Abstract:
A microscope with a dynamic damper, and an optical system including a plurality of optical elements and having an optical axis. The dynamic damper attenuates vibration of the microscope in the direction of the optical axis by using part of the plurality of optical elements as a mass displaceable in the direction of the optical axis in accordance with said vibration.

Description:
[0001]    This application is a continuation of application Ser. No. 09/375,434 filed Aug. 17, 1999. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to a microscope with a dynamic vibration absorber.  
           [0004]    2. Description of Related Art  
           [0005]    In a microscope of high resolving power, slight vibration will cause a great disturbance. Accordingly, measures against the vibration have been taken. For example, an air table and a rubber foot are used therefor.  
           [0006]    The air table attenuates vibration from the floor by utilizing an air spring or the like and serves as a table for mounting a microscope. Further, there is proposed an air table in which a sensor detects vibration of the table to drive and control actuators provided between the floor and the table so that the vibration can be cancelled.  
           [0007]    The rubber foot is arranged on the bottom surface of a microscope to prevent the microscope from becoming unsteady and to attenuate vibration transmitted from a surface on which the microscope is located. In addition, the rubber foot can reduce rolling or pitching of the whole microscope.  
           [0008]    Furthermore we know a dynamic vibration absorber (a dynamic damper) which is a kind of means for attenuating vibration.  
           [0009]    The dynamic vibration absorber reduces vibration by means of a force due to vibration of a mass and is divided into a passive dynamic vibration absorber and an active dynamic vibration absorber. The passive dynamic vibration absorber comprises a mass, a spring element, and a damping element. A plurality of masses, springs and/or damping elements may be used in some kinds of apparatus. The active dynamic vibration absorber uses a vibration sensor to detect vibration and drives a mass by means of an actuator to reduce the vibration. The dynamic vibration absorber is applied to various technologies such as construction and automobile industries and is disclosed in, for example, Japanese Laid-Open Patent Publication Nos. Hei 3-250165 and Hei 8-21483.  
           [0010]    In the passive dynamic vibration absorber, the mass is secured via the spring element and the damping element to a structure whose vibration should be reduced. When the structure vibrates so that the relative displacement between the mass and the structure varies, vibration energy is consumed by the damping element between the mass and the structure, thereby attenuating the vibration.  
           [0011]    In the active dynamic vibration absorber, the mass is secured via the actuator to a structure whose vibration should be reduced. After the vibration sensor detects vibration of the structure, the actuator drives the mass according to the detected vibration so that the vibration of the structure can be cancelled by a force of the mass.  
           [0012]    As described above, in a microscope of high resolving power, vibration is reduced by means of an air table, a rubber foot, a dynamic vibration absorber, or the like. However, in recent years, these measures against the vibration have become insufficient.  
           [0013]    For example, microscopes having a resolving power of 1 nm or less, such as a tunneling microscope (see U.S. Pat. No. 4,823,044) and an atomic force microscope (see U.S. Pat. No. 5,260,824 and U.S. Pat. No. 5,672,816), have been put to practical use. Further, a scanning laser microscope provides an observation image which is very clear in comparison with that of a conventional microscope. These microscopes require very strict setting environments. For example, air vibration caused by voice, noise, an air conditioner or the like will cause a deterioration of the observation image.  
           [0014]    Further, a motor driving mechanism is incorporated in a microscope for electrical driving and is also a source of vibration. That is, when the driving mechanism operates to move a sample stage, perform focusing, or change over filters, prisms or the like, mechanical vibration is generated from the driving mechanism.  
           [0015]    Under the circumstances, the air table is used for the measures against the vibration. The air table is to insulate a structure on the table from floor vibration and is not effective in insulating the structure from a disturbance, such as air vibration caused by voice, noise, an air conditioner or the like, and mechanical vibration generated by an electrically driven microscope itself.  
           [0016]    The rubber foot is to prevent a microscope from being unsteady when it is installed, and to reduce rolling or pitching of the entire microscope. It does not directly contribute to reducing the vibration that varies the relative positions of a sample and an observation optical system.  
           [0017]    The dynamic vibration absorber is used for reducing air vibration caused by voice, noise, an air conditioner or the like, and mechanical vibration generated by an electrically driven microscope itself that are applied to a structure affecting an observation image of a sample, such as an objective lens and a sample stage. That is, the dynamic vibration absorber is suitable for reducing local vibration, but has the problems that its setting place is restricted and that the microscope becomes heavy because the mass is used.  
