Abstract:
A conveyance control device includes a drive mechanism to drive a reciprocating body, an origin sensor, a drive amount detection unit for detecting the drive amount of the drive mechanism, and a movement detection unit for optically detecting the reciprocating body&#39;s shifting from a resting state to a moving state. After the reciprocating body is moved in one direction until the origin sensor turns from a first output state to a second output state, the reciprocating body is moved in the opposite direction until the origin sensor turns back to the first output state. A first drive amount from when the origin sensor turns to the second output state to when the reciprocating body shifts from the resting state to the moving state, and a second drive amount from when the reciprocating body shifts to the moving state to when the origin sensor turns to the first output state are acquired.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. P2008-250192 filed on Sep. 29, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a conveyance device for holding and reciprocating a conveyance object on a predetermined conveyance path. The present invention also relates to a control method of the conveyance device and an observation device provided with the conveyance device. 
         [0004]    2. Description of Related Art 
         [0005]    Generally, a conveyance device for reciprocating a conveyance object along a predetermined conveyance path includes a reciprocating body for holding and reciprocating the conveyance object on the predetermined conveyance path and a drive mechanism for driving the reciprocating body along the conveyance path. In such a conveyance device, in order to return the reciprocating body to an origin position on the conveyance path, an origin sensor is provided which is switched from an OFF state to an ON state by the reciprocating body when the reciprocating body has reached the origin position. 
         [0006]    A gear mechanism and a pulley mechanism for example are adopted as the drive mechanism, which converts the rotation of a motor as a power source to reciprocating motion and transmits it to the reciprocating body. The amount of motor operation can be measured by counting the number of drive pulses using for example an internal counter of a motor controller. In addition, an inductive proximity sensor can be used as the origin sensor, wherein a detection coil generating a magnetic field detects changes in impedance caused by an object moving in the magnetic field object. 
         [0007]    In a drive mechanism in which a gear mechanism is used, a backlash can exist between gears, and therefore, when a conveyance object is moved in one direction along the conveyance path and thereafter moved backward in the opposite direction, a period occurs during which the motor runs idle due to the backlash and during which the conveyance object remains stopped even if the motor is rotating. 
         [0008]    Thus, Japanese Patent Laid-Open No. 2005-092152 describes technology wherein lost motion caused by the backlash is prevented by unifying the drive direction in one direction when the drive mechanism is stopped. 
         [0009]    Japanese Patent Laid-Open No. 2004-283977 describes technology wherein in a slitter device for slitting while conveying a sheet-like material printed in a number of colors, printing deviations of two reference marks printed on the sheet-like material are inspected by detecting a distance between the two reference marks. 
         [0010]    However, in the conventional technology that unifies the drive direction in one direction when the drive mechanism is stopped, while the lost motion caused by the backlash does not occur when the drive mechanism is driven in one direction, if the drive mechanism is driven in the opposite direction, lost motion caused by the backlash occurs and positioning control conducted by the drive mechanism contains error because a measurement of such backlashes cannot be detected quantitatively. 
         [0011]    On the other hand, in the conventional technology wherein two reference marks are printed on a sheet-like material, as a conveyance object is moved and the distance between the two reference marks is detected, and while it is possible to inspect the printing deviations of the reference marks and to correct the position of the sheet-like material according to the amount of deviations, the conventional technology cannot address, for example, a position detection error in a current usage environment wherein the origin sensor determines a reference position of the motor operation and change over time with an amount of the backlash contained in the drive mechanism. 
         [0012]    In operation of the origin sensor, a position detection error can exist due to a difference in responsiveness between switching from the ON state to the OFF state upon the approaching of a detection object and switching from the OFF state to the ON state with the leaving of the detection object. Therefore, a gap exists between a position at which switching from the ON state to the OFF state is detected and a position at which switching from the OFF state to the ON state is detected. 
         [0013]    While the backlash changes over time, the position detection error of the origin sensor changes with an influence by a current usage environment, e.g. the temperature. Therefore, a correction of the drive amount taking into consideration the feed amount error (backlash) specific to the drive mechanism and a correction of the drive amount taking into consideration the position detection error specific to the origin sensor need to be performed individually. However, in the conventional technology, the measurement of the feed amount error specific to the drive mechanism and the measurement of the position detection error specific to the origin sensor cannot be known individually. 
         [0014]    Therefore, an object of the invention is to provide a conveyance control device, a control method of the conveyance device, and an observation device, which can individually acquire the feed amount error of the drive mechanism and the position detection error of the origin sensor, and can perform a control operation by individually taking into consideration the feed amount error and the position detection error in a positioning control of the reciprocating body. 
       SUMMARY OF THE INVENTION 
       [0015]    One aspect of the present invention relates to a conveyance control device, which includes a reciprocating body that holds a conveyance object and reciprocates it on a predetermined conveyance path; a drive mechanism that drives the reciprocating body along the conveyance path; an origin sensor that is switched from a first output state to a second output state by the reciprocating body&#39;s reaching a predetermined position on the conveyance path; a control circuit for controlling an operation of the drive mechanism; a drive amount detection unit for detecting a drive amount of a power source of the drive mechanism; and a movement detection unit for optically detecting a point of time that the reciprocating body shifts from a resting state to a moving state. 
         [0016]    The control circuit includes a movement control unit that moves the reciprocating body in one direction until the origin sensor is switched from the first output state (e.g. the OFF state) to the second output state (e.g. the ON state) and then moves the reciprocating body in an opposite direction of the one direction until the origin sensor is switched from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state) in performing a positioning control of the reciprocating body; a drive amount acquisition unit that acquires, in the course of moving the reciprocating body by a control of the movement control unit, a first drive amount detected by the drive amount detection unit from a point of time that the origin sensor turns to the second output state (e.g. the ON state) and the reciprocating body starts moving in the opposite direction until a point of time that shifting of the reciprocating body from the resting state to the moving state is detected by the movement detection unit, and a second drive amount detected by the drive amount detection unit from the point of time that the shifting of the reciprocating body from the resting state to the moving state is detected by the movement detection unit until a point of time that the origin sensor turns to the first output state (e.g. the OFF state), in which a control operation is performed taking into consideration the acquired first and second drive amounts in the positioning control of the reciprocating body. 
