Patent Publication Number: US-2009232486-A1

Title: Image capturing apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image capturing apparatus that captures an image of an observation object by imaging a plate-like container containing the observation object such as a liquid sample. 
     2. Description of the Invention 
     In recent years, as a scale of screening is rapidly widened in a field of drug discovery screening which is performed in pharmaceutical industries, a technique of high throughput screening (HTS) has been introduced, which finds a target chemical compound by efficiently estimating a large amount of specimen samples in a short time by using an automatic system. In this high throughput screening, after a dispensing operation or incubation is performed on the specimen sample, as an object, which is contained in the container such as a micro plate, various measurements such as fluorescence measurement, luminescence measurement, and absorption measurement are performed according to aims. 
     These measurements are performed so as to capture the image by imaging the container containing the specimen sample by a camera. For this reason, a dedicated image capturing apparatus is used (for example, refer to Patent Document 1). In an example shown in Patent Document 1, a micro plate is held in a horizontal attitude below the camera that is disposed such that the imaging direction of the camera faces downward. The camera images the micro plate from the upper surface side thereof to capture the image. 
     Patent Document 1: U.S. Pat. No. 6,377,346 
     However, in measurement of the specimen sample as the object in the container such as the micro plate, there is a need for changing the imaging direction according to a portion of a measurement object. For example, when the measurement of the specimen sample as the object in wells of the micro plate is performed, the image is typically captured from an aperture side of the wells. However, when cells in a culture medium that is attached on the bottom surface of the wells are the objects to be measured, there is a need for imaging the micro plate from the lower surface side. However, in a prior art shown in the example of Patent Document 1 described above, when the imaging direction is changed as described above, it is necessary to perform the measurement in a state where the entire apparatus is inversed. In addition, it is difficult to correspond to various measurement contents with good operability by using the same apparatus. 
     SUMMARY OF THE INVENTION 
     The present invention has been finalized in view of the above problem, and it is an object of the invention to provide an image capturing apparatus that is able to correspond to various measurement contents with good operability. 
     An image capturing apparatus of the present invention for capturing an image of an observation object by imaging a plate-like container in which the observation object is contained, includes: a housing unit in which an imaging unit having a horizontal first optical axis as an imaging optical axis, and an illumination unit having a second optical axis as an illumination optical axis which is set below the first optical axis to be parallel to the first optical axis are housed in a positional relation that the imaging unit and the illumination unit vertically overlap each other; a container holding unit which holds the plate-like container in a horizontal attitude at a selected observation position of a first observation position which is set at a side of an object to be imaged by the imaging unit so as to be at a middle-height position between the first optical axis and the second optical axis and a second observation position which is set at a position higher than the first optical axis above the first observation position; an optical path switching unit which is disposed at a middle position interposed between the first observation position and the second observation position and bends an optical path of light irradiated along the first optical axis to either side of the first observation position or the second observation position; an optical member which is disposed between the imaging unit and the middle position, transmits light in a predetermined wavelength region of the light which is in an incident direction to the imaging unit along the first optical axis to enter the transmitted light in the imaging unit, and reflects downward the light in the other wavelength regions; an optical member moving mechanism which moves the optical member so that the first optical axis and the optical member intersect each other or separate from the intersecting state; and an illumination light reflecting mirror which is disposed below the optical member intersecting the first optical axis, reflects illumination light which is irradiated from the illumination unit along the second optical axis toward the optical member, and further enters the reflected light of the illumination light which is incident on the optical member to the optical path switching unit. 
     According to the image capturing apparatus of the invention, the imaging unit having the first optical axis and the illumination unit having the second optical axis are housed in the positional relation that the imaging unit and the illumination unit vertically overlap each other. In addition, the plate-like container is held in a horizontal attitude at a selected observation position of the first observation position and the second observation position which are set at positions higher and lower than the first optical axis, respectively, at the side of the object to be imaged by the imaging unit. In addition, using the optical path switching unit that is disposed at the middle position interposed between the first observation position and the second observation position, the optical path of the light irradiated along the first optical axis is bent to any one side of the first observation position and the second observation position. Accordingly, it is possible to correspond to various measurement contents with good operability by using the same apparatus because the observation is allowed to be performed from any one of the upper side and the lower side of the container holding unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view illustrating the entire configuration of an image capturing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a partially sectional view of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 3  is a partially sectional view of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 4  is a partially sectional view of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 5  is a partially sectional view of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 6  is a view illustrating an operation of a container transporting unit of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 7  is a view illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 8  is a view illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 9  is a view illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 10  is a view illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention; 
         FIG. 11  is a view illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention; and 
         FIG. 12  is a view illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, embodiments of the present invention will be described with reference to the accompanying drawings.  FIG. 1  is a side view illustrating the entire configuration of the image capturing apparatus according to an embodiment of the present invention.  FIGS. 2 to 5  are partially sectional views of the image capturing apparatus according to the embodiment of the present invention.  FIG. 6  is a view illustrating an operation of a container transporting unit of the image capturing apparatus according to the embodiment of the present invention.  FIGS. 7 to 12  are views illustrating measurement processing of the image capturing apparatus according to the embodiment of the present invention. 
