Method executed by sensor controller and sensor controller

Abstract

To perform drawing by an electromagnetic induction pen with high precision, without grounding a resonance circuit within the electromagnetic induction pen at an interval of sending power feeding alternating magnetic fields.SOLUTION: A method is executed by a sensor controller which detects an electromagnetic induction pen by using an EMR sensor, the method being such that, after a predetermined time has elapsed from stopping sending of power feeding alternating magnetic fields SM for supplying electric power to the electromagnetic induction pen from the EMR sensor, canceling alternating magnetic fields CM which are alternating magnetic fields which vibrate in a phase which cancels remaining resonance of the electromagnetic induction pen are sent from the EMR sensor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method performed by a sensor controller and to a sensor controller. [Background technology]

[0002] Electromagnetic induction type (EMR type) input devices are known as input devices for electronic devices such as tablet terminals and smartphones. This type of input device includes, for example, a pen-shaped electromagnetic induction pen and a position detection device having a flat input surface. A user performs input operations by sliding the electromagnetic induction pen over the input surface as if writing letters or pictures on a piece of paper. Patent Document 1 discloses an example of an EMR type input device.

[0003] The position detection device detects the position of an electromagnetic induction pen on an input surface. It is composed of an EMR sensor consisting of multiple loop coils arranged on the input surface and a sensor controller connected to each coil. The electromagnetic induction pen also has a resonant circuit consisting of a coil and a capacitor connected in series. When the sensor controller supplies AC current to one of the multiple loop coils, an AC magnetic field is generated from that loop coil. This AC magnetic field is sent from the position detection device to power the electromagnetic induction pen and is hereinafter referred to as the "power supply AC magnetic field." When the coil in the electromagnetic induction pen enters the power supply AC magnetic field, an electromotive force is generated across both ends, charging the capacitor. When the sensor controller then stops supplying AC current, AC current flows in the resonant circuit due to the power stored in the capacitor, which generates an AC magnetic field from the coil that makes up the resonant circuit. This AC magnetic field sent from the electromagnetic induction pen is hereinafter referred to as the "pen AC magnetic field." The sensor controller obtains the intensity distribution of the alternating current generated in each loop coil by the pen alternating magnetic field, and based on the result, derives the position of the electromagnetic induction pen within the input surface.

[0004] Depending on the type of electromagnetic induction pen, the position detection device may also detect the pen pressure, which is the pressure applied to the tip of the electromagnetic induction pen. A variable capacitor, whose capacitance changes depending on the pen pressure, is connected in parallel to the capacitor that constitutes the resonant circuit of the electromagnetic induction pen that detects the pen pressure. When the pen pressure changes, the capacitance of the variable capacitor changes, which in turn changes the resonant frequency of the resonant circuit and, as a result, the frequency of the pen's alternating magnetic field. Therefore, the sensor controller detects the pen pressure by detecting the frequency of the alternating current generated in each loop coil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6698386 Summary of the Invention [Problem to be solved by the invention]

[0006] The resonance of the resonant circuit in the electromagnetic induction pen converges over time after the sensor controller stops transmitting the power supply alternating magnetic field. If the sensor controller starts transmitting the next power supply alternating magnetic field before the resonance has sufficiently converged, residual resonance will affect the pen alternating magnetic field emitted from the electromagnetic induction pen after the previous transmission has stopped, resulting in a pen alternating magnetic field with an amplitude and frequency different from the original values. If the amplitude of the pen alternating magnetic field differs from the original values, the accuracy of detecting the position and height of the electromagnetic induction pen will decrease, and if the amplitude of the pen alternating magnetic field differs from the original values, the accuracy of detecting the writing pressure value will decrease. Since these decreases can also cause a decrease in drawing accuracy, the sensor controller has traditionally waited until the resonance of the resonant circuit in the electromagnetic induction pen has sufficiently converged before transmitting the next power supply alternating magnetic field. However, longer intervals between power supply alternating magnetic field transmissions mean a decrease in the frequency of detecting the position and writing pressure value, which also causes a decrease in drawing accuracy.

[0007] One method to solve the above problems is to temporarily ground the resonant circuit in the electromagnetic induction pen during the intervals between the transmission of the alternating magnetic field by the sensor controller. However, this method creates another problem: an integrated circuit must be installed in the electromagnetic induction pen to control the grounding timing of the resonant circuit.

[0008] Therefore, one object of the present invention is to provide a method and a sensor controller that enable drawing with an electromagnetic induction pen with high accuracy without grounding the resonant circuit in the electromagnetic induction pen during the intervals between the transmission of the alternating magnetic field for power supply. [Means for solving the problem]

[0009] The method according to the present invention is a method executed by a sensor controller that detects an electromagnetic induction pen using an EMR sensor, and after a predetermined time has elapsed since the EMR sensor stopped transmitting the power supply alternating magnetic field for supplying power to the electromagnetic induction pen, the EMR sensor transmits a canceling alternating magnetic field, which is an alternating magnetic field that oscillates at a phase that cancels out the residual resonance of the electromagnetic induction pen.