         [0017]    Here, the first drive amount represents an amount of a feed amount error of the drive mechanism and the second drive amount represents an amount of a position detection error of the origin sensor. 
         [0018]    In some embodiments, the origin sensor is provided on the conveyance path, and it changes from the first output state (e.g. the OFF state) to the second output state (e.g. the ON state) with approaching of a shield plate placed on the reciprocating body, and changes from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state) with leaving of the shield plate. 
         [0019]    In further embodiments, the movement detection unit is composed of a test target provided on the reciprocating body and an image pickup device for capturing an image of the test target, in which in the course of moving the reciprocating body in the opposite direction from the second output state of the origin sensor to the first output state of the origin sensor, the image pickup device continuously captures images of the test pattern, and in which the movement detection unit determines that the reciprocating body has shifted from the resting state to the moving state when change occurs in the captured image. 
         [0020]    Another aspect of the present invention is a control method of a conveyance device, in which the conveyance device includes: a reciprocating body that holds a conveyance object and reciprocates it on a predetermined conveyance path; a drive mechanism that drives the reciprocating body along the conveyance path; an origin sensor that is switched from a first output state (e.g. the OFF state) to a second output state (e.g. the ON state) by the reciprocating body&#39;s reaching a predetermined position on the conveyance path; a drive amount detection unit for detecting a drive amount of a power source of the drive mechanism; and a movement detection unit for optically detecting a point of time that the reciprocating body shifts from a resting state to a moving state, in which the control method includes a first process of moving the reciprocating body in one direction until the origin sensor is switched from the first output state (e.g. the OFF state) to the second output state (e.g. the ON state) and resetting the drive amount detection unit at a point of time that the origin sensor becomes the second output state (e.g. the ON state); thereafter, in the course of moving the reciprocating body in an opposite direction of the one direction until the origin sensor is switched from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state), a second process of monitoring an output signal of the movement detection unit and acquiring a first detection amount (a first count value α) from the drive amount detection unit at a point of time that the reciprocating body shifts from the resting state to the moving state; thereafter, a third process of acquiring a second detection amount (a second count value γ) from the drive amount detection unit at a point of time that the origin sensor turns to the first output state (e.g. the OFF state); and a fourth process of deriving, from the first and second detection amounts (α and γ), a feed amount error of the drive mechanism due to change of the movement direction of the reciprocating body, and a position detection error due to a response difference of the origin sensor between switching from the first output state to the second output state and switching from the second output state to the first output state, and in which a positioning control of the reciprocating body is performed by taking into consideration the derived feed amount error and the derived position detection error. 
         [0021]    Still another aspect of the present invention is a control program of a conveyance device, in which the conveyance device includes: a reciprocating body that holds a conveyance object and reciprocates it on a predetermined conveyance path; a drive mechanism that drives the reciprocating body along the conveyance path; an origin sensor that is switched from a first output state (e.g. the OFF state) to a second output state (e.g. the ON state) by the reciprocating body&#39;s reaching a predetermined position on the conveyance path; a drive amount detection unit for detecting a drive amount of a power source of the drive mechanism; and a movement detection unit for optically detecting a point of time that the reciprocating body shifts from a resting state to a moving state, in which the control program causes a computer to execute a first process of moving the reciprocating body in one direction until the origin sensor is switched from the first output state (e.g. the OFF state) to the second output state (e.g. the ON state) and resetting the drive amount detection unit at a point of time that the origin sensor turns to the second output state (e.g. the ON state); thereafter in the course of moving the reciprocating body in an opposite direction of the one direction until the origin sensor is switched from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state), a second process of monitoring an output signal of the movement detection unit and acquiring a first detection amount (a first count value α) from the drive amount detection unit at a point of time that the reciprocating body shifts from the resting state to the moving state; thereafter, a third process of acquiring a second detection amount (a second count value γ) from the drive amount detection unit at a point of time that the origin sensor turns to the first output state (e.g. the OFF state); and a fourth process of deriving, from the first and second detection amounts (α and γ), a feed amount error of the drive mechanism due to change of the movement direction of the reciprocating body, and a position detection error due to a response difference of the origin sensor between switching from the first output state to the second output state and switching from the second output state to the first output state, and in which a positioning control of the reciprocating body is performed by taking into consideration the derived feed amount error and the derived position detection error. 
         [0022]    Still another aspect of the present invention is an observation device, which includes a reciprocating body that holds a conveyance object and reciprocates it on a predetermined conveyance path; a drive mechanism that drives the reciprocating body along the conveyance path; an image pickup device for capturing an image of an observation object held on the reciprocating body when the reciprocating body has reached a predetermined observation position on the conveyance path; an origin sensor that is switched from a first output state (e.g. the OFF state) to a second output state (e.g. the ON state) by the reciprocating body&#39;s reaching a predetermined position on the conveyance path; a drive amount detection unit for detecting a drive amount of a power source of the drive mechanism; a movement detection unit for optically detecting a point of time that the reciprocating body shifts from a resting state to a moving state; and a control circuit for controlling an operation of the drive mechanism, in which a test target whose image is captured by the observation device is provided on the reciprocating body, in which the movement detection unit determines that the reciprocating body has shifted from the resting state to the moving state at a point of time that change occurs in the image of the test target captured by the image pickup device, and in which the control circuit includes a movement control unit that moves the reciprocating body in one direction until the origin sensor is switched from the first output state (e.g. the OFF state) to the second output state (e.g. the ON state) and then moves the reciprocating body in an opposite direction of the one direction until the origin sensor is switched from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state) in performing a positioning control of the reciprocating body; and a drive amount acquisition unit that acquires a first drive amount detected by the drive amount detection unit from a point of time that the origin sensor turns to the second output state (e.g. the ON state) and the reciprocating body moves in the opposite direction until a point of time that the shifting of the reciprocating body from the resting state to the moving state is detected by the movement detection unit, and a second drive amount detected by the drive amount detection unit from the point of time that the shifting of the reciprocating body from the resting state to the moving state is detected by the movement detection unit until a point of time that the origin sensor turns to the first output state (e.g. the OFF state), in the course of moving the reciprocating body controlled by the movement control unit, and in which a control operation is performed taking into consideration the acquired first drive amount and the acquired second drive amount in the positioning control of the reciprocating body. 