     First, the entire configuration of the image capturing apparatus  1  will be described with reference to  FIG. 1 . The image capturing apparatus  1  has a function that captures an image of an observation object by imaging a plate-like container containing the observation object. In the embodiment, liquid samples as the observation object are contained in plural wells of a micro plate that is a plate-like container. These liquid samples are imaged so as to capture the image thereof by using a camera. Therefore, various kinds of measurement processing such as fluorescence measurement, luminescence measurement, and absorption measurement are performed on the liquid sample as the object on the basis of captured image information. 
     In  FIG. 1 , the image capturing apparatus  1  is configured such that an imaging unit  3 , an illumination unit  4 , a container elevating unit  5 , a container transporting unit  6 , an optical path switching unit  7 , a diachronic mirror unit  8 , and an illumination light reflecting unit  9  are disposed in a housing unit  2 . Hereinafter, configurations and functions of respective units will be described with reference to  FIGS. 2 to 6 . In addition,  FIG. 2  and  FIG. 3  show a horizontal section of the inside of the housing unit  2  viewed from the upper surface side, and  FIG. 4  shows the horizontal section in which the optical switching unit  7  and the dichroic mirror unit  8  are removed from the horizontal section. In addition,  FIG. 5  shows the horizontal section in which the illumination light reflecting unit  9  is removed from  FIG. 4 , and  FIG. 6  is an enlarged view illustrating details of configuration and operation of the container elevating unit  5  and the container transporting unit  6 . 
     The configuration of the imaging unit  3  will be described. A base plate  11  is horizontally disposed on a right half portion in the inside of the housing unit  2 . In addition, a camera  13  and an imaging optical system  15  are held on brackets  12  and  14 , respectively, each of which is erectly provided on the base plate  11 , in a horizontal attitude in order to match optical axes of the camera  13  and the imaging optical system  15  with a first optical axis A 1  which is horizontally set. The camera  13  includes an image element such as a CCD, and receives imaging light from the object to be imaged, which is positioned on a left half portion in the housing unit  2 , through the imaging optical system  15  to output a video signal. 
     The imaging unit  3  includes an optical chopper  16  and a rotating filter  18 . The optical chopper  16  is configured such that a rotating disc  16   a , in which transmission openings (not shown) are provided, is driven to rotate by a motor  17 . The imaging light which is incident through the imaging optical system  15  is received to the camera  13  only in the state where the transmission opening is matched with the first optical axis A 1  by rotating the rotating disc  16   a , and the imaging light in the other states is blocked by the rotating disc  16   a . By controlling rotation of the motor  17 , the camera  13  can be exposed at predetermined timing by a predetermined period of time. 
     The rotating filter  18  is configured such that a rotating disk  20  on which plural filters  20   a  are attached is driven to rotate by a motor  19 . In addition, the imaging light that is incident through the imaging optical system  15  by matching the filter  20   a  with the first optical axis A 1  is received to the camera  13  in a state of being filtered according to filter characteristics of the attached filters  20   a . That is, it is possible that only a specific light of the imaging light from the object to be imaged is incident on the camera  13 , or the imaging light in which the specific light is removed is incident on the camera  13 . In the embodiment, since the fluorescence measurement is included in the measurement method as the object, a filter having characteristics of transmitting fluorescence and blocking excitation light from a light source is included in the plural filters  20   a  which are attached on the rotating disc  20 . 
     Next, a structure of the illumination unit  4  that is disposed below the imaging unit  3  will be described. In the housing unit  2 , a base plate  21  is horizontally disposed below the base plate  11 , and brackets  22  and  24  are erectly provided on the base plate  21 . The bracket  22  and the bracket  24  are held in a horizontal attitude in order to match optical axes of an LED light source unit  23  and an illumination optical system  25  with a second optical axis A 2  which is horizontally set. The LED light source unit  23  has an LED (light emitting diode) as a light source built therein, and the illumination light emitted from the LED light source unit  23  is irradiated in a direction along the second optical axis A 2  with respect to the object to be imaged through the illumination optical system  25 . 
     The illumination unit  4  includes a rotating filter  26  for filtering the illumination light from the LED light source unit  23 . The rotating filter  26  is configured such that a rotating disc  28  on which filters  28   a  are attached is driven to rotate by a motor  27 . In addition, by matching the filter  28   a  with the second optical axis A 2 , the illumination light which is emitted by the LED light source unit  23  is irradiated through the illumination optical system  25  in a state of being filtered according to the filter characteristics of the attached filers  28   a . In the embodiment, since the fluorescence measurement is included in the measurement method as the object, an excitation filter is included in the plural filters  28   a  which are attached on the rotating disc  28 , which has a function of extracting light having a wavelength required for exciting a fluorescent material as the object from the illumination light which is emitted from the LED light source unit  23 . By using the imaging unit  3  and the illumination unit  4  having the configuration and the function described above, it is possible to perform a time-resolved fluorescence technique of measuring a temporal transition of intensity in fluorescence, which is emitted from the object to be measured, by the imaging capturing apparatus  1 . 