           [0018]    It is explained why the setting place is restricted. In the microscope, the structures whose vibration should be reduced are the sample stage and the observation optical system. In many cases, the observation optical system is supported by a cantilever-type frame. Since the cantilever-type frame has a shape that is susceptible to vibration, it is desired to reduce the vibration. However, as the observation optical system exists, the setting place of the dynamic vibration absorber is restricted. Accordingly, in the conventional microscope system, the space for incorporation the dynamic vibration absorber has not been studied.  
           [0019]    The reason why the microscope becomes heavy due to the use of the mass is as follows: Since the passive dynamic vibration absorber has no vibration sensor, it cannot cope with a change of the structure whose vibration should be reduced, especially when the equivalent mass (mass of a physical model of a structure) of the mass is smaller than that of the structure whose vibration should be reduced. Since the frame of a microscope is highly rigid and its equivalent mass is large, a heavy mass is required. Accordingly, the microscope becomes heavy (and a large setting space is also necessary). When the microscope becomes substantially heavy, it is necessary to redesign the frame or the like.  
         BRIEF SUMMARY OF THE INVENTION  
         [0020]    In an embodiment of the present invention, a microscope having an optical axis has a frame including a base arm, a column extending vertically from the base arm and an upper arm. Dynamic damper includes a fixed part coupled to the upper side of the upper arm, and a movable part supported for linear movement in the direction of the optical axis with respect to the fixed part. An optical system is coupled to the movable part, the optical system comprising a displaceable mass of the dynamic damper. Parallel light rays extend along part of the optical axis, with the dynamic damper surrounding the optical axis at the position of the parallel light rays.  
           [0021]    The microscope may also include a sensor for detecting vibration of the fixed part, and outputting a vibration signal, an actuator for moving the movable part in a direction of the optical axis; and a controller for outputting a driving signal to move the actuator, the driving signal generated on the basis of the vibration signal so as to attenuate the vibration.  
           [0022]    A damping member for attenuating the vibration of the movable part with respect to the fixed part may be disposed between the movable part and the fixed part. The microscope may be, for example, a laser scanning microscope or a confocal microscope. The optical system may be an ocular tube or an ocular tube, and an intermediate attachment. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
         [0024]    [0024]FIG. 1 is a side view of a microscope with an active dynamic vibration absorber according to a first embodiment of the present invention.  
         [0025]    [0025]FIG. 2 is a side view of a frame of the microscope in FIG. 1.  
         [0026]    [0026]FIG. 3 is a sectional view of the active dynamic vibration absorber of the microscope in FIG. 1.  
         [0027]    [0027]FIG. 4 is a schematic view of a physical model of the active dynamic vibration absorber in FIG. 3.  
         [0028]    [0028]FIG. 5 is a graph of frequency response showing a vibration reducing effect of the active dynamic vibration absorber in FIG. 3.  
         [0029]    [0029]FIG. 6 is a side view of a microscope with a passive dynamic vibration absorber according to a second embodiment of the present invention.  
         [0030]    [0030]FIG. 7 a sectional view of the passive dynamic vibration absorber of the microscope in FIG. 6.  
         [0031]    [0031]FIG. 8 is a schematic view of a physical model of the passive dynamic vibration absorber in FIG. 7.  
         [0032]    [0032]FIG. 9 is a side view of a microscope with dynamic vibration absorbers according to a third embodiment of the present invention.  
         [0033]    [0033]FIG. 10 is a side view of a measuring microscope with an active dynamic vibration absorber according to a fourth embodiment of the present invention.  
         [0034]    [0034]FIG. 11 is a side view of a confocal microscope with an active dynamic vibration absorber according to a fifth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
       [0035]    Referring to the drawings, a first embodiment of the present invention is described.  
         [0036]    [0036]FIG. 1 shows the structure of a microscope with an active dynamic vibration absorber.  
         [0037]    A frame  1  of the microscope is provided with a sample stage  2 , on which a sample M is mounted. The frame  1  has an arm  3  projecting above the sample stage  2 . Above the arm  3 , there are an ocular tube  4 , an intermediate attachment  5  and a CCD camera  6  which constitute an observation optical system. Mounted on a lower surface of the arm  3  is a revolving nosepiece  7  with a plurality of infinity-corrected objectives  8 . The ocular tube  4  is provided with an imaging lens  9  which focuses parallel observation rays L from the objective  8  upon an image plane  6   a  of the CCD camera  6 . The microscope is also provided with an illumination optical system for illuminating the sample M.  
         [0038]    The microscope comprises a dynamic vibration absorber unit  10  for reducing vibration of the arm  3  that is a structure whose vibration should be reduced. When the frame  1  vibrates as shown in FIG. 2, the relative positions of the observation optical system and the sample M vary because of the vibration so that an observation image will be blurred. Accordingly, it is necessary to reduce the vibration of the frame  1  by means of the dynamic vibration absorber.  
