Abstract:
The invention provides a microscope examination apparatus including a light source; an illumination optical system configured to guide light from the light source to a specimen; an objective lens configured to collimate return light from the specimen, the objective lens being provided in such a manner as to be displaceable at least in a direction intersecting an optical axis of the objective lens; an image-forming lens configured to image the return light from the specimen, which is collimated by the objective lens; an optical detector configured to detect the return light imaged by the image-forming lens; a microscope main body including the image-forming lens and the optical detector; and an objective-lens driving mechanism configured to drive the objective lens in a direction correcting image blur due to a displacement of the specimen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending U.S. application Ser. No. 11/923,138, filed Oct. 24, 2007, which is a continuation of U.S. application Ser. No. 11/651,552, filed Jan. 10, 2007, now abandoned, and for which priority is claimed under 35 U.S.C. §120. This application is based upon and claims the benefit of priority under 35 U.S.C. §119 from the prior Japanese Patent Application Nos., 2006-004881 filed Jan. 12, 2006 and No. 2006-055060, filed Mar. 1, 2006. The entire contents of all applications are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a microscope examination apparatus, a method of securing a specimen, a securing apparatus, and a stage apparatus. 
         [0004]    2. Description of Related Art 
         [0005]    Recently, in biological research, ion concentration, membrane potential, and so on have been visualized with fluorescence probes using optical microscopes. For example, using individual laboratory animals as specimens, so-called in vivo examination is carried out to observe internal organs and so on while the animal is still alive. 
         [0006]    One known apparatus including an image-acquisition means, is made to track the motion of the examination site (for example, see Japanese Unexamined Patent Application, Publication No. HEI-7-222754 (hereinafter referred to as Document 1)). 
         [0007]    However, with the apparatus disclosed in Document 1, it is necessary to drive the entire microscope, which has a high weight. Therefore, this apparatus has the problem that it cannot be moved at high speed. For example, when observing a heart, because the pulse rate of a rat is about 350 beats per minute and the pulse rate of a mouse is about 620 beats per minute, it is extremely difficult to make the apparatus in Document 1 track these pulse rates. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a microscope examination apparatus, a specimen securing method and securing apparatus, and a stage apparatus which can obtain clear images from a living organism that exhibits dynamic behavior and moves within a particularly short period of time. 
         [0009]    A first aspect of the present invention is a microscope examination apparatus comprising a light source; an illumination optical system configured to guide light from the light source to a specimen; an objective lens configured to collimate return light from the specimen, the objective lens being provided in such a manner as to be displaceable at least in a direction intersecting an optical axis of the objective lens; an image-forming lens configured to image the return light from the specimen, which is collimated by the objective lens; an optical detector configured to detect the return light imaged by the image-forming lens; a microscope main body including the image-forming lens and the optical detector; and an objective-lens driving mechanism configured to drive the objective lens in a direction correcting image blur due to a displacement of the specimen. 
         [0010]    With the microscope examination apparatus described above, the objective-lens driving mechanism is operated to drive the objective lens, in a direction correcting image blur, relative to the specimen in which shifting occurs at the examination site due to dynamic motion of the specimen. By displacing only the objective lens while keeping the microscope main body, which includes the light source, the image-forming lens, and so forth, fixed, it is possible to suppress the motion of the specimen, such as a living organism which exhibits motion with a particularly short time period. Therefore, image blur can be corrected, and it is thus possible to acquire clear images. 
         [0011]    In the microscope examination apparatus described above, the objective lens may be provided so as to be capable of parallel motion in a direction intersecting the optical axis thereof. 
         [0012]    With this configuration, even if the specimen moves in a direction intersecting the optical axis of the objective lens, by operating the objective-lens driving mechanism, it is possible to move the objective lens so that it tracks the displacement of the specimen. As a result, it is possible to correct for shifting of the examination site, and therefore, clear, blur-free images can be acquired. 
         [0013]    In the microscope examination apparatus described above, the objective lens may be provided so as to be capable of rotating about an axis intersecting the optical axis. 
         [0014]    With this configuration, even if the inclination of the observation plane changes due to displacement of the specimen about an axis intersecting the objective lens, by operating the objective-lens driving mechanism, it is possible to move the objective lens so that the optical axis of the objective lens is substantially orthogonal to the observation plane. Therefore, so called blur and so forth can be prevented, and it is thus possible to acquire clear images. 
         [0015]    In the microscope examination apparatus described above, the objective lens may provided so as to be capable of rotating about a principal point of the objective lens. 
         [0016]    With this configuration, it is possible to tilt the optical axis of the objective lens while maintaining a conjugate condition between the observation plane and the detection plane of the optical detector. As a result, it is possible to prevent blur. Furthermore, the rotation of the objective lens about the principal point has no effect on the image position. Therefore, it is possible to prevent image blur. 
         [0017]    In the microscope examination apparatus described above, the objective lens may be provided so as to be capable of rotating about an object point of the objective lens. 
         [0018]    With this configuration, it is possible to tilt the optical axis of the objective lens while maintaining a conjugate condition between the observation plane and the detection plane of the optical detector. As a result, it is possible to prevent blur. Furthermore, by rotating the objective lens about the object point, it is possible to always observe the center of the specimen at an on-axis region of the objective lens, which allows observation without degrading the optical characteristics of the objective lens. Therefore, it is possible to prevent the aberrations due to rotation of the objective lens from worsening. 
         [0019]    The microscope examination apparatus described above preferably further comprises a correction optical system for correcting shifting of the optical axis by rotating the objective lens. When the objective lens is rotated about the object point thereof, it is possible to always observe the center of the specimen at the on-axis region of the objective lens. Because image blur occurs at the detection plane of the optical detector, it is possible to acquire blur-free images by correcting the image blur by operating the correction optical system. 
         [0020]    In the microscope examination apparatus described above, the light source and the illumination optical system may be provided within the main body. 
         [0021]    In the microscope examination apparatus described above, the specimen may include a small laboratory animal. 
         [0022]    A second aspect of the present invention is a specimen securing method for securing a specimen, which is mounted on a stage, to the stage by pressing the specimen to the stage with a tensile force of a sheet member covering the specimen. 