[0010] The sensor controller according to the present invention is a sensor controller that detects an electromagnetic induction pen using an EMR sensor, and after a predetermined time has elapsed since the EMR sensor stopped transmitting the power supply alternating magnetic field for supplying power to the electromagnetic induction pen, the EMR sensor transmits a canceling alternating magnetic field, which is an alternating magnetic field that oscillates at a phase that cancels out the residual resonance of the electromagnetic induction pen. [Effects of the Invention]

[0011] According to the present invention, residual resonance can be forcibly converged by the counteracting alternating magnetic field emitted from the EMR sensor, making it possible to draw with the electromagnetic induction pen with high precision without grounding the resonant circuit in the electromagnetic induction pen during the intervals between the emission of the alternating magnetic field by the sensor controller. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing a configuration of a position detection system 1 according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing an example of a waveform of an alternating magnetic field according to the background art of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of a waveform of an alternating magnetic field according to an embodiment of the present invention. [Figure 4] 10 is a diagram showing the relationship between the transmission phase of the counteracting alternating magnetic field CM or the amplifying alternating magnetic field AM and the waveform of the pen alternating magnetic field PM. FIG. [Figure 5] 10 is a diagram showing a processing flow of electromagnetic induction pen detection processing executed by the sensor controller 31. FIG. [Figure 6] 10 is a diagram showing a processing flow of electromagnetic induction pen detection processing executed by the sensor controller 31. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0014] Fig. 1 is a diagram showing the configuration of a position detection system 1 according to an embodiment of the present invention. As shown in the figure, the position detection system 1 comprises an electromagnetic induction pen 2 and a position detection device 3. Of these, the electromagnetic induction pen 2 is a pen that supports position detection using the EMR method, and is configured to have a resonant circuit including a coil and a capacitor inside.

[0015] The position detection device 3 is a computer that supports pen input using the EMR method and touch input using the capacitive method, and is configured with a switch circuit 30, a sensor controller 31, a host processor 32, and a structure 33. The structure 33 is configured to include a touch sensor 40, an EMR sensor 41, and a display 42. In a typical example, the position detection device 3 is a tablet terminal or a laptop computer that supports pen input and touch input.

[0016] First, focusing on the structure 33, the touch sensor 40 is a sensor including a plurality of Tx electrodes, which are linear electrodes each extending in the x direction and juxtaposed in the y direction, and a plurality of Rx electrodes, which are linear electrodes each extending in the y direction and juxtaposed in the x direction. Each of the plurality of Tx electrodes and each of the plurality of Rx electrodes are connected to the sensor controller 31 via a switch circuit 30.

[0017] The EMR sensor 41 is a sensor including a plurality of Tx coils and a plurality of Rx coils. Each of the plurality of Tx coils and each of the plurality of Rx coils are also connected to the sensor controller 31 via the switch circuit 30.

[0018] The display 42 is a display device that displays the video signal supplied from the host processor 32. The type of display system of the display 42 is not particularly limited, but may be a liquid crystal display or an organic EL display.

[0019] The surface of the structure 33 is covered with a cover glass or cover film (not shown), and forms a panel surface 3a that also serves as the touch surface of the touch sensor 40 and the EMR sensor 41 and the display surface of the display 42. A user of the position detection device 3 performs pen input by sliding the pen tip of the electromagnetic induction pen 2 over this panel surface 3a, and performs touch input by sliding their finger over it.

[0020] The switch circuit 30 is an integrated circuit including a group of switches provided between the sensor controller 31 and each electrode in the touch sensor 40 and each coil in the EMR sensor 41. The switching of the group of switches constituting the switch circuit 30 is performed by the sensor controller 31.

[0021] The sensor controller 31 is an integrated circuit having a function of deriving the position of a finger on the panel surface 3a using the touch sensor 40 and a function of deriving the position of the electromagnetic induction pen 2 on the panel surface 3a using the EMR sensor 41. The sensor controller 31 is also configured to have a function of receiving data transmitted by the electromagnetic induction pen 2. The position derived by the sensor controller 31 and the received data are sequentially supplied to the host processor 32.

[0022] To briefly explain the processing performed by the sensor controller 31, first, regarding the position of the finger, the sensor controller 31 transmits a predetermined touch detection signal from each of the multiple Tx electrodes and receives it at each of the multiple Rx electrodes, thereby acquiring the intensity of the touch detection signal received at each intersection of the multiple Rx electrodes and the multiple Tx electrodes. Then, the sensor controller 31 derives the position of the finger on the panel surface 3a based on the distribution of the acquired intensity.

