Microscope with supporting unit that fixedly supports the imaging unit and movably supports the objective lens

A microscope, which moves an objective lens along an observation optical axis with respect to a specimen, includes an imaging unit and a supporting unit. The imaging unit has an imaging lens, which is arranged on the observation optical axis and forms an observation image of the specimen, and an imaging element, which is arranged on the observation optical axis and takes the observation image, and is optically connected to the objective lens by a parallel light flux. The supporting unit fixedly supports the imaging unit, and movably supports the objective lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2009-111399, filed on Apr. 30, 2009 and Japanese Patent Application No. 2009-151475, filed on Jun. 25, 2009, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microscope that moves an objective lens along an observation optical axis with respect to a specimen.

2. Description of the Related Art

Conventionally, there is a microscope that makes an observation of a specimen by moving an objective lens along an observation optical axis with respect to the specimen and displaying an observation image on a liquid-crystal monitor or the like. For example, a microscope that makes an observation of a specimen by moving an objective lens and a camera together as a unit is disclosed in Japanese Laid-open Patent Publication No. 2004-348089 and Japanese Laid-open Patent Publication No. 2006-337471.

SUMMARY OF THE INVENTION

A microscope according to an aspect of the present invention includes an objective lens; an imaging unit that has an imaging lens for forming an observation image of a specimen and an imaging element for taking the observation image, the imaging lens and the imaging element being arranged on an observation optical axis, and the imaging unit being optically connected to the objective lens by a parallel light flux; and a supporting unit that fixedly supports the imaging unit, and movably supports the objective lens.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a side view illustrating a configuration of a microscope1according to a first embodiment of the present invention. As shown inFIG. 1, the microscope1has a base unit20, a stage30, a supporting unit40, a rotary holding unit50, a focusing unit60, and an imaging unit70.

The base unit20is a mount part supporting the entire microscope1. The stage30is supported by the base unit20, and has a specimen table30aon a top surface thereof. The specimen table30ais a table on which a specimen S is put. The stage30is connected to a stage handle30bby a moving mechanism (not shown), and makes a rotational movement in an X-Y direction shown the drawing and around an observation optical axis L by the turning operation of the stage handle30b.

The supporting unit40has a strut unit41, an L-shaped supporting unit42, and a focusing-unit moving mechanism43. The strut unit41is a right prism-like strut, and is rotatably held by the base unit20via the rotary holding unit50so that the strut unit41can rotate around a horizontal axis line P. Furthermore, the strut unit41is held by the base unit20so that a side surface of which is parallel to a direction of the observation optical axis L. The L-shaped supporting unit42is a member that a right prism is bent into an L shape, and has a body portion42ajoined to the strut unit41along the side surface of the strut unit41and an arm portion42bextending from the upper part of the body portion42ain a horizontal direction. The L-shaped supporting unit42is joined to the strut unit41so that the body portion42ais along the side surface of the strut unit41.

The focusing-unit moving mechanism43has a focus handle43aand a lift mechanism with a pinion and a rack (not shown) to which the focus handle43ais connected. By the operation of the focus handle43a, the focusing-unit moving mechanism43can move an enclosure61to be described below along the body portion42a. In other words, the focusing-unit moving mechanism43can move the enclosure61in a direction parallel to the observation optical axis L. The focusing-unit moving mechanism43having the lift mechanism with the pinion and the rack is described as an example; however, the configuration of the focusing-unit moving mechanism43is not limited to this, and any other configuration can be employed as long as the focusing-unit moving mechanism43can move the enclosure61in the direction parallel to the observation optical axis L. For example, the focusing-unit moving mechanism43can have a lift mechanism with a ball screw.

