Patent Publication Number: US-2023147095-A1

Title: Image forming device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-181147, filed Nov. 5, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to an image forming device. 
     BACKGROUND 
     An image forming device including a sensor (“human sensor”) to detect the presence of a person is known. The image forming device including a human sensor can be switched to a power saving mode when not used for a long time, and then returned to a normal mode when a person is detected by the human sensor. Accordingly, power consumption can be reduced, and the apparent return time to the normal mode from a power saving mode is shortened for the user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an image forming device according to an embodiment. 
         FIG.  2    is a perspective view of another image forming device according to an embodiment. 
         FIG.  3    is a block diagram of an image forming device according to an embodiment. 
         FIG.  4    depicts a human sensor unit as viewed from a front side. 
         FIG.  5    depicts a left end portion of a human sensor unit as viewed from a rear side. 
         FIG.  6    depicts a slider and a slider support unit as viewed from a rear side. 
         FIG.  7    is an enlarged perspective view of a sensor cover for an image forming device depicted in  FIG.  1   . 
         FIG.  8    is cross-sectional view of a sensor cover and an operator element. 
         FIG.  9    depicts a human sensor unit in states in which a detection distance has been adjusted to a close distance, a normal distance, and a long distance. 
         FIG.  10    are side views of a slider and a substrate holder in different states. 
         FIG.  11    are side views of a human sensor in different states. 
         FIG.  12    are side views of an image forming device in different states. 
         FIG.  13    depicts aspects of a detection window formed in a sensor cover. 
         FIG.  14    depicts aspects of a sensor cover and a detection window according to a modification. 
         FIG.  15    is a diagram illustrating a combination of a human sensor unit and a sensor cover. 
         FIG.  16    is a diagram illustrating a combination of a human sensor unit and another sensor cover. 
         FIG.  17    is a perspective view of an option unit including a human sensor unit and a sensor cover. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an image forming device that allows a user to adjust a detection distance of a human sensor is provided. 
     According to one embodiment, an image forming device includes a human sensor configured to detect a person in front of the image forming device, an adjustment mechanism configured to move the human sensor to adjust a detection distance of the human sensor, and a sensor cover panel on an exterior of the image forming device. The sensor cover panel is configured to cover the human sensor and the adjustment mechanism when installed on the image forming device. The adjustment mechanism includes an operator element manually operable by a user to adjust the detection distance. The human sensor and the adjustment mechanism are disposed behind the sensor cover panel. The sensor cover panel has a detection window through which a detection wave for the human sensor can pass. The sensor cover panel also has an opening through which the operator element is exposed so as to be seen by a user from both the front side and a lateral side of the image forming device. 
     Hereinafter, certain examples of an image forming device according to an embodiment will be described with reference to drawings.  FIG.  1    is a perspective view of an image forming device  10  of a first type according to an embodiment.  FIG.  2    is a perspective view of an image forming device  10  of a second type according to an embodiment. 
     In each of the drawings, the depicted dimensions, scales, and relative dimensions of each depicted element, component, unit, aspect, or the like may be appropriately changed. In addition, the drawings, certain aspects of configuration may be omitted for the purpose of description. 
     In order to define directions for purposes of description, an XYZ orthogonal coordinate system is set as illustrated in  FIGS.  1  and  2   . The Z direction may be referred to as a vertical direction, a longitudinal direction, or an upper-lower direction. A+Z direction is an upper side (upward) direction, and a −Z direction is a lower side (downward) direction. An X direction and a Y direction may be referred to as a horizontal direction or a transverse direction. In general, the Y direction is taken as a depth direction or a front-rear direction of the image forming device  10 . A+Y direction referred to as a front side (frontward) direction, and a −Y direction referred to as a rear side (rearward) direction. The X direction is taken as a width direction or a left-right direction of the image forming device  10 . The left-right direction is based on a case of viewing the image forming device  10  from the front side, a +X direction referred to as a right side (rightward) direction, and a −X direction referred to as a left side (leftward) direction. The right side or the left side is also referred to as a lateral side. In the following description, all expressions regarding directions follow the XYZ orthogonal coordinate system, but the establishment of the coordinate system is not a limitation. 
     Regarding the image forming device  10  of the first type in  FIG.  1    and the image forming device  10  of the second type in  FIG.  2   , certain device details are different, but basic configurations are the same overall. Therefore, in the following description, the two image forming devices  10  are described using a same reference numeral without being distinguished from each other. 
     The image forming device  10  is, for example, a multi function peripheral (MFP), and has a plurality of functions, for example, a print function, a scan function, and a copy function. 
