Integrated circuit and position detection method

Abstract

[Problem] To improve position detection accuracy when a plurality of electromagnetic induction pens are positioned within a touch surface. [Solution] An integrated circuit according to the present invention is connected to a sensor having a configuration in which each of a plurality of X coils extending in the Y direction and each of a plurality of Y coils extending in the X direction are arranged within a touch surface. The integrated circuit is configured to repeatedly perform a position detection process for detecting the position of each of a plurality of electromagnetic induction pens within the touch surface using the sensor, wherein the position detection process involves: determining, for each electromagnetic induction pen, an alternating magnetic field transmission coil to be used to transmit an alternating magnetic field, from among the plurality of X coils and the plurality of Y coils, on the basis of the distances between the electromagnetic induction pen and other electromagnetic induction pens indicated by the positions detected by the previous position detection process; and newly detecting the position of the electromagnetic induction pen by transmitting an alternating magnetic field from the determined alternating magnetic field transmission coil.

Description

Integrated Circuit and Position Detection Method

[0001] The present invention relates to an integrated circuit and a position detection method.

[0002] One method for detecting the position of a position indicator on a touch surface is the electromagnetic induction method (EMR method). In the electromagnetic induction method, a resonance circuit composed of a coil and a capacitor connected in series is arranged inside an electromagnetic induction pen, which is a position indicator. Also, inside the touch surface of the position detection device, a plurality of X coils extending in the Y direction and a plurality of Y coils extending in the X direction are arranged respectively. When the position detection device sends out an alternating magnetic field from any one of the coils in the touch surface and the resonance circuit in the electromagnetic induction pen is located therein, an alternating magnetic field as a reflected signal is sent out from the resonance circuit in the electromagnetic induction pen. This alternating magnetic field generates an alternating current in each coil in the touch surface, and the position detection device detects the position of the electromagnetic induction pen in the touch surface based on the reception intensity of the alternating current thus generated in each coil.

[0003] Patent Document 1 discloses an example of a position detection device using the electromagnetic induction method. In this example of the position detection device, when two electromagnetic induction pens are lined up at the same position in the X direction in the touch surface, an alternating magnetic field is sent out from the Y coil closest to each of them, and when two electromagnetic induction pens are lined up at the same position in the Y direction in the touch surface, an alternating magnetic field is sent out from the X coil closest to each of them. This is a configuration invented to send out an alternating magnetic field only for a specific electromagnetic induction pen.

[0004] Japanese Patent Laid-Open No. 8-278844

[0005] However, in the method of Patent Document 1, there may be a case where the optimal alternating magnetic field is not sent out. That is, depending on the separation distance between the two electromagnetic induction pens, there is a possibility that an induced current is generated not only in one electromagnetic induction pen but also in the resonance circuit of the other electromagnetic induction pen by the alternating magnetic field sent out toward one electromagnetic induction pen. In this way, the alternating current generated in each coil will include not only the component of the alternating magnetic field from one electromagnetic induction pen but also the component of the alternating magnetic field from the other electromagnetic induction pen, and as a result, the position detection accuracy will decrease, so improvement has been required.

[0006] Therefore, one of the objectives of the present invention is to provide an integrated circuit and a position detection method that can improve the position detection accuracy when multiple electromagnetic induction pens are located within a touch surface.

[0007] The integrated circuit according to the present invention is connected to a sensor having a configuration in which a plurality of X coils and a plurality of Y coils, each extending in the Y direction, are arranged within a touch surface, and is configured to repeatedly perform a position detection process for detecting the position of each of a plurality of electromagnetic induction pens within the touch surface using the sensor, wherein the position detection process determines, for each electromagnetic induction pen, an alternating magnetic field transmitting coil to be used for transmitting an alternating magnetic field from among the plurality of X coils and the plurality of Y coils based on the distance between it and other electromagnetic induction pens indicated by the position detected in the previous position detection process, and transmits an alternating magnetic field from the determined alternating magnetic field transmitting coil to newly detect the position of the electromagnetic induction pen, the integrated circuit.

[0008] The position detection method according to the present invention is a position detection method for detecting the positions of multiple electromagnetic induction pens within a touch surface using a sensor having a configuration in which a plurality of X coils and a plurality of Y coils, each extending in the Y direction, are arranged within the touch surface, wherein a position detection process is repeatedly executed using the sensor to detect the position of each of the plurality of electromagnetic induction pens within the touch surface, and the position detection process is a process in which, for each electromagnetic induction pen, an alternating magnetic field transmitting coil to be used for transmitting an alternating magnetic field is determined from among the plurality of X coils and the plurality of Y coils based on the distance between it and the other electromagnetic induction pens indicated by the position detected in the previous position detection process, and an alternating magnetic field is transmitted from the determined alternating magnetic field transmitting coil to newly detect the position of the electromagnetic induction pen.

[0009] According to the present invention, the coil for emitting an alternating magnetic field is determined based on the distance between it and other electromagnetic induction pens indicated by the position detected in the previous position detection process. This makes it possible to improve the position detection accuracy when multiple electromagnetic induction pens are located within the touch surface.