     In above-mentioned configuration, the imaging capturing apparatus  1  is configured such that the imaging unit  3  having the horizontal first optical axis A 1  as an imaging optical axis and the illumination unit  4  having the second optical axis A 2  as an illumination optical axis which is horizontally set below the first optical axis A 1  to be parallel to the first optical axis A 1  are included in the housing unit  2 . In addition, the housing unit  2  houses the imaging unit  3  and the illumination unit  4  in a positional relation therebetween to be vertically disposed so as to be overlapped with each other. Even if it is necessary to change the observation direction according to the portions of the measurement object, by disposing the imaging unit  3  and the illumination unit  4  in the positional relation described above, it is possible to correspond to various measurement contents with the good operability by using the same apparatus, which will be describe later. 
     Next, the container elevating unit  5  for holding and elevating the micro plate  10  which is a plate-like container in which a liquid sample (observation object) is contained will be described. In addition, an example of the micro plate  10  in which wells are provided is shown as the plate-like container. However, as the plate-like container, a glass plate may be used in which the liquid sample is simply contained. An elevating table  31  is disposed to be erected at the left end portion in the housing unit  2 . Further, a substantial plate-like container holding unit  33  (refer to  FIG. 6 ) is connected with an elevating member  31   a  of the elevating table  31  via a connecting bracket  32 . A position holding member  33   a  for placing the micro plate  10  on a fixed position is provided on the container holding unit  33 . In addition, four corner portions of the container holding unit  33  are cut so as to form corner cut portions  33   b . By driving the elevation table  31  in a state where the micro plate  10  is placed on the container holding unit  33 , the micro plate  10  is elevated together with the container holding unit  33  (arrow a). 
     A first observation position [P 1 ] and a second observation position [P 2 ] for imaging and observing the micro plate  10  by the imaging unit  3  are set in a stroke range in which the container holding unit  33  is elevated by the elevating table  31 . The first observation position [P 1 ] is set at a side of the object to be imaged by the imaging unit  3 , that is, at a middle-height position between the first optical axis A 1  and the second optical axis A 2  in the left half portion in the housing unit  2 . Further, the second observation position [P 2 ] is set at a position higher than the first optical axis A 1  above the first observation position [P 1 ]. By driving the elevating table  31 , it is possible to position the container holding unit  33  on which the micro plate  10  is placed at any of the first observation position [P 1 ] and the second observation position [P 2 ]. Accordingly, the micro plate  10  which is held by the container holding unit  33  is held at any one of the first observation position [P 1 ] and the second observation position [P 2 ]. 
     That is, in the above-mentioned configuration, the container holding unit  33  is elevated by the elevating table  31 , and holds the micro plate  10  which is the plate-like container in a horizontal attitude at a selected observation position of the first observation position [P 1 ] and the second observation position [P 2 ]. The elevating table  31  is an elevating mechanism for elevating the container holding unit  33 . The elevating mechanism moves the container holding unit  33  to the first observation position [P 1 ] or the second observation position [P 2 ]. 
     Next, the optical path switching unit  7  will be described. On an extended line of the first optical axis A 1 , the optical path switching unit  7  is disposed at a middle position [PM] between the first observation position [P 1 ] and the second observation position [P 2 ]. The optical path switching unit  7  is configured such that two mirrors of a first mirror  44 A and a second mirror  44 B are provided to freely move in a Y direction by a moving table  41  (refer to  FIG. 2 ) which is disposed horizontally in the Y direction at a position of the same height as that of the first optical axis A 1 . 
     Mirror holding members  43 A and  43 B are connected to a moving member  41   a  of the moving table  41  via a connecting bracket  42 . Further, the mirror holding member  43 A and  43 B hold a first mirror  44 A and a second mirror  44 B that are held in an inclined attitude of 45° down and 45° up, respectively. The first mirror  44 A and the second mirror  44 B are moved in the Y direction (refer to arrow b shown in  FIG. 2 ) by driving the moving table  41 , and thus it is possible to move any one of them to a position intersecting the first optical axis A 1 . The moving table  41  is a mirror moving mechanism that horizontally moves the first mirror  44 A and the second mirror  44 B. 
