Patent Publication Number: US-2006000962-A1

Title: Biological sample observation system and biological sample observation method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to autofocusing on a cultured biological sample, used in a device which detects information caused by the reaction of the biological sample being cultured.  
      This application is based on Japanese Patent Application No. 2004-180064, the content of which is incorporated herein by reference.  
      2. Description of Related Art  
      Recently, automation of various functions of survey instruments using a microscope is in progress, and an autofocus function for focusing on a specimen has been an essential function for automation.  
      The microscope autofocus is also employed for a survey instrument for a specimen sealed in a slide glass. For example, there is known an autofocus technique using an infrared reflection film as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei08-82747. Furthermore, there is known a technique wherein a slide glass or a cover glass is focused on by an active AF system, then a specimen is accurately focused on using a passive AF system, as disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-91821.  
      The system using the microscope as mentioned above has been largely used for observing cells in a culturing process in a culturing container or the like.  
      Here, in order to grow cells in a culturing container, it has been needed to keep the environment of the culture such as the thermal environment at approximately 37° C., the carbon dioxide concentration in the culture gas at about 5%, and so on. Therefore, due to the temperature drift due to the temperature control for keeping the environment of the culture, the effect of cooling due to flowing of the culture gas, and the heating of a lamp house, and the like, thermal deformation of the mainframe components or the subject of observation readily occurs, and in the technique disclosed in Patent Document 1 and Patent Document 2, there is concern of frequent defocusing where the focal point is displaced with the passage of time.  
      Cells to be observed range over various types, and have a thickness of 5 to 10 μm on the average. Non-confocal observation measurement, confocal observation measurement, or the like are used according to the object of the observation, and an object lens of a high magnification has been used in many cases. Therefore, together with the abovementioned reasons, there has been concern of frequent defocusing where the focal position is displaced.  
      Therefore, in an observation device taking the form of a microscope, an autofocus operation has been performed at each time during observation of cells, so as to prevent defocusing. However, if an autofocus operation is performed at each time during the observation, there has been a problem of extending the time for observation due to the autofocus operation.  
      If the time for observation is extended, for example in a case of observing a large number of cells, the time interval from the observation of the first cell to the observation of the last cell becomes longer, causing a problem in that the results can not be dealt with as observation results for the same time.  
      That is, since cells change with the passage of time, the time for observation must also be controlled accurately in order to perform accurate observation. However, if as mentioned above the time of observation differs depending on the order of observation, there is a problem in that accurate results can not be obtained, even if sets of information obtained by observation are compared.  
      If a laser is used for the active autofocus, laser light is always irradiated on the cells. Therefore the time for photoirradiation of the cells is also increased. If the time for photoirradiation is extended, the concentration of active oxygen in the cells is increased, causing a problem in that the active oxygen damages the cells in the culturing process.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention was achieved in order to solve the above problems, and has an object to provide a biological sample observation system wherein light damage to the biological sample is decreased, and observation can be performed accurately and quickly over a long period of time.  
      In order to achieve the above object, the present invention provides the following means.  
      A biological sample observation system of the present invention which continuously obtains information on a biological sample that is cultured inside of a culturing container has: an imaging section which observes mutually different regions that are previously selected, among regions to be observed including the biological sample, through an object lens for observing the biological sample in the culturing container through a part of the culturing container; an autofocus section which detects the focusing of the object lens with respect to a predetermined region among the regions to be observed; and a focusing drive control section which controls the focusing of the object lens when the biological sample is observed using the imaging section, based on the detection result of the focusing previously performed by the autofocus section. After the focus detection is performed by the autofocus section, without being intervened by the focus detection using the autofocus section, and the different regions are continuously observed by the imaging section, with the focusing controlled by the focusing drive control section.  
      A biological sample observation system of the present invention which continuously obtains information on a biological sample that is cultured inside of a culturing container has: an observation device which observes mutually different regions that are previously selected, among regions to be observed including the biological sample, through an object lens for observing the biological sample in the culturing container through a part of the culturing container; an autofocus device which detects the focusing of the object lens with respect to a predetermined region among the regions to be observed; and a focusing drive control device which controls the focusing of the object lens when the biological sample is observed using the observation device, based on the detection result of the focusing previously performed by the autofocus device. After the focus detection is performed by the autofocus device, without being intervened by the focus detection using the autofocus section, and the mutually different regions are continuously observed by the observation device, with the focusing controlled by the focusing drive control device.  
      A biological sample observation method of the present invention in which information on a biological sample that is cultured inside of a culturing container is continuously obtained includes: a step for detecting by an autofocus section, the focusing of an object lens for observing a biological sample through a part of the culturing container, with respect to a predetermined region among the regions to be observed including the biological sample in the culturing container; a step for controlling by a focusing drive control section, the focusing of the object lens when the biological sample is observed, based on the detection result of the focusing previously performed by the autofocus section; and a step for observing through the object lens by an imaging section, mutually different regions that are previously selected, among the regions to be observed, with the focusing controlled by the focusing drive control section. After the focus detection is performed by the autofocus section, without being intervened by the focus detection using the autofocus section, and the different regions are continuously observed by the imaging section, with the focusing controlled by the focusing drive control section. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a perspective view showing a biological sample observation system according to a first embodiment of the present invention.  
       FIG. 2  is a schematic diagram showing the system structure of the biological sample observation system of  FIG. 1 .  
       FIG. 3  is a schematic diagram showing the structure of an AF unit  46  of  FIG. 2 .  
       FIG. 4  is a perspective view showing an incubator box of  FIG. 1 .  
       FIG. 5  is a perspective view showing another example of the incubator box in the present embodiment.  
       FIG. 6  is a cross-sectional view of a chamber of  FIG. 5 .  
       FIG. 7A  shows an example of a selected example of a scan method and a detection range in the present embodiment.  
       FIG. 7B  shows another example of a selected example of the scan method and the detection range in the present embodiment.  
       FIG. 7C  shows yet another example of a selected example of the scan method and the detection range in the present embodiment.  
       FIG. 7D  shows yet another example of a selected example of the scan method and the detection range in the present embodiment.  
       FIG. 8  is a flowchart showing the flow of measurement parameter setting in the present embodiment.  
       FIG. 9A  shows an observation area on a slide glass in the present embodiment.  
       FIG. 9B  shows an area on the slide glass in which the focal position is measured in the present embodiment.  
       FIG. 10A  shows a linear interpolation in the present embodiment.  
       FIG. 10B  shows a curvilinear interpolation in the present embodiment.  
       FIG. 11  shows the observation area and the area on the slide glass in which the focal position is measured in the present embodiment.  
       FIG. 12  is a flowchart showing the flow of measurement in the present embodiment.  
       FIG. 13  is a flowchart showing an image processing method in the present embodiment.  
       FIG. 14  is a flowchart showing the flow of data processing in the present embodiment.  
       FIG. 15  is a flowchart showing the flow of light quantity adjustment in the present embodiment.  
       FIG. 16  is a flowchart showing a supplying/exchanging method of a culture solution in the present embodiment.  
       FIG. 17  shows a tracked image of cells, showing the change of cells with the passage of time.  
       FIG. 18  is a flowchart showing the flow of measurement according to a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
      Hereunder is a description of a biological sample observation system according to a first embodiment of the present invention, with reference to  FIG. 1  to  FIG. 17 .  
       FIG. 1  is a perspective view showing the outline of the biological sample observation system according to the present embodiment.  FIG. 2  is a schematic diagram showing the system structure of the biological sample observation system thereof.  