[0023] Next, regarding the position of the electromagnetic induction pen 2, the sensor controller 31 sequentially supplies an AC current to the multiple Tx coils, thereby sequentially transmitting the above-mentioned power supply AC magnetic field from each Tx coil. When a coil constituting the resonant circuit of the electromagnetic induction pen 2 enters this power supply AC magnetic field, an electromotive force is generated across both ends of the coil, and the capacitor constituting the resonant circuit together with the coil is charged. After that, when the sensor controller 31 stops transmitting the power supply AC magnetic field, the above-mentioned pen AC magnetic field is transmitted from the coil of the electromagnetic induction pen 2 due to the power stored in the capacitor. The sensor controller 31 receives the AC current (hereinafter referred to as "pen signal") generated in each Rx coil by this pen AC magnetic field, and by acquiring its intensity, derives the position of the electromagnetic induction pen 2 on the panel surface 3a.

[0024] There are two types of processing by the sensor controller 31 to derive the position of the electromagnetic induction pen 2: global scan and sector scan. Global scan is processing to detect the position of the electromagnetic induction pen 2 over the entire panel surface 3a, and is executed when the electromagnetic induction pen 2 has not yet been detected. In contrast, sector scan is processing to update the position of the electromagnetic induction pen 2 that has already been detected, and the sensor controller 31 detects the position of the electromagnetic induction pen 2 only in the area of ​​the panel surface 3a near the latest position of the electromagnetic induction pen 2.

[0025] When performing a global scan, the sensor controller 31 sequentially supplies AC current to each of the multiple Tx coils that make up the EMR sensor 41, and each time, performs a process of receiving a pen signal from each of the multiple Rx coils that make up the EMR sensor 41. Then, the sensor controller 31 derives the distribution of reception strength within the panel surface 3a from the reception strength of the pen signal for each combination of Tx coil and Rx coil, and derives the position of its peak as the position of the electromagnetic induction pen 2. On the other hand, when performing a sector scan, the sensor controller 31 sequentially supplies AC current to each of a predetermined number of Tx coils that are near the most recent position of the electromagnetic induction pen 2, and each time, performs a process of receiving a pen signal from each of a predetermined number of Rx coils that are near the most recent position of the electromagnetic induction pen 2. Then, the sensor controller 31 derives the distribution of reception strength within the panel surface 3a from the reception strength of the pen signal for each combination of Tx coil and Rx coil, and updates the position of the electromagnetic induction pen 2 based on the position of its peak.

[0026] Finally, with regard to the data transmitted by the electromagnetic induction pen 2, the data to be transmitted may include a writing pressure value indicating the pressure applied to the pen tip, on / off information indicating the state of a switch provided on the surface of the housing of the electromagnetic induction pen 2, a pen ID pre-stored in the memory of the electromagnetic induction pen 2, and the like. The electromagnetic induction pen 2 according to this embodiment is configured so that the resonant frequency of the resonant circuit changes depending on the content of these data, and when the resonant frequency of the resonant circuit changes, the frequency of the pen signal received by the sensor controller 31 also changes. The sensor controller 31 receives the data transmitted by the electromagnetic induction pen 2 by detecting this change in frequency by demodulating the received pen signal. This data reception will be explained in more detail later.

[0027] The host processor 32 is the central processing unit of the position detection device 3, and executes programs read from a memory (not shown) to execute the operating system and various applications of the position detection device 3. The processes executed by the host processor 32 in accordance with the programs include generating a video signal and supplying it to the display 42, and various processes performed using the position and data supplied from the sensor controller 31. The various processes performed using the position and data include, for example, moving a cursor displayed on the display surface and generating stroke data indicating the trajectory of the electromagnetic induction pen 2 on the touch surface. With regard to the stroke data, the host processor 32 also performs processes such as rendering and displaying the generated stroke data, generating and recording digital ink including the generated stroke data, and transmitting the generated digital ink to an external device in response to a user instruction.

[0028] Fig. 2 shows an example of the waveform of an alternating magnetic field according to the background art of the present invention. Fig. 2(a) shows an example when the writing pressure value is 0 g, and Fig. 2(b) shows an example when the writing pressure value is 500 g. In Fig. 2 and the figures shown below, the power supply alternating magnetic field is represented as "SM" and the pen alternating magnetic field is represented as "PM."

