Patent Publication Number: US-2016224168-A1

Title: Electronic apparatus and method of controlling electronic apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to an electronic apparatus including a display device, a touch panel, and a pressure-sensitive sensor, and a method of controlling the electronic apparatus. 
     For designated countries which permit the incorporation by reference, the contents described and/or illustrated in the documents relevant to Japanese Patent Application No. 2013-191401 filed on Sep. 17, 2013 will be incorporated herein by reference as a part of the description and/or drawings of the present application. 
     BACKGROUND ART 
     It is known an electronic apparatus in which a touch panel is disposed on an upper side of a liquid crystal panel to detect an input position on a screen, and a pressure applied to the touch panel is detected by using a pressure-sensitive sensor (for example, refer to Patent Document 1). 
     CITATION LIST 
     Patent Document 
     Patent Document 1: JP 2010-244514 A 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     In the above-described electronic apparatus, the pressure-sensitive sensor is disposed at four corners of the touch panel, and the touch panel is supported to a housing through the pressure-sensitive sensor. Accordingly, there is a problem that detection accuracy of the four pressure-sensitive sensors varies depending on the posture of the electronic apparatus, and the like. 
     An object of the invention is to provide an electronic apparatus capable of improving pressure detection accuracy, and a method of controlling the electronic apparatus. 
     Means for Solving Problem 
     [1] An electronic apparatus according to the present invention is an electronic apparatus comprising: a cover member including a transparent portion; a touch panel on which the cover member is laid; a display unit which includes a display region which faces the transparent portion through the touch panel; pressure-sensitive sensors which deform in accordance with pressing of the cover member; and a control unit which is electrically connected to the touch panel and the pressure-sensitive sensor. The control unit includes: a detection unit which outputs a detection signal on the basis of an output value of the touch panel; a setting unit which sets, as a reference value, an output value of the pressure-sensitive sensor at a predetermined timing in a case where the detection signal is input from the detection unit; and a first calculation unit which calculates, as a first pressure which is applied to the pressure-sensitive sensor, a difference between an output value of the pressure-sensitive sensor after the predetermined timing and the reference value. The setting unit individually sets the reference value with respect to each of the pressure-sensitive sensors. The first calculation unit individually calculates the first pressure with respect to each of the pressure-sensitive sensors each time the output value of each of the pressure-sensitive sensors is input. The detection signal is a signal which represents that contact of an object to be detected with the cover member is detected. The predetermined timing is a point of time immediately before detecting the contact of the object or a point of time at which the contact of the object is detected. 
     [2] An electronic apparatus according to the present invention is an electronic apparatus comprising: a cover member including a transparent portion; a touch panel on which the cover member is laid; a display unit which includes a display region which faces the transparent portion through the touch panel; pressure-sensitive sensors which deform in accordance with pressing of the cover member, and a control unit which is electrically connected to the touch panel and the pressure-sensitive sensor. The control unit includes: a detection unit which outputs a detection signal on the basis of an output value of the touch panel; a setting unit which sets, as a reference value, an output value of the pressure-sensitive sensor at a predetermined timing in a case where the detection signal is input from the detection unit; and a first calculation unit which calculates, as a first pressure which is applied to the pressure-sensitive sensor, a difference between an output value of the pressure-sensitive sensor after the predetermined timing and the reference value. The setting unit individually sets the reference value with respect to each of the pressure-sensitive sensors. The first calculation unit individually calculates the first pressure with respect to each of the pressure-sensitive sensors each time the output value of each of the pressure-sensitive sensors is input. The detection signal is a signal which represents that approaching of an object to be detected to the cover member in a predetermined distance is detected. The predetermined timing is a point of time at which the approaching of the object is detected or a point of time immediately after detecting the approaching of the object. 
     [3] An electronic apparatus according to the present invention is an electronic apparatus comprising: a cover member including a transparent portion; a touch panel on which the cover member is laid; a display unit which includes a display region which faces the transparent portion through the touch panel; pressure-sensitive sensors which deform in accordance with pressing of the cover member; and a control unit which is electrically connected to the touch panel and the pressure-sensitive sensor. The control unit includes: a detection unit which outputs a detection signal on the basis of an output value of the touch panel; a setting unit which sets, as a reference value, an output value of the pressure-sensitive sensor at a predetermined timing in a case where the detection signal is input from the detection unit; and a first calculation unit which calculates, as a first pressure which is applied to the pressure-sensitive sensor, a difference between an output value of the pressure-sensitive sensor after the predetermined timing and the reference value. The setting unit individually sets the reference value with respect to each of the pressure-sensitive sensors. The first calculation unit individually calculates the first pressure with respect to each of the pressure-sensitive sensors each time the output value of each of the pressure-sensitive sensors is input. The control unit further includes: a selection unit which selects, as a comparison value, any one of the reference values; and a correction unit which corrects the first pressure on the basis of the comparison value and the reference value. 
     [4] The control unit may further include a second calculation unit which calculates, as a second pressure which is applied to the cover member, the sum of the first pressures. 