      As shown in  FIG. 1  and  FIG. 2 , a biological sample observation system  10  schematically comprises a detection unit  20 , and a culturing unit  70 . The detection unit  20  and the culturing unit  70  are desirably arranged close to each other. More preferably, these units  20  and  70  are arranged in contact with each other.  
      As shown in  FIG. 1  and  FIG. 2 , the detection unit  20  schematically comprises a heat-insulating box  21  for containing cells (biological sample) CE inside, and a detection section  40  which measures the cells CE.  
      The heat insulating box  21  comprises; a heater (temperature maintaining section)  21 H which keeps the inside of the heat insulating box  21  warm at a predetermined temperature, a stage (holding device)  22  which holds an incubator box (culturing container)  100  described later, a transmission light source  23  which irradiates light to the cells CE, a fan  24  which makes uniform the temperature inside of the heat insulating box  21 , a UV lamp  25  which sterilizes the inside of the heat insulating box  21 , a carrier  26  which protects a culture solution circulation pipeline  77  and a culture gas supply pipeline  97  described later, an opening/shutting door  27  which is used for putting in and taking out the incubator box  100  or the like from the heat insulating box  21 , and a main power switch  28  which turns ON/OFF the main power source of the detection unit  20 .  
      The stage  22  has an X axis operation stage (holding device)  22 X, and a Y axis operation stage (holding device)  22 Y which are relatively moved in the mutually orthogonal directions, and scanning is controlled by a stage scanning section  29 .  
      The stage scanning section  29  comprises; an X axis coordinate detection section  30  which detects the X axis coordinate value of the X axis operation stage  22 X, an X axis scanning control section  31  which controls the operation (scan) of the X axis operation stage  22 X, a Y axis coordinate detection section  32  which detects the Y axis coordinate value of the Y axis operation stage  22 Y, and a Y axis scanning control section  33  which controls the operation (scan) of the Y axis operation stage  22 Y.  
      The X axis coordinate detection section  30  and the Y axis coordinate detection section  32  are arranged to respectively output the detected X coordinate of the X axis operation stage  22 X and Y coordinate of the Y axis operation stage  22 Y to a computer PC. The X axis scanning control section  31  and the Y axis scanning control section  33  are arranged to respectively control the scan of the X axis operation stage  22 X and the scan of the Y axis operation stage  22 Y, based on the instructions from the computer PC.  
      An example of a mechanism which drives the X axis operation stage  22 X and the Y axis operation stage  22 Y includes for example a combination of a motor and a ball screw.  
      The computer PC also controls the detection system of the cells CE, and analyzes the captured image of the cells CE as described later, as well as controlling the scan of the X axis operation stage  22 X and the scan of the Y axis operation stage  22 Y as described above. The X axis operation stage  22 X, the Y axis operation stage  22 Y, the detection system, and the analysis system, are controlled linked together.  
      A condenser lens  34  which focuses the light emitting from the transmission light source  23  onto the cells CE, is arranged between the transmission light source  23  and the incubator box  100 .  
      A shutter  35  may be provided between the condenser lens  34  and the incubator box  100 , or the shutter  35  may not be provided.  
      The fan  24  is arranged on the wall surface of the heat insulating box  21 . By operating the fan  24 , the air in the heat insulating box  21  is convected so that the temperature in the heat insulating box  21  can be readily kept uniform and constant.  
      The UV lamp  25  is connected to a UV lamp switch  36  arranged on the wall surface of the detection unit  20 . A timer  37  which controls the operation of the UV lamp  25  timewise is arranged between the UV lamp  25  and the UV lamp switch  36 . Furthermore, there is arranged a sterilization indicator lamp (not shown) which indicates if the UV lamp  25  is turned on.  
      For example, if the UV lamp switch  36  is pressed when the cells CE are not being measured, the counting of the timer  37  is started and the power is supplied to the UV lamp  25 , and UV light (ultraviolet light) is irradiated into the heat insulating box  21 . At the same time, the sterilization indicator lamp is also turned on. Then, after a predetermined time (for example, 30 minutes) has passed and the counting of the timer  37  is terminated, the timer  37  stops the power supply to the UV lamp  25  to terminate the irradiation of UV light. Moreover, the sterilization indicator lamp is also turned off.  
      The UV lamp  25  is controlled separately from the main power switch  28 , and can be operated even if the main power source is turned off.  
      The lighting time of the UV lamp  25  may be 30 minutes as mentioned above, or may be less than 30 minutes or longer than 30 minutes as long as the time allows the various bacteria in the heat insulating box  21  to be completely killed.  
      The opening/shutting door  27  is made from a metal such as an alumite coated aluminum, or a semitransparent resin having a high shading property. The structure of the opening/shutting door  27  is considered to be a hollow dual structure, and furthermore a structure having the aforementioned metal for the inside and resin for the outside.  
      By using the resin for the outside of the opening/shutting door  27 , the heat in the heat insulating box  21  can be kept from escaping from the opening/shutting door  27  to the outside. Moreover, using the alumite coated metal for the inside of the opening/shutting door  27 , deterioration in the lifetime of the opening/shutting door  27  due to the UV lamp  25  can be avoided.  
      If the opening/shutting door  27  has the dual structure of a metal or a metal and a resin, it is completely shaded. Therefore an observation window is desirably provided in a position to enable peeping into the incubator box  100 . Desirably a transparent resin or a glass is fitted into the peephole, and an openable and closable cover is arranged on the outside.  
      As shown in  FIG. 1  and  FIG. 2 , the detection section  40  comprises; a heater (temperature maintaining section)  40 H which keeps the inside of the detection section  40  warm at a predetermined temperature (for example, 37° C.), incident light sources  41 A and  41 B which irradiate the cells CE from the detection section  40  side, an optical path switch section  42  which switches the optical paths from the incident light sources  41 A and  41 B, a light quantity adjustment mechanism  43  which adjusts the light quantity of the irradiation light, a lens system  44  which focuses the irradiation light towards the cells CE, a filter unit  45  which controls the wavelength of the irradiation light and the wavelength of the detection light, an autofocus (AF) unit (autofocus section, autofocus device)  46  which performs the focusing operation on the cells CE, a revolver  47  comprising object lenses  48  having a plurality of magnifications and different properties, a detector (observation device)  49  which detects the detection light from the cells CE, a light quantity monitor  50  which measures the light quantity of the detection light, a fan  51  which makes uniform the temperature inside of the detection section  40 , and a cooling fan  52  which cools the inside of the detection section  40 .  
      The incident light sources  41 A and  41 B comprise for example mercury lamps or the like, and are arranged outside of the detection section  40 , and are respectively connected to a power source  53  which supplies their power.  
      Moreover, normally one incident light source, for example the incident light source  41 A is used. However, if the light quantity of the incident light source  41 A drops below a predetermined prescribed value, the illuminating light is irradiated from the incident light source  41 B, and the power source of the incident light source  41 A is turned off.  
      The optical path switch section  42  is formed to lead either one of the illuminating light from the incident light source  41 A or the illuminating light from the incident light source  41 B to the light quantity adjustment mechanism  43 . Moreover in the optical path switch section  42  there is arranged an optical path control section  54  which is connected to the computer PC described later to control the optical path switch section  42 , based on an instruction from the computer PC.  
      A shutter  42 S is arranged on the illuminating light emission side of the optical path switch section  42 , so as to perform transmission/shutdown control of the illuminating light.  
      A light quantity adjustment mechanism  43  is arranged on the illuminating light emission side of the shutter  42 S, so as to adjust the light quantity of the illuminating light transmitted through the shutter  42 S. As the mechanism, a well-known aperture mechanism may be used, or some other well-known mechanism and technique that can adjust the light quantity may be used.  
