Capacitive touch pad apparatus

The disclosure of Japanese Patent-Application No. 2008-237320, which was filed on Sep. 17, 2008, is incorporated herein by reference.

1. Field of the Invention

The present invention relates to a capacitive touch pad apparatus. More particularly, the present invention relates to a capacitive touch pad apparatus for sensing a finger contact with an insulating sheet covering an electrode by noticing a change in capacitance between the electrode and the finger.

2. Description of the Related Art

According to one example of this type of an apparatus, a plurality of switch electrodes are placed on a panel and are further covered by a glass plate (or an acrylic plate). When a finger of an operator contacts the glass plate, a capacitance of a switch electrode positioned on a bottom side of a contact portion increases. A manner of manipulating on the panel is determined by noticing such a change in capacitance, and a process depending upon a determination result is executed by a CPU.

However, in the above-described apparatus, a lead pattern connected to a switch electrode is formed near another switch electrode. Thus, a contact by the finger of an operator increases a capacitance of the lead pattern, and there is a possibility that the manner of manipulating may be erroneously determined.

A capacitive touch pad apparatus according to the present invention comprises: a plurality of first electrodes formed on a substrate; a plurality of second electrodes formed on said substrate in such a manner as to surround the plurality of first electrodes; a plurality of first conductive lines which extend over the substrate in such a manner as to sandwich at least one of the plurality of second electrodes so as to be connected to the plurality of first electrodes, respectively; and an insulating sheet, having one primary surface exposed to outside, for covering the plurality of first electrodes, the plurality of second electrodes, and the plurality of first conductive lines.

Preferably, further comprised is a plurality of second conductive lines which extend over the substrate so as to be connected to the plurality of second electrodes, respectively, wherein the insulating sheet father covers the plurality of second conductive lines.

More preferably, further comprised are: a detector for detecting a change in capacitance of each of the plurality of first electrodes and the plurality of second electrodes; and a processor for executing a process that is referred to a plurality of detection results by the detector.

Preferably, the detector detects a change in the capacitance by comparing a change amount of an input impedance indicating a numerical value corresponding to the capacitance with a threshold value.

Preferably, the detector detects a change in the capacitance by comparing an input impedance indicating a numerical value corresponding to the capacitance with a reference impedance.

Preferably, the detection results of the detector indicate one of active and negative, and the processor includes a determiner for determining whether or not both detection results, out of a plurality of detection results by the detector, corresponding to the plurality of first electrodes are active, a first predetermined process executor for executing a first predetermined process when a determination result of the determiner is affirmative, and a second predetermined process executor for executing a second predetermined process when the determination result by the determiner is negative.

Preferably, the plurality of second electrodes are formed on the substrate in such a manner as to depict a ring, and the processor includes an assigner for assigning a common parameter to the plurality of second electrodes, and an updater for updating a value of the parameter assigned by the assigner by responding to a detection result, out of the plurality of detection results by the detector, corresponding to the plurality of second electrodes.

More preferably, further comprised is a prohibiter for prohibiting a determining process of the determiner when the number of active detection results, out of the plurality of detection results by the detector, exceeds the number of the first electrodes.

The above described features and advantages of the present invention will become more apparent from the following detailed description of the embodiment when taken in conjunction with the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention;

FIG. 2 is an illustrative view showing one example of a hierarchical structure of a menu applied to the embodiment in FIG. 1 ;

FIG. 3(A) is an illustrative view showing one portion of an appearance of the embodiment in FIG. 1 ;

FIG. 3(B) is an illustrative view showing another portion of the appearance of the embodiment in FIG. 1 ;

FIG. 4(A) is an illustrative view showing one example of a menu displayed on a screen;

FIG. 4(B) is an illustrative view showing another example of the menu displayed on the screen;

FIG. 4(C) is an illustrative view showing still another example of the menu displayed on the screen;