     That is, the second mirror  44 B is moved to the position intersecting the first optical axis A 1  by driving the moving table  41  to move the moving member  41   a  to the position of arrow b shown in  FIG. 2 . In addition, the first mirror  44 A is moved to the position intersecting the first optical axis A 1  by further moving the moving member  41   a  in the Y direction (upper side in  FIG. 2 ). Furthermore, both the first mirror  44 A and the second mirror  44 B can be separated from the position intersecting the first optical axis A 1  by moving the moving member  41   a  to a position of arrow e shown in  FIG. 3 . Therefore, a space above the container holding unit  33  becomes clear, and thus it is possible to elevate the container holding unit  33 , on which the micro plate  10  is held, in the container elevating unit  5 . 
     In a state that the first mirror  44 A is at the position intersecting the first optical axis A 1 , light which is incident on the first mirror  44 A along the first optical axis A 1  proceeds along an optical path L 1  which is extended from the first optical axis A 1  bent to the lower side in a vertical direction to the side of the first observation position [P 1 ]. In addition, opposite to the direction of the light, the light which is incident on the first mirror  44 A from the lower side in the vertical direction along the optical path L 1  proceeds in a direction to the imaging unit  3  along the first optical axis A 1 . Similarly, in a state that the second mirror  44 B is at the position intersecting the first optical axis A 1 , the light which is incident on the second mirror  44 B along the first optical axis A 1  proceeds along an optical path L 2  which is extended from the first optical axis A 1  bent to the upper side in the vertical direction to the side of the second observation position [P 2 ]. In addition, opposite to the direction of the light, the light which is incident on the second mirror  44 B from the upper side in the vertical direction along the optical path L 2  proceeds in a direction to the imaging unit  3  along the first optical axis A 1 . 
     That is, in the above-mentioned configuration, the optical path switching unit  7  is disposed in the middle position [PM] interposed between the first observation position [P 1 ] and the second observation position [P 2 ], and has a function to bend the optical path of the light irradiated along the first optical axis A 1  to any side of the first observation position [P 1 ] (optical path L 1 ) or the second observation position [P 2 ] (optical path L 2 ). The optical path switching unit  7  is configured to include: the first mirror  44 A and the second mirror  44 B which bend the direction of the optical path along the first optical axis A 1  to the sides of the first observation position [P 1 ] and the second observation position [P 2 ], respectively; and the mirror moving mechanism which horizontally moves the first mirror  44 A and the second mirror  44 B. 
     By adopting the configuration described above, in measurement of the liquid sample as the object in the micro plate  10  which is held on the container holding unit  33 , it is possible to easily switch the direction to observe the micro plate  10 , that is, an upper surface observation for observing the micro plate  10  from the upper surface side thereof and a lower surface observation for observing the micro plate  10  from the lower surface side thereof. In addition, in switching of the observation direction, since the optical path switching unit  7  is positioned at the middle position [PM] between the first observation position [P 1 ] and the second observation position [P 2 ], the optical path length in the case of the upper surface observation becomes equal to the optical path length in the case of the lower surface observation. For this reason, even though the observation position is changed, it becomes possible that optical treatments in irradiating of the illumination light by the illumination unit  4  and in receiving the imaging light by the imaging unit  3  are performed as the same. As a result, the configuration is preferable in manufacturing the apparatus or in rapid measuring operations. 
     Next, the container transporting unit  6  which carries in the micro plate  10  into the housing unit  2  or carries out the micro plate  10  from the housing unit  2  will be described. As shown in  FIGS. 1 and 2 , an opening  2   a  which is communicated with the outside is provide in the vicinity of a lower limit position for elevating the container holding unit  33  in the side surface of the housing unit  2 , and a shutter  2   b  is provided to be freely opened or closed at the opening  2   a . As shown in  FIG. 5 , a moving table  34  is disposed in the housing unit  2  in the Y direction, and a connecting bracket  35  that is horizontally extended in the X direction is connected to a moving member (not shown) of the moving table  34 . The connecting bracket  35  is moved in the Y direction (refer to arrow i) by driving the moving table  34 . 
     A plate delivery unit  36  that holds the micro plate  10  is provided on the tip portion of the connecting bracket  35 . The plate delivery unit  36  protrudes to the outside of the housing unit  2  through the opening  2   a  by driving the moving table  34  to move the connecting bracket  35  to the side of the opening  2   a . As shown in  FIG. 6 , the plate delivery unit  36  includes two fork-like holding arms  36   a  which protrudes outside. A delivery space  36   b  is formed between two holding arms  36   a  so as to have a size of the opening through which the container holding unit  33  of the container elevating unit  5  can be inserted. 
     Plate holding units  36   c  are provided on the holding arms  36   a  corresponding to four corner portions of the micro plate  10 . The micro plate  10  is held by the plate delivery unit  36  by positioning the respective corner portions of the micro plate  10  at the plate holding units  36   c . Supplying or withdrawing of the micro plate  10  to the plate delivery unit  36  is performed in a state that the plate delivery unit  36  protrudes to the outside of the housing unit  2  through the opening  2   a.    
