JP2010272143A - Dural sensor touch screen using projective-capacitive sensor and pressure-sensitive touch sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for determining false contact in a touch screen system. <P>SOLUTION: The touch screen system includes: a plurality of pressure sensors connected to a touch screen of the touch screen system; a plurality of electrodes connected to the touch screen, having a first portion formed along a first axis and a second portion formed along a second axis; a projective-capacitive sensor system connected to the plurality of electrodes; and a processor connected to the plurality of pressure sensors and the projective-capacitive sensor system. The processor calculates, when the plurality of pressure sensors and the projective-capacitive sensor system substantially simultaneously detect a contact on the touch screen, coordinates of the contact position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates generally to touch screens, and more particularly to a method and apparatus for discriminating false and true touch events on a touch screen.

  Touch screens are incorporated into various types of displays, including cathode ray tubes (ie, CRTs) and liquid crystal display screens (ie, LCD screens) as information input means to the data processing system. If the touch screen is placed above or integrated with the display, the user can select the displayed icon or element by touching the position corresponding to the desired icon or element. . Touch screens are commonly used in a variety of applications such as POS systems, information centers, cash dispensers (ie, ATMs), and data entry systems.

  Various types of touch screens have been developed. Unfortunately, these touch screens have at least one problem that limits their convenience in at least some applications. For example, a resistive touch screen cover sheet is susceptible to damage due to surface scratches or cuts resulting from malicious fouling. In addition, the resistive touch screen may wear out even if the screen is repeatedly pressed. This type of touch screen is also susceptible to damage by environmental factors such as moisture entering the display. A capacitive touch screen having a thin film dielectric layer as a second type of touch screen has problems when touched with a gloved hand. A capacitive touch screen having a thick film dielectric layer called a projected capacitive touch screen has a problem that a sense of touch cannot be obtained. A third type of touch screen using surface acoustic waves is susceptible to the accumulation of foreign matter (eg, raindrops) on the sensor surface. Foreign objects can also interfere with the operation of the infrared touch screen. Furthermore, for infrared touch screens, special means are required to avoid signal disturbances due to direct sunlight. The fifth type touch screen has a pressure-sensitive sensor, but is easily affected by impact and vibration.

  Various systems have been devised that utilize two different touch screen technologies, primarily as a means of responding to different touch patterns, such as a finger or stylus, for entering data.

  US Pat. No. 5,231,381 discloses a multipurpose data input device using a touch screen integrated with a digitizing tablet. The touch screen uses a variety of techniques including surface acoustic waves, pressure, capacitance, or optical touch sensors to detect the presence and position of passive inputs (eg, finger contacts). The digitizing tablet employs an active stylus mechanism to activate a capacitive sensor, an inductive capacitive sensor, or a surface acoustic wave sensor.

  US Pat. No. 5,510,813 discloses a touch panel that measures both contact position and contact pressure. This touch panel determines a contact position by monitoring a current pattern using a resistive conductive layer. The contact pressure is measured by monitoring the capacitance value between the touch panel and a second conductive panel extending substantially parallel thereto. In response to the contact, the system processes the detected contact position and contact pressure.

  U.S. Pat. No. 5,543,589 discloses a touch screen having two sensors (dual sensors), each sensor using a different resolution to determine the touch location. The two sensors are clamped together to form a single sensor so that they are detected as a single contact, such as a finger or stylus. In use, the low resolution sensor is first scanned in order to identify a rectangular region having the same size as the wide conductor of the low resolution sensor as the contact position. In order to specify the contact position using the high resolution sensor, it is necessary to scan a narrow conductor corresponding to the rectangular region specified using the low resolution sensor. Thus, the disclosed system is intended to reduce costs as well as reducing the number of scan drivers and receivers required, improving the speed of the scanning process.

  U.S. Pat. No. 5,670,755 discloses a touch panel used in one of two modes. In one mode, the touch panel operates like a conventional touch screen and the user can enter information by touching the screen with a finger, pen, or other contact means. In this mode, the two resistive layers attached to the panel contact at the contact location. The contact position is specified based on the resistance ratio. In the second mode, the touch panel functions as a digitizer using a custom stylus. Capacitive coupling at the contact point to the stylus panel is used to identify the contact point.

