, the intersection position of each distance is obtained as the current position of the electronic pen by the principle of trigonometry. As a result, the receiver displays pictograms and the like on the display based on the signal indicating the current position of the electronic pen.
JP 2003-36225 A

  In the ultrasonic receiving circuit, since the output signal of the ultrasonic sensor is a weak signal with a small amplitude, it is necessary to perform signal processing after amplifying the output signal of the ultrasonic sensor with an appropriate amplification factor. However, when a weak signal with a small amplitude is amplified, the superimposed noise of the weak signal is significantly amplified. That is, on the receiver side, there is a problem that the arithmetic circuit malfunctions and the current position of the electronic pen cannot be detected accurately.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a receiver that accurately detects the current position of an electronic pen, an electronic pen position detection device, an electronic pen position display system, and an ultrasonic reception method for the receiver.

  A main invention for solving the above problems is an infrared receiving circuit that receives an infrared signal from an electronic pen, an ultrasonic receiving circuit that has an ultrasonic sensor that receives an ultrasonic signal from the electronic pen, and the infrared signal. And a detection circuit that detects a generation position of the infrared signal and the ultrasonic signal using a difference in arrival time of the ultrasonic signal, wherein the ultrasonic reception circuit outputs an output of the ultrasonic sensor. A first amplifier for amplifying the output signal, having a filter characteristic for amplifying the same frequency band as the ultrasonic signal of the signal, and an amplification factor that makes a superposition noise of the output signal equal to or lower than a predetermined level; And a second amplifier for further amplifying the amplified signal of the first amplifier.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the receiver which detects the present position of an electronic pen correctly, the position detection apparatus of an electronic pen, the position display system of an electronic pen, and the ultrasonic reception method of a receiver.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Schematic Configuration of Electronic Pen Position Display System ===
An outline of a position display system for an electronic pen according to the present invention will be described with reference to FIG. FIG. 4 is a diagram showing a schematic configuration of an electronic pen position display system according to the present invention.

  The electronic pen 100 periodically generates infrared signals and ultrasonic signals while the pen tip is in contact with the recording medium 200 when drawing a pictogram or the like. The receiver 300 obtains the current position of the electronic pen 100 using the arrival time difference between each infrared signal and ultrasonic signal generated by the electronic pen 100. The display 400 is provided in an electronic device such as a personal computer or a mobile phone, and these electronic devices are connected to the receiver 300 via an appropriate communication interface (not shown). Then, when the receiver 300 transmits a signal indicating the current position of the electronic pen 100 to the electronic device, the display 400 displays a pictograph or the like as a movement locus of the electronic pen 100.

  The recording medium 200 is not unique to this system, and various sizes of media distributed in the market such as electronic blackboards and JIS standard (for example, A4 size, B5 size) recording paper can be used. That is, this system has versatility in selecting the recording medium 200.

=== Schematic Configuration of Electronic Pen Position Detection Device ===
With reference to FIG. 5, an outline of a position detection device for an electronic pen according to the present invention will be described. FIG. 5 is a block diagram showing a schematic configuration of an electronic pen position detecting device according to the present invention.

<< Schematic configuration of electronic pen >>
The electronic pen 100 includes a switch 110, a control circuit 120, an infrared generation circuit 130, an ultrasonic generation circuit 140, and a power supply 150 in a pen-shaped cylindrical container.

  The switch 110 is turned on in accordance with the pressure displacement when the pen tip of the electronic pen 100 comes into contact with the recording medium 200 when drawing a pictograph or the like on the recording medium 200. At this time, the control circuit 120 is applied with the power supply voltage from the power supply 150 to the infrared generation circuit 130 and the ultrasonic generation circuit 140. In particular, the infrared generation circuit 130 and the ultrasonic generation circuit 140 are controlled by the control circuit 120. Works below. On the other hand, the switch 110 is turned off according to the pressure displacement when the pen tip of the electronic pen 100 is separated from the recording medium 200. At this time, the control circuit 120 stops the operation of the infrared generation circuit 130 and the ultrasonic generation circuit 140 when the supply of the power supply voltage from the power supply 150 is cut off. As the power source 150, a battery is adopted in consideration of the portability of the electronic pen 100.

  The control circuit 120 is a circuit that controls the operation of the infrared generation circuit 130, the ultrasonic generation circuit 140, and the power supply 150 while the switch 110 is on. For example, a microcomputer can be employed.