     The image forming device  10  includes an operation panel  11  (input panel), a scanner unit  12  (a scanner), an image forming unit  13  (a printer), a sheet feeding unit  14 , a sheet discharge unit  15  (sheet discharge tray), and a human sensor unit  16 . 
     The operation panel  11  is disposed on, for example, an upper and front side of the image forming unit  13 . The operation panel  11  receives an execution instruction (operation instruction) and setting information for various functions of the image forming device  10 . For example, the operation panel  11  includes a touch panel, a push button, and the like. The operation panel  11  is disposed at a height at which a person of an average height can easily operate the operation panel  11 . 
     The scanner unit  12  is disposed at, for example, a position located on the upper side of the image forming unit  13  and a rear side of the operation panel  11 . The scanner unit  12  uses a sensor such as a contact image sensor (CIS) or a charge coupled device (CCD) to read an image recorded on a document or the like and generate image data accordingly. 
     The sheet feeding unit  14  includes sheet feeding cassettes  21  in which sheets are accommodated, and feeds a sheet from one of the sheet feeding cassettes  21  to the image forming unit  13 . 
     The image forming unit  13  is disposed on an upper portion of the sheet feeding unit  14 . The image forming unit  13  forms, based on the image data read by the scanner unit  12  or image data received from an external device, an image on the sheet fed from the sheet feeding unit  14  by using toner. Therefore, the image forming unit  13  includes a photoreceptor unit, a toner unit, and the like. The image forming unit  13  discharges the sheet on which the image has been formed toward the left side and to the sheet discharge unit  15 . 
     The sheet discharge unit  15  receives and stores the sheet on which the image has been formed from the image forming unit  13 . 
     The human sensor unit  16  is disposed near the upper side of the image forming unit  13 . The human sensor unit  16  detects a person within a fixed range in the front of the image forming device  10 . The human sensor unit  16  can adjust the maximum distance (hereinafter, referred to as a detection distance) in front of the image forming unit at which a person can be detected. 
     The human sensor unit  16  is disposed to a lateral side, for example, the left side of the operation panel  11 . The human sensor unit  16  is generally disposed at substantially the same height as the operation panel  11 . Here, the matter that the human sensor unit  16  is disposed at substantially the same height as the operation panel  11  means that, for example, a height range occupied by the human sensor unit  16  and a height range occupied by the operation panel  11  at least partially overlap. 
     The image forming device  10  includes a cover for an exterior. The image forming device  10  of the first type depicted in  FIG.  1    includes a first front cover  22 , a second front cover  23 , and a sensor cover  24 . The image forming device  10  of the second type depicted in  FIG.  2    does not include the first front cover  22 , but does include the second front cover  23  and the sensor cover  24 . 
     The sensor cover  24  covers the human sensor unit  16 . In the image forming device  10  in  FIG.  1   , the first front cover  22  and the second front cover  23  cover the image forming unit  13 . In the image forming device  10  in  FIG.  2   , just the second front cover  23  covers the image forming unit  13 . 
     The first front cover  22  can be fixed without being openable and closable by a user in normal operation. The second front cover  23  is openable and closable for, for example, replacement of the toner unit or the photoreceptor unit, dealing with sheet jams, and maintenance. 
     In a state in which all of the sheet feeding cassettes  21  and the second front cover  23  are closed, the image forming unit  13  and the sheet feeding unit  14  form a substantially rectangular parallelepiped housing. 
     As compared with the image forming device  10  of the second type in  FIG.  2   , the image forming device  10  of the first type in  FIG.  1    needs a larger installation area and is a device of a large type. In other words, as compared with the image forming device  10  in  FIG.  1   , the image forming device  10  in  FIG.  2    needs a smaller installation area and is a device of a small type. 
     In the image forming device  10  in  FIG.  1   , the sheet feeding unit  14  includes four sheet feeding cassettes  21 , and on the upper side of the image forming unit  13 , the sheet discharge unit  15  is provided on a left side of the scanner unit  12 . The operation panel  11  is disposed near a center along the width direction. The human sensor unit  16  can be disposed frontward of the operation panel  11 . 
     The first front cover  22  and the second front cover  23  constitute parts of a front panel. Front surface portions of the sheet feeding cassettes  21  also constitute a part of the front panel. The first front cover  22 , the second front cover  23 , and the front surface portions of the sheet feeding cassettes  21  can be, for example, substantially flush with each other and are parallel with each other along a ZX plane, when all of the sheet feeding cassettes  21  and the second front cover  23  are closed. 
     A front surface portion of the sensor cover  24  is substantially flush with at least a part of, the first front cover  22 , the second front cover  23 , and the front surface portions of the sheet feeding cassettes  21  in a closed state, and is along the same ZX plane. 
