pen

Abstract

To make it possible to execute calibration of a pen pressure determination threshold as necessary.SOLUTION: A pen includes a pen pressure detection unit that detects a pen pressure level according to a force applied to a pen nib of the pen, the pen being configured to: determine whether a time to acquire pen pressure has come or not; acquire, when the arrival of the timing is determined, a pen pressure level from the pen pressure detection unit; generate a pen-down event on the basis of a result of comparing the pen pressure level with a pen pressure determination threshold; after the pen-down event is generated, execute processing to update the pen pressure determination threshold, when the pen pressure level falls below a first auxiliary threshold which is smaller than the pen pressure determination threshold, the processing being triggered by the generation of the pen-down event.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present invention relates to a method performed by a pen or a pen detection device for detecting said pen. [Background technology]

[0002] Electronic devices that enable pen input by detecting the position of a pen on a panel surface are known. Pen detection in these types of electronic devices is performed based on a pen pressure level, which indicates the level of pen pressure detected by a pen pressure detection sensor built into the pen. Specifically, the pen transmits a position detection burst signal and a data signal containing the detection result of the pen pressure detection sensor to a pen detection device within the electronic device. The pen detection device detects the pen position on the panel surface based on the burst signal, while also acquiring a pen pressure level from the received detection result of the pen pressure detection sensor and performing a threshold determination on the pen pressure level. If the pen pressure level exceeds a predetermined threshold (hereinafter referred to as the "pen pressure determination threshold"), the pen detection device detects that the pen has touched the panel surface and generates a pen-down event. If the pen pressure level falls below the pen pressure determination threshold, the pen detection device detects that the pen has been released from the panel surface and generates a pen-up event. The pen detection device outputs the detected pen position, various data (including the pen pressure level) received via the data signal, and data indicating the occurrence of various events to a host processor within the electronic device each time.

[0003] The host processor is configured to be able to execute a drawing application. This drawing application performs processing to draw a series of positions (pen trajectories) detected between the occurrence of a pen-down event and the occurrence of a pen-up event, with a thickness corresponding to the pen pressure level corresponding to each position. Therefore, if the pen pressure determination threshold is not set to an appropriate value, and a pen-down event does not occur unless further pressure is applied even though the pen is already in contact with the panel surface, or conversely, a pen-up event does not occur even though the pen has already been removed from the panel surface, drawing processing that differs from the contact state will be performed, adversely affecting the user's usability.

[0004] Patent Document 1 discloses an invention for calibrating a writing pressure determination threshold. In this invention, a reference level Vzero of the writing pressure level is derived by statistically processing writing pressure levels that are smaller than the current writing pressure determination threshold and that are fluctuating within a predetermined deviation, and a value Vzero+Voffset obtained by adding a predetermined offset Voffset to this reference level Vzero is used as a new writing pressure determination threshold. This makes it possible to suppress variations in the timing of pen-down events caused by variations in the output level of the writing pressure detection sensor for each pen or over time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2017-0131817 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there are some problems with the writing pressure determination threshold that cannot be solved even by the technology of Patent Document 1. These will be explained in detail below.

[0007] The first issue is ink leakage. Pen pressure sensors have hysteresis (such as structural hysteresis due to different frictional forces occurring under load and unloaded conditions, such as when a core pressed into the housing under load gets caught on the housing when unloaded, or physical hysteresis due to the components used in the pen pressure sensor (e.g., elastic materials used in variable capacitance capacitors). Hereinafter, these types of hysteresis are collectively referred to as "hysteresis"). Even if pressure is applied to the pen tip for a while and then released, the output level does not immediately return to its original level, but rather slowly returns over a certain period of time. Due to this nature of pen pressure sensors, the pen pressure level may remain above the pen pressure threshold even after the pen is lifted, and drawing with a drawing application may continue for a while. In such cases, the user may experience the sensation of ink leakage. Hereinafter, this phenomenon is referred to as "ink leakage."

[0008] The second problem is that even if the pen pressure determination threshold is calibrated using the method described in Patent Document 1, the calibration may not be completed between the time when the pen is up and the time when the pen is down. Calibrating the pen pressure determination threshold using the method described in Patent Document 1 requires obtaining pen pressure level samples over a predetermined period of time while the pen is up. However, if the user operates the pen quickly, a sufficient number of samples may not be obtained between the time when the pen is up and the time when the pen is down. Furthermore, if the pen tip gets caught on the pen housing, the pen pressure level in the pen-up state may fluctuate beyond the predetermined deviation. In such cases, the pen pressure level samples required for calibration may not be obtained. As a result, the calibration may not be completed between the time when the pen is up and the time when the pen is down.

[0009] The third issue is that calibration of the pen pressure determination threshold is not performed in a timely manner. While calibration is usually considered sufficient to be performed once each time the pen is down, the technology of Patent Document 1 may result in calibration being repeatedly performed inside the pen while the pen is up. Such repeated processing may reduce the battery life of the pen.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method implemented by a pen or a pen detection device for detecting said pen, which is able to overcome the above-mentioned problems. [Means for solving the problem]

[0011] A method according to a first aspect of the present invention, which is executed by a pen or a pen detection device for detecting the pen, includes the steps of acquiring a writing pressure level corresponding to the force applied to the tip of the pen, generating a pen-down event or a pen-up event based on the result of comparing the writing pressure level with a writing pressure judgment threshold, acquiring a proximity indicating the positional relationship between the pen and the pen detection device from a proximity detection means provided in either the pen or the pen detection device, and updating the writing pressure judgment threshold based on the writing pressure level when the proximity indicates that the positional relationship between the pen and the pen detection device satisfies a predetermined relationship.

[0012] A method executed by a pen or a pen detection device for detecting the pen according to a second aspect of the present invention includes the steps of acquiring a pen pressure level corresponding to the force applied to the tip of the pen from a pen pressure detection sensor provided on the pen, generating a pen down event based on the result of comparing the pen pressure level with a first threshold, and generating a pen up event based on the result of comparing the pen pressure level with a second threshold different from the first threshold.

[0013] A method executed by a pen or a pen detection device for detecting the pen according to a third aspect of the present invention includes a step of acquiring a writing pressure level corresponding to the force applied to the tip of the pen, a pen down event generating step of generating a pen down event based on the result of comparing the writing pressure level with a writing pressure judgment threshold, and a first update step of updating the writing pressure judgment threshold using the occurrence of the pen down event as a trigger, wherein the pen down event generating step generates the (k+1)th pen down event based on the result of comparing the writing pressure level with the writing pressure judgment threshold after being updated by the first update step, using the occurrence of the kth pen down event as a trigger. [Effects of the Invention]

[0014] According to the first aspect of the present invention, the writing pressure determination threshold can be updated based on a single writing pressure level acquired at an appropriate time (not based on statistics), thereby reducing the possibility that calibration will not be completed between the time of pen-up and the time of the next pen-down. Also, when the proximity acquired from the proximity detection means indicates that the positional relationship between the pen and the pen detection device satisfies a predetermined relationship, the writing pressure determination threshold can be updated immediately, thereby reducing the occurrence of ink leakage.

[0015] According to the second aspect of the present invention, it is possible to appropriately generate pen-down events and pen-up events regardless of the hysteresis of the pen pressure detection sensor, thereby making it possible to quickly resolve the ink leakage phenomenon.