FIG. 4(D) is an illustrative view showing yet still another example of the menu displayed on the screen;

FIG. 5(A) is an illustrative view showing another example of the menu displayed on the screen;

FIG. 5(B) is an illustrative view showing still another example of the menu displayed on the screen;

FIG. 6(A) is an illustrative view showing yet still another example of the menu displayed on the screen;

FIG. 6(B) is an illustrative view showing another example of the menu displayed on the screen;

FIG. 7(A) is an illustrative view showing still another example of the menu displayed on the screen;

FIG. 7(B) is an illustrative view showing yet still another example of the menu displayed on the screen;

FIG. 8 is an illustrative view showing one example of a printed-circuit board applied to the embodiment in FIG. 1 ;

FIG. 9 is a block diagram showing one example of a configuration of a manipulation sensing circuit applied to the embodiment in FIG. 1 ;

FIG. 10 is an illustrative view showing one portion of an operation of a decoder applied to the embodiment in FIG. 9 ;

FIG. 11(A) is an illustrative view showing one portion of an operation of the decoder in a state that a finger does not contact a touch pad;

FIG. 11(B) is an illustrative view showing one portion of an operation of the decoder in a state that the finger contacts the touch pad;

FIG. 12 is a flowchart showing one portion of an operation of a CPU applied to the embodiment in FIG. 1 ;

FIG. 13 is a flowchart showing another portion of the operation of the CPU applied to the embodiment in FIG. 1 ; and

FIG. 14 is an illustrative view showing one example of a printed-circuit board applied to another embodiment.

With reference to FIG. 1 , a photo viewer 10 according to this embodiment includes a capacitive touch pad (hereinafter, briefly referred to as a “touch pad”) 22 . A manner of manipulating on the touch pad 22 is sensed by a manipulation sensing circuit 24 . A CPU 30 repeatedly fetches a sense result of the manipulation sensing circuit 24 and executes a process corresponding to the fetched sense result.

A manipulation menu has a hierarchical structure as shown in FIG. 2 . A main menu has four items such as a “set up”, a “file transfer”, a “moving image file”, and a “still image file”. A sub menu at a lower hierarchy of the “set up” has three items such as a “sound effect”, a “luminance”, and a “return”. Moreover, a sub menu at a lower hierarchy of the “sound effect” has three items such as “YES”, “NO”, and a “return”, and a sub menu at a lower hierarchy of the “luminance” has four items such as a “high luminance”, an “intermediate luminance”, a “low luminance”, and a “return”.

A sub menu at a lower hierarchy of the “file transfer” has three items such as “card→storage”, “storage→card”, and a “return”. A sub menu at a lower hierarchy of the “moving image file” has items such as “M0001”, “M0002”, “M0003”, . . . , and a “return”. A sub menu at a lower hierarchy of the “still image file” has items such as “S0001”, “S0002”, “S0003”, . . . , and a “return”.

Herein, the item “sound effect” arranged at a lower hierarchy of the “set up” is an item for selecting whether or not a sound effect should be outputted from a speaker 40 in response to the manipulation of the touch pad 22 by an operator. When “YES” is selected, a sound generator 34 is started, and thereby, the sound effect is outputted from the speaker 40 at each touch manipulation. On the other hand, when “NO” is selected, the sound generator 34 is stopped, and thereby, the output of the sound effect from the speaker 40 is stopped.

The item “luminance” arranged at a lower hierarchy of the “set up” is an item for adjusting a brightness of an image displayed on an LCD monitor 36 . When the “high luminance” is selected, an LCD driver 32 is set to a high luminance, and then, the brightness of the image displayed on the LCD monitor 36 is increased. When the “intermediate luminance” is selected, the LCD driver 32 is set to an intermediate luminance, and then, the brightness of the image displayed on the LCD monitor 36 becomes moderate. When the “low luminance” is selected, the LCD driver 32 is set to a low luminance, and then, the brightness of the image displayed on the LCD monitor 36 is decreased.