      Moreover, in the light quantity adjustment mechanism  43  there is arranged a light quantity control section  55  which is connected to the computer PC described later to control the light quantity adjustment mechanism  43  based on an instruction from the computer PC.  
      A lens system  44  is arranged on the illuminating light emission side of the light quantity adjustment mechanism  43 . The lens system  44  comprises a pair of lenses  44 A and  44 B, and an aperture  44 C arranged between the lens  44 A and the lens  44 B.  
      The filter unit  45  comprises an excitation filter  56 , a dichroic mirror  57 , and an absorption filter  58 . The excitation filter  56  is one which passes light (exciting light) having a wavelength that contributes to the fluorescence of the cells CE, among the illuminating light, and is arranged so that the illuminating light emitting from the lens system  44  is incident into the excitation filter  56 . The dichroic mirror  57  is an optical element that separates exciting light and fluorescent light. The dichroic mirror  57  is arranged so that the exciting light transmitted through the excitation filter  56  is reflected towards the cells CE, and the fluorescent light from the cells CE is transmitted. The absorption filter  58  is an optical element that separates fluorescent light from the cells CE, and the other unnecessary scattered light, and is arranged so that the light transmitted through the dichroic mirror  57  is incident thereinto.  
      A filter control section  46 C which controls the wavelength of the exciting light or the detection light (fluorescent light) emitting from the filter unit  45  based on an instruction from the computer PC described later, is arranged in the filter unit  45 .  
      One of each excitation filter  56 , dichroic mirror  57 , and absorption filter  58  may be used, or a plurality of them may be used.  
       FIG. 3  shows the schematic structure of the AF unit  46 .  
      As shown in  FIG. 2  and  FIG. 3 , the AF unit  46  is arranged on the exciting light emission side of the filter unit  45 , so that the exciting light is focussed onto the cells CE through the object lens  48 , based on the instruction from the computer PC described later.  
      More specifically, the AF unit  46  is constituted as an active AF light receiving system including a floodlighting device. In the AF unit  46 , the arrangement is such that the laser light emitting from the laser light source (LD)  131  is incident into a collimate lens  132  and converted into a parallel light flux, a half of the parallel light flux is shut by a shielding plate  133 , the P polarized component of the laser light flux that was not shut by the shielding plate  133  is reflected towards an imaging lens system  135  by a polarized beam splitter  134 , and the S polarized component thereof is transmitted.  
      The arrangement is such that the P polarized light transmitted through the imaging lens system  135  is converted into an elliptical polarized light by a quarter wave plate  136 , and reflected by a dichroic mirror  137  towards a microplate  120  or a chamber  110 .  
      The elliptical polarized light reflected against the dichroic mirror  137  is irradiated onto the microplate  120  or the chamber  110 , and reflected as elliptical polarized light by the microplate  120  or the chamber  110 . The reflected elliptical polarized light is reflected against the dichroic mirror, incident into the quarter wave plate  136 , converted into an S polarized light, and emitted therefrom. The S polarized light is transmitted through the imaging lens system  135  and the polarized beam splitter  134 , and incident into the imaging lens  138 . The S polarized light incident into the imaging lens  138  is arranged so as to form the imaged thereof on an active two-split detector (PD)  139 .  
      The optical components are set on the same optical axis, and the dichroic mirror  137  is also set on the optical axis of the object lens  48 .  
      The PD  139  is arranged so that two signals PD-A and PD-B are outputted to an active AF signal generation section. 140 . The active AF signal generation section  140  generates an active AF signal showing the defocus amount and the defocus direction, based on the magnitude and the difference of the two signals PD-A and PD-B.  
      An optical element that reflects only the laser light emitting from the LD 131  or the laser light reflected by the microplate  120  or the chamber  110 , is used for the dichroic mirror  137 .  
      As described above, the AF unit  46  may be an optical system that performs active focus, may be an optical system that performs passive autofocus, or may be a system that performs focusing by an other well-known method.  
      As shown in  FIG. 2 , the revolver  47  is arranged on the exciting light emission side of the AF unit  46 , and is arranged with a plurality of object lenses  48  having a plurality of magnifications. For the object lens  48 , there is arranged an object lens control section (focusing drive section)  59  including a highly accurate feed mechanism that can move the object lens  48  in the Z direction (direction for approaching or separating from the relative position with respect to the cells CE).  
      The object lens control section (focusing drive section)  59  drives the revolver  47  based on an instruction from the computer (focusing drive control section, focusing drive control device) PC, so as to select an object lens  48  into which the exciting light is shone, and control the focal position of the object lens  48  by the feed mechanism.  
      As the feed mechanism, for example, a mechanism comprising a cross roller guide, a ball screw, or a stepping motor may be used, or a mechanism using an other actuator such as a piezoelectric element may be used.  
      The object lens  48  has a structure where the inside of the incubator box in the heat insulating box  21  can be observed from the detection section  40  through holes respectively provided in the X axis operation stage  22 X and the Y axis operation stage  22 Y.  
      For the X axis operation stage  22 X and the Y axis operation stage  22 Y, the size of the holes includes some leeway to allow for a range wherein the stage is operated.  
      Therefore, even though the atmosphere in the heat insulating box  21  is kept at a temperature suitable for the cell culture, the atmosphere escapes through the holes to the detection section  40 , so the temperature suitable for the cell culture can not be maintained, causing the likelihood that the cell activity is decreased.  
      Here, there may be provided a restraining device  99  which restrains such an atmosphere at the temperature suitable for the cell culture, from passing through between the heat insulating box  21  and the detection section  40 .  
      The restraining device  99  may be any form as long as the movement of the revolver  47  and the object lenses  48  are not interrupted. For example, it is considered to be in film form having a sheet made from a soft material such as a film or a transparent sheet adhered around the hole provided on the border between the heat insulating box  21  and the detection section  40 , and attached so as to hang down around the revolver.  
      A condenser lens  60  which focuses the detection light onto the detector  49  and the light quantity monitor  50 , is arranged on the detection light emission side of the filter unit  45 .  
      A half mirror  61  which reflects a part of the detection light towards the detector  49  and lets the rest of the detection light pass through towards the light quantity monitor  50 , is arranged on the detection light emission side of the condenser lens  60 .  
      The detector (imaging device, imaging section)  49  is arranged in a position into which the detection light reflected from the half mirror  61  is incident. Moreover, a detector calculation section  62  which calculates the detection signal from the detector  49  and outputs it to the computer PC described later, is connected to the detector  49 .  
      For the detector  49 , a line sensor may be used, an area sensor may be used, or the line sensor and the area sensor may be used together. Moreover, a CCD may be used, a photomultiplier may be used, or a light intensity detecting element such as a photodiode may be used.  
      The light quantity monitor  50  is arranged to measure the detection light transmitted through the half mirror  61 , and output the measured value to the computer PC.  
      As described above, the light quantity of the detection light may be measured using the light quantity monitor  50 , or the light quantity of the detection light may be measured using an illuminometer, a power meter, or the like.  
      The heater  40 H is arranged on for example, four side faces of the detection section  40 , to control the temperature of the inside of the detection section  40  to keep it warm at 30° C. to 37° C., for example. The fan  51  is arranged to convect the air in the detection section  40  so that the temperature in the detection section  40  becomes uniform. Therefore, the temperature in the detection section  40  can be kept at a temperature close to that of the heat insulating box  21 , so that the temperature of the heat insulating box  21  can be stabilized more readily.  