     [5] A method of controlling an electronic apparatus according to the present invention is a method of controlling an electronic apparatus including a cover member including a transparent portion, a touch panel on which the cover member is laid, a display unit which includes a display region which faces the transparent portion through the touch panel, and pressure-sensitive sensors which deform in accordance with pressing of the cover member. The method comprises: a first step of detecting contact of an object to be detected with the cover member or approaching of the object to the cover member on the basis of an output value of the touch panel; a second step of setting, as a reference value, an output value of the pressure-sensitive sensor at a predetermined timing in a case where the contact or the approaching of the object is detected; and a third step of calculating, as a first pressure which is applied to the pressure-sensitive sensor, a difference between an output value of the pressure-sensitive sensor after the predetermined timing and the reference value. The second step includes individually setting the reference value with respect to each of the pressure-sensitive sensors. The third step includes individually calculating the first pressure with respect to the pressure-sensitive sensors each time the output value of each of the pressure-sensitive sensors is input. The first step includes detecting the contact of the object with the cover member. The predetermined timing is a point of time immediately before detecting the contact of the object, or a point of time at which the contact of the object is detected. 
     [6] A method of controlling an electronic apparatus according to the present invention is a method of controlling an electronic apparatus including a cover member including a transparent portion, a touch panel on which the cover member is laid, a display unit which includes a display region which faces the transparent portion through the touch panel, and pressure-sensitive sensors which deform in accordance with pressing of the cover member. The method comprises: a first step of detecting contact of an object to be detected with the cover member or approaching of the object to the cover member on the basis of an output value of the touch panel; a second step of setting, as a reference value, an output value of the pressure-sensitive sensor at a predetermined timing in a case where the contact or the approaching of the object is detected; and a third step of calculating, as a first pressure which is applied to the pressure-sensitive sensor, a difference between an output value of the pressure-sensitive sensor after the predetermined timing and the reference value. The second step includes individually setting the reference value with respect to each of the pressure-sensitive sensors. The third step includes individually calculating the first pressure with respect to each of the pressure-sensitive sensors each time the output value of each of the pressure-sensitive sensors is input. The first step includes detecting the approaching of the object to the cover member in a predetermined distance. The predetermined timing is a point of time at which the approaching of the object is detected or a point of time immediately after detecting the approaching of the object. 
     [7] A method of controlling an electronic apparatus according to the present invention is a method of controlling an electronic apparatus including a cover member including a transparent portion, a touch panel on which the cover member is laid, a display unit which includes a display region which faces the transparent portion through the touch panel, and pressure-sensitive sensors which deform in accordance with pressing of the cover member. The method comprises: a first step of detecting contact of an object to be detected with the cover member or approaching of the object to the cover member on the basis of an output value of the touch panel; a second step of setting, as a reference value, an output value of the pressure-sensitive sensor at a predetermined timing in a case where the contact or the approaching of the object is detected; and a third step of calculating, as a first pressure which is applied to the pressure-sensitive sensor, a difference between an output value of the pressure-sensitive sensor after the predetermined timing and the reference value. The second step includes individually setting the reference value with respect to each of the pressure-sensitive sensors. The third step includes individually calculating the first pressure with respect to each of the pressure-sensitive sensors each time the output value of each of the pressure-sensitive sensors is input. The method further includes: a fourth step of selecting, as a comparison value, any one of the reference values; and a fifth step of correcting the first pressure on the basis of the comparison value and the reference value. 
     [8] The method of controlling an electronic apparatus may further include a sixth step of calculating, as a second pressure which is applied to the cover member, the sum of the first pressures. 
     Effect of the Invention 
     According to the invention, since the difference between the output value of the pressure-sensitive sensor and the reference value is calculated as the first pressure, it is possible to cancel an effect due to the posture of the electronic apparatus and the like, and it is possible to realize an improvement in pressure detection accuracy by the pressure-sensitive sensor. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of an electronic apparatus in an embodiment of the invention; 
         FIG. 2  is a cross-sectional view taken along line II-II in  FIG. 1 ; 
         FIG. 3  is a plan view of a cover member in the embodiment of the invention. 
         FIG. 4  is a bottom view of a reinforcing member in the embodiment of the invention; 
         FIG. 5  is an exploded perspective view of a touch panel in the embodiment of the invention; 
         FIG. 6  is a plan view of a display device in the embodiment of the invention; 
         FIG. 7  is a cross-sectional view of a pressure-sensitive sensor in the embodiment of the invention; 
         FIG. 8  is a plan view illustrating arrangement of the pressure-sensitive sensor on a support member in the embodiment of the invention; 
         FIG. 9  is a block diagram illustrating a control device of an electronic apparatus in the embodiment of the invention; 
         FIG. 10  is a circuit diagram illustrating an acquisition unit in the embodiment of the invention; 
         FIG. 11  is a circuit diagram illustrating a first modification example of the acquisition unit in the embodiment of the invention; 
         FIG. 12  is a circuit diagram illustrating a second modification example of the acquisition unit in the embodiment of the invention; 
         FIG. 13  is a view illustrating a pressure-output characteristics of the pressure-sensitive sensor; and 
         FIG. 14  is a flowchart illustrating a method of detecting a pressure in the embodiment of the invention. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. 
       FIG. 1  and  FIG. 2  are a plan view and a cross-sectional view of an electronic apparatus in a first embodiment of the invention,  FIG. 3  is a plan view of a cover member,  FIG. 4  is a bottom view of a reinforcing member,  FIG. 5  is an exploded perspective view of a touch panel,  FIG. 6  is a plan view of a display device,  FIG. 7  is a cross-sectional view of a pressure-sensitive sensor, and  FIG. 8  is a plan view illustrating arrangement of the pressure-sensitive sensor on a support member. 