     On the other hand, in the image forming device  10  in  FIG.  2   , the sheet feeding unit  14  includes two sheet feeding cassettes  21 , and the sheet discharge unit  15  is provided between the scanner unit  12  and the image forming unit  13 . The operation panel  11  is disposed near a right side in the width direction. The human sensor unit  16  is disposed rearward of the operation panel  11 . 
     The second front cover  23  constitutes a part of a front panel. The front surface portions of the sheet feeding cassettes  21  also constitute a part of the front panel. The second front cover  23  and the front surface portions of the sheet feeding cassettes  21  are, for example, substantially flush with each other and parallel along a ZX plane, when all of the sheet feeding cassettes  21  and the second front cover  23  are closed. 
     The front surface portion of the sensor cover  24  is substantially flush with at least a part of, the second front cover  23  and the front surface portions of the sheet feeding cassettes  21  in a closed state, and is along the same ZX plane. 
     The image forming device  10  in  FIG.  2    includes a card reader  26 . The card reader  26  receives user authentication information from an ID card or the like. The card reader  26  is disposed between the operation panel  11  and the human sensor unit  16  in the width direction, and is disposed at substantially the same height as the operation panel  11 . 
       FIG.  3    is a block diagram of the image forming device  10 . The image forming device  10  includes the operation panel  11 , the scanner unit  12 , the image forming unit  13 , the sheet feeding unit  14 , the human sensor unit  16 , and a control unit  17 . 
     The control unit  17  controls overall operations of the image forming device  10 . The control unit  17  includes a central processing unit (CPU)  18 , a memory  19 , and an auxiliary storage device  20 . 
     The auxiliary storage device  20  permanently stores a program and data necessary for executing various functions of the image forming device  10 . 
     The memory  19  includes a random access memory (RAM) and the like. The memory  19  temporarily stores a program and data necessary for processing executed by the CPU  18 . 
     The CPU  18  receives information from the operation panel  11  and the human sensor unit  16 , reads the necessary program and data from the auxiliary storage device  20  into the memory  19 , and executes the program to control the scanner unit  12 , the image forming unit  13 , and the sheet feeding unit  14 . 
     For example, the control unit  17  switches an operation of the image forming device  10  to an operation in a power saving mode when the image forming device  10  is not used for a long time and to an operation in a normal mode when a person is detected by the human sensor unit  16 . 
     Next, the human sensor unit  16  will be described with reference to  FIGS.  4  to  6   .  FIG.  4    is a perspective view of the human sensor unit  16  as viewed from the front side.  FIG.  5    is a perspective view of a left end portion of the human sensor unit  16  as viewed from the rear side.  FIG.  6    is a perspective view of a slider  47  and a slider support unit  48  as viewed from the rear side. 
     The human sensor unit  16  includes a human sensor  31  that detects a person and an adjustment mechanism  35  that adjusts the detection distance of the human sensor  31 . 
     The human sensor  31  is, for example, a pyroelectric infrared sensor. The pyroelectric infrared sensor uses a pyroelectric effect of pyroelectric ceramics to detect an infrared ray emitted by a person as thermal energy. The human sensor  31  can also detect an object other than a person, but here, the human sensor  31  is referred to as a human sensor for convenience. 
     The human sensor  31  is mounted on a substrate  32  (e.g., circuit board) on which necessary wiring and the like is formed. The human sensor  31  is vertically mounted with respect to a surface of the substrate  32 . The wiring of the substrate  32  is electrically connected to the control unit  17 . The human sensor  31  sends a detection signal to the control unit  17  via such wiring. 
     The human sensor  31  includes a receiving surface on which a detection wave is received. The human sensor  31  detects a person by receiving the detection wave from a person within a predetermined spatial spread range that is centered on an axis orthogonal to the receiving surface. 
     In the following description, a direction of the axis orthogonal to the receiving surface of the human sensor  31  is referred to as the detection direction of the human sensor  31  for convenience. The range within which the human sensor  31  can detect a person is referred to as the detection range of the human sensor  31  for convenience. The detection range of the human sensor  31  extends, for example, in a conical shape starting from the receiving surface expanding along the detection direction. 
     The adjustment mechanism  35  adjusts the detection distance of the human sensor  31  by changing the detection direction of the human sensor  31 . Specifically, the adjustment mechanism  35  swingably supports the human sensor  31  around an axis extending in the left-right direction, and adjusts the detection distance of the human sensor  31  by changing the detection direction. 