  US Pat. No. 5,777,607 discloses a system that senses finger contact capacitively and senses stylus contact resistively. This system uses a single resistive layer in any contact mode, and the disclosed system uses a single resistive layer in any touch mode to xy the contacts on the touch screen. Coordinates can be specified. In a preferred embodiment, if the system detects that the stylus is in use, the finger detection mode is disabled and prevents inadvertent data entry via capacitive coupling by the user's hand.

  U.S. Pat. No. 5,801,682 discloses a dual sensor touch screen and discloses compensating for variations in coordinate data from a capacitive sensor using strain gauges installed at the corners of the sensor. The data fluctuation of the capacitive sensor may be caused by a change in signal path due to, for example, a user wearing gloves.

  There is a need in the art for a method and apparatus that discriminates false contacts that can arise from external stimuli such as vibration, electrical noise, contaminants, or that confirms that there has been contact. The present invention provides such a method and apparatus, and particularly a method and apparatus that are well suited for outdoor applications.

U.S. Pat.No. 5,231,381 U.S. Pat.No. 5,510,813 U.S. Pat.No. 5,543,589 U.S. Pat.No. 5,670,755 U.S. Pat.No. 5,777,607

  The present invention provides a method and apparatus for determining false contact in a touch screen system. The system according to the present invention utilizes a plurality of different types of touch screen sensors to authenticate touch on the touch screen. Thus, the present invention addresses the problems of other types of sensors that are required in outdoor or semi-outdoor applications, particularly those that are poorly managed or where raindrops or other foreign objects are present. It is going to be solved by utilizing.

  The principle of the present invention is based on a function of confirming or authenticating a contact detected by one touch sensor by another touch sensor. When the contact is confirmed, the contact can be processed, for example, by transmitting the contact position coordinates to the operation system. On the other hand, when the contact is not confirmed, the contact is invalidated. The system includes a primary touch sensor that identifies a contact position coordinate, and a secondary sensor that authenticates the authenticity of the contact by generating an independent signal or a second contact position coordinate for comparison. It is configured as. Furthermore, the contact position coordinates can be authenticated before or after the first contact is authenticated. The pressure sensitive sensor and the projected capacitive sensor system are particularly adapted to the requirements in outdoor or semi-outdoor applications.

  According to one embodiment of the present invention, a projected capacitive sensor is used as a primary sensor, and one or more pressure sensitive sensors are used to authenticate the contact. In this embodiment, a pressure sensitive sensor is used to determine when the object contacts the contact surface. Preferably, the system according to the present invention is set as a requirement that a predetermined pressure needs to be applied to the touch screen in order to detect contact. When a pressure equal to or higher than a predetermined pressure is applied to the touch screen, the system determines whether the projected capacitive sensor has detected contact. If the projected capacitive sensor does not detect contact, the contact is invalidated, the system returns to the ready mode, and if the projected capacitive sensor detects contact, the contact coordinate position Is identified. In a further preferred embodiment, a non-contact threshold is set. This threshold value may be equal to, for example, the signal amplitude of the projected capacitive sensor when contact is first detected by the pressure sensor.

  According to another embodiment of the present invention, a plurality of pressure sensors are used as primary sensors to accurately identify contact position coordinates, while a projected capacitive sensor is used as a secondary sensor to provide primary The contact detected by the sensor is authenticated. In this embodiment, since the projected capacitive sensor is used only for authentication of the contact, the number of electrodes used can be extremely reduced, making the touch screen easier to manufacture and necessary. Electronic wiring can be minimized. In the system of this embodiment, after the pressure-sensitive sensor detects a contact, the projection-type capacitive sensor is used to determine whether the contact is due to a conductive object having a ground potential. If the contact is authenticated, contact position coordinates are generated by the primary sensor and the system returns to the ready mode. In the simplest configuration, if the contact is not authenticated, the system simply returns to the preparation mode without identifying the contact coordinates or not reporting the position coordinates to the operating system. In an alternative configuration, if the contact is not authenticated, the pressure threshold value of the pressure-sensitive sensor is adjusted in order to avoid false detection as much as possible.

  According to another embodiment of the present invention, accurate contact position coordinates can be specified using each of the projected capacitive method and the pressure-sensitive sensor. In this embodiment, the system is configured to determine which sensor can identify the exact position coordinates for a given set of conditions.

  A full understanding of the features and advantages of the present invention may be realized by reference to the following specification and drawings.