[0029] 2, the sensor controller 31 starts transmitting the power supply alternating magnetic field SM at time t1 and stops transmitting the power supply alternating magnetic field SM 30 μs later at time t2. Between time t1 and time t2 while the power supply alternating magnetic field SM is being transmitted, the amplitude of the pen alternating magnetic field PM gradually increases. This is because the power supply alternating magnetic field SM generates an electromotive force in a coil that constitutes a resonant circuit in the electromagnetic induction pen 2, which charges a capacitor that constitutes a resonant circuit in the electromagnetic induction pen 2.

[0030] Even though the transmission of the power supply alternating magnetic field SM stops at time t2, the pen alternating magnetic field PM does not immediately disappear, and the amplitude of the pen alternating magnetic field PM gradually decreases. This is because the capacitor that constitutes the resonant circuit in the electromagnetic induction pen 2 gradually discharges. The sensor controller 31 receives a pen signal between the time when the transmission of the power supply alternating magnetic field SM stops and time t3, 30 μs later, and derives the position of the electromagnetic induction pen 2 and receives data transmitted by the electromagnetic induction pen 2.

[0031] Here, the reception of data transmitted by the electromagnetic induction pen 2 will be described in detail. As described above, the electromagnetic induction pen 2 according to this embodiment is configured so that the resonant frequency of the resonant circuit changes depending on the content of the data to be transmitted. Since a change in the resonant frequency of the resonant circuit means a change in the frequency of the pen alternating magnetic field PM, the sensor controller 31 can demodulate the data transmitted by the electromagnetic induction pen 2 by detecting the frequency of the pen alternating magnetic field PM. However, in an actual sensor controller 31, a technique called "delta phase (ΔPhase)" is used, which is capable of detecting a change in the frequency of the pen alternating magnetic field PM with a simpler configuration.

[0032] According to the delta phase, the sensor controller 31 determines the phase of the pen alternating magnetic field PM based on the amplitude of the pen signal after a predetermined time has elapsed since the transmission of the power supply alternating magnetic field SM stopped (for example, at the aforementioned time t3), and acquires the data transmitted by the electromagnetic induction pen 2 from the determined phase. If the phase of the pen alternating magnetic field PM matches the phase of the power supply alternating magnetic field SM when the sensor controller 31 stops transmitting the power supply alternating magnetic field SM, the phase of the pen alternating magnetic field PM at time t3 is a value uniquely determined by the frequency of the pen alternating magnetic field PM. Therefore, the sensor controller 31 using the delta phase can acquire the data transmitted by the electromagnetic induction pen 2 from the determined phase of the pen alternating magnetic field PM. Specifically, a table correlating phases with data is stored, and the data transmitted by the electromagnetic induction pen 2 can be acquired by referencing this table based on the determined phase of the pen alternating magnetic field PM. However, if the above-mentioned correspondence is not established due to residual resonance of the electromagnetic induction pen 2, acquiring the data in this manner may not necessarily result in correct data. Therefore, the sensor controller 31 according to the background art is configured to wait until the resonance of the resonant circuit in the electromagnetic induction pen 2 has sufficiently converged before transmitting the next alternating magnetic field SM for power supply.

[0033] Referring back to FIG. 2 , the sensor controller 31 of this example waits another 270 μs after time t3, and then starts transmitting the next power supply alternating magnetic field SM at time t4. The 270 μs wait time is the time required for the resonance in the electromagnetic induction pen 2 to converge sufficiently. However, waiting for 270 μs in this manner would lengthen the interval between power supply alternating magnetic fields SM, reducing the frequency of position and pen pressure detection. Therefore, the sensor controller 31 of this embodiment forcibly removes the residual resonance of the electromagnetic induction pen 2 by transmitting a counteracting alternating magnetic field, which is an alternating magnetic field with a phase that cancels out the residual resonance of the electromagnetic induction pen 2, prior to transmitting the power supply alternating magnetic field SM. This point will be described in detail below.

[0034] 3 is a diagram showing an example of the waveform of an alternating magnetic field according to this embodiment. The sensor controller 31 according to this embodiment does not wait for 270 μs as shown in FIG. 2, but instead emits an alternating magnetic field oscillating at a phase that cancels the residual resonance of the electromagnetic induction pen 2 for a predetermined time T1 before emitting the next alternating magnetic field SM for power supply. Hereinafter, this alternating magnetic field emitted for the predetermined time T1 will be referred to as a "countering alternating magnetic field CM." Thereafter, the sensor controller 31 emits the next alternating magnetic field SM for power supply for a predetermined time T2.

[0035] Here, the sensor controller 31 may transmit the next power supply alternating magnetic field SM immediately after transmitting the counteracting alternating magnetic field CM, or may transmit the counteracting alternating magnetic field CM, then stop transmitting the alternating magnetic field, and then transmit the next power supply alternating magnetic field SM. In the former case, the phase of the power supply alternating magnetic field SM may be the same as the phase of the counteracting alternating magnetic field CM. FIG. 3 shows an example of the former case. The specific values ​​of the predetermined times T1 and T2 may be fixed, such as T1 = 7.5 μsec and T2 = 22.5 μsec. Alternatively, T2 = 30 μsec. In this case, power can be supplied to the electromagnetic induction pen 2 for the same time as in the example of FIG. 2.