     As illustrated in  FIG. 1  and  FIG. 2 , an electronic apparatus  1  in the present embodiment includes a movable unit  10 , a pressure-sensitive sensor  60 , a seal member  70 , and a support member  80 . The movable unit  10  includes a cover member  20 , a reinforcing member  30 , a touch panel  40 , and a display device  50 . The movable unit  10  is supported to the support member  80  through the pressure-sensitive sensor  60  and the seal member  70 , and a minute vertical movement of the movable unit  10  with respect to the support member  80  is permitted due to an elastic deformation of the pressure-sensitive sensor  60  and the seal member  70 . 
     The electronic apparatus  1  can display an image by the display device  50  (display function). In addition, in a case where an arbitrary position on the cover member  20  is indicated by a finger of an operator, a touch pen, and the like, the electronic apparatus  1  can detect XY coordinates of the position with the touch panel  40  (position input function). In addition, in a case where the movable unit  10  is pressed with a finger of the operator and the like, the electronic apparatus  1  can detect the pressing operation with the pressure-sensitive sensor  60 . 
     As illustrated in  FIG. 2  and  FIG. 3 , the cover member  20  is constituted by a transparent substrate  21  through which visible light beams can be transmitted. Specific examples of a material of which the transparent substrate  21  is made include glass, polymetylmethacrylate (PMMA), polycarbonate (PC), and the like. 
     For example, a shielding portion (bezel portion)  23 , which is formed by applying white ink, black ink, and the like, is provided on a lower surface of the transparent substrate  21 . The shielding portion  23  is formed in a frame shape in a region on the lower surface of the transparent substrate  21  except for a rectangular transparent portion  22  which is located at the center of the lower surface. The shapes of the transparent portion  22  and the shielding portion  23  are not particularly limited to the above-described shapes. A decorating member which is decorated with a white color or a black color may be laminated on a lower surface of the transparent substrate  21  so as to form the shielding portion  23 . Alternatively, a transparent sheet, which has substantially the same size as the transparent substrate  21  and in which only a portion corresponding to the shielding portion  23  is colored with a white color or a black color, may be prepared, and the sheet may be laminated on the lower surface of the transparent substrate  21  so as to form the shielding portion  23 . 
     As illustrated in  FIG. 2  and  FIG. 4 , the reinforcing member  30  is a frame-shaped member that is fixed to the lower surface of the cover member  20  through a gluing agent  24 . The reinforcing member  30  is attached to the shielding portion  23  of the cover member  20 , and the reinforcing member  30  is not visually recognized to the operator. In the present embodiment, an adhesive may be used instead of the gluing agent  24 ,  25 ,  33 , or  83 . 
     The reinforcing member  30  includes a main body portion  31  and a protruding portion  32 . The main body portion  31  has a rectangular frame shape, and extends in a direction which is substantially parallel to a main surface of the cover member  20 . On the other hand, the protruding portion  32  has a square tubular shape which communicates with an opening  311  of the main body portion  31 , and protrudes from an inner edge of the main body portion  31  toward a lower side. A screw hole  321  for screwing of the display device  50  is formed in a tip end surface of the protruding portion  32 . The reinforcing member  30  is made of a material which is hard and excellent in workability, for example, a metallic material such as stainless steel (SUS), a resin material such as an ABS resin or polycarbonate (PC), and a composite material such as fiber reinforced plastic (FRP). The main body portion  31  and the protruding portion  32  are integrally formed. 
     As illustrated in  FIG. 5 , the touch panel  40  is an electrostatic capacitance type touch panel including two electrode sheets  41  and  42  which overlap each other. The structure of the touch panel is not particularly limited thereto, and for example, a resistive film type touch panel or an electromagnetic induction type touch panel may be employed. The following first electrode pattern  412  or second electrode pattern  422  may be formed on the lower surface of the cover member  20 , and the cover member  20  may be used as a part of the touch panel. Alternatively, a sheet, in which an electrode is formed on both surfaces thereof, may be used instead of the two electrode sheets  41  and  42 . 
     The first electrode sheet  41  includes a first transparent substrate  411  through which visible light beams can be transmitted, and first electrode patterns  412  which are provided on the first transparent base material  411 . 
     Specific examples of a material of which the first transparent substrate  411  is made include resin materials such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), polystyrene (PS), an ethylene-vinyl acetate copolymer resin (EVA), vinyl resin, polycarbonate (PC), polyamide (PA), polyimide (PI), polyvinyl alcohol (PVA), an acrylic resin, and triacetyl cellulose (TAC). 
     For example, the first electrode patterns  412  are transparent electrodes which are made of indium tin oxide (ITO) or a conductive polymer, and are configured as strip-like face patterns (so-called solid patterns) which extend in a Y direction in  FIG. 5 . In an example illustrated in  FIG. 5 , nine first electrode patterns  412  are arranged in parallel on the first transparent substrate  411 . The shape, the number, the arrangement, and the like of the first electrode patterns  412  are not particularly limited to the above-described configurations. 
     In the case where the first electrode patterns  412  is made of ITO, for example, the first electrode patterns  412  are formed through sputtering, photolithography, and etching. On the other hand, in the case where the first electrode patterns  412  is made of a conductive polymer, the first electrode patterns  412  can be formed through sputtering and the like similar to the case of ITO, or can be formed through a printing method such as screen printing and gravure-offset printing, or through etching after coating. 