[0016] According to the third aspect of the present invention, the writing pressure determination threshold can be updated only once for each pen-down, making it possible to timely calibrate the writing pressure determination threshold. Also, even when the user operates the pen quickly, and time-consuming calibration such as that described in Patent Document 1 cannot be performed, the writing pressure determination threshold can be updated. [Brief explanation of the drawings]

[0017] [Figure 1] It is a diagram showing the configuration of the position detection system 1 according to the first embodiment of the present invention. [Figure 2] It is a schematic block diagram showing the functional blocks of the pen pressure detection unit 22 and the signal processing unit 24 shown in FIG. 1. [Figure 3] It is a diagram showing the relationship between the relative positional relationship between the pen 2 and the pen detection device 34 and the proximity S. [Figure 4] It is a diagram showing the relationship between the pen pressure level raw_P and the normalized pen pressure level mod_P. [Figure 5] It is a diagram for explaining the pen pressure determination threshold value T. [Figure 6] It is a diagram for explaining the first problem of the present invention. [Figure 7] It is a diagram for explaining the second problem of the present invention. [Figure 8] It is a diagram showing the operation of the event determination / threshold update unit 43 shown in FIG. 2. [Figure 9] It is a flowchart showing the processing flow of the processing performed by the event determination / threshold update unit 43 shown in FIG. 2. [Figure 10] It is a diagram showing the operation of the event determination / threshold update unit 43 according to the second embodiment of the present invention. [Figure 11] It is a diagram schematically showing the change in the pen pressure level raw_P for each case where the value of the peak value PEAK is P1 and P2 (>P1). [Figure 12] It is a diagram schematically showing the change in the pen pressure level raw_P for each case where the time when the pen 2 is in the pen-down state is t2 - t1 and t2 - t0 (t0 < t1). [Figure 13] It is a flowchart showing the processing flow of the processing performed by the event determination / threshold update unit 43 according to the second embodiment of the present invention. [Figure 14] It is a flowchart showing the processing flow of the processing performed by the event determination / threshold update unit 43 according to the second embodiment of the present invention. [Figure 15]FIG. 11 is a diagram illustrating the operation of the event determination and threshold update unit 43 according to the third embodiment of the present invention. [Figure 16] FIG. 11 is a flowchart showing the processing flow of processing performed by an event determination and threshold update unit 43 according to the third embodiment of the present invention. [Figure 17] FIG. 11 is a flowchart showing the processing flow of processing performed by an event determination and threshold update unit 43 according to the third embodiment of the present invention. [Figure 18] FIG. 13 is a flowchart showing the processing flow of processing performed by an event determination and threshold update unit 43 according to a modified example of the third embodiment of the present invention. [Figure 19] FIG. 20 is a flowchart showing details of the calibration process executed in step S51 of FIG. 18. [Figure 20] FIG. 13 is a diagram illustrating the operation of the event determination and threshold update unit 43 according to the modified example of the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] FIG. 1 is a diagram showing 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 is configured to include a pen 2 and an electronic device 3. Of these, the electronic device 3 is, for example, a tablet computer, and is configured to include a display device 30, which is, for example, a liquid crystal display or an organic EL display, a sensor 31 arranged on the rear (or front) of the display device 30, a sensor controller 32 connected to the sensor 31, and a host processor 33 that controls each part of the electronic device 3, including these. Of these, the sensor 31 and the sensor controller 32 constitute a pen detection device 34 for detecting the pen 2. The display surface of the display device 30 is a flat glass surface, and constitutes a panel surface 3t on which the user slides the pen 2.

[0020] The sensor controller 32 and the pen 2 are configured to be able to transmit and receive signals to and from each other via the sensor 31. Hereinafter, a signal transmitted from the pen 2 to the sensor controller 32 will be referred to as a downlink signal DS, and a signal transmitted from the sensor controller 32 to the pen 2 will be referred to as an uplink signal US. The downlink signal DS includes a burst signal for causing the sensor controller 32 to detect the position of the pen 2, and a data signal obtained by modulating various data such as the pen ID assigned to the pen 2, the writing pressure level detected by the writing pressure detection unit 22 described below, and data indicating the on / off state of the switch 23 described below. On the other hand, the uplink signal US includes a command signal indicating an instruction from the sensor controller 32 to the pen 2.

[0021] A user performs pen input to the electronic device 3 by moving the pen 2 with the pen tip in contact with the panel surface 3t. The dashed arrows C1 to C5 in Fig. 1 indicate a typical cycle in which a user operates the pen 2. The sensing range SR shown in Fig. 1 indicates a range in which either the pen 2 or the sensor controller 32 can detect the other by the pen 2 receiving an uplink signal US transmitted by the sensor controller 32 or by the sensor controller 32 receiving a downlink signal DS transmitted by the pen 2.

[0022] When drawing a line on the panel surface 3t using the pen 2, the user moves the pen 2 from outside the sensing range SR into the sensing range SR (pen-down operation, C1 and C2 in FIG. 1 ), moves the pen 2 while the pen tip is in contact with the panel surface 3t (pen-move operation, C3 in FIG. 1 ), and then moves the pen 2 from inside the sensing range SR to outside the sensing range SR (pen-up operation, C4 and C5 in FIG. 1 ). This cycle is repeated. While the pen 2 is within the sensing range SR, the sensor controller 32 receives a downlink signal DS via the sensor 31 to detect the position of the pen 2 on the panel surface 3t and receives various data transmitted by the pen 2. Then, based on the writing pressure level contained in the received data, the sensor controller 32 generates a pen-down event and a pen-up event as appropriate. The sensor controller 32 outputs the detected position, the received data, and data indicating the occurrence of an event to the host processor 33 each time. The host processor 33 renders the line drawing based on the series of positions provided between the pen-down event and the pen-up event. This allows the user to input a desired figure into the electronic device 3.

[0023] As shown in FIG. 1, the pen 2 has a core body 20, an electrode 21, a writing pressure detection unit 22, a switch 23, a signal processing unit 24, and a power source 25.

[0024] The core body 20 is a rod-shaped member arranged so that its longitudinal direction coincides with the pen axis direction of the pen 2, and constitutes the pen tip of the pen 2. A conductive material is applied to the surface of the tip of the core body 20, forming an electrode 21. The rear end of the core body 20 abuts against the writing pressure detection unit 22. The writing pressure detection unit 22 is a sensor (writing pressure detection sensor) that detects the writing pressure level corresponding to the pressure applied to the tip of the core body 20 (writing pressure applied to the core body 20) when the pen tip of the pen 2 is pressed against the panel surface 3t of the sensor controller 32, etc., and is constituted, for example, by a variable capacitance module whose capacitance changes according to the writing pressure.

[0025] The electrode 21 is a conductor provided near the core body 20 and is electrically connected to the signal processing unit 24 by wiring. When the pen 2 transmits a downlink signal DS to the sensor controller 32, the downlink signal DS is supplied from the signal processing unit 24 to the electrode 21, and in response, a charge corresponding to the content of the downlink signal DS is induced in the electrode 21. This causes a change in capacitance in the sensor 31, and the sensor controller 32 receives the downlink signal DS by detecting this change. Furthermore, when an uplink signal US transmitted by the sensor controller 32 arrives at the electrode 21, a charge corresponding to the received uplink signal US is induced in the electrode 21. The signal processing unit 24 receives the uplink signal US by detecting the charge thus induced in the electrode 21.