[0010] (a) is a diagram showing the configuration of the position detection system 1 according to the first embodiment of the present invention, and (b) is a plan view of the sensor 30. This is a flowchart of the position detection process performed by the sensor controller 31 according to the first embodiment of the present invention. This is a diagram showing the details of the global scan performed in steps S2 and S3 of Figure 2. This is a diagram showing the details of the local scan 1 performed in step S4 of Figure 2. This is a diagram showing the details of the local scan 2 performed in step S5 of Figure 2. This is a diagram showing the details of the coil determination process for sending the alternating magnetic field in step S31 of Figure 5. (a) is a diagram showing an example of an X coil LX used to send an alternating magnetic field to pen 2a when pens 2a and 2b are aligned in the X direction, and (b) is a diagram showing an example of an X coil LX and a Y coil LY used to receive the alternating magnetic field sent from pen 2a after receiving this alternating magnetic field. (a) is a diagram showing an example of an X coil LX used to send an alternating magnetic field to pen 2b when pens 2a and 2b are aligned in the X direction, and (b) is a diagram showing an example of an X coil LX and a Y coil LY used to receive the alternating magnetic field sent out from pen 2b in response to this alternating magnetic field. (a) is a diagram showing an example of a Y coil LY used to send an alternating magnetic field to pen 2a when pens 2a and 2b are aligned in the Y direction, and (b) is a diagram showing an example of an X coil LX and a Y coil LY used to receive the alternating magnetic field sent out from pen 2a in response to this alternating magnetic field. (a) is a diagram showing an example of a Y coil LY used to send an alternating magnetic field to pen 2b when pens 2a and 2b are aligned in the Y direction, and (b) is a diagram showing an example of an X coil LX and a Y coil LY used to receive the alternating magnetic field sent out from pen 2b in response to this alternating magnetic field. This is a flowchart of the position detection process performed by the sensor controller 31 according to the second embodiment of the present invention. This figure shows the details of the local scan 3 performed in step S7 of Figure 11. This figure shows the details of the alternating magnetic field transmission coil determination process performed in step S61 of Figure 12. This figure shows the details of the non-separated reception coil determination process performed in step S74 of Figure 13. This figure shows the details of the separated reception coil determination process 1 performed in step S76 of Figure 13.This figure shows the details of the separated reception coil determination process 2 performed in step S78 of Figure 13. (a) is a figure showing an example of an X coil LX used to send an alternating magnetic field to pen 2a when pens 2a and 2b are aligned in the X direction and pens 2a and 2c are aligned in the Y direction, and (b) is a figure showing an example of a Y coil LY used to receive the alternating magnetic field sent out from pen 2a after receiving this alternating magnetic field. (a) is a figure showing an example of a Y coil LY used to send an alternating magnetic field to pen 2a when pens 2a and 2b are aligned in the X direction and pens 2a and 2c are aligned in the Y direction, and (b) is a figure showing an example of an X coil LX used to receive the alternating magnetic field sent out from pen 2a after receiving this alternating magnetic field. (a) is a diagram showing an example of an X coil LX used to send an alternating magnetic field to pen 2a when pens 2a and 2b are aligned in the Y direction and pens 2a and 2c are aligned in the X direction, and (b) is a diagram showing an example of a Y coil LY used to receive the alternating magnetic field sent out from pen 2a in response to this alternating magnetic field. (a) is a diagram showing an example of a Y coil LY used to send an alternating magnetic field to pen 2a when pens 2a and 2b are aligned in the Y direction and pens 2a and 2c are aligned in the X direction, and (b) is a diagram showing an example of an X coil LX used to receive the alternating magnetic field sent out from pen 2a in response to this alternating magnetic field. This is a flowchart of a local scan 2 performed by a sensor controller 31 according to a third embodiment of the present invention. This is a diagram showing the details of the separated reception coil determination process 3 performed in step S113 of Figure 21. (a) is a diagram showing an example of an X coil LX used to send an alternating magnetic field to pen 2a when pens 2a and 2b are arranged diagonally, and (b) is a diagram showing an example of a Y coil LY used to receive the alternating magnetic field sent out from pen 2a in response to this alternating magnetic field. (a) is a diagram showing an example of a Y coil LY used to send an alternating magnetic field to pen 2a when pens 2a and 2b are arranged diagonally, and (b) is a diagram showing an example of an X coil LX used to receive the alternating magnetic field sent out from pen 2a in response to this alternating magnetic field.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0012] Figure 1(a) shows the configuration of a position detection system 1 according to a first embodiment of the present invention. As shown in the figure, the position detection system 1 has a plurality of pens 2, including pens 2a and 2b, and a position detection device 3, and is configured to detect the positions of the plurality of pens 2 on a flat touch surface 3a provided on the position detection device 3 by the electromagnetic induction method described above. In this embodiment, the explanation continues assuming that the sensor controller 31 can simultaneously detect a maximum of two pens 2.

[0013] Each of the multiple pens 2 is an electromagnetic induction pen that incorporates a resonant circuit consisting of a coil 20 and a capacitor 21 connected in series. This resonant circuit accumulates charge in the capacitor 21 by the induced current generated in the coil 20 by the alternating magnetic field emitted by the position detection device 3, and after the emission of the alternating magnetic field by the position detection device 3 stops, it uses the charge accumulated in the capacitor 21 to emit an alternating magnetic field as a reflected signal from the coil 20.

[0014] The position detection device 3 is an electronic device that has the function of detecting the position of each of the multiple pens 2 on the touch surface 3a, and as shown in Figure 1(a), it is configured to include a sensor 30, a sensor controller 31, and a host processor 32. The position detection device 3 may be an electronic device in which the touch surface 3a also serves as a display surface, such as a tablet terminal, smartphone, or notebook computer, or it may be an electronic device in which the touch surface 3a does not serve as a display surface, such as a digitizer.

[0015] Figure 1(b) is a plan view of the sensor 30. As shown in the figure, the sensor 30 is composed of a plurality of X coils LX, each extending in the Y direction and arranged in the X direction, and a plurality of Y coils LY, each extending in the X direction and arranged in the Y direction. The plurality of X coils LX and the plurality of Y coils LY are arranged within the touch surface 3a, and both ends of each are connected to the sensor controller 31. Note that in Figure 1(b), for the sake of clarity, eight X coils LX are shown as the plurality of X coils LX. １ ~LX８ It only depicts the eight Y-coils LY, as multiple Y-coils LY. １ ~LY ８ Although only one is depicted, the actual sensor 30 is equipped with more X coils LX and Y coils LY.

