WO2014180444A1

WO2014180444A1 - Sensitivity adjustment method and device

Info

Publication number: WO2014180444A1
Application number: PCT/CN2014/079883
Authority: WO
Inventors: 郝志坚; 童向杰
Original assignee: 中兴通讯股份有限公司
Priority date: 2013-12-11
Filing date: 2014-06-13
Publication date: 2014-11-13
Also published as: CN104714703A

Abstract

Disclosed is a sensitivity adjustment method and device, wherein said method comprises: obtaining the signal strength of a signal produced by a touch object coming into contact with a touch screen; adjusting, in accordance with said signal strength, the sensitivity of the touch screen. The present invention solves the problem whereby, because the sensitivity of a touch screen is fixed, said sensitivity cannot generate different signal strengths in accordance with different touch objects to thereby engage in flexible adjustment, thus causing inconvenience to a user when operating a touch screen terminal; the present invention achieves the goal of flexibly adjusting touch screen terminal sensitivity, thus improving user experience.

Description

TECHNICAL FIELD The present invention relates to the field of touch technologies, and in particular, to a sensitivity adjustment method and apparatus. BACKGROUND OF THE INVENTION A touch screen is a transparent medium attached to the surface of a display, and is increasingly favored by consumers, and is increasingly applied to various mobile terminal devices. With the development of touch technology, the capacitive touch screen not only supports bare finger touch, but also supports gloved finger touch, stylus touch and the like. Since the signal strength generated by bare fingers, gloved fingers, and the stylus when touching the touch screen (the amount of capacitance change of the touch screen caused by the touch is different), their requirements for touch screen sensitivity are different. However, the sensitivity of the touch screen set at the factory is generally fixed. Even if the user can select the touch screen sensitivity in advance, the system will fix this sensitivity before the next selection. Touch objects with different signal intensities are not well supported at a fixed sensitivity. If the touch screen sensitivity is suitable for a gloved finger or stylus, the sensitivity is high for bare fingers, which may result in a report point when the finger has not touched the touch screen, or a touch operation may be recognized. For many touch screen actions, many misoperations occur; if the touch screen sensitivity is suitable for bare fingers, the sensitivity is low for gloved fingers or stylus, when touching with a gloved finger or stylus When the screen is touched, the touch screen may not recognize the touch action or be slow, which causes great trouble to the user. In view of the related art, the sensitivity of the touch screen is generally fixed, and it is not possible to flexibly adjust the signal intensity with different touch objects. Currently, no reasonable solution has been proposed. SUMMARY OF THE INVENTION Embodiments of the present invention provide a method and a device for adjusting sensitivity, so as to at least solve the related problem in the related art, because the sensitivity of the touch screen is fixed, the sensitivity cannot be flexibly adjusted according to different signal strengths generated by different touch objects, and the user is operated. The problem of inconvenience caused by touching the screen terminal. According to an aspect of an embodiment of the present invention, a method for sensitivity adjustment is provided, comprising: acquiring a signal strength of a signal generated by a touch object contacting a touch screen; and adjusting a sensitivity of the touch screen according to the signal strength. Optionally, acquiring the signal strength of the signal generated by the touch object contacting the touch screen comprises: acquiring an average intensity value of a signal generated by the touch object contacting the touch screen within a predetermined duration as the signal strength. Optionally, adjusting the sensitivity of the touch screen according to the signal strength comprises: comparing the signal strength with a current threshold value, wherein the threshold value is set to identify a sensitivity of the touch screen; As a result, the threshold value is adjusted. Optionally, adjusting the threshold according to the result of the comparison includes at least one of the following: in a case where the signal strength is higher than the threshold and the difference between the signal strength and the threshold is higher than N, And increasing the threshold value to reduce the sensitivity of the touch screen; or when the signal strength is lower than the threshold value, or when the signal strength is higher than the threshold value and the signal strength is If the difference between the threshold values is lower than L, the threshold value is lowered to increase the sensitivity of the touch screen; wherein, the L is smaller than the N; the signal strength is higher than the threshold value and the signal is In the case where the difference between the intensity and the threshold value is greater than L and less than N, the threshold value is maintained unchanged. Optionally, adjusting