Abstract:
A microscope system includes: a stage that shifts a specimen in x and y directions; a detection section that detects a position of the stage after shifting; a reception section that receives an input of a shift target position for the stage inputted by an observer; an optical system that forms a light flux into a focused and magnified image of the specimen; an image capturing section that captures the magnified image; and a shift section that, if the position detected by the detection section and the shift target position received by the reception section do not agree with one another, shifts a relative positional relationship between the light flux and the image capturing section.

Description:
INCORPORATION BY REFERENCE  
         [0001]    The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 2001-214601, filed Jul. 16, 2001.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a microscope system which is equipped with a stage.  
           [0004]    2. Description of Related Art  
           [0005]    In a microscope which is equipped with an electrically driven stage, methods of setting the position of the electrically driven stage can broadly be classified into two categories.  
           [0006]    The first method is an open loop control method. In this method, the rotational amount for the motor required in order to arrive at the target point is calculated in advance, and the motor is rotated based thereupon. Generally a stepping motor is used.  
           [0007]    The second method is a closed loop control method. In this method, a sensor such as a linear encoder or the like is provided separately from the drive motor for detecting the position of the stage, and the motor is driven while comparing the present position with a target point, until the position of the target point is arrived at.  
           [0008]    When setting the position of an electrically driven stage, generally the position upon the image monitor to which the observer has tried to shift, i.e. the so called ‘shift target position’, and the position when the system has actually completed shifting, i.e. the so called ‘stage position’, do not perfectly agree with one another. As a result, a minute error exists between these two positions. Even though the error between the shift target position and the stage position may be a minute amount upon the surface of the object under examination, if the observation magnification is great, this becomes a great difference upon the display means such as a monitor or the like, and it can happen that the field of observation intended by the observer is not necessarily always attained. For example, if the shift amount accuracy of the stage is ±10 microns with regard to the shift target position in case that the magnification of the objective lens is 100 and the size of the CCD is a third inch (diagonal dimension: 6 mm), the error amount is 0.01 mm upon the surface of the object. However, the error amount becomes 1 mm on the image-capturing surface of the CCD, which corresponds to a sixth of the diagonal dimension on the monitor. In particular, with an electrically driven stage which utilizes the above described open loop control method, its construction and control are simple and low in cost. However, since only the rotational amount of the motor is controlled, errors can easily occur due to backlash of the lead screw or the like when the rotational amount of the motor is converted to the shift amount of the stage, and it becomes difficult to enhance the accuracy of positioning. Due to this, errors can easily occur between the shift target position and the stage position.  
           [0009]    On the other hand, with the above described closed loop control method, the position of the stage is detected in real time by the position detection sensor such as a linear encoder or the like, and it is possible to perform positioning while correcting the position of the stage until the difference from the shift target position is within a permitted range which is specified in advance. Due to this, it is possible to perform positioning at comparatively high accuracy. However, when a quite high positioning accuracy is demanded, so called hunting can take place in which the stage oscillates around the shift target position, since the permitted range described above is small. As a result the positioning may consume a considerable amount of time, and the phenomenon may even occur of the hunting continuing indefinitely.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention proposes a microscope system which can display an image of the target position at high speed and with high accuracy.  
           [0011]    A microscope system according to the present invention, comprises: a stage that shifts a specimen in x and y directions; a detection section that detects a position of the stage after shifting; a reception section that receives an input of a shift target position for the stage inputted by an observer; an optical system that forms a light flux into a focused and magnified image of the specimen; an image capturing section that captures the magnified image; and a shift section that, if the position detected by the detection section and the shift target position received by the reception section do not agree with one another, shifts a relative positional relationship between the light flux and the image capturing section. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is an explanatory figure showing the entire structure of a microscope system which is a first preferred embodiment of the present invention.  
         [0013]    [0013]FIG. 2 is a cutaway sectional figure showing the structure around a CCD  21  which is incorporated in this microscope system according to the first preferred embodiment of the present invention.  
         [0014]    [0014]FIG. 3 is a plan view showing the structure of an actuator  139  which carries a CCD  21  incorporated in a microscope system according to a third preferred embodiment of the present invention.  