[0016] The sensor controller 31 is an integrated circuit configured to repeatedly perform position detection processing to newly detect or update the position of each of the multiple pens 2 within the touch surface 3a using the sensor 30. The sensor controller 31 is configured to sequentially supply the newly detected or updated positions of the pens 2 to the host processor 32. The position detection processing performed by the sensor controller 31 will be explained in detail later with reference to Figures 2 to 9.

[0017] The host processor 32 is the central processing unit of the position detection device 3 and is configured to execute programs stored in a storage device (not shown). The programs executed by the host processor 32 include the operating system of the position detection device 3 and various applications, including a drawing application that performs drawing processing based on the position of the pen 2 repeatedly supplied from the sensor controller 31.

[0018] Figures 2 to 6 are flowcharts of the position detection process performed by the sensor controller 31. Figures 7 to 10 show examples of coils used for transmitting and receiving alternating magnetic fields. The position detection process performed by the sensor controller 31 will be described in detail below with reference to these figures.

[0019] First, referring to Figure 2, the sensor controller 31 first determines the number of pens 2 being detected (step S1). If there are 0 pens, it performs a global scan (step S2) to detect pens 2 across the entire touch surface 3a. If there is 1 pen, it performs a global scan (step S3) and a local scan 1 (step S4) to update the position of the detected pen 2 in a time-division manner. If there are 2 pens, it performs a local scan 2 (step S5) to update the positions of the two detected pens 2.

[0020] Figure 3 shows the details of the global scan performed in steps S2 and S3 of Figure 2. As shown in the figure, the sensor controller 31 first sends out an alternating magnetic field from all X coils LX (or all Y coils LY) (step S10). It may be predetermined whether to use X coils LX or Y coils LY as the coils for sending out the alternating magnetic field. Next, after stopping the transmission of the alternating magnetic field, the sensor controller 31 attempts to detect alternating current in all X coils LX and Y coils LY and stores the current value (step S11). Then, the sensor controller 31 attempts to derive the position of pen 2 based on the current value stored in step S11 (step S12). This derivation can be performed by generating a two-dimensional distribution of current values ​​and using its peak position as the coordinate of pen 2.

[0021] Next, the sensor controller 31 determines whether or not a new pen 2 has been detected based on the trial results of deriving the position of pen 2 (step S13). The result of this determination is positive if a global scan was performed in step S2 of Figure 2, and negative if the position of pen 2 could be derived in step S12, and negative if it could not. Also, if a global scan was performed in step S3 of Figure 2, the result is positive if the position of pen 2 could be derived in step S12 and that position is more than a predetermined distance away from the latest position of the already detected pen 2 (the position detected by local scan 1), and negative otherwise.

[0022] If the sensor controller 31 obtains a negative result in step S13, it terminates the global scan. On the other hand, if the sensor controller 31 obtains a positive result in step S13, it assigns a local ID to the newly detected pen 2 (step S14). The local ID is identification information for distinguishing between multiple pens 2 on the touch surface 3a, and if the sensor controller 31 can detect a maximum of two pens 2 simultaneously, it may be a single bit of information. Once the assignment of the local ID is complete, that pen 2 will be treated as the pen 2 being detected in the determination in step S1 of Figure 2.

[0023] Next, the sensor controller 31 stores the position derived in step S12 in association with the local ID assigned in step S14 (step S15). The sensor controller 31 also outputs the position derived in step S12, along with the local ID assigned in step S14, to the host processor 32 (step S16). With these steps completed, the global scan is finished.

[0024] Figure 4 shows the details of the local scan 1 performed in step S4 of Figure 2. As shown in the figure, the sensor controller 31 first selects an X coil LX (or Y coil LY) for transmitting an alternating magnetic field and a predetermined number of X coils LX and Y coils LY for receiving, based on the previously stored position (step S20). Here, the sensor controller 31 should select the X coil LX (or Y coil LY) closest to the previously detected position of the pen 2 as the coil for transmitting the alternating magnetic field. Note that it may be decided in advance whether to use an X coil LX or a Y coil LY as the coil for transmitting the alternating magnetic field. The sensor controller 31 should also select a predetermined number of X coils LX and Y coils LY in order of proximity to the previously detected position of the pen 2 as the coils for receiving.

[0025] Next, the sensor controller 31 emits an alternating magnetic field from the alternating magnetic field emission coil selected in step S20 (step S21). After stopping the emission of the alternating magnetic field, the sensor controller 31 attempts to detect alternating current in each of the receiving coils selected in step S20 and stores the current value (received strength) (step S22). Then, the sensor controller 31 attempts to derive the position of the pen 2 based on the current value stored in step S22 (step S23). This derivation can also be performed by generating a two-dimensional distribution of current values ​​(a two-dimensional distribution with a narrower range than the two-dimensional distribution used in step S12 of Figure 3) and using its peak position as the coordinates of the pen 2.

[0026] Next, the sensor controller 31 determines whether or not the position of the pen 2 was derived in step S23 (step S24). If the sensor controller 31 obtains a negative result in this determination, it determines whether or not the negative determination in step S24 has continued for a predetermined number of times (step S27). If it determines that it has continued, it releases the assignment of the local ID and notifies the host processor 32 of the release (step S28), and terminates local scan 1. If the sensor controller 31 determines in step S27 that it has not continued, it terminates local scan 1 without performing the process in step S28.

[0027] Meanwhile, the sensor controller 31, having obtained a positive result in step S24, stores the position derived in step S23 in association with the corresponding local ID (step S25). The sensor controller 31 also outputs the position derived in step S23 along with the corresponding local ID to the host processor 32 (step S16), and terminates local scan 1.