the threshold value includes at least one of: increasing a threshold value of PM in a case where a difference P between the signal strength and the threshold value is higher than the N, wherein a value between the L and the N; if the difference P between the signal strength and the threshold is lower than the L, determining whether the threshold is lower than the first after the MP is lowered a threshold value, if the value is higher, the threshold value is lowered by MP, and if not higher, the threshold value is lowered to a first threshold value, wherein the first threshold value is the lowest allowed value; In the case that the signal strength is lower than the threshold value, it is determined whether the threshold value is lowered by M+P or higher than the first threshold value, and if it is higher, the threshold value is lowered by M+P, if If not higher, the threshold value is lowered to the first threshold value. According to another aspect of the embodiments of the present invention, there is provided an apparatus for adjusting sensitivity, comprising: an acquiring module configured to acquire a signal strength of a signal generated by a touch object contacting a touch screen; and an adjustment module configured to be according to the signal The intensity adjusts the sensitivity of the touch screen. Optionally, the acquiring module is further configured to acquire, as the signal strength, an average intensity value of a signal generated by the touch object contacting the touch screen within a predetermined duration. Optionally, the adjusting module includes: a comparing unit, configured to compare the signal strength with a current threshold value, wherein the threshold value is set to identify a sensitivity of the touch screen; and the adjusting unit is configured to be compared according to the comparison As a result, the threshold value is adjusted. Optionally, the adjusting unit is set to at least one of the following: when the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is higher than N, the threshold value is increased Reducing the sensitivity of the touch screen; or wherein the signal strength is lower than the threshold value, or wherein the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value Below L, the threshold is lowered to increase the sensitivity of the touch screen; wherein, the L is smaller than the N; the signal strength is higher than the threshold and the signal strength and the threshold are In the case where the difference is greater than L and less than N, the threshold is maintained. Optionally, the adjusting unit is configured to adjust the threshold value to include at least one of: if the difference P between the signal strength and the threshold value is higher than the N, increase the threshold value by PM, Wherein M is a value between the L and the N; if the difference P between the signal strength and the threshold is lower than the L, it is determined whether the threshold is lowered after the MP is Above the first threshold, if the value is higher, the threshold value is decreased by MP, and if not higher, the threshold value is lowered to a first threshold value, wherein the first threshold value is allowed a minimum value; if the signal strength is lower than the threshold value, determining whether the threshold value is lowered by M+P is higher than the first threshold value, and if the threshold value is higher, the threshold value is lowered by M +P, if not higher than the threshold value is lowered to the first threshold value. According to the embodiment of the present invention, the signal strength of the signal generated by the touch object touching the touch screen is adopted; the sensitivity of the touch screen is adjusted according to the signal strength, and the sensitivity of the touch screen sensitivity is not solved in the related art, and the sensitivity cannot be With the different signal strengths generated by different touch objects, the user's operation of the touch screen terminal is inconvenient, and the sensitivity of the touch screen is flexibly adjusted, thereby improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1 is a flowchart of a sensitivity adjustment method according to an embodiment of the present invention; FIG. 2 is a block diagram of a sensitivity adjustment apparatus according to an embodiment of the present invention; FIG. 3 is a preferred embodiment of a sensitivity adjustment apparatus according to an embodiment of the present invention. FIG. 4 is a structural diagram of a touch screen mobile terminal device according to an embodiment of the present invention; FIG. 5 is a flowchart of a method for adaptively adjusting a touch screen sensitivity according to an embodiment of the present invention; 6 is a preferred flow diagram of a method of adaptively adjusting touch screen sensitivity in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In this embodiment, a method for adjusting sensitivity is provided. FIG. 1 is a flowchart of a method for adjusting sensitivity according to an embodiment of the present invention. As shown in FIG. 1, the process includes the following steps:

S102: Acquire a signal strength of a signal generated by the touch object contacting the touch screen;