         [0023]    With this specimen securing method, the specimen mounted on the stage is secured by being pressed to the stage by the tensile force of the sheet member. Because the sheet member has a large area, a large pressing force is not applied locally to the specimen. Therefore, the effect on the specimen can be reduced and the viability of the specimen can thus be maintained. By securing the specimen using the sheet member with a large area, it is possible to suppress the periodic motion of the entire specimen. As a result, blurring of the observed image due to such motion can be prevented, and it is thus possible to acquire clear images. 
         [0024]    In the specimen securing method described above, the sheet member may be a strip partially covering the specimen. 
         [0025]    With this configuration, because the motion is suppressed by the strip-shaped sheet member, it is possible to partially suppress the effective site. 
         [0026]    In the aspect of the invention described above, the sheet member may entirely cover the specimen. 
         [0027]    In the specimen securing method described above, the sheet member may be transparent. 
         [0028]    With this configuration it is possible to observe the examination site of the specimen via the sheet member which secures the specimen. As a results, it is possible to observe the examination site while directly securing the specimen with the sheet member, and blurring of the observed images can thus be suppressed effectively. 
         [0029]    In the specimen securing method described above, a through-hole may be provided in the sheet member covering the specimen at a position corresponding to an examination site of the specimen. 
         [0030]    With this configuration, it is possible to directly observe the specimen by exposing the examination site through the through-hole in the sheet member which secures the specimen. Therefore, the sheet member is not restricted to a transparent material, and it is possible to use any suitable material. 
         [0031]    A third aspect of the present invention is a specimen securing apparatus comprising a frame having a size that surrounds a specimen mounted on a stage; a sheet member stretched at an inner side of the frame; and a pressing portion configured to press the frame towards the stage. 
         [0032]    With this specimen securing apparatus, the sheet member which is stretched inside the frame is pressed from above onto the specimen mounted on the stage, and the frame is pressed towards the stage by the pressing portion, while the specimen is sandwiched between the stage and the sheet member. By doing so, the tensile force of the sheet member is increased, and it is thus possible to secure the specimen. 
         [0033]    In the specimen securing apparatus described above, the frame may include a pair of frame plates sandwiching the sheet member, and a joining portion configured to join the frame plates in a detachable manner. 
         [0034]    With this configuration, by sandwiching the sheet member between the pair of frame-shaped plates and joining the two frame-shaped plates using the joining portion, it is possible to integrate the frame and the sheet member. Also, by unjoining the frame-shaped plates joined by the joining portion, it is possible to separate the sheet member and the frame. Therefore, it is possible to easily replace the sheet member. 
         [0035]    In the specimen securing apparatus described above, the joining portion is constituted by forming one of the frame plates of a magnet and forming the other one of a magnet or a magnetic material. 
         [0036]    With this configuration, it is possible to easily integrate the sheet member and the frame by joining the pair of frame-shaped plates using the magnetic force of attraction of a magnet. Also, by applying the force that surpasses the magnetic force of attraction of the magnet to separate the frame-shaped plates, it is possible to easily separate the sheet member from the frame. 
         [0037]    In the specimen securing apparatus described above, the sheet member may be transparent. 
         [0038]    In the specimen securing apparatus described above, a through-hole may be provided in the sheet member covering the specimen, at a position corresponding to an examination site of the specimen. 
         [0039]    A fourth aspect of the present invention is a stage apparatus comprising a stage configured to mount a specimen, and any one of the specimen securing apparatuses described above. 
         [0040]    With this stage apparatus, by operating the specimen securing apparatus to press the frame towards the stage, the specimen is sandwiched between the stage and the sheet member supported in the frame. It is thus possible to effectively and easily secure the specimen using the tensile force of the sheet member. 
         [0041]    According to the present invention, an advantage is afforded in that it is possible to acquire clear images from a living organism that exhibits dynamic motion, particularly movement within a short period of time. In addition, the present invention provides an advantage in that it is possible to continuously or consecutively acquire images without going out of the field of view of a living organism that moves with a large amplitude. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0042]      FIG. 1  is a diagram showing the overall configuration of a microscope examination apparatus according to a first embodiment of the present invention. 
           [0043]      FIGS. 2 and 3  are diagrams showing examples of a driving mechanism for driving an objective lens in an objective-lens driving mechanism of the microscope examination apparatus in  FIG. 1 . 
           [0044]      FIG. 4  is a diagram showing another example of the driving mechanism in  FIGS. 2 and 3 . 
           [0045]      FIG. 5  is a perspective view showing the relationship between the objective lens and coordinate axes in the description of the microscope examination apparatus in  FIG. 1 . 
           [0046]      FIGS. 6 to 8  are diagrams showing the relationship between operating direction of the specimen and the operating mode of the objective lens in the microscope examination apparatus in  FIG. 1 . 
           [0047]      FIGS. 9 and 10  are diagrams showing the light path of the objective lens which is rotated about a principal point in the microscope examination apparatus in  FIG. 1 . 
           [0048]      FIG. 11  is a perspective view showing a first modification of the objective-lens driving mechanism in the microscope examination apparatus in  FIG. 1 . 
           [0049]      FIG. 12  is a longitudinal sectional view showing a second modification of the objective-lens driving mechanism in the microscope examination apparatus in  FIG. 1 . 
           [0050]      FIG. 13  is a perspective view showing a third modification of the objective-lens driving mechanism in the microscope examination apparatus in  FIG. 1 . 
           [0051]      FIG. 14  is a longitudinal sectional view showing a fourth modification of the objective-lens driving mechanism in the microscope examination apparatus in  FIG. 1 . 
           [0052]      FIG. 15  is a perspective view for explaining an electromagnetic linear motor constituting the objective-lens driving mechanism in  FIG. 14 . 
           [0053]      FIG. 16  shows the relationship between the operating direction of the electromagnetic linear motor in  FIG. 15  and the conducting state of each coil. 
           [0054]      FIG. 17  is a perspective view showing a fifth modification of the objective-lens driving mechanism in the microscope examination apparatus in  FIG. 1 . 
           [0055]      FIG. 18  is a longitudinal sectional view showing a sixth embodiment of the objective-lens driving mechanism in the microscope examination apparatus in  FIG. 1 . 