     That is, the micro plate  10  is supplied from the outside of the housing unit  2  to the plate delivery unit  36  which moves the micro plate  10  into the housing unit  2 , and a plate delivery operation is performed between the container holding unit  33  of the container elevating unit  5  and the plate delivery unit  36 , so that the micro plate  10  is delivered to the container holding unit  33 . After completing measurement processing, the micro plate  10  is delivered from the container holding unit  33  to the plate delivery unit  36 , and then is carried out to the outside of the housing unit  2  through the opening  2   a . The moving table  34 , the connecting bracket  35 , and the plate delivery unit  36  configure a container transporting unit  6  which carries in the micro plate  10  to a path for moving the container holding unit  33  by the elevating table  31 . 
     The plate delivery operation described above is performed as follows. First, in delivering the micro plate  10  from the plate delivery unit  36  to the container holding unit  33 , the container holding unit  33  is ascended through the delivery space  36   b  in a state that the container holding unit  33  is positioned at the lower side of the plate delivery unit  36 . Therefore, the position holding members  33   a  which are provided on the container holding unit  33  come into contact with the micro plate  10  from the lower surface, and the micro plate  10  is lifted up by the container holding unit  33 , and thus the delivering the micro plate  10  held by the plate holding units  36   c  to the container holding unit  33  is completed. In addition, in delivering the micro plate  10  from the container holding unit  33  to the plate delivery unit  36 , the above-mentioned plate delivery operation is performed in reverse. 
     In the plate delivery operation, since the corner cut portions  33   b  are provided on the respective corner portions of the container holding unit  33 , it is possible to perform the delivery of the micro plate  10  without interference between the plate holding unit  36   c  and the container holding unit  33 . That is, in the above-mentioned configuration, the opening  2   a  as a container entrance is formed on the side surface of the housing unit  2 . In addition, the container transporting unit  6  which carries in the micro plate  10  from the opening  2   a  to transport the micro plate  10  to the path for moving the container holding unit  33  by the elevating table  31  is included. 
     Next, the dichroic mirror unit (optical member unit)  8  will be described. In  FIG. 1 , the dichroic mirror unit  8  is disposed between the imaging unit  3  and the middle position [PM] on which the optical path switching unit  7  is positioned. As shown in  FIGS. 1 and 2 , the dichroic mirror unit  8  includes two tables of a first moving table  51 A and a second moving table  51 B which are disposed in the Y direction. Further, a connecting bracket  52 A and a connecting bracket  52 B which are extended downward are mounted on the first moving table  51 A and the second moving table  51 B via moving members  51   a , respectively. 
     Two dichroic mirrors  54 A and  54 B are connected to the connecting bracket  52 A via a mirror holding member  53 A. In addition, two dichroic mirror  54 C and  54 D are connected to the connecting bracket  52 B via a mirror holding member  53 B. The dichroic mirrors  54 A,  54 B,  54 C, and  54 D are optical members with characteristics that light in a specific wavelength region is transmitted and light in the other wavelength regions is reflected. In the embodiment, since different kinds of measurement such as the fluorescence measurement and the absorption measurement are performed by the same apparatus, the dichroic mirror unit  8  includes plural dichroic mirrors, each of which has a different wavelength characteristic. In addition, in the embodiment, the dichroic mirrors are used as the optical member to transmit the light in the specific wavelength region and reflect the light in the other wavelength regions. However, other things such as a dichroic prism having the same function as that of the dichroic mirror may be used as the optical member described above. 
     As shown in  FIG. 2 , the dichroic mirrors  54 A and  54 B are moved in the Y direction by driving the first moving table  51 A (refer to arrow c), and thus it is possible to move any one of them to the position intersecting the first optical axis A 1 . In addition, the dichroic mirrors  54 C and  54 D are moved in the Y direction by driving the second moving table  51 B (refer to arrow d), and thus it is possible to move any one of them to the position intersecting the first optical axis A 1 . Furthermore, as shown in  FIG. 3 , by driving the first moving table  51 A and the second moving table  51 B to move the moving member  51   a  to the position shown by arrows f and g, all the dichroic mirrors  54 A,  54 B,  54 C, and  54 D are separated from the position intersecting the first optical axis A 1 . Therefore, when the function of the dichroic mirrors is not requested according to the kinds and forms of measurement it is possible to separate all the dichroic mirrors  54 A,  54 B,  54 C, and  54 D from the position intersecting the first optical axis A 1 . 
     That is, in the above-mentioned configuration, the dichroic mirrors  54 A,  54 B,  54 C, and  54 D are disposed between the imaging unit  3  and the middle position [PM] on which the optical path switching unit  7  is positioned, and have the function that the light in the predetermined wavelength region of the light which is in an incident direction to the imaging unit  3  along the first optical axis A 1  is transmitted to be incident on the imaging unit  3  and the light in the other wavelength regions is reflected downward. In addition, the first moving table  51 A and the second moving table  51 B have the function as an optical member moving mechanism that moves these dichroic mirrors in order to intersect the first optical axis A 1  and the dichroic mirrors  54 A,  54 B,  54 C, and  54 D or to be separated from the intersecting state. In the embodiment, the plural dichroic mirrors having different characteristics are included, and these plural dichroic mirrors are selectively positioned at the position intersecting the first optical axis A 1  by the optical member moving mechanism. 