[0026] The switch 23 is, for example, a side switch provided on the side surface of the housing of the pen 2, and functions as an input unit configured to be able to accept an operation by the user. Specifically, the switch 23 is configured to output switch information indicating its own pressing state to the signal processing unit 24 in accordance with the state of the operation by the user (pressing state). The switch information is information indicating, for example, one of two states, on and off.

[0027] The signal processing unit 24 has a function of receiving and decoding the uplink signal US transmitted by the sensor controller 32 via the electrodes 21, and a function of generating a downlink signal DS in response to a command signal included in the uplink signal US and transmitting it to the sensor controller 32 via the electrodes 21. The pen ID described above is written in an internal memory (not shown) of the signal processing unit 24 during manufacturing.

[0028] The signal processing unit 24 may also have the following functions: a function to generate a pen-down event indicating that the pen 2 has come into contact with the panel surface 3t and a pen-up event indicating that the pen 2 has been released from the panel surface 3t based on the writing pressure level detected by the writing pressure detection unit 22, and each time such an event occurs, to transmit data indicating each event in a downlink signal DS; a function to detect the reception strength of the uplink signal US and, based on the result, to acquire the proximity indicating the positional relationship between the pen 2 and the sensor controller 32; and a function to hold a writing pressure level threshold (writing pressure determination threshold) used to detect the occurrence of a pen-down event and a pen-up event, and to update the threshold as necessary. Details of this point will be described in a third embodiment below.

[0029] The power supply 25 is for supplying operating power (DC voltage) to the signal processing unit 24, and is configured by, for example, a cylindrical AAAA battery.

[0030] The sensor 31 is configured to include a plurality of sensor electrodes (not shown). The sensor controller 32 receives the downlink signal DS via the sensor 31 and detects the position of the pen 2 on the panel surface 3t based on the reception strength of the downlink signal DS at each sensor electrode. The sensor controller 32 also demodulates the downlink signal DS to obtain various data contained in the data signal, and generates a pen-down event indicating that the pen 2 has touched the panel surface 3t and a pen-up event indicating that the pen 2 has been released from the panel surface 3t based on the writing pressure level contained in the data. The sensor controller 32 sequentially supplies the detected position, the obtained various data, and data indicating the occurrence of an event to the host processor 33.

[0031] The host processor 33 is the central processing unit of the electronic device 3, and is capable of running various applications including a drawing application. When running a drawing application, the host processor 33 renders a line drawing by interpolating discrete positions sequentially supplied from the sensor controller 32, and outputs the rendering result to the display device 30. As a result, a figure input by the user using the pen 2 is displayed on the panel surface 3t.

[0032] 2 is a schematic block diagram showing the functional blocks of the writing pressure detection unit 22 and the sensor controller 32. As shown in the figure, the writing pressure detection unit 22 is functionally configured to have a writing pressure signal acquisition unit 40 and a writing pressure level acquisition unit 41, and the sensor controller 32 is functionally configured to have a proximity detection unit 42 (proximity detection means) and an event determination / threshold update unit 43.

[0033] The writing pressure signal acquisition unit 40 converts the pressure F applied to the tip of the core body 20 into an analog writing pressure signal AP. The writing pressure level acquisition unit 41 generates a writing pressure level raw_P, which is a digital value, based on this analog writing pressure signal AP. In a specific example, the writing pressure signal acquisition unit 40 is a time constant circuit, and the writing pressure level acquisition unit 41 is a clock counter. In this case, the analog writing pressure signal AP is a signal indicating a time corresponding to a time constant determined by a capacitance that changes according to the pressure F. Furthermore, the writing pressure level acquisition unit 41 is a circuit that counts clocks supplied from an oscillator (not shown) over a period of time specified by the analog writing pressure signal AP. The writing pressure level raw_P is a signal indicating the result of this counting.

[0034] The writing pressure level raw_P detected by the writing pressure detection unit 22 is transmitted as part of a data signal to the sensor controller 32 by the signal processing unit 24 shown in Fig. 1. Note that an analog writing pressure signal AP may be transmitted from the signal processing unit 24 to the sensor controller 32, and the function of the writing pressure level acquisition unit 41 may be provided within the sensor controller 32.

[0035] The proximity detection unit 42 has a function of detecting the maximum value (maximum reception strength) among the reception strengths of the downlink signal DS at each sensor electrode. The detected maximum reception strength is supplied to the event determination and threshold update unit 43 as proximity S indicating the positional relationship between the pen 2 and the pen detection device 34.

[0036] The event determination and threshold updating unit 43 has a function of comparing the writing pressure level raw_P received from the pen 2 with a pre-stored writing pressure determination threshold, and generating a pen-down event and a pen-up event based on the result of the comparison. The event determination and threshold updating unit 43 is also configured to update the writing pressure determination threshold based on the writing pressure level raw_P when the proximity S supplied from the proximity detection unit 42 indicates that the positional relationship between the pen 2 and the pen detection device 34 satisfies a predetermined relationship.

[0037] FIG. 3 is a diagram showing the relationship between the relative positional relationship between the pen 2 and the pen detection device 34 and the proximity S. In this embodiment, the relative positional relationship between the pen 2 and the sensor controller 32 is classified into three types depending on the value of the proximity S. Specifically, the zones are classified into zone 1 where the proximity S is 0 (i.e., an area where the sensor controller 32 cannot receive the downlink signal DS), zone 2 where the proximity S is greater than 0 and less than a predetermined threshold Sth, and zone 3 where the proximity S is equal to or greater than the threshold Sth. Since the proximity S is the maximum reception strength of the downlink signal DS at the sensor controller 32, these zones 1 to 3 represent the distance from the panel surface 3t. Specifically, zone 3 represents the area closest to the panel surface 3t, zone 1 represents the area farthest from the panel surface 3t, and zone 2 represents the area sandwiched between zone 1 and zone 3.

[0038] The event determination and threshold update unit 43 updates the writing pressure determination threshold when the proximity S indicates that the pen 2 is in zone 2. In this case, it is possible to receive the downlink signal DS, but it is guaranteed that the pen tip of the pen 2 is not in contact with the panel surface 3t. Therefore, the event determination and threshold update unit 43 sets the writing pressure level raw_P when the proximity S indicates that the pen 2 is in zone 2 as the reference value for the writing pressure level (a value indicating the writing pressure level raw_P when no pressure is applied to the pen tip; a system reference value, described later), and updates the writing pressure determination threshold based on this reference value.

[0039] Returning to Figure 2, the event determination and threshold update unit 43 is configured to supply data indicating the occurrence of a pen-down event and a pen-up event, and the writing pressure level received from the pen 2, to the host processor 33 (see Figure 1). However, the event determination and threshold update unit 43 does not supply the writing pressure level raw_P detected by the writing pressure detection unit 22 to the host processor 33 as is, but normalizes it before supplying it to the host processor 33. Hereinafter, the writing pressure level raw_P normalized in this way will be referred to as a normalized writing pressure level mod_P.