The rotary holding unit50has a rotating mechanism50aand a strut fixing knob50b. The strut fixing knob50bis connected to the rotating mechanism50a, for example, via a screw unit (not shown), and fixes the strut unit41at a desired rotational position around the horizontal axis line P. Specifically, the rotary holding unit50fixes the strut unit41at the desired rotational position with the strut unit41pressed against the base unit20by tightening up the strut fixing knob50b, and turns the supporting unit40by loosening the strut fixing knob50b. Namely, the rotary holding unit50holds a lower end of the supporting unit40or near the lower end so that the supporting unit40can turn.

The focusing unit60has the enclosure61formed into a box, an objective lens62, an epi-illumination projecting unit63, and a magnification converting unit64. The enclosure61is movably supported by the body portion42avia the focusing-unit moving mechanism43so that the enclosure61can move in the direction parallel to the observation optical axis L.

The objective lens62is attached to the lower part of the enclosure61, and moves with respect to the specimen S along the observation optical axis L with movement of the enclosure61.

The epi-illumination projecting unit63is provided in the enclosure61, and lets illumination light fall on the objective lens62. The epi-illumination projecting unit63has a light source63a, an optical-path splitting element63b, condenser lenses63c,63d, and63e, an aperture stop63f, and a field stop63g.

The light source63aemits illumination light in a range of wavelengths from a visible region to an ultraviolet region with a white LED or the like. As the optical-path splitting element63b, a half mirror, a dichroic mirror, or the like is used. The optical-path splitting element63bis arranged on the observation optical axis L between the magnification converting unit64and the objective lens62, reflects the illumination light emitted from the light source63ato the side of the objective lens62, and lets the observation light reflected from the specimen S therethrough.

The condenser lenses63c,63d, and63eare arranged between the light source63aand the optical-path splitting element63b. The condenser lens63cconcentrates the illumination light emitted from the light source63ainto a parallel light. The condenser lens63dfocuses the illumination light concentrated into the parallel light by the condenser lens63cinto a first light source image at the position of the aperture stop63f. The condenser lens63efocuses the illumination light entering via the field stop63gfrom the first light source image into a second light source image at the back focal position of the objective lens62on a reflection optical path of the optical-path splitting element63b. The configuration of the epi-illumination projecting unit63is not limited to that is described above; any other configuration can be employed as long as the epi-illumination projecting unit63lets illumination light fall on the objective lens62so that the specimen S is irradiated with parallel light via the objective lens62.

The magnification converting unit64is provided in the enclosure61, and has two zoom lenses64aand64barranged on the observation optical axis L. The magnification converting unit64moves any of the zoom lenses64aand64balong the observation optical axis L, thereby changing the observation magnification. The magnification converting unit64having two zoom lenses is described as an example; however, the configuration of the magnification converting unit64is not limited to this, and any other configuration can be employed as long as the magnification converting unit64has at least two zoom lenses and can convert the observation magnification.

The imaging unit70is fixed to the arm portion42b, and supported by the arm portion42b. The imaging unit70has a tube70a, an imaging lens70b, and an imaging element70c. The imaging lens70bis arranged on the observation optical axis L in the tube70a, and focuses a parallel light flux from the side of the objective lens62into an observation image of the specimen S. As the imaging element70c, a CCD camera or the like is used. The imaging element70cis arranged on the observation optical axis L in the tube70a. The imaging element70ctakes the observation image of the specimen S imaged by the imaging lens70b, and outputs the observation image of the specimen S to a display unit (not shown), such as a liquid-crystal monitor, provided to the outside via a cable70dor the like so that the observation image of the specimen S is displayed on the display unit. In this manner, the imaging lens70band the imaging element70care arranged on the observation optical axis L, whereby the imaging unit70is optically connected to the objective lens62by the parallel light flux.