         [0023]    In the conveyance control device, the control method of the conveyance device, and the observation device according to the invention, when performing a positioning control of the reciprocating body, in the course of moving the reciprocating body in one direction until the origin sensor is switched from the first output state (e.g. the OFF state) to the second output state (e.g. the ON state) and then resetting the drive amount detection unit (e.g. an internal counter) at a point of time that the origin sensor turns to the second output state (e.g. the ON state), and thereafter moving the reciprocating body in an opposite direction of the one direction until the origin sensor is switched from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state), a detection value (e.g. a count value α of the internal counter) is acquired by the drive amount detection unit at a point of time that the reciprocating body shifts from the resting state to the moving state. The acquired first detection value α represents a feed amount error of the drive mechanism caused by the change of the movement direction of the reciprocating body that is an amount of the backlash. 
         [0024]    Thereafter, in the course of moving the reciprocating body in the opposite direction, a detection value (e.g. a count value γ of the internal counter) is acquired by the drive amount detection unit at a point of time that the origin sensor is switched from the second output state (e.g. the ON state) to the first output state (e.g. the OFF state). The acquired second detection value γ represents the sum of the feed amount error of the drive mechanism and the position detection error of the origin sensor, and thus, the difference β obtained by subtraction of the first detection value α from the second detection value γ represents an amount of the position detection error of the origin sensor. 
         [0025]    After the feed amount error of the drive mechanism and the position detection error of the origin sensor are derived as such, a control operation is performed by taking into consideration the derived feed amount error and the derived position detection error in the positioning control of the reciprocating body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a perspective view showing external appearance of an observation device according to an embodiment of the present invention. 
           [0027]      FIG. 2  is a view showing an internal structure of the observation device. 
           [0028]      FIG. 3  is a plan view of an X-axis drive mechanism and a Y-axis drive mechanism according to an embodiment. 
           [0029]      FIG. 4  is a front view of the X-axis drive mechanism and the Y-axis drive mechanism. 
           [0030]      FIG. 5  is a side view of the X-axis drive mechanism and the Y-axis drive mechanism. 
           [0031]      FIG. 6  is a block diagram showing a structure of the observation device. 
           [0032]      FIG. 7  is a plan view showing a positional relationship of a holder, an X-axis sensor, and an X-axis shield plate at an origin position according to an embodiment. 
           [0033]      FIGS. 8A to 8C  are views for explaining switching between the ON/OFF state of the X-axis sensor. 
           [0034]      FIGS. 9A and 9B  are views showing a positional relationship between the X-axis sensor and the X-axis shield plate ( 9 A) and a captured image of a test target ( 9 B) at a first phase of an origin return operation. 
           [0035]      FIGS. 10A and 10B  are views showing a positional relationship between the X-axis sensor and the X-axis shield plate ( 10 A) and change with the captured image of the test target ( 10 B) at a second phase of the origin return operation. 
           [0036]      FIG. 11  is a view showing a positional relationship between the X-axis sensor and the X-axis shield plate at a third phase of the origin return operation. 
           [0037]      FIG. 12  is a view showing a positional relationship between the X-axis sensor and the X-axis shield plate at a fourth phase of the origin return operation. 
           [0038]      FIG. 13  is a flowchart showing a control process of the observation device according to the present invention. 
           [0039]      FIG. 14  is a flowchart showing a control process of the origin return operation. 
           [0040]      FIG. 15  is a flowchart showing a control process of feed amount error computation. 
           [0041]      FIG. 16  is a flowchart showing a control process of position detection error computation. 
           [0042]      FIG. 17  is a flowchart showing an alternative control process of the origin return operation. 
           [0043]      FIG. 18  is a flowchart showing a control process of an alternative control process of the observation device according to the present invention. 
           [0044]      FIG. 19  is a flowchart showing a control process of the origin return operation. 
           [0045]      FIGS. 20A to 20C  are a plan view ( 20 A), a front view ( 20 B), and a side view ( 20 C) showing a first phase of an origin return operation. 
           [0046]      FIGS. 21A to 21C  are a plan view ( 21 A), a front view ( 21 B), and a side view ( 21 C) showing a second phase of the origin return operation. 
           [0047]      FIGS. 22A to 22C  are a plan view ( 22 A), a front view ( 22 B), and a side view ( 22 C) showing a third phase of the origin return operation. 
           [0048]      FIGS. 23A to 23C  are a plan view ( 23 A), a front view ( 23 B), and a side view ( 23 C) showing a fourth phase of the origin return operation. 
           [0049]      FIGS. 24A to 24C  are a plan view ( 24 A), a front view ( 24 B), and a side view ( 24 C) showing a first phase of an operation to compute the feed amount error and the position detection error. 
           [0050]      FIGS. 25A to 25C  are a plan view ( 25 A), a front view ( 25 B), and a side view ( 25 C) showing a second phase of the operation to compute the feed amount error and the position detection error. 