[0040] FIG. 4 is a diagram showing the relationship between the writing pressure level raw_P and the normalized writing pressure level mod_P. As shown in the figure, the writing pressure level raw_P is a value between Min and Max, and the normalized writing pressure level mod_P is a value between 0 and mod_Max. If the writing pressure level raw_P is less than the writing pressure determination threshold T, the event determination / threshold update unit 43 fixes the normalized writing pressure level mod_P to 0. On the other hand, if the writing pressure level raw_P is equal to or greater than the writing pressure determination threshold T, the event determination / threshold update unit 43 determines the normalized writing pressure level mod_P according to the following equation (1): mod_P=((mod_Max-1)×raw_P+Max-mod_Max×T) / (Max-T)···(1)

[0041] According to equation (1), when the writing pressure level raw_P is equal to the writing pressure determination threshold T, the normalized writing pressure level mod_P is 1, and when the writing pressure level raw_P is equal to the maximum value Max, the normalized writing pressure level mod_P is equal to the maximum value mod_Max. The minimum value Min, maximum value Max, and writing pressure determination threshold T of the writing pressure level raw_P vary depending on the type and individual differences of the writing pressure detection unit 22. However, it is undesirable for the output writing pressure level to differ depending on the type and individual differences of the writing pressure detection unit 22 or the timing of the pen-down operation, even when the same predetermined force exceeding the writing pressure determination threshold T is applied. By using the normalized writing pressure level mod_P instead of the writing pressure level raw_P, it is possible to reduce the influence of the type and individual differences of the writing pressure detection unit 22 on the rendering result of the host processor 33.

[0042] Here, the writing pressure determination threshold T will be explained in detail. FIG. 5 is a diagram for explaining the writing pressure determination threshold T. In this diagram, the horizontal axis represents the passage of time t, and the vertical axis represents the writing pressure level raw_P. This also applies to the other diagrams shown later.

[0043] The event determination and threshold update unit 43 is configured to have, as internal variables, a system reference value ST and a margin M1 in addition to the writing pressure determination threshold T. The system reference value ST is a value corresponding to the writing pressure level raw_P acquired when no pressure is applied to the pen tip of the pen 2. The margin M1 is a fixed value, and is equal to the difference T-ST between the writing pressure determination threshold T and the system reference value ST. In other words, the writing pressure determination threshold T is always a value that is larger than the system reference value ST by M1, as shown in FIG. 5. Therefore, deriving or updating the writing pressure determination threshold T is equivalent to deriving or updating the system reference value ST.

[0044] Based on its definition, the system reference value ST is expected to be equal to the pen pressure level raw_P when no pressure is applied to the tip of pen 2. At t < t0 in Fig. 5, the state as expected is shown. However, as also shown in the figure, it is normal for a certain ripple to occur in the pen pressure level raw_P, so the system reference value ST becomes a value equal to the average value of the pen pressure level raw_P.

[0045] In the example of Fig. 5, near time t0, a pen-down operation is being performed by the user. As shown in the figure, when the pen-down operation is performed, the pen pressure level raw_P increases accordingly. When the pen pressure level raw_P exceeds the pen pressure determination threshold T, the pen-down event is activated by the event determination and threshold update unit 43. Using this event, the rendering of lines by the drawing application operating on the host processor 33 is started.

[0046] After that, when the pen pressure level raw_P falls below the pen pressure determination threshold T at time t1 due to the user performing a pen-up operation, the pen-up event is activated by the event determination and threshold update unit 43. Thereby, the rendering of lines by the drawing application ends.

[0047] Comparing the pen pressure level raw_P before time t0 and the pen pressure level raw_P after time t1 in FIG. 5, it can be seen that the latter is larger. Since both are in the pen-up state, these values ​​are expected to be the same. However, they are not the same because the pen pressure detection unit 22 has the aforementioned hysteresis. According to the technology of Patent Document 1, in such a case, the system reference value ST can be calibrated. Specifically, the system reference value ST is derived by statistically processing the pen pressure level raw_P (the pen pressure level raw_P within the illustrated period P) that is smaller than the current pen pressure determination threshold T and fluctuates within a predetermined deviation. Furthermore, the pen pressure determination threshold T can be derived by adding a margin M1 to the result. This calibration can also be performed by the sensor controller 32 according to this embodiment.

[0048] However, this calibration alone cannot solve the various problems described above. According to this embodiment, the first and second of the three problems described above are solved. Therefore, the first and second problems will be described in detail below with reference to FIGS. 5 and 6, and then the operation of the event determination and threshold update unit 43 according to this embodiment for solving these problems will be described in detail.

[0049] FIG. 6 is a diagram illustrating the first problem. Due to the hysteresis of the pen pressure detection unit 22, after the user performs a pen-up operation at time t1, the value of the pen pressure level raw_P does not immediately return to its original level. In this case, as shown in FIG. 6, the pen pressure level raw_P may remain above the pen pressure determination threshold T for a while after time t1 (until time t2 in FIG. 6). This causes a time lag between the user performing a pen-up operation and the signal processing unit 24 generating a pen-up event, during which rendering by the host processor 33 continues, giving the user the sensation of ink leakage (the ink leakage phenomenon described above).

[0050] FIG. 7 illustrates the second problem. Performing the calibration requires a certain number of samples of the pen pressure level raw_P, which takes a certain amount of time (e.g., the period P shown in FIG. 5). However, if the user operates the pen quickly, a sufficient number of samples may not be obtained between a pen-up and the next pen-down, as shown in the example shown in FIG. 7. That is, in FIG. 7, the kth pen-down operation is performed at time APD[k], and the kth pen-up operation is performed at time APU[k]. Further, the k+1th pen-down operation is performed at time APD[k+1], and the k+1th pen-up operation is performed at time APU[k+1]. In this case, if the time between time APU[k] and time APD[k+1] is short, calibration cannot be performed within this period.

[0051] FIG. 8 is a diagram illustrating the operation of the event determination and threshold update unit 43 according to this embodiment for solving these problems. To update the system reference value ST (pen pressure determination threshold T), the event determination and threshold update unit 43 refers to the proximity S supplied from the proximity detection unit 42 in addition to the pen pressure level raw_P. Specifically, as shown in FIG. 8, when the proximity S indicates that the pen 2 is in zone 2 shown in FIG. 3, the system reference value ST (pen pressure determination threshold T) is updated based on the pen pressure level raw_P. Note that while FIG. 8 shows an example in which the value of the pen pressure level raw_P is used as the system reference value ST directly, a moving average of the pen pressure level raw_P (the average value of the pen pressure level raw_P over a time shorter than the time required for calibration) may be calculated and used as the system reference value ST.

[0052] By performing such an update, the system reference value ST (pen pressure determination threshold T) can be updated (not based on statistics) based on a single pen pressure level raw_P acquired when the proximity S indicates that it is appropriate to update the system reference value ST (pen pressure determination threshold T), thereby reducing the possibility that calibration will not be completed between pen-up and the next pen-down. Also, when the proximity S acquired from the proximity detection unit 42 indicates that the positional relationship between the pen 2 and the pen detection device 34 satisfies a predetermined relationship (specifically, that the pen 2 is not in contact with the panel surface 3t), the system reference value ST (pen pressure determination threshold T) can be updated immediately, thereby reducing the occurrence of ink leakage.

[0053] 9 is a flowchart showing the processing flow of the processing performed by the event determination and threshold update unit 43. Hereinafter, the operation of the event determination and threshold update unit 43 according to this embodiment will be described in more detail with reference to FIG.

[0054] As shown in FIG. 9, the event determination and threshold updating unit 43 first initializes the writing pressure determination threshold T (system reference value ST) (step S1) and sets the current state to pen-up (step S2).