[0028] Figure 5 shows the details of the local scan 2 performed in step S5 of Figure 2. As shown in the figure, the sensor controller 31 performs the processes of steps S31 to S40 for each of the pens 2 being detected (step S30). Specifically, the sensor controller 31 first performs a coil determination process for alternating magnetic field output to select either the X coil LX or the Y coil LY for outputting the alternating magnetic field, based on the distance between it and other pens 2 indicated by the position detected by the previous position detection process (including global scan, local scan 1, and local scan 2) (step S31).

[0029] Figure 6 shows the details of the process for determining the alternating magnetic field transmission coil, which is performed in step S31 of Figure 5. Figures 7(a), 8(a), 9(a), and 10(a) show examples of the alternating magnetic field transmission coil selected in step S31. The process for determining the alternating magnetic field transmission coil will be explained in detail below with reference to these figures.

[0030] First, looking at Figures 7(a) and 8(a), in these examples, the pens 2a and 2b are placed close together in the X direction. In this case, the separation distance DX in the X direction between the two pens 2a and 2b is greater than 0, and the separation distance DY in the Y direction is approximately 0. Also, looking at Figures 9(a) and 10(a), in these examples, the pens 2a and 2b are placed close together in the Y direction. In this case, the separation distance DY in the Y direction between the two pens 2a and 2b is greater than 0, and the separation distance DX in the X direction is approximately 0. The sensor controller 31 uses this relationship between the separation distances DX and DY to determine the coil for transmitting the alternating magnetic field.

[0031] Referring to Figure 6, the sensor controller 31 first determines the distance DX in the X direction and the distance DY in the Y direction between the two pens 2a and 2b based on the previously detected positions (step S50). Next, the sensor controller 31 determines whether DX ≥ DY is true (step S51).

[0032] As shown in the examples in Figures 7(a) and 8(a), when DX ≥ DY is true, the sensor controller 31 determines whether the separation distance DX is less than a predetermined threshold T1 (whether DX < T1 is true) (step S52). The threshold T1 is a value predetermined based on the maximum distance that an alternating magnetic field emitted from a coil reaches the resonant circuit in the pen 2. If DX < T1 is not true (i.e., DX ≥ T1), it can be expected that the alternating magnetic field emitted from the X coil LX closest to a pen 2 will not be received by the other pen 2.

[0033] If the sensor controller 31 determines in step S52 that DX < T1 does not hold true, it selects the X coil LX closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S54). On the other hand, if the sensor controller 31 determines in step S52 that DX < T1 holds true, it selects an X coil LX that is further from the other pens 2 than the X coil LX closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S53). Figure 7(a) shows the X coil LX selected in step S53 when the pen 2 of interest is pen 2a with a thick line, and Figure 8(a) shows the X coil LX selected in step S53 when the pen 2 of interest is pen 2b with a thick line. This reduces the possibility that the alternating magnetic field transmitted to the pen 2 of interest may be received by the other pens 2.

[0034] On the other hand, if DX ≥ DY does not hold true, as in the examples of Figure 9(a) and Figure 10(a), the sensor controller 31 determines whether the separation distance DY is smaller than the threshold T1 (whether DY < T1 holds true) (step S55).

[0035] If the sensor controller 31 determines in step S55 that DY < T1 does not hold true, it selects the Y coil LY closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S57). On the other hand, if the sensor controller 31 determines in step S55 that DY < T1 holds true, it selects a Y coil LY that is further from other pens 2 than the Y coil LY closest to pen 2 as the coil for transmitting the alternating magnetic field (step S58). Figure 9(a) shows the Y coil LY selected in step S56 when the pen 2 of interest is pen 2a with a thick line, and Figure 10(a) shows the Y coil LY selected in step S56 when the pen 2 of interest is pen 2b with a thick line. This reduces the possibility that the alternating magnetic field transmitted to the pen 2 of interest may be received by other pens 2.

[0036] Returning to Figure 5, the sensor controller 31 then selects a predetermined number of X coils LX and Y coils LY for receiving based on the previously stored position of the pen 2 under interest (step S32). In this selection, the sensor controller 31 can select the predetermined number of X coils LX and Y coils LY in order of proximity to the previously detected position of the pen 2, similar to step S20 in Figure 4. Figures 7(b), 8(b), 9(b), and 10(b) show examples of the receiving coils selected in step S32, corresponding to Figures 7(a), 8(a), 9(a), and 10(a), respectively.

[0037] Next, the sensor controller 31 emits an alternating magnetic field from the alternating magnetic field emission coil selected in step S31 (step S33). After stopping the emission of the alternating magnetic field, the sensor controller 31 attempts to detect alternating current in each of the receiving coils selected in step S32 and stores the current value (step S34). Then, the sensor controller 31 attempts to derive the position of the pen 2 based on the current value stored in step S34 (step S35). This derivation can also be performed by generating a two-dimensional distribution of current values ​​and using the peak position as the coordinate of the pen 2, similar to steps S12 and S23 in Figure 3.

[0038] Next, the sensor controller 31 determines whether or not it was able to derive the position of the pen of interest 2 in step S35 (step S36). If the sensor controller 31 obtains a negative result in this determination, it determines whether or not the negative determination in step S36 has continued for a predetermined number of times (step S39). If it determines that it has continued, it releases the assignment of the local ID to the pen of interest 2 and notifies the host processor 32 of the release (step S40), and proceeds to the processing of the next pen 2. If the sensor controller 31 determines in step S39 that it has not continued, it proceeds to the processing of the next pen 2 without performing the processing in step S40.

