Patent Publication Number: US-11644936-B2

Title: Position detection device, and position detection method based on electromagnetic inductive coupling and capacitive coupling

Description:
BACKGROUND 
     Technical Field 
     This disclosure relates to a position detection device that enables detection of a position indicated by a pointer through electromagnetic inductive coupling, and detection of a position indicated by a pointer through capacitive coupling, to be performed using a common position detection sensor. 
     Background Art 
     A position detection device is known which allows a position indicated by a stylus (an electronic pen) that supports a capacitive coupling method, as well as a position touched by a human finger, to be detected using a position detection sensor supporting the capacitive coupling method. However, this position detection device has a problem in that, if a human body, such as a finger, touches a surface of the position detection sensor when a position indicated by the stylus is to be detected, an accurate detection of the position indicated by the stylus will be difficult. 
     The above problem could be solved by detecting the position indicated by the stylus through a position detection sensor supporting an electromagnetic induction method, and detecting a position touched by a human finger through a position detection sensor supporting the capacitive coupling method. 
     However, if the position detection sensor supporting the electromagnetic induction method and the position detection sensor supporting the capacitive coupling method are separately provided in a position detection device, the structure of the position detection device will be complicated. 
     As such, to solve this problem, each of Patent Document 1 (Japanese Patent No. 5702511) and Patent Document 2 (Japanese Patent No. 5819565) has proposed a position detection device that allows position detection employing the electromagnetic induction method and position detection employing the capacitive coupling method to be implemented using a single common position detection sensor. 
     PRIOR ART DOCUMENT 
     Patent Documents 
     Patent Document 1: Japanese Patent No. 5702511 
     Patent Document 2: Japanese Patent No. 5819565 
     BRIEF SUMMARY 
     Technical Problems 
     However, in a position detection sensor of the position detection device proposed in Patent Document 1, a plurality of linear conductors (x-axis linear bodies and y-axis linear bodies) extending in directions perpendicular to each other are provided on a front surface and a rear surface of a substrate, and switch circuits are provided on both sides of the x-axis linear bodies and of the y-axis linear bodies to allow loop coils for electromagnetic inductive coupling to be formed and switching among the loop coils to be performed, and to allow switching among the x-axis linear bodies and the y-axis linear bodies to be performed for capacitive coupling. Accordingly, the structure of the position detection sensor is complicated. 
     Meanwhile, in a position detection sensor of the position detection device proposed in Patent Document 2, a plurality of linear conductors (x-axis linear bodies and y-axis linear bodies) extending in directions perpendicular to each other are provided on a front surface and a rear surface of a substrate, and both the x-axis linear bodies and the y-axis linear bodies are divided into linear bodies to be used in the electromagnetic induction method and linear bodies to be used in the capacitive coupling method. Accordingly, in the position detection sensor, areas that allow detection employing the electromagnetic induction method and areas that allow detection employing the capacitive coupling method exist separately, making it impossible to use the entire area of the position detection sensor for both the electromagnetic induction method and the capacitive coupling method. 
     An object of this disclosure is to provide a position detection device that is able to solve the above problems. 
     Technical Solution 
     To solve the aforementioned problems, a position detection device is provided which includes: a sensor having a plurality of first electrodes arranged in a first direction, and a plurality of second electrodes arranged in a second direction that crosses the first direction; and signal processing circuitry connected to the sensor, and configured to detect a position indicated by a first pointer on the sensor and a position indicated by a second pointer on the sensor, in which each of the first electrodes and the second electrodes is formed as a loop electrode, the signal processing circuitry includes selection circuitry configured to select the plurality of first electrodes and the plurality of second electrodes, and the selection circuitry is configured to select the first and second electrodes such that an induced electric current is induced in each of the first and second electrodes to enable the position indicated by the first pointer on the sensor to be detected through electromagnetic inductive coupling between the first pointer and the sensor, and select the first and second electrodes such that an induced electric current is not induced in each of the first and second electrodes to enable the position indicated by the second pointer on the sensor to be detected through capacitive coupling between the second pointer and the sensor. 
     On the sensor of the position detection device having the above-described structure, the plurality of first electrodes and the plurality of second electrodes are arranged as loop electrodes in the first direction and the second direction that cross each other. In addition, the loop electrodes arranged on the sensor are selected by the selection circuitry such that an induced electric current is induced in each of the loop electrodes to enable electromagnetic inductive coupling with the first pointer, enabling the position indicated by the first pointer to be detected by an electromagnetic induction method. In addition, the loop electrodes arranged on the sensor are selected by the selection circuitry such that an induced electric current is not induced in each of the loop electrodes to enable capacitive coupling with the second pointer, enabling the position indicated by the second pointer to be detected by a capacitive coupling method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram illustrating an example configuration of a position detection device according to a first embodiment of this disclosure. 
         FIG.  2    is a diagram for explaining an operating state of the position detection device according to the first embodiment in an electromagnetic induction mode. 
         FIG.  3    is a diagram for explaining an operating state of the position detection device according to the first embodiment in a capacitive coupling mode. 
         FIG.  4    is a diagram illustrating an example configuration of a position detection device according to a second embodiment of this disclosure. 
         FIG.  5    is a diagram for explaining loop electrode selection control performed by selection circuitry in the electromagnetic induction mode in a position detection device according to a first example of the second embodiment. 
         FIG.  6    is a diagram for explaining an operation of the position detection device according to the first example of the second embodiment in the electromagnetic induction mode. 
         FIG.  7    is a diagram illustrating an example arrangement of loop coils of a position detection sensor equivalent to a position detection sensor of the position detection device according to the first example of the second embodiment. 
         FIG.  8    is a diagram for explaining an operation of a position detection device according to a second example of the second embodiment in the electromagnetic induction mode. 
         FIG.  9    is a diagram for explaining the operation of the position detection device according to the second example of the second embodiment in the electromagnetic induction mode. 
         FIG.  10    is a diagram illustrating an example arrangement of loop coils of a position detection sensor equivalent to a position detection sensor of the position detection device according to the second example of the second embodiment. 
         FIG.  11    is a diagram illustrating an example configuration of a position detection device according to a third embodiment of this disclosure. 
         FIG.  12    is a diagram for explaining an operating state of the position detection device according to the third embodiment in the electromagnetic induction mode. 
         FIGS.  13 A and  13 B  illustrate diagrams for explaining other examples of position detection sensors of position detection devices according to this disclosure. 