     Specific examples of the conductive polymer of which the first electrode patterns  412  is made include organic compounds such as a polythiophene-based compound, a polypyrrole-based compound, a polyaniline-based compound, a polyacetylene-based compound, and a polyphenylene-based compound. A PEDOT/PSS compound is preferably used among these compounds. 
     Furthermore, the first electrode patterns  412  may be formed by printing conductive paste on the first transparent substrate  411  and by curing the conductive paste. In this case, each of the first electrode patterns  412  is formed in a mesh shape instead of the face pattern so as to secure sufficient light transmittance of the touch panel  30 . As the conductive paste, for example, conductive paste, which is obtained by mixing metal particles such as silver (Ag) and copper (Cu), and a binder such as polyester and polyphenol, can be used. 
     The first electrode patterns  412  are connected to a touch panel control unit  91  (see  FIG. 9 ) through a first lead-out wiring pattern  413 . The first lead-out wiring pattern  413  is provided at a position, which faces the shielding portion  23  of the cover member  20 , on the first transparent substrate  411 , and the first lead-out wiring pattern  413  is not visually recognized to the operator. Therefore, the first lead-out wiring pattern  413  is formed by printing conductive paste on the first transparent substrate  411  and by curing the conductive paste. 
     The second electrode sheet  42  also includes a second transparent substrate  421  through which visible light beams can be transmitted, and second electrode patterns  422  which are provided on the second transparent substrate  421 . 
     The second transparent substrate  421  is made of the same material as in the above-described first transparent substrate  411 . Similar to the above-described first electrode patterns  412 , the second electrode patterns  422  are also transparent electrodes which are made of, for example, indium tin oxide (ITO) or a conductive polymer. 
     The second electrode patterns  422  are configured as rectangular face patterns which extend in an X direction in  FIG. 5 . In an example illustrated in  FIG. 5 , six second electrode patterns  422  are arranged in parallel on the second transparent substrate  421 . The shape, the number, the arrangement, and the like of the second electrode patterns  422  are not particularly limited to the above-described configurations. 
     The second electrode patterns  422  are connected to the touch panel control unit  91  (see  FIG. 9 ) through a second lead-out wiring pattern  423 . The second lead-out wiring pattern  423  is provided at a position, which faces the shielding portion  23  of the cover member  20 , on the second transparent substrate  421 , and the second lead-out wiring pattern  423  is not visually recognized to the operator. Therefore, similar to the above-described first lead-out wiring pattern  413 , the second lead-out wiring pattern  423  is also formed by printing conductive paste on the second transparent substrate  421  and by curing the conductive paste. 
     The first electrode sheet  41  and the second electrode sheet  42  are attached to each other through a transparent gluing agent in such a manner that the first electrode patterns  412  and the second electrode patterns  422  are substantially orthogonal to each other in a plan view. The touch panel  40  itself is attached to the lower surface of the cover member  20  through the transparent gluing agent  25  in such a manner that the first and second electrode patterns  412  and  422  face the transparent portion  22  of the cover member  20 . Specific examples of the transparent gluing agent  25  include an acryl-based gluing agent, and the like. 
     As illustrated in  FIG. 6 , the display device  50  includes a display region  51  on which an image is displayed, an outer edge region  52  which surrounds the display region  51 , and a flange  53  which protrudes from both ends of the outer edge region  52 . For example, the display region  51  of the display device  50  is constituted by a thin type display device such as a liquid crystal display, an organic EL display, or an electronic paper. 
     Two kinds of through-holes  531  and  532  are formed in the flange portion  53 . Each of the first through-holes  531  faces each of screw holes  321  which is formed in the protruding portion  32  of the reinforcing member  30 . On the other hand, each of the second through-holes  532  faces each of screw holes  81  (to be described later) of the support member  80 . 
     As illustrated in  FIG. 2 , when a bolt  54  screwed into the screw hole  321  through the first through-hole  531 , the display device  50  is fixed to the reinforcing member  30 . According to this, the display region  51  faces the transparent portion  22  of the cover member  20  through the opening  311  of the reinforcing member  30 . 
     In the present embodiment, when the bolt  54  is fastened to the reinforcing member  30 , the outer edge region  52  of the display device  50  is brought into close contact with a lower surface of the touch panel  40 , and thus the touch panel  40  is interposed between the cover portion  20  and the display device  50 . According to this, a gap between the touch panel  40  and the display device  50  is not present, and thus appearance of a screen in the electronic apparatus  1  is improved. 
     In addition, in the present embodiment, since the touch panel  40  and the display device  50  can be brought into close contact with each other without using a gluing agent, there is no concern that foreign matter or air bubbles are trapped between the touch panel  40  and the display device  50 , and thus a yield ratio of a product is improved. 
     The outer edge region  52  and the touch panel  40  may be fixed to each other by applying the gluing agent (a broken line portion  521  in  FIG. 6 ) only to the outer edge region  52 . According to this, it is possible to enhance the rigidity of the movable unit  10 , and thus it is possible to make the elements  20  to  50  of the movable unit  10  thin. As a result, it is possible to make the entirety of the movable unit  10  thin. An adhesive may be used instead of the gluing agent  521 . 
     As illustrated in  FIG. 1  and  FIG. 2 , the pressure-sensitive sensors  60  are attached to four corners of the above-described movable unit  10 . The number and the arrangement of the pressure-sensitive sensor  60  are not particularly limited as long as the pressure-sensitive sensors  60  can stably hold the movable unit  10 . The configuration of the pressure-sensitive sensor is not limited to the following configuration as long as a pressure can be detected. For example, an electrostatic capacitance type sensor, a pressure-sensitive conductive rubber, a strain gauge, a piezoelectric element, and the like may be used as the pressure-sensitive sensor. 