[0055] Next, the event determination and threshold update unit 43 determines whether or not a downlink signal DS has been received (step S3). If it is determined in step S3 that a downlink signal DS has not been received, the event determination and threshold update unit 43 returns to step S3 and repeats the determination process. On the other hand, if it is determined in step S3 that a downlink signal DS has been received, the event determination and threshold update unit 43 acquires the proximity S from the proximity detection unit 42 (step S4) and decodes the data signal to acquire the writing pressure level raw_P (step S5). Then, the writing pressure level raw_P is converted into a normalized writing pressure level mod_P (see FIG. 4) based on the writing pressure determination threshold T, and output to the host processor 33 (step S6).

[0056] Next, the event determination and threshold update unit 43 determines whether the pen 2 that transmitted the downlink signal DS is in one of zones 1 to 3 shown in FIG. 3, based on the obtained proximity S (step S7). As a result, if it is determined that the pen 2 is in zone 2 (that is, if it is possible to receive the downlink signal DS but it is guaranteed that the pen 2 is not in contact with the panel surface 3t), the event determination and threshold update unit 43 updates the writing pressure determination threshold T (system reference value ST) based on the writing pressure level raw_P obtained in step S5 (step S8). Specifically, the system reference value ST is updated by the writing pressure level raw_P obtained in step S5, and a margin M1 is added to the updated system reference value ST to calculate the writing pressure determination threshold T.

[0057] Next, the event determination and threshold update unit 43 compares the writing pressure level raw_P acquired in step S5 with the writing pressure determination threshold T (step S9). If the result shows that the writing pressure level raw_P is greater than the writing pressure determination threshold T, the event determination and threshold update unit 43 first determines whether the current state is pen-up or pen-down (step S10). If the result shows that the current state is pen-up, the event determination and threshold update unit 43 generates a pen-down event and sets the current state to pen-down (step S11). This setting process includes a process of outputting data indicating that a pen-down event has occurred to the host processor 33. After completing the process of step S11, the event determination and threshold update unit 43 returns to step S3 and waits for the next timing. On the other hand, if the event determination and threshold update unit 43 determines that the current state is pen-down in step S10, the event determination and threshold update unit 43 skips the process of step S11 and returns to step S3.

[0058] When the comparison in step S8 indicates that the writing pressure level raw_P is equal to or lower than the writing pressure determination threshold T, the event determination and threshold update unit 43 first determines whether the current state is pen-up or pen-down (step S12). If it determines that the current state is pen-down, it generates a pen-up event and sets the current state to pen-up (step S13). This setting process includes a process of outputting data indicating that a pen-up event has occurred to the host processor 33. After completing the process in step S13, the event determination and threshold update unit 43 returns to step S3 and waits for the next timing. On the other hand, if it determines that the current state is pen-up in step S12, the event determination and threshold update unit 43 skips the process in step S13 and returns to step S3.

[0059] As described above, according to the first embodiment of the present invention, the writing pressure determination threshold T can be updated (without relying on statistics) based on a single writing pressure level raw_P acquired at an appropriate time (specifically, when the pen 2 is in zone 2), thereby reducing the possibility that calibration will not be completed between a pen-up and the next pen-down. Furthermore, when the proximity S acquired from the proximity detection unit 42 indicates that the positional relationship between the pen 2 and the pen detection device 34 satisfies a predetermined relationship (specifically, when the pen 2 is in zone 2), the writing pressure determination threshold T can be updated immediately, thereby reducing the occurrence of ink leakage.

[0060] In this embodiment, an example has been described in which the proximity detection unit 42 is provided within the sensor controller 32, but a proximity detection unit may also be provided within the signal processing unit 24 of the pen 2. In this case, it is preferable to use the reception strength of the uplink signal US received via the electrode 21 shown in Fig. 1 as the proximity S. Specifically, for example, in an electromagnetic induction type pen 2, it is preferable to use the magnitude of the current generated by the tablet's alternating magnetic field as the proximity S, and for example, in an active electrostatic type pen 2, it is preferable to use the amount of charge induced in the electrode 21 as the proximity S.

[0061] In other words, the proximity detection unit may generate the proximity S based on the reception strength at the receiving end of the signal transmitted and received between the pen 2 and the pen detection device 34. However, the proximity detection unit may also generate the proximity S based on information other than the reception strength at the receiving end of the signal transmitted and received between the pen 2 and the pen detection device 34. For example, the proximity detection unit may generate the proximity S based on the detection result of the capacitance generated between the electrode 21 and the sensor electrode constituting the sensor 31, or the pressed state of the switch 23. Furthermore, the proximity detection unit may generate the proximity S based on an image of the panel surface 3t captured by an image sensor provided in the pen 2, or may generate the proximity S based on the result of echolocation performed by a sonar provided in the pen. Furthermore, the proximity detection unit may generate the proximity S based on two or more of these pieces of information.

[0062] Furthermore, the function of the event determination and threshold update unit 43 may be provided in the pen 2 instead of the sensor controller 32. In this case, it is preferable that the signal processing unit 24 of the pen 2 transmits data indicating the occurrence of a pen-down event and a pen-up event to the sensor controller 32 by a downlink signal DS.

[0063] In addition, the sensor controller 32 can be configured to be able to detect multiple pens 2 each assigned a different pen ID. In this case, since different pen IDs are received from each of the multiple pens 2, the event determination / threshold update unit 43 may be configured to hold the writing pressure determination threshold T and system reference value ST for each received pen ID and to update these based on the corresponding writing pressure level raw_P.

[0064] Next, a position detection system 1 according to a second embodiment of the present invention will be described. The basic configuration of the position detection system 1 according to this embodiment is the same as that shown in FIGS. 1 and 2. However, the proximity detection unit 42 does not necessarily have to be provided. This embodiment differs from the first embodiment in that the event determination and threshold update unit 43 uses two types of writing pressure determination thresholds. The operation of the event determination and threshold update unit 43 according to this embodiment will be described in detail below.

[0065] 10 is a diagram showing the operation of the event determination and threshold update unit 43 according to this embodiment. In addition to the writing pressure determination threshold T (first threshold) described in the first embodiment, the event determination and threshold update unit 43 according to this embodiment uses an auxiliary threshold TU1 (second threshold) that is different from the writing pressure determination threshold T. After a pen-down event is generated as described in the first embodiment, the event determination and threshold update unit 43 is configured to calculate the auxiliary threshold TU1 so that it is a value greater than the writing pressure determination threshold T.

[0066] The following formula (2) is an example of a specific formula for calculating the auxiliary threshold value TU1. Here, f(PEAK) is a function of the peak value PEAK of the writing pressure level raw_P (the maximum value of the writing pressure level raw_P detected while the pen 2 is in a pen-down state), and is configured to increase as the peak value PEAK increases. After generating a pen-down event, the event determination / threshold update unit 43 periodically acquires the writing pressure level raw_P and acquires the maximum value of the writing pressure level raw_P after the pen-down event occurs. Then, the event determination / threshold update unit 43 is configured to calculate the auxiliary threshold value TU1 by substituting the acquired maximum value as the peak value PEAK into formula (2). TU1=T+f(PEAK) (2)

[0067] The auxiliary threshold value TU1 calculated as described above increases as the writing pressure level raw_P continues to increase, and becomes a fixed value once the writing pressure level raw_P reaches its maximum, as shown in Fig. 10. The event determination and threshold value update unit 43 uses the calculated auxiliary threshold value TU1 to detect a pen-up operation. That is, the event determination and threshold value update unit 43 is configured to generate a pen-up event based on the result of comparing the writing pressure level raw_P with the auxiliary threshold value TU1.