  The infrared generation circuit 130 periodically generates an infrared signal (about 30 THz to 300 THz) having the speed of light while the switch 110 is on.

  The ultrasonic generation circuit 140 periodically generates an ultrasonic signal (about 20 KHz to 100 MHz) having a sound speed slower than the speed of light as a pair with an infrared signal while the switch 110 is on. .

<< Schematic configuration of receiver >>
The receiver 300 includes an infrared receiving circuit 310, for example, two ultrasonic receiving circuits 320A and 320B, a control circuit 330, and a communication interface circuit 340 in a box container.

  The infrared receiving circuit 310 is an infrared sensor made of, for example, an IrDA (Infrared Data Association) standard module, and receives an infrared signal generated from the infrared generation circuit 130 of the electronic pen 100.

  The ultrasonic receiving circuits 320 </ b> A and 320 </ b> B are ultrasonic sensors using, for example, PVDF (Polyvinyl Den Fluoride), and receive ultrasonic signals generated from the ultrasonic generation circuit 140 of the electronic pen 100. The infrared receiving circuit 310 and the ultrasonic receiving circuits 320 </ b> A and 320 </ b> B are disposed on a printed wiring board 350 (FIG. 4) inside the receiver 300. In particular, since the receiver 300 detects the current position of the electronic pen 100 by a triangulation method based on the principle of trigonometry, the infrared receiving circuit 310 is disposed at the front center portion on the printed wiring board 350 to receive ultrasonic waves. The circuits 320 </ b> A and 320 </ b> B are disposed on both sides on the front side of the printed wiring board 350.

  The control circuit 330 (detection circuit) obtains each time from when the infrared receiving circuit 310 receives the infrared signal to when the ultrasonic receiving circuits 320A and 320B receive the ultrasonic signal, and based on each time, the electronic pen For example, a microcomputer can be employed.

  The communication interface circuit 340 transmits a signal indicating the current position of the electronic pen 100 output from the control circuit 330 to an electronic device such as a personal computer or a mobile phone. As a result, a pictograph or the like as a movement locus of the electronic pen 100 is displayed on the display 400. As the communication interface circuit 340, for example, a serial communication method such as a USB (Universal Serial Bus) standard or an IEEE 1394 standard, an infrared communication, or a wireless communication method such as Bluetooth (registered trademark) can be adopted.

=== Method for detecting position of electronic pen ===
The detection method of the electronic pen position detection device according to the present invention will be described with reference to FIGS. FIG. 6 is a diagram illustrating the relationship between the timing at which the electronic pen generates an infrared signal and an ultrasonic signal and the timing at which the receiver receives the infrared signal and the ultrasonic signal from the electronic pen. FIG. 7 is a diagram for explaining a detection method (triangulation method) of the electronic pen position detection device according to the present invention.

  First, when the pen tip of the electronic pen 100 contacts the recording medium 200, the switch 110 is turned on, and the infrared generation circuit 130 and the ultrasonic generation circuit 140 start operating under the control of the control circuit 120. That is, the infrared generation circuit 130 periodically generates an infrared signal having an IR (Infrared Ray) pattern (time t0). The ultrasonic generation circuit 140 starts to operate simultaneously with the infrared generation circuit 130. However, since the ultrasonic signal must be boosted to a predetermined amplitude, the PVDF paired with the infrared signal is generated after the generation of the infrared signal. A pattern ultrasonic signal is periodically generated (time T1).

  On the other hand, in the receiver 300, since the propagation speed of the infrared signal is faster than the propagation speed of the ultrasonic signal, after the infrared receiving circuit 310 receives the infrared signal from the electronic pen 100 (time T3), the ultrasonic receiving circuits 320A and 320B. Receives the ultrasonic signal from the electronic pen 100 (time T5, T6). Note that the times T5 and T6 at which the ultrasonic receiving circuits 320A and 320B receive the ultrasonic signal vary depending on the position of the electronic pen 100 on the recording medium 200. Here, the control circuit 330 obtains a time TL from the time T4 to the time T5 when the infrared receiving circuit 310 finishes receiving the infrared signal from the electronic pen 100, and a time TR from the time T4 to the time T6. The control circuit 330 multiplies each time TL, TR by the propagation speed of the ultrasonic signal to obtain the distances L1, L2 between the current position of the electronic pen 100 and the ultrasonic reception circuits 320A, 320B. . Further, the control circuit 330 obtains the orientation of the electronic pen 100 using the space between the ultrasonic receiving circuits 320A and 320B as a reference line. Then, the control circuit 330 detects the current position of the electronic pen 100 on the principle of trigonometry using the distances L1 and L2.