     
    
    
     MODES FOR CARRYING OUT THE DISCLOSURE 
     First Embodiment 
       FIG.  1    is a diagram illustrating an example configuration of a position detection device  1  according to a first embodiment of this disclosure. The position detection device  1  according to this embodiment allows use of an electronic pen (a stylus) as an example of a first pointer and a human finger as an example of a second pointer, and is configured to be capable of detecting coordinates (X, Y) of a position indicated by a pointer no matter which pointer is used to indicate the position. 
     As illustrated in  FIG.  2   , an electronic pen  2 , which is the first pointer to be detected by the position detection device according to the first embodiment, includes a coil  202  wound around a magnetic core  201 , and is configured to transmit, as electromagnetic induction energy, a signal from a signal generation circuit  203  to the position detection device  1  through the coil  202  in an example described below. Note that the electronic pen  2  is provided with a battery (not illustrated) to drive the signal generation circuit  203 . 
     As illustrated in  FIG.  1   , the position detection device  1  according to this embodiment includes a position detection sensor  10 , and signal processing circuitry  20  connected to the position detection sensor  10 . In this example, the position detection sensor  10  is a transparent sensor disposed on a display screen of a display device, such as a liquid crystal display. 
     Specifically, the position detection sensor  10  according to this example is configured to have a rectangular transparent substrate  11 , such as a glass substrate, and loop electrode groups each of which is composed of a plurality of elongated loop electrodes arranged at regular intervals so as not to overlap with one another on the transparent substrate  11  and formed by metal mesh electrodes made up of thin lines of ITO (Indium Tin Oxide), silver, copper, or the like, with the horizontal direction of the transparent substrate  11  defined as an x-axis direction (an example of a first direction), and the vertical direction of the transparent substrate  11 , which is perpendicular to the horizontal direction, defined as a y-axis direction (an example of a second direction). 
     The loop electrode groups are configured to form a double layer structure made up of, for example, an X loop electrode group  12  composed of a plurality of loop electrodes X as examples of first electrodes, and a Y loop electrode group  13  composed of a plurality of loop electrodes Y as examples of second electrodes. In this example, on a front side of the transparent substrate  11 , the plurality of loop electrodes X, each forming an elongated loop with the y-axis direction as a longitudinal direction of the loop, are arranged at regular intervals in the x-axis direction so as not to overlap with one another to form the X loop electrode group  12 . In addition, on a rear side of the transparent substrate  11 , the plurality of loop electrodes Y, each forming an elongated loop with the x-axis direction as a longitudinal direction of the loop, are arranged at regular intervals in the y-axis direction so as not to overlap with one another to form the Y loop electrode group  13 . In this example, the X loop electrode group  12  is composed of 40 loop electrodes X (X 1  to X 40 ), while the Y loop electrode group  13  is composed of 30 loop electrodes Y (Y 1  to Y 30 ). 
     Note that, in the following description, the wording “loop electrode X” will be used when the loop electrodes X 1  to X 40  need not be distinguished from one another, while, similarly, the wording “loop electrode Y” will be used when the loop electrodes Y 1  to Y 30  need not be distinguished from one another. 
     The array pitch of the loop electrodes X and the loop electrodes Y is preferably in the range of, for example, 3 to 6 mm, which approximately corresponds to the size of a contact area when a surface of the position detection sensor  10  is touched with a finger. In addition, because a greater width of a loop coil is desirable for efficient reception of a signal from the electronic pen  2 , it is desirable that an interspace between adjacent ones of the loop electrodes X and the loop electrodes Y is as narrow as possible as illustrated in  FIG.  1   . Thus, in this example, adjacent ones of the loop electrodes X and the loop electrodes Y are arranged in close proximity to each other. Accordingly, the width of the loop of each of the loop electrodes X and the loop electrodes Y measured in the array direction is arranged to be slightly smaller than the array pitch. 
     In this example, the signal processing circuitry  20 , which is connected to the position detection sensor  10 , is configured to include selection circuitry  21  for selecting one of the loop electrodes X from the X loop electrode group  12 , selection circuitry  22  for selecting one of the loop electrodes Y from the Y loop electrode group  13 , mode switch circuitry  23  for making a switch between detection of the first pointer through electromagnetic inductive coupling and detection of the second pointer through capacitive coupling, pen signal reception circuitry  24  that forms an example of first detection circuitry for detecting a position indicated by the first pointer undergoing electromagnetic inductive coupling, touch detection control circuitry  25  that forms an example of second detection circuitry for detecting a position indicated by the second pointer undergoing capacitive coupling, and process control circuitry  26  formed by a computer. 
     The selection circuitry  21  includes two multiplexers  211  and  212 , and winding start terminals (X 1   a  to X 40   a ) of the plurality of loop electrodes X (X 1  to X 40 ) are connected to the multiplexer  211 , while winding end terminals (X 1   b  to X 40   b ) thereof are connected to the other multiplexer  212 . Then, the two multiplexers  211  and  212 , in conjunction with each other, are subjected to selection control using selection control signals SEx from the process control circuitry  26 , whereby the loop electrodes X are selected one by one sequentially from the X loop electrode group  12  by the selection circuitry  21 . 
     Then, the winding start terminal of the one of the loop electrodes X in the X loop electrode group  12  which has been selected by the selection control signal SEx is selected by the multiplexer  211 , and is connected to a common terminal XA of this multiplexer  211 , while the winding end terminal of the same loop electrode X is selected by the multiplexer  212 , and is connected to a common terminal XB of this multiplexer  212 . 
     Meanwhile, the selection circuitry  22  includes two multiplexers  221  and  222 , and winding start terminals (Y 1   a  to Y 30   a ) of the plurality of loop electrodes Y (Y 1  to Y 30 ) are connected to the multiplexer  221 , while winding end terminals (Y 1   b  to Y 30   b ) thereof are connected to the other multiplexer  222 . Then, the two multiplexers  221  and  222 , in conjunction with each other, are subjected to selection control using selection control signals SEy from the process control circuitry  26 , whereby the loop electrodes Y are selected one by one sequentially from the Y loop electrode group  13  by the selection circuitry  22 . 
     Then, the winding start terminal of the one of the loop electrodes Y in the Y loop electrode group  13  which has been selected by the selection control signal SEy is selected by the multiplexer  221 , and is connected to a common terminal YA of this multiplexer  221 , while the winding end terminal of the same loop electrode Y is selected by the multiplexer  222 , and is connected to a common terminal YB of this multiplexer  222 . 