         [0039]    The dynamic vibration absorber unit  10  is arranged between the arm  3  and microscope components: the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 , which constitute the observation optical system functioning as a mass  20  of the active dynamic vibration absorber.  
         [0040]    [0040]FIG. 3 shows a structure of the dynamic vibration absorber unit  10 .  
         [0041]    The dynamic vibration absorber unit  10  comprises a cylindrical structure-side member  11  on the side of the structure whose vibration should be reduced; a mass-side member  12  slidably fitted into the structure-side member  11 ; and a piezoelectric actuator  13  and a spring  14  interposed between the structure-side member  11  and the mass-side member  12 . The piezoelectric actuator  13  and the spring  14  support the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 . The piezoelectric actuator  13  expands and contracts in the Z-direction to drive the ocular tube  4 ,the intermediate attachment  5  and the CCD camera  6  that constitute the mass  20 . The piezoelectric actuator  13  may be replaced with a voice coil.  
         [0042]    On the upper surface of the mass-side member  12 , there should be mounted, via a dovetail, the mass  20  comprising the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 . The lower surface of the structure-side member  11  is to be attached, via a dovetail, to the arm  3  that is the structure whose vibration should be reduced. Via these dovetails, the dynamic vibration absorber unit  10  can be attached to a conventional microscope system.  
         [0043]    Further, the structure-side member  11  is provided with a vibration sensor  15  for detecting vibration of the arm  3  that is the structure whose vibration should be reduced. As the vibration sensor  15 , for example, a piezoelectric acceleration sensor is used in view of its frequency band, sensitivity and size.  
         [0044]    A vibration sensor signal p outputted from the vibration sensor  15  is inputted to a controller  16  (FIG. 1) which has the following function: in accordance with the vibration of the arm  3  represented by the vibration sensor signal p, the controller  16  operates to derive an actuator drive signal s for reducing the vibration of the arm  3  and transmits the actuator drive signal s to the piezoelectric actuator  13 .  
         [0045]    Referring to FIG. 4, a physical model of the active dynamic vibration absorber constituted as described above is explained. M represents the equivalent mass of the arm  3  that is the structure whose vibration should be reduced. K 1  and C respectively denote the equivalent stiffness and equivalent damping of the arm  3 . These constitute a physical model Q 1  of the arm  3 .  
         [0046]    Further, m denotes the mass  20  (the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 ), K 2  a spring element of the spring  14 , and f the piezoelectric actuator  13 . These and the vibration sensor  15  and the controller  16  constitute a physical model Q 2  of the dynamic vibration absorber.  
         [0047]    Next, the vibration reducing operation in the microscope constituted as described above is explained.  
         [0048]    In the arm  3  of the frame  1 , vibration of the natural frequency of the arm  3  is produced by air vibration (such as wind or sound), vibration from the floor, internal mechanical vibration due to the operation of the-microscope, or the like. when the arm  3  vibrates, the relative distance between the sample stage  2  and the objective  8  varies so that the observation image will be blurred.  
         [0049]    The vibration sensor  15  detects the vibration of the arm  3  and outputs the vibration sensor signal p, which is inputted to the controller  16 . As described above, in accordance with the vibration of the arm  3  represented by the vibration sensor signal p, the controller  16  operates to derive the actuator drive signal s for reducing the vibration of the arm  3  and transmits the actuator drive signal s to the piezoelectric actuator  13 .  
         [0050]    The piezoelectric actuator  13  vibrates in the Z-direction the mass  20  comprising the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6  so that the force of the mass  20  can reduce the vibration of the arm  3 .  
         [0051]    [0051]FIG. 5 is a graph of frequency response showing a vibration reducing effect of the dynamic vibration absorber. f 1  denotes the amplitude of vibration of the arm  3  without the dynamic vibration absorber, f 2  the amplitude of vibration of the arm  3  with the dynamic vibration absorber, and f 3  the natural frequency of the arm  3 . This figure shows that resonance peak at the natural frequency can be reduced by the dynamic vibration absorber.  
         [0052]    As described above, in the first embodiment, the dynamic vibration absorber unit  10  is arranged between the arm  3  and the mass  20  comprising the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 , so as to reduce the vibration of the arm  3 . Accordingly, the microscope of this embodiment can be provided with the dynamic vibration absorber unit  10  without changing the structure of the microscope. Thus, the dynamic vibration absorber unit  10  can be introduced into the microscope system without restriction of its setting place and without increasing the weight of the microscope. It is also possible to arrange the dynamic vibration absorber unit  10 , for example, between the arm  3  and the revolving nosepiece  7  or between the revolving nosepiece  7  and the objective  8  so as to reduce the vibration of the revolving nosepiece  7  or the objective  8 .  