[0039] On the other hand, the sensor controller 31 that obtained a positive result in step S36 stores the position derived in step S35 in association with the corresponding local ID (step S37). Further, the sensor controller 31 outputs the position derived in step S35 to the host processor 32 together with the corresponding local ID (step S38), and proceeds to the next processing of the pen 2.

[0040] As described above, in the position detection system 1 according to the present embodiment, the alternating magnetic field transmission coil is determined based on the distance to another pen 2 indicated by the position detected by the previous position detection process. Therefore, according to the position detection system 1 according to the present embodiment, it is possible to reduce the possibility that the alternating magnetic field transmitted for one pen 2 is received by the other pen 2, so that when a plurality of pens 2 are located in the touch surface 3a, the position detection accuracy can be improved.

[0041] Next, the position detection system 1 according to the second embodiment of the present invention will be described. The position detection system 1 according to the present embodiment is different from the position detection system 1 according to the first embodiment in that the maximum number of pens 2 that the sensor controller 31 can detect simultaneously is three. Since other points are the same as those of the position detection system 1 according to the first embodiment, the description will be continued below focusing on the differences from the position detection system 1 according to the first embodiment.

[0042] Figs. 11 to 16 are flowcharts of the position detection process executed by the sensor controller 31 according to the present embodiment. Figs. 17 to 20 are diagrams showing examples of coils used for transmitting and receiving an alternating magnetic field. Hereinafter, the position detection process executed by the sensor controller 31 according to the present embodiment will be described in detail with reference to these figures.

[0043] First, referring to Fig. 11, the process shown in the figure is different from the process shown in Fig. 2 in that a global scan (step S6) is executed when the determination result in step S2 is two, and a local scan 3 (step S7) is executed when the determination result in step S2 is three.

[0044] FIG. 12 is a diagram showing details of the local scan 3 executed in step S7 of FIG. 11. As shown in this figure, for each of the pens 2 being detected, the sensor controller 31 executes the processes of steps S61 to S67 (step S60). More specifically, the sensor controller 31 first performs an alternating magnetic field transmission coil determination process for selecting the X coil LX or the Y coil LY for alternating magnetic field transmission based on the distance from the other pens 2 indicated by the position detected by the previous position detection process (including the global scan, the local scan 1, and the local scan 2) (step S61).

[0045] FIG. 13 is a diagram showing details of the alternating magnetic field transmission coil determination process executed in step S61 of FIG. 12. However, in this figure and FIGS. 14 to 16, for the sake of easy understanding of the explanation, it is assumed that the pen of interest is pen 2a and the other two pens 2 are pens 2b and 2c.

[0046] First, the sensor controller 31 derives the separation distances DXb, DYb, Dxc, and DYc between the pen 2a and each of the other two pens 2b and 2c based on the previously detected position (step S70). The separation distance DXb is the separation distance in the X direction between pens 2a and 2b, and the separation distance DYb is the separation distance in the Y direction between pens 2a and 2b. The separation distance Dxc is the separation distance in the X direction between pens 2a and 2c, and the separation distance DYc is the separation distance in the Y direction between pens 2a and 2c.

[0047] Next, the sensor controller 31 determines whether DXb < T2 and DYc < T2 are satisfied (step S71). If it is determined that they are not satisfied, it further determines whether DYb < T2 and Dxc < T2 are satisfied (step S72). T2 is the maximum separation distance when the closest coils to each of the two pens 2 are the same.

[0048] Figures 17(a) and 18(a) show the arrangement of pens 2a to 2c when DYb < T2 and DXc < T2 are satisfied. As in this example, when the Y coordinates of pens 2a and 2b are nearly identical and the X coordinates of pens 2a and 2c are nearly identical, DYb < T2 and DXc < T2 are satisfied. Also, Figures 19(a) and 20(a) show the arrangement of pens 2a to 2c when DXb < T2 and DYc < T2 are satisfied. As in this example, when the X coordinates of pens 2a and 2b are nearly identical and the Y coordinates of pens 2a and 2c are nearly identical, DXb < T2 and DYc < T2 are satisfied.

[0049] Return to Figure 13. If it is determined that the condition is not met in step S72, the sensor controller 31 sets the separated reception flag to False (step S73) and executes the non-separated reception coil determination process (step S74). The separated reception flag is a Boolean variable that is False when an alternating magnetic field is transmitted only once from either the X coil or the Y coil each time a position is detected (i.e., reception with the X coil and reception with the Y coil are performed simultaneously), and True when an alternating magnetic field is transmitted from both the X coil and the Y coil each time a position is detected (i.e., reception with the Y coil and reception with the X coil are performed separately).

[0050] If it is determined that the condition is met in step S72, the sensor controller 31 sets the separation reception flag to True (step S75) and executes the separation reception coil determination process 1 (step S76). If it is determined that the condition is met in step S71, the sensor controller 31 sets the separation reception flag to True (step S77) and executes the separation reception coil determination process 2 (step S78).

[0051] Figure 14 shows the details of the coil determination process during non-separated reception, which is performed in step S74 of Figure 13. As shown in the figure, the sensor controller 31 first determines the smallest of the separation distances DXb, DYb, DXc, and DYc calculated in step S70 of Figure 13 (step S80). Figure 14 shows only the case where the determination result is the separation distance DXb, but the same applies to other cases. The following explanation will focus on the case where the determination result in step S80 is the separation distance DXb.

[0052] If the result of step S80 is the separation distance DXb, the sensor controller 31 determines whether the separation distance DXb is smaller than the threshold T1 described above (whether DXb < T1 is true) (step S81). If it is determined that DXb < T1 is not true, the sensor controller 31 selects the X coil LX closest to the pen 2a as the coil for transmitting the alternating magnetic field (step S84).