3 is a flowchart showing a basic method according to the present invention. 6 is a flowchart illustrating an alternative method according to the present invention. It is a figure which shows a pressure sensor. FIG. 3 illustrates one or more pressure sensitive sensors attached to a touch screen. It is a figure which shows the pressure-sensitive touch sensor of a projection capacitive type. FIG. 6 is a cross-sectional view of the projected capacitive pressure-sensitive touch sensor shown in FIG. 5. It is a figure which shows embodiment using a projection type capacitive sensor as a primary sensor, and one or more pressure-sensitive sensors as a secondary sensor. 8 is a flowchart illustrating a preferred method using the embodiment shown in FIG. It is a figure which shows embodiment using a several capacitive sensor as a primary sensor, and a projection type capacitive sensor as a secondary sensor. 10 is a flowchart illustrating a preferred method using the embodiment shown in FIG. 6 is a flowchart illustrating a method used in an embodiment of the present invention in which both a projected capacitive sensor and a pressure sensitive touch sensor specify contact position coordinates. It is a general block circuit diagram of a sensor element detection circuit. FIG. 13 is a diagram showing a projected capacitive sensor element used in the circuit shown in FIG. 12. It is a figure which shows the pressure-sensitive sensor element used with the circuit shown in FIG.

  FIG. 1 is a flowchart illustrating a preferred method of operation of the present invention. In step 101, the touch screen is in a pre-contact or ready state. The screen is then touched by, for example, a finger or a finger wearing a glove (step 103). At this time, the primary touch sensor detects contact (step 105). Before the primary touch sensor determines the contact coordinates, or before the primary touch sensor sends any information (such as contact position and contact mode) to the operating system, the secondary sensor must be touched by the primary sensor. It is confirmed that the contact has been made (step 107). When it is confirmed that the contact is effective by the secondary sensor (step 109), the contact position is specified (step 111). Depending on the desired configuration, the contact coordinate position can be identified using a primary sensor or a secondary sensor. Then, the touch controller sends contact information such as contact position coordinates to the operation system (step 113). If the secondary sensor determines that the touch sensed by the primary sensor is not valid, no touch information is sent to the operating system and the touch sensor returns to the ready state 101. The advantage of this embodiment is that it does not take time to locate the determined contact that is invalid, the system can quickly confirm that a valid contact has been sensed, and the contact is invalid If so, it is possible to immediately return to the ready state.

  The system slightly modified as shown in FIG. 2 specifies the contact position (step 201) after the primary sensor detects contact (step 105). After identifying the contact position, the system determines whether or not the secondary sensor has also detected contact (step 107). If the result is affirmative, the contact is confirmed (step 109) and the position coordinate is determined by the operation system. (Step 203). Alternatively, after the contact position is specified (step 201), a contact threshold value dependent on coordinates is set for the secondary sensor (step 205), and the coordinate-dependent contact sensitivity is set.

  In a preferred embodiment of the present invention, only one sensor, preferably a secondary sensor, determines whether contact has been detected. Since the sensor does not specify an accurate contact position, an inexpensive sensor may be used. Alternatively, the sensor may be designed to identify a rough contact position. For example, the sensor may be designed to identify which quadrant of the screen has been touched. In a third alternative, the sensor can be designed to identify the actual coordinates of the touch location to provide system redundancy.

  Preferably, one sensor is a projected capacitive sensor and the other sensor is a pressure sensitive sensor. It is possible to design the system so that one sensor functions as a primary sensor and functions as a sensor for specifying contact position coordinates, and the other sensor functions only as an authentication sensor. In at least one embodiment of the present invention, both sensors can accurately identify touch coordinates to provide redundancy and achieve a more sophisticated touch authentication method. Alternatively, the first sensor accurately identifies the contact coordinates, and the second sensor roughly determines the contact coordinates (eg, in any quadrant of the touch screen). Also good.

  The design and use of touch screen pressure sensitive sensors are well known to those skilled in the art and will not be described in detail herein. A typical pressure sensitive sensor is the temperature compensated strain gauge disclosed in US Pat. No. 5,742,222. The pressure sensitive sensor may be one using a piezoelectric system disclosed in US Pat. No. 4,355,202 and US Pat. No. 4,675,569, and European Patent Application Publication No. EP0754936. In the present invention, it is preferable to employ pressure-sensitive pressure sensors shown in GB2310288A, GB2321707A, and GB2326719A. FIG. 3 is based on FIG. 5a of GB 2 GB 2707A, but shows two such pressure sensitive sensors 300. FIG.

