Patent Publication Number: US-8115162-B2

Title: Sliding door apparatus and elevator including an obstruction detection system

Description:
TECHNICAL FIELD 
     The present invention relates to a sliding door apparatus that automatically moves a door horizontally, and to an elevator that makes use thereof. 
     BACKGROUND ART 
     In conventional sliding door apparatuses, a light emitter that has a long and continuous light-emitting surface is disposed on either a left or a right vertical frame of an entrance, and a camera that captures an image of the light-emitting surface is also disposed on a vertical frame that faces the light emitter (see Patent Document 1, for example).
     Patent Document 1: Japanese Patent Laid-Open No. 2004-338846   

     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     In conventional sliding door apparatuses such as that described above, since the light emitter and the camera are disposed on the vertical frames, when portions of passengers or baggage approach the door, they may be detected as obstructions even if they are not really positioned so as to be caught in the door. For this reason, if such sliding door apparatuses are used in elevators, the doors may be reversed and opened many times during closing, reducing operating efficiency. In order to detect obstructions from a side near a landing, it is also necessary to install light emitters and cameras on the landing of every floor, increasing costs. 
     The present invention aims to solve the above problems and an object of the present invention is to provide a sliding door apparatus that can more reliably detect an obstruction that would actually be caught in a door, and to an elevator that makes use thereof. 
     Means for Solving the Problem 
     In order to achieve the above object, according to one aspect of the present invention, there is provided a sliding door apparatus including: a first door that opens and closes a first entrance by being slid horizontally; a second door that opens and closes a second entrance that faces the first entrance by being slid horizontally together with the first door; imaging means that is disposed beside a space between the first entrance and the second entrance, and that captures images across the space; and an image processing and determining portion that determines presence or absence of an obstruction inside the space based on image data from the imaging means. 
     According to another aspect of the present invention, there is provided an elevator including: a car that has a car entrance, and that is raised and lowered inside a hoistway; a car door that is disposed on the car, and that opens and closes the car entrance by being slid horizontally; a landing door that is disposed on a landing, and that opens and closes a landing entrance by being slid horizontally together with the car door; imaging means that is disposed on the car beside a space between the car entrance and the landing entrance, and that captures images across the space; and an image processing and determining portion that determines presence or absence of an obstruction inside the space based on image data from the imaging means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural diagram that shows an elevator according to Embodiment 1 of the present invention; 
         FIG. 2  is a horizontal cross section of a sliding door apparatus from  FIG. 1 ; 
         FIG. 3  is a front elevation of a car door apparatus from  FIG. 2  viewed from a side near a landing; 
         FIG. 4  is a cross section of a light emitter from  FIGS. 2 and 3 ; 
         FIG. 5  is an outline block diagram that shows a control circuit of the sliding door apparatus from  FIG. 1 ; 
         FIG. 6  is an explanatory diagram that shows a differential image that is obtained by an image processing and determining portion from  FIG. 5  when an obstruction is not present in a monitored region; 
         FIG. 7  is an explanatory diagram that shows a first example of a differential image that is obtained by the image processing and determining portion from  FIG. 5  when an obstruction is present in a monitored region; 
         FIG. 8  is an explanatory diagram that shows a second example of a differential image that is obtained by the image processing and determining portion from  FIG. 5  when an obstruction is present in a monitored region; 
         FIG. 9  is a flowchart that shows action of a master control portion from  FIG. 5  during door closing; 
         FIG. 10  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 2 of the present invention; 
         FIG. 11  is a front elevation of a car door apparatus from  FIG. 10  viewed from a side near a landing; 
         FIG. 12  is an explanatory diagram that shows a differential image that is obtained by an image processing and determining portion in the sliding door apparatus from  FIG. 10  when doors are fully open; 
         FIG. 13  is an explanatory diagram that shows a differential image that is obtained by the image processing and determining portion in the sliding door apparatus from  FIG. 10  during a door-closing action; 
         FIG. 14  is an outline block diagram that shows a control circuit of the sliding door apparatus from  FIG. 10 ; 
         FIG. 15  is an outline block diagram that shows a control circuit of an elevator sliding door apparatus according to Embodiment 3 of the present invention; 
         FIG. 16  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 4 of the present invention; 
         FIG. 17  is a front elevation of a car door apparatus from  FIG. 16  viewed from a side near a landing; 
         FIG. 18  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 5 of the present invention; 
         FIG. 19  is a front elevation of a car door apparatus from  FIG. 18  viewed from a side near a landing; 
         FIG. 20  is a cross section of a light emitter of a sliding door apparatus according to Embodiment 6 of the present invention; 
         FIG. 21  is a front elevation that shows a light emitter of a sliding door apparatus according to Embodiment 7 of the present invention; 
         FIG. 22  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 8 of the present invention; 
         FIG. 23  is a front elevation of a car door apparatus from  FIG. 22  viewed from a side near a landing; 
         FIG. 24  is an outline block diagram that shows a control circuit of an elevator sliding door apparatus according to Embodiment 9 of the present invention; 
         FIG. 25  is a flowchart that shows action of a master control portion from  FIG. 24  during door closing; 
         FIG. 26  is a flowchart that shows action of a master control portion according to Embodiment 11 of the present invention during door closing; 
         FIG. 27  is a front elevation that shows a light emitter of a sliding door apparatus according to Embodiment 12 of the present invention; 
         FIG. 28  is an explanatory graph that shows a relationship between a camera captured image and luminance distribution according to Embodiment 13 of the present invention; 
         FIG. 29  is a graph that shows an example of luminance distribution when an obstruction is present; 
         FIG. 30  is a cross section of a light emitter of a sliding door apparatus according to Embodiment 14 of the present invention; 
         FIG. 31  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 15 of the present invention; and 
         FIG. 32  is a front elevation of a car door apparatus from  FIG. 31  viewed from a side near a landing. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will now be explained with reference to the drawings. 