         [0015]    [0015]FIG. 4 is an explanatory figure showing the structure of an actuator  149  which carries a focusing lens  13  incorporated in a microscope system according to a fourth preferred embodiment of the present invention.  
         [0016]    [0016]FIG. 5 is an explanatory figure showing the positional relationship between an effective pixel range A and a display pixel range B of the CCD  21  incorporated in the microscope system according to the first preferred embodiment of the present invention.  
         [0017]    [0017]FIG. 6 is an explanatory figure showing the positional relationship after shifting between the positional relationship between the effective pixel range A and the display pixel range B of the CCD  21  incorporated in the microscope system according to the first preferred embodiment of the present invention.  
         [0018]    [0018]FIG. 7 is an explanatory figure showing the positional relationship between the positional relationship between the effective pixel range A and the display pixel range B of the CCD  21  incorporated in the microscope system according to the first preferred embodiment of the present invention, when electronic zoom is being employed.  
         [0019]    [0019]FIG. 8 is a flow chart showing the operation of a calculation processing section of the microscope system according to the first preferred embodiment of the present invention, when the displayed image is being shifted.  
         [0020]    [0020]FIG. 9A is an explanatory figure for showing the structure of an electrically driven stage  30  of the microscope system according to the first preferred embodiment of the present invention, before shifting.  
         [0021]    [0021]FIG. 9B is an explanatory figure for showing the structure of an electrically driven stage  30  of the microscope system according to the first preferred embodiment of the present invention, after shifting.  
         [0022]    [0022]FIG. 10 is a cutaway sectional figure showing a parallel flat plate  14  which is disposed in a barrel  101  of the microscope system according to the fourth preferred embodiment of the present invention.  
         [0023]    [0023]FIG. 11 is a sectional figure showing a mechanism for tilting the parallel flat plate  14  of FIG. 10. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Preferred embodiments of the present invention will now be explained with reference to the drawings.  
         [0025]    First Embodiment  
         [0026]    A microscope system equipped with an electrically driven stage according to the first preferred embodiment of the present invention will be explained with reference to FIGS. 1, 2,  5 ,  6 ,  8 ,  9 A, and  9 B.  
         [0027]    This microscope system comprises a microscope  10 , a control device  50 , and a monitor  40 . The microscope  10  comprises an electrically driven stage  30 , a revolver  11 , an objective lens  12 , a barrel  101 , and a TV camera  20 . The TV camera  20  is connected to the upper portion of a barrel  101 . As shown in FIG. 2, this TV camera  20  comprises a CCD  21  as an image capturing element. A focusing lens  13  is disposed within the barrel  101  for focusing an observed image of the specimen into an image upon the CCD  21 . The control device  50  comprises an image processing section  51  and a calculation processing section  52 , and the output of the CCD  21  is inputted to the image processing section  51 . The revolver  11  and the electrically driven stage  30  are connected to the calculation processing section  52 . Furthermore, a mouse  60  and a monitor  40  are connected to the control device  50 .  
         [0028]    The electrically driven stage  30  comprises an x stage  121  for carrying the specimen  120  as shown in FIG. 9A, a stepping motor  31  and a lead screw section  124  for shifting the x stage  121  in the x direction, a y stage  126  which carries the x stage  121 , and a stepping motor  32  and a lead screw section  125  for shifting the y stage  126  in the y direction. Furthermore, respective linear scales  122   a  and  123   a  of linear encoders  122  and  123  are connected to the x stage  121  and to the y stage  126 , respectively. And respective sensors  122   b  and  123   b  of the linear encoders  122  and  123  are fitted to the lead screw sections  124  and  125 , respectively. The rotational motion of the stepping motors  31  and  32  is converted into rectilinear motion by lead screws (not particularly shown) of the lead screw sections  124  and  125  respectively, and thereby the x stage  121  and the y stage  126  are respectively driven in the x direction and in the y direction (refer to FIG. 9B). At this time, the sensors  122   b  and  123   b  detect the positions of the linear scales  122   a  and  123   a , respectively. In this manner, the (x, y) coordinates of the x and y stages  121  and  126  are detected. The stepping motors  31  and  32  are connected to the calculation processing section  52 , and operate according to rotational amounts which are commanded by the calculation processing section  52 . Furthermore, the outputs of the sensors  122   b  and  123   b  are inputted to the calculation processing section  52 .  