  As illustrated, the piezoresistive pressure sensor 300 may be installed between one or more corners (corner portions) of the touch plate 301 and the support structure 303. Each pressure-sensitive sensor 300 is made of a piezoresistive material 305, and the resistance changes according to the applied pressure. Using the upper electrode 307 and the lower electrode 309, the electric resistance of the piezoresistive material 305 can be measured. In order to ensure the mechanical strength of the pressure sensitive sensor structure, a sensor substrate 311 is provided. If necessary, an insulating layer (not shown) may be added to ensure electrical insulation. Usually, the detection electric circuit unit is one in which the pressure-sensitive sensor 300 is incorporated in a Wheatstone bridge circuit in order to easily detect a minute change in resistance.

  A pressure sensitive sensor as shown in FIG. 3 has many advantages. First, according to such a configuration, it is possible to be robust against environmental changes without being affected by changes in ambient temperature and humidity. Second, the pressure can be measured directly. Third, since it can withstand extremely large urging pressure, it can be mechanically incorporated as a simple washer when assembled with a bolt.

  The pressure-sensitive sensor can be attached to the touch screen in a superimposing manner (such as superimposing) or a non-superimposing manner, and depends on whether the touch is authenticated or the touch coordinates are detected. Alternatively, a plurality of sensors may be used. In the simplest configuration shown in FIG. 4, a single pressure sensor 401 is disposed on the touch screen 405. When a single pressure sensor is used, a low rigidity support member is arranged at the corner portion 406 and a high rigidity support member is arranged at the corner portion 408, or an area where contact sensitivity is limited, or A region that does not have contact sensitivity may not be formed. Preferably, it is located just outside the display area of the screen 405 and below the cowling 407 of the touch screen. Alternatively, as disclosed in U.S. Pat. No. 5,708,460, four pressure sensitive sensors 401-404 may be arranged, one at each corner.

  It should be noted that a single pressure sensor 401 typically has a contact sensitivity that depends on the contact location. The contact sensitivity depends on the mounting method of the touch screen 405 (for example, a solid mounting method or a flexible mounting method). Therefore, when a single pressure sensor is used for contact authentication, the contact threshold of the pressure sensor is preferably set based on a contact position specified by a projection capacitive sensor described in detail below.

  The other sensor used in the preferred embodiment of the present invention is a projected capacitive sensor. 5 and 6 are a front view and a cross-sectional view, respectively, of a projected capacitive touch sensor disclosed in US Pat. No. 5,844,506, the contents of which are hereby incorporated by reference as a single unit. . According to this configuration, an electrode pattern 503 formed by thin wire electrodes, a resistive film pattern, or other standard electrodes are disposed on the substrate 501. The protective overlay layer 601 prevents damage when the electrode 503 is used. As described above, the projected capacitive sensor 503 can be used to specify an accurate contact position or simply to authenticate contact. In general, the electrode spacing is determined by the application, i.e., the electrode spacing is narrow when used to identify the exact contact location, and when used simply to authenticate contact. It is wide.

U.S. Pat. No. 5,650,597, U.S. Pat. No. 4,954,823, International Patent Application Publication No. WO95 / 27334, and International Patent Application Publication No. WO96 / 15464, the contents of which are hereby incorporated by reference. The projected capacitive touch screen disclosed in (1) monitors changes in the capacitance of the touch screen. Unlike capacitive sensors with a thin film dielectric layer, the capacitance of a projected capacitive sensor does not change only by contact with an object with ground potential, but with an object with ground potential. Also changes as the sensor approaches the sensor.
Therefore, the first problem with these types of touch screens is that there is variation in the size of the object having the ground potential used. For example, the signal when touched with a small finger (eg a child's finger) is substantially smaller than the signal when touched with a large finger. Also, as expected in outdoor applications, the signal when a person wearing gloves touches is considerably smaller than the signal when a person not wearing gloves touches.
Also, another problem can arise if the user is too close to a portion of the screen, for example by holding the hand over a surface close to the screen. That is, a system that uses only one signal level as a threshold detects that there was contact before the actual contact (for example, by recognizing the user's large hand as a child's finger), depending on the threshold, Alternatively, the single signal level threshold system may be used to determine the actual contact location because it may completely ignore the contact (ignoring the child's finger because it was set to recognize an adult finger) Does not work well.