           [0051]      FIGS. 26A to 26C  are a plan view ( 26 A), a front view ( 26 B), and a side view ( 26 C) showing a third phase of the operation to compute the feed amount error and the position detection error. 
           [0052]      FIGS. 27A to 27C  are a plan view ( 27 A), a front view ( 27 B), and a side view ( 27 C) showing a fourth phase of the operation to compute the feed amount error and the position detection error. 
           [0053]      FIGS. 28A to 28C  are a plan view ( 28 A), a front view ( 28 B), and a side view ( 28 C) showing a fifth phase of the operation to compute the feed amount error and the position detection error. 
           [0054]      FIG. 29  is a view showing an example of a positioning control taking into consideration the feed amount error. 
           [0055]      FIGS. 30A and 30B  are views showing an example of the positioning control taking into consideration the position detection error. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0056]    Specific embodiments in which the present invention is performed in an observation device will be described hereinafter by referring to the drawings. 
         [0057]    The observation device according to an embodiment of the invention is for observing an object such as a cell stained with fluorescent reagent. As shown in  FIGS. 1 and 2 , a stage  41  on which a flask  10  that holds an observation object is to be placed is provided within a housing  1 , and the stage  41  can be reciprocated in an X-axis direction and in a Y-axis direction on a horizontal plane by an X-axis drive mechanism  2  and a Y-axis drive mechanism  3 . 
         [0058]    Within the housing  1 , an illuminating device  13  having an LED  11  and a mirror  12  is provided for illuminating the flask  10 , and an image pickup device  16  having a CCD  15  and a mirror  14  also is provided for capturing an image of the flask  10 . 
         [0059]    As shown in  FIGS. 3 to 5 , the X-axis drive mechanism  2  includes an X-axis motor  21  as a power source. Rotation of the X-axis motor  21  is converted to reciprocating motion of an X-axis sliding body  25  connected to a timing belt  24  through a gear mechanism  26  and a pulley mechanism composed of pulleys  22 ,  23  and the timing belt  24 . The holder  4  is driven in the X-axis direction by the reciprocating motion of the X-axis sliding body  25 . 
         [0060]    Also, the Y-axis drive mechanism  3  has a Y-axis motor  31  as a power source. Rotation of the Y-axis motor  31  is converted to reciprocating motion of a Y-axis sliding body  35  connected to a timing belt  34  through a pulley mechanism composed of pulleys  32 ,  33  and the timing belt  34 . The holder  4  is driven in the Y-axis direction by the reciprocating motion of the Y-axis sliding body  35 . 
         [0061]    As shown in  FIG. 3 , the holder  4  holds the flask  10 , and the flask  10  held by the holder  4  moves in the Y-axis direction driven by the Y-axis drive mechanism  3  while moving in the X-axis direction driven by the X-axis drive mechanism  2 . 
         [0062]    As shown in  FIG. 5 , an X-axis sensor  5  is provided in the X-axis drive mechanism  2  for detecting an origin position of the X-axis sliding body  25  in the X-axis direction. The X-axis sensor  5  is switched between the ON/OFF state by approaching and leaving of an X-axis shield plate  51  connected to the X-axis sliding body  25 . 
         [0063]    As shown in  FIG. 4 , a Y-axis sensor  6  is provided in the Y-axis drive mechanism  3  for detecting an origin position of the Y-axis sliding body  35  in the Y-axis direction. The Y-axis sensor  6  is switched between the ON/OFF state by approaching and leaving of a Y-axis shield plate  61  connected to the Y-axis sliding body  35 . 
         [0064]    An inductive proximity sensor is used as the X-axis sensor  5  and the Y-axis sensor  6 , which causes a detection coil to generate a magnetic field and detects change in impedance by approaching of a detection object. 
         [0065]    As shown in  FIG. 6 , output signals of the X-axis sensor  5  and the Y-axis sensor  6  are supplied to a controller  7 , and the X-axis motor  21  and the Y-axis motor  31  are driven by drive control signals (drive pulses) generated at the controller  7 , which are supplied to drivers  74  and  75 . Electric power is supplied to the drivers  74  and  75  from a power circuit  73 . 
         [0066]    In addition, the X-axis motor  21  and the Y-axis motor  31  respectively are stepping motors, and a drive amount of each motor can be accurately measured by counting the number of drive pulses supplied from the controller  7  using an internal counter. 
         [0067]    Also, the illuminating device  13  is controlled at a lighting control circuit  72 , and necessary electric power is supplied to the lighting control circuit  72  from the power circuit  73 . 
         [0068]    Moreover, command signals sent by an operation of a user on a personal computer  71  are supplied to the image pickup device  16 , the lighting control circuit  72 , and the controller  7 , by which a control is performed on capturing an image of the observation object by the image pickup device  16 , illuminating the observation object by the illuminating device  13 , and driving the X-axis motor  21  and the Y-axis motor  31 . Power can be supplied to the image pickup device  16  from the personal computer  71  or from the power circuit  73 . 
         [0069]    As shown in  FIG. 7 , a test target  8  is provided on the holder  4 . The test target  8  is formed by providing a circular mark on a transparent glass part  81  e.g. by vapor deposition, and an image of the test target  8  can be captured by moving the holder  4  in the Y-axis direction and bringing the test target  8  so as to come within an image capturing range  17  of the image pickup device  16 . 
         [0070]      FIG. 7  shows a state in which the holder  4  is placed in an origin position. At the origin position, it is constructed such that the center of the flask held by the holder  4  comes within the image capturing range  17 . By moving the holder  4  from this state in the Y-axis direction (the CW direction), the test target  8  can be placed within the image capturing range  17 . 