S104: Adjust the sensitivity of the touch screen according to the signal strength. Through the above steps, the signal intensity of the signal generated by the touch object touching the touch screen is first acquired, and the sensitivity of the touch screen is adjusted according to the signal intensity, so that the sensitivity of the touch screen of the terminal is dynamically changed according to the signal strength generated by the touch object touching the touch screen. Compared with the sensitivity of the touch screen in the related art, the sensitivity of the touch screen is fixed at the factory, or the sensitivity of the touch screen is automatically selected in advance, but the system will fix the sensitivity before the next selection. In this embodiment, in the above steps, The sensitivity of the touch screen is automatically adjusted, and the user can switch between touch fingers such as naked fingers, gloved fingers, stylus, etc., and the touch screen can achieve the purpose of adjusting sensitivity according to the difference of signal strength generated by the touch screen, thereby improving the user. Experience. As an alternative embodiment, the threshold of the touch screen may be used to identify the sensitivity of the touch screen, and increasing the threshold may reduce the sensitivity of the touch screen; lowering the threshold may increase the sensitivity of the touch screen. Obtaining the signal strength of the signal generated by the touch object contacting the touch screen may have various implementation manners. In this embodiment, an optional implementation manner is provided. In the preferred embodiment, the touch object contact is obtained by acquiring a predetermined duration. The average intensity value of the signal generated by touching the screen is taken as the signal strength. This treatment can reduce the false positive rate. In this alternative embodiment, the signal strength of the signal generated by the touch object touching the touch screen is compared with the current threshold value of the touch screen, and the threshold value of the touch screen is adjusted according to the result of the comparison, and finally the purpose of adjusting the sensitivity is achieved. In order to make the touch screen more sensitive to the signal generated by the touch object, in the embodiment, a better implementation is provided. Adjusting the threshold according to the comparison result may include at least one of the following: In the case where the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is higher than N, the threshold value is increased, and the sensitivity of the touch screen is lowered; in the case where the signal strength is lower than the threshold value, or, at the signal strength Above the threshold value and the difference between the signal strength and the threshold value is lower than L, the threshold value is lowered, and the sensitivity of the touch screen is improved; wherein L is less than N; the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value When the value is greater than L and less than N, the threshold value is maintained unchanged. Through the above several preferred embodiments, the adjustment of the screen can be made more in line with the user's experience. There are many ways to adjust the threshold. For example, you can use a fixed value to adjust the threshold. In this embodiment, a preferred adjustment mode is provided. The threshold value may be adjusted to include at least one of the following: when the difference P between the signal strength and the threshold value is higher than N, the threshold value is increased by PM, where, M For the value between L and N; in the case where the difference P between the signal strength and the threshold value is lower than L, it is judged whether the threshold value is lower than the first threshold value after the MP value is lowered, and if it is higher than the threshold value Decrease MP, if not higher, lower the threshold to the first threshold, where the first threshold is the lowest allowed; and if the signal strength is lower than the threshold, judge the threshold to decrease M Whether +P is higher than the first threshold, if it is higher, the threshold is lowered by M+P, and if it is not higher, the threshold is lowered to the first threshold. Wherein, if the threshold value is lower than the first threshold, the touch screen may receive interference from the LCD or the charger to generate an automatic report, so the threshold value is not lower than the first threshold. With the above embodiment, the threshold value of the touch screen can be set to an appropriate value lower than the signal strength of the signal generated by the touch object touching the touch screen. In the embodiment, a device for adjusting the sensitivity is also provided, and the device is configured to implement the above device. The description of the device in the device is not described here. The definition of the module, for example, the acquisition module, is set to obtain the signal strength of the signal generated by the touch object touching the touch screen, and may also be expressed as "a signal intensity that is set to obtain a signal generated by the touch object contacting the touch screen. Module", the functions of the modules described below can be implemented by a processor. 