     The adjustment mechanism  35  includes a substrate holder  41  that holds the substrate  32  and a frame  43  that swingably supports the substrate holders  41 . The frame  43  includes a pair of support shafts  44  provided coaxially at left and right end portions. The substrate holder  41  extends in the left-right direction beyond a width (transverse dimension) of the substrate  32 , and includes the pair of shaft engaging portions  42  at the left and right end portions, which are to be engaged with the pair of support shafts  44  of the frame  43 . Accordingly, the substrate holder  41  is swingable around the support shafts  44  of the frame  43 , and the detection direction (pointing angle) of the human sensor  31  is changed according to the swing (angle) of the substrate holder  41 . That is, the substrate holder  41  and the frame  43  constitute a swing support mechanism  40  that swingably supports the substrate  32 . 
     The adjustment mechanism  35  includes an operator element  45  (also referred to as “operator  45 ”) that can be manually operated by the user to adjust the detection distance of the human sensor  31 . The operator  45  is provided at a left end portion. The operator  45  has a protrusion  46  for ease of operation by the user. The operator  45  is slidable (moveable) in the upper-lower direction. 
     The adjustment mechanism  35  includes a slider  47  to which the operator  45  is fixed. The frame  43  includes a slider support unit  48  at the left end portion. The slider support unit  48  slidably supports the slider  47  in the upper-lower direction. The slider  47  and the slider support unit  48  constitute a support mechanism that slidably supports the operator  45  in the upper-lower direction. 
     As illustrated in  FIG.  5   , the substrate holder  41  has a cylindrical boss  51  that extends to the left side through an opening  52  formed in the slider support unit  48 . The slider  47  has a rectangular hole  53  that receives a left end portion of the boss  51 . Therefore, the boss  51  is moved in the upper-lower direction in response to sliding of the slider  47  in the upper-lower direction. Accordingly, the substrate holder  41  can be swung around the support shafts  44  of the frame  43 , with which the shaft engaging portions  42  at the left and right end portions of the substrate holder  41  are engaged. As a result, the detection direction of the human sensor  31  is changed. That is, the cylindrical boss  51  of the substrate holder  41  and the rectangular hole  53  of the slider  47  constitute a conversion mechanism that converts the movement in the upper-lower direction of the slider  47  into a swing of the substrate holder  41 , and the swing changes the detection direction of the human sensor  31 . 
     The operator  45  can be positioned at a plurality of positions. As seen in  FIG.  6   , the slider  47  includes a cantilever  56  that is elastically deformable. The cantilever  56  includes, at a free end portion of the cantilever  56 , a claw  57  protruding to the right side. The slider support unit  48  includes a claw receiving part  58  having a plurality of recesses  59  that receive the claw  57 . 
     The claw  57  of the cantilever  56  moves on the claw receiving part  58  of the slider support unit  48  as the slider  47  slides in the upper-lower direction. The cantilever  56  is elastically deformed when the claw  57  is located between the recesses  59 . The cantilever  56  recovers from deformation when the claw  57  is located in one of the recesses  59 . The claw  57  engages with this recess  59  while the claw  57  is urged towards the recess  59  by an elastic restoring force of the cantilever  56 . Accordingly, movement of the claw  57  of the cantilever  56  is restricted. As a result, the operator  45  is positioned at one of the plurality of available positions (corresponding to the recesses  59 ). That is, the cantilever  56  of the slider  47  and the claw receiving part  58  of the slider support unit  48  constitute a positioning mechanism  55  that positions the operator  45  at any of a plurality of positions. 
     With respect to an operation to the operator  45  by a small force that is insufficient to release engagement between the claw  57  and the recess  59  against the restoring force of the cantilever  56 , the positioning mechanism  55  maintains the engagement between the claw  57  and the recess  59 , prevents the operator  45  from sliding, and keeps the operator  45  at the present position. 
     On the other hand, with respect to an operation to the operator  45  by a large force that is sufficient to release the engagement between the claw  57  and the recess  59  against the restoring force of the cantilever  56 , the positioning mechanism  55  allows the operator  45  to slide. 
     The claw receiving part  58  has three recesses  59  in this example. Therefore, the operator  45  can be positioned in three steps (stages). The human sensor unit  16  adjusts the detection distance to a close distance when the claw  57  is engaged with the recess  59  at an upper portion. The human sensor unit  16  adjusts the detection distance to a normal distance when the claw  57  is engaged with the recess  59  at a center. The human sensor unit  16  adjusts the detection distance to a long distance when the claw  57  is engaged with the recess  59  at a lower portion. 
     The number of the recesses  59  of the claw receiving part  58  is an example and is not limited to three, and the number of the recesses  59  may be any other suitable number. 