         [0053]    This embodiment is also advantageous in that the dynamic vibration absorber unit  10  does not affect the observation image since the observation rays L passing through the dynamic vibration absorber unit  10  between the arm  3  and the ocular tube  4  are parallel rays.  
       Second Embodiment  
       [0054]    Referring to the drawings, a second embodiment of the present invention is described. The same elements as those shown in FIG. 1 are assigned the same reference numerals and characters and their descriptions are omitted.  
         [0055]    [0055]FIG. 6 shows the structure of a microscope with a passive dynamic vibration absorber.  
         [0056]    The microscope is provided with a dynamic vibration absorber unit  30  for reducing vibration of an arm  3  which is a structure whose vibration should be reduced. The dynamic vibration absorber-unit  30  is arranged between the arm  3  and a mass  20  of the dynamic vibration absorber, the mass  20  comprising an ocular tube  4 , an intermediate attachment  5  and a CCD camera  6  that constitute an observation optical system.  
         [0057]    [0057]FIG. 7 shows a structure of the dynamic vibration absorber unit  30 .  
         [0058]    The dynamic vibration absorber unit  30  comprises a cylindrical structure-side member  11  on the side of the structure whose vibration should be reduced; a mass-side member  12  slidably fitted into the structure-side member  11 ; and a damping member  31  and a spring  14  interposed between the structure-side member  11  and the mass-side member  12 . The damping member  31  and the spring  14  support the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 .  
         [0059]    The damping member  31  has a function of expanding and contracting in the Z-direction in accordance with vibration of the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6  so as to reduce their vibration. The damping member  31  is made of, for example, silicone rubber or urethane rubber and has both mechanical properties and spring properties. If the damping member  31  and the spring  14  are exchangeable with those having different characteristics, the characteristics of the dynamic vibration absorber unit  30  can be varied in order to cope with the exchange of the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 .  
         [0060]    The natural frequency of the dynamic vibration absorber is determined by the damping member  31 , the spring  14  and the mass  20 . When this natural frequency is identical with the natural frequency of the arm  3  which is the structure whose vibration should be reduced, the effect of reducing the vibration is large. Accordingly, the damping member  31 , the spring  14  and the mass  20  are selected so that the natural frequency of the dynamic vibration absorber is identical with that of the arm  3 .  
         [0061]    The spring  14  is exchangeable or adjustable so that the dynamic vibration absorber can be adjusted when the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 , which function as the mass  20 , are exchanged.  
         [0062]    [0062]FIG. 8 shows a physical model of the active dynamic vibration model. M represents the equivalent mass of the arm  3  that is the structure whose vibration should be reduced. K 1  and C respectively denote the equivalent stiffness and equivalent damping of the arm  3 . These constitute a physical model Q 1  of the aria  3 .  
         [0063]    Further, m denotes the mass  20  (the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 ), K 2  a -spring element of the spring  14 , and Ca the damping member  31 . These constitute a physical model Q 3  of the dynamic vibration absorber.  
         [0064]    Next, the vibration reducing operation in the microscope constituted as, described above is explained.  
         [0065]    In the arm  3  of the frame  1 , vibration of the natural frequency of the arm  3  is produced by air vibration (such as wind or sound), vibration from the floor, internal mechanical vibration due to the operation of the microscope, or the like. When the arm  3  vibrates, the relative distance between a sample stage  2  and an objective  8  varies so that the observation image will be blurred.  
         [0066]    When the arm  3  vibrates, then the mass  20  (the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 ) above the arm  3  also vibrates and the damping member, 31  and the spring  14  arranged between the arm  3  and the mass  20  expand and contract. At this time, vibration energy is converted into thermal energy. Thus, the vibration energy is consumed by the expansion and contraction of the damping member  31  so that the vibration of the arts  3  is reduced.  
         [0067]    As described above, in the second embodiment, the dynamic vibration absorber unit  30  is arranged between the arm  3  and the mass  20  comprising the ocular tube  4 , the intermediate attachment  5  and the CCD camera  6 , so as to reduce the vibration of the arm  3 . Accordingly, just like in the first embodiment, the microscope of this embodiment can be provided with the dynamic vibration absorber unit  30  without changing the structure of the microscope. Thus, the dynamic vibration absorber unit  30  can be introduced into the microscope system without restriction of its setting place and without increasing the weight of the microscope. It is also possible to arrange the dynamic vibration absorber unit  30 , for example, between the arm  3  and a revolving nosepiece  7  or between the revolving nosepiece  7  and the objective  8  so as to reduce the vibration of the revolving nosepiece  7  or the objective  8 .  