     As illustrated in  FIG. 7 , each of the pressure-sensitive sensors  60  includes a first electrode sheet  61 , a second electrode sheet  62 , and a spacer  63  which is interposed therebetween.  FIG. 7  is a cross-sectional view taken along line VII-VII in  FIG. 8  to be described later. 
     The first electrode sheet  61  includes a first substrate  611  and an upper electrode  612 . The first substrate  611  is a flexible insulating film, and is made of, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyetherimide (PEI), and the like. 
     The upper electrode  612  includes a first upper electrode layer  613  and a second upper electrode layer  614 , and is provided on a lower surface of the first substrate  611 . The first upper electrode layer  613  is formed by printing conductive paste, which has a relative low electric resistance, on the lower surface of the first substrate  611 , and by curing the conductive paste. On the other hand, the second upper electrode layer  614  is formed by printing conductive paste, which has a relatively high electric resistance, on the lower surface of the first substrate  611  so as to cover the first upper electrode layer  613 , and by curing the conductive paste. 
     The second electrode sheet  62  also includes a second substrate  621  and a lower electrode  622 . The second substrate  621  is made of the same material as in the above-described first substrate  611 . The lower electrode  622  includes a first lower electrode layer  623  and a second lower electrode layer  624 , and is provided on an upper surface of the second substrate  621 . 
     Similar to the above-described first upper electrode layer  613 , the first lower electrode layer  623  is formed by printing conductive paste, which has a relatively low electric resistance, on an upper surface of the second substrate  621 , and by curing the conductive paste. On the other hand, similar to the above-described second upper electrode layer  614 , the second lower electrode layer  624  is formed by printing conductive paste, which has a relatively high electric resistance, on the upper surface of the second substrate  621  so as to cover the first lower electrode layer  623 , and by curing the conductive paste. 
     Examples of the conductive paste, which has a relatively low electric resistance, include silver (Ag) paste, gold (Au) paste, and copper (Cu) paste. In contrast, examples of the conductive past, which has a relatively high electric resistance, include carbon (C) paste. Examples of a method of printing the conductive paste include screen printing, gravure-offset printing, an inkjet method, and the like. 
     The first electrode sheet  61  and the second electrode sheet  62  are laminated through the spacer  63 . The spacer  63  is made of an insulating material such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), and polyetherimide (PEI). 
     An opening  631  is formed in the spacer  63  at a position which corresponds to the upper electrode  612  and the lower electrode  622 . The upper electrode  612  and the lower electrode  622  are located inside the opening  631  and face each other. The thickness of the spacer  63  is set so that the upper electrode  612  and the lower electrode  622  come into contact with each other. The upper electrode  612  and the lower electrode  622  may not come into contact with each other. However, when the upper electrode  612  and the lower electrode  622  are brought into contact with each other in advance, a problem, in which the electrodes do not contact with each other even when a pressure is applied (that is, an output of the pressure-sensitive sensor  60  is zero (0)), does not occur, and thus it is possible to realize an improvement in detection accuracy. 
     The second upper electrode layer  614  or the second lower electrode layer  624  may be formed by printing pressure-sensitive ink instead of the carbon paste, and by curing the pressure-sensitive ink. The electrode layers  613 ,  614 ,  623 , and  624  can be formed through a plating process or a patterning process instead of the printing method. 
     The support member  80  supports the movable unit  10  through the pressure-sensitive sensor  60 , and is made of, for example, a metallic material such as aluminum, or a resin material such as polycarbonate (PC) or an ABS resin. As described above, the pressure-sensitive sensors  60  are disposed at four corners of the support member  80 . As illustrated in  FIG. 8 , the seal member  70  is provided on the support member  80  along an outer edge of the support member  80  to be located on an outer side of the pressure-sensitive sensor  60 . Although not particularly illustrated in the drawings, the pressure-sensitive sensors  60  may be disposed between the lower surface of the display device  50  and the upper surface of the support member  80 . 
     The annular seal member  70  is made of a material which has a compressive elasticity modulus which is relatively lower than that of the pressure-sensitive sensor, and has a sealing property. Specific examples of the material of which the seal member  70  made of include urethane foam having closed cells, and the like. The seal member  70  prevents foreign matter from intruding into a space between the movable unit  10  and the support member  80  from an outer side. 
     As illustrated in  FIG. 2 , the pressure-sensitive sensors  60  and the seal member  70  are attached to a lower surface of the main body portion  31  of the reinforcing member  30  through the gluing agent  33 , and are attached to the support member  80  through the gluing agent  83 . All of the pressure-sensitive sensors  60  and the seal member  70  are disposed on a rear side of the shielding portion  23  of the cover member  20 , and thus the pressure-sensitive sensors  60  and the seal member  70  are not visually recognized to the operator. 
     As illustrated in  FIG. 2 ,  FIG. 6 , and  FIG. 8 , two screw holes  81  are formed in an upper surface of the support member  80  to face the second through-hole  532  in the flange  53  of the display device  50 . Bolts  82  are respectively fixed to the screw holes  81  through the second through-holes  532  of the display device  50 . 