  Unlike touch screens using projected capacitive sensors, touch screens using pressure sensitive sensors do not have recognition problems due to various finger sizes. Moreover, the pressure-sensitive sensor has no problem in recognizing a hand wearing a glove, a stylus, a pen, or the like. However, touch screens using pressure sensitive sensors have the problem of spurious signals due to mechanical noise. For example, when the touch screen vibrates, the reference mass vibrates and generates an extrinsic background signal. In addition, the extrinsic background signal may make the system unable to recognize a valid touch.

  In an outdoor application, a touch screen using a pressure-sensitive sensor may cause a contact position error due to wind. For example, when the wind is blowing parallel to the touch screen, the pressure applied to the left portion of the screen by the person standing in front of the touch screen may be asymmetric with the pressure applied to the right portion. Due to this pressure imbalance, the pressure sensitive sensor on the touch screen will identify the wrong contact coordinates. The degree of position error depends on the degree of pressure asymmetry due to the wind on the touch screen. These asymmetries depend on the wind speed, the angle between the wind and the screen, the degree of airflow change by the obstruction (ie the user), the size of the screen, and the degree of force applied by the user's contact.

  Another problem with pressure sensitive sensors arises when trying to implement a drag and untouch function. In order to realize this function, the signal of the pressure sensor needs to be processed well within the sub-hertz range. Unfortunately, however, it is difficult to provide subhertz information because pressure-sensitive sensors essentially generate a signal that is a time derivative of the applied pressure. A pressure sensitive sensor that generates a signal proportional to the applied pressure may have problems processing subhertz information due to mechanical noise.

  In the embodiment of the present invention shown in FIG. 7, the primary sensor is a projected capacitive sensor having an electrode array composed of a plurality of electrodes 503. This projected capacitive sensor is connected to a processor 701 and uses this processor to identify contact position coordinates. The secondary touch sensor is a pressure-sensitive sensor, and includes pressure-sensitive sensors 401 to 404 as illustrated. It should be understood that contact authentication may be performed using a single pressure sensitive sensor 401. Therefore, as shown in FIG. 7, the output of the sensor 401 is connected to the monitor 703 and the determination unit 705 for authenticating the contact, or the pressure sensitive sensors 402 to 404 are used to specify the contact coordinates as a secondary. Can be connected directly to the processor 701 together with the output from the.

  In the embodiment shown in FIG. 7, the pressure sensitive sensor is only used to determine when the finger contacts the contact surface. That is, the system is set to require that a predetermined pressure is applied to the screen 501 in order to detect “contact”. For example, when a plurality of pressure sensors 401 to 404 are used, the sum of signals from these pressure sensors needs to exceed a threshold value. In this embodiment, since the pressure sensitive sensor need not support a drag and untouch function, the pressure sensitive sensor signal can be processed using a relatively narrow frequency filter. By using a narrow frequency filter, mechanical background noise due to vibration of the reference mass can be suppressed relatively easily.

  FIG. 8 shows a preferred method using the system according to the embodiment shown in FIG. Initially, the system is in a ready mode while waiting for contact (step 801). The pressure-sensitive sensor detects contact by determining that the pressure applied to the touch screen exceeds a predetermined threshold (step 803), and the system detects the contact of the projected capacitive sensor as well. It is confirmed whether or not it has been done (step 805). If the projected capacitive sensor does not detect contact, the system returns to the ready mode (step 801) and the contact is considered invalid. If the projected capacitive sensor has detected contact, in a preferred embodiment of the present invention, a non-contact threshold is set (step 807). This threshold value may be equal to a predetermined ratio (for example, 50%) with respect to the amplitude of the projected capacitive signal when the pressure sensor is first detected. In an alternative embodiment, the step of setting the threshold may be omitted by using a preset threshold.

  In the next step, the coordinates of the contact position are generated (step 809). In a preferred embodiment, the position coordinates are specified by a projected capacitive system. Preferably, the system continues to monitor the projected capacitance signal and continues to generate position coordinates as long as the projected capacitance signal exceeds the non-contact threshold (step 811). Thus, if the user performs a drag action (ie dragging a finger across the screen), the system continues to generate the necessary contact position information. When the projected capacitance signal falls below the non-contact threshold, the system generates a non-contact message and final position coordinates (step 813) and then returns to the preparation mode.