     Embodiment 1 
       FIG. 1  is a structural diagram that shows an elevator according to Embodiment 1 of the present invention. In the figure, a winding apparatus  2  is installed in an upper portion of a hoistway  1 . The winding apparatus  2  has: a drum  3 ; and a winding motor  4  that rotates the drum  3 . A wire  5  that constitutes a suspending means is wound onto the drum  3 . 
     A car  6  that constitutes a hoisted body is connected to an end portion of the wire  5 . The car  6  is suspended inside the hoistway  1  by the wire  5  and is raised and lowered inside the hoistway  1  by the winding apparatus  2 . A plurality of car guide rails  7  that guide raising and lowering of the car  5  are installed inside the hoistway  1 . 
     The car  6  has: a car frame  8  to which the wire  5  is connected; and a cage  9  that is supported by the car frame  8 . A car entrance  10  that constitutes a first entrance is disposed on a front surface of the cage  9 . Landing entrances  12  that constitute a second entrance are disposed on landings  11 . The car entrance  10  and the landing entrances  12  are opened and closed by a sliding door apparatus  13 . 
     The sliding door apparatus  13  has: a car door apparatus  14  that opens and closes the car entrance  10 ; a door driving apparatus  15  that drives the car door apparatus  14 ; a plurality of landing door apparatuses  16  that are disposed on all of the landings  11 , and that open and close the landing entrances  12 . The door driving apparatus  15  is mounted onto an upper portion of the car  6 . The landing door apparatuses  16  are opened and closed together with the car door apparatus  14  by engaging with the car door apparatus  14  when the car  6  arrives at the landing  11 . 
       FIG. 2  is a horizontal cross section of the sliding door apparatus  13  from  FIG. 1 , and  FIG. 3  is a front elevation of the car door apparatus  13  from  FIG. 2  viewed from a side near a landing, each showing doors in a fully open state. A pair of vertical frames  17  and  18  are disposed on two sides of the car entrance  10 . Lower ends of the vertical frames  17  and  18  are linked to each other by a lower portion horizontal frame  19 . Upper ends of the vertical frames  17  and  18  are linked to each other by an upper portion horizontal frame  20 . The car entrance  10  is formed inside these frames  17  through  20 . 
     The car door apparatus  14  has car doors  21  and  22  that function as a first door that opens and closes the car entrance  10 . The car doors  21  and  22  act in a reverse direction to each other during opening and closing actions. The car doors  21  and  22  are housed in car door housing portions (door pocket portions)  23  and  24  when fully open. 
     Pairs of vertical frames  25  and  26  are disposed on two sides of the landing entrances  12 . Lower ends of the vertical frames  25  and  26  are linked to each other by lower portion horizontal frames  27 . Upper ends of the vertical frames  25  and  26  are linked to each other by upper portion horizontal frames (not shown). The landing entrances  12  are formed inside these frames  25  through  27 . 
     The landing door apparatuses  16  have landing doors  28  and  29  that function as a second door that opens and closes the landing entrances  12 . The landing doors  28  and  29  act in a reverse direction to each other during opening and closing actions. The landing doors  28  and  29  are housed in landing door housing portions (door pocket portions)  30  and  31  when fully open. 
     A light emitter  32  is disposed on the car  6  in a vicinity of the car door housing portions  24  (closer to the landings than the car door  22 ). The light emitter  32  aims a detecting beam  33  parallel to a closing and opening direction of the car doors  21  and  22  in a space between the car doors  21  and  22  and the landing doors  28  and  29 . The light emitter  32  has a vertically long and continuous light-emitting surface  32   a.    
     Imaging means that captures images of the light-emitting surface  32   a  is disposed beside a space between the car entrance  10  and the landing entrances  12 . 
     Specifically, the imaging means has first through third cameras  34  through  36  that are disposed on the car  6  in a vicinity of the car door housing portions  23  (closer to the landings than the car door  21 ) so as to face the light emitter  32 . The first camera  34  is disposed at a height that is approximately equal to that of an upper end portion of the car entrance  10 . The second camera  35  is disposed at a height that is approximately equal to that of a vertically intermediate portion of the car entrance  10 . The third camera  36  is disposed at a height that is approximately equal to that of a lower end portion of the car entrance  10 . The cameras  34  through  36  are each installed so as to capture an image of the entire light-emitting surface  32   a.    
       FIG. 4  is a cross section of the light emitter  32  from  FIGS. 2 and 3 . The light emitter  32  has: a circuit board  37 ; a plurality of light sources  38  that are disposed on the circuit board  37  so as to be spaced apart from each other vertically; and a translucent diffusing plate  39  that is disposed in front of the circuit board  37  so as to be opposite the light sources  38 . Light-emitting diodes or semiconductor lasers, for example, can be used for the light sources  38 . The light sources  38  are disposed so as to direct light over an entire region of the translucent diffusing plate  39 . The translucent diffusing plate  39  scatters and emits the light from the light sources  38 . The light-emitting surface  32   a  is formed by the translucent diffusing plate  39 . 