     Next, the sensor cover  24  of the image forming device  10  of the first type in  FIG.  1    will be representatively described.  FIG.  7    is a perspective view of the sensor cover  24 . The sensor cover  24  is an exterior cover that covers the human sensor unit  16 . The human sensor unit  16  is disposed within a height range of the sensor cover  24 . 
     The sensor cover  24  is disposed at, for example, a position on a front and left side of the image forming device  10 . In order to define a space in which the human sensor unit  16  is housed, the sensor cover  24  includes a front surface portion  61  that faces frontward, a rearward extending portion  62  that extends toward the rear side from a left end of the front surface portion  61 , and an upper surface portion  63  that extends horizontally from upper ends of the front surface portion  61  and the rearward extending portion  62 . 
     The sensor cover  24  has a detection window  71  through which the detection wave, for example, the infrared ray for the human sensor  31  passes, and an opening  73  through which the operator  45  of the adjustment mechanism  35  is exposed. The detection window  71  and the opening  73  are commonly formed with the sensor cover  24 , and therefore, the sensor cover  24  can be formed at low cost. 
     The detection window  71  is formed in a left portion relative to a center of the front surface portion  61  in the left-right direction. Further, the detection window  71  is formed in a lower portion relative to a center of the front surface portion  61  in the upper-lower direction. The detection window  71  has a plurality of slits  72  that extend in the width direction. 
     The opening  73  is formed in the rearward extending portion  62 . The rearward extending portion  62  is curved outward. The rearward extending portion  62  forms a curved corner portion on the front and left side of the image forming device  10 . The opening  73  has a height corresponding to the sliding amount (movement range) of the operator  45  in the upper-lower direction. That is, a height dimension of the opening  73  is larger than a sum of a height of the protrusion  46  of the operator  45  and the sliding amount of the operator  45  in the upper-lower direction. A transverse dimension along an outer surface of the rearward extending portion  62  for the opening  73  is larger than that of the protrusion  46  of the operator  45 . 
     The human sensor unit  16  is disposed in a space that is defined by the front surface portion  61 , the rearward extending portion  62 , and the upper surface portion  63  of the sensor cover  24 . That is, the human sensor unit  16  is disposed behind the front surface portion  61  of the sensor cover  24 . Further, the human sensor unit  16  is disposed near the rearward extending portion  62 . 
     The human sensor  31  is disposed behind the detection window  71 . As illustrated in  FIG.  1   , the operator  45  of the adjustment mechanism  35  is exposed through the opening  73  of the rearward extending portion  62 . That is, the operator  45  is disposed on a sheet discharge direction side of the image forming device  10 . 
       FIG.  8    is a cross-sectional view of the operator  45  and the sensor cover  24  with the human sensor unit  16  being covered by the sensor cover  24 , that is, in the state illustrated in  FIG.  1   . As is clear from  FIGS.  1  and  8   , the operator  45  of the human sensor unit  16  can be seen from both the front side and the lateral side through the opening  73  of the rearward extending portion  62 . 
     As illustrated in  FIG.  8   , the operator  45  does not protrude beyond the sensor cover  24 . That is, the operator  45 , including the protrusion  46 , is disposed inward of the outer surface of the rearward extending portion  62 . 
     Aspects of the adjustments of the detection distance of the human sensor  31  in the human sensor unit  16  will be described with reference to  FIGS.  9  to  12   . States in which the detection distance of the human sensor  31  is adjusted to the close distance, the normal distance, and the long distance are depicted in each of  FIGS.  9  to  12   .  FIG.  9    depicts perspective views of the human sensor unit  16 .  FIG.  10    depicts side views of the slider  47  and the substrate holder  41 .  FIG.  11    depicts side views of the human sensor  31 .  FIG.  12    depicts side views of the image forming device  10 . 
     In  FIG.  9   , a state in which the detection distance is adjusted to the close distance is depicted in an upper drawing portion, a state in which the detection distance is adjusted to the normal distance is depicted in a middle drawing portion, and a state in which the detection distance is adjusted to the long distance is depicted in a lower drawing portion. In each of  FIGS.  10  to  12   , the state in which the detection distance is adjusted to the close distance is depicted in a right drawing portion, the state in which the detection distance is adjusted to the normal distance is depicted in a middle drawing portion, and the state in which the detection distance is adjusted to the long distance is depicted in a left drawing portion. 