  The system described above has a number of advantages. First, by using a pressure sensitive sensor, a projected capacitive system prior to actual contact, i.e., when the user's finger or hand is simply in the vicinity of the screen and is not touching the screen. Can eliminate the possibility of responding to contact. Secondly, problems caused by the difference in finger size, that is, capacitance (eg, small fingers for large fingers, fingers wearing gloves and fingers not wearing) by using the threshold setting step described above. Can be solved. Third, since a drag-and-untouch function can be realized using a projected capacitive system, the typical problem associated with processing of subhertz information when using a pressure sensor is solved. be able to. Fourth, in this embodiment, the pressure sensor is used only to authenticate that there was a contact, not to identify the exact contact location, so calibration and stability associated with the pressure sensor In addition to this problem, it is possible to avoid the problem of false contact due to wind or large vibrations.

  According to the second embodiment using the combination of the projected capacitive sensor and the pressure sensitive sensor shown in FIG. 9, the projected capacitive sensor is used only to confirm that there was a true contact. In order to specify an accurate position, pressure-sensitive sensors 401 to 404 are used. In this system, the pressure sensor is set in a standard configuration to achieve the required accuracy using techniques well known to those skilled in the art. In contrast, projected capacitive sensors are designed for minimal accuracy and require a small number of electrodes 503, that is, as few as one electrode 503. It is. It is preferable to achieve higher accuracy and performance using one or more electrodes 503. Even when multiple electrodes are used, the projected capacitive system is not used to ultimately identify the contact location, so the number of electrodes and electrical channels required is substantially reduced. Can be reduced. Furthermore, since the projected capacitive electrode is used only to confirm contact, it does not require both x and y axis electrodes and avoids complicating sensors and electronics. Can do. As shown in the figure, the output of the projected capacitive sensor is connected to the processor 701 via the monitor 703 and the discriminating unit 705, and the pressure sensitive sensors 401 to 404 directly process the processor in order to specify the coordinates of the contact position. 701 is connected.

  FIG. 10 illustrates the method of the present invention when used only as a projected capacitive sensor contact authentication sensor, as described with reference to FIG. Initially, the system is in a preparation mode (step 1001). In the first step (step 1003), the pressure sensor detects contact. Next, the projected capacitive system determines whether or not the contact is valid by determining whether or not a conductive object having a ground potential has contacted (step 1005). If the contact is verified to be valid, contact position coordinates are generated by the pressure sensor (step 1007), and the system returns to the preparation mode. According to the simplest configuration of this embodiment, if the projected capacitive system does not authenticate that there was a valid contact, the system only returns to the ready mode. According to an alternative configuration, if the contact is determined to be invalid, the system adjusts the threshold of the pressure sensor (step 1009). For example, the required pressure threshold can be increased to eliminate false contact detection (eg, false contact detection by wind). When adjusting the pressure threshold to eliminate false contact detection, optimal contact detection by automatically reducing the threshold periodically (for example, considering that noise due to wind is reduced) It is preferable to achieve accuracy. In addition to setting the threshold value of the amplitude of the pressure-sensitive sensor, the frequency spectrum of the background signal may be similarly monitored, and an appropriate frequency filter may be used as necessary. According to this configuration, when a false contact is detected by the projected capacitive sensor, the frequency spectrum of the background signal is confirmed and an appropriate frequency filter is used. As in the case of the pressure threshold, it is preferable to periodically cancel the frequency filter or periodically remeasure the frequency spectrum so that unnecessary filtering processing is not performed as a result.

  According to one embodiment of the present invention, both the projected capacitive sensor system and the pressure sensitive sensor system may be capable of specifying contact position coordinates. In this embodiment, the contact algorithm of the system is designed to determine which sensor system will yield the most accurate position coordinates under a given condition. The contact position coordinates are obtained using the selected sensor system. FIG. 11 shows a method used in this dual sensor system.

  Initially, the contact detection system is in a preparation mode (step 1101). It is preferable that the pressure-sensitive sensor first detects contact (step 1103) to avoid erroneous detection due to approach that may occur with the projected capacitive sensor. When contact is detected with a pressure-sensitive sensor and authenticated with a secondary sensor system (ie, a projected capacitive sensor in the preferred embodiment) (step 1105), the contact algorithm can determine the finger size or conductivity. In order to eliminate the problem due to the difference, the threshold value of the projected capacitive sensor is adjusted (step 1107). Since both sensors can specify positions with sufficient accuracy, in the next step, a deviation (difference) between the contact positions detected by the two sensors is determined (step 1109). If the misalignment is greater than a reasonable value (i.e., greater than that which may be due to wind, hand size, etc.), the system invalidates the contact and returns to the ready mode. If the misalignment between the two contact positions is within acceptable limits, the contact is authenticated and processing continues.