[0053] On the other hand, if the sensor controller 31 determines in step S81 that DXb < T1 is true, it determines whether the X coil LX that is one unit further from pen 2b than the X coil LX closest to pen 2a is sufficiently far from pen 2c (step S82). This determination is made to avoid a situation where the alternating magnetic field emitted from the alternating magnetic field emission coil is received by pen 2c as a result of shifting the alternating magnetic field emission coil so that it is not received by pen 2b. If it is determined in step S82 that it is not sufficiently far, the sensor controller 31 moves the process to step S84 and selects the X coil LX closest to pen 2a as the alternating magnetic field emission coil. On the other hand, if it is determined in step S82 that it is sufficiently far, the sensor controller 31 selects the X coil LX that is one unit further from pen 2b than the X coil LX closest to pen 2a as the alternating magnetic field emission coil (step S83). This makes it possible to reduce the possibility that the alternating magnetic field emitted to pen 2a is received by pens 2b and 2c.

[0054] Figure 15 shows the details of the separated reception coil determination process 1 performed in step S76 of Figure 13. As shown in the figure, the sensor controller 31 first determines whether the separation distance DXb is less than the threshold T1 (whether DXb < T1 is true) (step S90). If it is determined that DXb < T1 is not true, the sensor controller 31 selects the X coil LX closest to the pen 2a as the coil for transmitting the alternating magnetic field (step S92). On the other hand, if the sensor controller 31 determines in step S90 that DXb < T1 is true, it selects the X coil LX that is further from the pen 2b than the X coil LX closest to the pen 2a as the coil for transmitting the alternating magnetic field (step S91). In Figure 17(a), the X coil LX thus selected is shown by a thick line.

[0055] Next, the sensor controller 31 determines whether the separation distance DYc is less than the threshold T1 (whether DYc < T1 is true) (step S93). If it determines that DYc < T1 is not true, the sensor controller 31 selects the Y coil LY closest to the pen 2a as the coil for transmitting the alternating magnetic field (step S95). On the other hand, if the sensor controller 31 determined in step S93 that DYc < T1 is true, it selects the Y coil LY that is further from the pen 2c than the Y coil LY closest to the pen 2a as the coil for transmitting the alternating magnetic field (step S94). In Figure 18(a), the Y coil LY thus selected is shown by a thick line.

[0056] Figure 16 shows the details of the separated reception coil determination process 2, which is performed in step S78 of Figure 13. As can be seen by comparing Figure 16 and Figure 15, the separated reception coil determination process 2 is basically the same as the separated reception coil determination process 1. Briefly, the sensor controller 31 first determines whether DXc < T1 is true or not (step S100). If it is determined that it is not true, it selects the X coil LX closest to pen 2a as the coil for transmitting the alternating magnetic field (step S102). On the other hand, if it is determined that it is true, it selects the X coil LX that is further from pen 2c than the X coil LX closest to pen 2a as the coil for transmitting the alternating magnetic field (step S101). In Figure 19(a), the X coil LX thus selected is shown by a thick line.

[0057] Next, the sensor controller 31 determines whether DYb < T1 is true (step S103). If it determines that it is not true, it selects the Y coil LY closest to pen 2a as the coil for transmitting the alternating magnetic field (step S105). On the other hand, if it determines that it is true, it selects the Y coil LY that is further from pen 2b than the Y coil LY closest to pen 2a as the coil for transmitting the alternating magnetic field (step S104). In Figure 20(a), the Y coil LY thus selected is shown by a thick line.

[0058] Returning to Figure 12, the sensor controller 31, having completed the process of determining the alternating magnetic field transmission coil in step S61 as described above, selects a predetermined number of X coils LX and Y coils LY for reception, similar to step S32 in Figure 5, based on the previous position of the pen of interest 2 that it has stored (step S62).

[0059] Next, the sensor controller 31 determines the value of the separation reception flag (step S63). If the separation reception flag is found to be False, the sensor controller 31 detects the position of the target pen 2 by performing the same processing as in steps S33 to S40 shown in Figure 5.

[0060] On the other hand, if the separation reception flag is True, the sensor controller 31 sends out an alternating magnetic field from the X coil for sending out the alternating magnetic field (step S64). This X coil is the "first alternating magnetic field sending coil" selected in steps S91 and S92 in Figure 15 or in steps S101 and S102 in Figure 16. After that, the sensor controller 31 stops sending out the alternating magnetic field and then attempts to detect the alternating current in each of the Y coils for receiving selected in step S62 and stores the current value (step S65). In Figures 17(b) and 19(b), the Y coils used for receiving in step S65 are shown with thick lines.

[0061] Next, the sensor controller 31 sends out an alternating magnetic field from the Y coil for sending out the alternating magnetic field (step S66). This Y coil is the "second alternating magnetic field sending coil" selected in steps S94 and S95 of Figure 15 or in steps S104 and S105 of Figure 16. After that, the sensor controller 31 stops sending out the alternating magnetic field and then attempts to detect an alternating current in each of the X coils for receiving selected in step S62 and stores the current value (step S67). In Figures 18(b) and 20(b), the Y coils used for receiving in step S67 are shown with thick lines.

[0062] The subsequent processing is the same as steps S35 to S40 shown in Figure 5. As can be understood from the processing in steps S64 to S67, when the separated reception flag is True, the sensor controller 31 separates the reception at the Y coil and the reception at the X coil each time a position is detected. By separating the reception in this way, it becomes possible to accurately determine the position of pen 2 even when other pens 2 are adjacent to pen 2a in both the X and Y directions, as shown in Figures 17 to 20.

[0063] As described above, the position detection system 1 according to this embodiment makes it possible to detect the position of each pen 2 with high accuracy, even when using three pens 2 simultaneously.