     When detection distance is adjusted to the close distance, as illustrated in the upper drawing of  FIG.  9    and the right drawing of  FIG.  10   , the operator  45  and the slider  47  are positioned on an upper step of the three steps, the claw  57  of the cantilever  56  of the slider  47  is engaged with the recess  59  at the upper portion (see  FIG.  6   ), and the substrate  32  is horizontally disposed. Therefore, as illustrated in the right drawing of  FIG.  11   , a detection direction Da of the human sensor  31  faces downwardly, and a detection range Ra of the human detection sensor  31  extends in the conical shape around the detection direction Da facing downwardly. 
     The range within which the human sensor  31  can actually detect a person is a part of the detection range Ra which extends through the detection window  71  of the sensor cover  24 . As a result, as illustrated in the right drawing of  FIG.  12   , the detection distance of the human sensor  31  is close distance La. In  FIG.  12   , an arrow A indicates a boundary of the range within which a person can be detected by the human sensor  31  through the detection window  71  on a plane extending in the upper-lower direction and the front-rear direction. 
     When the operator  45  is slid towards the lower side to shift from the state illustrated in the upper drawing of  FIG.  9    to the state illustrated in the middle drawing of  FIG.  9   , the slider  47  is accordingly slid towards the lower side to shift from the state illustrated in the right drawing of  FIG.  10    to the state illustrated in the middle drawing of  FIG.  10   . Accordingly, the boss  51  of the substrate holder  41  to be engaged with the rectangular hole  53  of the slider  47  is moved to the lower side. Accordingly, the substrate holder  41  is rotated counterclockwise about the support shafts  44  of the frame  43 , with which the shaft engaging portions  42  of the substrate holder  41  are engaged. As a result, the detection direction of the human sensor  31  is rotated from the lower side towards the front side. 
     When the claw  57  of the cantilever  56  of the slider  47  is engaged with the recess  59  at the center (see  FIG.  6   ), as illustrated in the middle drawing of  FIG.  9    and the middle drawing of  FIG.  10   , the operator  45  and the slider  47  are positioned on a middle step of the three steps, and shift to the state in which the detection distance is adjusted to the normal distance. In this state, as illustrated in the middle drawing of  FIG.  11   , a detection direction Db of the human sensor  31  faces downwardly but more to the front than before, and a detection range Rb of the human sensor  31  extends in the conical shape around the detection direction Db which is angled with respect to the vertical direction. 
     The range within which the human sensor  31  can actually detect a person is the part of the detection range Rb that extends through the detection window  71  of the sensor cover  24 . As a result, as illustrated in the middle drawing of  FIG.  12   , the detection distance of the human sensor  31  becomes normal distance Lb. 
     When the operator  45  is slid towards the lower side to shift from the state illustrated in the middle drawing of FIG.  9  to the state illustrated in the lower drawing of  FIG.  9   , the slider  47  is accordingly slid towards the lower side to shift from the state illustrated in the middle drawing of  FIG.  10    to the state illustrated in the left drawing of  FIG.  10   . Accordingly, the boss  51  of the substrate holder  41  is moved towards the lower side by the slider  47 , the substrate holder  41  is rotated counterclockwise about the support shafts  44  of the frame  43 , and the detection direction of the human sensor  31  is further rotated towards the front side. 
     When the claw  57  of the cantilever  56  of the slider  47  is engaged with the recess  59  at the lower portion (see  FIG.  6   ), as illustrated in the lower drawing of  FIG.  9    and the left drawing of  FIG.  10   , the operator  45  and the slider  47  are positioned on a lower portion of the three steps, and shift to the state in which the detection distance is adjusted to the long distance. In this state, as illustrated in the left drawing of  FIG.  11   , a detection direction Dc of the human sensor  31  further faces more frontward than the detection direction Db, and a detection range Rc of the human sensor  31  extends in the conical shape around the detection direction Dc facing more frontward than before. 
     The range within which the human sensor  31  can actually detect a person is the part of the detection range Rc that extends through the detection window  71  of the sensor cover  24 . As a result, as illustrated in the left drawing of  FIG.  12   , the detection distance of the human sensor  31  becomes long distance Lc. 
     Operations of sliding the operator  45  towards the lower side from an upper position is described above, but operations of sliding the operator  45  towards the upper side from a lower position may be easily inferred from the above description. 
     Next, a structure of the detection window  71  formed in the sensor cover  24  will be described with reference to  FIG.  13   .  FIG.  13    includes a side cross-sectional view and a front view of the detection window  71 . The side cross-sectional view of the detection window  71  is illustrated on the left, and the front view of the detection window  71  is illustrated on the right. Although not illustrated in  FIG.  13   , the human sensor  31  is disposed on the rear side of the detection window  71 . 