       FIG. 5  is an outline block diagram that shows a control circuit of the sliding door apparatus  13  from  FIG. 1 . In the figure, the door driving apparatus  15  is controlled by an opening and closing control portion  41 . Specifically, opening and closing actions of the car doors  21  and  22  and the landing doors  28  and  29  are controlled by the opening and closing control portion  41 . The opening and closing control portion  41  is mounted to the car  6 . 
     Signals from the first through third cameras  34  through  36  are sent to the image processing and determining portion  42 . The image processing and determining portion  42  determines whether the detecting beam  33  from the light emitter  32  has been interrupted by an obstruction during door closing based on the signals from the cameras  34  through  36 . 
     The light emitter  32 , the opening and closing control portion  41 , and the image processing and determining portion  42  are controlled by a master control portion  43 . The master control portion  43  shines the detecting beam  33  from the light emitter  32  at least during a door closing action. The master control portion  43  also reverses and opens the car doors  21  and  22  and the landing doors  28  and  29  if an obstruction is detected by the image processing and determining portion  42  during the door closing action. 
     The opening and closing control portion  41 , the image processing and determining portion  42 , and the master control portion  43  are each constituted by a microcomputer. It is also possible to constitute any two of the opening and closing control portion  41 , the image processing and determining portion  42 , and the master control portion  43  using a shared computer. A control apparatus includes the opening and closing control portion  41 , the image processing and determining portion  42 , and the master control portion  43 . 
     Next, a method for detecting obstructions using the image processing and determining portion  42  will be explained. First, image data α from the cameras  34  through  36  when the light emitter  32  is not switched on, and image data β when the light emitter  32  is switched on and there is no obstruction are imported into the image processing and determining portion  42 . Then, a differential image γ is calculated by subtracting the image data α from the image data β. An action of this kind is repeated while executing obstruction monitoring. 
     When a differential process of this kind is performed, only an image of the light-emitting surface  32   a  remains in the differential image γ. Consequently, if no obstruction is present inside three triangular monitored regions that have the cameras  34  through  36  as apexes and the light-emitting surface  32   a  as base sides, a single continuous rectilinear light-emitting surface image such as that shown in  FIG. 6  will remain in the differential image γ. 
     In contrast to that, if an obstruction is present inside the monitored regions, light-emitting surface images such as those shown in  FIG. 7  or  FIG. 8  will remain in the differential image γ since a portion of the detecting beam  33  will be interrupted. Specifically, in the differential image γ in  FIG. 7 , the light-emitting surface image has been divided plurally and is discontinuous. The length of the light-emitting surface image in the differential image γ in  FIG. 8  is shorter than normal. If the image processing and determining portion  42  detects that the light-emitting surface image has become discontinuous or has become shorter or that the light-emitting surface image has disappeared, then it determines that an obstruction is present and sends a signal to that effect to the master control portion  43 . 
       FIG. 9  is a flowchart that shows action of the master control portion  43  from  FIG. 5  during door closing. When a predetermined time interval has elapsed after door opening, the master control portion  43  checks whether an obstruction is present in the monitored regions (Step S 1 ). If no obstruction is present, start the door closing action (Step S 2 ). If an obstruction is present, hold until the obstruction is removed, and start the door closing action after the obstruction has been removed. 
     After starting the door closing action, check whether an obstruction is present in the monitored regions (Step S 3 ), continue the door closing action if no obstruction is present (Step S 4 ), and check whether the car doors  21  and  22  and the landing doors  28  and  29  have reached fully closed positions (Step S 5 ). In other words, during the door closing action, the presence or absence of an obstruction is repeatedly checked for until the doors reach a fully closed state. 
     If an obstruction is detected during the door closing action, reverse and open the car doors  21  and  22  and the landing doors  28  and  29  (Step S 6 ), and return to the first action. The action in  FIG. 9  terminates when the doors reach a fully closed state without an obstruction being detected. 
     In a sliding door apparatus  13  of this kind, because the first through third cameras  34  through  36  are disposed beside the space between the car entrance  10  and the landing entrances  12  obstructions that would actually be caught in the doors  21 ,  22 ,  28 , and  29  can be detected more reliably. 
     Because frequent occurrences of reversing action due to false detection can be prevented, operating efficiency can be improved when applied to elevators. 
     In addition, if applied to elevators, because the cameras  34  through  36  need only be mounted to the car  6 , costs can be reduced compared to when cameras are disposed on all of the landings. 
     Because the light emitter  32  is disposed at a position that faces the cameras  34  through  36  across the space between the car entrance  10  and the landing entrances  12  and images of the light-emitting surface  32   a  are captured by the cameras  34  through  36 , obstructions can be detected more reliably. 
     Because the image processing and determining portion  42  determines presence or absence of an obstruction based on a differential image between image data when the light emitter  32  is switched off and image data when the light emitter  32  is switched on, obstructions can be detected more reliably. 
     In addition, because the image processing and determining portion  42  determines that an obstruction is present if the image of the light-emitting surface  32   a  is discontinuous, if the length of the image of the light-emitting surface  32   a  is shortened, or if the image of the light-emitting surface  32   a  disappears, obstructions can be detected more reliably. 
     Because the imaging means includes three cameras  34  through  36  that are disposed at different heights, obstructions can be detected more reliably. 