         [0029]    As shown in FIG. 5, the CCD  21  has an effective pixel range A over which the image capturing pixels are arranged vertically and horizontally. The CCD  21  is capable of capturing an image of an observation image which has been focused upon this effective pixel range A. The output of the CCD  21  is inputted to the image processing section  51 . The image processing section  51  outputs an image within a display pixel range B which is surrounded by the four coordinate points (X1, Y1), (X2, Y2), (X3, Y3) and (X4, Y4) which are determined upon in advance within the effective pixel range A, to the monitor  40  so as to display it.  
         [0030]    The revolver  11  is provided with a plurality of holes for attachment of objective lenses, so that a plurality of objective lenses can be fitted thereto. A sensor (not particularly shown) is provided within the revolver  11  for detecting the rotation angle of the revolver  11 . The output of this sensor is inputted to the calculation processing section  52  of the control device  50 . The calculation processing section  52  stores in an internal memory a table which establishes in advance a correspondence between the addresses assigned to the plurality of objective lens attachment holes and the outputs of the sensor. Furthermore, in this table, there is also included information which establishes a correspondence between the addresses assigned to the objective lens attachment holes, and the observation magnifications M which are the results of multiplying the magnifications of the objective lenses which are fitted to those objective lens attachment holes by the magnifications of the focusing lens  13  and of other lenses such as relay lenses and the like. By consulting the above described table, the calculation processing section  52  identifies the address of the objective lens attachment hole which is currently upon the optical axis from the rotation angle which is outputted from the sensor, and is able to obtain the observation magnification M therefrom.  
         [0031]    The calculation processing section  52  controls the electrically driven stage  30  according to the flow chart of FIG. 8 by reading in a program stored in its internal memory and executing it. First, in a step  81 , the calculation processing section  52  reads in the present position (x0, y0) via the linear encoders  122  and  123 . Next, a display is provided upon the monitor  40  in order to urge the observer to input a shift target position (xd, yd) on the specimen  120 . And, in a step  82 , a target position is received from the observer by designation according to a clicking action of the mouse  60  upon the display image which is being presented upon the monitor  40 . Furthermore, the observation magnification M is obtained by looking up in the table in the memory with the rotation angle of the revolver  11  which has been received from the sensor. Then, also in the step  82 , the shift target position upon the monitor is converted into the coordinates (xd, yd) of the target position upon the specimen  120  (upon the electrically driven stage  30 ) from this observation magnification M and the target position upon the monitor. Next, the values xM=(xd−x0) and yM=(yd−y0) are calculated from the present position (x0, y0) and from the target position (xd, yd) which have been obtained in the steps  81  and  82  described above, and the shift amounts xM and yM for the electrically driven stage  30  are obtained (in the step  83 ).  
         [0032]    It should be understood that, the present position means the position according to the x, y coordinates of the specimen, which is being displayed at present, corresponding to a predetermined position upon the screen of the monitor  40  (for example the center of the screen). The present position before shifting is the position (x0, y0) according to the above description. And, the target position (xd, yd) means the position in the present x, y coordinates which the observer desires to shift to the predetermined position upon the screen of the monitor  40  (for example the center of the screen).  