The “file transfer” is an item for instructing a file transfer between: a memory card 12 detachably attached to an I/F 14 ; and an internal storage 28 . When the “card storage” is selected, a moving image file and/or a still image file accommodated in the memory card 12 is transferred to the storage 28 . When the “storage-card” is selected, the moving image file and/or the still image file accommodated in the storage 28 is transferred to the memory card 12 .

The “moving image file” is an item for selecting a moving image file to be reproduced, out of a plurality of moving image files accommodated in the storage 28 . “M0001”, “M0002”, “M0003”, . . . are all file names of the moving image files. When any one of these is selected, a moving image file having the selected file name is reproduced.

The “still image file” is an item for selecting a still image file to be reproduced, out of a plurality of still image files accommodated in the storage 28 . “S0001”, “S0002”, “S0003”, . . . are all file names of the still image files, and when any one of these is selected, a still image file having the selected file name is reproduced.

It is noted that in this embodiment, compressed moving image data compressed by a Motion JPEG system is contained in the moving image file, and compressed still image data compressed by a JPEG system is contained in the still image file.

A file transferring operation is executed as follows: When transferring from the memory card 12 to the storage 28 , firstly, the I/F 14 reads out the moving image file and/or the still image file from the memory card 12 , and writes the read-out moving image file and/or the still image file in an SDRAM 18 through a memory control circuit 16 . The moving image file and/or the still image file accommodated in the SDRAM 18 is applied via the memory control circuit 16 to an I/F 26 , and the I/F 26 writes the applied file in the storage 28 .

On the other hand, when transferring from the storage 28 to the memory card 12 , firstly, the I/F 26 reads out the moving image file and/or the still image file from the storage 26 , and writes the read-out moving image file and/or the still image file in the SDRAM 18 through the memory control circuit 16 . The moving image file and/or the still image file accommodated in the SDRAM 18 is applied via the memory control circuit 16 to the I/F 14 , and the I/F 14 writes the applied file in the memory card 12 .

A reproducing operation of the moving image file is executed as follows: The compressed moving image data accommodated in a desired moving image file is read out by the I/F 26 , and further written in the SDRAM 18 through the memory control circuit 16 . A JPEG decoder 20 reads out the compressed moving image data written in the SDRAM 18 through the memory control circuit 16 , decompresses the read-out compressed moving image data, and writes the decompressed moving image data in the SDRAM 18 through the memory control circuit 16 . The LCD driver 32 reads out the decompressed moving image data thus obtained through the memory control circuit 16 , and based on the read-out decompressed moving image data, drives the LCD monitor 36 . As a result, the moving image is displayed on a monitor screen. It is noted that the brightness of the displayed moving image complies with the luminance set to the LCD driver 32 as described above.

A reproducing operation of the still image file is executed as follows: The compressed still image data accommodated in a desired still image file is read out by the I/F 26 , and further written in the SDRAM 18 through the memory control circuit 16 . A JPEG decoder 20 reads out the compressed still image data written in the SDRAM 18 through the memory control circuit 16 , decompresses the read-out compressed still image data, and writes the decompressed still image data in the SDRAM 18 through the memory control circuit 16 . The LCD driver 32 repeatedly reads out the decompressed still image data thus obtained through the memory control circuit 16 , and based on the read-out decompressed still image data, drives the LCD monitor 36 . As a result, the still image is displayed on the monitor screen. It is noted that the brightness of the displayed still image also complies with the luminance set to the LCD driver 32 as described above.