     Embodiment 2 
     Next,  FIG. 10  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 2 of the present invention, and  FIG. 11  is a front elevation of a car door apparatus from  FIG. 10  viewed from a side near a landing. In the figures, a light emitter  32  is mounted to a door closing end portion of a front surface of a car door  22  (a surface that faces a landing door  29 ). In other words, the light emitter  32  moves together with the car door  22 . 
     A first camera  34  is disposed at a height that is different from that of an upper end portion of a light-emitting surface  32   a . In this case, the first camera  34  is disposed at a position that is lower than the upper end portion of the light-emitting surface  32   a . In addition, the first camera  34  is disposed such that a straight line B that joins the upper end portion of the light-emitting surface  32   a  and the first camera  34  and an optical axis A of a lens system of the first camera  34  never become parallel. 
     In Embodiment 2, distances between the light emitter  32  and the cameras  34  through  36  change together with movement of the car doors  22 , and perspective angles φa, φb, and φc of the light-emitting surface  32   a  from the cameras  34  through  36  also change. Because of this, lengths of images of the light-emitting surface  32   a  that are captured by the cameras  34  through  36  change together with the movement of the car doors  22 . That is, whereas a differential image γ such as that shown in  FIG. 12 , for example, is obtained when the doors are fully open, a differential image γ such as that shown in  FIG. 13 , for example, is obtained as the door closing action progresses, since the light-emitting surface  32   a  approaches the cameras  34  through  36 . 
     Thus, when the light emitter  32  is mounted to the car doors  22 , it is necessary to find lengths of the light-emitting surface image that constitute comparative references that correspond to the position of the car doors  22  because the length of the light-emitting surface image will change due to the door closing action of the car doors  22  even if an obstruction is not present. 
       FIG. 14  is an outline block diagram that shows a control circuit of the sliding door apparatus from  FIG. 10 . A door position and image length determining portion  44  determines the position of the car doors  22  based on the data of the differential image γ that has been obtained from an image processing and determining portion  42  and also finds a reference length for the light-emitting surface image that corresponds to the position of the car doors  22 . A control apparatus includes an opening and closing control portion  41 , the image processing and determining portion  42 , a master control portion  43 , and the door position and image length determining portion  44 . 
     Now, in  FIG. 11 , an angle θ that is formed by the straight line B with respect to the optical axis A changes together with the movement of the car doors  22 . Because of this, the position of the upper end portion of the image of the light-emitting surface  32   a  captured by the cameras  34  changes together with the movement of the car doors  22 . Consequently, the position of the upper end portion of the light-emitting surface image of the differential image γ that is obtained from the image data from the cameras  34  is uniquely dependent upon the position of the car doors  22 . 
     The door position and image length determining portion  44  determines the position of the car doors  22  making use of this principle, and sends information concerning the reference length of the light-emitting surface image that corresponds to the position of the car doors  22  to the image processing and determining portion  42 . Based on the reference length of the light-emitting surface image, the image processing and determining portion  42  determines the presence or absence of an obstruction in a similar manner to that of Embodiment 1. The door position and image length determining portion  44  can be constituted by a microcomputer that is shared with or independent from the image processing and determining portion  42 . The rest of the configuration is similar to that of Embodiment 1. 
     According to a sliding door apparatus  13  of this kind, because the light emitter  32  is mounted to the car doors  22 , installation space for the light emitter  32  can be reduced. 
     Because distances between the light emitter  32  and the cameras  34  through  36  can be shortened, detecting precision can be improved. 
     In addition, because the light emitter  32  and a camera  34  are disposed in such a way that the position of images of the upper end portion of the light-emitting surface  32   a  captured by the camera  34  changes together with the movement of the car doors  22 , and the position of the car doors  22  and a reference length for the light-emitting surface image that corresponds to that position are found based on image data of the light-emitting surface  32   a  obtained from the camera  34 , changes in the distances between the light emitter  32  and the cameras  34  through  36  due to the movement of the car doors  22  can be compensated for without having to add a door position measuring apparatus. 
     Moreover, visible light may also be used for the detecting beam  33  that is emitted from the light emitter  32 . In that case, passengers can visually recognize the light-emitting surface  32   a , and action of the doors  21 ,  22 ,  28 , and  29  can be visually indicated to the passengers by linking timing of light emission to the action of the doors  21 ,  22 ,  28 , and  29 . For example, the passengers can be informed more intelligibly of the door closing action if light is not emitted while the doors are opening or while the doors are being held open, and light is emitted as the doors start to close and during the door closing action. 
     Embodiment 3 
     Next,  FIG. 15  is an outline block diagram that shows a control circuit of an elevator sliding door apparatus according to Embodiment 3 of the present invention. In the figure, a door position measuring apparatus  45  is disposed on a drive portion of car doors  21  and  22 , and outputs a signal that corresponds to the position of the car doors  21  and  22 . An encoder that is mounted to a motor of a door driving apparatus  15  can be used for the door position measuring apparatus  45 , for example. An image length determining portion  40  sends information concerning a reference length of the light-emitting surface image that corresponds to the position of the car doors  21  and  22  to an image processing and determining portion  42  based on information from the door position measuring apparatus  45 . A control apparatus includes an opening and closing control portion  41 , the image processing and determining portion  42 , a master control portion  43 , and the image length determining portion  40 . The rest of the configuration is similar to that of Embodiment 2. 
     By using a door position measuring apparatus  45  in this manner, the control circuit can be simplified, and adjustment of the mounted positions of the cameras  34  through  36  and the light emitter  32  can also be facilitated. 