      The cooling fan  52  is driven to decrease the temperature in the detection section  40 , based on the output from the temperature sensor (not shown) that is arranged in the detection section  40 . Therefore, an abnormal increase in the temperature in the detection section  40  due to the heating of a motor or the like can be prevented.  
      The detection section  40  having such a structure allows observation of the cells CE similar to with a microscope, such as phase contrast observation, differential interference observation, fluorescence observation, and the like.  
       FIG. 4  is a perspective view showing the incubator box according to the present embodiment.  
      As shown in  FIG. 4 , the incubator box  100  schematically comprises a box body  101  which stores the microplate  120 , and a cover  102  which forms an enclosed space together with the box body  101 . A magnetic sealing treatment for shutting out the magnetic field from the outside, and a static elimination treatment for eliminating the static electricity generated in the incubator box  100 , are applied to the box body  101  and the cover  102 .  
      The box body  101  is formed from a bottom plate  103  and a side wall  104 . The region corresponding to the measurement area on the bottom plate  103  is made from a material having transmittance such as glass. The other region on the bottom plate  103  and the side wall  104  are preferably made from a metal such as an alumite coated aluminum, or a material having a high shading property such as a stainless steel, like SUS316. From the viewpoint of the heat retaining property, it is more preferable to select a material having low heat conductivity.  
      Moreover, a temperature sensor  106  which measures the temperature of the microplate  120  is arranged on the bottom plate  103 . When the chamber (culturing container)  110  described later is stored into the incubator box  100 , an adaptor  105  (refer to  FIG. 5 ) may be arranged between the bottom plate  103  and the chamber  110  to hold the chamber  110 .  
      Moreover, a water bath  121  enclosing the microplate  120  in a square shape, an internal fan  122  arranged inside of the water bath  121 , a connector  123  which supplies a culture gas, a culture gas concentration sensor  124  which detects the carbon dioxide concentration in the culture gas, and a heater (temperature maintaining section)  100 H which adjusts the temperature in the incubator box  100  to approximately 37° C., are arranged in the box body  101 .  
      The output from the temperature sensor  106  is inputted into the computer PC via an incubator temperature detection section  106 S, and is also inputted into a temperature display section  107  arranged on the wall surface of the detection section  20 . The computer PC controls the heater  100 H and the like via the incubator temperature control section  106 C shown in  FIG. 2 , so as to control to keep the temperature in the incubator box  100  constant.  
      The culture gas concentration sensor  124  outputs the carbon dioxide concentration to the computer PC and to the culture gas concentration display section  124 D.  
      The side wall  121 W of the water bath  121  is formed lower than the height of the side wall  104 . Moreover, the layout for the connector  123  is adjusted so that the supplied culture gas impinges on the side wall  121 W. Sterilized water is stored in the water bath  121  to adjust the humidity in the incubator box  100   a  to approximately 100%.  
      The internal fan  122  is arranged so as to blow along the side wall  104  of the water bath  121 , so that the microplate  120  is not arranged in the flow direction.  
      The culture gas concentration sensor  124  may be arranged on the inner surface of the side wall  121 W of the water bath  121 . Alternatively, the pipeline may be arranged from the incubator box  100  to the outside to draw the culture gas in the incubator box  100  by a suction pump so that the culture gas concentration sensor  124  detects the concentration.  
      The cover  102  comprises a glass plate  117  through which the illuminating light is transmitted, and a support  117 A which supports the glass plate  117 . Anti-reflection films may be formed on the both sides in a region corresponding to the measurement area. By forming the anti-reflection films on the both sides, the reflection by the glass plate  117  during the transmission observation/incident light observation can be avoided.  
      The dimensions of the glass plate  117  may be approximately the same as the dimensions of the bottom plate  103  of the incubator box  100 , or may be the minimum dimensions required for measurement without problems.  
      When such an incubator box  100  is used, since there is no necessity to supply the culture solution from the culturing unit  70 , the operation of various pumps such as a culture solution pump  80  is stopped.  
       FIG. 5  is a perspective view showing another example of an incubator box according to the present embodiment.  FIG. 6  is a cross-sectional view of a chamber according to the present embodiment.  
      As described above, the incubator box  100  may have the microplate  120  (or a well plate) arranged inside, or may have the chamber  110  arranged inside as shown in  FIG. 5 .  
      As shown in  FIG. 6 , the chamber  110  is schematically formed from a bottom glass member  111  for observing by the object lenses  48 , a top glass member  112  for transmitting light from the transmission light source  23 , and a frame member  113  which supports the bottom glass member  111  and the top glass member  112 .  
      A joint  114  formed with a passage for letting the culture solution circulate, is formed on the side facing the frame member  113 . A culture solution circulation pipeline  77  described later is connected to the joint  114 , so that the culture solution circulates between the culturing unit  70  and the chamber  110 . Moreover, the destination of the culture gas from the culture gas mixing bath  91  described later is changed from the incubator box  100  to a culture solution bottle  72 .  
      On the frame member  113 , a pair of grids  115  which make the flow of the culture solution uniform, are arranged approximately perpendicularly to the flow of the culture solution. The commutator  115  is made from a plate member in which small pores are formed in matrix form, and the culture solution dispersingly flows through a plurality of the formed small pores, by which the flow is made uniform. Moreover, a slide glass  116  having cells CE disseminated thereon, is arranged between the two commutators  115 .  
      In this case, the connector  123  which supplies the culture gas is closed off, and the culture gas concentration sensor  124  is not used. Moreover, if the size of the chamber  110  is different from that of the microplate  120 , the chamber  110  may be arranged on the incubator box  100   a  using the adaptor  105 . Furthermore, the sterilized water need not be put into the water bath  121 , and the water bath  121  itself may be taken out from the incubator box  100 . The temperature sensor  106  measures the temperature of the chamber  110 .  
      The connector  123  may be closed off as described above, or the supply of the culture gas to the incubator box  100  may be simply stopped while the culture gas supply pipeline  97  is connected.  
      As shown in  FIG. 1  and  FIG. 2 , the culturing unit  70  schematically comprises a sterile box  71  which stores the culture solution inside, and a mixing section  90  which generates the culture gas.  
      The sterile box  71  comprises; a heater  71 H which keeps the inside of the sterile box  71  warm at a predetermined temperature, a culture solution bottle  72  which stores the culture solution inside, a spare tank  73  which stores the spare culture solution inside, a waste tank  74  into which the used culture solution is put, a UV lamp  25  which sterilizes the inside of the sterile box  71 , an opening/shutting door  75  which is used for putting in and taking out the culture solution bottle  72  or the like from the sterile box  71 , and a main power switch  76  which turns ON/OFF the main power source of the culturing unit  70 .  
      The culture solution bottle  72  is made from a material having excellent thermal conductivity, for example a corrosion-resistant stainless or a glass. A heater (not shown) for the culture solution bottle is arranged at the bottom of the culture solution bottle  72 . The culture solution in the culture solution bottle  72  can be kept at approximately 37° C. by the heater for the culture solution bottle.  
      A culture solution circulation pipeline  77  for letting the culture solution circulate between the incubator box  100  and the culture solution bottle  72 , a supply pipeline  78  which supplies the spare culture solution from the spare tank  73 , and a waste pipeline  79  which discharges the used culture solution from the culture solution bottle  72  to the waste tank  74 , are arranged on the culture solution bottle  72 .  
      A culture solution pump  80  which delivers the culture solution from the culture solution bottle  72  to the incubator box  100  to let the culture solution circulate, is arranged on the culture solution circulation pipeline  77 . Since the culture solution in the chamber  110  can be exchanged for a new solution by the culture solution pump  80 , the period during which the cells CE can be cultured can be extended compared to the case where the culture solution can not be exchanged.  