In this microscope1, the illumination light emitted from the light source63ais concentrated into parallel light by the condenser lens63c, and focused into a first light source image at the position of the aperture stop63fby the condenser lens63d. After that, the illumination light enters the condenser lens63evia the field stop63g, and is reflected to the side of the objective lens62by the optical-path splitting element63b, and then falls on the objective lens62along the observation optical axis L. After that, the illumination light is focused into a second light source image at the back focal position of the objective lens62, and after the illumination light is concentrated into approximately-parallel light by passing through the objective lens62, the specimen S is irradiated with the illumination light. The reflected light from the specimen S passes, as observation light, through the objective lens62and the optical-path splitting element63b, and enters the imaging lens70bvia the zoom lenses64aand64b. Then, an observation image of the specimen S is focused on the imaging element70cby the imaging lens70b.

Subsequently, how to operate the microscope1according to the first embodiment is explained. First, an operator loosens the strut fixing knob50b, and turns the supporting unit40to a desired position. After that, the operator fixes the supporting unit40by tightening up the strut fixing knob50b. As a result, the supporting unit40is fixed in an upright state (FIG. 2A) or a tilted state in which the supporting unit40is tilted at a desired angle θ around the horizontal axis line P (FIG. 2B). After that, the operator puts a specimen S on the specimen table30a, and moves the specimen S by turning the stage handle30bto make a rough position (focus) adjustment of the objective lens62with respect to the specimen S.

After that, the operator moves the enclosure61by turning the focus handle43a. Namely, the operator focuses the microscope1on the specimen S by moving the objective lens62along the observation optical axis L. At this time, in a state where the imaging unit70is fixed to the arm portion42b, the objective lens62is moved. Furthermore, since the epi-illumination projecting unit63is provided in the enclosure61, the epi-illumination projecting unit63moves together with the movement of the objective lens62along the observation optical axis L.

In the microscope1according to the first embodiment, the supporting unit40fixedly supports the imaging unit70and movably supports the objective lens62, so the focusing unit60including the objective lens62can be moved for focusing with the imaging unit70fixed. At this time, although a positional relation between the imaging unit70and the objective lens62varies, the imaging unit70is optically connected to the objective lens62by a parallel light flux, so there is no optical impact. Consequently, the weight balance of the microscope1at the time of movement of the objective lens62is stabilized as compared with a case where the objective lens62and the imaging unit70are moved together as a unit. Furthermore, even when the objective lens62is moved along the observation optical axis L in a state where the supporting unit40is tilted at the angle θ as shown inFIG. 2B, there is little change in the position of the gravity center of the microscope1, so the weight balance of the microscope1is stabilized. Consequently, there is no need to employ a device configuration tolerant of a change in weight balance as in the case where the objective lens62and the imaging unit70are moved together as a unit, and thus it is possible to construct a microscope apparatus in a simple configuration.

Moreover, in the microscope1according to the first embodiment, the epi-illumination projecting unit63moves together with the movement of the objective lens62along the observation optical axis L, so even when the objective lens62is moved, a light source image can be focused at the back focal position of the objective lens62. Consequently, it is possible to provide an optimum illumination with respect to the specimen S.

Subsequently, a first variation of the microscope1according to the first embodiment is explained.FIG. 3is a side view of a microscope100according to the first variation of the microscope1shown inFIG. 1. In this first variation, a focusing mechanism110of the microscope100has a motor M for generating power for movement of the enclosure61. The microscope100moves the enclosure61by driving the motor M. For example, a rotation axis is connected to the rotation center of a pinion of the focusing mechanism110, and the connected rotation axis is rotated by the motor M. Consequently, the operator does not have to perform the focus operation by rotating the focus handle43a, and thus the burden on the operator can be reduced.

Subsequently, a second variation of the microscope1according to the first embodiment is explained.FIG. 4is a side view of a microscope200according to the second variation of the microscope1shown inFIG. 1. In this second variation, an imaging unit210of the microscope200has an optical-path changing element210a, such as a total reflection mirror, which changes an optical path of an observation light entering the imaging lens70bin the horizontal direction. The imaging lens70band the imaging element70care arranged on an observation optical axis of the observation light of which the optical path is changed in the horizontal direction by the optical-path changing element210a. Consequently, the height of the microscope can be reduced, and the gravity center can be kept low; thus, the weight balance at the time of movement of the objective lens62is further stabilized.