     Each of the bolt  82  has a head portion having an outer diameter which is greater than an inner diameter of the second through-hole  532  of the display device  50 , and a shaft portion having an outer diameter which is smaller than the inner diameter of the second through-hole  532 . By the bolts  82 , the movable unit  10  is restricted from being spaced away from the support member  80  in a predetermined distance or greater while being permitted to slightly move in a vertical direction. According to this, for example, in the case of inverting the electronic apparatus  1 , the movable unit  10  is prevented from being separated from the support member  80 . 
     Next, description will be given of a control system of an electronic apparatus in the present embodiment with reference to  FIG. 9  to  FIG. 13 . 
       FIG. 9  is a block diagram illustrating a control device of the electronic apparatus in the present embodiment, and  FIG. 10  is a circuit diagram illustrating an acquisition unit in the present embodiment,  FIG. 11  and  FIG. 12  are circuit diagrams illustrating a modification example of the acquisition unit in the present embodiment, and  FIG. 13  is a view illustrating pressure-output characteristics of the pressure-sensitive sensor. 
     For example, a control device  90  of the electronic apparatus  1  in the present embodiment is constituted by a computer including a CPU, a ROM, a RAM, various interfaces, and the like, an electric circuit, and the like, and is electrically connected to the touch panel  30  and the pressure-sensitive sensor  60 . As illustrated in  FIG. 9 , the control device  90  functionally includes a touch panel control unit  91  which controls the touch panel  30 , a pressure-sensitive sensor control unit  92  which controls the pressure-sensitive sensor  60 , and an input operation determination unit  100  which determines an input operation to the electronic apparatus  1  on the basis of an output of the control units  91  and  92 . The control device  90  in the present embodiment corresponds to an example of a control unit in the present invention, and the touch panel control unit  91  in the present embodiment corresponds to an example of a detection unit in the present invention. 
     For example, the touch panel control unit  91  periodically applies a predetermined voltage between the first electrode patterns  412  and the second electrode patterns  422  of the touch panel  40 , and detects a position of a finger on the touch panel  40  on the basis of a variation in electrostatic capacitance at each intersection between the first and second electrode patterns  412  and  422 . 
     In the present example, when a value of the electrostatic capacitance reaches a predetermined threshold value or greater, the touch panel control unit  91  detects that a finger of the operator comes into contact with the cover member  20 , and a detection signal is output to the pressure-sensitive sensor control unit  92 . 
     When the touch panel control unit  91  detects that the finger of the operator approaches the cover member  20  in a predetermined distance (a so-called hover state), a detection signal may be output to the pressure-sensitive sensor control unit  92 . 
     As illustrated in  FIG. 9 , the pressure-sensitive sensor control unit  92  includes an acquisition unit  93 , a setting unit  94 , a first calculation unit  95 , a selection unit  96 , a correction unit  97 , a second calculation unit  98 , and a sensitivity adjustment unit  99 . 
     As illustrated in  FIG. 10 , the acquisition unit  93  includes a power supply  931  which is connected in series to the upper electrode  612  (or the lower electrode  622 ) of the pressure-sensitive sensor  60 , and a first resistive element  932  which is connected in series to the lower electrode  622  (or the upper electrode  612 ) of the pressure-sensitive sensor  60 . In a state in which a predetermined voltage is applied between the electrodes  612  and  622  by the power supply  931 , when a load from an upper side to the pressure-sensitive sensor  60  increases, an electrical resistance value between the electrodes  612  and  622  varies in accordance with the size of the load. The acquisition unit  93  periodically samples a voltage value, which corresponds to the resistance variation, from the pressure-sensitive sensor  60  at a constant interval, converts the voltage value into a digital signal with an A/D converter, and outputs the digital signal to the setting unit  94  and the first calculation unit  95 . 
     As illustrated in  FIG. 11 , the acquisition unit  93  may include a second resistive element  933  which is connected in parallel to the pressure-sensitive sensor  60 . In addition, as illustrated in  FIG. 12 , the acquisition unit  93  may include a third resistive element  934  which is connected in series to a parallel circuit which is constituted by the pressure-sensitive sensor  60  and the second resistive element  933 . An output characteristic of the pressure-sensitive sensor  60  can be made to be close to a linear shape by adjusting the resistance value of the first to third resistive elements  932  to  934 . 
     When the detection signal is input from the touch panel control unit  91 , the setting unit  94  sets, as a reference value OP 0 , an output value OP n  of the pressure-sensitive sensor  60  at a predetermined timing. The setting unit  94  is provided for each pressure-sensitive sensor  60 , and sets the reference value OP 0  for each pressure-sensitive sensor  60 . The reference value OP 0  also includes 0 (zero). 
     In a case where the detection signal indicates that contact of the finger with the cover member  20  is detected, the setting unit  94  sets, as the reference value OP 0 , an output value of the pressure-sensitive sensor  60  immediately before detecting the contact (that is, an output value OP n  which is sampled immediately before detecting the contact). 
     In contrast, when the detection signal represents that approaching of the finger to the cover member  20  in a predetermined distance is detected, the setting unit  94  sets, as the reference value OP 0 , an output value of the pressure-sensitive sensor  60  immediately after the detection of the approaching (that is, an output value OP n  which is sampled immediately after the detection of the approaching). 
     When the detection signal represents that the contact of the finger with the cover member  20  is detected, an output value of the pressure-sensitive sensor  60  (that is, an output value OP n  which is sampled simultaneously with the detection of the contact) at a point of time, at which the contact is detected, may be set as the reference value OP 0 . 