           [0056]      FIGS. 19 and 20  are diagrams showing the light path of the objective lens which rotated about an object point in a microscope examination apparatus according to a second embodiment of the present invention. 
           [0057]      FIGS. 21 and 22  are diagrams for explaining correction of image blurring in the microscope examination apparatus in  FIGS. 19 and 20 . 
           [0058]      FIG. 23  is a perspective view for explaining an image-blur correction mechanism for mechanically correcting image blurring in the microscope examination apparatus in  FIGS. 19 and 20 . 
           [0059]      FIG. 24  is a perspective view for explaining in detail part of the image-blur correction mechanism in  FIG. 23 . 
           [0060]      FIG. 25  is a perspective view for explaining a specimen securing method according to an embodiment of the present invention. 
           [0061]      FIG. 26  is a perspective view showing a modification of the specimen securing method in  FIG. 25 . 
           [0062]      FIG. 27  is a perspective view showing another modification of the specimen securing method in  FIG. 25 . 
           [0063]      FIG. 28  is a perspective view showing yet another modification of the specimen securing method in  FIG. 25 . 
           [0064]      FIG. 29  is a perspective view showing a specimen securing apparatus according to an embodiment of the present invention. 
           [0065]      FIG. 30  is a perspective view showing a specimen secured on a stage using the specimen securing apparatus in  FIG. 29 . 
           [0066]      FIG. 31  is an exploded perspective view of the specimen securing apparatus in  FIG. 29 . 
           [0067]      FIG. 32  is a modification of the specimen securing apparatus in  FIG. 30 . 
           [0068]      FIG. 33  is a longitudinal sectional view showing a stage apparatus according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0069]    A microscope examination apparatus  1  according to a first embodiment of the present invention will be described below with reference to  FIGS. 1 to 10 . 
         [0070]    As shown in  FIG. 1 , the microscope examination apparatus  1  according to this embodiment includes a stage  2  for mounting a specimen S; an excitation light source  3  for emitting excitation light E; an illumination lens (illumination optical system)  4  for guiding the excitation light E from the excitation light source  3 ; an objective lens  5  for guiding the excitation light E guided by the illumination lens  4  to the specimen S, as well as for collimating fluorescence F generated in the specimen S; a dichroic mirror  6  for splitting off from the excitation light E the fluorescence F collimated by the objective lens  5 ; a beamsplitter  7  for further dividing the split-off fluorescence F; and two image-acquisition devices (optical detectors)  8  and  9 , such as CCDs, for detecting the split-off fluorescence F. Reference numerals  20  in this figure are image-forming lenses. 
         [0071]    The excitation light source  3 , the illumination lens  4 , the dichroic mirror  6 , the beamsplitter  7 , and the two image-acquisition devices  8  and  9  are provided in a microscope main body  10 . On the other hand, the objective lens  5  is separate from the microscope main body  10 , and is supported by an objective-lens driving mechanism  11 . 
         [0072]    The objective-lens driving mechanism  11  includes an arm  12  which disposes the objective lens  5  between the stage  2  and the microscope main body  10 ; a first driving mechanism  13  for moving the objective lens  5 , which is held by the arm  12 , in the vertical direction; second and third driving mechanisms  14  and  15  for moving the objective lens  5  in two horizontal directions; and fourth and fifth driving mechanisms  16  and  17  for rotating the objective lens  5  about axes parallel to two directions orthogonal to the optical axis of the objective lens  5 . The first to third driving mechanisms  13  to  15  include, for example, motors  13   a  to  15   a  and linear driving mechanisms, for example, ball screws (not shown in the drawing), connected to the motors  13   a  to  15   a . The fourth and fifth driving mechanisms  16  and  17  include, for example, motors  16   a  and  17   a  and speed-reduction mechanisms  16   b  and  17   b  connected to the motors  16   a  and  17   a . The speed-reduction mechanisms  16   b  and  17   b  include, for example, lead screws  16   c  and  17   c  and nuts  16   d  and  17   d  provided at a fixed side and claws  16   e  and  16   d , provided at a moving side, for transmitting the motion of the nuts  16   d  and  17   d , as shown in  FIGS. 2 and 3 , or worm gears  16   f  and  17   f , as shown in  FIG. 4 . 
         [0073]    The amount of displacement of the specimen S and the direction thereof are calculated in a control apparatus  18  by processing images acquired by the image-acquisition device  9 . In addition, the control apparatus  18  outputs driving command to each of the driving mechanism  13  to  17  of the objective-lens driving mechanism  11  to drive the objective lens  5  in a direction which corrects shifting of the optical axis of the objective lens  5  due to displacement of the specimen S, and the control apparatus  18  is connected to the image-acquisition device  9 . 
         [0074]    As shown in  FIG. 5 , in the microscope examination apparatus  1  according to this embodiment, having such a configuration, by operating the objective-lens driving mechanism  11 , the objective lens  5  can be moved in a Z-axis direction parallel to the optical axis and in X-axis and Y-axis directions orthogonal to the optical axis, as well in directions A and B about the X-axis and Y-axis, respectively. 
         [0075]    More specifically, as shown in  FIGS. 6 and 7 , it is possible to translate the objective lens  5  in the X-axis, Y-axis, and Z-axis directions while maintaining its orientation. Also, as shown in  FIG. 8 , it is possible to rotate the objective lens  5 , about a principal point H, in the A and B directions about the X-axis and Y-axis. 
         [0076]    In the following, when rotating the objective lens  5  about the principal point H at the object side thereof, a blur-correction effect and an image-blur prevention effect will be described using  FIGS. 9 ,  10 , and  19 . 
         [0077]    In  FIGS. 9 ,  10 , and  19 , an optical axis AX 0  is the optical axis of the image-forming lenses  20 ; a point O 0  is defined as the intersection of the optical axis AX 0  and the specimen S; and point I 0  is the intersection of the optical axis AX 0  and the image-acquisition devices  8  and  9 . An optical axis AX 1  is the optical axis of the objective lens  5 , the point O 1  is the intersection of the optical axis AX 1  and the specimen S, and the point F OB  is an object-side focal point of the objective lens  5 . The point S c  is a point on the specimen A defined as the center of the field of view. 