     Embodiment 4 
     Next,  FIG. 16  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 4 of the present invention, and  FIG. 17  is a front elevation of a car door apparatus from  FIG. 16  viewed from a side near a landing. In this example, cameras  34  through  36  are mounted to a car door  21  instead of a light emitter  32 . 
     Similar effects to those in Embodiment 3 above can also be achieved if the cameras  34  through  36  are mounted to the car door  21  in this manner. 
     Embodiment 5 
     Next,  FIG. 18  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 5 of the present invention, and  FIG. 19  is a front elevation of a car door apparatus from  FIG. 18  viewed from a side near a landing. In this example, a light emitter  32  is mounted to a car door  22 , and cameras  34  through  36  are mounted to a car door  21 . 
     It is also possible to mount the light emitter  32  and the cameras  34  through  36  to the car doors  21  and  22  in this manner, and using this kind of configuration, obstructions that would actually be caught in the doors  21 ,  22 ,  28 , and  29  can also be detected more reliably. 
     Embodiment 6 
     Next,  FIG. 20  is a cross section of a light emitter of a sliding door apparatus according to Embodiment 6 of the present invention. An upper portion light source  46   a  that shines light downward is fixed to an upper end portion of a light emitter  32 . A lower portion light source  46   b  that shines light upward is also fixed to a lower end portion of the light emitter  32 . A transparent light-conducting body  47  that conducts light longitudinally (vertically) is disposed between the upper portion light source  46   a  and the lower portion light source  46   b . A light-emitting surface  32   a  is formed on a front surface of the transparent light-conducting body  47 . A diffusing surface  48  that diffuses light is joined together with a surface of the transparent light-conducting body  47  that faces the light-emitting surface  32   a  (a back surface). 
     Light that has entered the transparent light-conducting body  47  from the light sources  46   a  and  46   b  is propagated through the transparent light-conducting body  47  while being diffused by the diffusing surface  48 . Then, the light that has been scattered by the diffusing surface  48  is emitted from the light-emitting surface  32   a  as a detecting beam  33 . The rest of the configuration is similar to that of Embodiment 1. 
     By using a light emitter  32  of this kind, the number of light sources  46   a  and  46   b  can be reduced, enabling power to be saved and cost reductions to be achieved. 
     Moreover, the diffusing surface  48  may also be formed integrally on the transparent light-conducting body  47  by machining the surface of the transparent light-conducting body  47  that faces the light-emitting surface  32   a.    
     Embodiment 7 
     Next,  FIG. 21  is a front elevation that shows a light emitter of a sliding door apparatus according to Embodiment 7 of the present invention. First through fourth transparent light-conducting bodies  49  through  52  are disposed side by side sequentially from an upper portion of a light emitter  32 . The light-emitting surfaces  32   a  is thereby divided into a plurality of (four) light-emitting surfaces  49   a ,  50   a ,  51   a , and  52   a . The first through fourth transparent light-conducting bodies  49  through  52  are also disposed so as to be offset alternately in a width direction of the light emitter  32 . In addition, vertically adjacent transparent light-conducting bodies  49  through  52  are disposed to overlap partially in a vertical direction. 
     A first upper portion light source  53  is disposed at an upper end portion of the first transparent light-conducting body  49 . A first lower portion light source  54  is disposed at a lower end portion of the first transparent light-conducting body  49 . A second upper portion light source  55  is disposed at an upper end portion of the second transparent light-conducting body  50 . A second lower portion light source  56  is disposed at a lower end portion of the second transparent light-conducting body  50 . A third upper portion light source  57  is disposed at an upper end portion of the third transparent light-conducting body  51 . A third lower portion light source  58  is disposed at a lower end portion of the third transparent light-conducting body  51 . A fourth upper portion light source  59  is disposed at an upper end portion of the fourth transparent light-conducting body  52 . A fourth lower portion light source  60  is disposed at a lower end portion of the fourth transparent light-conducting body  52 . Diffusing surfaces  48  (see  FIG. 20 ) are joined with surfaces that face front surfaces (the light-emitting surfaces  49   a ,  50   a ,  51   a , and  52   a ) of the respective transparent light-conducting body  49  through  52 . The rest of the configuration is similar to that of Embodiment 1. 
     By using a plurality of transparent light-conducting body  49  through  52 , and disposing light sources  53  through  60  at two end portions of the respective transparent light-conducting bodies  49  through  52  in this manner, intensity of the detecting beams  33  that are emitted from the respective transparent light-conducting bodies  49  through  52  can be maintained sufficiently. Light emitters  32  that have different lengths can also be prepared easily, simply by modifying the amount of vertical overlap between the transparent light-conducting bodies  49  through  52 . 
     Moreover, the light emitter  32  is not limited to the above examples, and may also be a linear light source that uses a fluorescent lamp or an electroluminescent light source, for example. 
     Embodiment 8 
     Next,  FIG. 22  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 8 of the present invention, and  FIG. 23  is a front elevation of a car door apparatus from  FIG. 22  viewed from a side near a landing. Embodiment 8 is an example in which the light emitter  32  from Embodiment 1 has been omitted. Cameras  34  through  36  capture images through a space between a car entrance  10  and landing entrances  12  of structures that are present at a far end of that space. Examples of structures of which images are captured include hoistway walls, hoisting machinery, etc. Images of structures of this kind can be captured by the cameras  34  through  36  by illuminating them with lighting apparatuses inside the hoistway  1 , or by light from outside the hoistway  1 . 