Subsequently, a third variation of the microscope1according to the first embodiment is explained.FIG. 5is a side view of a microscope300according to the third variation of the microscope1shown inFIG. 1. In this third variation, a focusing unit310of the microscope300has a revolving nosepiece311. The revolving nosepiece311holds a plurality of objective lenses62, and sets desired one of the plurality of objective lenses62on the observation optical axis L. In this manner, the revolving nosepiece311can be added to the focusing unit310because the weight balance at the time of movement of the objective lens62is stabilized as the objective lens62can be moved for focusing with the imaging unit70fixed. This makes it possible to easily switch among the objective lenses62of different magnifications from one another and set one of them on the observation optical axis L.

FIG. 6is an enlarged view of a main portion of the revolving nosepiece311shown inFIG. 5. The revolving nosepiece311has a rotary member311a, a rotation axis portion311b, and a click mechanism311c. The rotary member311aremovably holds the plurality of objective lenses62. The rotation axis portion311brotatably holds the rotary member311aso that the rotary member311acan rotate around a rotation axis line C. The click mechanism311cassists in positioning and arranging the desired objective lens62out of the objective lenses62held by the rotary member311aon the observation optical axis L. The revolving nosepiece311sets the desired objective lens62on the observation optical axis L by rotating the rotary member311aand positioning the click mechanism311c. The configuration of the revolving nosepiece311is not limited to that is shown inFIG. 5, and any other configuration can be employed as long as the revolving nosepiece311can hold a plurality of objective lenses62and set desired one of the plurality of objective lenses62on the observation optical axis L. It is preferable that a lightweight revolving nosepiece be used as the revolving nosepiece311.

In the first embodiment, it is described that the epi-illumination projecting unit63and the magnification converting unit64are provided in the enclosure61, and the enclosure61is movably supported by the supporting unit40; however, the present invention is not limited to this configuration, and any other configuration can be employed as long as the imaging unit70is fixedly supported by the supporting unit40and the objective lens62is movably supported by the supporting unit40. For example, out of the epi-illumination projecting unit63and the magnification converting unit64, only the epi-illumination projecting unit63can be provided in the enclosure61.

Furthermore, in the first embodiment, it is described that the strut unit41is a right prism-like strut, and the L-shaped supporting unit42is a member that a right prism is bent into an L shape; the shapes of the strut unit41and the L-shaped supporting unit42are not limited thereto, and the strut unit41and the L-shaped supporting unit42can have any other shapes as long as the imaging unit70is fixedly supported on the observation optical axis L by the supporting unit40and the enclosure61is movably supported by the supporting unit40via the focusing-unit moving mechanism43so that the enclosure61can move in the direction parallel to the observation optical axis L, i.e., as long as the imaging unit70is fixedly supported on the observation optical axis L by the supporting unit40and the objective lens62is movably supported by the supporting unit40so that the objective lens62can move along the observation optical axis L.

Moreover, in the first embodiment, it is described that the supporting unit40is rotatably held by the base unit20via the rotary holding unit50so that the supporting unit40can rotate around the horizontal axis line P; however, the present invention is not limited to this configuration, and the supporting unit40can be fixed to the base unit20in an upright state with the supporting unit40prevented from rotating.

Second to fourth embodiments of the microscope according to the present invention are explained in detail below with reference to the drawings. In what follows, the X-axis direction in the drawings denotes a horizontal direction of the microscope, the Y-axis direction in the drawings denotes a front-back direction of the microscope, and the Z-axis direction in the drawings denotes a vertical direction of the microscope.

FIGS. 7 and 8show a microscope according to the second embodiment of the present invention.FIG. 7shows the microscope in a state where a focusing unit is located on the upper side, andFIG. 8shows the microscope in a state where the focusing unit is moved on the lower side. A microscope501has a base unit502, a stage503, and a strut507. The base unit502is a part directly placed in a location on which the microscope501is put, such as on the desk, and is mounting for supporting the entire microscope501.