[0068] Here, the meaning of equation (2) will be explained in detail. Fig. 11 is a diagram showing a schematic diagram of changes in the pen pressure level raw_P when the peak value PEAK is P1 and when it is P2 (>P1). In the figure, the curve C1 shows the case when the peak value PEAK is P1, and the curve C2 shows the case when the peak value PEAK is P2. For both curves C1 and C2, it is assumed that a pen-down operation occurs at time t0 and a pen-up operation occurs at time t1.

[0069] As can be seen from FIG. 11, the pen pressure level raw_P after the user performs a pen-up operation drops sharply and then slowly approaches zero. The minimum values ​​at which this sharp drop occurs differ between curves C1 and C2. That is, the minimum value V2 of curve C2, which has a relatively large peak value PEAK, is greater than the minimum value V1 of curve C1, which has a relatively small peak value PEAK. The time required for the pen pressure level raw_P to return to zero also differs between curves C1 and C2. That is, the return time t3-t1 of curve C2, which has a relatively large peak value PEAK, is greater than the return time t2-t1 of curve C1, which has a relatively small peak value PEAK. Therefore, to avoid false detection of a pen-up operation and generate a pen-up event promptly after a pen-up operation, the larger the peak value PEAK, the greater the auxiliary threshold value TU1 used to detect the pen-up operation. Equation (2) formulates this.

[0070] Therefore, according to this embodiment, it can be said that it is possible to appropriately generate pen-down events and pen-up events regardless of the hysteresis of the pen pressure detection unit 22. As shown in FIG. 10, compared with the case of generating a pen-up event based on the pen pressure determination threshold value T, it is possible to eliminate the ink leakage phenomenon at an earlier stage.

[0071] Note that instead of the peak value PEAK of the pen pressure level raw_P, the auxiliary threshold value TU1 may be calculated based on the length of time during which the pen 2 is in the pen-down state. This will be described in detail below.

[0072] FIG. 12 is a diagram schematically showing changes in the pen pressure level raw_P for the cases where the time during which the pen 2 is in the pen-down state is t2 - t1 and t2 - t0 (t0 < t1), respectively. In the figure, the case where the time during which the pen is in the pen-down state is t2 - t1 is indicated by curve C3, and the case where the time during which the pen is in the pen-down state is t2 - t0 is indicated by curve C4. The occurrence time of the pen-up operation is set to time t2 for both curves C3 and C4.

[0073] The pen pressure level raw_P after the user performs a pen-up operation also changes in such a way that it once drops rapidly and then gradually approaches zero in this case. The minimum values when dropping rapidly are different between curve C3 and curve C4. That is, the minimum value V4 of curve C4 with a relatively long pen-down time is larger than the minimum value V3 of curve C3 with a relatively short pen-down time. Also, the time required for the pen pressure level raw_P to return to zero is different between curve C3 and curve C4. That is, the return time t4 - t2 of curve C4 with a relatively long pen-down time is larger than the return time t3 - t2 of curve C3 with a relatively short pen-down time. Therefore, it is understood that in order to avoid misdetection of the pen-up operation and generate a pen-up event promptly after the pen-up operation, it is also possible to increase the auxiliary threshold value TU1 used to detect the pen-up operation as the length of the time during which the pen is in the pen-down state becomes larger.

[0074] The following equation (3) shows a calculation formula for the auxiliary threshold value TU1 that can be used in this case: where f(L) is a function of the duration L of the pen-down state, and is configured to increase as the duration L increases. TU1=T+f(L) (3)

[0075] Furthermore, in the second embodiment, if the auxiliary threshold value TU1 were simply used, there is a possibility that a pen-down event would occur immediately after a pen-up event. This is because the writing pressure level raw_P immediately after falling below the auxiliary threshold value TU1 is usually a value greater than the writing pressure determination threshold value T. Therefore, it is preferable that the event determination / threshold value update unit 43 according to this embodiment further performs processing to set the writing pressure determination threshold value T to a value greater than the auxiliary threshold value TU1 in response to the occurrence of a pen-up event. This point will be explained in detail below, again with reference to FIG. 10.

[0076] As shown in FIG. 10 , at time t3 when a pen-up event occurs, the event determination and threshold update unit 43 performs a process of updating the system reference value ST using the pen pressure level raw_P at that time. Accordingly, the pen pressure determination threshold T is also updated. Thereafter, when the pen pressure level raw_P falls below the system reference value ST, the event determination and threshold update unit 43 updates the system reference value ST and the pen pressure determination threshold T using the pen pressure level raw_P at that time. This makes it possible to avoid a pen-down event from occurring unless the pen pressure level raw_P significantly rebounds. When the pen pressure level raw_P significantly rebounds, the pen pressure level raw_P exceeds the pen pressure determination threshold T, as shown at time t4 in FIG. 10 , and a pen-down event occurs.

[0077] 13 and 14 are flow charts showing the processing flow of the processing performed by the event determination and threshold update unit 43. Hereinafter, the operation of the event determination and threshold update unit 43 according to this embodiment will be described in more detail with reference to these figures.

[0078] The processing of steps S1 to S6 is the same as that of the first embodiment. However, step S4 may be skipped (not shown in FIGS. 13 and 14). After step S6, the event determination and threshold update unit 43 determines whether the current state is pen-up or pen-down (step S20). As a result, if it is determined to be pen-up, the event determination and threshold update unit 43 next compares the writing pressure level raw_P acquired in step S5 with the system reference value ST (step S21). Then, if the writing pressure level raw_P is less than the system reference value ST, the system reference value ST is updated based on the writing pressure level raw_P. Specifically, the system reference value ST is updated based on the writing pressure level raw_P acquired in step S5. At this time, the writing pressure determination threshold T is also updated in accordance with the update of the system reference value ST. After updating the system reference value ST and the writing pressure determination threshold T, the event determination and threshold update unit 43 returns to the processing of step S3.

[0079] On the other hand, if the event determination and threshold update unit 43 determines in step S22 that the writing pressure level raw_P is equal to or greater than the system reference value ST, it then compares the writing pressure level raw_P with the writing pressure determination threshold T (step S23). If the result indicates that the writing pressure level raw_P is greater than the writing pressure determination threshold T, it generates a pen-down event and sets the current state to pen-down (step S24). Details of this process are the same as those of step S11 shown in FIG. 9. Next, the event determination and threshold update unit 43 sets the peak value PEAK, which is an internal variable, to 0 (step S25), and returns the process to step S3.

[0080] If it is determined in step S20 that a pen-down has occurred, the event determination and threshold update unit 43 compares the writing pressure level raw_P acquired in step S5 with the peak value PEAK (step S26), as shown in Fig. 14. If the writing pressure level raw_P is greater than the peak value PEAK, the event determination and threshold update unit 43 sets the writing pressure level raw_P to the peak value PEAK (step S27) and calculates an auxiliary threshold TU1 based on the writing pressure determination threshold T and the peak value PEAK (step S28). The event determination and threshold update unit 43 performs this calculation using, for example, the above-mentioned equation (2).