     Next, the illumination light reflecting unit  9  which is provided below the optical path switching unit  7  and the dichroic mirror unit  8  will be described. In  FIG. 1 , below the optical path switching unit  7  and the dichroic mirror unit  8 , a mirror moving mechanism  61  is horizontally disposed below the second optical axis A 2  in the X direction. An illumination light reflecting mirror  63  is connected to the moving member  61   a , which is mounted on the mirror moving mechanism  61 , with an inclination angle of 45° through a mirror holding member  62 . A position of the height of the middle point of the illumination light reflecting mirror  63  is matched with the second optical axis A 2 , and the illumination light which is irradiated from the illumination unit  4  along the second optical axis A 2  is incident on the illumination light reflecting mirror  63  in a horizontal direction. 
     The illumination light reflecting mirror  63  is moved in the X direction by driving the mirror moving mechanism  61 . Therefore, the mirror moving mechanism  61  becomes an illumination light reflecting mirror moving mechanism. For this reason, it is possible to selectively position the illumination light reflecting mirror  63  at a first reflection position [P 3 ] on which the illumination light reflecting mirror  63  is positioned immediately below the dichroic mirror unit  8 , or at a second reflection position [P 4 ] on which the illumination light reflecting mirror  63  is positioned immediately below the optical path switching unit  7 . When the illumination light reflecting mirror  63  is positioned at the first reflection position [P 3 ], the illumination light which is incident along the second optical axis A 2  by the illuminating unit  4  is reflected to the upper side in a vertical direction along an optical path L 3  by the illumination light reflecting mirror  63  and is incident on the dichroic mirror  54 A of the dichroic mirror unit  8 . Then, the reflected light of the light that is incident on the dichroic mirror  54 A is incident on any one of the first mirror  44 A and the second mirror  44 B of the optical path switching unit  7  along the first optical axis A 1 . 
     That is, the illumination light reflecting mirror  63  of the illumination light reflecting unit  9  is disposed below the dichroic mirror intersecting the first optical axis A 1  in the dichroic mirror unit  8 , and has the function that the illumination light which is irradiated from the illumination unit  4  along the second optical axis A 2  is reflected toward the dichroic mirror and the reflected light of the illumination light which is further incident on the dichroic mirror is incident on the optical path switching unit  7 . The illumination light reflecting unit  9  is configured to include the illumination light reflecting mirror moving mechanism which selectively positions the illumination light reflecting mirror  63  at a position below the dichroic mirror unit  8  or at a position below the first observation position [P 1 ] by moving the illumination light reflecting mirror  63  along the second optical axis A 2 . 
     The image capturing apparatus  1  is configured in the same manner as described above. Hereinafter, an actual example of various measurements processing, which is performed on the micro plate  10  as the object by using the image capturing apparatus  1 , will be described. First, the most basic fluorescence measurement, that is, the case where the fluorescence measurement is performed on the aperture side of the wells  10   a  of the micro plate  10  as a surface of the measurement object will be described with reference to  FIG. 7 . In this case, the micro plate  10  that contains the liquid sample in the wells  10   a  is held on the container holding unit  33  to position at the first observation position [P 1 ]. 
     In the illumination light reflecting unit  9 , the illumination light reflecting mirror  63  is positioned at the first reflection position [P 3 ]. Further, in the dichroic mirror unit  8 , the dichroic mirror  54 A, which has a fluorescence measuring characteristic, that is, a characteristic for reflecting the excitation light by transmitting fluorescence, is moved to the position intersecting the first optical axis A 1 . Further, in the optical path switching unit  7 , the first mirror  44 A which is disposed in a direction (optical path L 1 ) of the first optical axis A 1  bent downward is positioned at the position intersecting the first optical axis A 1 . 
     In this state, the illumination light in the specific wavelength region, that is, the excitation light for exciting the fluorescent material as the object is incident on the illumination light reflecting mirror  63  along the second optical axis A 2  through the illumination light optical system  25  by operating the illumination unit  4  (arrow j 1 ). Therefore, the excitation light is reflected to the upper side in a vertical direction (arrow j 2 ), and incident on the dichroic mirror  54 A of the dichroic mirror unit  8  from the lower side. Next, the incident light is reflected in the horizontal direction by the dichroic mirror  54 A and proceeds along the first optical axis A 1  to be incident on the first mirror  44 A (arrow j 3 ). Further, the incident light is reflected to the lower side along the optical path L 1  by the first mirror  44 A (arrow j 4 ) to be incident on the liquid sample in the wells  10   a  from the upper side. 