The stage503is mounted on top of the base unit502, and includes a specimen putting surface503aon the top face thereof. On the specimen putting surface503a, a specimen A, an object to be observed, is put. The stage503can move in directions of the back and forth and the right and left of the microscope501and rotate around the observation optical axis L by the operation of a stage handle503bmounted on the base unit502.

The strut507is provided on the back side face of the stage503on top of the base unit502in a standing manner. On the front face of the strut507, a focusing support unit506is mounted. On the front face of the focusing support unit506, a focusing unit505is movably mounted so that the focusing unit505can move up and down via a focusing-unit moving mechanism510with respect to the focusing support unit506. The focusing-unit moving mechanism510is a mechanism for moving the focusing unit505with respect to the focusing support unit506, and is a publicly-known mechanism, such as a mechanism with a rack and a pinion or a mechanism with a ball screw. In the focusing support unit506, a focus handle506afor moving the focusing unit505is mounted. The focusing-unit moving mechanism510can be driven by an electric motor M. On the upper side of the focusing support unit506, an arm508is formed to extend from the back face side to the front face side of the microscope501so as to project upward above the focusing unit505. At a leading end of the arm508in a direction of projection, a tube509formed into a cylinder extending in the vertical direction is mounted. In the tube509, an observing unit504is provided.

The focusing unit505has an illuminating unit512, a magnification converting unit513, and an objective lens514. The objective lens514is provided so as to project downward from the focusing unit505. The illuminating unit512has an illumination light source521, illumination lenses522, and an optical-path splitting element523. The illumination light source521is composed of a white LED, and mounted around the observation optical axis L toward the observation optical axis L. The illumination light source521is supplied with power from a power supply (not shown) housed in the focusing unit505. The optical-path splitting element523is composed of a half mirror, and arranged on the observation optical axis L. The optical-path splitting element523reflects light from the illumination light source521to the side of the specimen A, and lets the reflected light from the specimen therethrough. The illumination lenses522are mounted between the illumination light source521and the optical-path splitting element523.

The magnification converting unit513includes at least two zoom lenses524aand524b. The zoom lenses524aand524bare connected to a motor (not shown), and can be moved along the observation optical axis L by the motor. The observation magnification is changed by movement of the zoom lenses524aand524b.

The observing unit504has an imaging lens525and an imaging element526. The imaging element526is composed of a CCD. The imaging element526is connected to a cable527, and an observation image is displayed on a monitor (not shown). The observing unit504and the focusing unit505are optically connected by a parallel light flux. Namely, the reflected light from the specimen A is concentrated into a parallel light flux when the reflected light exits from the focusing unit505, and the parallel light flux enters the imaging lens525of the observing unit504. The focusing unit505is moved along the observation optical axis L by the focusing-unit moving mechanism510. The focusing unit505is moved independently of the observing unit504.

On the observation optical axis L, in order from bottom to top, the specimen A, the objective lens514, the optical-path splitting element523, the zoom lenses524aand524b, the imaging lens525, and the imaging element526are arranged. The illumination light emitted from the illumination light source521is reflected by the optical-path splitting element523, and turned toward the specimen A, and then falls on the specimen A along the observation optical axis L. After that, the illumination light passes through the objective lens514, and is focused and irradiated to the specimen A. The reflected light from the specimen A passes through the objective lens514and the optical-path splitting element523, and enters the imaging lens525via the zoom lenses524aand524b. Then, the reflected light is focused into an image on the imaging element526by the imaging lens525.