[0081] After step S28 is completed, or if step S26 determines that the writing pressure level raw_P is not greater than the peak value PEAK, the event determination and threshold update unit 43 compares the writing pressure level raw_P with the auxiliary threshold TU1 (step S29). If the result indicates that the writing pressure level raw_P is equal to or less than the auxiliary threshold TU1, a pen-up event is generated and the current state is set to pen-up (step S30). Details of this process are the same as those of step S13 shown in FIG. 9. Next, the event determination and threshold update unit 43 updates the system reference value ST and the writing pressure determination threshold T based on the auxiliary threshold TU1 (step S31), and then returns to step S3. In a specific example, step S31 is a process of setting the writing pressure determination threshold T to a value greater than the auxiliary threshold TU1, but it may also be a process of setting the system reference value ST to a value greater than the auxiliary threshold TU1.

[0082] As described above, according to the second embodiment of the present invention, it is possible to appropriately generate pen-down events and pen-up events regardless of the hysteresis of the pen pressure detection unit 22, thereby making it possible to quickly resolve the ink leakage phenomenon.

[0083] Next, the position detection system 1 according to the third embodiment of the present invention will be described. The basic configuration of the position detection system 1 according to the present embodiment is the same as that shown in FIGS. 1 and 2, except that the proximity detection unit 42 and the event determination / threshold update unit 43 are provided in the signal processing unit 24 of the pen 2. However, the proximity detection unit 42 may not be provided. In addition to the above points, the present embodiment is different from the first embodiment in that the event determination / threshold update unit 43 updates the pen pressure determination threshold using the occurrence of the pen-down event as a trigger. Hereinafter, the operation of the event determination / threshold update unit 43 according to the present embodiment will be described in detail.

[0084] FIG. 15 is a diagram showing the operation of the event determination / threshold update unit 43 according to the present embodiment. The event determination / threshold update unit 43 according to the present embodiment uses an auxiliary threshold TU2 (first auxiliary threshold) having a value smaller than the pen pressure determination threshold T (first threshold) described in the first embodiment. Specifically, as shown in FIG. 15, a value obtained by adding a margin M2 (<M1) to the system reference value ST is used as the auxiliary threshold TU2.

[0085] The event determination / threshold update unit 43 generates a pen-down event by the same process as the event determination / threshold update unit 43 according to the first embodiment, and updates the pen pressure determination threshold T using the occurrence of this pen-down event as a trigger. Specifically, after the pen-down event occurs, when the pen pressure level raw_P falls below the auxiliary threshold TU2, the pen pressure determination threshold T is configured to be updated. Further, the event determination / threshold update unit 43 generates the (k + 1)-th pen-down event based on the comparison result between the pen pressure level raw_P and the pen pressure determination threshold T updated using the occurrence of the k-th pen-down event as a trigger.

[0086] By performing such an operation by the event determination / threshold update unit 43, it becomes possible to update the writing pressure determination threshold T only once per pen-down operation, as shown in FIG. 15 . Among the above-mentioned hysteresis, mechanical hysteresis in particular can be said to be a change in the force response characteristics in the loading and unloading associated with the next cycle due to the loading and unloading associated with the previous cycle of pen-down operation and pen-up operation. Therefore, since it is desirable to perform calibration for each cycle in which this loading and unloading occurs, this embodiment can be said to make it possible to perform calibration of the writing pressure determination threshold T in a timely manner. Furthermore, it becomes possible to update the writing pressure determination threshold T even when time-consuming calibration such as that described in Patent Document 1 cannot be performed, such as when the user operates the pen 2 quickly.

[0087] 16 and 17 are flow charts showing the processing flow of the processing performed by the event determination and threshold update unit 43 according to this embodiment. The operation of the event determination and threshold update unit 43 according to this embodiment will be described in more detail below with reference to these figures.

[0088] The event determination and threshold update unit 43 according to this embodiment first initializes the writing pressure determination threshold T (system reference value ST, auxiliary threshold TU2) (step S1a). As described above, the auxiliary threshold TU2 is always a value that is M2 larger than the system reference value ST, and therefore, as in the case of the writing pressure determination threshold T, deriving or updating the auxiliary threshold TU2 is equivalent to deriving or updating the system reference value ST.

[0089] Among the subsequent processes, steps S2 to S13 are executed in the same manner as in the first embodiment. However, steps S4, S7, and S8 (see FIG. 9) related to the proximity S may be skipped (not shown in FIGS. 16 and 17). Steps S3 and S5 may be replaced with steps S3a and S5a, respectively. Step S3a is a process for determining whether or not a timing has arrived to acquire the writing pressure level raw_P from the writing pressure detection unit 22. This timing may occur periodically, or may occur upon receipt of an uplink signal US from the sensor controller 32. In the latter case, the subsequent processes are performed only when the pen 2 is near the sensor controller 32, thereby delaying the consumption of the power supply 25. Step S5a differs from step S5 in that the writing pressure level raw_P is acquired by receiving an input from the writing pressure detection unit 22, rather than by decoding a data signal.

[0090] The event determination and threshold update unit 43 also sets a pen-down occurrence flag 1, which temporarily stores the occurrence of a pen-down, to false between steps S2 and S3 (step S40). After generating a pen-down event in step S11, the event determination and threshold update unit 43 sets the pen-down occurrence flag 1 to true (step S41).

[0091] If the event determination / threshold update unit 43 according to this embodiment determines in step S9 that the writing pressure level raw_P is equal to or less than the writing pressure determination threshold T, it further determines whether the writing pressure level raw_P is equal to or less than the auxiliary threshold TU2 (step S42), as shown in Fig. 17. Note that steps S12 and S13 also shown in Fig. 9 may be executed after determining in step S9 that the writing pressure level raw_P is equal to or less than the writing pressure determination threshold T, as shown in Fig. 17, and before executing step S42.

[0092] If it is determined in step S42 that the writing pressure level raw_P is not equal to or less than the auxiliary threshold value TU2, the event determination and threshold value update unit 43 returns the process to step S3. On the other hand, if it is determined in step S42 that the writing pressure level raw_P is equal to or less than the auxiliary threshold value TU2, the event determination and threshold value update unit 43 first determines whether the pen-down occurrence flag 1 is true. If it is determined to be false, the process returns to step S3. On the other hand, if it is determined to be true, the event determination and threshold value update unit 43 performs an update process of the writing pressure determination threshold value T (system reference value ST, auxiliary threshold value TU2) based on the writing pressure level raw_P (step S44, first update step). Specifically, as shown in FIG. 15, the system reference value ST is updated by the writing pressure level raw_P acquired in step S5. In addition, the writing pressure determination threshold value T and the auxiliary threshold value TU2 are calculated by adding margins M1 and M2 to the updated system reference value ST. Thereafter, the event determination and threshold update unit 43 sets the pen-down occurrence flag 1 to false (step S45), and returns the process to step S3.

[0093] As described above, according to the third embodiment of the present invention, it is possible to update the writing pressure determination threshold T only once for each pen-down. This makes it possible to timely perform calibration of the writing pressure determination threshold T. Furthermore, it is possible to update the writing pressure determination threshold T even when time-consuming calibration such as that described in Patent Document 1 cannot be performed, such as when the user operates the pen 2 quickly.

[0094] In this embodiment, the occurrence of a pen-down event is used as a trigger to update the writing pressure determination threshold T (system reference value ST, auxiliary threshold TU2) using the latest writing pressure level raw_P, but the occurrence of a pen-down event may also be used as a trigger to execute a calibration process such as that disclosed in Patent Document 1. Furthermore, these processes may also be executed in combination. Below, a modified example of this embodiment relating to such a combination will be described in detail with reference to the drawings.