With reference to FIG. 3(A) and FIG. 3(B) , the photo viewer 10 includes plate-shaped cases C 1 and C 2 axially supported for rotation by a hinge H 1 . The LCD monitor 36 is attached to the case C 1 in such a manner that its screen is exposed to an inner-side surface of the case C 1 . The inner-side surface of the case C 2 is covered with an insulating sheet IST 1 . On a top surface of the insulating sheet IST 1 , a circular determination key P 1 , a toroidal dial key P 2 , and strip-shaped function keys P 3 to P 6 are depicted. By the insulating sheet IST 1 and a printed-circuit board PCB 1 (described later) shown in FIG. 8 arranged on a bottom surface of the insulating sheet IST 1 , the touch pad 22 is formed.

Hereinafter, the function keys P 3 , P 4 , P 5 , and P 6 are equivalent to keys for directly selecting the “set up”, the “file transfer”, the “moving image file”, and the “still image file”. Moreover, the dial key P 2 is equivalent to a key for moving a cursor CS that is described later. Furthermore, the determination key P 1 is equivalent to a key for selecting an item at which the cursor CS points.

It is noted that each of the determination key P 1 and the function keys P 3 to P 6 has a size about that of an apex of a forefinger of a grown person. A width of a torus formed by the dial key P 2 also has a size about that of an apex of a forefinger of a grown person. The cursor CS moves on the screen when the finger slides on the torus formed by the dial key P 2 .

When power is inputted, the CPU 30 assigns the above-described function or a parameter to the determination key P 1 , the dial key P 2 , and the function keys P 3 to P 6 , and requests the character generator 34 to display the main menu and the cursor CS.

The character generator 34 applies corresponding character data to the LCD driver 32 , and as a result, an image shown in FIG. 4(A) is outputted from the LCD monitor 36 . According to FIG. 4(A) , the four items of the “setup”, the “file transfer”, the “moving image file”, and the “still image file”, and the cursor CS that points at the “set up” are displayed on the screen.

When the finger touches the function key P 3 , the CPU 30 requests the character generator 34 to display the sub menu existing at a lower hierarchy of the “set up” and the cursor CS. A similar request is issued toward the character generator 34 also when the finger slides on the torus formed by the dial key P 2 to adjust the cursor CS to the “set up”, and in this state, the finger touches the determination key P 1 .

As a result, the display on the LCD monitor 36 is transitioned from FIG. 4(A) to FIG. 4(B) . According to FIG. 4(B) , the three items of the “sound effect”, the “brightness”, and the “return”, and the cursor CS that points at the “sound effect” are displayed on the screen.

When the determination key P 1 is touched in a state that the cursor CS is adjusted to the “sound effect” by the dial key P 2 , the CPU 30 requests character generator 34 to display the sub menu existing at a lower hierarchy of the “sound effect” and the cursor CS. The display on the LCD monitor 36 is transitioned from FIG. 4(B) to FIG. 4(C) . According to FIG. 4(C) , the three items of the “YES”, the “NO”, and the “return”, and the cursor CS that points at the “YES” are displayed on the screen.

Herein, when the cursor CS is adjusted to “YES” by the dial key P 2 and the determination key P 1 is touched, the sound generator 38 is started by the CPU 30 . On the other hand, when the cursor CS is adjusted to “NO” by the dial key P 2 and the determination key P 1 is touched, the sound generator 38 is stopped by the CPU 30 .

When the cursor CS is adjusted to the “brightness” by the dial key P 2 on a screen shown in FIG. 4(B) and the determination key P 1 is touched, the CPU 30 requests the character generator 34 to display the sub menu existing at a lower hierarchy of the “brightness” and the cursor CS. The display on the LCD monitor 36 is transitioned from FIG. 4(B) to FIG. 4(D) . According to FIG. 4(D) , the four items of the “high luminance”, the “intermediate luminance”, the “low luminance”, and the “return”, and the cursor CS that points at the “high luminance” are displayed on the screen.

Herein, when the cursor CS is adjusted to the “high luminance” by the dial key P 2 and the determination key P 1 is touched, the high luminance is set to the LCD driver 32 . Moreover, when the cursor CS is adjusted to the “intermediate luminance” by the dial key P 2 and the determination key P 1 is touched, the intermediate luminance is set to the LCD driver 32 . Furthermore, when the cursor CS is adjusted to the “low luminance” by the dial key P 2 and the determination key P 1 is touched, the low luminance is set to the LCD driver 32 .