         [0033]    The rotational amounts for the stepping motors  31  and  32  which correspond to the obtained shift amounts xM and yM are calculated using a ratio between stage shifting amount and motor rotational amount which has been obtained in advance and stored, and the rotational amounts which are obtained are outputted to the stepping motors  31  and  32 , in the step  84 . By doing this, the stepping motors  31  and  32  are rotated by just the rotational amounts which have been designated, and this rotational motion is converted into rectilinear motion by the lead screws incorporated in the lead screw sections  124  and  125 , and thereby the x stage  121  and the y stage  126  are driven in the x direction and the y direction, respectively (FIGS. 9A and 9B). After this driving has been completed, the calculation processing section  52  captures the present position (xz, yz) for a second time from the linear encoders  122  and  123  in the step  86 , compares it with the shift target position (xd, yd) in the step  87 , and determines, in the step  88 , whether or not its difference ((xz−xd), (yz−yd)) from the shift target position (xd, yd) is less than a standard value (xs, ys) which is determined in advance; i.e., it evaluates the conditions xs&gt;(xz−xd) and ys&gt;(yz−yd). If this difference is greater than the standard value (xs, ys) the flow of control returns to the step  83 , and the electrically driven stage  30  is driven for a second time to shift it. On the other hand, if the difference is less than the standard value (xs, ys), then the flow of control proceeds to the step  89 , in which the shift amount for the display image is calculated according to the following calculation equations. That is, it may be the case that the difference is less than the standard value (xs, ys), but that an error greater than a predetermined value is present. M in the calculation equations below is the observation magnification M which was obtained in the step  82 .  
           XΔ= ( xd−xz ) ×M    
           YA= ( yd−yz )× M    
         [0034]    Finally, in the step  90 , the calculation processing section  52  commands the image processing section  51  to shift the four coordinates (X1, Y1), (X2, Y2), (X3, Y3), and (X4, Y4) which determine the region of the display pixel range B by the amounts XΔ, YΔ which were obtained in the step  89 . Due to this, as shown in FIG. 6, the image processing section  51  outputs to the monitor  40  and displays, as the display pixel range B after shifting, the image in a region which is surrounded by the four coordinates (X1+XΔ, Y1+YΔ), (X2+XΔ, Y2+YΔ), (X3+XΔ,Y3+YΔ), and (X4+XΔ, Y4+YΔ). Due to this, the remaining error xd−xz, yd−yz upon the object plane (the surface of the specimen) is corrected upon the image plane, and an image which is centered upon the target position (xd, yd) is displayed upon the monitor  40 .  
         [0035]    It should be understood that there is an upper limit upon the shift amounts XΔ and YΔ, since the possible shift range of the CCD  21  for the display pixel range B is the effective pixel range A of the CCD  21 . Due to this, the above described standard values xs and ys are set as the upper limits for the shift amounts XΔ and YΔ. By doing this, if the difference between the present position (xz, yz) and the shift target position (xd, yd) is less than the values xs and ys which can be handled by shifting of the display pixel range B, then it is handled by shifting the display pixel range B; while, on the other hand, if the difference is greater than the values xs and ys, then the flow of control returns from the step  88  to the step  83  and the electrically driven stage  30  is shifted again. As a result, it is possible to display an image centered upon the shift target position (xd, yd) with good efficiency. It should be understood that, if the widths in the X and Y directions of the effective pixel range A are given by XA and YA, and the widths in the X and Y directions of the display pixel range B are given by XB and YB, then the upper limits for the shift amounts XΔ and YΔ are given as below (refer to FIG. 5). The X and Y directions upon the CCD  21  correspond to the x and y directions of the electrically driven stage  30 .  
         (Upper limit for  XΔ )=( XA−XB )/2  
         (Upper limit for  YΔ )=( YA−YB)/ 2  
         [0036]    Accordingly, by setting the standard values xs and ys according to:  
           xs= ( XA−XB )/2 M    
           ys= ( YA−YB )/2 M    
         [0037]    it is possible to display at high efficiency an image with the shift target position (xd, yd) centered. It should be understood that the above described standard values xs and ys could also be defined as the minimum unit amounts of the shift control amounts for the electrically driven stage  30 .  
         [0038]    It should be understood that, when the image processing section  51  is displaying an image upon the monitor  40 , it is also possible simultaneously to implement electronic zooming so as to magnify the image at a magnification determined in advance. In this case, the magnification of the electronic zooming is superimposed upon the above described observation magnification M. Furthermore, when utilizing this electronic zooming, if for example an electronic zoom of 2× is assumed, then the display pixel range B is smaller than the display pixel range A when using an electronic zoom of 1×, as shown in FIG. 7, and it is possible to take the shift amounts XΔ and YΔ greater. Accordingly, if electronic zooming is utilized, the method according to this preferred embodiment for shifting the specimen image by shifting the observation image side is very effective, since it is possible to take the shift amounts XΔ and YΔ greater. Moreover, if electronic zooming is utilized, it is desirable to prepare the standard values xs and ys for each electronic zooming magnification in advance.  