     As illustrated in  FIG.  13   , the detection window  71  is formed in the lower portion of the front surface portion  61  that faces the front side. The detection window  71  has a plurality of slits  72 . Three slits  72  are depicted in  FIG.  13   . The slits  72  extend in the width direction and are one above the other in the vertical direction. 
     No optical component (e.g., lens, filter, or the like) to pass the detection wave is disposed in front of the human sensor  31 . Therefore, the human sensor  31  is not affected by reflection, refraction, or the like of the detection wave by any optical component that might otherwise be positioned on the front side of the human sensor  31 . Since the detection wave is received directly by the human sensor  31  without passing through an optical component, the human sensor  31  is useful for efficiently detecting a person. The detection window  71  has a plurality of slits  72 , and thus is useful for obtaining a long detection distance. Each slit  72  is a size at which entry of a finger, a pen, or the like is prevented. Therefore, it is possible to prevent fingers, pens, or the like from unintentionally or inadvertently touching the human sensor  31 , and it is possible to avoid damage to the human sensor  31 . 
     The lowermost slit  72  is open towards the lower side direction. That is, the lowermost slit  72  is formed at a lower end of the front surface portion  61  of the sensor cover  24 . Therefore, dust is not accumulated in the lowermost slit  72 . In addition, entry of the dust into the sensor cover  24  is also reduced. 
     Next, structures of a sensor cover  24  and a detection window  71  according to a modification will be described with reference to  FIG.  14   .  FIG.  14    includes a side cross-sectional view and a front view of the detection window  71 . The side cross-sectional view of the detection window  71  is illustrated on the left, and the front view of the detection window  71  is illustrated on the right. 
     As illustrated in  FIG.  14   , the detection window  71  has three slits  72 . The slits  72  extend in the width direction. Each slit  72  has a size at which entry of a finger, pen, or the like is prevented. Advantages and the like obtained by the structure of the detection window  71  provided with the slits  72  are similar to those in the case of  FIG.  13   . 
     The sensor cover  24  includes a front surface portion  61  that faces frontward and a lower surface portion  64  that faces downward. The lower surface portion  64  is continuous with the front surface portion  61 , and extends obliquely toward the rear side from a lower end of the front surface portion  61 . 
     The two upper slits  72  are formed in the front surface portion  61 . The lowermost slit  72  is formed in the lower surface portion  64 . The lowermost slit  72  is open towards the lower side (downward). Therefore, the dust is not accumulated in the lowermost slit  72 . In addition, the entry of the dust into the sensor cover  24  is also reduced. 
     Next, the combination of the human sensor unit  16  and the sensor cover  24  will be described with reference to  FIGS.  15  and  16   .  FIGS.  15  and  16    depict the human sensor unit  16  and the sensor cover  24  as viewed from the upper side. In  FIGS.  15  and  16   , just the human sensor  31 , the substrate  32 , and the substrate holder  41  of the human sensor unit  16  are depicted for explanatory simplicity. 
     In  FIGS.  15  and  16   , the human sensor unit  16  is the same in each, but the sensor covers  24  are different for each. Specifically, a first combination example of the human sensor unit  16  and the sensor cover  24  illustrated in  FIG.  15    and a second combination example of the human sensor unit  16  and the sensor cover  24  illustrated in  FIG.  16    are different in a width of the slits  72  formed in the sensor cover  24 . In  FIGS.  15  and  16   , only one slit  72  is depicted for convenience, but a plurality of slits  72  can be considered present. 
     In the example of  FIG.  15   , the slit  72  formed in the sensor cover  24  has a width Wa. The width Wa does not block the detection range Rd of the human sensor  31  in the transverse direction. 
     On the other hand, in the example of  FIG.  16   , the slit  72  formed in the sensor cover  24  has a width Wb (narrower than the width Wa). The width Wb partially blocks the detection range Rd of the human sensor  31  and thus limits the detection range Rd to a detection range Re in the transverse direction. 
     Therefore, a range in the transverse direction within which the human sensor unit  16  can actually detect a person through the slit  72  in the combination example of  FIG.  15    is wider than that in the combination example of  FIG.  16   . 
     An appropriate detection range in the transverse direction of the human sensor unit  16  can be determined according to a use, experiment, or the like. For example, the example of  FIG.  15    in which the detection range in the transverse direction is wide may be adopted for the image forming device  10  of the large type illustrated in  FIG.  1   , and the example of  FIG.  16    in which the detection range in the transverse direction is narrow may be adopted for the image forming device  10  of the small type illustrated in  FIG.  2   . 
     Next, an option unit  80  (also referred to as an “optional unit  80 ” or “add-on unit  80 ”) including a human sensor unit  16  and a sensor cover  24  will be described with reference to  FIG.  17   .  FIG.  17    is a perspective view of the option unit  80 . 