         [0071]    As shown in  FIG. 7 , the X-axis sensor  5  is turned on when the X-axis shield plate  51  moves in the CCW direction and reaches the ON position, and thereafter, the X-axis sensor  5  is turned off when the X-axis shield plate  51  moves in the CW direction and reaches the off position. Thus, sensors have a gap between the range  5   a  at which the X-axis sensor  5  is turned ON from the OFF state and the range  5   b  at which the X-axis sensor is turned off from the ON state. 
         [0072]    When the holder  4  moves a predetermined distance in the CW direction from the origin position as shown in  FIG. 7 , a CW limit is placed by software on the movement of the holder  4 . Also, when the holder  4  moves a predetermined distance in the CCW direction from the origin position, a CCW limit is placed by software on the movement of the holder  4 . The Y-axis sensor  6  has a similar structure also. 
         [0073]    As shown in  FIGS. 8A to 8C , the X-axis shield plate  51  is formed such that it is elongated in the X-axis direction, and it is set up such that when it is on the CCW side from the origin position as shown in  FIG. 8B , the X-axis sensor  5  is always in the ON state, and when it is on the CW side from the origin position as shown in  FIG. 8C , the X-axis sensor  5  is always in the OFF state. The Y-axis shield plate  61  has a similar structure also. 
         [0074]    In the observation device according to the present invention, after the power is activated, as shown in  FIG. 9A , the X-axis motor  21  is rotated in the CCW direction until the X-axis sensor  5  is turned to the ON state from the OFF state thereby moving the X-axis shield plate  51 , and the X-axis shield plate  51  is stopped at a point that the X-axis sensor  5  is turned on. In this state, a backlash B is occurring in the X-axis drive mechanism  2 . 
         [0075]    At this point, the holder  4  is moved in the Y-axis direction and an image of the test target  8  is captured as shown in  FIG. 9B  in a state that the test target  8  comes within the image capturing range  17 . At the same time, the internal counter is reset. 
         [0076]    Next, as shown in  FIG. 10A , the X-axis motor  21  is reversed in the CW direction and an image of the test target  8  is captured continuously. At this time, the X-axis motor  21  runs idle and the X-axis shield plate  51  remains stopped until the backlash B of the X-axis drive mechanism  2  is cleared up, and at a point of time that the backlash B of the X-axis drive mechanism  2  is eliminated, the X-axis shield plate  51  starts moving. 
         [0077]    After the X-axis shield plate  51  starts moving, the captured image  8   b  of the test target  8  is shifted from the captured image  8   a  of the test target  8  before the X-axis shield plate  51  started moving, and thus, as shown in  FIG. 10B , if a difference is taken between the captured image  8   a  before the start of moving and the captured image  8   b  after the start of moving, a difference image  8   c  can be obtained, which has a dimension greater than or equal to a certain value. On the other hand, if a difference image  8   c  having such a dimension is not obtained, it can be determined that the test target  8  is in a resting state. 
         [0078]    Thus, the image of the test target  8  is captured continuously starting immediately after the X-axis motor  21  is reversed and the difference between the captured image  8   a  before the start of moving and the captured image  8   b  thereafter is computed. At a point that the difference image  8   c  having the dimension greater than or equal to a certain value is obtained, it is determined that the backlash has been eliminated and a count value α is taken in, which is obtained by subtracting 1 from the count value of the internal counter at that time. Therefore, the count value α represents the amount of the backlash of the X-axis drive mechanism  2 . 
         [0079]    Thereafter, as shown in  FIG. 11 , the X-axis shield plate  51  is moved further in the CW direction, and at a point that the X-axis sensor  5  is turned to the OFF state from the ON state, the X-axis shield plate  51  is stopped and at the same time a count value γ is taken in, which is obtained by subtracting 1 from the count value of the internal counter at that time. The count value γ represents the sum of the backlash of the X-axis drive mechanism  2  and the position detection error of the X-axis sensor  5 . 
         [0080]    Therefore, by subtracting the count value α from the count value γ, the difference β of the count values represents the amount of the position detection error of the X-axis sensor  5 . 
         [0081]    With respect to the Y-axis drive mechanism  3 , the count value α corresponding to the backlash of the Y-axis drive mechanism  3  and the count value difference β corresponding to the position detection error of the Y-axis sensor  6  also can be derived through a similar process. 
         [0082]      FIG. 13  shows a process for deriving the feed amount errors due to the backlashes with respect to the X-axis drive mechanism and the Y-axis drive mechanism and the position detection errors with respect to the X-axis sensor and the Y-axis sensor, and for returning the flask as the observation object to the observation starting position (origin position). 
         [0083]    After the system is activated, first, at step S 1 , a return to origin operation is performed with respect to the X-axis drive mechanism. At step S 2 , a return to origin operation is performed with respect to the Y-axis drive mechanism. 
         [0084]    At each of the return to origin operations, as shown in  FIG. 14 , at step S 21 , an output state of the sensor is checked and if the sensor is in the OFF state, at step S 25 , the drive mechanism is driven in the CCW direction. 
         [0085]    If the sensor is in the ON state, the process advances to step S 22 , and after the drive mechanism is driven in the CW direction, at step S 23 , the output state of the sensor is checked and driving in the CW direction is maintained until the sensor is turned off. 
         [0086]    When the sensor thus is turned off, at step S 24 , the drive mechanism is stopped, and then, at step S 25 , the drive mechanism is driven in the CCW direction. 
         [0087]    Thereafter, at step S 26 , the output state of the sensor is checked, and at a point that the sensor is turned on, the process advances to step S 27  and the drive mechanism is stopped. 
         [0088]    As a result, the X-axis drive mechanism and the Y-axis drive mechanism respectively return to the origin position (see  FIG. 7 ) and the rotation directions of the motors before stopping become the same. Also, the output states of the sensors both become in the ON state. 