[0095] Fig. 18 is a flow diagram showing the processing flow of the processing performed by the event determination and threshold update unit 43 according to this modified example. As can be seen by comparing Fig. 18 with Fig. 16, the processing performed by the event determination and threshold update unit 43 according to this modified example differs from the processing performed by the event determination and threshold update unit 43 according to this embodiment in that steps S1a, S40, and S41 become steps S1b, S40a, and S41a, respectively, and in that steps S50 and S51 are added between steps S6 and S9. The following description will focus on these differences.

[0096] In step S1b, the event determination and threshold update unit 43 according to this modification initializes the writing pressure determination threshold T (system reference value ST, auxiliary threshold TU2), as well as auxiliary thresholds Tshort and Tfluc (second and third auxiliary thresholds), and the number of references Tcount. Regarding the auxiliary threshold Tshort, the event determination and threshold update unit 43 uses a value obtained by adding a predetermined margin to the system reference value ST, which is greater than the auxiliary threshold TU2 and smaller than the writing pressure determination threshold T. Therefore, as with the writing pressure determination threshold T and the auxiliary threshold TU2, deriving or updating the auxiliary threshold Tshort is equivalent to deriving or updating the system reference value ST. Predetermined values ​​are set for the auxiliary threshold Tfluc and the number of references Tcount.

[0097] Furthermore, the event determination and threshold update unit 43 according to this modification uses two flags for temporarily storing the occurrence of a pen-down. Specifically, in step S40a, pen-down occurrence flags 1 and 2 are each set to False. After a pen-down event is generated in step S11, pen-down occurrence flags 1 and 2 are each set to True (step S41a). Note that pen-down occurrence flag 1 is the same as that described with reference to FIGS. 16 and 17.

[0098] After executing step S6, the event determination and threshold update unit 43 according to this modification determines whether the pen-down occurrence flag 2 is true (step S50). If it is determined to be false, the process proceeds to step S9. On the other hand, if it is determined to be true, the process executes a calibration process for the writing pressure determination threshold T (step S51).

[0099] 19 is a flow diagram showing details of the calibration process executed in step S51. As shown in the figure, the event determination / threshold update unit 43 first stores the pen pressure level raw_P newly acquired in step S5 in a memory (not shown) (step S60). This process is executed so that at least the pen pressure levels raw_P corresponding to the number of references Tcount are accumulated in the memory.

[0100] Next, the event determination and threshold update unit 43 determines whether the past pen pressure levels raw_P for the number of references Tcount stored in memory are all below the auxiliary threshold Tshort and whether the maximum fluctuation range is below the auxiliary threshold Tfluc (steps S61, S62).

[0101] If the event determination and threshold update unit 43 obtains a negative result in step S62, it terminates the calibration process and proceeds to step S9 in FIG. 18. On the other hand, if the event determination and threshold update unit 43 obtains a positive result in step S62, it updates the writing pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) based on the past writing pressure levels raw_P for the number of references Tcount stored in memory (step S63, second update step). Specifically, it updates the system reference value ST using the average value of the past writing pressure levels raw_P for the number of references Tcount stored in memory. In addition, it calculates the writing pressure determination threshold T and the auxiliary thresholds TU2, Tshort by adding a predetermined margin to the updated system reference value ST. Thereafter, the event determination and threshold update unit 43 sets the pen-down occurrence flag 2 to false (step S64), terminates the calibration process, and proceeds to step S9 in FIG. 18.

[0102] 20 is a diagram showing the operation of the event determination and threshold update unit 43 according to this modified example. In this example, when the kth pen-down event occurs at time t0, and thereafter the writing pressure level raw_P falls below the auxiliary threshold TU2 at time t2, the writing pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) is updated using the latest writing pressure level raw_P at that time. Furthermore, at time t3, when all of the past writing pressure levels raw_P for the number of references Tcount are equal to or less than the auxiliary threshold Tshort and the maximum fluctuation range is equal to or less than the auxiliary threshold Tfluc, the writing pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) is updated by the calibration process shown in FIG. 19.

[0103] Furthermore, when the (k+1)th pen-down event occurs at time t2, thereafter, at time t5 when all of the past pen pressure levels raw_P for the number of references Tcount are equal to or less than the auxiliary threshold Tshort and the maximum fluctuation range is equal to or less than the auxiliary threshold Tfluc, the pen pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) is updated by the calibration process shown in Fig. 19. In this case, because the pen pressure level raw_P is not below the auxiliary threshold TU2, the pen pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) is not updated by the latest pen pressure level raw_P.

[0104] Furthermore, when the (k+2)th pen-down event occurs at time t6, the writing pressure level raw_P falls below the auxiliary threshold TU2 at time t8, and the writing pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) is updated using the most recent writing pressure level raw_P at that time. Also, at time t9, when all of the past writing pressure levels raw_P referenced the number of times Tcount are equal to or less than the auxiliary threshold Tshort and the maximum fluctuation range is equal to or less than the auxiliary threshold Tfluc, the writing pressure determination threshold T (system reference value ST, auxiliary thresholds TU2, Tshort) is updated using the calibration process shown in FIG.

[0105] Thus, according to this modification, even when the writing pressure level raw_P does not fall below the auxiliary threshold value TU2 and therefore the writing pressure determination threshold value T (system reference value ST, auxiliary threshold value TU2, Tshort) is not updated using the latest writing pressure level raw_P, the writing pressure determination threshold value T (system reference value ST, auxiliary threshold value TU2, Tshort) can be updated by the calibration process shown in Fig. 19. This makes it possible to more appropriately calibrate the writing pressure determination threshold value T.

[0106] 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. [Explanation of symbols]

[0107] 1. Position detection system 2 pens 3 Electronic equipment 3t panel surface 20 core body 21 electrodes 22 Pen pressure detection unit 23 Switch 24 Signal Processing Section 25 Power supply 30 Display device 31 Sensors 32 Sensor Controller 33 Host Processor 34 Pen detection device 40 Pen pressure signal acquisition unit 41 Pen pressure level acquisition unit 42 Proximity detection unit 43 Event judgment and threshold update unit AP Analog pen pressure signal DS downlink signal M1,M2 margin PEAK Peak value ST System Reference Values T Pen pressure threshold TU1, TU2, Tshort, Tfluc auxiliary thresholds Tcount Reference count US uplink signal mod_P normalized pressure level raw_P pressure level

Claims

1. A pen including a writing pressure detection unit that detects a writing pressure level according to a force applied to a pen tip, Determine whether or not a timing for acquiring pen pressure has arrived, which occurs periodically or upon receiving an uplink signal transmitted by the sensor controller; Each time it is determined that the timing has arrived, the writing pressure level is acquired from the writing pressure detection unit; generating a pen-down event based on the newly acquired writing pressure level exceeding a writing pressure determination threshold when the timing arrives; After the pen-down event occurs, if the writing pressure level newly acquired in response to the arrival of the timing is below a first auxiliary threshold that is smaller than the writing pressure determination threshold, a process of updating the writing pressure determination threshold is executed using the occurrence of the pen-down event as a trigger. pen.

2. When a predetermined number of past writing pressure levels are all equal to or less than the second auxiliary threshold and the maximum fluctuation range is equal to or less than the third auxiliary threshold, a process of updating the writing pressure determination threshold is executed using the occurrence of the pen-down event as a trigger.

10. The pen of claim 1.

3. The second auxiliary threshold is greater than the first auxiliary threshold.

3. The pen of claim 2.

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