      A supply pump  81  which sends the culture solution from the spare tank  73  to the culture solution bottle  72  is arranged on the supply pipeline  78 . A waste pump  82  which sends the used culture solution from the culture solution bottle  72  to the waste tank  74 , is arranged on the waste pipeline  79 .  
      For example, a VeriStar pump may be used for the abovementioned culture solution pump  80 , supply pump  81 , and waste pump  82 . A predetermined flow of culture solution can be sent by the VeriStar pump.  
      As described above, the waste tank  74  which stores the used culture solution, may be used. Alternatively, a drainage port which discharges the used culture solution directly to the outside, may be provided without using the waste tank  74 .  
      A culture solution temperature sensor (not shown) which detects the temperature of the inside of the culture solution is arranged on the culture solution bottle  72 , so that the output from the culture solution temperature sensor is inputted into the computer PC via a culture solution temperature detection section  83 . Moreover, the data of the temperature of the culture solution inputted into the computer PC is saved into a memory as text data so as to be used for comparison/verification with the detection result of the cells CE.  
      For the heater  71 H, there is arranged a culture solution temperature control section  84  which controls the temperature of the culture solution through the temperature in the sterile box  71  based on the instructions from the computer PC. The temperature of the culture solution supplied from the culture solution bottle  72  is kept at approximately  370 C by the culture solution temperature control section  84  to avoid a decrease in the activity of cells CE due to the temperature change of the culture solution. Moreover, a temperature display section  85  which displays the culture solution temperature detected by the abovementioned culture solution temperature sensor, is arranged on the wall surface of the culturing unit  70 .  
      A culture solution pump control section  86  which controls the circulation of the culture solution based on the instructions from the computer PC, is arranged on the culture solution pump  80 . Moreover, the supply pump  81  and the waste pump  82  are arranged so that the operation is controlled based on the instructions from the computer PC.  
      The UV lamp  25  is connected to the UV lamp switch  36  arranged on the wall surface of the culturing unit  70 . A timer  37  which controls the operation of the UV lamp  25  timewise is arranged between the UV lamp  25  and the UV lamp switch  36 . Furthermore, there is arranged a sterilization indicator lamp (not shown) which indicates if the UV lamp  25  is turned on.  
      The UV lamp  25  is controlled separately from the main power switch  76 , and can be operated even if the main power source is turned off.  
      As shown in  FIG. 1  and  FIG. 2 , a heater (not shown) which keeps the inside of the mixing section  90  warm at a predetermined temperature, a culture gas mixing bath  91  which controls the carbon dioxide concentration in the culture gas to be supplied to the incubator box  100 , and a CO2 pump  93  which supplies carbon dioxide from a CO2 tank  92  arranged outside of the culturing unit  70  to the culture gas mixing bath  91 , are arranged in the mixing section  90 .  
      On the culture gas mixing bath  91 , a CO2 concentration detection section  94  which detects the carbon dioxide concentration of the inside thereof is arranged, so that the output from the CO2 concentration detection section  94  is inputted to the computer PC. A CO2 concentration control section  95  which controls the amount of carbon dioxide to be supplied to the culture gas mixing bath  91  based on the instruction from the computer PC, is arranged for the CO2 pump  93 . Moreover, a CO2 concentration display section  96  which displays the carbon dioxide concentration in the culture gas mixing bath  91  detected by the CO2 concentration detection section  94 , is arranged on the wall surface of the culturing unit  70 .  
      Furthermore, a culture gas supply pipeline  97  is arranged between the culture gas mixing bath  91  and the culture solution bottle  72 . Therefore, a culture gas can be supplied to the culture solution via the culture gas supply pipeline  97  so as to sufficiently blend the culture gas into the culture solution.  
      Moreover, as necessary, in order to promote the dissolution of carbon dioxide into the culture solution, for example a magnetic stirrer (not shown) may be arranged on the lower side of the culture solution bottle  72  and a stirrer (not shown) which rotates by the rotation of the magnetic field may be arranged in the culture solution bottle  72 . In this manner, by sufficiently blending the carbon dioxide into the culture solution, the pH value of the culture solution can be kept constant.  
      In this manner, a culture solution with 5% concentration of carbon dioxide dissolved is generated in the culture solution bottle  72 , so that the culture solution including culture gas and essential nutrition for growing the cells CE can be supplied to the chamber  110  described later. Moreover, by dissolving the culture gas into the culture solution, the pH and the like of the culture solution can be adjusted.  
      The carbon dioxide concentration inputted from the CO2 concentration detection section  94  to the computer PC is saved into a memory as data, and data processing is made possible in the computer PC.  
      Next is a description of an observation method for the biological sample observation system  10  having the abovementioned structure.  
      First is a description of the selection for the scan method and the detection range in the present embodiment, with reference to  FIG. 7A ,  FIG. 7B ,  FIG. 7C , and  FIG. 7D .  
       FIG. 7A ,  FIG. 7B ,  FIG. 7C , and  FIG. 7D  show selected examples of the scan method and the detection range in the present embodiment.  
      In the example shown in  FIG. 7A , a measuring object range M (the range enclosed by broken lines in the drawing) is selected by specifying a point a on the top left and a point b on the bottom right of the measuring object range M on the displayed image. Specifically, the measuring object range M may be selected by dragging between the points a and b using a device such as a mouse, or may be specified by inputting the coordinate value of the point a and the point b.  
      As shown by the arrows in the drawing, the measurement part for the detector  49  is scanned vertically in the selected measuring object range M. That is, in the drawing, it is scanned in parallel with the X direction when scanned from the left to the right, and it is scanned downwards to the left when scanned from the right to the left. Of these scans, the image of the cells CE is captured when it is scanned from the left to the right.  
       FIG. 7B  is an example for where there are two measuring object ranges M selected by the abovementioned method. Firstly, two measuring object ranges MA and MB are selected by the abovementioned method. In the drawing, the selecting is such that the measuring object range MA and the measuring object range MB are aligned with a predetermined interval in the X direction, and they are wholly overlapped in the Y direction.  
      As shown by the arrows in the drawing, the measurement part for the detector  49  in this example is scanned to measure the measuring object ranges MA and MB side-by-side. That is, in the drawing, it is scanned from the measuring object range MA to the measuring object range MB when scanned from the left to the right, and it is scanned from the measuring object range MB to the measuring object range MA when scanned from the right to the left.  
       FIG. 7C  is an example for where there are two measuring object ranges selected by the abovementioned method and the arrangement of the two measuring object ranges MA and MB is different. Here, in the drawing, the selecting is such that the measuring object range MA and the measuring object range MB are lined up with a predetermined interval in the X direction, and they are partly overlapped in the Y direction.  
      As shown by the arrows in the drawing, regarding the measurement part for the detector  49  in this example, only the part of the measuring object ranges MA and MB which is overlapped in the Y direction is continuously scanned. That is, firstly the part of the measuring object range MA which is not overlapped is scanned. Next, the part of the measuring object ranges MA and the MB which is overlapped in the Y direction is continuously scanned. Then, the part of the measuring object range MB which is not overlapped is scanned.  
       FIG. 7D  is an example for where there are two measuring object ranges M selected by the abovementioned method and the arrangement of the two measuring object ranges MA and MB is similar to that of  FIG. 7B , but the scan method is different.  
      As shown by the arrows in the drawing, regarding the measurement part for the detector  49  in this example, the measuring object ranges MA and MB are separately scanned. That is, firstly the measuring object range MA is wholly scanned, and then the measuring object range MB is wholly scanned.  