2 is a block diagram of a sensitivity adjustment apparatus according to an embodiment of the present invention. As shown in FIG. 2, the apparatus includes: an acquisition module 22 and an adjustment module 24. The obtaining module 22 is configured to acquire a signal strength of a signal generated by the touch object contacting the touch screen; and the adjusting module 24 is configured to adjust the sensitivity of the touch screen according to the signal strength. Optionally, the acquisition module 22 is configured to obtain an average intensity value of a signal generated by the touch object touching the touch screen within a predetermined duration as the signal strength. FIG. 3 is a block diagram 1 of a sensitivity adjustment apparatus according to an embodiment of the present invention. As shown in FIG. 3, the adjustment module 24 further includes: a comparison unit 32 and an adjustment unit 34. Optionally, the adjustment module 24 includes: a comparison unit 32 configured to compare the signal strength with a current threshold value, wherein the threshold value is set to identify the sensitivity of the touch screen; the adjustment unit 34 is configured to adjust the threshold according to the comparison result value. Optionally, the adjusting unit 34 is further configured to: at least one of the following: when the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is higher than N, the threshold value is increased, and the sensitivity of the touch screen is lowered; If the signal strength is lower than the threshold value, or if the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is lower than L, the threshold value is lowered to improve the sensitivity of the touch screen; wherein, L is less than N; When the signal strength is higher than the threshold and the difference between the signal strength and the threshold is greater than L and less than N, the threshold is maintained. Optionally, the adjusting unit 34 is configured to adjust the threshold value to include at least one of the following: if the difference P between the signal strength and the threshold value is higher than N, the threshold value is increased by PM, where M is at L and N The value between the signal strength and the threshold value P is lower than L, it is judged whether the threshold value is lower than the first threshold value after the MP value is lowered, and if it is higher, the threshold value is lowered by MP, if not high Then, the threshold value is lowered to the first threshold value, wherein the first threshold value is the lowest allowed value; if the signal strength is lower than the threshold value, it is judged whether the threshold value is lowered after M+P is higher than The first threshold, if higher, lowers the threshold by M+P, and if not, lowers the threshold to the first threshold. The following description will be made in conjunction with the preferred embodiments. The purpose of the preferred embodiment is to provide a method for automatically adjusting the sensitivity of the touch screen according to the signal strength generated by the touch object, and to solve the problem that the sensitivity is fixed to the user to operate the touch screen terminal. Through the method provided by the preferred embodiment, the user can conveniently switch between a touch finger such as a bare finger, a gloved finger, a stylus, etc., and the touch screen can automatically adjust the threshold value of the touch screen according to the difference in signal strength generated by the touch screen, and finally The purpose of adjusting the sensitivity is achieved, and the user experience is improved. In the preferred embodiment, the "signal strength" is used to adjust the sensitivity. The preferred embodiment can be applied to a capacitive touch screen. According to the working principle of the capacitive touch screen, the same conductive object (such as a hand-held 8 mm diameter copper column) Touch the screen, the signal strength is independent of the strength of the user. The method of adjusting the sensitivity by using the "average pressure value" of the screen can be used for a resistive touch screen, and is not suitable for a capacitive touch screen. The preferred embodiment is faster and more efficient and closer to the needs of the user. A method for adaptively adjusting the sensitivity of the touch screen proposed by the preferred embodiment adopts the following steps: Step 1: Collect an average intensity value of the touch signal within a preset time. Step 2: Determine whether the current touch screen threshold S is appropriate according to the collected average intensity value. Step 3: If the current touch screen threshold value s is low, the touch screen threshold value is increased, that is, the touch screen sensitivity is lowered. Step 4: If the current touch screen threshold value s is high, the touch screen threshold value is lowered, that is, the touch screen sensitivity is improved. Step 5: If the current touch screen threshold value s is just right, the touch screen threshold value remains unchanged, that is, the touch screen sensitivity is unchanged. The method provided by the preferred embodiment can automatically adjust the sensitivity of the touch screen according to the signal strength generated by the touch object, and the user can conveniently The touch between the naked fingers, the gloved fingers, the stylus and other touch entities, the touch screen can automatically adjust the threshold of the touch screen according to the different signal strengths generated, and finally achieve the purpose of adjusting the sensitivity, thereby improving the user experience. The preferred embodiment is described below with reference to the accompanying drawings. To solve the above technical problem, the technical solution adopted by the preferred embodiment includes the following modules, as shown in FIG. 4: Touch screen panel: The panel can sense the finger, the stylus, and the like. Signal Acquisition Module: Set to scan the touch screen panel and collect the signal strength of the touch action. This module implements the functions of the acquisition module 22 described above. The threshold value judgment module: compares the average intensity value of the obtained touch signal with the current touch screen threshold value to determine whether the current threshold value is appropriate. This module implements the functions of the above-described adjustment module 24. Sensitivity adjustment module: Adjust the sensitivity of the touch screen by adjusting the threshold of the touch screen. FIG. 5 is a flowchart of a method for adaptively adjusting a touch screen sensitivity according to the preferred embodiment. As shown in FIG. 5, the process includes the following steps:

5501. Collect the average intensity value of the touch signal within the preset time.

5502. Determine whether the current threshold value S is low according to the average intensity value. S503, if the current threshold value S is low, the current threshold is increased, and the sensitivity of the touch screen is lowered.

5503. If the current threshold value S is not low, it is determined whether the current threshold value S is too high.

5504, if the current threshold value S is high, the current threshold value is lowered to improve the sensitivity of the touch screen.

5505. If the current threshold value is just right, the current threshold value is maintained and the sensitivity of the touch screen remains unchanged. A simple process is depicted in Figure 5. 6 is a preferred flowchart of a method for adaptively adjusting a touch screen sensitivity according to the preferred embodiment, and FIG. 6 depicts a flow chart of a preferred adjustment. As shown in FIG. 6, the flow includes the following steps:

5601. Collect the average intensity value of the touch signal within the preset time.

5602. Determine whether the average intensity of the collected signal is greater than a current threshold S.

5603. Determine whether the difference P between the average signal strength and the current threshold S is between the data threshold L and the data threshold N. Wherein the data threshold L is less than the data threshold N.

5604, if the difference P between the average signal intensity and the current threshold S is between the data threshold L and the data threshold N, the current threshold of the touch screen remains unchanged.

5605, if the current threshold value of the touch screen remains unchanged, the sensitivity of the touch screen remains unchanged.

5606. Determine whether a difference P between the average signal strength and the current threshold exceeds a data threshold N.

S607, if the difference P between the average signal intensity and the current threshold exceeds the data threshold N, the current touch screen threshold is low, the sensitivity is too high, and the false alarm point may be generated when the finger does not touch the screen. Then raise the current threshold of the touch screen to S+(P-M). The data threshold M is located between the data thresholds L and N. When the signal strength is higher than the threshold value, M indicates that the sensitivity set at this time is appropriate.

S608, after the current threshold value of the touch screen is raised, the sensitivity of the touch screen is lowered. S609, if the difference P between the average signal strength and the current threshold is neither between the data thresholds L and N, nor exceeds the data threshold N, indicating that the difference P between the average signal strength and the current threshold is less than the data threshold L, that is, the description The average intensity of the touch signal is close to the current threshold, and the actual touch signal may fluctuate around the threshold, and the threshold value needs to be lowered. First, it is judged whether S-(MP) is higher than the first threshold. S610, if S-(MP) is higher than the first threshold, the current threshold of the touch screen is lowered to S-(MP).

5611. If S-(M-P) is not higher than the first threshold, the current threshold of the touch screen is lowered to the first threshold. If the threshold is lower than the first threshold, the touch screen may receive interference from the LCD or the charger to generate an automatic report, so the threshold cannot be lower than the first threshold.

5612. If the average intensity of the touch signal is not greater than the current threshold S, the current threshold is low, and it is first determined whether S-(M+P) is higher than the first threshold.

5613, if S-(M+P) is higher than the first threshold, the current threshold of the touch screen is lowered to S-(M+P). If S-(M+P) is not higher than the first threshold, proceed to step S611 to lower the current threshold of the touch screen to the first threshold.