         [0078]    First, as shown in  FIG. 19 , we consider a case in which the specimen S is orientated orthogonal to the optical axis AX 0 , and the point Sc is at a location overlapping the optical axis AX 0 . At this time, the orientation and position of the objective lens  5  are controlled so that the optical axis AX 1  thereof is aligned with the optical axis AX 0  and the object-side focal point F OB  thereof overlaps the specimen S. As a result, the object-side focal plane of the objective lens  5  is aligned with the specimen S. Also, the point O 1 , the point O 0 , and the point Sc overlap with each other and are in conjugate relationship with a point I 0 . In other words, in-focus images of the specimen S are projected over the entire plane at the image-acquisition devices  8  and  9 , and an image of the point Sc is projected at the central point I 0  of the image-acquisition devices  8  and  9 . 
         [0079]    Next, as shown in  FIG. 9 , a case in which the specimen S is tilted at a predetermined angle about the point Sc is considered. At this time, the objective lens  5  is rotated about the object-side principal point H thereof, and the orientation is controlled so that the optical axis AX 1  is orthogonal to the specimen S. As a result of this orientation control, when the specimen S deviates from the object-side focal point F OB  of the objective lens  5 , the position of the objective lens  5  in the direction of optical axis AX 0 , that is, the Z direction, is controlled so that the focal point F OB  and the specimen S are re-aligned. As a result, the object-side focal plane of the objective lens  5  is aligned with the specimen S. At the same time, point O 0  and point Sc are aligned with each other, and a conjugate relationship with point I 0  is established. In other words, an in-focus image (that is, a blur-free image) of the specimen S is projected over the entire plane of the image-acquisition devices  8  and  9 , and an image of the point S 0  is projected at the central point I 0  of the image-acquisition devices  8  and  9  (that is, blurring is prevented). 
         [0080]    Next, when correcting the blurring by rotating the objective lens  5  about the object-side principal point H thereof, the prevention of image blur as shown in  FIG. 9  will be described in detail by showing representative rays. 
         [0081]      FIG. 10  shows, in particular, the light path of a ray R coming from the point Sc and passing through the object-side principal point H and an image-side principal point H′ of the objective lens  5 , in the same observation state as in  FIG. 9 . This ray R is formed of a ray Ra from the point Sc to the object-side principal point H, a ray Rb from the object-side principal point H to the image-side principal point H′, a ray Rc from the image-side principal point H′ to the image-forming lenses  20 , and a ray Rd from the image-forming lenses  20  to the image-acquisition devices  8  and  9 . 
         [0082]    The ray R emitted from the point Sc propagates as ray Ra aligned with the optical axis AX 0  and is incident on the object-side principal point H. Then, it propagates as ray Rb aligned with the optical axis AX 1  and is incident on the image-side principal point H′. Then, it propagates as ray Rc parallel to the optical axis AX 0  and is incident on the image-forming lenses  20 . Then, as ray Rd, it is deflected by the image-forming lenses  20  and is incident on the focal point of the image-forming lenses  20 , that is, at the center I 0  of the image-acquisition devices  8  and  9 . 
         [0083]    By rotating the objective lens  5  about the object-side principal point H thereof to correct the blurring, the ray emitted from the point Sc is always incident on the point I 0 , that is, at the center of the image-acquisition devices  8  and  9 . In other words, this means that no image blurring occurs. 
         [0084]    The operation of the microscope examination apparatus  1  according to this embodiment, having such a configuration, will be described below. 
         [0085]    With the microscope examination apparatus  1  according to this embodiment, the excitation light E emitted from the excitation light source  3  is emitted from the microscope main body  10  via the illumination lens  4  and the dichroic mirror  6  and is incident on the objective lens  5 . The excitation light E incident on the objective lens  5  passes through the objective lens  5  and irradiates the specimen S, which is mounted on the stage  2 . When the excitation light E irradiates the specimen S, a fluorescent substance inside the specimen S is excited and emits fluorescence F. 
         [0086]    The fluorescence F generated in the specimen S is collimated by the objective lens  5  to form a substantially collimated beam, which enters the microscope main body  10 . The fluorescence F entering the microscope main body  10  is split off from the excitation light E by the dichroic mirror  6 , is then divided by the beam splitter  7 , and is detected by the individual image-acquisition devices  8  and  9 . 
         [0087]    Image information acquired by imaging with the image-acquisition device  9  is sent to the control apparatus  18 , and by subjecting it to image processing in the control apparatus  18 , command signals to be sent to each of the driving mechanism  13  to  17  of the objective-lens driving mechanism  11  are calculated, and each of the driving mechanisms  13  to  17  is driven on the basis of these command signals. 
         [0088]    When the specimen S is displaced in the horizontal direction, the displacement direction and displacement amount are detected using image processing, and command signals are sent from the control apparatus  18  to the second and third driving mechanisms  14  and  15  to translate the objective lens  5  horizontally in the same direction by the same displacement amount. Accordingly, because the objective lens  5  is translated so as to track the displacement of the specimen S, it is possible to acquire an image with a low level of blur. 
         [0089]    When the specimen S is displaced in the optical-axis direction, the amount of displacement thereof is detected using image processing, and a command signal is sent from the control apparatus  18  to the first driving mechanism  13  to translate the objective lens  5  in the optical-axis direction by the same displacement amount. Accordingly, because the objective lens  5  is translated in the optical-axis direction so as to track the displacement of the specimen S, it is possible to acquire a clear, in-focus image. 
         [0090]    When the specimen S is tilted about a horizontal optical axis, the direction and rotation angle thereof are detected using image processing, and command signals are sent from the control apparatus  18  to the fourth and fifth driving mechanisms  16  and  17  to rotate the objective lens  5  in the same direction by the same rotation angle. 
         [0091]    Accordingly, because the objective lens  5  is rotated so as to track the tilting of the specimen S, it is possible to acquire a clear, blur-free image. 
         [0092]    In this case, with the microscope examination apparatus  1  according to this embodiment, because the objective lens  5  is rotated about the principal point H thereof, no blurring of the image acquired by the image-acquisition devices  8  and  9  occurs, and therefore it is not necessary to provide a separate apparatus for correcting image blur. Therefore, an advantage is provided in that it is possible to provide a simple apparatus configuration. 