     The mode switch circuitry  23  includes change switch circuits  23 XA and  23 XB used for the loop electrodes X, and change switch circuits  23 YA and  23 YB used for the loop electrodes Y. Then, the common terminal XA of the multiplexer  211  is connected to a movable terminal of the change switch circuit  23 XA in the mode switch circuitry  23 , while the common terminal XB of the multiplexer  212  is connected to a movable terminal of the change switch circuit  23 XB in the mode switch circuitry  23 . In addition, the common terminal YA of the multiplexer  221  is connected to a movable terminal of the change switch circuit  23 YA in the mode switch circuitry  23 , while the common terminal YB of the multiplexer  222  is connected to a movable terminal of the change switch circuit  23 YB in the mode switch circuitry  23 . 
     Then, a first fixed terminal P and a second fixed terminal F of each of the change switch circuits  23 XA,  23 XB,  23 YA, and  23 YB in the mode switch circuitry  23  are connected to the pen signal reception circuitry  24  and the touch detection control circuitry  25 , respectively. 
     Then, the first fixed terminal P of the change switch circuit  23 XA in the mode switch circuitry  23  is connected to an input terminal (in the illustrated example, an inverting input terminal) of an x-side differential input amplifier  24 X in the pen signal reception circuitry  24 , while the first fixed terminal P of the change switch circuit  23 XB is connected to another input terminal (in the illustrated example, a non-inverting input terminal) of the x-side differential input amplifier  24 X. In addition, the first fixed terminal P of the change switch circuit  23 YA in the mode switch circuitry  23  is connected to an input terminal (in the illustrated example, an inverting input terminal) of a y-side differential input amplifier  24 Y in the pen signal reception circuitry  24 , while the first fixed terminal P of the change switch circuit  23 YB is connected to another input terminal (in the illustrated example, a non-inverting input terminal) of the y-side differential input amplifier  24 Y. 
     Then, although not illustrated in the figures, x-axis signal reception circuitry and y-axis signal reception circuitry are provided in stages subsequent to the x-side differential input amplifier  24 X and the y-side differential input amplifier  24 Y, respectively, in the pen signal reception circuitry  24 . The x-axis signal reception circuitry and the y-axis signal reception circuitry detect the reception levels of pen signals (signals received from the electronic pen  2 ) detected at the loop electrode X and the loop electrode Y, and supply information of the detected reception levels to the process control circuitry  26 . The process control circuitry  26  detects the coordinates (X, Y) of the position on the position detection sensor  10  indicated by the electronic pen  2  from the information supplied from the pen signal reception circuitry  24 . 
     In addition, in this example, the second fixed terminal F of the change switch circuit  23 XA and the second fixed terminal F of the change switch circuit  23 XB are connected to each other, and a junction thereof is connected to an input terminal of a touch signal detection amplifier  251  in the touch detection control circuitry  25 . Meanwhile, the second fixed terminal F of the change switch circuit  23 YA and the second fixed terminal F of the change switch circuit  23 YB are connected to each other, and a junction thereof is connected to an output terminal of a transmission output driver  252  in the touch detection control circuitry  25 . Accordingly, the loop electrode X and the loop electrode Y are shorted at both ends, and therefore, each of the loop electrodes X and Y operates as a single electrode wire. 
     In a stage previous to the transmission output driver  252 , an oscillator circuit  253  is connected thereto, and a frequency signal having a predetermined frequency f is transmitted from the oscillator circuit  253  to the position detection sensor  10  through the transmission output driver  252 . In addition, touch detection circuitry (not illustrated), which detects the level of the signal transmitted to the position detection sensor  10  through the transmission output driver  252  and received through the position detection sensor  10 , and which supplies information of the detected level of the signal to the process control circuitry  26 , is provided in a stage subsequent to the touch signal detection amplifier  251  in the touch detection control circuitry  25 . 
     The process control circuitry  26  detects the coordinates (X, Y) of the position on the position detection sensor  10  indicated by a finger, using a change in level of the signal from the touch detection control circuitry  25  caused at the position indicated by the finger. 
     The process control circuitry  26  detects the coordinates of the positions indicated by the respective pointers as mentioned above on the basis of the information received from the pen signal reception circuitry  24  and the touch detection control circuitry  25 , and also supplies timing control signals to the pen signal reception circuitry  24  and the touch detection control circuitry  25 . 
     In addition, the process control circuitry  26  supplies the selection control signals SEx to the multiplexers  211  and  212  of the selection circuitry  21  to control the loop electrodes X to be selected one by one sequentially from the X loop electrode group  12 , and also supplies the selection control signals SEy to the multiplexers  221  and  222  of the selection circuitry  22  to control the loop electrodes Y to be selected one by one sequentially from the Y loop electrode group  13 . 
     Further, the process control circuitry  26  supplies, to the mode switch circuitry  23 , a mode switch signal MD to make a switch between a condition (an electromagnetic induction mode) in which the movable terminal of each of the change switch circuits  23 XA,  23 XB,  23 YA, and  23 YB is connected to the fixed terminal P, and a condition (a capacitive coupling mode) in which the movable terminal of each of the change switch circuits  23 XA,  23 XB,  23 YA, and  23 YB is connected to the fixed terminal F. 
     In this embodiment, using the mode switch signal MD, the process control circuitry  26  controls the mode switch circuitry  23  to alternate between the fixed terminal P and the fixed terminal F such that each of the fixed terminal P and the fixed terminal F is selected for a period having a predetermined time length, to cause the position detection device  1  to make switching between the electromagnetic induction mode and the capacitive coupling mode in a time division manner. 
     Operation of Position Detection Device  1  According to First Embodiment 
     In this embodiment, the process control circuitry  26 , using the mode switch signal MD, controls the mode switch circuitry  23  to enter a state in which the movable terminal of each of the change switch circuits  23 XA,  23 XB,  23 YA, and  23 YB is connected to the fixed terminal P in the period having the predetermined time length, and controls the pen signal reception circuitry  24  to be driven to make a switch to the electromagnetic induction mode. Then, in this period of the electromagnetic induction mode, the process control circuitry  26  controls the multiplexers  211  and  212  of the selection circuitry  21  to select the loop electrodes X one by one from the X loop electrode group  12  such that all the loop electrodes X are selected sequentially, and controls the multiplexers  221  and  222  of the selection circuitry  22  to select the loop electrodes Y one by one from the Y loop electrode group  13  such that all the loop electrodes Y are selected sequentially. 