=== Specific Configuration of Electronic Pen Position Detection Device ===
<< Specific configuration of electronic pen >>
A specific configuration of the electronic pen according to the present invention will be described with reference to FIGS. 1, 2, and 6. FIG. 1 is a circuit diagram showing a specific configuration of an electronic pen according to the present invention. FIG. 2 is a flowchart showing the power supply operation of the electronic pen according to the present invention.

  The two infrared light emitting elements 502 and 504 (LEDs) emit infrared signals that serve as a reference when the receiver 300 detects the current position of the electronic pen 100, and are connected in series. The piezoelectric element 506 constitutes an ultrasonic oscillator for generating an ultrasonic signal having a high voltage sine waveform. For example, the infrared light emitting elements 502 and 504 and the piezoelectric element 506 are formed on a single semiconductor chip.

Based on the voltage VCCBT of the battery 508, the power supply 150 is configured to supply a power supply voltage VCCA for the control circuit 120 (hereinafter referred to as a microcomputer), a power supply voltage VCCB for the infrared generation circuit 130, and a power supply voltage VCCCC for the ultrasonic generation circuit 140. A regulator 510 that is generated, a switch 110 that is turned on in response to a change in the position of the pen tip in the axial direction, and diodes 514A and 514B while the pen tip of the electronic pen 100 is in contact with the recording medium 200; And a voltage detection resistor 516. In particular, the regulator 510 has a VIN terminal, an ON / OFF terminal, a VOUT terminal, and a VSS terminal. The regulator 510 operates when the voltage of the ON / OFF terminal is high, and the voltage of the ON / OFF terminal is low. If it stops working. The VIN terminal of regulator 510 is connected to the positive electrode of battery 508 and one end of switch 110. The ON / OFF terminal of the regulator 510 is connected to the other end of the switch 110 via the diode 514A, and is connected to the P0 terminal of the microcomputer 120 via the diode 514B. Further, the ON / OFF terminal and the VSS terminal of the regulator 510 are connected to the ground GND-A, and the negative electrode of the battery 508 is connected to the ground GND-C.
That is, when the tip of the pen of the electronic pen 100 abuts on the recording medium 200 and the switch 110 is turned on, the voltage of the ON / OFF terminal of the regulator 510 becomes high with the conduction of the diode 514A. Based on voltage VCCBT, power supply voltages VCCA, VCCB, and VCCC are generated. The electronic pen 100 is a circuit in which a digital circuit (microcomputer 120) and an analog circuit (infrared generation circuit 130, ultrasonic generation circuit 140) are mixed. When the power supply voltage generated from the regulator 510 is used for the digital circuit and the analog circuit, the accuracy of the power supply voltage of the analog circuit needs to be higher than the accuracy of the power supply voltage of the digital circuit. Therefore, the power supply 150 branches the power supply voltage generated from the VOUT terminal of the regulator 510 into three power supply voltages VCCA, VCCB, and VCCC and outputs them.

  The microcomputer 120 is connected between the power supply voltage VCCA and the ground GND-A. The microcomputer 120 includes an internal oscillation circuit 518 that generates an oscillation clock having a first oscillation frequency, an external oscillation circuit 520 that generates an oscillation clock having a second oscillation frequency (<first oscillation frequency), and an OFF duration of the switch 110. And a timer 522 for measuring the time. The external oscillation circuit 520 is an oscillation circuit used when controlling the operations of the infrared generation circuit 130 and the ultrasonic generation circuit 140. The second oscillation frequency of the external oscillation circuit 520 is the infrared generation circuit 130 and the ultrasonic generation circuit. It can be changed according to the processing speed when controlling 140. That is, since the first oscillation frequency of the internal oscillation circuit 518 is not specified, a general-purpose microcomputer is sufficient for the microcomputer 120.

  Here, the control operation of the microcomputer 120 with respect to the power supply 150 will be described with reference to FIG.