     Even if the light emitter  32  is omitted in this manner, obstructions that would actually be caught in the doors  21 ,  22 ,  28 , and  29  can still be detected more reliably because the first through third cameras  34  through  36  are disposed beside the space between the car entrance  10  and the landing entrances  12 . 
     Embodiment 9 
     Next,  FIG. 24  is an outline block diagram that shows a control circuit of an elevator sliding door apparatus according to Embodiment 9 of the present invention. In the figure, a warning sound generating portion  61  that generates a warning sound in a vicinity of a car entrance  10  and landing entrances  12  is connected to a master control portion  43 . The warning sound may be a noise such as a buzzer or a chime, etc., or it may also be a voice such as an announcement, etc. The master control portion  43  generates the warning sound using the warning sound generating portion  61  if an obstruction is detected by an image processing and determining portion  42  during door closing. The rest of the configuration is similar to that of Embodiment 1. 
       FIG. 25  is a flowchart that shows action of the master control portion  43  from  FIG. 24  during door closing. When a predetermined time interval has elapsed after door opening, the master control portion  43  checks whether an obstruction is present in the monitored regions (Step S 1 ). If no obstruction is present, start the door closing action (Step S 2 ). If an obstruction is present, generate the warning sound using the warning sound generating portion  61  (Step S 7 ), hold until the obstruction is removed, and start the door closing action after the obstruction has been removed. 
     After starting the door closing action, check whether an obstruction is present in the monitored regions (Step S 3 ), continue the door closing action if no obstruction is present (Step S 4 ), and check whether the car doors  21  and  22  and the landing doors  28  and  29  have reached fully closed positions (Step S 5 ). In other words, during the door closing action, the presence or absence of an obstruction is repeatedly checked for until the doors reach a fully closed state. 
     If an obstruction is detected during the door closing action, reverse and open the car doors  21  and  22  and the landing doors  28  and  29 , and generate the warning sound using the warning sound generating portion  61  (Step S 8 ), and return to the first action. The action in  FIG. 24  terminates when the doors reach the fully closed state without an obstruction being detected. 
     In a sliding door apparatus  13  of this kind, because a warning sound is generated if an obstruction is detected, passengers can be informed aurally that an obstruction that constitutes a hindrance to the door closing action has been detected. 
     Embodiment 10 
     Next, Embodiment 10 of the present invention will be explained. Configuration of a sliding door apparatus  13  according to Embodiment 10 is similar to that of Embodiment 1. In Embodiment 10, the master control portion  43  performs a running check (failure detection) on the light emitters  32  and the cameras  34  through  36  when the doors are in the fully closed state. 
     Specifically, the master control portion  43  performs an action that is similar to the obstruction detecting action during door closing when the doors are in the fully closed state. Here, if the light emitters  32  and the cameras  34  through  36  are functioning normally, a continuous light-emitting surface image such as that shown in  FIG. 6  is obtained. In contrast to that, if light-emitting surface images such as those shown in  FIG. 7  or  FIG. 8  are obtained, for example, it can be considered that a portion of the light emitter  32  has failed and can no longer emit light, or images can no longer be captured of a portion of the light-emitting surface image due to failure of the cameras  34  through  36 . If the whole of the light-emitting surface image disappears, it can also be considered that the light emitter  32  or the cameras  34  through  36  have failed. 
     Because of this, if a dark portion that is greater than or equal to a predetermined length is present on the light-emitting surface image or the whole of the light-emitting surface image has disappeared in the running check of the light emitter  32  and the cameras  34  through  36 , the master control portion  43  determines that a failure has occurred in at least one of the light emitter  32  or the cameras  34  through  36 . 
     If a failure such as that described above is detected, the opening and closing control portion  41  changes over to low energy operation in which the door closing action is performed at a lower speed than normal. Thus, even if false negative detection of an obstruction occurs due to the failure, mechanical shock from a collision between the doors  21 ,  22 ,  28 , and  29  and the obstruction can be reduced. 
     Embodiment 11 
     Next, Embodiment 11 of the present invention will be explained. Configuration of a sliding door apparatus  13  according to Embodiment 11 is similar to that of Embodiment 1. In Embodiment 11, visible light is used for the detecting beam  33  that is emitted from the light emitter  32 . The master control portion  43  changes an emission pattern from the light emitter  32  if an obstruction is detected by an image processing and determining portion  42  during door closing. 
     For example, when no obstruction has been detected, the light emitter  32  may flash the detecting beam  33  for a predetermined period T (0.1 sec, for example). In contrast to that, when an obstruction is detected, the light emitter  32  may flash the detecting beam  33  for a period that is longer than period T ( 3 T or  4 T, for example). The rest of the configuration is similar to that of Embodiment 1. 
       FIG. 26  is a flowchart that shows action of the master control portion  43  according to Embodiment 11 of the present invention during door closing. When a predetermined time interval has elapsed after door opening, the master control portion  43  checks whether an obstruction is present in the monitored regions (Step S 1 ). If no obstruction is present, start the door closing action (Step S 2 ). If an obstruction is present, change the emission pattern from the light emitter  32  until a predetermined amount of time elapses (Step S 9 ), and perform the obstruction detecting action again. 
     After starting the door closing action, check whether an obstruction is present in the monitored regions (Step S 3 ), continue the door closing action if no obstruction is present (Step S 4 ), and check whether the car doors  21  and  22  and the landing doors  28  and  29  have reached fully closed positions (Step S 5 ). In other words, during the door closing action, the presence or absence of an obstruction is repeatedly checked for until the doors reach a fully closed state. 