         [0068]    Since this embodiment does not require the controller  16  of the first embodiment, the setting space of the dynamic vibration absorber unit  30  is less restricted than in the first embodiment.  
         [0069]    Further, the dynamic vibration absorber unit  30  does not affect the observation image since the observation rays L passing through the dynamic vibration absorber unit  30  between the arm  3  and the ocular tube, 4  are parallel rays.  
       Third Embodiment  
       [0070]    Next, a third embodiment of the present invention is explained.  
         [0071]    [0071]FIG. 9 shows the structure of a laser scanning microscope (LSM) with dynamic vibration absorbers.  
         [0072]    The LSM is a microscope for visualizing optical information of a sample, for example, a three-dimensional image of the sample by irradiating a laser beam to a desired position of the sample and detecting the beam reflected from the sample. Such an LSM is described in, for example, U.S. Pat. No. 5,153,428, the contents of which is hereby incorporated by reference.  
         [0073]    A sample stage  41  and a frame  42  are provided on a base  40 . A laser light source  43  is fixed to the frame  42 . Arranged on the optical path of the laser beam emitted from the laser light source  43  are a half mirror  44 , galvanomirrors  45  and  46  for scanning the laser beam in the directions of the X- and Y-axes which are perpendicular to each other, a half mirror  47  and a mirror  48 . Further, a revolving nosepiece  49  and an objective  50  attached to the revolving nosepiece  49  are arranged on the optical path of the laser beam. The revolving nosepiece  49  is coupled to a focusing mechanism  52  via a supporting member  51  and the position of the revolving nosepiece  49  can be adjusted in the Z-direction by the focusing mechanism  52 . An imaging lens (not shown) is arranged between the objective  50  and the mirror  48  to form an image of a sample M at a detecting system  53 . The imaging lens and a CCD camera arranged in the detecting system  53  constitute an observation optical system.  
         [0074]    A half mirror  54  is arranged on a branch optical path of the half mirror  47 . An illumination optical system  55  of an optical microscope is located on a branch optical path of the half mirror  47 , and an imaging optical system  56  of the optical microscope is positioned on another branch optical path. The illumination optical system  55  of the optical microscope comprises a light source, a filter and the like.  
         [0075]    Of the above components, the laser light source  43 , the focusing mechanism  52 , the detecting system  53 , and the illumination optical system  55  and imaging optical system  56  of the optical microscope are fixed to the frame  42  via dynamic vibration absorber units A 1  to A 5 , respectively. Further, the revolving nosepiece  49  is fixed to the supporting member  51  via a dynamic vibration absorber unit A 6 .  
         [0076]    The laser light source  43 , the revolving nosepiece  49 , the focusing mechanism  52 , the detecting system  53 , and the illumination optical system  55  and imaging optical system  56  of the optical microscope must be arranged such that they vibrate in directions that will not affect the optical microscope. That is, they are supported by the respective dynamic vibration absorber units A 1  to A 6  such that they can vibrate in the directions of the optical paths. The laser light source  43  and the illumination optical system  55  of the optical microscope are supported in the Y-direction, and the revolving nosepiece  49 , the focusing mechanism  52 , the detecting system  53 , and the imaging optical system  56  of the optical microscope are supported in the Z-direction. Although the detecting system  53  is oriented in the Z-direction in the figure, it can be rotated together with the half mirror  44  around the Y-axis, thereby securing its freedom in designing the microscope.  
         [0077]    The dynamic vibration absorber units A 1  to A 5  are passive dynamic vibration absorber units and constructed in the same way as the second embodiment. The damping member  31  converts vibration energy into thermal energy to reduce the vibration of the structure whose vibration should be reduced.  
         [0078]    The dynamic vibration absorber unit A 6  is an active dynamic vibration absorber unit and coupled to a controller  16 . It is designed in the same way as the first embodiment. The vibration sensor  15  detects the vibration of the structure whose vibration should be reduced, and the controller  16  drives the piezoelectric actuator  13  in accordance with the vibration of the structure to vibrate the mass  20  of the dynamic vibration absorber, so that the force of the mass  20  can reduce the vibration of the structure.  
         [0079]    The dynamic vibration absorber units A 1  to A 5  may be active and the dynamic vibration absorber unit A 6  may be passive.  
         [0080]    Now, the vibration reducing operation in the microscope constituted as described above is explained.  