  First, the microcomputer 120 starts operation when the power supply voltage VCCA from the regulator 510 is applied (S600). The microcomputer 120 executes an initialization operation according to the result of decoding the program data read from the program memory (not shown) (S610). As a result of executing the initialization operation, the microcomputer 120 sets the P0 terminal to the high level (logic value “1”). That is, the diodes 514A and 514B are both conductive. For example, when the tip of the pen of the electronic pen 100 is separated from the recording medium 200, the diode 514A becomes non-conductive when the switch 110 is turned off, but the other diode 514B is continuously conductive. 510 continuously generates power supply voltages VCCA, VCCB, and VCCC. As a result, the microcomputer 120 does not repeatedly start and stop frequently, so that the infrared generation circuit 130 and the ultrasonic generation circuit 140 can be stably controlled. On the other hand, the microcomputer 120 selects an oscillation clock generated by the external oscillation circuit 520 as a result of executing the initialization operation. As a result, the power consumption of the entire electronic pen 100 can be reduced (S620). The microcomputer 120 performs an initial reset of the timer 522 while operating based on the oscillation clock of the external oscillation circuit 520 (S630). The P1 terminal of the microcomputer 120 is connected to one end of the voltage detection resistor 516 on the non-ground side.

  That is, the P1 terminal of the microcomputer 120 is at a high level due to the voltage drop of the voltage detection resistor 516 while the switch 110 is on. Using this, the microcomputer 120 determines whether or not the P1 terminal is at a high level, that is, whether or not the pen tip of the electronic pen 100 is in contact with the recording medium 200 (S640). . When the P1 terminal is at the high level (S640: YES), the microcomputer 120 determines that the pen tip of the electronic pen 100 is in contact with the recording medium 200 and a pictograph or the like is drawn, and the timer 522 The reset process is continued and the determination process of step S640 is executed again (S650). On the other hand, when the P1 terminal is at the low level (S640: NO), the microcomputer 120 determines that the pen tip of the electronic pen 100 is separated from the recording medium 200 and no pictograph or the like is drawn, and the timer The reset of 522 is released. That is, the timer 522 starts measuring time TX (S660). Thereafter, the microcomputer 120 determines whether or not the timer 522 has timed the time TX (S670). If the timer 522 has not yet timed the time TX (S670: NO), the microcomputer 120 determines that the pen tip of the electronic pen 100 is highly likely to come into contact with the recording medium 200 again, and The determination process of step S640 is executed again. On the other hand, when the timer 522 counts the time TX (S670: YES), the microcomputer 120 determines that the pen tip portion of the electronic pen 100 is unlikely to come into contact with the recording medium 200 again. The P0 terminal is set to the low level (logical value “0”) by the insertion process. That is, the diodes 514A and 514B are turned off, and the regulator 510 stops operating. That is, since the regulator 510 stops generating the power supply voltages VCCA, VCCB, and VCCC, the microcomputer 120 stops its operation. As a result, the microcomputer 120 can stop the operation of the power supply 150 after the power supply 150 starts operating, depending on the determination result of the microcomputer 120 itself (S680).

  The infrared generation circuit 130 includes infrared light emitting elements 502 and 504 and an N-channel type MOSFET 524. The gate of MOSFET 524 is connected to the P4 terminal of microcomputer 120 through resistor 526 and to ground GND-B through resistor 528. The drain of the MOSFET 524 is connected to the power supply voltage VCCB (first power supply) via the infrared light emitting elements 502 and 504. Further, the source of the MOSFET 524 is connected to the ground GND-B (second power supply). The MOSFET 524 is a switch element for causing the infrared light emitting elements 502 and 504 to emit light. That is, the MOSFET 524 is turned on when the P4 terminal of the microcomputer 120 is at a high level during the period of time T0 to T1, and the infrared light emitting elements 502 and 504 emit infrared signals. The infrared light emitting elements 502 and 504 are connected in series with the drain-source path of the MOSFET 524, but the on-resistance between the drain and source of the MOSFET 524 is a small value (for example, several tens of mΩ). That is, since the voltage drop other than the infrared light emitting elements 502 and 504 in the infrared generation circuit 130 is almost zero, the infrared light emitting elements 502 and 504 have a sufficient current even when the power supply voltage VCCB is a low value (for example, 3 V). Is supplied and has sufficient luminous power. Thereby, it is possible to effectively reduce the power consumption of the battery 508 and provide the electronic pen 100 suitable for portability. Note that the MOSFET 524 is not limited to the N-channel type, but can adopt a P-channel type. In this case, the connection relationship between the infrared light emitting elements 502 and 504 and the MOSFET 524 and the control logic of the P4 terminal of the microcomputer 120 need to be changed as appropriate.