[0036] 2 (the timing when a predetermined time (specifically, 30 μsec) has elapsed since the transmission of the power supply alternating magnetic field SM was stopped), the sensor controller 31 performs processing to delay the exact timing of the start of transmission by Δμsec (Δ is a value less than one period of the counteracting alternating magnetic field CM and the power supply alternating magnetic field SM) from time t3. By performing this delay processing, the sensor controller 31 controls the phase of the counteracting alternating magnetic field CM.

[0037] Regarding the specific value of Δ, each time the sensor controller 31 receives a pen signal, it acquires the phase (received phase) of the received pen signal based on the phase (transmitted phase) of the power supply alternating magnetic field SM transmitted immediately before. Then, it determines the phase of the counteracting alternating magnetic field CM based on the acquired received phase, and determines the value of Δ so that the counteracting alternating magnetic field CM is transmitted at the determined phase. Specifically, if the determined phase is θ, then the value of Δ can be determined by Δ=(θ / 2π)×T, where T is the period of the counteracting alternating magnetic field CM (= the period of the power supply alternating magnetic field SM). This makes it possible for the counteracting alternating magnetic field CM to cancel out residual resonance within the electromagnetic induction pen 2.

[0038] FIG. 3 shows how the residual resonance in the electromagnetic induction pen 2 is canceled by the counteracting alternating magnetic field CM, which is transmitted Δμ seconds after time t3. As shown in the figure, the transmission of the counteracting alternating magnetic field CM begins at time t5, Δμ seconds after time t3. At the same time, the rate of decrease in the amplitude of the pen alternating magnetic field PM increases. At time t6, when the transmission of the counteracting alternating magnetic field CM ends, the amplitude of the pen alternating magnetic field PM temporarily converges to zero. In the example of FIG. 3, the sensor controller 31 transmits the next power supply alternating magnetic field SM immediately after transmitting the counteracting alternating magnetic field CM. Therefore, after time t6, the amplitude of the pen alternating magnetic field PM increases again. Because the amplitude of the pen alternating magnetic field PM temporarily returns to zero at time t6, the influence of the residual resonance in the electromagnetic induction pen 2 on this increasing pen alternating magnetic field PM is eliminated. Therefore, in the example shown in FIG. 3, a decrease in the accuracy of detecting position and writing pressure values ​​due to the residual resonance of the electromagnetic induction pen 2 is avoided.

[0039] 3 illustrates an example in which the pen alternating magnetic field PM is converged by transmitting a counteracting alternating magnetic field CM. However, instead of transmitting the counteracting alternating magnetic field CM, an alternating magnetic field that increases the amplitude of the pen alternating magnetic field PM may be transmitted. Hereinafter, this alternating magnetic field will be referred to as an "amplified alternating magnetic field AM." Forcibly increasing the amplitude of the pen alternating magnetic field PM by the amplified alternating magnetic field AM is an effective process for reliably supplying power to the electromagnetic induction pen 2 located away from the panel surface 3a, and can be used when the electromagnetic induction pen 2 is hovering (the pen tip is floating in the air) and no drawing is being performed with the electromagnetic induction pen 2.

[0040] 4 shows the relationship between the transmission phase of the counteracting alternating magnetic field CM or the amplified alternating magnetic field AM and the waveform of the pen alternating magnetic field PM. (a) to (c) of FIG. 4 show the case where the writing pressure is 0 g and the transmission phases of the counteracting alternating magnetic field CM or the amplified alternating magnetic field AM are set to 0°, 264°, and 96°, respectively. (d) to (f) of FIG. 4 show the case where the writing pressure is 500 g and the transmission phases of the counteracting alternating magnetic field CM or the amplified alternating magnetic field AM are set to 0°, 48°, and 288°, respectively. As can be seen from these figures, the required value of the transmission phase of the counteracting alternating magnetic field CM or the amplified alternating magnetic field AM varies depending on the writing pressure (data transmitted by the electromagnetic induction pen 2). However, whether the writing pressure is 0 g or 500 g, by appropriately setting the transmission phase, it is possible to achieve both forced convergence of the pen alternating magnetic field PM and forced increase in the amplitude of the pen alternating magnetic field PM.

[0041] 5 and 6 are diagrams showing the processing flow of the electromagnetic induction pen detection processing executed by the sensor controller 31. Below, with reference to these diagrams, we will explain in more detail the processing performed by the sensor controller 31 to forcibly converge the pen alternating magnetic field PM or forcibly increase the amplitude of the pen alternating magnetic field PM. In the following explanation, the power supply alternating magnetic field SM, the counteracting alternating magnetic field CM, and the amplifying alternating magnetic field AM may be collectively referred to as the "sending alternating magnetic field."