         [0089]    After the return to origin operations of the X-axis drive mechanism and the Y-axis drive mechanism are completed, at step S 3  of  FIG. 13 , the Y-axis drive mechanism is operated and a target capturing operation is performed which places the test target  8  within the image capturing range  17 , as shown in  FIG. 7 . At this time, since the drive amount of the Y-axis motor generally is set according to the structure of the Y-axis drive mechanism, the Y-axis motor can be stopped after being rotated in the CW direction as much as a predetermined amount. 
         [0090]    Thereafter, at step S 4  of  FIG. 13 , with respect to the X-axis drive mechanism and the Y-axis drive mechanism, the rotation directions (CW, CCW) of the motors immediately before stopping are retained. The retention of the rotation directions of immediately before stopping may be implemented each time the driving is stopped with respect to each axis. 
         [0091]    Subsequently, at step S 5 , with respect to the X-axis drive mechanism and the Y-axis drive mechanism, the internal counters are reset to zero, which count the number of drive pulses of the respective motors. 
         [0092]    The process of steps S 1  to S 5  may be performed in succession with respect to the X-axis and the Y-axis or it maybe performed in parallel. Next, at step S 6 , an image of the test target is captured as a reference image and the result is stored in a memory at step S 7 . 
         [0093]    Thereafter, at step S 8 , the feed amount error caused by a backlash of the X-axis drive mechanism is computed. In computing the feed amount error, as shown in  FIG. 15 , at step S 31 , the rotation direction of immediately before is read out, determining its opposite direction as the motor drive direction, and at step S 32 , the motor is driven as much as 1 pulse. Then at step S 33 , the internal counter is incremented, and thereafter at step S 34 , an image of the test target is captured. 
         [0094]    At step S 35 , a differential processing is performed with respect to the reference image stored in the memory and the image captured at step S 34 , and it is determined whether or not change exists between the two images. If it is determined that no change exists, it is considered that the driving of the 1 pulse immediately before was lost motion (the backlash is occurring), and the process returns to step S 32  to repeat the process from S 32  to S 35 . 
         [0095]    On the other hand, if it is determined that change exists at step S 35 , it is considered that the backlash has been cleared up, and at step S 36 , the count value α is stored in the memory as the feed amount error, which is a value that 1 is subtracted from the count value at that time. 
         [0096]    Thereafter, at step S 9  of  FIG. 13 , the position detection error with respect to the X-axis is computed. In computing the position detection error, as shown in  FIG. 16 , at step S 41 , the motor is driven as much as 1 pulse in the same direction as the drive direction determined at the time of computing the feed amount error, and then at step S 42 , the internal counter is incremented. Then, at step S 43 , the output state of the sensor is checked and if it is in the ON state, the process returns to step S 41  and repeats the 1 pulse driving of the motor. 
         [0097]    If the sensor is turned off at step S 43 , it is considered that the position detection error of the sensor is resolved, and at step S 44 , feed amount error information (the count value α) is read out from the memory, and at step S 45 , the number of pulses representing the position detection error amount (position detection error information) β is computed by subtracting the count value α representing the feed amount error from the count value γ, which is a value that 1 is subtracted from the current count value of the internal counter, and at step S 46 , the result is stored in the memory. 
         [0098]    Thereafter, at step S 10  of  FIG. 13 , a return to origin operation is performed with respect to the X-axis, and then at step S 11 , an image of the test target is captured as a reference image, and its result is stored in the memory at step S 12 . 
         [0099]    Thereafter, at step S 13 , a feed amount error caused by a backlash of the Y-axis drive mechanism is computed (see  FIG. 15 ). Furthermore, at step S 14 , a return to origin operation is performed, and then at step S 15 , the position detection error with respect to the Y-axis is computed (see  FIG. 16 ). Lastly, at step S 16 , a return to origin operation is performed with respect to the Y-axis and the sequence of the process is completed. 
         [0100]    The return to origin operation also can be performed by the process as shown in  FIG. 17 . First, at step S 51 , the output state of the sensor is checked. If the sensor is in the OFF state, at step S 52 , the drive mechanism is driven at high speed in the CCW direction. 
         [0101]    Thereafter, at step S 53 , the output state of the sensor is checked and the driving at high speed in the CCW direction is maintained until the sensor is turned to the ON state. 
         [0102]    When the sensor thus is turned on, at step S 54 , the drive mechanism is stopped, and then at step S 55 , the drive mechanism is driven at low speed in the CW direction. 
         [0103]    Moreover, at step S 56 , the output state of the sensor is checked and the driving at low speed in the CW direction is maintained until the sensor is turned off. 
         [0104]    When the sensor thus is turned off, at step S 57 , the drive mechanism is stopped, and then at step S 58 , the drive mechanism is driven at low speed in the CCW direction. 
         [0105]    On the other hand, when the sensor is in the ON state at step S 51 , the process advances to step S 61  at which the drive mechanism is driven at high speed in the CW direction, and then at step S 62 , the output state of the sensor is checked and the driving at high speed in the CW direction is maintained until the sensor is turned off. 
         [0106]    When the sensor thus is turned off, at step S 63 , the drive mechanism is stopped, and then at step S 58 , the drive mechanism is driven at low speed in the CCW direction. 
         [0107]    Thereafter, at step S 59 , the output state of the sensor is checked, and at a point that it is turned to the ON state, the process advances to step S 60  and the drive mechanism is stopped. 
         [0108]    Thus, the X-axis drive mechanism and the Y-axis drive mechanism rapidly return to the origin position respectively. At this time, even if each shield plate overshoots the ON position because of increased inertia force due to the high-speed driving of the X-axis drive mechanism and the Y-axis drive mechanism, thereafter each shield plate returns to the ON position of the sensor by the low-speed driving. 