It is noted that on a screen shown in FIG. 4(B) , FIG. 4(C) , or FIG. 4(D) , when the cursor CS is adjusted to the “return” by the dial key P 2 , and the determination key P 1 is touched, the CPU 30 requests the character generator 34 to display the main menu and the cursor CS. As a result, the screen display is returned to FIG. 4(A) .

When the function key P 4 is touched in a state that the main menu is displayed, or the cursor CS is adjusted to the “file transfer” by the dial key P 2 and the determination key P 1 is touched, the CPU 30 requests the character generator 34 to display the sub menu existing at a lower hierarchy of the “file transfer” and the cursor CS. As a result, the display on the LCD monitor 36 is transitioned from FIG. 5(A) to FIG. 5(B) . According to FIG. 5(B) , the three items of “card→storage”, “storage→card”, and “return” and the cursor CS that points at “card→storage” are displayed on the screen.

Herein, when the cursor CS is adjusted to “card-storage” by the dial key P 2 and the determination key P 1 is touched, the moving image file and/or the still image file accommodated in the memory card 12 is transferred to the storage 28 . On the other hand, when the cursor CS is adjusted to “storage→card” by the dial key P 2 and the determination key P 1 is touched, the moving image file and/or the still image file accommodated in the storage 28 is transferred to the memory card 12 .

When the function key P 5 is touched in a state that the main menu is displayed, or the cursor CS is adjusted to the “moving image file” by the dial key P 2 and the determination key P 1 is touched, the CPU 30 requests the character generator 34 to display the sub menu existing at a lower hierarchy of the “moving image file” and the cursor CS. As a result, the display on the LCD monitor 36 is transitioned from FIG. 6(A) to FIG. 6(B) . According to FIG. 6(B) , the items of “M0001”, “M0002”, “M0003”, . . . , and the cursor CS that points at “M0001” are displayed on the screen.

Herein, when the cursor is adjusted to a desired file name by the dial key P 2 and the determination key P 1 is touched, the compressed moving image data accommodated in a moving image file having a file name at which the cursor CS points is reproduced, and a desired moving image is outputted from the LCD monitor 36 . The screen display is returned to FIG. 6(B) when the determination key P 1 is touched again.

When the function key P 6 is touched in a state that the main menu is displayed, or the cursor CS is adjusted to the “still image file” by the dial key P 2 and the determination key P 1 is touched, the CPU 30 requests the character generator 34 to display the sub menu existing at a lower hierarchy of the “still image file” and the cursor CS. As a result, the display on the LCD monitor 36 is transitioned from FIG. 7(A) to FIG. 7(B) . According to FIG. 7(B) , the items of “S0001”, “S0002”, “S0003”, . . . , and the cursor CS that points at “S0001” are displayed on the screen.

Herein, when the cursor is adjusted to a desired file name by the dial key P 2 and the determination key P 1 is touched, the compressed still image data accommodated in a still image file having a file name at which the cursor CS points is reproduced, and a desired still image is outputted from the LCD monitor 36 . The screen display is returned to FIG. 7(B) when the determination key P 1 is touched again.

It is noted that the image shown in FIG. 6(B) or FIG. 7(B) is scrolled when an undisplayed file name is displayed. When the item of “return” is displayed by this scrolling and the determination key P 1 is touched in a state that the cursor CS points at “return”, the screen display is returned to FIG. 6(A) or FIG. 7(A) .