[0042] 5, the sensor controller 31 first initializes various transmission parameters of the transmitted alternating magnetic field, including the transmission frequency and transmission phase (step S1). Then, the sensor controller 31 executes the global scan described above (step S2). In the global scan, the alternating magnetic field transmitted by the sensor controller 31 is only the power supply alternating magnetic field SM, and the counteracting alternating magnetic field CM and the amplifying alternating magnetic field AM are not transmitted.

[0043] After the global scan is completed, the sensor controller 31 calculates the maximum reception strength of the pen signal (step S3) and determines whether the calculated maximum reception strength is equal to or greater than a predetermined value a (step S4). The predetermined value a is a threshold value that serves as a criterion for determining whether the sensor controller 31 is able to receive a pen signal from the electromagnetic induction pen 2. If the sensor controller 31 determines in step S4 that the maximum reception strength is less than the predetermined value a, the sensor controller 31 determines that the electromagnetic induction pen 2 has not been detected and returns to step S2.

[0044] On the other hand, if the sensor controller 31 determines in step S4 that the maximum reception strength is equal to or greater than the predetermined value a, it derives the distribution of reception strength within the panel surface 3a from the reception strength of the pen signal for each combination of the Tx coil and the Rx coil, and derives the position of the peak as the position of the electromagnetic induction pen 2 (step S5). The position thus derived is supplied from the sensor controller 31 to the host processor 32.

[0045] Then, the sensor controller 31 transmits the power supply alternating magnetic field SM and receives the pen signal once using the combination (peak coil) of the Tx coil and Rx coil where the maximum reception strength is observed (step S6).Then, the sensor controller 31 calculates the reception strength of the pen signal (step S7) and obtains the reception phase of the pen signal based on the transmission phase of the power supply alternating magnetic field SM (step S8).

[0046] Next, the sensor controller 31 determines whether the reception strength calculated in step S6 is equal to or greater than a predetermined value b, equal to or greater than a predetermined value a but less than b, or less than a predetermined value a (step S9). The predetermined value a is the same as the predetermined value a described in step S4, and the predetermined value b is a threshold value that serves as a criterion for determining whether the electromagnetic induction pen 2 can be considered to be in contact with the panel surface 3a. If the sensor controller 31 determines in step S9 that the reception strength is less than the predetermined value a, it determines that the electromagnetic induction pen 2 is no longer detected, and returns to step S2.

[0047] On the other hand, if the sensor controller 31 determines in step S9 that the reception strength is equal to or greater than the predetermined value a and less than the predetermined value b, it considers that the electromagnetic induction pen 2 is not in contact with the panel surface 3a, and determines a transmission phase that does not kill the resonance in the electromagnetic induction pen 2 based on the reception phase acquired in step S8 (step S10). By transmitting the amplified alternating magnetic field AM at the transmission phase determined in this manner, the amplitude of the pen alternating magnetic field PM can be forcibly increased, as illustrated in Figures 4(a), (c), and (f), so that the sensor controller 31 can suitably receive a pen signal even if the electromagnetic induction pen 2 is not close enough to the panel surface 3a and therefore the amplitude is not stable.

[0048] Furthermore, when the sensor controller 31 determines in step S9 that the reception strength is equal to or greater than the predetermined value b, it considers that the electromagnetic induction pen 2 is in contact with the panel surface 3a, and determines a transmission phase for temporarily converging the resonance in the electromagnetic induction pen 2 based on the reception phase acquired in step S8 (step S11). By transmitting the counteracting alternating magnetic field CM at the transmission phase thus determined, it is possible to forcibly converge the pen alternating magnetic field PM, as exemplified in Figures 4(b), (d), and (e), thereby reducing the possibility that the sensor controller 31 will acquire erroneous data due to residual resonance in the electromagnetic induction pen 2.

[0049] After completing step S10 or step S11, the sensor controller 31 resets the transmission parameters (step S12) according to the transmission phase determined in step S10 or step S11, as shown in FIG. 6, and then performs the above-mentioned sector scan (step S13). In this sector scan, the sensor controller 31 transmits a power supply alternating magnetic field SM from a certain Tx coil for T2 μs, and then, a predetermined time (e.g., 30 μs)+Δ μs after the power supply alternating magnetic field SM has stopped, transmits the next counteracting alternating magnetic field CM or amplifying alternating magnetic field AM for T1 μs, repeating this process. Δ is a value determined according to the transmission phase determined in step S10 or step S11. This makes it possible to converge the pen alternating magnetic field PM or increase the amplitude of the pen alternating magnetic field PM each time the power supply alternating magnetic field SM is transmitted.