         [0109]      FIG. 18  shows an alternative example of the process as shown in  FIG. 13 . At step S 1 ′ and step S 2 ′, error detection preparation operations are performed with respect to the X-axis drive mechanism and the Y-axis drive mechanism. This error detection preparation operation is the same as the return to origin operation as shown in  FIG. 17 . On the other hand, at step S 10 ′ and step S 16 ′, a return to origin operation as shown in  FIG. 19  is performed. 
         [0110]    At the return to origin operation of  FIG. 19 , first, at step S 71 , the output state of the sensor is checked, and if the sensor is in the OFF state, at step S 72 , the drive mechanism is driven at high speed in the CCW direction. 
         [0111]    Thereafter, at step S 73 , the output state of the sensor is checked and the driving at high speed in the CCW direction is maintained until the sensor is turned to the ON state. When the sensor thus is turned on, at step S 74 , the drive mechanism is stopped, and then at step S 75 , the drive mechanism is driven at low speed in the CW direction. 
         [0112]    Moreover, at step S 76 , the output state of the sensor is checked, and the driving at low speed in the CW direction is maintained until the sensor is turned off. When the sensor thus is turned off, at step S 77 , the drive mechanism is stopped, and then at step S 78 , the drive mechanism is driven at low speed in the CCW direction. 
         [0113]    On the other hand, if the sensor is in the ON state at step S 71 , the process advances to step S 91 , and the drive mechanism is driven at high speed in the CW direction, and then at step S 92 , the output state of the sensor is checked and the driving at high speed in the CW direction is maintained until the sensor is turned off. 
         [0114]    When the sensor thus is turned off, at step S 93 , the drive mechanism is stopped, and then at step S 78 , the drive mechanism is driven at low speed in the CCW direction. Thereafter, at step S 79 , the output state of the sensor is checked, and when it is turned to the ON state, the process advances to step S 80  at which the drive mechanism is stopped. Thereafter, at step S 81 , the drive mechanism is driven at low speed in the CW direction, and then at step S 82 , the output state of the sensor is checked, and at a point when the sensor is turned off, the process advances to step S 83  and the drive mechanism is stopped. As such, with the position that the sensor is turned off being the origin, a return to origin operation for returning to that origin is achieved. 
         [0115]      FIGS. 20A-20C  to  FIGS. 23A-23C  show an example of the return to origin operations with a position that the sensor is turned on is set as the origin.  FIGS. 20A to 20C  show a state in which both the X-axis and the Y-axis are in the limit positions. For example, from this state the return to origin operation is started. At this time, since the X-axis sensor  5  is in the OFF state, and the Y-axis sensor  6  is in the ON state, the X-axis motor  21  of the X-axis drive mechanism  2  is driven in the CCW direction, and thereafter, at a point when the X-axis sensor  5  is turned to the ON state, the X-axis drive mechanism  2  is stopped as shown in  FIGS. 21A to 21C . 
         [0116]    Next, since the Y-axis sensor  6  is in the ON state as shown in  FIG. 21 , the Y-axis motor  31  of the Y-axis drive mechanism  3  is driven in the CW direction, and thereafter, the Y-axis drive mechanism  3  is stopped at a point when the Y-axis sensor  6  is turned off as shown in  FIGS. 22A to 22C . At this time, since the Y-axis sensor  6  is in the OFF state, the Y-axis motor  31  of the Y-axis drive mechanism  3  is driven in the CCW direction and at a point when the Y-axis sensor  6  is turned to the ON state, the Y-axis drive mechanism  3  is stopped as shown in  FIGS. 23A to 23C . As a result, the return to origin operations of the X-axis drive mechanism  2  and the Y-axis drive mechanism  3  are completed. 
         [0117]      FIGS. 24A-24C  to  FIGS. 28A-28C  show an example of the operations for computing the feed amount error and the position detection error with a position that the sensor is turned on is set as the origin.  FIGS. 23A to 23C  show a state in which the X-axis drive mechanism  2  and the Y-axis drive mechanism  3  are stopped with the X-axis sensor  5  and the Y-axis sensor  6  being in the ON state. From this state, the Y-axis drive mechanism  3  is operated in the CW direction as much as a certain amount so as to place the test target  8  within the image capturing range, and a reference image of the test target  8  is captured. 
         [0118]    At this time, since the last rotation direction of the X-axis motor  21  of the X-axis drive mechanism  2  is CCW, lost motion is generated by driving the X-axis motor  21  in the CW direction. And in the course of operating the X-axis drive mechanism  2  until the X-axis sensor  5  is turned off from the ON state, the difference between the reference image and the captured image is monitored, and when a difference image having a dimension greater than or equal to a certain value is obtained, the count value α of the internal counter is taken in. Thereafter, as shown in  FIGS. 25A to 25C , at a point when the X-axis sensor  5  is turned off, the count value γ of the internal counter is taken in, and the feed amount error with respect to the X-axis drive mechanism  2  and the position detection error with respect to the X-axis sensor  5  are computed from the two count values. 
         [0119]    Next, as shown in  FIGS. 26A to 26C , after the X-axis drive mechanism  2  is returned to the origin, computation of the feed amount error of the Y-axis drive mechanism  3  is started. At this time, since the last rotation direction of the Y-axis motor  31  is CW, lost motion is generated by driving the Y-axis motor  31  in the CCW direction. Then the difference between the reference image and the captured image is monitored, and when a difference image having a dimension greater than or equal to a certain value is obtained, the count value α of the internal counter is taken in, and the feed amount error with respect to the Y-axis drive mechanism  3  is computed. 
         [0120]    From the state that the feed amount error computation is completed with respect to the Y-axis as shown in  FIGS. 27A to 27C , the Y-axis drive mechanism  3  further is returned to the origin, and thereafter the position detection error with respect to the Y-axis sensor  6  is computed. At this time, since the last rotation direction of the Y-axis motor  31  is CCW, lost motion is generated by driving the Y-axis motor  31  in the CW direction. Since the drive amount of the Y-axis motor  31  necessary for eliminating the lost motion already is computed, if the Y-axis motor  31  is rotated until the Y-axis sensor  6  is turned off, the position detection error with respect to the Y-axis sensor  6  also can be computed. 