     If an obstruction is detected during the door closing action, reverse and open the car doors  21  and  22  and the landing doors  28  and  29 , and change the emission pattern from the light emitter  32  (Step S 10 ), and return to the first action. The changed emission pattern continues until the doors reach a fully open state. The action in  FIG. 26  terminates when the doors reach the fully closed state without an obstruction being detected. 
     In a sliding door apparatus  13  of this kind, because the emission pattern from the light emitter  32  is changed if an obstruction is detected, passengers can be informed visually that an obstruction that constitutes a hindrance to the door closing action has been detected. 
     Moreover, in the above example, the flashing period of the detecting beam  33  is made longer during detection of an obstruction, but the flashing period may also be shortened instead. However, it is preferable to make the flashing period longer because if the flashing period during non-detection of an obstruction is comparatively short, it will be difficult for the passengers to notice if the flashing period is then made even shorter. 
     In the above example, a change in the flashing period was given as an example of the change in the emission pattern, but the whole of the light-emitting surface  32   a  may also be made to emit light during non-detection of an obstruction, and a portion of the light-emitting surface  32   a  made to emit light during detection of an obstruction, for example. 
     In addition, emission intensity of the detecting beam  33  may also changed between non-detection and detection of an obstruction. For example, the emission intensity of the detecting beam  33  may also be increased if an obstruction is detected. 
     Color of the detecting beam  33  may also changed between non-detection and detection of an obstruction. 
     Embodiment 12 
     Next,  FIG. 27  is a front elevation that shows a light emitter of a sliding door apparatus according to Embodiment 12 of the present invention. In this example, a light-emitting surface of a light emitter  32  is divided into: a plurality of first light-emitting surfaces  50   a  and  52   a  that are driven to switch on by a first light source driving portion  62 ; and a plurality of second light-emitting surfaces  49   a  and  51   a  that are driven to switch on by a second light source driving portion  63 . 
     Specifically, the first light-emitting surfaces  50   a  and  52   a  are formed on second and fourth transparent light-conducting bodies  50  and  52 . The second light-emitting surfaces  49   a  and  51   a  are formed on first and third transparent light-conducting bodies  49  and  51 . In other words, the first and second light-emitting surfaces  50   a ,  52   a ,  49   a , and  51   a  are alternately disposed in a vertical direction of the light emitter  32 . 
     In order to arrange and configure first light-emitting surfaces  50   a  and  52   a  and second light-emitting surfaces  49   a  and  51   a  of this kind, a second upper portion light source  55 , a second lower portion light source  56 , a fourth upper portion light source  59 , and a fourth lower portion light source  60  are connected to the first light source driving portion  62 . A first upper portion light source  53 , a first lower portion light source  54 , a third upper portion light source  57 , and a third lower portion light source  58  are connected to the second light source driving portion  63 . 
     In other words, light sources  55 ,  56 ,  59 , and  60  that correspond to the transparent light-conducting bodies  50  and  52  that are odd numbered ordinal numbers from the bottom and light sources  53 ,  54 ,  57 , and  58  that correspond to the transparent light-conducting bodies  49  and  51  that are even numbered ordinal numbers from the bottom are wired independently from each other, and are driven to switch on independently from each other by the first and second light source driving portions  62  and  63 . The rest of the configuration is similar to that of Embodiment 7. 
     In a sliding door apparatus  13  such as that described above, even if a failure occurs in a portion of the light sources  53  through  60 , power supply cables, or power supply circuitry, the obstruction detecting action can continue to be executed because the light emitter will not cease to emit light completely. 
     Moreover, in the above example, the first light-emitting surfaces  50   a  and  52   a  and the second light-emitting surfaces  49   a  and  51   a  are disposed alternately in the vertical direction of the light emitter  32  but are not limited to that arrangement, and may also be disposed so as to be divided into an upper portion and a lower portion, for example. 
     In the above example, the light-emitting surface  49   a ,  50   a ,  51   a , and  52   a  were divided into two groups, but they may also be divide into three or more groups and be driven to switch on by respective independent light source driving portions. 
     Embodiment 13 
     Next,  FIG. 28  is an explanatory graph that shows a relationship between a camera captured image and luminance distribution according to Embodiment 13 of the present invention. In this example, a light emitter  32  such as that shown in Embodiment 7 or 12 is used. The size of two-dimensional image data that is obtained by the cameras  34  through  36  is Gx by Gy. Moreover, a longitudinal direction (a vertical direction) of the light emitter  32  is the x direction, and a direction that is perpendicular to the x direction is the y direction. 
     In the image processing and determining portion  42 , a differential image is found for image data in a region of a portion that includes the light-emitting surface image (Wx by Wy: Wx&lt;Gx, Wy&lt;Gy). Then, an x-axial distribution of luminance values b(x) is found from the differential image of Wx by Wy using a predetermined calculation. For example, a sum of luminance of all pixels that are lined up in the y direction is found for every position x. An average of luminance of all pixels that are lined up in the y direction may also be found for every position x. In addition, a maximum value of luminance of all pixels that are lined up in the y direction may also be found for every position x. Moving average values of N pixels (N&lt;Wy) in the y direction (average values of N consecutive pixels) for every position x may also be found, and a maximum value of these moving average values found. 