The ultrasonic wave generation circuit 140 includes a piezoelectric element 506, a coil 530, a half-wave rectifier diode 532, and NPN bipolar transistors 534 and 536. The coil 530 is connected in parallel with the piezoelectric element 506. The base of the bipolar transistor 534 is connected to the P5 terminal of the microcomputer 120 through the resistor 538. Bipolar transistor 534 has a collector connected to power supply voltage VCCC via coil 530 and half-wave rectifying diode 532. Furthermore, the emitter of bipolar transistor 534 is connected to ground GND-D. Similarly, the base of the bipolar transistor 536 is connected to the P6 terminal of the microcomputer 120 via the resistor 540. The collector of the bipolar transistor 536 is connected to the cathode of the half-wave rectifying diode 532 via the resistor 542. Furthermore, the emitter of the bipolar transistor 536 is connected to the ground GND-C. The bipolar transistor 534 is an oscillation switch element that boosts the amplitude of the ultrasonic signal. That is, the bipolar transistor 534 is turned on by raising the P5 terminal of the microcomputer 120 during the period from the time T7 to the time T1, and the amplitude of the ultrasonic signal is boosted.
Note that the period from time T7 to T1 is a period required for boosting the amplitude of the ultrasonic signal to the set value, and time T7 is earlier than time T0 in this embodiment. That is, even when the inductance of the coil 530 is a small value, the ultrasonic wave generation circuit 140 surely boosts the amplitude of the ultrasonic signal to the set value. As a result, it is possible to provide the inexpensive electronic pen 100 using the low-cost coil 530. On the other hand, the bipolar transistor 536 is a switching element for oscillation damping that lowers the amplitude of the ultrasonic signal. That is, during the period from time T8 to T9, the P6 terminal of the microcomputer 120 becomes high level, whereby the bipolar transistor 536 is turned on and the amplitude of the ultrasonic signal is lowered. As a result, the ultrasonic wave generation circuit 140 generates an ultrasonic signal for the period of time T1 to T8.

<< Specific configuration of receiver >>
A specific configuration of the receiver according to the present invention will be described with reference to FIGS. 3 and 6. FIG. 3 is a circuit diagram showing a specific configuration of the receiver according to the present invention.

  The communication interface circuit 340 includes a D + terminal and a D− terminal for inputting / outputting data to / from the control circuit 330 (hereinafter referred to as a microcomputer), a VBUS terminal for outputting a power supply voltage, and a ground GND terminal. . The power supply voltage VBUS output from the VBUS terminal is supplied from an electronic device 400 such as a personal computer.

  The power supply 360 has a regulator 702 and generates a power supply voltage VCCA for the infrared receiving circuit 310, a power supply voltage VCCB for the ultrasonic receiving circuits 320A and 320B, and a power supply voltage VCCPC for the microcomputer 330 based on the power supply voltage VBUS. To do. In particular, the power supply 360 generates the power supply voltage VBUS as the power supply voltage VCCPC for the microcomputer 330. As a result, the microcomputer 330 operates by applying the power supply voltage VCCPC, and generates and outputs the power supply voltage VCCA for the infrared receiving circuit 310. The power supply 360 generates the power supply voltage VCCA applied from the microcomputer 330 as it is. The regulator 702 generates and generates a power supply voltage VCCB for the ultrasonic receiving circuits 320A and 320B based on the power supply voltage VBUS.

  The infrared receiving circuit 310 includes an IrDA standard infrared sensor 704. Infrared sensor 704 is connected between power supply voltage VCCA and ground GND-C. When the infrared sensor 704 receives an infrared signal generated from the infrared generation circuit 130, the infrared sensor 704 outputs a signal indicating that the infrared signal has been received to the microcomputer 330.