         [0039]    Second Embodiment  
         [0040]    The second preferred embodiment of the microscope system of the present invention has a structure in which the CCD  21  is carried upon an actuator  139  as shown in FIG. 3, and the CCD  21  can itself be physically shifted in the X and Y directions, so as to shift the image which is being displayed upon the monitor  40  in the X and Y directions. It should be understood that the X and Y directions of the CCD  21  correspond to the x and y directions of the electrically driven stage  30 . Accordingly, with this second preferred embodiment, in the step  90  of the flow chart for the first preferred embodiment shown in FIG. 8, instead of shifting the display pixel range B, piezo elements  134  and  135  which are the drive sources for the actuator  139  are driven, and the CCD  21  itself is shifted by just the amounts XΔ and YΔ.  
         [0041]    The actuator  139  comprises an X plate  130  which is formed by processing a flexible plate shaped member as shown in FIG. 3 by wire cutting, a Y plate  133  which supports the X plate  130  in cantilever fashion by two plate springs  131 , and a main body  136  which supports the Y plate  133  in cantilever fashion by two plate springs  132 . The CCD  21  is carried upon the X plate  130 . The lengthwise direction of the plate spring  131  is the Y direction, and the lengthwise direction of the plate spring  132  is the X direction. A piezo element  134  which can expand and contract in the X direction is disposed at the side surface of the X plate  130 . This piezo element  134  is supported by the Y plate  133 . Furthermore, a piezo element  135  which can expand and contract in the Y direction is disposed at the side surface of the Y plate  133 . This piezo element  135  is supported by the main body  136 . Thus the X plate  130  is shifted in the X direction when the piezo element  134  expands according to command by the calculation processing section  52 , and similarly the Y plate  133  (together with the X plate  130 ) is shifted in the Y direction when the piezo element  135  expands. Due to this, it is possible to shift the CCD  21  by exactly XΔ and YΔ.  
         [0042]    With this second preferred embodiment, up through the calculation of the shift amounts XΔ and YΔ in the step  89  of FIG. 8, the operations of the various elements are the same as in the first preferred embodiment. However, in the step  90 , the calculation processing section  52  extends the piezo elements  134  and  135  of the actuator  139  and shifts the CCD  21  itself in the X and Y directions, so that the remaining error (xd−xz), (yd−yz) upon the specimen  120  (the object plane) is corrected. By doing this, an image centered upon the target position (xd, yd) which has been inputted by the observer is projected upon the monitor  40 .  
         [0043]    With the structure of this second embodiment, the display pixel range B of the CCD  21  can be made to be the same range as the effective pixel range A. Accordingly, since all of the pixels of the CCD  21  can be utilized, it is beneficial from the point of view of picture quality,  
         [0044]    Third Embodiment  
         [0045]    The third preferred embodiment of the microscope system according to the present invention has a structure in which the focusing lens  13  is carried upon an actuator  149  as shown in FIG. 4, and, by shifting the focusing lens  13  in the X and Y directions, the image which is focused upon the CCD  21  is itself shifted in the X and Y directions. By doing this, the image which is being displayed upon the monitor  40  is shifted in the X and Y directions. The structure of the actuator  149  is the same as that of the actuator  139  of the second preferred embodiment described above, and accordingly its explanation will be curtailed.  
         [0046]    Accordingly, with this third preferred embodiment as well, just as with the second preferred embodiment described above, up through the step  89  of the flow chart of FIG. 8, the operation is the same as in the first preferred embodiment; but in the step  90 , instead of shifting the display pixel range B, the calculation processing section  52  drives the piezo elements  134  and  135  which are the drive sources for the actuator  149  to shift the focusing lens  13  itself in the X and Y directions, so that the observation image upon the CCD  21  is shifted. By doing this, an image centered upon the target position (xd, yd) which has been inputted by the observer is projected upon the monitor  40 .  