         [0081]    Air vibration, such as wind or sound, causes the microscope to vibrate. Vibration from the floor is transmitted by the frame  42  to produce vibration of the microscope. Further, an inner vibration source, such as the galvanomirrors  45  and  46  or the focusing mechanism  52 , causes vibrations of the frame  42 , the focusing mechanism  52  and the revolving nosepiece  49 . Because of these vibrations, the relative displacement between the objective  50  and the sample M varies to cause noise in an observation image.  
         [0082]    In such a case, the dynamic vibration absorber comprising the revolving nosepiece  49 , the dynamic vibration absorber unit A 6  and the controller  16  operates as follows: When the supporting member  51  vibrates, the vibration sensor signal p outputted from the vibration sensor  15  incorporated in the dynamic vibration absorber unit A 6  varies. In accordance with the variation of the signal p, the controller  16  operates to derive the actuator drive signal s for reducing the vibration of the supporting member  5  and transmits the actuator drive signal s to the piezoelectric actuator  13 . The piezoelectric actuator  13  drives the revolving nosepiece  49  functioning as the mass, and its force is transmitted to the supporting member  51  to reduce the vibration of the supporting member  51 .  
         [0083]    Driving the revolving nosepiece  49  supporting the objective  50  results in the change of the focusing position. However, the dynamic vibration absorber unit A 6  drives the revolving nosepiece  49  in such a manner that the vibration of the supporting member  51  is cancelled by the force due to the vibration of the revolving nosepiece  49 . Specifically, when the supporting member  51  moves to displace the revolving nosepiece  49  away from the focusing position, the dynamic vibration absorber unit A 6  drives the revolving nosepiece  49  so that the revolving nosepiece  49  approaches the focusing position. Thus, by setting the gain in the controller such that the amplitude of vibration of the piezoelectric actuator  13  does not exceed the amplitude of vibration of the supporting member  51 , the revolving nosepiece  49  is driven so as to restrict the change of the focusing position due to the vibration of the supporting member  51 . As a result, the vibration of the supporting member  51  is reduced.  
         [0084]    Further, the laser light source  43 , the focusing mechanism  52 , the detecting system  53 , and the illumination optical system  55  and imaging optical system  56  of the optical microscope serve to reduce the vibration of the frame  42  by means of the vibration reducing function of the respective dynamic vibration absorber units A 1  to A 5 . In the case of the laser light source  43  and the illumination optical system  55  of the optical microscope, the vibration in the Y-direction is reduced. With respect to the revolving nosepiece  49 , the focusing mechanism  52 , the detecting system  53 , and the imaging optical system  56  of the optical microscope, the vibration in the Z-direction is reduced. The detecting system  53  is rotatable about the Y-axis and in accordance with its fixed position, its vibration can be reduced.  
         [0085]    As explained above, in the third embodiment, the laser light source  43 , the focusing mechanism  52 , the detecting system  53 , and the illumination optical system  55  and imaging optical system  56  of the optical microscope are supported by the frame  42  via the respective dynamic vibration absorber units A 1  to A 5 . Further, the revolving nosepiece  49  is supported by the supporting member  51  via the dynamic vibration absorber unit Al. Accordingly, the vibration of the laser light source  43  and the illumination optical system  55  of the optical microscope in the Y-direction can be reduced, and the vibration of the revolving nosepiece  49 ,the focusing mechanism  52 , the detecting system  53 , and the imaging optical system  56  of the optical microscope in the Z-direction can be reduced. In other words, this embodiment can reduce plural modes of vibration.  
       Fourth Embodiment  
       [0086]    With reference to FIG. 10, a fourth embodiment of the present invention is described.  
         [0087]    [0087]FIG. 10 shows the structure of a measuring microscope with an active dynamic vibration absorber.  
         [0088]    The measuring microscope measures the shape of a sample M which has a rough surface. An XY-stage  61  is provided on a base of an L-shaped frame  60 , and the sample M is mounted on the XY stage  61 .  
         [0089]    A Z-stage  62  extending over the XY-stage. 61  is slidably mounted on a vertical portion of the frame  60 : The Z-stage  62  is provided on its upper surface with a displacement measuring optical system  63 , above which there is an observation optical system comprising an ocular tube  64 , an intermediate attachment  65  and a CCD camera  66 . The Z-stage  62  is also provided on its lower surface with a revolving nosepiece  67 , to which an objective  68  is mounted.  
         [0090]    The displacement measuring optical system  63  has a function of measuring a minute displacement of the surface of the sample M in the direction of the Z-axis. The ocular tube  64  is provided with an imaging lens  69  for converging, on the image plane of the CCD camera  66 , parallel rays of an observation light beam L from the objective  68 .  