5614, the touch screen threshold is reduced, and the sensitivity of the touch screen is improved. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or they may be Multiple modules or steps are made into a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention. Industrial Applicability The embodiment of the present invention can be applied to the field of touch technology, and adopts a signal strength of acquiring a signal generated by a touch object contacting a touch screen; adjusting sensitivity of the touch screen according to the signal strength, and solving the related art because of touch The fixed sensitivity of the screen causes the sensitivity to be flexibly adjusted with different signal strengths generated by different touch objects, causing inconvenience to the user to operate the touch screen terminal, achieving the purpose of flexibly adjusting the sensitivity of the touch screen, and improving the user experience. .

Claims

Claim

1. A sensitivity adjustment method, including:

Obtaining a signal strength of a signal generated by the touch object touching the touch screen;

The sensitivity of the touch screen is adjusted according to the signal strength.

2. The method according to claim 1, wherein acquiring a signal strength of the signal generated by the touch object contacting the touch screen comprises:

An average intensity value of a signal generated by the touch object touching the touch screen within a predetermined duration is obtained as the signal strength.

The method according to claim 1 or 2, wherein adjusting the sensitivity of the touch screen according to the signal strength comprises:

Comparing the signal strength to a current threshold value, wherein the threshold value is used to identify a sensitivity of the touch screen;

The threshold value is adjusted based on the result of the comparison.

4. The method according to claim 3, wherein adjusting the threshold according to the result of the comparison comprises at least one of the following:

In a case where the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is higher than N, the threshold value is increased to reduce the sensitivity of the touch screen;

In the case where the signal strength is lower than the threshold value, or when the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is lower than L, the threshold is lowered. a value that increases the sensitivity of the touch screen; wherein, L is less than the N;

In the event that the signal strength is above the threshold and the difference between the signal strength and the threshold is greater than L less than N, the threshold is maintained.

5. The method according to claim 4, wherein adjusting the threshold value comprises at least one of: in a case where a difference P between the signal strength and the threshold value is higher than the N, The threshold value is increased by PM, where M is a value between the L and the N;

In a case where the difference P between the signal strength and the threshold value is lower than the L, it is determined whether the threshold value is lower than the first threshold value after the MP value is lowered, and if the threshold value is higher than the first threshold value, Lower the MP, If not higher, the threshold value is lowered to a first threshold, wherein the first threshold is the lowest allowed value;

In the case that the signal strength is lower than the threshold value, it is determined whether the threshold value is lowered by M+P or higher than the first threshold value, and if it is higher, the threshold value is lowered by M+P, if If not higher, the threshold value is lowered to the first threshold value. A sensitivity adjusting device includes:

An acquisition module is configured to obtain a signal strength of a signal generated by the touch object contacting the touch screen; and an adjustment module configured to adjust a sensitivity of the touch screen according to the signal strength. The apparatus according to claim 6, wherein the acquisition module is configured to acquire an average intensity value of a signal generated by the touch object contacting the touch screen within a predetermined duration as the signal strength. The apparatus according to claim 6 or 7, wherein the adjustment module comprises:

a comparing unit, configured to compare the signal strength with a current threshold value, wherein the threshold value is set to identify a sensitivity of the touch screen;

The adjustment unit is set to adjust the threshold value according to the result of the comparison. The apparatus according to claim 8, wherein the adjustment unit is configured to perform at least one of: the signal strength is higher than the threshold value and the difference between the signal strength and the threshold value is higher than N In the case of increasing the threshold value, reducing the sensitivity of the touch screen;

In the event that the signal strength is above the threshold and the difference between the signal strength and the threshold is greater than L less than N, the threshold is maintained. The apparatus according to claim 9, wherein the adjustment unit is configured to perform at least one of: in a case where a difference P between the signal strength and the threshold value is higher than the N, the threshold is The value increases PM, where M is a value between the L and the N;

In the case that the signal strength is lower than the threshold value, it is determined whether the threshold value is lowered by M+P or higher than the first threshold value, and if it is higher, the threshold value is lowered by M+P, if If not higher, the threshold value is lowered to the first threshold value.