      Moreover, among the abovementioned scan methods shown in  FIG. 7A ,  FIG. 7B ,  FIG. 7C , and  FIG. 7D , the scan method by which the total moved distance becomes the shortest is automatically selected by the computer PC, based on a set parameter and measurement mode described later.  
      Next is a description of the procedure taken to measure the cells CE, using respective flowcharts.  
      Firstly, the measurement parameter is set prior to the measurement of the cells CE. Here, the flow of the measurement parameter setting is described with reference to  FIG. 8 .  
       FIG. 8  is a flowchart describing the flow of the measurement parameter setting in the present embodiment.  
      Firstly, the measurement parameter is set (STEP  1 ).  
      Then, default conditions are set (STEP  2 ). The conditions set here are for example a measurement condition and a culture condition such as the CO2 concentration is 5% and the temperature is 37° C. These set conditions can be changed into predetermined conditions by a user.  
      Next, the measuring object is selected (STEP  3 ). The measuring object is a container of the cells CE such as the microplate  120  or the slide glass  116  for example.  
      Next, the measurement mode is selected (STEP  4 ). The measurement mode includes an area imaging mode, a line imaging mode, an automatic mode, and the like. The automatic mode is a mode for automatically selecting a measurement mode in which the measuring time or the scanning time is short, from among the other measurement modes.  
      When capturing an image of the range where the cells are cultured, if the structure is such that the images of a plurality of regions (detection range) can be separately captured by for example, selecting the measuring object ranges M in this manner, then as necessary it is possible to capture only the image of the necessary part.  
      For example, if the setting of the computer PC is changed so as to alternatively scan the whole range, being the scanning object, and a predetermined part of the region, a phenomenon peculiar to the biological sample occurring only for a short period can be captured. As an example, in the case where the whole range being the scanning object, is scanned every 30 minutes, if the predetermined measuring object range M where the noteworthy cells are present is scanned during this time, it becomes possible to capture any peculiar phenomenon that appears for only about 15 minutes, occurring in the noteworthy cells.  
      Moreover, since only the necessary measuring object range M is scanned when needed, the scanning time can be shortened and the light irradiation time to the other cells can be shortened.  
      Next, the measurement magnification is selected (STEP  5 ), and then the detection wavelength is selected (STEP  6 ). In the selection of the measurement magnification, and the selection of the detection wavelength, selection can be made from each of two or more kinds of alternatives.  
      Here, as the selection method of the detection wavelength, the list of fluorescent proteins to be used, such as GFP, HC-Red, and the like is previously stored in the computer PC, and the fluorescent protein is selected from the stored list. Based on the selected fluorescent protein, the computer PC automatically selects the excitation filter  56 , the absorption filter  58 , and the like, that is optimum for the observation. In this manner, a predetermined fluorescence from the cells CE can be detected.  
      During the measurement, the excitation filter  56 , the absorption filter  58 , the object lenses  48 , and the like, are automatically changed in synchronous with the drive of the X axis operation stage  22 X, and the Y axis operation stage  22 Y.  
      Next, the measurement interval is set (STEP  7 ).  
      Then, the preview image is read in (STEP  8 ), and the preview image is displayed on the monitor (STEP  9 ). Here, the preview image is displayed on the monitor under the user&#39;s instruction using a preview button which instructs displaying of the preview image on the monitor. Then, the user can confirm the preview image displayed on the monitor.  
      Next, the measuring range is selected (STEP  10 ). After the measuring range is selected, the preview image may be displayed on the monitor again so as to confirm that the measuring range is the predetermined range.  
      Next, a predetermined measurement interval is selected from a plurality of set measurement intervals (STEP  11 ).  
      Then, if the measurement start switch (not shown) is pressed (STEP  12 ), the measurement of the cells CE is started (STEP  13 ). If the measurement start switch is not pressed, the state remains in standby until the measurement start switch is pressed (STEP  12 ).  
      The setting may be such that, if the measurement start switch is not pressed in STEP  12 , the flow can return to various predetermined STEPs so as to be able to set various setting again.  
      If the measurement parameter setting is completed, then next the cells CE are observed. First is a description of the focus observation area where the focus detection is performed, and a description of the calculation of the movement value of the observation area (observation region) where the observation is performed, but the focus detection is not performed, with reference to  FIG. 9A  to  FIG. 11 .  
       FIG. 9A  shows the observation area on the slide glass  116 ., and  FIG. 9B  shows the area on the slide glass  116  in which the focal position is measured.  
      As shown in  FIG. 9A , the cells CE are disseminated on the slide glass  116 . The biological cell observation system  10  is previously set so as to observe the rectangular regions (observation area M) shown by the dotted lines in the drawing.  
      Alternatively, as shown in  FIG. 9B , the observation areas (focus observation area F) where the focus detection is performed may be selected sparsely. Here, the focus detection is performed in the observation areas M at the four corners and the observation area M in the approximate center of the slide glass  116 , to obtain the movement values. Moreover, the focus detection is performed in the focus observation area F, in the order of top left corner, top right corner, approximate center, bottom left corner, and the bottom right corner.  
       FIG. 10A  is a side view of the slide glass  116 , for explaining the linear interpolation.  FIG. 10B  is a side view of the slide glass  116 , for explaining the curvilinear interpolation.  
      As described above, when the movement values of the five focus observation areas F are obtained, the movement values of the observation areas M where the focus detection is not performed are calculated based on the measured value. The calculation includes a calculation method using linear interpolation, and a calculation method using the curvilinear interpolation.  
      As shown in  FIG. 10A , in the calculation method using linear interpolation, the space between the movement values (shown by O in the drawing) of the focus observation areas F is interpolated by a straight line (shown by a solid line in the drawing), to thereby calculate the movement values of the observation areas M where the focus detection is not performed.  
      As shown in  FIG. 10B , in the calculation method using the curvilinear interpolation, the space between the movement values (shown by O in the drawing) of the focus observation areas F is interpolated by a curved line (shown by a solid line in the drawing), to thereby calculate the movement values of the observation areas M where the focus detection is not performed. The curved line used for the calculation may be a quadric curve or a cubic curve, and it is not specifically limited.  
       FIG. 11  shows the observation area and the focus observation area on the microplate  120 .  
      As shown in  FIG. 11 , if the microplate  120  is used, a well  120 W where the cells CE are stored becomes the observation area M. Moreover, the focus observation areas F are selected by skipping every other area.  
      By selecting the focus observation areas F in this manner, even in the case of a microplate  120  larger than the slide glass  116 , the occurrence of focal displacement can be prevented, and the amount of focal displacement can be decreased.  
      Moreover, compared to a case where focus detection is performed for all the wells  120 W, the time required for the autofocus operation can be shortened if the focus detection is performed on part of the wells  120 W, and the Z coordinates (movement value) of the wells  120 W where the focus detection is not performed are obtained by calculation. In the focus detection method, the time shortening effect may be demonstrated more as the number of the observation areas M (wells  120 W) is increased. For example, since the number of the wells  120 W is generally 384 wells or more, the time shortening effect for the autofocus operation can be more readily demonstrated.  
      In the focus detection method, the focus observation areas F are selected by skipping every other area. However, they may be selected by skipping two areas at a time, or only the wells  120 W at four corners of the microplate  120  may be selected as the focus observation areas F. The selecting can be changed according to the shape of the microplate  120  when the cells CE are observed.  
      Next is a description of the flow of measurement of the cells CE, with reference to  FIG. 12 .  