         [0091]    The-displacement measuring optical system  63 , the ocular tube  64 , the intermediate attachment  65  and the CCD camera  66  are moved in the direction of the optical axis (Z-direction) by driving the Z-stage  62 .  
         [0092]    The displacement measuring optical system has a light source for illuminating the sample M, and a detector for detecting light reflected from the sample M.  
         [0093]    The detector outputs a signal on the basis of quantity of the reflected light. The signal is used for forming the shape of the sample.  
         [0094]    The XY-stage  61  and the Z-stage  62  incorporate respective displacement scales such as an optical scale or a magnetic scale. When the XY-stage  61  and the Z-stage  62  move, the displacement scales detect respective amounts of movement, which are displayed in a displacement display. Thus, by moving the XY-stage  61  and the Z-stage  62  to change the observation position of the sample M, the observer can read the distance between the observation positions from the displacement display.  
         [0095]    In the measuring microscope, when the frame  60  or the Z-stage  62  vibrates, the relative displacement between the objective  68  and the sample M also vibrates so that a vibration component is added to the result of measurement of the sample M. Accordingly, it is necessary to reduce the vibration of the frame  60  or the Z-stage  62  by means of an active dynamic vibration absorber unit  70 .  
         [0096]    The active dynamic vibration absorber unit  70  is arranged between the displacement measuring optical system  63  on the Z-stage  62  and microscope components: the ocular tube  64 , the intermediate attachment  65  and the CCD camera  66 , which constitute an observation optical system functioning as a mass  71  of the active dynamic-vibration absorber.  
         [0097]    The dynamic vibration absorber unit  70  has the same structure as that of the dynamic vibration absorber unit  10  shown in FIG. 3 and its detailed description is omitted. A controller  72  is coupled to the dynamic vibration absorber unit  70 . The vibration sensor signal p outputted from the vibration sensor  15  and representing the vibration of the Z-stage  62  is inputted to the controller  72 . The controller  72  has the following function: in accordance with the vibration of the Z-stage  62 , the controller  72  operates to derive an actuator drive signal s for reducing the vibration of the Z-stage  62  and transmits the actuator drive signal s to the piezoelectric actuator  13  of the dynamic vibration absorber unit  70 .  
         [0098]    Next, the vibration reducing operation in the microscope constituted as described above is explained.  
         [0099]    The Z-stage  62  is vibrated by air vibration (such as wind or sound), vibration from the floor, internal mechanical vibration die to the operation of the microscope, or the like. When the Z-stage  62  vibrates, the relative distance between the XY-stage  61  and the objective  68  varies so that there will be an error in the result of displacement measuring.  
         [0100]    The vibration sensor  15  detects the vibration of the Z-stage  62  and outputs the vibration sensor signal p, which is inputted to the controller  72 . As described above, in accordance with the vibration of the Z-stage  62  represented by the vibration sensor signal p, the controller  72  operates to derive the actuator drive signal s for reducing the vibration of the Z-stage  62  and transmits the actuator drive signal s to the piezoelectric actuator- 13 .  
         [0101]    The piezoelectric actuator  13  vibrates in the Z-direction the mass  71  comprising the ocular tube  64 , the intermediate attachment  65  and the CCD camera  66  so that the force of the mass  71  can reduce the vibration of the Z-stage  62 .  
         [0102]    As described above, in the fourth embodiment, the dynamic vibration absorber unit  70  is arranged between the displacement measuring optical system  63  on the Z-stage  62  and the mass  71  comprising the ocular tube  64 , the intermediate attachment  65  and the CCD camera  66 . In accordance with the vibration of the Z-stage  62 , the mass  71  is vibrated to reduce the vibration of the Z-stage  62 . As a result, displacement due to the vibration can be prevented from being added to the measurement of the sample M.  
         [0103]    Further, just like in the first embodiment, the measuring microscope of this embodiment can be provided with the dynamic vibration absorber unit  70  without changing the structure of the microscope. Thus, the dynamic vibration absorber unit  70  can be introduced into the microscope system without restriction of its setting place and without increasing the weight of the microscope. It is also possible to arrange the dynamic vibration absorber unit  70 , for example, between the ocular tube  64  and the intermediate attachment  65 or between the intermediate attachment  65  and the CCD camera  66  so as to reduce the vibration of the intermediate attachment  65  or the CCD camera  66 .  