         [0121]    Lastly, as shown in  FIGS. 28A to 28C , by returning the Y-axis drive mechanism  3  to the origin, the computation operations of the feed amount errors and the position detection errors with respect to the X-axis and the Y-axis are completed. 
         [0122]    In addition, the X-axis drive mechanism  2  also may be returned to the origin at this time. 
         [0123]    As such, after computing the feed amount errors (the numbers of drive pulses α) with respect to the X-axis drive mechanism and the Y-axis drive mechanism, and the position detection errors (the numbers of drive pulses β) with respect to the X-axis sensor and the Y-axis sensor, a proper positioning control of the observation device is performed by utilizing the computation results. 
         [0124]    The feed amount errors with respect to the X-axis drive mechanism and the Y-axis drive mechanism are reflected in the positioning control as follows. 
         [0125]    For example, as shown in  FIG. 29 , in a case that an observation object (cell) within the flask is observed at points A, B, and C starting from the origin O, when moving the observation position from point A(ax, ay) to point B(bx, by), the drive amount (the number of drive pulses) of the Y-axis motor is (ay−by+α y ) by taking into consideration the feed amount error α y  of the Y-axis drive mechanism. 
         [0126]    Thereafter, when moving the observation position from point B(bx, by) to point C (cx, cy), the drive amount (the number of drive pulses) of the X-axis motor is (bx−cx+α x ) by taking into consideration the feed amount error α x  of the X-axis drive mechanism, and the drive amount (the number of drive pulses) of the Y-axis motor is (cy−by+α y ) by taking into consideration the feed amount error α y  of the Y-axis drive mechanism. 
         [0127]    In addition, the X-axis sensor and the Y-axis sensor are associated with a gap (response difference) in the order of 10% of the detected distance between a switching position from the OFF state to the ON state upon approaching of the shield plate (a detected distance at the time of turning to the ON state) and a switching position from the ON state to the OFF state (a detected distance at the time of turning to the OFF state). The size of such gap varies depending on the temperature and the distance between the sensors and the shield plate. Because of this response difference, the position detection error is created. 
         [0128]    In the observation device, when performing a cell observation with respect to a specific position of the cell cultured within an incubator, such a specific position is registered as coordinate information, and when manipulating on the cell, a moving operation is performed which moves the observation position to the registered coordinate position. However, while the incubation temperature within the incubator is maintained in 37° C., the cell manipulation for example is performed at room temperature, and thus, errors may occur in the return to origin operations using the X-axis sensor and the Y-axis sensor due to such temperature difference. As a result, the observation position may not be moved to the same position that is registered at the time of coordinate registration. 
         [0129]    Thus, the position detection errors of the X-axis sensor  5  and the Y-axis sensor  6  are reflected in the positioning control as follows. 
         [0130]    In the observation device according to the invention, a relationship between the temperature and the detected distance as shown in  FIG. 30A  and a relationship between the response difference and the detected distance as shown in  30 B respectively are illustrated graphically or in a table format beforehand. Then, at the time of cell manipulation, the response difference under a present usage condition is computed from the relationship of  FIG. 30A  by obtaining the position detection error, and by applying that value in the relationship of  FIG. 30B , the detected distance under the present usage environment is derived. Similarly, at the time of coordinate registration, the response difference is computed from the relationship of  FIG. 30A  and the position detection error, and the detected distance at the time of coordinate registration can be derived by applying that value in the relationship of  FIG. 30B . 
         [0131]    The difference between the detected distance under the present usage environment and the detected distance at the time of coordinate registration is set as dp, and by operating the coordinate difference dp to the registration coordinate value (i.e. adding in the illustrated example), the origin position that is the same as the origin position at the time of coordinate registration can be duplicated. Thus, it becomes possible to move the observation position at the time of cell manipulation to the same position as that at the time of coordinate registration. 
         [0132]    As described above, according to the observation device of the present invention, it is possible to acquire each feed amount error of the X-axis drive mechanism and of the Y-axis drive mechanism, and each position detection error of the X-axis origin sensor and of the Y-axis origin sensor individually. As a result, in a positioning control with respect to the X-axis drive mechanism and the Y-axis drive mechanism, a control operation can be performed by taking into consideration the feed amount errors of both drive mechanisms  2  and  3  and the position detection errors of the both sensors  2  and  3 . Thus, it becomes possible to prevent deterioration of positioning accuracy due to the change over time and change in environmental conditions. 
         [0133]    In addition, highly accurate positioning can be achieved with an inexpensive mechanism system for the X-axis drive mechanism  2  and the Y-axis drive mechanism  3 , without adopting an expensive ball screw mechanism that does not generate backlashes. 
         [0134]    The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims therefore are intended to be embraced therein. 
         [0135]    For example, instead of the image pickup device  16  for capturing an image of the test target  8 , various other optical detection means can be adopted which can accurately detect a point of time that the reciprocating body shifts from the resting state to the moving state without causing hysteresis, such as a displacement meter that captures a speckle pattern with a CCD camera by irradiating laser beam to the surface of the reciprocating body. 
         [0136]    Also, the test target  8  may be formed by deposition or paint application on a glass plate if the optical system of the observation device is a transmission type. However, if the optical system of the observation device is an incident-light type, it can be formed in pattern printing such as in black and white that at least causes a different in contrast. 
         [0137]    According to the conveyance control device, a control method of the conveyance device, and an observation device of the present invention, it is possible to acquire the feed amount error of the drive mechanism and the position detection error of the origin sensor individually, and as a result, in a positioning control of the reciprocating body, a control operation can be performed by individually taking into consideration the feed amount error and the position detection error.