         [0047]    Fourth Embodiment  
         [0048]    A fourth preferred embodiment of the present invention will now be described with reference to FIGS. 10 and 11. This microscope system according to the fourth preferred embodiment has a structure which is the same as that of the first preferred embodiment, except for the feature that a parallel flat plate  14  is arranged upon the optical axis  100  between the focusing lens  13  and the CCD  21 , and the position of the image which is focused upon the CCD  21  is shifted in the X and Y directions by tilting this parallel flat plate  14 . In FIG. 10 the manner is shown in which the light flux (light beam or ray bundle)  146  from the specimen is shifted.  
         [0049]    The parallel flat plate  14  is a transparent glass parallel flat plate of circular form which is supported by a frame  141 . The frame  141  is provided around its circumference with three through holes  145 , and the frame  141  is fitted into the barrel  101  by screws  143  which are inserted in these through holes  145 . Springs  142  are fitted over the screws  143 , and these springs  142  bias the frame  141  towards the direction of the focusing lens  13 . Furthermore, piezo elements  144  are respectively arranged in the barrel  101  at positions somewhat towards the optical axis  100  from the three through holes  145  in the frame  141 . Accordingly it is possible to press upwards at these three places upon the frame  141  by any amounts desired by extending these three piezo elements  144 , so that it is possible to tilt the parallel flat plate  14  in any desired direction. By doing this, it is possible to shift the position of the image which is focused upon the CCD  21  in the X and Y directions by any desired amount.  
         [0050]    In other words, this fourth preferred embodiment takes advantage of the difference between the index of refraction of the glass from which the parallel flat plate  14  is formed and the index of refraction of the surrounding air.  
         [0051]    Accordingly, with the structure of this fourth preferred embodiment of the present invention, up through the step  89  of the flow chart of FIG. 8, the operation is the same as in the first preferred embodiment; but, in the step  90 , the calculation processing section  52  calculates tilt angles for the parallel flat plate  14  in the X and Y directions in order to shift the image upon the CCD  21  by just the shift amounts XΔ and YΔ, determines amounts of extension for three piezo elements  144  for applying these tilt angles, and extends the piezo elements  144  by just these extension amounts. By doing this, the observation image upon the CCD  21  is shifted by just the shift amounts XΔ and YΔ. Thus, it is possible for an image centered upon the target position (xd, yd) which has been inputted by the observer to be projected upon the monitor  40 .  
         [0052]    It should be understood that the tilt angles for the parallel flat plate  14  are calculated in consideration of the thickness and the index of refraction of the parallel flat plate  14 .  
         [0053]    With the above described first through fourth preferred embodiments of the present invention, not only the positioning operation when displaying an image of the desired coordinates upon the specimen is performed upon the object plane side (the stage side), but also final positioning is performed by applying adjustment or correction upon the image plane. Due to this it is possible to apply corrections comparatively simply, even with difficult positioning which is minute upon the object plane side, since they are magnified upon the image plane side because magnification is applied. Accordingly, as a result, it is possible to implement high accuracy and also high speed positioning, since it is possible to ensure high positioning accuracy even if the positioning at the object plane is quite rough. In particular, with the structure of the first preferred embodiment, it is possible to enhance the speed and the reliability especially effectively, since no mechanical moving parts at all are employed during the adjustment at the image plane side.  
         [0054]    It should be understood that, although in the above description of the first through fourth preferred embodiments of the present invention structures for the microscope system were explained in which the microscope  10 , the TV camera  20 , and the electrically driven stage  30  were each provided as a separate independent component and were all individually connected to the control device  50 , the present invention is not to be considered as being limited to this structure; it would also be possible for the microscope system to be implemented with a structure in which the control device  50  is housed within the microscope  10 , and the TV camera  20  and the electrically driven stage  30  are formed integrally with the microscope  10 .  
         [0055]    Furthermore, although in the first preferred embodiment of the present invention the stepping motors  31  and  32  were used as drive sources for the electrically driven stage  30 , it would also be possible to use DC motors. In such a case, it would be desirable to perform closed loop control with shifting while detecting the present position with the linear encoders  122  and  123 .  
         [0056]    The above described embodiments are examples, and various modifications can be made without departing from the spirit and scope of the invention.