With reference to FIG. 8 , the printed-circuit board PCB 1 includes 14 electrodes E 1 to E 14 printed on a top surface of the substrate SB 1 . The electrodes E 1 and E 2 are obtained by printing a circular metal on the substrate SB 1 and etching the printed circular metal in a diametrical direction. Also, the electrodes E 3 to E 10 are obtained by printing a toroidal metal on the substrate SB 1 in such a manner as to surround the electrodes E 1 and E 2 and etching the printed toroidal metal in a radial direction at eight positions spaced at 45 degrees. Moreover, the electrodes E 11 to E 14 are printed in a strip shape on the substrate SB 1 so as to be positioned outside the torus depicted by the electrodes E 3 to E 10 . On the top surface of the substrate SB 1 , the conductive lines L 1 to L 14 are also printed. The electrodes E 1 to E 14 are connected to one ends of the conductive lines L 1 to L 14 , respectively, and the other ends of the conductive lines L 1 to L 14 reach an end of the substrate SB 1 .

As a result, an electrical conductor EC 1 is formed by the electrode E 1 and the conductive line L 1 ; an electrical conductor EC 2 is formed by the electrode E 2 and the conductive line L 2 ; an electrical conductor EC 3 is formed by the electrode E 3 and the conductive line L 3 ; an electrical conductor EC 4 is formed by the electrode E 4 and the conductive line L 4 ; and an electrical conductor EC 5 is formed by the electrode E 5 and the conductive line L 5 .

Moreover, an electrical conductor EC 6 is formed by the electrode E 6 and the conductive line L 6 ; an electrical conductor EC 7 is formed by the electrode E 7 and the conductive line L 7 ; an electrical conductor EC 8 is formed by the electrode E 8 and the conductive line L 8 ; an electrical conductor EC 9 is formed by the electrode E 9 and the conductive line L 9 ; and an electrical conductor EC 10 is formed by the electrode E 10 and the conductive line L 10 .

Furthermore, an electrical conductor EC 11 is formed by the electrode E 11 and the conductive line L 11 ; an electrical conductor EC 12 is formed by the electrode E 12 and the conductive line L 12 ; an electrical conductor EC 13 is formed by the electrode E 13 and the conductive line L 13 ; and an electrical conductor EC 14 is formed by the electrode E 14 and the conductive line L 14 .

Herein, the conductive line L 1 extends into a void between the electrodes E 7 and E 8 so as to contact neither the electrodes E 7 nor E 8 . Also, the conductive line 12 extends into a void between the electrodes E 5 and E 6 so as to contact neither the electrodes E 5 nor E 6 . That is, the conductive lines L 1 and L 2 that need to cross the torus depicted by the electrodes E 3 to E 10 in order to reach the end of the substrate SB 1 extend from inside the toms to outside thereof in such a manner as to sandwich at least one of the electrodes E 3 to E 10 and not to contact the electrodes E 3 to E 10 .

The insulating sheet LST 1 shown in FIG. 3(A) and FIG. 3(B) is stacked on the top surface of the printed-circuit board PCB 1 . The determination key P 1 is depicted in a circular shape at a position to cover the electrodes E 1 and E 2 , the dial key P 2 is depicted in a toroidal shape at a position to cover the electrodes E 3 to E 10 , and the function keys P 3 to P 6 are depicted in a strip shaped at positions respectively to cover the electrodes E 11 to E 14 .

The manipulation sensing circuit 24 is configured as shown in FIG. 9 . Capacitances VC 1 to VC 14 of the electrical conductors EC 1 to EC 14 are determined by decoders 2401 to 2414 , respectively. From each of the decoders 2401 to 2414 , a decode value equivalent to “H” or “L” is outputted. It is noted that “H” is equivalent to an active decode value, and “L” is equivalent to a negative decode value.

An operation of each of the decoders 2401 to 2414 is described with reference to FIG. 10 , FIG. 11(A) , and FIG. 11(B) . For example, when the finger of the operator comes into contact with the function key P 3 , the capacitance VC 11 of the electrical conductor EC 11 is increased. Likewise, when the finger of the operator comes into contact with the determination key P 1 , the capacitance VC 1 of the electrical conductor EC 1 and the capacitance VC 2 of the electrical conductor EC 2 are increased.