     The excitation light generates unique fluorescence because the fluorescent material in the liquid sample is excited. The imaging light including the fluorescence is incident on the first mirror  44 A along the optical path L 1  (arrow j 5 ), and then the imaging light which is reflected in the horizontal direction by the first mirror  44 A proceeds along the first optical axis A 1  to be incident on the dichroic mirror  54 A. Since the dichroic mirror  54 A has the characteristic of reflecting the excitation light by transmitting the fluorescence, only the fluorescence generated from the micro plate  10  is transmitted through the dichroic mirror  54 A (arrow j 6 ). The transmitted light is imaged by the imaging unit  3 . That is, the transmitted light is incident on the camera  13  through the imaging optical system  15  (refer to  FIG. 1 ), so that the image information is obtained. Therefore, fluorescence intensity of the fluorescent material in the liquid sample is measured on the basis of the image information. 
     Next, an example of the fluorescence measurement which is performed in the case where the object to be measured exists on the bottom surface of the wells  10   a  will be described with reference to  FIG. 8 . In this case, the micro plate  10  in which the liquid sample is contained is positioned at the second observation position [P 2 ]. In addition, in the illumination light reflecting unit  9 , the illumination light reflecting mirror  63  is positioned at the first reflection position [P 3 ]. Further, in the dichroic mirror unit  8 , the dichroic mirror  54 A for the fluorescence measurement is moved to the position intersecting the first optical axis A 1 . Further, in the optical path switching unit  7 , the second mirror  44 B which is disposed in a direction (optical path L 2 ) of the first optical axis A 1  bent upward intersects the first optical axis A 1 . 
     In this state, the excitation light is incident on the illumination light reflecting mirror  63  along the second optical axis A 2  through the illumination optical system  25  by operating the illumination unit  4  (arrow k 1 ). Therefore, the excitation light is reflected to the upper side in a vertical direction (arrow k 2 ), and is incident on the dichroic mirror  54 A of the dichroic mirror unit  8  from the lower side. Further, the incident light is reflected in the horizontal direction by the dichroic mirror  54 A along the first optical axis A 1  (arrow k 3 ). Then, the incident light is further reflected to the upper side along the optical path L 2  by the second mirror  44 B (arrow k 4 ) to be incident on the liquid sample in the wells  10   a.    
     When the excitation light is incident on the object to be measured such as cells existing on the bottom surface of the wells  10   a , the object to be measured generates the unique fluorescence by being excited. The imaging light including the fluorescence is incident on the second mirror  44 B along the optical path L 2  (arrow k 5 ), and then the imaging light which is reflected in the horizontal direction by the second mirror  44 B proceeds along the first optical axis A 1  to be incident on the dichroic mirror  54 A. Since the dichroic mirror  54 A has the characteristic of reflecting the excitation light by transmitting the fluorescence, only the fluorescence generated from the micro plate  10  is transmitted through the dichroic mirror  54 A (arrow k 6 ). Similar to the example shown in  FIG. 7 , the transmitted light is imaged by the imaging unit  3 . 
     Next, an example of the fluorescence measurement in which the fluorescence is generated from the object to be measured in a state where the illumination light is absorbed into the liquid sample contained in the wells  10   a  will be described with reference to  FIG. 9 . In this case, the micro plate  10  in which the liquid sample is contained is positioned at the first observation position [P 1 ], and in the illumination light reflecting unit  9 , the illumination light reflecting mirror  63  is positioned at the second reflection position [P 4 ] below the micro plate  10 . In addition, in the optical path switching unit  7 , the first mirror  44 A which is disposed on the first optical axis A 1  bent downward intersects the first optical axis A 1 . Further, in the dichroic mirror unit  8 , the dichroic mirror  54 A for the fluorescence measurement is moved to the position intersecting the first optical axis A 1 . 
     In this state, the excitation light is incident on the illumination light reflecting mirror  63  along the second optical axis A 2  through the illumination optical system  25  by operating the illumination unit  4  (arrow  11 ). Therefore, the excitation light is reflected to the upper side in a vertical direction (arrow  12 ), and is incident on the liquid sample in the wells  10   a  of the micro plate  10  from the lower side. When the excitation light is absorbed into the liquid sample, the object to be measured generates the unique fluorescence since the fluorescent material is excited. The imaging light including the fluorescence is incident on the first mirror  44 A along the optical path L 2  (arrow  13 ), and then the imaging light which is reflected by the first mirror  44 A proceeds in the horizontal direction along the first optical axis A 1  to be incident on the dichroic mirror  54 A. Since the dichroic mirror  54 A has the characteristic of reflecting the excitation light by transmitting the fluorescence, only the fluorescence generated from the micro plate  10  is transmitted through the dichroic mirror  54 A (arrow  14 ). Similar to the examples shown in  FIGS. 7 and 8 , the transmitted light is imaged by the imaging unit  3 . 