  The ultrasonic receiving circuit 320A includes a PVDF ultrasonic sensor 706A, an operational amplifier 708A, and a comparator 710A. The ultrasonic sensor 706A, the operational amplifier 708A, and the comparator 710A are connected between the power supply voltage VCCB and the ground GND-A. The ultrasonic sensor 706A receives the ultrasonic signal generated from the ultrasonic generation circuit 140, and outputs a weak sine wave signal indicating that the ultrasonic signal has been received. The amplitude of the weak signal from the ultrasonic sensor 706A is, for example, several hundred μV. Therefore, the operational amplifier 708A amplifies the amplitude of the weak signal until the comparator 710A can reliably compare the amplitude of the weak signal with the reference voltage VREF. However, when a weak signal having a small amplitude is amplified, the superimposed noise of the weak signal is significantly amplified, causing the comparator 710A to malfunction. Therefore, the operational amplifier 708A includes a first-stage operational amplifier 712A (first amplifier) and a second-stage operational amplifier 714A (second amplifier). The first-stage operational amplifier 712A has a filter characteristic that amplifies the frequency band (eg, several tens of KHz) of the ultrasonic signal and a low amplification factor (eg, 21 dB) that prevents the comparator 710A from malfunctioning. Thereby, the operational amplifier 712A in the first stage amplifies only the same frequency band as the ultrasonic signal in the weak signal with a low amplification factor. The second-stage operational amplifier 714A has a high amplification factor (for example, 17 dB) that enables the comparison operation of the comparator 710A. As a result, the second-stage operational amplifier 714A further amplifies the amplified signal of the first-stage operational amplifier 712A with a high amplification factor. Then, the comparator 710A reliably compares the amplified signal of the second stage operational amplifier 714A with the reference voltage VREF, and outputs a signal indicating the comparison result to the microcomputer 330.

  The configuration of the ultrasonic receiving circuit 320B is the same as that of the ultrasonic receiving circuit 320A. That is, the ultrasonic receiving circuit 320B includes a PVDF ultrasonic sensor 706B, an operational amplifier 708B, and a comparator 710B. The ultrasonic sensor 706B, the operational amplifier 708B, and the comparator 710B are connected between the power supply voltage VCCB and the ground GND-B. The ultrasonic sensor 706B receives the ultrasonic signal generated from the ultrasonic generation circuit 140, and outputs a weak sine wave signal indicating that the ultrasonic signal has been received. The amplitude of the weak signal from the ultrasonic sensor 706B is, for example, several hundred μV. Therefore, the operational amplifier 708B amplifies the amplitude of the weak signal until the comparator 710B can reliably compare the amplitude of the weak signal with the reference voltage VREF. However, when a weak signal having a small amplitude is amplified, the superimposed noise of the weak signal is significantly amplified, causing the comparator 710B to malfunction. Therefore, the operational amplifier 708B includes a first-stage operational amplifier 712B (first amplifier) and a second-stage operational amplifier 714B (second amplifier). The first-stage operational amplifier 712B has a filter characteristic that amplifies the frequency band (for example, several tens of KHz) of the ultrasonic signal and a low amplification factor (for example, 21 dB) that prevents the comparator 710B from malfunctioning. Thereby, the operational amplifier 712B in the first stage amplifies only the same frequency band as the ultrasonic signal in the weak signal with a low amplification factor. The second-stage operational amplifier 714B has a high amplification factor (for example, 17 dB) that enables the comparator 710B to perform a comparison operation. As a result, the second stage operational amplifier 714B further amplifies the amplified signal of the first stage operational amplifier 712B at a high gain. The comparator 710B reliably compares the amplified signal of the second operational amplifier 714B with the reference voltage VREF, and outputs a signal indicating the comparison result to the microcomputer 330.

  As a result, the microcomputer 330 detects the current position of the electronic pen 100 on the principle of trigonometry using signals from the infrared receiving circuit 310 and the ultrasonic receiving circuits 320A and 320B.

  The electronic pen, the electronic pen position detection device, and the electronic pen position display system according to the present invention have been described above. However, the above description is intended to facilitate understanding of the present invention, and the present invention is limited. Not what you want. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents.

It is a circuit diagram which shows the specific structure of the electronic pen concerning this invention. It is a flowchart which shows the power supply operation | movement of the electronic pen concerning this invention. It is a circuit diagram which shows the specific structure of the receiver concerning this invention. It is a figure which shows schematic structure of the position display system of the electronic pen concerning this invention. It is a block diagram which shows schematic structure of the position detection apparatus of the electronic pen concerning this invention. It is a figure which shows the relationship between the timing which an electronic pen produces | generates an infrared signal and an ultrasonic signal, and the timing which a receiver receives the infrared signal and ultrasonic signal from an electronic pen. It is a figure explaining the detection method (triangulation method) of the position detection apparatus of the electronic pen concerning this invention.