     As a result, in the position detection device  1  in the state of this electromagnetic induction mode, respective ends of the one of the loop electrodes X which is selected by the selection circuitry  21  are connected to the inverting input terminal and the non-inverting input terminal of the x-side differential input amplifier  24 X in the pen signal reception circuitry  24  as illustrated in  FIG.  2   . Similarly, respective ends of the one of the loop electrodes Y which is selected by the selection circuitry  22  are connected to the inverting input terminal and the non-inverting input terminal of the y-side differential input amplifier  24 Y in the pen signal reception circuitry  24 . 
     At this time, if a position is indicated by the electronic pen  2  on the position detection sensor  10 , induced electric currents induced in the loop electrode X and the loop electrode Y in response to the signal from the electronic pen  2  are amplified in the x-side differential input amplifier  24 X and the y-side differential input amplifier  24 Y, and are supplied to the x-axis signal reception circuitry and the y-axis signal reception circuitry in the subsequent stages, and the levels thereof are detected. 
     The process control circuitry  26  detects the coordinates (X, Y) of the position indicated by the electronic pen  2  on the position detection sensor on the basis of timing of switching of the multiplexers  211  and  212  of the selection circuitry  21  and the multiplexers  221  and  222  of the selection circuitry  22  using the selection control signals SEx and the selection control signals SEy, and an output of reception detection of the signal transmitted from the electronic pen  2  from the pen signal reception circuitry  24 , as described above. 
     Then, in this embodiment, once the period of the electromagnetic induction mode ends, the process control circuitry  26 , using the mode switch signal MD, causes the movable terminal of each of the change switch circuits  23 XA,  23 XB,  23 YA, and  23 YB in the mode switch circuitry  23  to be connected to the fixed terminal F, and controls the touch detection control circuitry  25  to be driven to make a switch to the capacitive coupling mode. Then, in the period of this capacitive coupling mode also, the process control circuitry  26 , using the selection control signals SEx and the selection control signals SEy, controls the selection circuitry  21  and the selection circuitry  22  to make switches such that the loop electrodes X are selected one by one sequentially from the X loop electrode group  12 , and the loop electrodes Y are selected one by one sequentially from the Y loop electrode group  13 . 
     As illustrated in  FIG.  3   , in the position detection device  1  in this capacitive coupling mode, a signal having the predetermined frequency is sequentially supplied from the oscillator circuit  253  through the transmission output driver  252  of the touch detection control circuitry  25  to each one of the loop electrodes Y which is selected by the selection circuitry  22  and acts as a single electrode wire with the common terminal YA, to which the winding start terminal is connected, and the common terminal YB, to which the winding end terminal is connected, connected to each other. In addition, each one of the loop electrodes X which is selected by the selection circuitry  21  and acts as a single electrode wire with the common terminal XA, to which the winding start terminal is connected, and the common terminal XB, to which the winding end terminal is connected, connected to each other is connected to the inverting input terminal of the touch signal detection amplifier  251  in the touch detection control circuitry  25 . 
     At this time, the signal transmitted to the shorted loop electrode Y through the transmission output driver  252  is received by the shorted loop electrode X, and the reception level thereof is supplied to the touch signal detection amplifier  251 . When the position detection sensor  10  is being touched by a finger  3 , a part of the signal transmitted to the loop electrode Y is caused to pass through the finger  3  and a human body, resulting in a reduction in a signal to be transferred from the loop electrode Y at the position touched by the finger to the loop electrode X. The process control circuitry  26  detects the coordinates of the position touched by the finger by detecting a change in level of the reception signal from the touch detection control circuitry  25 . 
     Then, in this embodiment, once the period of the capacitive coupling mode ends, the process control circuitry  26  makes a switch to the electromagnetic induction mode using the mode switch signal MD as described above. Thereafter, the electromagnetic induction mode and the capacitive coupling mode are similarly repeated in the time division manner. 
     As described above, the position detection device  1  according to the above-described first embodiment is able to detect the coordinates of the position indicated by the electronic pen  2  by an electromagnetic induction method, and is also able to detect the coordinates of the position indicated by the finger  3  by a capacitive coupling method, using the position detection sensor  10  in which the X loop electrode group  12  and the Y loop electrode group  13  are formed. 
     In addition, in the position detection device  1  according to the first embodiment, instead of linear electrodes, the X loop electrode group  12  and the Y loop electrode group  13  are formed in the position detection sensor  10 , and this eliminates the need to form loop electrodes by connecting end portions of the linear electrodes. This allows the position detection device  1  to have a simple structure with use of the selection circuitry  21 , which selects each of the loop electrodes X from the X loop electrode group  12 , the selection circuitry  22 , which selects each of the loop electrodes Y from the Y loop electrode group  13 , and the mode switch circuitry  23 . 
     Second Embodiment 
     In the position detection device  1  according to the above-described first embodiment, the selection circuitry  21  and the selection circuitry  22  are configured to select the loop electrodes X and the loop electrodes Y, respectively, one by one sequentially in both the electromagnetic induction mode and the capacitive coupling mode. However, in the electromagnetic induction mode, a plurality of adjacent loop electrodes may be simultaneously selected from each of the X loop electrode group  12  and the Y loop electrode group  13  to equivalently form a loop coil having a large width, to enable more efficient detection of the signal from the electronic pen  2 . A second embodiment described below corresponds to such a configuration. Because an operation of the capacitive coupling mode remains the same as in the first embodiment, an operation of the electromagnetic induction mode will mainly be described in the following description. 
     First Example of Second Embodiment 
       FIGS.  4  to  7    are diagrams for explaining an example configuration of a position detection device  1 A according to the second embodiment, which is configured to simultaneously select two adjacent loop electrodes X and two adjacent loop electrodes Y. 
       FIG.  4    is a diagram illustrating the example configuration of the position detection device  1 A according to the second embodiment. As illustrated in  FIG.  4   , in the position detection device  1 A according to the second embodiment, selection circuitry  21 A and selection circuitry  22 A are provided in place of the selection circuitry  21  and the selection circuitry  22  in the position detection device  1  according to the first embodiment, and process control circuitry  26 A is provided in place of the process control circuitry  26 . The position detection device  1 A is otherwise similar in structure to the position detection device  1  according to the first embodiment. In  FIG.  4   , components that have their equivalents in the position detection device  1  according to the above-described first embodiment are denoted by the same reference symbols as those of their equivalents, and descriptions thereof are omitted. 