     When the detection signal represents that the approaching of the finger to the cover member  20  in a predetermined distance is detected, an output value of the pressure-sensitive sensor  60  (that is, an output value OP n  which is sampled simultaneously with the detection of the approaching) at a point of time, at which the approaching is detected, may be set as the reference value OP 0 . 
     The first calculation unit  95  calculates a first pressure f n , which is applied to the pressure-sensitive sensor  60 , in accordance with the following Expression (1). As is the case with the setting unit  94 , the first calculation unit  95  also provided to each pressure-sensitive sensor  60 , and calculates first pressure f n  for each pressure-sensitive sensor  60 . 
         f   n =OP n −OP 0   (1)
 
     The selection unit  96  selects the minimum value among four reference values OP 0  which are set by the four setting units  94 , and sets, as a comparison value S 0 , the minimum reference value. 
     The correction unit  97  calculates a correction value R n  of each pressure-sensitive sensor  60  in accordance with the following Expression (2) and Expression (3), and corrects first pressure f n  of the pressure-sensitive sensor  60  by using the correction value R n . As is the case with the setting unit  94  or the first calculation unit  95 , the correction unit  97  is also provided for each pressure-sensitive sensor  60 , and corrects the first pressure f n  for each pressure-sensitive sensor  60 . The first pressure f n ′ in the following Expression (3) represents a first pressure after correction. 
         R   n =OP 0   /S   0   (2)
 
         f   n   ′=f   n   ×R   n   (3)
 
     Here, as illustrated in  FIG. 13 , the pressure-sensitive sensor  60  has the following characteristics. That is, the further a pressure increase, the smaller an increase rate of an output value becomes. Accordingly, even in the same pressure variation amount ΔF, the larger an initial load (pressing initiation load) is, the further a variation amount of the output value tends to decrease, and thus a difference in the variation amount of the output value occurs depending on the initial load. 
     Specifically, as illustrated in the same drawing, when pressing is initiated from a first initial load F 1  which is small, the output value of the pressure-sensitive sensor  60  varies by a first variation amount ΔV 1 . In contrast, when pressing is initiated from a second initial load F 2  greater than the first initial load F 1  (F 2 &gt;F 1 ), a variation occurs by only a second variation amount ΔV 2 , and the second variation amount ΔV 2  is narrower than the first variation amount ΔV 1 . (ΔV 2 &lt;ΔV 1 ). 
     A different initial load may be applied to the four pressure-sensitive sensors  60  provided to the electronic apparatus  1  due to the posture of the electronic apparatus  1 , and the like. According to the above-described reason, the first pressure f n , which is calculated by the first calculation unit  95 , greatly depends on the initial load of each of the pressure-sensitive sensors  60 . 
     In contrast, in the present embodiment, since the first pressure f n  is corrected by using the correction value R n  to reduce an effect of the initial load with respect to the first pressure f n , it is possible to realize an improvement in detection accuracy of the pressure-sensitive sensor  60 . 
     As long as the selection unit  96  select any one value among reference values OP 0  as the comparison value S 0 , the selection unit  96  may select, for example, a maximum value among the reference values OP 0  as the comparison value S 0 . 
     A method of correcting the first pressure f n  by the selection unit  96  is not particularly limited to the above-described method as long as the further the reference value OP 0  is greater than the comparison value S 0 , the larger first pressure f n  is corrected, and the further the reference value OP 0  is smaller than the comparison value S 0 , the smaller the first pressure f n  is corrected. 
     The second calculation unit  98  calculates, as a second pressure F n  which is applied to the cover member  20 , the sum of first pressures f n ′ of the four pressure-sensitive sensors  60  after correction in accordance with the following Expression (4). 
         F   n   =Σf   n ′  (4)
 
     The sensitivity adjustment unit  99  performs sensitivity adjustment for the second pressure F n  in accordance with the following Expression (5). In the following expression (5), k adj  represents a coefficient for adjustment of an individual pressure difference of the operator, is stored in advance, for example, in a storage unit (not illustrated in the drawing) of the control device  90 , and can be set by the operator in an arbitrary manner. In the following Expression (5), F n ′ represents a second pressure after the sensitivity adjustment. 
         F   n   ′=F   n   /k   adj   (5)
 
     The input operation determination unit  100  determines an input operation which is intended by the operator on the basis of a position of the finger which is detected by the touch panel control unit  91 , or the second pressure F n ′ which is detected by the pressure-sensitive sensor control unit  92 . 
     Hereinafter, description will be given of a method of detecting a pressure by using the pressure-sensitive sensor in the present embodiment with reference to  FIG. 14 .  FIG. 14  is a flowchart illustrating the method of detecting a pressure in the present embodiment. 
     When control of the electronic apparatus  1  in the present embodiment is initiated, first, in step S 10  of  FIG. 14 , the acquisition unit  93  acquires an output of the four pressure-sensitive sensors  60 , and output the output value OP n  to the setting unit  94  and the first calculation unit  95 . Then, in step S 20 , the setting unit  94  determines whether or not a detection signal is input from the touch panel control unit  91 . 
     As long as contact of the finger of the operation with the cover member  20  is not detected by the touch panel control unit  91  (NO in step S 20  of  FIG. 14 ), step S 10  to Step S 20  are repetitively executed at a constant interval. 