Explanation of symbols

100 Electronic pen 110 Switch 120 Control circuit (microcomputer)
DESCRIPTION OF SYMBOLS 130 Infrared generator circuit 140 Ultrasonic generator circuit 150 Power supply 200 Recorded object 300 Receiver 310 Infrared receiver circuit 320A, 320B Ultrasonic receiver circuit 330 Control circuit (microcomputer)
340 Communication interface circuit 350 Printed wiring board 400 Electronic device 502, 504 Infrared light emitting element 506 Piezoelectric element 508 Battery 510 Regulator 514A, 514B Diode 518 Internal oscillation circuit 520 External oscillation circuit 522 Timer 524 MOSFET
530 Coil 532 Half-wave clear diode 534, 536 Bipolar transistor

Claims (5)

Using an infrared receiving circuit for receiving an infrared signal from an electronic pen, an ultrasonic receiving circuit having an ultrasonic sensor for receiving an ultrasonic signal from the electronic pen, and an arrival time difference between the infrared signal and the ultrasonic signal A detection circuit for detecting a generation position of the infrared signal and the ultrasonic signal, and a receiver,
The ultrasonic receiving circuit is
The output signal of the ultrasonic sensor has a filter characteristic for amplifying the same frequency band as that of the ultrasonic signal, and an amplification factor that makes superimposed noise of the output signal equal to or lower than a predetermined level, and amplifies the output signal A first amplifier;
A second amplifier for further amplifying the amplified signal of the first amplifier;
A receiver comprising: An electronic pen for generating an infrared signal and an ultrasonic signal, an infrared receiving circuit for receiving an infrared signal from the electronic pen, an ultrasonic receiving circuit having an ultrasonic sensor for receiving an ultrasonic signal from the electronic pen, and the infrared ray A receiver having a detection circuit that detects a generation position of the infrared signal and the ultrasonic signal using a difference in arrival time between the signal and the ultrasonic signal, and a position detection device for an electronic pen comprising:
The receiver is the ultrasonic receiving circuit,
The output signal of the ultrasonic sensor has a filter characteristic for amplifying the same frequency band as that of the ultrasonic signal, and an amplification factor that makes superimposed noise of the output signal equal to or lower than a predetermined level, and amplifies the output signal A first amplifier;
A second amplifier for further amplifying the amplified signal of the first amplifier;
A position detection device for an electronic pen, comprising: The receiver is
The position detection device for an electronic pen according to claim 2, wherein a display signal for displaying the position of the electronic pen is output to a display based on a detection result of the detection circuit. An electronic pen for generating an infrared signal and an ultrasonic signal, an infrared receiving circuit for receiving an infrared signal from the electronic pen, an ultrasonic receiving circuit having an ultrasonic sensor for receiving an ultrasonic signal from the electronic pen, and the infrared ray A receiver having a detection circuit for detecting a generation position of the infrared signal and the ultrasonic signal using a difference in arrival time between the signal and the ultrasonic signal, and a position of the electronic pen based on a detection result of the detection circuit An electronic pen position display system comprising a display,
The receiver, as the ultrasonic receiving circuit,
The output signal of the ultrasonic sensor has a filter characteristic for amplifying the same frequency band as that of the ultrasonic signal, and an amplification factor that makes superimposed noise of the output signal equal to or lower than a predetermined level, and amplifies the output signal A first amplifier;
A second amplifier for further amplifying the amplified signal of the first amplifier;
A position display system for an electronic pen, comprising: Using an infrared receiving circuit for receiving an infrared signal from an electronic pen, an ultrasonic receiving circuit having an ultrasonic sensor for receiving an ultrasonic signal from the electronic pen, and an arrival time difference between the infrared signal and the ultrasonic signal In a receiver comprising a detection circuit for detecting the generation position of the infrared signal and the ultrasonic signal,
The ultrasonic receiving circuit includes a first amplifier and a second amplifier,
The first amplifier has a filter characteristic for amplifying the same frequency band as the ultrasonic signal of the output signal of the ultrasonic sensor, and an amplification factor that makes the superimposed noise of the output signal equal to or lower than a predetermined level. Amplifying the output signal;
The second amplifier further amplifies the amplified signal of the first amplifier;
An ultrasonic reception method for a receiver.

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