     Next, an example of the measurement in which absorbance of the light to be absorbed by the liquid sample in the wells  10   a  is measured will be described with reference to  FIG. 10 . In this case, in order to irradiate measurement light to be used in measuring from the lower side of the micro plate  10 , the micro plate  10  in which the liquid sample is contained is positioned at the first observation position [P 1 ] similar to the measurement example shown in  FIG. 9 . Then, in the illumination light reflecting unit  9 , the illumination light reflecting mirror  63  is positioned at the second reflection position [P 4 ] below the micro plate  10 . In addition, in the optical path switching unit  7 , the first mirror  44 A intersects the first optical axis A 1 . Further, since the dichroic mirrors are not used in this measurement example, all the dichroic mirrors  54 A,  54 B,  54 C, and  54 D in the dichroic mirror unit  8  are evacuated from the position intersecting the first optical axis A 1 . 
     In this absorption measurement, the measurement light for the absorption measurement is irradiated by operating the illumination unit  4  along the second optical axis A 2  (arrow m 1 ), being incident on the illumination light reflecting mirror  63  to be reflected to the upper side in a vertical direction (arrow m 2 ), and being incident on the liquid sample contained in the wells  10   a  of the micro plate  10  from the lower side. In the incident light, the light that is further transmitted through the liquid sample after absorbed into the liquid sample in the wells  10   a  proceeds to the upper side in a vertical direction (arrow m 3 ) to be incident on the first mirror  44 A. The reflection light of the incident light proceeds in the horizontal direction along the first optical axis A 1 , thereby being received to the imaging unit  3 . As a result, the absorbance of the liquid sample in the wells  10   a  is measured. 
     Next, an example of the luminescence measurement that is performed by receiving the light generated due to a chemical reaction of the liquid sample itself in the wells  10   a  will be described with reference to  FIGS. 11 and 12 .  FIG. 11  shows an example where the light to be generated toward the upper side from the liquid sample in the wells  10   a  is the object to be measured. In this case, the micro plate  10  in which the liquid sample is contained is positioned at the first observation position [P 1 ]. Further, in the optical path switching unit  7 , the first mirror  44 A is moved to the position intersecting the first optical axis A 1 . 
     In this state, the light generated from the liquid sample in the wells  10   a  proceeds to the upper side to be incident on the first mirror  44 A (arrow n 1 ), being reflected in the horizontal direction by the first mirror  44 A and proceeding along the first optical axis A 1  (arrow n 2 ) to be received to the imaging unit  3 . Since the illumination light is not requested for the luminescence measurement, the functions of the illumination unit  4 , the dichroic mirror unit  8 , and the illumination light reflecting unit  9  are not used. Further, in the dichroic mirror unit  8 , all the dichroic mirrors are kept in a state of being separated. 
       FIG. 12  shows an example, in the same luminescence measurement, where the light emitted toward the lower side from the liquid sample in the wells  10   a  is the object to be measured. In this case, the micro plate  10  in which the liquid sample is contained is positioned at the second observation position [P 2 ]. Further, in the optical path switching unit  7 , the second mirror  44 B is moved to the position intersecting the first optical axis A 1 . In this state, the light emitted from the liquid sample in the wells  10   a  proceeds to the lower side to be incident on the second mirror  44 B (arrow o 1 ), reflecting in the horizontal direction by the second mirror  44 B and proceeding along the first optical axis A 1  (arrow o 2 ) to be received to the imaging unit  3 . Similar to the example shown in  FIG. 11 , the functions of the illumination unit  4 , the dichroic mirror unit  8 , and the illumination light reflecting unit  9  are not used also in this luminescence measurement. 
     As described above, in the image capturing apparatus of the invention, the imaging unit  3  having the first optical axis A 1  and the illumination unit  4  having the second optical axis A 2  are housed in the positional relation therebetween to be vertically overlapped with each other. In addition, the micro plate  10  which is the plate-like container is held in a horizontal attitude at a selected observation position of the first observation position [P 1 ] and the second observation position [P 2 ] which are set at the positions higher or lower than the first optical axis A 1 , respectively, at the side of the object to be imaged by the imaging unit  3 . In addition, by using the optical path switching unit  7  which is disposed at the middle position [PM] interposed between the first observation position [P 1 ] and the second observation position [P 2 ], the optical path of the light irradiated along the first optical axis A 1  is bent to any side of the first observation position [P 1 ] and the second observation position [P 2 ]. 
     With this configuration, in the image measurement of the micro plate  10  as the object, it is possible to capture the image of any side of the upper surface and the lower surface by easily switching the observation direction of the micro plate  10 . Accordingly, there is no need for the operation to inverse the entire apparatus which has been requested for the prior art when the image capturing direction is changed, but it is possible to correspond to various measurement contents with good operability by using the same apparatus because the measurement is allowed to be performed from any one of the upper side and the lower side of the micro plate  10 . 
     The image capturing apparatus of the present invention can advantageously correspond to various measurement contents with good operability by using the same apparatus, and is useful for the high throughput screening which estimates a large amount of specimen samples in pharmaceutical industries.