         [0093]    Thus, with the microscope examination apparatus  1  according to this embodiment, by fixing the microscope main body  10 , which is relatively heavy, and translating and rotating the objective lens  5 , which is relatively light, it is possible to compensate for blurring, defocus, and moving out of the field of view due to displacement of the specimen S, which allows a clear, low-blur image to be acquired. Also, it is possible to perform continuous observation without interrupting image acquisition due to moving out of the field of view. 
         [0094]    In the microscope examination apparatus  1  according to this embodiment, the lead screws  16   c  and  17   c  or the worm gears  16   f  and  17   f  are illustrated as examples of the mechanism for rotating the objective lens  5  of the objective-lens driving mechanism  11 . Instead of these, however, as shown in  FIG. 11 , it is possible to use a multiple-degree-of-freedom spherical-surface ultrasonic motor  23  in which a plurality of ultrasonic motors  22  are arranged in contact on the circumference of a sphere  21  to which the arm  12  is attached. 
         [0095]    When using the multiple-degree-of-freedom spherical-surface ultrasonic motor  23 , as shown in  FIG. 12 , the sphere  21  may be made hollow and observation may be carried with the objective lens  5  disposed in the interior and the specimen S accommodated inside the sphere  21 . 
         [0096]    As shown in  FIG. 13 , it is also possible to employ two groups of platform-shaped link mechanisms  24  and  25  for rotating the objective lens  5 . By rotating the platform-shaped link mechanisms  24  and  25  using actuators (not shown in the drawing) provided on the platform-shaped link mechanisms  24  and  25 , it is possible to rotate the objective lens  5 , which is secured to the end of the platform-shaped link mechanisms  24  and  25 . The objective lens  5  is rotated about the X-axis, that is, in direction A, by the platform-shaped link mechanism  25  and is rotated about the Y-axis, that is, in direction B, by the platform-shaped link mechanism  24 . 
         [0097]    It is possible to use an electromagnetic linear motor  31  as the objective-lens driving mechanism  11 . As shown in  FIG. 14 , a bobbin member  26 , to which two pointed portions  26   a  and  26   b  are connected by means of a cylindrical portion  26   c , is supported by resilient members  28 , such as coil spring, so as to be capable of moving inside a case  27 . In addition, as shown in  FIG. 15 , two inner and outer ring-shaped coils  29   a  and  29   b  are respectively disposed on each of the pointed portion  26   a  and  26   b , and magnets  30   a  and  30   b  which sandwich each of the coils  29   a  and  29   b  are disposed at positions such that they are oriented in the radial direction of the pointed portions  26   a  and  26   b . Translation in the optical-axis direction of the objective lens  5  is achieved by means of a Z-axis stage  13  which is provided separately from the electromagnetic linear motor  31 . 
         [0098]    The conducting states of the coil  29   a  (inner side) and the coil  29   b  (outer side) when translating the objective lens  5  in the X-axis and Y-axis directions and when rotating it in the A and B directions are shown in  FIG. 16 . For example, in order to translate the objective lens  5  in the X-axis direction, by flowing electrical currents in the same directions in the outer coils  29   b  on the upper and lower pointed portions  26   a  and  26   b , using the Lorentz force between the magnets  30   b  and the coils  29   b , a force is exerted at the same time and in the same direction in the X-axis direction on the upper and lower pointed portions  26   a  and  26   b  of the bobbin member  26 , which enables the objective lens  5  to be translated. By switching the directions of the electrical currents flowing in the coils  29   b , it is possible to switch the direction in which the objective lens  5  is translated in the X-axis direction. Similarly, for translation in the Y-axis direction, the inner coils  29   a  on the upper and lower pointed portions  26   a  and  26   b  conduct. 
         [0099]    To rotate the objective lens  5  in the A direction about the X-axis, by flowing electrical currents in opposite directions in the inner coils  29   a  on the upper and lower pointed portions  26   a  and  26   b , respectively, a force is exerted at the same time and in the opposite direction to the Y-axis direction on the upper and lower pointed portions  26   a  and  26   b  of the bobbin member  26 , generating a rotational force, which enables the objective lens  5  to be rotated in the A direction. Similarly, to rotate it in the B direction about the Y-axis, electrical currents flow in opposite directions in the outer coils  29   b  on the upper and lower pointed portions  26   a  and  26   b . Accordingly, it is possible to achieve translation of the objective lens  5  along the X-axis and the Y-axis and to achieve rotation thereof in the A and B directions using a single electromagnetic linear motor  31 , which affords an advantage in that it is possible to construct the apparatus with a compact configuration. 
         [0100]    In this embodiment, the objective lens  5  is separate from the microscope main body  10  and is independently controlled. However, as shown in  FIG. 17 , it may be attached to the microscope main body  10  using a parallel-link stage  32 . 
         [0101]    The parallel-link stage  32 , which combines six linear actuators  33 , can translate the objective lens  5  in the X-axis, Y-axis, and Z-axis directions and can rotate it in the A and B directions about the X-axis and Y-axis. The linear actuators  33  may use piezoelectric devices or voice coil motors. It is possible to employ linear actuators  33  of the type in which rapid expansion and contraction of piezoelectric devices is repeated (for example, see Japanese Unexamined Patent Application, Publication No. HEI 11-90867). 
         [0102]    Using this type of actuator in which rapid expansion and contraction of piezoelectric devices is repeated, as shown in  FIG. 18 , the objective lens  5  may be rotated along a guide rail  34  having a spherical surface. Reference numerals  35  in the drawing are piezoelectric devices, reference numerals  36  are spindles serving as inertial elements, and reference numerals  37  are sliders which are in frictional contact with the guide rail  34 . 
         [0103]    In this embodiment, as the method of detecting the amount of displacement in the optical-axis direction, the tilt direction, and the rotation angle, a method based on image processing has been described. Instead of this however, it is possible to use so-called pupil division in which a plurality of optical detectors are disposed in a plane conjugate with respect to the pupil of the image-forming optical system, and combined focus information is obtained from output signals thereof. It is also possible to dispose position detectors based on optical triangulation and to obtain surface positional information of the specimen therefrom. 
         [0104]    Next, regarding a microscope examination apparatus  40  according to a second embodiment of the present invention, a blur-correction effect thereof and a method of correcting image blur will be described below with reference to  FIGS. 19 to 22 . 