[0050] After the sector scan is completed, the sensor controller 31 calculates the maximum reception strength of the pen signal (step S14) and determines whether the calculated maximum reception strength is equal to or greater than a predetermined value a (step S15). The predetermined value a is the same as the predetermined value a described in step S4. If it is determined in step S15 that the maximum reception strength is less than the predetermined value a, the sensor controller 31 determines that the electromagnetic induction pen 2 is no longer detected and returns to step S2.

[0051] On the other hand, if the sensor controller 31 determines in step S15 that the maximum reception strength is equal to or greater than the predetermined value a, it derives the distribution of reception strength on the panel surface 3a from the reception strength of the pen signal for each combination of the Tx coil and the Rx coil, and updates the position of the electromagnetic induction pen 2 based on the position of its peak (step S16). The sensor controller 31 also performs processing to acquire data transmitted by the electromagnetic induction pen, including the writing pressure value, by demodulating the received pen signal (step S17). The updated position and the acquired data are supplied from the sensor controller 31 to the host processor 32.

[0052] Thereafter, the sensor controller 31 acquires the reception phase of the pen signal based on the transmission phase of the power supply alternating magnetic field SM (step S18). The transmission phase and reception phase referred to at this time may be those when the maximum reception strength of the pen signal is observed. Next, the sensor controller 31 determines whether the writing pressure value acquired in step S17 is greater than 0 (i.e., whether the electromagnetic induction pen 2 is in contact with the panel surface 3a) (step S19). If the result of the determination in step S19 is that the writing pressure value is 0, the sensor controller 31 determines a transmission phase that does not kill the resonance in the electromagnetic induction pen 2 based on the reception phase acquired in step S18 (step S20). As a result, as in step S10 of FIG. 5, the amplified alternating magnetic field AM is sent before the power supply alternating magnetic field SM, and the amplitude of the pen alternating magnetic field PM can be forcibly increased, so that the sensor controller 31 can preferably receive the pen signal from the electromagnetic induction pen 2 during hover.

[0053] On the other hand, if it is determined in step S19 that the writing pressure value is greater than 0, the sensor controller 31 determines a transmission phase for temporarily converging the resonance in the electromagnetic induction pen 2 based on the reception phase acquired in step S18 (step S21). As a result, as in step S11 in Fig. 5, the counteracting alternating magnetic field CM is sent out before the power supply alternating magnetic field SM, and the pen alternating magnetic field PM can be forcibly converged, thereby reducing the possibility that the sensor controller 31 will acquire erroneous data due to residual resonance in the electromagnetic induction pen 2.

[0054] After completing step S20 or step S21, the sensor controller 31 returns to step S12 to continue the process. This makes it possible to effectively use the amplifying alternating magnetic field AM and the counteracting alternating magnetic field CM every time a sector scan is performed.

[0055] As described above, according to the sensor controller 31 of this embodiment, the residual resonance of the electromagnetic induction pen 2 can be forcibly converged by the counteracting alternating magnetic field CM emitted from the EMR sensor 41, so that drawing with the electromagnetic induction pen 2 can be performed with high precision without grounding the resonant circuit within the electromagnetic induction pen 2 during the intervals between the emission of the alternating magnetic field by the sensor controller 31.

[0056] Furthermore, when the tip of the electromagnetic induction pen 2 is not in contact with the panel surface 3a (and therefore no drawing is being performed with the electromagnetic induction pen 2), the amplitude of the electromagnetic induction pen 2 can be forcibly increased by the amplified alternating magnetic field AM emitted from the EMR sensor 41, thereby enabling the sensor controller 31 to suitably receive the pen signal from the electromagnetic induction pen 2 during hover.

[0057] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0058] For example, in the above embodiment, the sensor controller 31 acquires the reception phase of the pen signal each time it receives it, based on the transmission phase of the power supply alternating magnetic field SM transmitted immediately before, and determines the transmission phases of the amplified alternating magnetic field AM and the negating alternating magnetic field CM based on the acquired reception phase. However, if an electromagnetic induction pen 2 whose resonant frequency does not change is used, the transmission phases of the amplified alternating magnetic field AM and the negating alternating magnetic field CM may be fixed. This reduces the processing load on the sensor controller 31. However, even with this type of electromagnetic induction pen 2, the resonant frequency may change depending on whether the pen 2 is located at the edge of the panel surface 3a or the distance (height) from the panel surface 3a. In such cases, the sensor controller 31 may determine the transmission phases of the amplified alternating magnetic field AM and the negating alternating magnetic field CM based on the pen signal received from the electromagnetic induction pen 2. Specifically, the transmission phases of the amplified alternating magnetic field AM and the negating alternating magnetic field CM may be determined depending on the detected position of the electromagnetic induction pen 2 and the maximum reception strength of the pen signal, which varies depending on the distance from the panel surface 3a. [Explanation of symbols]