[0064] Next, a position detection system 1 according to a third embodiment of the present invention will be described. The position detection system 1 according to this embodiment differs from the position detection system 1 according to the first embodiment in terms of the specific processing content of the local scan 2 performed in step S5 of Figure 2. In other respects, it is the same as the position detection system 1 according to the first embodiment, so the following description will focus on the differences from the position detection system 1 according to the first embodiment.

[0065] Figures 21 and 22 are flowcharts of the position detection process performed by the sensor controller 31 according to this embodiment. Figures 23 and 24 show examples of coils used for transmitting and receiving alternating magnetic fields. The position detection process performed by the sensor controller 31 according to this embodiment will be described in detail below with reference to these figures.

[0066] First, referring to Figure 21, the figure shows the details of the local scan 2 performed by the sensor controller 31 according to this embodiment. As shown in the figure, the sensor controller 31 according to this embodiment performs the processes of steps S111 to S113 for each of the pens 2 being detected (step S110). Specifically, the sensor controller 31 first determines whether the pen of interest 2 is a newly detected pen 2 or not (step S111), and if it is determined that it is not a newly detected pen 2, it further determines whether detection failed in the previous local scan (including local scans 1 and 2) (step S112). The determination result in step S112 is affirmative if the determination in step S36 shown in Figure 5 was negative in the previous local scan 2.

[0067] If it is determined that there was no failure in step S112, the sensor controller 31 executes steps S31 to S40 in Figure 6 and proceeds to the next processing of pen 2. On the other hand, if it is determined in step S111 that the pen 2 is newly detected, or if it is determined that there was a failure in step S112, the sensor controller 31 executes the separated reception coil determination process 3 (step S113).

[0068] Figure 22 shows the details of the coil determination process 3 during separation and reception, which is performed in step S113 of Figure 21. As shown in the figure, the sensor controller 31 first determines the separation distance DX in the X direction and the separation distance DY in the Y direction of the two pens 2a and 2b based on the previously detected positions (step S120).

[0069] Next, the sensor controller 31 determines whether DX < T1 is true (step S121). If it determines that it is not true, it selects the X coil LX closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S123). If it determines that it is true, it selects an X coil LX that is further from the other pens 2 than the X coil LX closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S122). In Figure 23(a), the X coil LX selected in step S122 when the pen 2 of interest is pen 2a is shown in bold.

[0070] Next, the sensor controller 31 determines whether DY < T1 is true (step S124). If it determines that it is not true, it selects the Y coil LY closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S126). If it determines that it is true, it selects a Y coil LY that is further from the other pens 2 than the Y coil LY closest to the pen 2 of interest as the coil for transmitting the alternating magnetic field (step S125). In Figure 24(a), the Y coil LY selected in step S125 when the pen 2 of interest is pen 2a is shown in bold.

[0071] Returning to Figure 21, the sensor controller 31, having completed the coil determination process 3 during separated reception in step S113, performs the same process as in steps S64 to S67 in Figure 12, and further performs the same process as in steps S35 to S40 in Figure 6, thereby performing position detection using the separation of reception by the Y coil and reception by the X coil. In Figure 23(b), the Y coil used for reception in step S65 when the pen of interest 2 is pen 2a is shown with a thick line, and in Figure 24(b), the X coil used for reception in step S67 when the pen of interest 2 is pen 2a is shown with a thick line.

[0072] As explained above, the position detection system 1 according to this embodiment employs separation of reception by the Y coil and reception by the X coil for newly detected pens 2 and pens 2 that were previously undetected. This makes it possible to reliably detect such pens 2 compared to when this system is not used. Therefore, it becomes possible to further improve the position detection accuracy when multiple pens 2 are located within the touch surface 3a.

[0073] Although preferred embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, and it goes without saying that the present invention can be implemented in various forms without departing from its essence.

[0074] 1 Position detection system 2, 2a-2c Pen 3 Position detection device 3a Touch surface 20 Coil 21 Capacitor 30 Sensor 31 Sensor controller 32 Host processor LX X coil LY Y coil

Claims

1. An integrated circuit connected to a sensor having a configuration in which a plurality of X coils and a plurality of Y coils, each extending in the Y direction, are arranged within a touch surface, wherein the integrated circuit is configured to repeatedly perform a position detection process for detecting the position of each of a plurality of electromagnetic induction pens within the touch surface using the sensor, wherein the position detection process determines, for each electromagnetic induction pen, an alternating magnetic field transmitting coil to be used for transmitting an alternating magnetic field from among the plurality of X coils and the plurality of Y coils based on the distance between it and other electromagnetic induction pens indicated by the position detected by the previous position detection process, and detects the position of the electromagnetic induction pen anew by transmitting an alternating magnetic field from the determined alternating magnetic field transmitting coil.

2. The integrated circuit according to claim 1, wherein the position detection process involves determining, for each electromagnetic induction pen, a predetermined number of X coils and Y coils to be used as receiving coils to receive the alternating magnetic field emitted by the electromagnetic induction pen, based on the position of the electromagnetic induction pen in the previous position detection process, and then detecting an alternating current in the determined receiving coils after emitting an alternating magnetic field from the determined alternating magnetic field transmitting coils, thereby newly detecting the position of the electromagnetic induction pen.

3. The integrated circuit according to claim 2, wherein the position detection process involves determining one of the X coils or one of the Y coils for each electromagnetic induction pen as the alternating magnetic field transmission coil, and using the predetermined number of X coils and Y coils determined as the receiving coils, receiving the alternating magnetic field transmitted from the alternating magnetic field transmission coil to the alternating magnetic field transmitted from the alternating magnetic field transmission coil.