  Next, the contact algorithm determines which touch sensor should use the contact position when specifying the contact coordinates (step 1111). For example, the contact algorithm may recognize that the system is being used in drag mode when it determines that the contact location continues to change before the non-contact message is sent (step 1113). In this case, in general, the projected capacitive system is more effective in supporting the drag mode as described above. Therefore, the projected position is separated from the contact position using the projected capacitive system. It is preferable to specify (that is, the non-contact position) (step 1115). Alternatively, if the system determines that background noise caused by vibration or wind is too great (step 1117), the touch algorithm may select a projected capacitive sensor (step 1119). ). In cases other than the above, the contact position may be specified using a pressure sensor (step 1121).

  In an embodiment that is a slight modification of the above embodiment, if the projected capacitive sensor does not authenticate the first contact detected by the pressure sensitive sensor (step 1105), the system will detect the contact before returning to the ready mode. The threshold value of the pressure sensor may be adjusted (step 1123). As described with reference to FIG. 10, either the amplitude threshold or the frequency filter for the pressure sensor may be adjusted.

  Combining sensors as described above provides other advantages in addition to overcoming the problems of both sensor systems. For example, when the system is in the ready mode, only one sensor system need be in the ready state. That is, it is possible to reduce the power consumption by putting the other sensor system in a completely non-powered state. For example, the electrodes of the projected capacitive system may be scanned when the pressure sensitive sensor is in a standby state and activated.

  Another advantage of combining sensors as described above is that users can be identified in a limited way. For example, if the user is right-handed, the projected capacitive system tends to project the contact position due to the capacitance of the user's hand on the right side of the contact position detected by the pressure sensor. is there. Similarly, if the user is left-handed, the projected capacitive system tends to project the contact position to the left of the contact position detected by the pressure sensor. Other contact-related attribute information that can be used in the identification system includes positional displacement between the contact positions specified by the two sensor systems, pressure when touching the screen, and when the user touches multiple areas of the screen. Speed, and the time from when the user first touches to when he stops touching. The system according to the present invention can be designed to monitor only specific contact movements (eg user code of an ATM device) or to monitor all contact movements. According to one possible utilization method regarding these data, different menu screens and touch screens can be provided according to past usage situations of different users.

  Many electronic components associated with a touch screen controller are independent of the type of detector (sensor), and therefore multiple sets of electronic components are usually not required using multiple contact sensors. For example, a typical touch screen controller requires a microprocessor, RAM, ROM, analog-to-digital converter (ADC), power supply circuitry, digital circuitry that supports communication with a host computer, and a printed circuit board. That is, in many cases, many electronic components associated with the touch screen can be utilized to support a multiple sensor system.

  In some cases, other aspects of the controller electronics may be common in two different types of sensors. For example, a certain type of piezoresistive pressure-sensitive sensor can measure using an AC excitation voltage in the range of several tens of kilohertz instead of using a DC excitation voltage as a more general technique. Therefore, the same excitation frequency and the same receiving electronic component can be used for both the pressure-sensitive sensor and the electrostatic coupling type detection sensor.

FIG. 12 shows a general block circuit diagram of the sensor element detection circuit 1200. The negative feedback circuit ensures that the voltage on the feedback line 1201 is the same as the oscillation voltage V ₀ generated from the reference power supply 1203. The output from the sensor element 1205 is a signal voltage ΔV superimposed on the reference voltage V ₀ . A difference signal output voltage ΔV is obtained by adding the reference voltage line to the output line.

  FIG. 13 shows a projected capacitive sensor element used in the circuit of FIG. A variable capacitor 1301 represents a projected capacitive sensor electrode. In use, capacitance with respect to ground potential is increased by the user's finger or other object having ground potential. Resistor 1303 supports the sensing mechanism. Resistor 1303 can be integrated directly into the sensor or installed with the sensing electrode.