     In the second embodiment, the selection circuitry  21 A includes a selection switch  211 A and a selection switch  212 A. As illustrated in  FIG.  4   , each of the selection switch  211 A and the selection switch  212 A includes the same number of switches as that of loop electrodes X (X 1  to X 40 ), and each of winding start terminals X 1   a  to X 40   a  of the loop electrodes X (X 1  to X 40 ) is connected to one end of the corresponding switch in the selection switch  211 A, while each of winding end terminals X 1   b  to X 40   b  thereof is connected to one end of the corresponding switch in the selection switch  212 A. 
     In addition, ends of all the switches in the selection switch  211 A on an opposite side are connected to each other, and are connected to a common terminal XA′ of the selection switch  211 A. Similarly, ends of all the switches in the selection switch  212 A on an opposite side are connected to each other, and are connected to a common terminal XB′ of the selection switch  212 A. The common terminal XA′ of the selection switch  211 A is connected to a movable terminal of a change switch circuit  23 XA in mode switch circuitry  23 , while the common terminal XB′ of the selection switch  212 A is connected to a movable terminal of a change switch circuit  23 XB in the mode switch circuitry  23 . 
     Then, in a first example of the second embodiment, in the electromagnetic induction mode, the selection switch  211 A and the selection switch  212 A are controlled, through selection control signals SEMx from the process control circuitry  26 A, to simultaneously select two adjacent ones of the loop electrodes X from the X loop electrode group  12  such that the two loop electrodes X selected are sequentially shifted one by one. 
       FIG.  5    is a diagram for explaining selection control for selecting a plurality of switches in the selection switches  211 A and  212 A in the electromagnetic induction mode in the position detection device  1 A according to the first example of the second embodiment.  FIG.  5    illustrates how the switches to which the loop electrodes X 1  to X 40  in the X loop electrode group  12  are respectively connected are turned on and off in the selection switches  211 A and  212 A as time passes, and “1” represents turning on while “0” represents turning off. In the electromagnetic induction mode, the selection control as illustrated in  FIG.  5    is repeatedly performed through the selection control signals SEMx and SEMy. 
     Specifically, the selection switch  211 A and the selection switch  212 A of the selection circuitry  21 A select the same, two adjacent loop electrodes X sequentially, and, at first, turn on the two switches to which the loop electrodes X 1  and X 2  are connected, and connect these loop electrodes X 1  and X 2  to the common terminals XA′ and XB′. Next, the two switches to which the loop electrodes X 2  and X 3  are connected are turned on, and these loop electrodes X 2  and X 3  are connected to the common terminals XA′ and XB′. Further, two loop electrodes X sequentially selected such that the loop electrodes X selected are shifted one by one, such as the loop electrodes X 3  and X 4 , the loop electrodes X 4  and X 5 , the loop electrodes X 5  and X 6 , and so on, are connected to the common terminals XA′ and XB′. 
     The common terminals XA′ and XB′ are connected to an x-side differential input amplifier  24 X in pen signal reception circuitry  24  through fixed terminals P in the mode switch circuitry  23 , and therefore, in the pen signal reception circuitry  24 , the reception level of a pen signal is detected with respect to the two loop electrodes X selected sequentially. 
     As illustrated in  FIG.  6   , when two adjacent loop electrodes X are simultaneously selected as described above, two coils are connected in parallel, allowing a supply to be provided to the x-side differential input amplifier  24 X. In this case, assuming that electric currents induced in two adjacent loop electrodes Xn and Xn+1 (n=1, 2, . . . , 39) through electromagnetic inductive coupling with the electronic pen  2  are denoted by i 1  and i 2 , respectively, an output α(i 1 +i 2 ), which corresponds to a sum of the electric currents induced in the two loop electrodes Xn and Xn+1, is obtained in the x-side differential input amplifier  24 X. 
     Detecting the signals from the electronic pen  2  with the selection switch  211 A and the selection switch  212 A being controlled to select two adjacent loop electrodes X sequentially in the order illustrated in  FIG.  5    as described above is equivalent to a well-known detection method of selecting loop coils  14  disposed so as to overlap with one another in due order employing the electromagnetic induction method as illustrated in  FIG.  7   . In the case of this example, a loop coil having a width equal to twice the array pitch of the loop electrodes can be formed by selecting two adjacent loop electrodes simultaneously. 
     While the foregoing description has been made with respect to the selection circuitry  21 A for the X loop electrode group  12 , which is used to obtain an x-coordinate, a similar configuration can be implemented with respect to the selection circuitry  22 A for the Y loop electrode group  13 , which is used to obtain a y-coordinate. 
     That is, in the second embodiment, the selection circuitry  22 A includes a selection switch  221 A and a selection switch  222 A, each of which includes the same number of switches as that of loop electrodes Y (Y 1  to Y 30 ), and as illustrated in  FIG.  4   , each of winding start terminals Y 1   a  to Y 30   a  of the loop electrodes Y (Y 1  to Y 30 ) is connected to one end of the corresponding switch in the selection switch  221 A, while each of winding end terminals Y 1   b  to Y 30   b  thereof is connected to one end of the corresponding switch in the selection switch  222 A. 
     In addition, ends of all the switches in the selection switch  221 A on an opposite side are connected to each other, and are connected to a common terminal YA′ of the selection switch  221 A, while ends of all the switches in the selection switch  222 A on an opposite side are connected to each other, and are connected to a common terminal YB′ of the selection switch  222 A. Then, the common terminal YA′ of the selection switch  221 A is connected to a movable terminal of a change switch circuit  23 YA in the mode switch circuitry  23 , while the common terminal YB′ of the selection switch  222 A is connected to a movable terminal of a change switch circuit  23 YB in the mode switch circuitry  23 . 
     Then, in the first example of the second embodiment, in the electromagnetic induction mode, the selection switch  221 A and the selection switch  222 A are controlled, through selection control signals SEMy from the process control circuitry  26 A, to simultaneously select two adjacent ones of the loop electrodes Y such that the two loop electrodes Y selected are sequentially shifted one by one, in a manner similar to that in which the above-described control is performed to sequentially select two adjacent ones of the loop electrodes X from the X loop electrode group  12 . 
     Accordingly, an operation similar to the operation illustrated in  FIG.  6    is performed with respect to the loop electrodes Y as well, and an output α(i 1 +i 2 ), which corresponds to a sum of electric currents induced in two loop electrodes Ym and Ym+1 (m=1, 2, . . . , 29), is obtained in a y-side differential input amplifier  24 Y in the pen signal reception circuitry  24 . In addition, a detection method employed for the Y loop electrode group  13  is also equivalent to the well-known detection method of selecting loop coils disposed so as to overlap with one another in due order employing the electromagnetic induction method. 