         [0105]    In the description of this embodiment,  FIG. 19  is also used in the description of the microscope examination apparatus  1  according to the first embodiment described above. Also, parts having the same configuration as those in the first embodiment described above are assigned the same reference numerals, and a description thereof is thus omitted. 
         [0106]    The microscope examination apparatus  40  according to this embodiment differs from the microscope examination apparatus  1  according to the first embodiment in that the objective lens  5  is rotated about an object-side focal point F OB  thereof. 
         [0107]    First, when the specimen S and the objective lens  5  are in the state shown in  FIG. 19 , an in-focus image of the specimen is projected over the entire plane of the image-acquisition devices  8  and  9 , and an image of the point Sc is projected at central points I 0  of the image-acquisition devices  8  and  9 . 
         [0108]    Next, as shown in  FIG. 20 , a case in which the specimen S is tilted at a certain angle about the point Sc is considered. At this time, the objective lens  5  is rotated about the object-side focal point F OB  thereof, and the orientation is controlled so that the optical axis AX 1  is orthogonal to the specimen S. As a result, the object-side focal plane of the objective lens  5  is coincident with the specimen S. In other words, in-focus images of the specimen S (that is, images having no blur) are projected over the entire plane of the image-acquisition devices  8  and  9 . 
         [0109]    In this embodiment, however, when the objective lens  5  is rotated, so-called image blur (Y ERR  in  FIG. 20 ) occurs; that is, the image of the point Sc defined as the center of the field of view is shifted from the central position I 0  in the image-acquisition plane. Therefore, an image-blur correction mechanism  41  for correcting this is provided. As shown in  FIGS. 21 and 22 , the image-blur correction mechanism  41  may include an image-forming lens  42  and a pupil-relay lens  43  disposed between the objective lens  5  and the image-acquisition devices  8  and  9 , and a correction mirror  44  which can be rotated may be disposed in the vicinity of the back focal point of the pupil-relay lens  43 . Using the correction mirror  44  which can rotate about an axis orthogonal to the optical axis, it is possible to correct the image blur by rotating it by the following angle A CM  in a direction opposite to the tilt direction of the objective lens. 
         [0000]        A   CM   =f   TL /2 f   PL   ×A   SP   (1) 
         [0110]    Here, f TL  is the focal length of the image-forming lens  42 , f PL  is the focal length of the pupil-relay lens  43 , and A SP  is the rotation angle of the objective lens  5 . 
         [0111]    The correction mirror  44  may be driven using an actuator (not shown in the drawing), by operating the control apparatus  18 . In addition, as shown in  FIGS. 23 and 24 , it may be coupled to the rotation of the objective lens  5  using a mechanical transmission mechanism  45 . It may have one rotation axis to enable rotation in one direction, or it may have two rotation axes to enable free rotation in three dimensions. 
         [0112]    Describing  FIGS. 23 and 24  in more detail, one end of links  47  and  48  having columnar end portions  47   a  and  48   a  are disposed so as to be inserted inside elongated holes  46   a  and  46   b  provided in the arm  12  which holds the objective lens  5 . Rotation shafts  51   a  and  51   b  of bevel gears  50   a  and  50   b  are connected to the other end of each link  47  and  48  via respective universal joints  49 . Reference numerals  52   a  and  52   b  in the figure are elongated holes for restricting the movement direction of the links  47  and  48 . 
         [0113]    With this configuration, when the arm  12  is translated horizontally (in the X and Y directions), displacement of the columnar end portions  47   a  and  48   a  inside the elongated holes  46   a  and  46   b  is allowed. When the arm  12  is translated vertically (in the Z direction), the universal joints  49  bend while allowing displacement of the columnar end portions  47   a  and  48   a  inside the elongated holes  46   a  and  46   b . Accordingly, no rotary force is transmitted to the rotation shafts of the bevel gears  50   a  and  50   b  due to the translation in the X, Y, and Z directions. 
         [0114]    Correction mirrors  44   a  and  44   b  are respectively connected to other bevel gears  53   a  and  53   b , which mesh with each of the bevel gears  50   a  and  50   b , via shafts  54   a  and  54   b  and gear trains  55   a  and  55   b.    
         [0115]    Accordingly, when the arm  12  rotates about the X-axis, because the link  47 , which extends in the X-axis direction, is made to rotate about that axis, the rotary force thereof is transmitted to the rotation shaft  51   a  of the bevel gear  50   a , and the first correction mirror  44   a  is rotated via the bevel gear  53   a , the shaft  54   a , and the gear train  55   a . At this time, no rotary force is produced on the other link  48 , and the second correction mirror  44   b  is thus kept stationary. 
         [0116]    Conversely, when the arm  12  rotates about the Y-axis, because the link  48 , which extends in the Y-axis direction, is made to rotate about that axis, the rotary force thereof is transmitted to the rotation shaft  51   b  of the bevel gear  50   b , and the second correction mirror  44   b  is made to rotate via the bevel gear  53   b , the shaft  54   b , and the gear train  55   b . At this time, no rotary force is produced on the other link  47 , and the first correction mirror  44   a  is thus kept stationary. 
         [0117]    The relationship between the tilt angle of the arm  12  and the rotation angles of each of the correction mirrors  44   a  and  44   b  is set as defined by expression (1) above, by adjusting the number of teeth on the bevel gears  50   a ,  50   b ,  53   a , and  53   b  and the gear trains  55   a  and  55   b.    
         [0118]    By respectively rotating the two correction mirrors  44   a  and  44   b , it is possible to correct image blur generated according to the rotation of the objective lens  5  about the X-axis and the Y-axis. 
         [0119]    Thus, with the microscope examination apparatus  40  according to this embodiment, because the objective lens  5  is made to rotate about the object-side focal point F OB , although image-blur correction mechanisms  41  and  45  for correcting the image blur generated in response thereto are necessary, it is possible to observe the specimen S with the object-side focal point F OB  of the objective lens  5 , in other words, the central position of the field of view at the object side of the objective lens  5 , always aligned with point Sc (that is, a point on the specimen S defined as the center of the field of view). Therefore, without deteriorating the optical characteristics of the objective lens  5 , it is possible to prevent aberrations from worsening even though the objective lens  5  is rotated, which affords an advantage in that clear images can be acquired. 