     In general, the image forming device  10  may have different mounted functions depending on a difference in model or the like even if the general type is the same. For example, some versions of an image forming device  10  may not include the human sensor unit  16  or may not include the card reader  26  according to user preference. In addition, in some instances, the necessity of functions corresponding to those related to a human sensor  16  and/or card reader  26  might not be apparent initially to a user, but use or the like may generate a demand to add these functions subsequently. 
     The option unit  80  responds to such a demand. The option unit  80  includes the human sensor unit  16  and the sensor cover  24 . The sensor cover  24  has the detection window  71  for the human sensor  31  of the human sensor unit  16 , and the opening  73  for the operator  45  of the human sensor unit  16 . The sensor cover  24  further incorporates a card reader  26 . 
     Even if the image forming device  10  is a basic model having just the minimum functions, it is common that the wiring necessary for those units or the like mounted on a higher model will anyways be incorporated in the image forming device  10  from the start even though the higher model units are not themselves provided with the basic model. The human sensor unit  16  includes a mounting portion  81  for mounting of the human sensor unit  16  to the sensor cover  24  and for connection of wiring of the image forming device  10 . 
     Therefore, the user can easily add a desired function to the image forming device  10  by removing the existing cover to be replaced with the sensor cover  24 , connecting the wiring for the human sensor unit  16 , and mounting the human sensor unit  16  and the sensor cover  24  to the image forming device  10 . 
     According to the image forming device  10  of the embodiment described above, since the operator  45  that adjusts the detection distance of the human sensor  31  is exposed through the opening  73  of the sensor cover  24  on the sheet discharge direction side so as to be seen from both the front side and the lateral side, the user can adjust the detection distance of the human sensor  31 . 
     The human sensor unit  16  is disposed at substantially the same height as the operation panel  11 . Therefore, the operator  45  is disposed at a height at which the operator  45  can be easily operated by a user. Accordingly, the user can easily operate the operator  45  without greatly changing a posture. 
     The operator  45  is slidable in the upper-lower direction. Therefore, the detection distance of the human sensor  31  can be adjusted by a simple operation. It is possible to visually grasp a current adjustment state of the detection distance of the human sensor  31  based on a position of the protrusion  46  in the upper-lower direction. 
     Since the operator  45  is disposed on the sheet discharge direction side, the operator  45  is relatively distant from the operation panel  11 . Therefore, it is possible to avoid a situation in which the operator  45  is erroneously moved during an operation on the operation panel  11 . It is possible to efficiently operate the operation panel  11  and the operator  45  without worrying about making a mistake. For example, it is possible to slide the operator  45  with a left hand while operating the operation panel  11  with a right hand. 
     The operator  45  is exposed through the opening  73  formed in the rearward extending portion  62  of the sensor cover  24  so as to be seen from both the front side and the lateral side. Therefore, it is easy to access the operator  45  when operating the operator  45 . In addition, it is possible to easily find the operator  45 , and the user does not get confused about finding the operator  45 . 
     The operator  45  does not protrude from the sensor cover  24 . Therefore, unintended and inadvertent contact with the operator  45  is less likely. Accordingly, undesired changes in the detection distance of the human sensor  31  are reduced. 
     The operator  45  can be positioned at a plurality of positions. Therefore, it is possible to prevent the operator  45  from being slid and the detection distance of the human sensor  31  being undesirably changed due to light contact with the operator  45 . 
     In an embodiment, the operator  45  is slidable in the upper-lower direction, but embodiments are not limited thereto. In general, as long as the operator  45  can be manually operated by the user, the operator  45  may adopt another basic structure, for example, a rotary dial. Preferably, a mark is attached to the rotary dial so that the presently set detection distance of the human sensor  31  can be seen. 
     The adjustment mechanism  35  has a configuration in which the detection distance of the human sensor  31  is adjusted by changing the detection direction of the human sensor  31 , but is not limited thereto, and may have other configurations. For example, the adjustment mechanism  35  may have a configuration in which the detection distance of the human sensor  31  is adjusted by providing a slider or the like in the human sensor  31  and changing a position of the slider. 
     While certain embodiments of the disclosure have been described, these embodiments are presented as examples and are not intended to limit the scope of the disclosure. These novel embodiments are capable of being implemented in various forms, and various omissions, substitutions, and modifications may be made without departing from the scope of the disclosure. The embodiments and the modification thereof are included in the scope and the spirit of the disclosure and are also included in the disclosure described in the scope of claims and an equivalent scope thereof.