     Note that, as mentioned above, also in the second embodiment, the selection switch  211 A and the selection switch  212 A, or the selection switch  221 A and the selection switch  222 A, are controlled to select the loop electrodes X or the loop electrodes Y, respectively, one by one in the capacitive coupling mode. Accordingly, in the capacitive coupling mode, SECx and SECy for causing the switches to be turned on one by one are supplied from the process control circuitry  26 A to the selection switch  211 A and the selection switch  212 A, and the selection switch  221 A and the selection switch  222 A, respectively. 
     Second Example of Second Embodiment 
     In the above-described first example, in the electromagnetic induction mode, a plurality of (in this example, two) adjacent loop electrodes X and a plurality of (in this example, two) adjacent loop electrodes Y are simultaneously selected, but more than two adjacent loop electrodes X and loop electrodes Y may be simultaneously selected. A second example corresponds to an example of such a case, and a case where three adjacent loop electrodes are simultaneously selected will be described below. 
     Also, in the case of the second example, the configuration of the position detection device  1 A as illustrated in  FIG.  4    as it is used as the configuration of the position detection device. The position detection device according to the second example is different from the position detection device according to the first example in the selection control signals SEMx and SEMy supplied from the process control circuitry  26 A to the two selection switches  211 A and  212 A of the selection circuitry  21 A and the two selection switches  221 A and  222 A of the selection circuitry  22 A, respectively, in the electromagnetic induction mode. 
       FIG.  8    is a diagram for explaining selection control for selecting a plurality of switches in the selection switches  211 A and  212 A in the electromagnetic induction mode in the position detection device  1 A according to the second example of the second embodiment. 
     In this example, the selection switch  211 A and the selection switch  212 A of the selection circuitry  21 A select the same, three adjacent loop electrodes X sequentially, and, at first, turn on the three switches to which the loop electrodes X 1 , X 2 , and X 3  are connected, and connect these loop electrodes X 1 , X 2 , and X 3  to the common terminals XA′ and XB′. Next, the three switches to which the loop electrodes X 2 , X 3 , and X 4  are connected are turned on, and these loop electrodes X 2 , X 3 , and X 4  are connected to the common terminals XA′ and XB′. Further, three loop electrodes X sequentially selected such that the loop electrodes X selected are shifted one by one, such as the loop electrodes X 3 , X 4 , and X 5 , the loop electrodes X 4 , X 5 , and X 6 , the loop electrodes X 5 , X 6 , and X 7 , and so on, are connected to the common terminals XA′ and XB′. 
     As illustrated in  FIG.  9   , when three adjacent loop electrodes X are simultaneously selected as described above, three loop electrodes X (coils) are connected in parallel, allowing a supply to be provided to the x-side differential input amplifier  24 X. In this case, assuming that electric currents induced in three adjacent loop electrodes Xn, Xn+1, and Xn+2 (n=1, 2, . . . , 38) through electromagnetic inductive coupling with the electronic pen  2  are denoted by i 1 , i 2 , and i 3 , respectively, an output α(i 1 +i 2 +i 3 ), which corresponds to a sum of the electric currents induced in the three loop electrodes Xn, Xn+1, and Xn+2, is obtained in the x-side differential input amplifier  24 X. 
     Detecting the signals from the electronic pen  2  with the selection switch  211 A and the selection switch  212 A being controlled to select three adjacent loop electrodes X sequentially in the order illustrated in  FIG.  8    as described above is equivalent to a well-known detection method of selecting loop coils  15  disposed so as to overlap with one another in due order employing the electromagnetic induction method as illustrated in  FIG.  10   . In the case of this example, a loop coil having a width equal to three times the array pitch of the loop electrodes X can be formed by selecting three adjacent loop electrodes simultaneously. 
     A similar configuration can be implemented with respect to the selection circuitry  22 A for the Y loop electrode group  13 , which is used to obtain a y-coordinate, and in this case, three coils are connected in parallel, allowing a supply to be provided to the y-side differential input amplifier  24 Y. 
     Third Embodiment 
     In the position detection device  1 A according to the above-described second embodiment, in the electromagnetic induction mode, the selection circuitry  21 A and the selection circuitry  22 A are controlled to select a plurality of loop electrodes X and a plurality of loop electrodes Y, respectively, to connect them in parallel as illustrated in  FIGS.  6  and  9   , but the selection circuitries may alternatively be configured to connect loop electrodes (coils) in series when a plurality of adjacent loop electrodes X and a plurality of adjacent loop electrodes Y have been selected. A third embodiment corresponds to an example of such a case. 
       FIG.  11    is a diagram for explaining an example configuration of a position detection device  1 B according to a third embodiment. The following description focuses on an operation of the position detection device  1 B according to the third embodiment in the electromagnetic induction mode. 
     As illustrated in  FIG.  11   , in the position detection device  1 B according to the third embodiment, selection circuitry  21 B and selection circuitry  22 B are provided in place of the selection circuitry  21  and the selection circuitry  22  in the position detection device  1  according to the first embodiment, and process control circuitry  26 B is provided in place of the process control circuitry  26 . The position detection device  1 B is otherwise similar in structure to the position detection device  1  according to the first embodiment. In  FIG.  11   , components that have their equivalents in the position detection device  1  according to the above-described first embodiment are denoted by the same reference symbols as those of their equivalents, and descriptions thereof are omitted. Note that, in  FIG.  11   , illustration of pen signal reception circuitry  24  and touch detection control circuitry  25  is omitted. 
     In the third embodiment, the selection circuitry  21 B includes multiplexers  211 B and  212 B, which are similar in structure to the multiplexers  211  and  212  according to the first embodiment, and a plurality of 3-terminal switches, in this example, 39 3-terminal switches SX 1  to SX 39 , the number of which is smaller than the number of loop electrodes X (X 1  to X 40 ) by one. Each 3-terminal switch is a switch that includes three terminals, i.e., a first terminal, a second terminal, and a third terminal, and which can be configured to connect two freely-selected terminals among the three terminals to each other through a configuration control signal. 
     Then, each of winding end terminals X 1   b  to X 39   b  of the loop electrodes X (X 1  to X 39 ) is connected to the first terminal of a corresponding one of the 3-terminal switches SX 1  to SX 39 , while each of winding start terminals X 2   a  to X 40   a  of the loop electrodes X (X 2  to X 40 ) is connected to the second terminal of a corresponding one of the 3-terminal switches SX 1  to SX 39 . In addition, the third terminal of each of the 3-terminal switches SX 1  to SX 39  is connected to the multiplexers  211 B and  212 B. Notice that a winding start terminal X 1   a  of the loop electrode X 1  is directly connected to the multiplexer  212 B, while a winding end terminal X 40   b  of the loop electrode X 40  is directly connected to the multiplexer  211 B. 