An input impedance Zin changes depending on such contact/non-contact of the finger. Due to a design error, there is a disparity between a magnitude of the input impedance Zin in a non-contact state and that of a reference impedance Zref (see FIG. 11(A) ). When this disparity is defined as a “difference impedance ZinI”, the magnitude of the difference impedance ZinI is stable in a non-contact state, and increases as a time period elapses in a contact state.

When such an increase amount of the a difference impedance ZinI is defined as “ΔZin”, output of each of the decoders 2401 to 2414 indicates “L” when the increase amount ΔZin falls below a threshold value TB, and on the other hand, indicates “H” when the increase amount ΔZin is equal to or more than the threshold value TH.

The CPU 30 executes a plurality of tasks, including a manipulation determining task shown in FIG. 12 and FIG. 13 , in a parallel manner. It is noted that a control program corresponding to these tasks is stored in a flash memory 42 .

Firstly, in a step S 1 , an initializing setting is performed. As a result, the above-described function or parameter is assigned to the determination key P 1 (i.e., the electrodes E 1 and E 2 ), the dial key P 2 (i.e., the electrodes E 3 to E 10 ), and the function keys P 3 to P 6 (i.e., the electrodes E 11 to E 14 ), and a display request of the main menu and the cursor CS is issued toward the character generator 34 .

In a subsequent step S 3 , from the decoders 2401 to 2414 , a total of 14 decode values are fetched. In a step S 5 , it is determined whether or not the number of decode values indicating “H”, out of the 14 fetched decode values, exceeds “2”. When YES is determined, the process directly returns to the step S 3 whereas when NO is determined, the process undergoes processes in steps S 7 to S 19 , and then, returns to the step S 3 . That is, the processes following the step S 7 are permitted when the number of decode values indicating “H” is equal to or less than two, and are prohibited when the number of decode values indicating “H” is equal to or more than three.

In the step S 7 , it is determined whether or not the decode value outputted from the decoder 2401 indicates “H”, and in the step S 9 , it is determined whether or not the decode value outputted from the decoder 2402 indicates “H”. When YES is determined in the both steps S 7 and S 9 , a determining process, i.e., a process for selecting an item at which the cursor CS points, is executed in the step S 11 , and then, the process returns to the step S 3 .

On the other hand, when NO is determined in the step S 7 or S 9 , it is determined in a step S 13 whether or not one or two of the decode values of the decoders 2403 to 2410 indicate “H”, and it is determined in a step S 15 whether or not one or two of the decode values of the decoders 2411 to 2414 indicate “H”. When YES is determined in the step S 13 , the process advances to a step S 17 so as to move the cursor CS in a desired direction or scroll the display items in up and down directions. When YES is determined in the step S 15 , the display of the corresponding sub menu and the cursor is requested to the character generator 34 . Upon completion of the process in the step S 17 or S 19 , or when NO is determined in the both steps S 13 and S 15 , the process returns to the step S 3 .

As understood from the above description, the electrodes E 1 and E 2 are formed on the substrate SB 1 . Moreover, the electrodes E 3 to E 10 are formed on the substrate SB 1 in such a manner as to surround the electrodes E 1 and E 2 . The conductive lines L 1 and L 2 extend over the substrate SB 1 in such a manner as to sandwich electrodes E 6 and E 7 , and are connected to the electrodes E 1 and E 2 , respectively. The insulating sheet IST 1 , which has the top surface exposed to outside, covers the electrodes E 1 to E 10 and the conductive lines L 1 to L 10 .