     The distribution of the luminance values b(x) that are found in this manner are continuous in the x direction if there is no obstruction, as shown in  FIG. 28 . In contrast to that, the distribution of the luminance values b(x) is discontinuous when an obstruction is present, as shown in  FIG. 29 , for example. Consequently, the image processing and determining portion  42  determines that an obstruction is present if at least a portion of the distribution of the luminance values b(x) is less than or equal to a predetermined value. 
     A luminance difference distribution may also be found by finding distributions of the luminance values b(x) for two sets of image data that are obtained at a predetermined time interval, and taking the difference between the two distributions of luminance values b(x). If there is no moving object, the absolute values of the luminance difference distribution will be small values overall because the distribution of the luminance values b(x) will not change. In contrast to that, if there is a moving object, the absolute values of the luminance difference distribution will be large values in at least a portion since the distribution of the luminance values b(x) will change. 
     Consequently, in that case, the image processing and determining portion  42  determines that an obstruction is present if the absolute values are greater than or equal to a predetermined value in at least a portion of the luminance difference distribution that is found from the two sets of image data that are obtained at the predetermined time interval. 
     By using cameras  34  through  36  that obtain two-dimensional image data as imaging means in this manner, precision in positioning the cameras  34  through  36  relative to the light emitter  32  can be lowered, enabling time spent on installation to be reduced. Costs can also be reduced by making use of commercially available imaging devices. 
     Because image data in a region of a portion that includes the light-emitting surface image are clipped and processed from the two-dimensional image data that the cameras  34  through  36  obtain, the size of the data that is processed is reduced, enabling processing speed to be increased. 
     In addition, because a vertical luminance distribution is found from the two-dimensional image data by a predetermined calculation, and the presence or absence of an obstruction is determined based on the luminance distribution, processing speed can be increased further, since two-dimensional image data are converted to one-dimensional luminance data. By converting to the one-dimensional luminance distribution, the presence or absence of an obstruction can be determined directly therefrom even if the light-emitting surface is divided plurally. 
     By determining the presence or absence of an obstruction from absolute values of a luminance difference distribution that is found from two sets of image data that are obtained at a predetermined time interval, litter that has adhered the light emitter  32  or the cameras  34  through  36  can be prevented from being mistakenly determined as an obstruction, enabling detecting precision to be improved. 
     Embodiment 14 
     Next,  FIG. 30  is a cross section of a light emitter of a sliding door apparatus according to Embodiment 14 of the present invention. In a light emitter  32  according to Embodiment 14, a diffusing plate  64  that diffuses light as it passes through is disposed in front of a transparent light-conducting body  47  according to Embodiment 6. That is, the diffusing plate  64  is disposed so as to face a front surface of the transparent light-conducting body  47 . Light emitted from the front surface of the transparent light-conducting body  47  is scattered by the diffusing plate  64 , and is emitted out from a light emitter  32  from a front surface of the diffusing plate  64 , that is, from a light-emitting surface  32   a . The rest of the configuration is similar to that of Embodiment 6. 
     By disposing a diffusing plate  64  in front of the transparent light-conducting body  47  in this manner, the captured light-emitting surface image has sufficient brightness irrespective of the height of the cameras  34  through  36 , since the light that is emitted from the transparent light-conducting body  47  is scattered uniformly in a vertical direction, enabling detecting precision to be improved. 
     Embodiment 15 
     Next,  FIG. 31  is a horizontal cross section of an elevator sliding door apparatus according to Embodiment 15 of the present invention, and  FIG. 32  is a front elevation of a car door apparatus from  FIG. 31  viewed from a side near a landing. In the figures, first and second light emitters  71  and  72  are disposed in a vicinity of car door housing portions  23  and  24  of a car  6  (closer to landings than car doors  22 ). Specifically, the first and second light emitters  71  and  72  are disposed so as to that face each other on opposite sides of a space between a car entrance  10  and landing entrances  12 . 
     The light emitters  71  and  72  aim detecting beams  33  parallel to a closing and opening direction of the car doors  21  and  22  in a space between the car doors  21  and  22  and the landing doors  28  and  29 . The light emitters  71  and  72  have vertically long and continuous light-emitting surfaces  71   a  and  72   a.    
     Imaging means includes: a first camera  73  that is disposed on an upper portion of the first light emitter  71 , and that captures images of the light-emitting surface  72   a  of the second light emitter  72 ; and a second camera  74  that is disposed on a lower portion of the second light emitter  72 , and that captures images of the light-emitting surface  71   a  of the first light emitter  71 . The rest of the configuration is similar to that of Embodiment 1. 
     In a sliding door apparatus  13  of this kind, a detection range that is formed by the light emitters  71  and  72  and the cameras  73  and  74  is an entire surface between the light emitters  71  and  72 . Consequently, regions in which detection is not possible are eliminated even when the car doors  21  and  22  and the landing doors  28  and  29  are fully open, enabling reliability to be improved. 
     Moreover, in the above examples, a sliding door apparatus that opens to two sides has been explained, but the present invention can also be applied to doors that open to one side, and the car doors and the landing doors are not limited to a particular number of leaves. 
     In the above examples, a drum-wound elevator apparatus has been shown, but the present invention can of course also be applied to traction elevator apparatuses that use a counterweight. 
     In addition, in the above examples, the present invention has been applied to an elevator, but the present invention can also be applied to sliding door apparatuses other than elevators such as double-door door apparatuses that are disposed in buildings, or door apparatuses that include train doors and platform doors, etc., for example.