         [0120]    It has been described above that the microscope examination apparatus  40  according to this embodiment has image-acquisition devices  8  and  9  such as CCDs. Instead, however, it may include an optical scanning unit such as a galvanometer mirror for two-dimensionally scanning the excitation light E, and an optical detector such as a photomultiplier tube may be used as the optical detector. In this case, to correct the image blur by rotating the objective lens  5  about the object-side focal point F OB , the center position of the range of rotation of the galvanometer mirror should be offset. 
         [0121]    Regarding the timing at which images are acquired, after rotating the objective lens  5  and the correction mirrors  44 ,  44   a , and  44   b  with high-speed driving actuators to move the objective lens  5  and the correction mirrors  44 ,  44   a , and  44   b  to desired positions, it is preferable to perform image acquisition with these components in a stationary state in order to allow image blur to be reduced. 
         [0122]    Because the objective lens  5  is driven based on the detected displacement of the specimen S, as the optical detector  9  for detecting the displacement of the specimen S, it is preferable to use a detector with a higher speed than the optical detector  8  for acquiring images. 
         [0123]    In the embodiment described above, two kinds of light having different wavelengths may be emitted from the excitation light source  3 ; then, for example, the displacement of the specimen S may detected using the longer wavelength light, and fluoroscopy may be carried out using the shorter wavelength light. In this case, the beamsplitter  7  should be a dichroic mirror. 
         [0124]    Regarding a method of adjusting the command signals sent to the objective-lens driving mechanism  11 , in particular, when the displacement of the specimen is periodic, the objective lens  5  is continuously and periodically driven in the X, Y, Z, A, and B directions, for example, using a signal from a frequency oscillator. While the operator views the acquired images on a monitor, he or she may manually adjust the driving frequency and amplitude in each oscillation direction so as to minimize the defocus, blur, and image blur thereof. 
         [0125]    Next, a method of securing a specimen  100  according to an embodiment of the present invention will be described with reference to  FIG. 25 . 
         [0126]    As shown in  FIG. 25 , the method of securing the specimen  100  according to this embodiment involves securing the specimen  100 , such as a small laboratory animal like a mouse which is mounted on a stage  71 , using a tensile force of a sheet member  72 . As the sheet member  72 , it is preferable to use a transparent film. After the specimen  100  is covered with the sheet member  72  and a predetermined tensile force is applied, the sheet member  72  is secured to the stage  71  using any type of securing member, for example, adhesive tape (not shown in the drawing). 
         [0127]    With the method of securing the specimen  100  according to this embodiment, the specimen  100  is covered with the sheet member  72 , formed of film, over a wide area, the entire specimen  100  is pressed by the tensile force exerted by the sheet member  72 , and it is possible to press it against the stage  71 . Accordingly, it is possible to reliably restrict pulsating of the specimen  100  without applying a strong pressing force locally to the specimen  100 . Therefore, an excessive stress is not placed on the specimen  100 , the viability of the specimen  100  is maintained during examination, and it is thus possible to carry out in vivo examination with the specimen  100  at rest. 
         [0128]    By using the sheet member  72  formed of a transparent film, as shown in  FIG. 25 , it is possible to bring an objective lens  73  close to the specimen  100  to observe an examination site P thereof while leaving the sheet member  72 , which suppresses pulsing of the specimen  100 , interposed therebetween. Accordingly, it is possible to prevent shifting of the examination site P due to dynamic motion of the specimen  100 , such as a pulse, and therefore, it is possible to acquire clear examination images in which blurring is prevented. 
         [0129]    In the method of securing the specimen  100  according to this embodiment, it has been describe that the specimen  100  is entirely covered with a single sheet member  72  to secure it to the stage  71 . Instead of this, however, as shown in  FIG. 26 , the specimen  100  may be partially covered using two or more strips of sheet members  72 . In this case also, because a pressing force is applied to the specimen  100  over a wide area, an excessive pressing force is prevented from being applied to the specimen  100 . 
         [0130]    Moreover, with this configuration, it is possible to expose the examination site P of the specimen  100  without covering it with the sheet member  72 , and it is thus possible to acquire a clearer examination image. 
         [0131]    In the case where the specimen  100  is secured to the stage  71  by covering the specimen  100  with a single sheet member  72  as in  FIG. 25 , by providing a through-hole  74  in the sheet member  72  and covering the specimen such that the through-hole  74  is aligned with the examination site P, as shown in  FIG. 27 , it is possible to expose the examination site P and to perform examination thereof while suppressing pulsing of the specimen  100  using the tensile force of the sheet member  72 . 
         [0132]    Thus, if it is possible to expose the examination site P in this way, the material of the sheet member  72  is not limited to a transparent material. It is possible to use a sheet member  72  made of any type of material, and therefore, it is possible to select a material having the optimum flexibility, strength, and so forth for securing the specimen  100 . 
         [0133]    As shown in  FIG. 28 , if it is not possible to suppress the pulsing using only the sheet member  72 , it may be additionally suppressed using a stabilizer  75  which extends from outside of the stage  71 . Two or more of the stabilizers  75  may be provided. It is also possible to provide two or more supports  75   a.    
         [0134]    Next, a securing apparatus  80 , for securing the specimen  100 , according to an embodiment of the present invention will be described below with reference to  FIGS. 29 to 31 . 
         [0135]    As shown in  FIG. 29 , the securing apparatus  80  according to this embodiment includes a frame  81  having an opening  81   a ; a sheet member  82  which is stretched over the opening  81   a  in the frame  81 ; and a pressing portion  83  for pressing the frame  81  towards the stage  71 . 
         [0136]    As shown in  FIG. 31 , the frame  81  includes a pair of frame-shaped plates  84  and clips (joining portions)  85  for keeping these frame-shaped plates  84  joined so that they are stacked together. 
         [0137]    As shown in  FIG. 29 , each frame-shaped plate  84  has a substantially square outer shape and is provided, at the center thereof, with the opening  81   a , which is larger than the specimen  100  mounted on the stage  71 . At the peripheral parts of each frame-shaped plate  84 , a plurality of through-holes  86  are provided at positions which are aligned when they are stacked together. 