[0059] 1. Position detection system 2. Electromagnetic induction pen 3 Position detection device 3a Panel surface 30 Switch Circuit 31 Sensor Controller 32 host processor 33 Structure 40 Touch Sensor 41 EMR sensor 42 Display AM amplified alternating magnetic field CM Cancellation alternating magnetic field PM pen alternating magnetic field SM Alternating magnetic field for power supply

Claims

1. 1. A method performed by a sensor controller for detecting an electromagnetic induction pen using an EMR sensor, comprising: a counteracting alternating magnetic field, which is an alternating magnetic field that oscillates at a phase that cancels out residual resonance of the electromagnetic induction pen, is transmitted from the EMR sensor after a predetermined time has elapsed since the EMR sensor stopped transmitting the power supply alternating magnetic field for supplying power to the electromagnetic induction pen; method.

2. the sensor controller receives a pen signal generated in the EMR sensor by an alternating magnetic field emitted from the electromagnetic induction pen within the predetermined time period; The method of claim 1.

3. After the counteracting alternating magnetic field is emitted from the EMR sensor, the power supplying alternating magnetic field is again emitted from the EMR sensor.

3. The method according to claim 1 or 2.

4. transmitting the power supply alternating magnetic field from the EMR sensor following the transmission of the canceling alternating magnetic field from the EMR sensor; The method of claim 3.

5. After the EMR sensor emits the counteracting alternating magnetic field, the EMR sensor temporarily stops emitting the alternating magnetic field, and then the EMR sensor emits the power-supplying alternating magnetic field. The method of claim 3.

6. The phase that cancels the residual resonance of the electromagnetic induction pen is a fixed value.

3. The method according to claim 1 or 2.

7. a phase value that cancels the residual resonance of the electromagnetic induction pen is a value that is determined based on a pen signal received from the electromagnetic induction pen; 3. The method according to claim 1 or 2.

8. a phase value that cancels the residual resonance of the electromagnetic induction pen is a value that is determined based on a position or height of the electromagnetic induction pen detected using a pen signal received from the electromagnetic induction pen; The method of claim 7.

9. the value of the phase that cancels the residual resonance of the electromagnetic induction pen is a value that is determined based on the phase of the pen signal received from the electromagnetic induction pen. The method of claim 7.

10. the sensor controller starts transmitting the counteracting alternating magnetic field at a timing delayed by a time corresponding to a phase that cancels out residual resonance of the electromagnetic induction pen from the timing when the predetermined time has elapsed since the EMR sensor stopped transmitting the power supply alternating magnetic field, thereby transmitting the counteracting alternating magnetic field.

3. The method according to claim 1 or 2.

11. a time corresponding to a phase that cancels the residual resonance of the electromagnetic induction pen is less than one period of the canceling alternating magnetic field; The method of claim 10.

12. the sensor controller, after a predetermined time has elapsed since the EMR sensor stopped transmitting the power supply alternating magnetic field, transmits from the EMR sensor either the canceling alternating magnetic field or an amplifying alternating magnetic field, which is an alternating magnetic field oscillating at a phase that increases the amplitude of the alternating magnetic field transmitted by the electromagnetic induction pen; 3. The method according to claim 1 or 2.

13. The sensor controller determining whether the electromagnetic induction pen is in contact with the panel surface; When it is determined that the electromagnetic induction pen is in contact with the panel surface, the counteracting alternating magnetic field is transmitted, and when it is determined that the electromagnetic induction pen is not in contact with the panel surface, the amplifying alternating magnetic field is transmitted. The method of claim 12.

14. the sensor controller determines whether the electromagnetic induction pen is in contact with a panel surface based on the writing pressure value received from the electromagnetic induction pen; The method of claim 13.

15. the sensor controller determines whether the electromagnetic induction pen is in contact with a panel surface based on a maximum reception strength of a pen signal received from the electromagnetic induction pen; The method of claim 13.

16. the sensor controller does not transmit the counteracting alternating magnetic field when the sensor controller does not detect the electromagnetic induction pen; 3. The method according to claim 1 or 2.

17. A sensor controller that detects an electromagnetic induction pen using an EMR sensor, a counteracting alternating magnetic field, which is an alternating magnetic field that oscillates at a phase that cancels out residual resonance of the electromagnetic induction pen, is transmitted from the EMR sensor after a predetermined time has elapsed since the EMR sensor stopped transmitting the power supply alternating magnetic field for supplying power to the electromagnetic induction pen; Sensor controller.

Images