       FIG. 12  is a flowchart describing the flow of measurement according to the present embodiment.  
      In the measurement described below, the drive is controlled by the computer PC. Firstly, when the observation of the cells CE is started, the X axis operation stage  22 X and the Y axis operation stage  22 Y are moved to the measurement position (STEP  21 ). Here, the previously selected focus observation area F is moved to be positioned above the object lens  48 .  
      Next, the object lens  48  is selected (STEP  22 ). Here, a predetermined object lens  48  is selected by rotating the revolver  47 . Then, the filters  56  and  58  are selected (STEP  23 ). Here, the filters  56  and  58  are selected according to the measurement wavelength used for the observation.  
      Then, the active autofocus is performed (STEP  24 ), and the movement values are obtained (STEP  25 ). Here, the Z coordinate value (movement value) of the object lens  48  which becomes the focal position, is obtained.  
      The obtained movement values are stored in the computer PC (STEP  26 ), and the abovementioned operation is repeated until the movement values of all of the previously selected focus observation areas F are obtained (STEP  27 ).  
      Once obtaining of the movement values for the selected focus observation areas F has been completed, the movement values of the observation areas M between the focus observation areas F are calculated by the computer PC using linear interpolation or curvilinear interpolation (STEP  28 ).  
      Then, the X axis operation stage  22 X and the Y axis operation stage  22 Y are moved to the observation position (STEP  29 ). Here, the observation area M is moved to be positioned above the object lens  48 .  
      Then, based on the movement values obtained in STEP  25  and STEP  28 , the object lens  48  is moved (STEP  30 ), and the image or the fluorescent light quantity in the observation area M is obtained/captured (STEP  31 ).  
      The operation from STEP  29  to STEP  31  is repeated until the observation of the previously selected observation areas M is completed (STEP  32 ). When the observation of all of the observation areas M is completed, the observation of the cells CE is terminated.  
      Once the observation/capturing the image of the cells CE has been terminated, then next the captured image is processed. Here is a description of the processing method of the captured image, with reference to  FIG. 13 .  
       FIG. 13  is a flowchart describing the image processing method.  
      Firstly, the image processing section of the computer PC recognizes the background image from the captured image stored in the memory section (STEP  71 ), and removes the background image (background) from the captured image (STEP  72 ).  
      Next, the maximum luminance range of a highlitable image is read-in (STEP  73 ), and the image is highlighted for example by multiplying by a predetermined coefficient according to the maximum luminance range (STEP  74 ). By these processings, the image is highlightened from the image for which the background has been removed, so that the cells CE can be readily recognized in the granular form one by one.  
      Then, by extracting parts having for example the luminance of a predetermined threshold or more from the highlightened image, the luminance of each cell CE can be recognized in a clear granular form one by one (STEP  75 ).  
      Next, a geometrical feature quantity such as the position of the center of gravity or the area, a chemical feature quantity, an optical feature quantity such as fluorescent luminance of the cell CE, are accurately recognized and extracted in association with the information of the position of the cell CE (STEP  76 ). By extracting the feature quantities, the cells CE can be recognized one by one.  
      After the extraction of the feature quantities of the cells CE, the highlighting operation (STEP  74 ) that has been performed to recognize the cells CE is compensated for (STEP  77 ). By this compensation, the effect of the predetermined coefficient used for highlighting the image is eliminated.  
      Next, the compensated feature quantities are outputted, for example to a file, and stored in the file (STEP  78 ).  
      Therefore, the image processing section of the computer PC can form the image of the distribution of the fluorescent light quantity of the cells CE in the respective positions on the whole surface of the slide glass, the microplate, or the like. Moreover, since the image processing section can trace the cells CE accurately one by one, it is possible to focus on a predetermined number of cells CE and locally measure the fluorescent distribution inside of the cells CE for a long time while culturing them. Furthermore, it is also possible to measure the whole surface of the slide glass, the microplate, or the like at each fixed timing while culturing the cells CE, so as to automatically measure the fluorescent light quantity of the cells CE with respect to the passage of time.  
      As described above, firstly in STEP  21  to STEP  27 , the computer PC performs the focus detection of the object lens  48  using the AF unit  46 . Then, in STEP  28  to STEP  32 , the computer PC continuously observes, using the detector  49 , a plurality of different observation areas M, based on the obtained focusing of the object lens  48 . Part-way through the observation, the focus detection using the AF unit  46  is not performed (i.e., the focus detection using the AF unit  46  does not intervene), and the observation areas M are continuously observed by the detector  49 .  
      Next is a description of the data processing performed after extraction of the data such as the feature quantities of the cells CE from the captured image, with reference to  FIG. 14 .  
       FIG. 14  is a flowchart describing the flow of data processing.  
      Here, the data (feature quantities) of the cells CE stored in the file by the data processing section of the computer PC are processed.  
      Firstly, the data processing section reads-in the raw data (feature quantities) of the cells CE stored in the file (STEP  81 ), and the data is sorted so as to be arranged in time series for each cell (STEP  82 ). After the data is sorted, the data processing section graphs the change with time of the luminance, that is, the expression level, for each cell CE (STEP  83 ).  
      When the graph is completed, the data processing section displays the graph as a preview (STEP  84 ), and the graphed data is outputted to the file (STEP  85 ).  
      By performing the processing, the change with time of a cell for where the cells CE have been cultured for a long time, can be readily observed. Consequently, the change with time of the expression level of the cells CE during the culturing and the like can be accurately and readily measured.  
      Next is a description of the adjustment of the irradiation light quantity performed at the time of measuring the cells CE, with reference to  FIG. 15 .  
       FIG. 15  is a flowchart describing the flow of light quantity adjustment.  
      Firstly, the light quantity of the light irradiated onto the cells CE is measured (STEP  91 ). The irradiation light quantity may be calculated from the output of the light quantity monitor  50 , may be measured by providing an illuminometer, or may be calculated by providing a power meter and calculating from the output of the power meter.  
      If the measured irradiation light quantity is within the allowable range, the flow returns to the measurement of the irradiation light quantity (STEP  91 ), and the measurement is repeated until the irradiation light quantity becomes outside of the allowable range (STEP  92 ).  
      When the irradiation light quantity becomes outside of the allowable range, the ND filter (not shown) included in the light quantity adjustment mechanism  43  is replaced (STEP  93 ), and the irradiation light quantity is adjusted so as to be within the allowable range. Then, the flow returns to the measurement of the irradiation light quantity (STEP  91 ), and the adjustment of the irradiation light quantity is repeated.  
      Next is a description of a control method for supplying/exchanging a culture solution to the chamber  110 , with reference to  FIG. 16 .  
       FIG. 16  is a flowchart describing the supplying/exchanging method of a culture solution.  
      Firstly, the background value of the captured image is analyzed (STEP  101 ). In the background of the captured image, the image of autofluorescent light from the culture solution is captured, and the luminance of the autofluorescent light from the culture solution is analyzed.  
      Here, since the luminance of the autofluorescent light becomes higher as the culture solution gets older, the timing for exchanging the culture solution can be detected by measuring the luminance of the autofluorescent light.  
      If the change with time in the analyzed background value is a predetermined prescribed value or less, the flow returns to the analysis of the background value (STEP  101 ), and the analysis is repeated until the change with time in the background value becomes greater than the predetermined prescribed value (STEP  102 ).  
      When the change with time in the background value becomes greater than the predetermined prescribed value, the waste pump  82  of the culture solution is driven (STEP  103 ), and the supply pump  81  of the culture solution is driven (STEP  104 ).  