In a case that the finger of the operator contacts the top surface of the insulating sheet IST 1 , if there are the electrodes E 1 and E 2 on the bottom side of the contact portion, the capacitance VC 1 of the electrical conductor EC 1 and the capacitance VC 2 of the electrical conductor EC 2 change. Likewise, in a case that the finger of the operator contacts the top surface of the insulating sheet IST 1 , if there are the electrode E 7 and the conductive line L 1 extending in the vicinity thereof on the bottom side of the contact portion, the capacitance VC 7 of the electrical conductor EC 7 and the capacitance VC 1 of the electrical conductor EC 1 change.

However, in this embodiment, the two electrodes E 1 and E 2 and the two conductive lines L 1 and L 2 are prepared, and the conductive lines L 1 and L 2 extend in such a manner as to sandwich the electrodes E 6 and E 7 . Therefore, when the capacitance VC 1 of the electrical conductor EC 1 and the capacitance VC 2 of the electrical conductor EC 2 are individually monitored, it becomes clear whether the change of the capacitance VC 1 results from contacting of the finger with a portion that covers the electrodes E 1 and E 2 or results from contacting of the finger with a portion that covers the electrode E 7 and the conductive line L 1 that extends in the vicinity thereof. Thereby, it becomes possible to prevent an erroneous determination of a manner of manipulating.

It is noted that in this embodiment, inside the torus depicted by the electrodes E 3 to E 10 , a pair of electrodes E 1 and E 2 are formed. However, as in a printed-circuit board PCB 2 shown in FIG. 14 , two or more pairs of electrodes may be formed inside the torus.

According to FIG. 14 , electrodes E 1 a and E 2 a form a pair, and conductive lines L 1 a and L 2 a extend from the electrodes E 1 a and E 2 a , respectively. Moreover, electrodes E 1 b and E 2 b form a pair, and conductive lines L 1 b and L 2 b extend from the electrodes E 1 b and E 2 b , respectively. Furthermore, electrodes E 1 c and E 2 c form a pair, and conductive lines L 1 c and L 2 c extend from electrodes E 1 c and E 2 c , respectively. Still furthermore, electrodes E 1 d and E 2 d form a pair, and conductive lines L 1 d and L 2 d extend from the electrodes E 1 d and E 2 d , respectively.

Herein, the conductive line L 1 a extends into a void between the electrodes E 9 and E 10 , and the conductive line L 2 a extends into a void between the electrodes E 10 and E 3 . Moreover, the conductive line L 1 b extends into a void between the electrodes E 4 and E 5 , and the conductive line L 2 b extends into a void between the electrodes E 3 and E 4 . Furthermore, the conductive line L 1 c extends into a void between the electrodes E 6 and E 7 , and the conductive line L 2 c extends into a void between the electrodes E 5 and E 6 . Also, the conductive line L 1 d extends into a void between the electrodes E 7 and E 8 , and the conductive line L 2 d extends into a void between the electrodes E 8 and E 9 .

Moreover, in this embodiment, the printed-circuit board PCB 1 is covered with the single insulating sheet IST 1 . However, the printed-circuit board PCB 1 may be locally covered with a plurality of pieces of divided insulating sheets.

Moreover, in this embodiment, as the parameter assigned to the electrodes E 3 to E 10 , the cursor CS is assumed, and as the parameter value that is modified in response to the touch manipulation on the dial key P 2 , a position of the cursor CS is assumed. However, as the parameter and its value assigned to the electrodes E 3 to E 10 , a sound effect and its magnitude may be assumed, and an image frame to be reproduced and its position may be assumed.

Also, in this embodiment, as the capacitive touch pad apparatus, the photo viewer is assumed. However, it is needless to say that the present invention may also be applied to apparatuses such as an audio player.

Moreover, according to this embodiment, each of the decoders 2401 to 2414 compares the increase amount ΔZin of the difference impedance ZinI with the threshold value TH so as to switch the output between “H” and “L”. However, each of the decoders 2401 to 2414 may output “H” when input impedance Zin>reference impedance Zref is established, and on the other hand, may output “L” when input impedance Zin≦reference impedance Zref is established.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.