4. The integrated circuit according to claim 2, wherein the position detection process involves determining, for each of the electromagnetic induction pens, one X coil and one Y coil to be the alternating magnetic field transmitting coil, using a predetermined number of X coils determined to be the receiving coils to receive the alternating magnetic field transmitted from the Y coil determined to be the alternating magnetic field transmitting coil, and using a predetermined number of Y coils determined to be the receiving coils to receive the alternating magnetic field transmitted from the X coil determined to be the alternating magnetic field transmitting coil.

5. The position detection process is as follows: For each electromagnetic induction pen, if the X coil closest to the electromagnetic induction pen is the same as one of the other two electromagnetic induction pens being detected, and the Y coil closest to the electromagnetic induction pen is the same as the other of the other two electromagnetic induction pens being detected, then one of the X coils and one of the Y coils are determined to be the alternating magnetic field transmitting coils; the alternating magnetic field transmitted from the electromagnetic induction pen is received by the alternating magnetic field transmitted from the Y coil determined to be the alternating magnetic field transmitting coil using the predetermined number of X coils determined to be the receiving coils; and the alternating magnetic field transmitted from the electromagnetic induction pen is received by the alternating magnetic field transmitted from the X coil determined to be the alternating magnetic field transmitting coil using the predetermined number of Y coils determined to be the receiving coils.

6. The integrated circuit according to claim 4, wherein the position detection process, for each of the electromagnetic induction pens, determines one of the X coils and one of the Y coils as the alternating magnetic field transmitting coils when the electromagnetic induction pen is a newly detected pen; uses a predetermined number of X coils determined as receiving coils to receive the alternating magnetic field transmitted from the Y coil determined as the alternating magnetic field transmitting coils; and uses a predetermined number of Y coils determined as receiving coils to receive the alternating magnetic field transmitted from the X coil determined as the alternating magnetic field transmitting coils.

7. The integrated circuit according to claim 4, wherein the position detection process, for each of the electromagnetic induction pens, if the position detection of the electromagnetic induction pen failed in the previous position detection process, determines one of the X coils and one of the Y coils to be used as the alternating magnetic field transmitting coils, uses a predetermined number of X coils determined as receiving coils to receive the alternating magnetic field transmitted from the Y coil determined as the alternating magnetic field transmitting coil, and uses a predetermined number of Y coils determined as receiving coils to receive the alternating magnetic field transmitted from the X coil determined as the alternating magnetic field transmitting coil.

8. The integrated circuit according to claim 1, wherein the plurality of electromagnetic induction pens include a first electromagnetic induction pen and a second electromagnetic induction pen, and the integrated circuit determines the X coil that is further from the second electromagnetic induction pen than the X coil closest to the first electromagnetic induction pen as the alternating magnetic field transmitting coil used to detect the position of the first electromagnetic induction pen, and determines the X coil that is further from the first electromagnetic induction pen than the X coil closest to the second electromagnetic induction pen as the alternating magnetic field transmitting coil used to detect the position of the second electromagnetic induction pen.

9. The integrated circuit, when the distance in the X direction between the first electromagnetic induction pen and the second electromagnetic induction pen, indicated by the position detected by the previous position detection process, is less than a predetermined value, determines the X coil that is further from the second electromagnetic induction pen than the X coil that is closest to the first electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the first electromagnetic induction pen; determines the X coil that is further from the first electromagnetic induction pen than the X coil that is closest to the second electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the second electromagnetic induction pen; when the distance in the X direction between the first electromagnetic induction pen and the second electromagnetic induction pen, indicated by the position detected by the previous position detection process, is greater than or equal to a predetermined value, determines the X coil that is closest to the first electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the first electromagnetic induction pen; determines the X coil that is closest to the second electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the second electromagnetic induction pen. The integrated circuit according to claim 8.

10. The integrated circuit according to claim 1, wherein the plurality of electromagnetic induction pens include a first electromagnetic induction pen and a second electromagnetic induction pen, and the integrated circuit determines the Y coil that is further from the second electromagnetic induction pen than the Y coil closest to the first electromagnetic induction pen as the alternating magnetic field transmitting coil used to detect the position of the first electromagnetic induction pen, and determines the Y coil that is further from the first electromagnetic induction pen than the Y coil closest to the second electromagnetic induction pen as the alternating magnetic field transmitting coil used to detect the position of the second electromagnetic induction pen.

11. The integrated circuit, when the Y-direction separation distance between the first electromagnetic induction pen and the second electromagnetic induction pen, indicated by the position detected by the previous position detection process, is less than a predetermined value, determines the Y-coil that is further from the second electromagnetic induction pen than the Y-coil that is closest to the first electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the first electromagnetic induction pen; determines the Y-coil that is further from the first electromagnetic induction pen than the Y-coil that is closest to the second electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the second electromagnetic induction pen; when the Y-direction separation distance between the first electromagnetic induction pen and the second electromagnetic induction pen, indicated by the position detected by the previous position detection process, is greater than or equal to a predetermined value, determines the Y-coil that is closest to the first electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the first electromagnetic induction pen; determines the Y-coil that is closest to the second electromagnetic induction pen as the alternating magnetic field transmission coil used to detect the position of the second electromagnetic induction pen. The integrated circuit according to claim 10.

12. A position detection method for detecting the positions of multiple electromagnetic induction pens within a touch surface using a sensor having a configuration in which a plurality of X coils and a plurality of Y coils, each extending in the Y direction, are arranged within the touch surface, the method comprising: repeatedly executing a position detection process to detect the position of each of the plurality of electromagnetic induction pens within the touch surface using the sensor; the position detection process for each electromagnetic induction pen being determined, based on the distance between it and other electromagnetic induction pens indicated by the position detected in the previous position detection process, to be used to emit an alternating magnetic field from among the plurality of X coils and the plurality of Y coils; and detecting the position of the electromagnetic induction pen anew by emitting an alternating magnetic field from the determined alternating magnetic field emitting coil.

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