         [0138]    The clips  85  are formed of leaf spring members which sandwich the stacked frame-shaped plates  84  in the thickness direction and press the frame-shaped plates  84  to each other with a pressing force which is determined by the spring constant thereof to keep them in tight contact. In this embodiment, the clips  85  are disposed on the respective edges of the substantially square frame-shaped plates  84 . 
         [0139]    The sheet member  82  is formed, for example, of a transparent film. The sheet member  82  is sandwiched by the two frame-shaped plates  84  and is pressed by the clips  85 . Therefore, the sheet member  82  is secured in the frame plates  84  so as to seal off the opening  81   a.    
         [0140]    The pressing portion  83  is formed of a plurality of bolts  87  which are inserted in the through-holes  86  provided in the frame-shaped plates  84  and threaded holes  88  which are provided in the stage  71  and with which the bolts  87  engage. 
         [0141]    The operation of the securing apparatus  80  for securing the specimen  100  according to this embodiment, configured in this way, will be described below. 
         [0142]    To secure the specimen  100  on the stage  71  using the securing apparatus  80  according to this embodiment, as shown in  FIG. 29 , the sheet member  82  attached to the frame  81  is lowered from above the specimen  100  mounted on the stage  71  and is brought into contact with the specimen  100 . Then, the bolts  87  passing through the through-holes  86  in the frame-shaped plates  84  are engaged with the threaded holes  88  in the stage  71 . 
         [0143]    By gradually screwing the bolts  87  into the threaded holes  88 , the frame  81  is pressed down towards the stage  71 , and therefore, the tensile force of the sheet member  82  increases, and the pressing force applied to the specimen  100  increases. 
         [0144]    Accordingly, as shown in  FIG. 30 , the specimen  100  is pressed by the sheet member  82  over a wide area, and by adjusting the fastening of the bolts  87 , it is possible to adjust the tensile force applied to the sheet member  82 , which allows the specimen  100  to be secured to the stage  71  with an appropriate pressing force. Therefore, the stress placed on the specimen  100  is reduced, and it is thus possible to maintain the viability of the specimen  100 . 
         [0145]    Because the sheet member  82  is formed of a transparent film, it is possible to observe the examination site of the specimen  100  while keeping the sheet member  82  interposed therebetween. Thus, with the securing apparatus  80  according to this embodiment, it is possible to prevent shifting of the examination site P due to dynamic motion of the specimen, such as a pulse, which enables the acquisition of clear examination images in which blur is prevented. 
         [0146]    In this embodiment, by sandwiching the sheet member  82  with the pair of frame-shaped plates  84  and fastening it with the clips  85 , the sheet member  82  is secured in the frame-shaped plates  84 . Therefore, when changing the specimen  100  or if the sheet member  82  becomes broken, it is possible to easily replace the sheet member  82  merely by removing the clips  85 . 
         [0147]    In the securing apparatus  80  for securing the specimen  100  according to this embodiment, the frame  81  includes the pair of frame-shaped plates  84  and the clips  85  for tightly joining these frame-shaped plates  84 . Instead of this however, the frame  81  may be formed of a single frame-shaped plate  84 , and the sheet member  82  may be bonded to the frame-shaped plate  84 . 
         [0148]    Although a joining portion in which the pair of frame-shaped plates are joined by the clips  85  is formed, instead of this, the joining portion may be constituted by forming one of the frame-shaped plates of a magnet and forming the other one of a magnet or magnetic material. By doing so, it is possible to join both frame-shaped plates  84  by a magnetic attraction force, and it is thus possible to keep the sheet member  82  sandwiched by the joining force thereof. 
         [0149]    A through-hole  74  similar to that shown in  FIG. 27  may be provided in the sheet member  82  which is stretched in the opening  81   a . Also, a plurality of strips of sheet members  72 , similar to those in  FIG. 26 , may be stretched in the opening  81   a.    
         [0150]    Although the bolts  87  and the threaded holes  88  which are engaged with each other are used as the pressing portion, it is possible to use any other type of securing member instead. 
         [0151]    The securing apparatus  80  according to this embodiment uses the substantially square frame-shaped plates  84 . Instead, however, as shown in  FIG. 32 , it is possible to used substantially circular frame-shaped plates  89 . 
         [0152]    With this configuration, the tensile force generated in the sheet member  82  by pressing the sheet member  82  on the specimen  100  can be made substantially uniform around the entire circumference thereof. Therefore, it is possible to prevent the tensile force from concentrating locally, and the sheet member  82  can thus be prevented from breaking. 
         [0153]    Next, a stage apparatus  90  according to an embodiment of the present invention will be described with reference to  FIG. 33 . 
         [0154]    As shown in  FIG. 33 , the stage apparatus  90  according to this embodiment includes a stage  91  for mounting a specimen  100 , and a securing apparatus  92 , provided in the stage  91 , for securing the specimen  100 . 
         [0155]    The securing apparatus  92  includes a frame  93  provided so as to be capable of rotating about a horizontal shaft  101  provided in the stage  91 ; a sheet member  94  which is stretched so as to seal off an opening  93   a  in the frame  93 ; and a pressing portion  95  for securing the frame  93  while the specimen  100  is pressed by the sheet member  94 . Similarly to  FIG. 29 , the pressing portion  95  includes threaded holes  96  provided in the stage  91  and bolts  97  which are engaged with the threaded holes  96 . 
         [0156]    With the stage apparatus  90  according to this embodiment, by mounting the specimen  100  on the stage  91 , rotating the frame  93  in which the sheet member  94  is stretched from a position indicated by the broken line in  FIG. 33  to a position indicated by the solid line, and engaging the bolts  97  inserted in the through-holes  98  provided in the frame  93  with the threaded holes  96  in the stage  91 , the specimen  100  can be secured to the stage  91  by a tensile force produced in the sheet member  94 . By doing so, the number of bolts to be engaged can be reduced, and it is possible to more easily secure the specimen  100  to the stage  91 . 
         [0157]    The specimen S and the specimen  100  according to the above embodiment may include small laboratory animals such as mice and rats. 
       Additional Items 
       [0158]    Aspects of the invention according to the following configurations are derived from the embodiments described above.