     On the other hand, when the contact of the finger is detected by the touch panel control unit  91  (YES in step S 20  of  FIG. 14 ), in step S 30  of  FIG. 14 , the setting unit  94  sets, as the reference value OP 0 , an output value OP n  which is sampled immediately before detecting the contact. The reference value OP 0  is set for each pressure-sensitive sensor  60 , and thus four reference values OP 0  are set in the present embodiment. 
     When each of the reference values OP 0  is set, in step S 40  of  FIG. 14 , the acquisition unit  93  acquires the output value OP n  of the pressure-sensitive sensor  60 , and in step S 50  of  FIG. 14 , the first calculation unit  95  calculates the first pressure f n  from the output value OP n  and the reference value OP 0  in accordance with Expression (1). The first pressure f n  is also set for each pressure-sensitive sensor  60 . 
     Next, in step S 60  of  FIG. 14 , the selection unit  96  sets, as the comparison value S 0 , the minimum value among the four reference values OP 0 . 
     Next, in step S 70  of  FIG. 14 , the correction unit  97  calculates the correction value R n  of each pressure-sensitive sensor  60  in accordance with Expression (2), and in step S 80  of  FIG. 14 , the correction unit  97  corrects the first pressure f n  by using the correction value R n  in accordance with Expression (3). The correction value R n  is also set for each pressure-sensitive sensor  60 . 
     Next, in step S 90  of  FIG. 14 , the second calculation unit  98  calculates the sum of the first pressure f n ′ of the four pressure-sensitive sensors  60  after correction to obtain the second pressure F n  in accordance with Expression (4). 
     Next, in step S 100  of  FIG. 14 , the sensitivity adjustment unit  99  performs sensitivity adjustment of the second pressure F n  in accordance with Expression (5). The second pressure F n ′ after adjustment is output to the input operation determination unit  100 , and the input operation determination unit  100  determines an input operation, which is performed by the operator with respect to the electronic apparatus  1 , on the basis of the second pressure F n ′ after the adjustment. The step S 100  may be omitted, and in this case, the second pressure F n  which is calculated in step S 90  is output to the input operation determination unit  100 . 
     As long as the contact of the finger continues (YES in step S 110  of  FIG. 14 ), the above-described steps S 40  to S 100  repetitively executed at a constant interval. The step S 60  is executed only at a first time after the detection signal is input from the touch panel control unit  91 . 
     In contrast, when the contact of the finger is not detected by the touch panel control unit  91  (NO in step S 110  of  FIG. 14 ), in step S 120  of  FIG. 14 , the setting of the four reference values OP 0  and the comparison value S 0  is released, and the process returns to step S 10  of  FIG. 14 . 
     As described above, in the present embodiment, since a difference between the output value OP n  of the pressure-sensitive sensor  60  and the reference value OP 0  is calculated as the first pressure f n , it is possible to cancel an effect due to the posture of the electronic apparatus  1  and the like, and it is possible to realize an improvement in pressure detection accuracy by the pressure-sensitive sensor  60 . 
     The above-described embodiment is described for easy understanding of the invention, and is not intended to limit the invention. Accordingly, respective elements, which are disclosed in the above-described embodiment, are intended to include all design modifications or equivalents thereof which pertain to the technical scope of the invention. 
     For example, the second pressure F n  may be calculated by calculating the sum of the first pressure f n , which is calculated by the first calculation unit  95 , instead of the first pressure f n ′ after correction. 
     The first pressure f n ′ after correction may be output to the input operation determination unit  100  instead of the second pressure F n , and the input operation determination unit  100  may determine the input operation on the basis of the first pressure f n ′ after correction. 
     Alternatively, the first pressure f n  may be output to the input operation determination unit  100  instead of the second pressure F n , and the input operation determination unit  100  may determine the input operation on the basis of the first pressure f n . 
     In the above-described embodiment, the pressure-sensitive sensors  60  are disposed at four corners of the electronic apparatus  1 , but there is no particular limitation thereto. For example, in a case where the pressure-sensitive sensor is constituted by using an electrostatic capacitance type sensor, the pressure-sensitive sensor may be constituted by a sheet-shaped electrostatic capacitive sensor, and a transparent elastic member which is provided on the electrostatic capacitive sensor, and the pressure-sensitive sensor may be interposed between the touch panel  40  and the display device  50  with the transparent elastic member disposed on a touch panel  40  side. The pressure-sensitive sensor has substantially the same size as the touch panel  40 , and is laid on the entirety of the rear surface of the touch panel  40 . In the electrostatic capacitive sensor, a plurality of detection regions are divided, and the pressure-sensitive sensor control unit  92  of the control device  90  acquires a detection result from the plurality of detection regions. 
     EXPLANATIONS OF LETTERS OR NUMERALS 
     
         
         
           
               1 : Electronic apparatus 
               10 ,  10 C: Movable unit 
               20 : Cover member 
               30 : Reinforcing member 
               40 : Touch panel 
               50 : Display device 
               60 : Pressure-sensitive sensor 
               70 : Seal member 
               80 : Support member 
               90 : Control device 
               91 : Touch panel control unit 
               92 : Pressure-sensitive sensor control unit 
               93 : Acquisition unit 
               94 : Setting unit 
               95 : First calculation unit 
               96 : Selection unit 
               97 : Correction unit 
               98 : Second calculation unit 
               99 : Sensitivity adjustment unit 
               100 : Input operation determination unit