     Then, in this embodiment, in addition to sending a mode switch signal MD, the process control circuitry  26 B sends, to each of the 3-terminal switches SX 1  to SX 39 , a configuration control signal CTx for controlling the configuration thereof, and sends a selection control signal SExA and a selection control signal SExB to the multiplexer  211 B and the multiplexer  212 B, respectively. 
     For example, in the case where two adjacent loop electrodes X are to be connected in series, at first, the 3-terminal switch SX 1 , to the first terminal of which the winding end terminal X 1   b  of the loop electrode X 1  is connected, is controlled and configured to connect the first terminal and the second terminal to each other, and the 3-terminal switch SX 2 , to the first terminal of which the winding end terminal X 2   b  of the adjacent loop electrode X 2  is connected, is controlled and configured to connect the first terminal and the third terminal to each other. In addition, the multiplexer  211 B is controlled to select the 3-terminal switch SX 2 , and the multiplexer  212 B is controlled to select the winding start terminal X 1   a  of the loop electrode X 1 . 
     Next, the 3-terminal switch SX 1  is controlled and configured to connect the first terminal and the third terminal to each other, the 3-terminal switch SX 2  adjacent thereto is controlled and configured to connect the first terminal and the second terminal to each other, and the 3-terminal switch SX 3  adjacent thereto is controlled and configured to connect the first terminal and the third terminal to each other. In addition, the multiplexer  211 B is controlled to select the 3-terminal switch SX 3 , in which the first terminal and the third terminal are connected to each other, and the multiplexer  212 B is controlled to select the 3-terminal switch SX 1 , in which, similarly, the first terminal and the third terminal are connected to each other. 
     Thereafter, sets of three adjacent 3-terminal switches SXn to SXn+2 are sequentially subjected to configuration control such that the three adjacent 3-terminal switches are sequentially shifted by one 3-terminal switch. Of the three adjacent 3-terminal switches SXn to SXn+2, each of the 3-terminal switches SXn and SXn+2 at both ends is controlled and configured to connect the first terminal to the third terminal, and the 3-terminal switch SXn+1 in the middle is controlled and configured to connect the first terminal to the second terminal. In addition, the multiplexer  211 B and the multiplexer  212 B are controlled to select the 3-terminal switch SXn+2 and the 3-terminal switch SXn, respectively, at both ends. 
     When the selection control of the selection circuitry  21 B is performed in the above-described manner, two loop electrodes X (coils) are connected in series as illustrated in  FIG.  12   , allowing a supply to be provided to an x-side differential input amplifier  24 X, and an output corresponding to a sum of electric currents induced in the two loop electrodes X is obtained in the x-side differential input amplifier  24 X. 
     Note that this disclosure is not limited to the case where two loop electrodes are connected in series, and that control may be performed such that three adjacent loop electrodes X are connected in series while the three loop electrodes X that make a set are sequentially shifted one by one. In the case of three or more loop electrodes X, the 3-terminal switches to which the loop electrodes X are connected are controlled such that the winding start terminals of the loop electrodes X at both ends are connected to the multiplexers  211 B and  212 B, while the winding end terminal and the winding start terminal of adjacent ones of the loop electrodes X in the middle are connected to each other. 
     While the foregoing description has been made with respect to the X loop electrode group  12 , a similar configuration can be implemented with respect to the selection circuitry  22 B for the Y loop electrode group  13  so that similar control can be performed such that a plurality of loop electrodes Y are sequentially connected in series. In this case, the selection circuitry  22 B includes multiplexers  221 B and  222 B, which are similar in structure to the multiplexers  221  and  222  according to the first embodiment, and a plurality of 3-terminal switches, in this example,  29  3-terminal switches SY 1  to SY 29 , the number of which is smaller than the number of loop electrodes Y (Y 1  to Y 30 ) by one. 
     Then, the multiplexers  221 B and  222 B in the selection circuitry  22 B and the 3-terminal switches SY 1  to SY 29  can be controlled through selection control signals SEyA and SEyB and configuration control signals CTy from the process control circuitry  26 B to sequentially select a plurality of adjacent loop electrodes Y and connect them in series in a manner similar to that for the X loop electrode group  12 . 
     Note that, in the capacitive coupling mode according to the third embodiment, the loop electrodes X are selected one by one by the selection circuitry  21 B, and the loop electrodes Y are selected one by one by the selection circuitry  22 B as in the second embodiment. 
     Other Embodiments 
     In the position detection sensor  10  according to each of the above-described embodiments, the loop electrodes X and the loop electrodes Y are formed on the transparent substrate  11  by electrically conductive materials that can be made substantially transparent, such as metal mesh electrodes made up of thin lines of ITO, silver, copper, or the like. Accordingly, each of the lines of the electrodes of the position detection sensor  10  is formed as a pattern having a predetermined width, such as, for example, approximately one millimeter. When the position detection sensor that uses such electrode lines is used for a touch detection operation, inside portions of the loop electrodes X and the loop electrodes Y in the width direction form electrical cavities, reducing a capacitance in relation to a human body, such as a finger, at a middle portion of each of the loop electrodes X and the loop electrodes Y, making it difficult to accurately determine a position indicated by a finger. 
     To solve such a problem, projecting portions that project from the patterns of the electrode lines of the loop electrodes X and the loop electrodes Y inward in the width direction of each of the loop electrodes X and in the width direction of each of the loop electrodes Y may be formed.  FIGS.  13 A and  13 B  illustrate examples of the projecting portions that project from the patterns of the electrode lines of the loop electrodes X and the loop electrodes Y inward in the width direction of each of the loop electrodes X and in the width direction of each of the loop electrodes Y. 
     As illustrated in  FIGS.  13 A and  13 B , in a position detection sensor, the loop electrodes X and the loop electrodes Y are arranged to cross at right angles, and therefore, a rectangular cavity region  16  is formed within the width of each loop electrode X and the width of each loop electrode Y. 
     In the example of  FIG.  13 A , two projecting portions  17   a  and  17   b , which are opposite to each other and which are arranged to project from each of the electrode line patterns of the loop electrodes X in such directions as to intersect the electrode line pattern at right angles and at such positions as to extend toward a center of the rectangular cavity region  16 , are formed. In addition, two projecting portions  18   a  and  18   b , which are opposite to each other and which are arranged to project from each of the electrode line patterns of the loop electrodes Y in such directions as to intersect the electrode line pattern at right angles at a middle position of the rectangular cavity region  16 , are formed. 