         [0104]    Moreover, the dynamic vibration absorber unit  70  does not affect the observation image since the observation light beam L passing through the dynamic vibration absorber unit  10  between the Z-stage  62  and the ocular tube  64  comprises parallel rays.  
       Fifth Embodiment  
       [0105]    Referring to FIG. 11, a fifth embodiment of the present invention is described.  
         [0106]    This embodiment relates to a confocal microscope. Such a confocal microscope is described in, for example, U.S. Pat. No. 4,927,254 and U.S. Pat. No. 5,067,805, these contents of which are hereby incorporated by reference.  
         [0107]    [0107]FIG. 11 shows the structure of a confocal microscope with an active dynamic vibration absorber.  
         [0108]    A frame  80  of the confocal microscope is provided with a sample stage  81 , on which a sample M is mounted.  
         [0109]    Over the sample stage  81 , an arm  82  protrudes from the frame  80 . Above the arm  82 , there are an ocular tube  83 , a confocal unit  84 , an intermediate attachment  85  and a CCD camera  86  that constitute an observation optical system. Mounted on a lower surface of the arm  82  is a revolving nosepiece  87  with an objective  88 .  
         [0110]    The intermediate attachment  85  is provided with an imaging lens  89  for converging, on an image plane  86   a  of the CCD camera  86 , parallel rays of an observation light beam L from the objective  88 .  
         [0111]    The confocal unit  84  comprises a disc  90  having randomly arranged pinholes, and a motor  91  for rotating the disc  90 .  
         [0112]    An illumination optical system  92  is attached to the confocal unit  84 . Illumination light emitted from the illumination optical system  92  is reflected by a mirror  93  in the confocal unit  84  to illuminate the sample M.  
         [0113]    In the confocal microscope, when the rotating disc  90  vibrates the arm  82  of the frame  80 , the relative displacement between the objective  88  and the sample M varies so that an observation image of the sample M will be blurred. Further, the confocal microscope is also used for three-dimensional measuring since it has a high resolving power. However, such vibration will substantially deteriorate its performance. Accordingly, it is necessary to use an active dynamic vibration absorber unit  94  for reducing the vibration of the frame  80 . The dynamic vibration absorber unit  94  is arranged between the arm  82  of the frame  80  and microscope components: the ocular tube  83 , the confocal unit  84 , the intermediate attachment  85  and the CCD camera  86  that constitute the observation optical system functioning a mass  95  of the active-dynamic vibration absorber.  
         [0114]    The dynamic vibration absorber unit  94  has the same structure as that of the dynamic vibration absorber unit  10  shown in FIG. 3 and its detailed description is omitted. A controller  96  is coupled to the dynamic vibration absorber unit  94 . The vibration sensor signal p outputted from the vibration sensor  15  and representing the vibration of the frame  80  is inputted to the controller  96 . The controller  96  has the following function: in accordance with the vibration of the frame  80 , the controller  96  operates to derive an actuator drive signal s for reducing the vibration of the frame  80  and transmits the actuator drive signal s to the piezoelectric actuator  13  of the dynamic vibration absorber unit  94 .  
         [0115]    Next, the vibration reducing operation in the microscope constituted as described above is explained.  
         [0116]    The frame  80  is vibrated by air vibration (such as wind or sound), vibration from the floor, internal mechanical vibration due to the operation of the confocal microscope, vibration due to the rotating disc  90  and the motor  91 , or the like. When the frame  80  vibrates, the relative distance between the XY-stage  61  and the objective  68  varies so that the observation image will be blurred.  
         [0117]    The vibration sensor  15  detects the vibration of the frame  80  and outputs the vibration sensor signal p, which is inputted to the controller  96 . As described above, in accordance with the vibration of the frame  80  represented by the vibration sensor signal p, the controller  96  operates to derive the actuator drive signal s for reducing the vibration of the frame  80  and transmits the actuator drive signal s to the piezoelectric actuator  13 .  
         [0118]    The piezoelectric actuator  13  vibrates in the Z-direction the mass  95  comprising the ocular tube  83 , the confocal unit  84 , the intermediate attachment  85  and the CCD camera  86  so that the force of the mass  95  can reduce the vibration of the, frame  80 .  
         [0119]    As described above, in the fifth embodiment, the dynamic vibration absorber unit  94  is arranged between the frame  80  and the mass  95  comprising the ocular tube  83 , the confocal unit  84 , the intermediate attachment  85  and the CCD camera  86 . In accordance with the vibration of the frame  80 , the mass  95  is vibrated to reduce the vibration of the frame  80 . As a result, it is possible to reduce a blur and axial displacement of an observation image of the sample M so that a good confocal image can be observed or three-dimensional measuring can be made.