The feedback circuit shown in FIG. 12 can be used together with the AC detection circuit of the pressure sensor. Some pressure sensors, such as those made by C-Cubed Limited, detect using a Wheatstone bridge circuit. Therefore, as shown in FIG. 14, one or more of the four resistors 1401 to 1404 may correspond to the piezoelectric resistance element of the pressure sensor. In the illustrated embodiment, the Wheatstone bridge circuit is grounded via a capacitor 1405. Capacitor 1405 is not required, but is useful in reducing the difference between the excitation voltage and the feedback voltage to bring the ratio of ΔV to V ₀ closer to the signal from the projected capacitively coupled sensor electrode. .

  As will be appreciated by those skilled in the art, the present invention may be implemented in other specific embodiments without departing from the spirit and essential characteristics thereof. Accordingly, the description and disclosure herein is intended to be illustrative and is intended to illustrate the scope of the present invention as set forth in the appended claims, and is intended to be limiting. It is not intended to be.

300: Piezoresistive pressure sensor, 301: Touch plate, 303: Support structure, 305: Piezoresistive material, 307: Upper electrode, 309: Lower electrode, 311: Sensor substrate.

Claims (14)

A touch screen system,
A plurality of pressure sensors connected to the touch screen of the touch screen system;
A plurality of electrodes connected to the touch screen, wherein the first portion of the electrode is formed along the first axis, and the second portion of the electrode is formed along the second axis;
A projected capacitive sensor system connected to a plurality of electrodes;
A plurality of pressure sensitive sensors and a processor connected to the projected capacitive sensor system,
A processor, wherein a plurality of pressure-sensitive sensors and a projected capacitive sensor system detects a touch screen contact at substantially the same time, and calculates a position coordinate related to the touch screen.   The touch screen system according to claim 1, wherein the position coordinates are detected by a plurality of pressure sensitive sensors.   The touch screen system according to claim 1, wherein the position coordinates are detected by a projected capacitive sensor system. A method of operating a touch screen system,
Detecting the pressure applied to the touch screen of the touch screen system using at least one pressure sensitive sensor, the detected pressure corresponding to contact with the touch screen;
Confirming the touch on the touch screen detected using at least one pressure sensor using a projected capacitive sensor;
Generating position coordinates corresponding to the contact;
A method of operating the touch screen system, comprising: transmitting position coordinates to the touch screen operation system. The operation method according to claim 4,
An operation method, further comprising returning the touch screen system to a preparation mode when a negative response is received from the projected capacitive sensor with respect to the confirmation step. The operation method according to claim 5,
The operation method further comprising the step of setting a non-contact threshold for the projected capacitive sensor. The operation method according to claim 6,
An operation method, wherein the non-contact threshold has a predetermined ratio with respect to an amplitude of a projected capacitive signal when the contact is first detected by a pressure sensor. The operation method according to claim 7,
Comparing the amplitude of the projected capacitive signal corresponding to the contact with a non-contact threshold;
The operation method characterized in that the position coordinates correspond to a second contact position related to the amplitude of the projected capacitive signal that is equal to or less than the non-contact threshold value. The operation method according to claim 7,
Comparing the amplitude of the projected capacitive signal corresponding to the contact with a non-contact threshold;
An operation method comprising: generating a second set of position coordinates corresponding to a second contact position related to an amplitude of a projected capacitive signal that is equal to or less than a non-contact threshold value. The operation method according to claim 9,
Generating a non-contact message when the amplitude of the projected capacitive signal is below a non-contact threshold;
Transmitting a non-contact message to the touch screen operation system. The operation method according to claim 5,
An operation method further comprising the step of setting a pressure-sensitive sensor threshold when a negative response is received from the projected capacitive sensor in response to the confirmation step. The operation method according to claim 5,
Comparing a first contact position identified by at least one pressure sensitive sensor with a second contact position identified by a projected capacitive sensor;
And a step of returning the touch screen system to a preparation mode when the displacement between the first and second contact positions is greater than a predetermined displacement threshold. The operation method according to claim 5,
Determining a background mechanical noise level;
Comparing the background mechanical noise level to a noise threshold;
If the background mechanical noise level is less than the noise threshold, the position coordinates are generated by at least one pressure sensor, and if the background mechanical noise level is greater than the noise threshold, the position coordinates are projected electrostatically. An operation method characterized by being generated by a capacitive sensor. The operation method according to claim 5,
Determining whether the touch screen system is operating in drag mode;
If the touch screen system is not operating in the drag mode, the position coordinates are generated by at least one pressure sensor, and if the touch screen system is operating in the drag mode, the position coordinates are projected. An operation method characterized by being generated by a capacitive sensor.

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