     Meanwhile, in the example of  FIG.  13 B , projecting portions  17   c  and  17   d , which are arranged to project in such directions as to intersect each of the electrode line patterns of the loop electrodes X at right angles, are formed, but in this example, the projecting portions  17   c  and  17   d  are not opposite to each other, and are each arranged to extend toward a position displaced from the center of the rectangular cavity region  16 . Similarly, projecting portions  18   c  and  18   d , which are arranged to project in such directions as to intersect each of the electrode line patterns of the loop electrodes Y at right angles, are formed, but in this example, the projecting portions  18   c  and  18   d  are not opposite to each other, and are each arranged to extend toward a position displaced from the center of the rectangular cavity region  16 . 
     According to the position detection sensors in which the electrode patterns are formed as illustrated in  FIGS.  13 A and  13 B  mentioned above, a finger touching any rectangular cavity region  16  essentially touches the corresponding loop electrode X and the corresponding loop electrode Y since the projecting portions  17   a  and  17   b  and the projecting portions  18   a  and  18   b , or the projecting portions  17   c  and  17   d  and the projecting portions  18   c  and  18   d , exist in the cavity region  16 , enabling the finger touch to be detected more easily. 
     Even when the projecting portions  17   a  and  17   b  and the projecting portions  18   a  and  18   b , or the projecting portions  17   c  and  17   d  and the projecting portions  18   c  and  18   d , are provided inside of the loop electrodes X and Y as described above, the projecting portions  17   a  and  17   b  and the projecting portions  18   a  and  18   b , or the projecting portions  17   c  and  17   d  and the projecting portions  18   c  and  18   d , hardly affect a reception of a magnetic field signal from the electronic pen during an operation of receiving a pen signal, because a magnetic field radiating from the electronic pen is radiated over a sufficiently large area compared to the line width of the projecting portions. 
     Other Embodiments or Modifications 
     In the above-described embodiment, in the capacitive coupling mode, each of the loop electrodes X and the loop electrodes Y is shorted with the winding start terminal and the winding end terminal connected to each other, but one of the winding start terminal and the winding end terminal may be made open (an open terminal), and the other of the winding start terminal and the winding end terminal may be made a terminal portion connected to the touch detection control circuitry  25 . 
     In addition, in the above-described embodiment, the position detection sensor  10  is formed as a transparent sensor having the transparent substrate  11 , and the loop electrodes X and the loop electrodes Y formed by the metal mesh electrodes made up of the thin lines of ITO, silver, copper, or the like, but it is needless to say that the position detection sensor  10  may alternatively be formed as a non-transparent sensor for applications in which the position detection sensor  10  is not disposed on a display screen of a display device. 
     In addition, in the above-described embodiment, differential amplifiers are used in amplification circuits for an x-side input and a y-side input of the pen signal reception circuitry  24 , but alternatively, one end of each of the loop electrodes X and the loop electrodes Y may be connected to a fixed potential with the other end being applied to a single-input amplifier. 
     In addition, in each of the above-described embodiments, the position detection device  1 ,  1 A, or  1 B is configured to switch the mode between the electromagnetic induction mode and the capacitive coupling mode in the time division manner using the mode switch signal MD from the process control circuitry  26 ,  26 A, or  26 B. Note, however, that the switching between the electromagnetic induction mode and the capacitive coupling mode may naturally be manually carried out by a user. In this case, the position detection device is provided with a change switch or a push button switch on which a switching operation can be performed by the user, and, for example, the process control circuitry is configured to switch the mode between the electromagnetic induction mode and the capacitive coupling mode according to the switch state of the change switch or the push button switch. 
     In addition, the position detection device may be configured to switch the mode to the electromagnetic induction mode when the position detection device is in such a condition as to receive a signal from the electronic pen through the position detection sensor, and switch the mode to the capacitive coupling mode when the position detection device is not in such a condition as to receive a signal from the electronic pen through the position detection sensor. 
     In addition, each of the electronic pen and the position detection device may be provided with, for example, a short-range wireless communication circuit compliant with the Bluetooth (registered trademark) standard, and the position detection device may be configured to switch the mode to the electromagnetic induction mode when the short-range wireless communication circuit of the position detection device has received a signal from the electronic pen, and switch the mode to the capacitive coupling mode when the short-range wireless communication circuit of the position detection device is not in such a condition as to receive a signal from the electronic pen. 
     In addition, in each of the above-described embodiments, the second pointer to be detected in the capacitive coupling mode is assumed to be a finger of a human body, but the second pointer may alternatively be a passive capacitive electronic pen. Further, the second pointer may alternatively be an active capacitive electronic pen. In the case where the active capacitive electronic pen is used, circuitry configured to receive a signal from the active capacitive electronic pen with respect to each of a loop electrode X and a loop electrode Y and detect the level thereof is provided in place of the touch detection control circuitry  25 . 
     In addition, in each of the above-described embodiments, in the electromagnetic induction mode, the position indicated by the electronic pen  2  is detected by receiving the signal from the electronic pen  2  provided with an oscillator circuit. Note, however, that this is not essential to this disclosure, and that an electronic pen provided with a resonant circuit including a coil and a capacitor may be used, and the position detection device may be configured to, in the electromagnetic induction mode, transmit an alternating-current signal to the electronic pen through electromagnetic inductive coupling, and receive a signal fed back through the resonant circuit of the electronic pen, to detect the position indicated by the electronic pen. In this case, the X loop electrode group  12  and the Y loop electrode group  13  may be used as a means for transmitting the alternating-current signal to the electronic pen, or alternatively, an additional loop coil may be provided for this transmission. 
     DESCRIPTION OF REFERENCE SYMBOLS 
       1 ,  1 A,  1 B . . . Position detection device,  2  . . . Electronic pen,  3  . . . Finger,  10  . . . Position detection sensor,  11  . . . Transparent substrate,  12  . . . X loop electrode group,  13  . . . Y loop electrode group,  17   a ,  17   b ,  17   c ,  17   d  . . . Projecting portion,  18   a ,  18   b ,  18   c ,  18   d  . . . Projecting portion,  21 ,  21 A,  21 B . . . Selection circuitry for X loop electrodes,  22 ,  22 A,  22 B . . . Selection circuitry for Y loop electrodes,  23  . . . Mode switch circuitry,  24  . . . Pen signal reception circuitry,  25  . . . Touch detection control circuitry