      The timing of supplying/exchanging the culture solution may be determined by the autofluorescent light from the culture solution as described above, or may be continual, or the supplying/exchanging may be automatically performed at a time interval previously specified by the user. Alternatively, the time for exchanging the culture solution may be appropriately specified by selecting a cell CE from a previously registered table. Moreover, the amount to be exchanged may be set by the user, may be determined by the autofluorescent light from the culture solution, or all of the culture solution in the chamber  110  may be exchanged. Alternatively, the amount of the culture solution to be exchanged may be appropriately specified by selecting a cell CE from a previously registered table. Moreover, it may be automatically set by converting by weight.  
      By the abovementioned measurement procedure, as shown in  FIG. 17 , a tracked image of the cells showing the change of the cells one by one with the passage of time can be obtained.  
      According to the above structure, since the autofocus operation is performed on the focus observation areas F prior to the observation of the observation areas M, and then the observation areas M are observed based on the movement values obtained from the result, the time required for the observation of the cells CE can be shortened, and the observation can be performed quickly.  
      Moreover, by reducing or controlling the expansion, contraction, and deformation due to the change in the thermal environment of the components related to the observation and focusing, using the heaters  21 H,  40 H, and  100 H, the displacement of the focal position can be prevented or reduced, and the cells CE can be accurately observed.  
      Since the focus observation areas F are part of the observation areas M, the time required for the autofocus operation can be shortened compared to the case where the autofocus operation is performed for all observation areas M.  
      Moreover, since no light is irradiated on the observation areas M other than the focus observation area F, in the autofocus operation, the decrease in the activity of the cells CE can be prevented, in the case where for example, the cells CE are such cells for which activity is decreased by light irradiation.  
      Since the time required for the observation of the cells CE can be shortened, the light irradiation time onto the cells CE can be shortened. For example, in the case where the cells CE are such cells for which activity is decreased by light irradiation, the decrease in the activity of the cells CE can be prevented and an accurate observation result for the cells CE can be obtained.  
      Moreover, since the time required for the observation can be shortened, if a large number of observation areas M are measured such as on the microplate  120 , the time interval between the time when the first observation area M is measured and the time when the last observation area M can be shortened, and accurate observation results which can be compared with a set of information obtained from the observations, can be obtained.  
      Since the object lenses  48  are arranged to be opposed to the cells CE through the microplate  120  or the chamber  110 , the cells CE can be observed without taking the cells CE out from the microplate  120  or the chamber  110 . Therefore, a decrease in the activity of the cells CE can be prevented even with long time observation.  
      Since the movement values of the observation areas M other than the focus observation areas F can be calculated based on the movement values of the focus observation areas F, all observation areas M can be observed based on the movement values. Therefore, compared to the case where the calculation is not performed, the occurrence of the focal displacement in the observation of the observation areas M can be prevented or the amount of the focal displacement can be decreased.  
      Moreover, even if the cells CE are observed using the microplate  120  or the chamber  110  having poor flatness for example, the autofocus operation on all observation areas M is not performed by calculation, and the occurrence of the focal displacement can be prevented or the amount of the focal displacement can be decreased.  
     Second Embodiment  
      Next is a description of a second embodiment of the present invention, with reference to  FIG. 18 .  
      The basic structure of the biological sample observation system of the present embodiment is similar to that of the first embodiment. However, the difference from the first embodiment is the point that a time lapse observation is performed. Therefore, in the present embodiment, the procedure for time lapse observation is described using  FIG. 18 , and the description of the structure of the biological sample observation system and the like is omitted.  
       FIG. 18  is a flowchart showing the flow of the procedure for time lapse observation according to the present embodiment.  
      For the same observation procedures as those of the first embodiment, the same reference symbols are used, and the description thereof is omitted.  
      Firstly, as shown in  FIG. 18 , when the observation of the cells CE is started, the X axis operation stage  22 X and the Y axis operation stage  22 Y are moved to the measurement position (STEP  21 ).  
      Then, the active autofocus is performed (STEP  24 ), and the movement values are obtained (STEP  25 ).  
      The obtained movement values are stored in the computer PC (STEP  26 ), and the abovementioned operation is repeated until the movement values of all of the previously selected focus observation areas F are obtained (STEP  27 ).  
      Then, the X axis operation stage  22 X and the Y axis operation stage  22 Y are moved to the observation position (STEP  29 ).  
      Next, the object lens  48  is selected (STEP  111 ), and the filters  56  and  58  are selected (STEP  112 ).  
      Then, the movement values of the observation areas M between the focus observation areas F are calculated by the computer PC using linear interpolation or curvilinear interpolation (STEP  113 ).  
      Based on the movement values obtained in STEP  25  and STEP  113 , the object lens  48  is moved (STEP  114 ), and the image or the fluorescent light quantity in the observation area M is obtained (STEP  115 ).  
      The operation from STEP  29  to STEP  115  is repeated until the observation of the previously selected observation areas M is completed (STEP  116 ).  
      Then, after the passage of a predetermined time, the flow returns to STEP  21 , in which focal position measurement and the autofocus operation of all focus observation areas F are performed (from STEP  21  to STEP  27 ), and the movement values stored in the computer PC are updated. Then, the image or the fluorescent light quantity of the cells CE is obtained based on the updated movement values (STEP  117 ).  
      The abovementioned procedure is repeated during the time set in the time lapse observation (STEP  118 ), and the observation is continued.  
      As described above, firstly in STEP  21  to STEP  27 , the computer PC performs the focus detection of the object lens  48  using the AF unit  46 . Then, in STEP  29  to STEP  116 , the computer PC continuously observes, using the detector  49 , a plurality of different observation areas M, based on the obtained focusing of the object lens  48 . Part-way through the observation, the focus detection using the AF unit  46  is not performed (i.e., the focus detection using the AF unit  46  does not intervene), and the observation areas M are continuously observed by the detector  49 .  
      Moreover, as shown in STEP  118 , the computer PC can control to repeat the focus detection of the object lens  48  and the continuous observation of the observation areas M which are different from each other. In the continuous observation, the focus detection is not performed part-way through the observation (is clamped part-way through).  
      According to the above structure, the cells CE can be grown for several days to several weeks in the incubator box  100 . Therefore, the time lapse observation can be performed for a long time while culturing the cells CE.  
      When performing the time lapse observation, the time required for observing all observation areas M can be shortened by performing the autofocus operation by the abovementioned procedure.  
      As in the abovementioned procedure, the number of times for the autofocus operation and the number of times for the observation operation of the cells CE may the same and the autofocus operation and the observation operation of the cells CE can be mutually arranged. The number of times for the autofocus operation may be less than the number of times for the observation operation of the cells CE.  
      For example, specifically, the autofocus operation is performed in the morning, noon, evening, and night to update the movement values, and the observation areas M can be observed at a predetermined time interval that was previously set during the autofocus operation.  
      Moreover, since the latest movement values obtained by the autofocus operation and the latest movement values obtained by calculation are stored, the observation areas M can be observed based on the latest movement values.  
      Therefore, even if thermal deformation or the like occurs in the components of the detection unit  20 , leading to the occurrence of focal displacement with respect to the observation areas M, the focal displacement can be reduced compared to the case where the movement values are not updated to the latest values.  
      The technical scope of the present invention is not limited to the above embodiments, and various modifications may be made without departing from the scope of the present invention.  
      For example, in the above embodiments, the description is for where the invention is suitable for a structure where the cells are observed. However, it is not limited to the structure where the cells are observed, but can be suitable for a structure where bacteria, microorganisms, eggs, or various kinds of other biological samples are observed.