The focusing operation of the microscope501is explained. A specimen A is put on the stage503, and a rough focus adjustment is performed by turning the stage handle503b. A fine focus adjustment is performed by turning the focus handle506ato move the focusing unit505along the observation optical axis L with respect to the focusing support unit506as shown inFIGS. 7 and 8. Namely, the focusing unit505is moved up and down along the observation optical axis L to adjust so that a focal plane (a front focal position) of the objective lens514is located on the specimen A. Furthermore, the magnification (the observation magnification) of an observation optical system can be changed by moving the zoom lenses524aand524bof the magnification converting unit513along the observation optical axis L by driving a motor (not shown).

Since the microscope501configured as described above achieves an epi-illumination of the same axis as the observation optical axis L even when the focusing unit505is moved for focusing in a direction away from the specimen A, the reflected light from the specimen A reliably enters the objective lens514. Namely, a decrease in amount of the reflected light from the specimen A is prevented, and it is possible to observe the specimen properly. Furthermore, in the microscope501, since the focusing unit505is moved for focusing independently of the observing unit504, a capability required for the focusing operation can be reduced as compared with a microscope in which a focusing unit and an observing unit move for focusing together as a unit, and thus the burden of the focusing operation on an operator can be reduced. If the focusing unit505is moved by an electric motor M, the burden of the focusing operation on the operator can be further reduced, and the operability is improved.

FIG. 9is a side view illustrating a microscope according to the third embodiment of the present invention. In what follows, portions identical to those explained in the second embodiment are denoted by the same reference numerals, and the description of the portions is omitted.

A focusing support unit531included in a microscope530according to the third embodiment is, in the same manner as the focusing support unit506in the second embodiment, mounted on the front face of the strut507. The focusing unit505is movably mounted on the front face of the focusing support unit531via the focusing-unit moving mechanism510so that the focusing unit505can move up and down with respect to the focusing support unit531. On the upper side of the focusing support unit531, an arm531ais formed to extend from the back face side to the front face side of the microscope530so as to project upward above the focusing unit505.

In the microscope530according to the third embodiment, an observing unit532is included in the arm531a. The observing unit532has an optical-path changing element533, the imaging lens525, and the imaging element526. The optical-path changing element533changes an optical path of a parallel light flux, and is provided on the side of a leading end of the arm531ain a direction of projection. The optical-path changing element533is a folding mirror. The imaging lens525is mounted on the back face side of the microscope530than the optical-path changing element533, and the imaging element526is mounted on the back face side of the microscope530than the imaging lens525.

The optical-path changing element533is arranged on the observation optical axis L, and the reflected light (a parallel light flux) from the specimen A, which has exited the focusing unit505and entered the observing unit532, enters the optical-path changing element533. The reflected light from the specimen A is reflected by the optical-path changing element533, enters the imaging lens525, and is focused into an image on the imaging element526. In this manner, the observing unit532and the focusing unit505are optically connected to each other by the parallel light flux.

The focusing unit505is moved along the observation optical axis L by the focusing-unit moving mechanism510. The focusing unit505is moved independently of the observing unit532.

The focusing operation of the microscope530is performed in the same manner as in the second embodiment. Since configurations of main parts of the microscope530are identical to those of the microscope501according to the second embodiment, the microscope530produces the same effect as the microscope501according to the second embodiment. Furthermore, as the microscope530has the optical-path changing element533, the imaging element526and the imaging lens525are mounted to be aligned not in the vertical direction of the microscope530but in the front-back direction of the microscope530, so the height of the entire microscope530can be reduced.

FIG. 10is a side view illustrating a microscope according to the fourth embodiment, andFIG. 11is an enlarged view of a revolving nosepiece portion of the microscope. In what follows, portions identical to those explained in the second embodiment are denoted by the same reference numerals, and the description of the portions is omitted.

In a microscope540according to the fourth embodiment, a focusing unit541includes a revolving nosepiece542. The focusing unit541is movably mounted on the front face of the focusing support unit506so that the focusing unit541can move up and down via the focusing-unit moving mechanism510with respect to the focusing support unit506. The focusing unit541is moved along the observation optical axis L independently of the observing unit504by the focusing-unit moving mechanism510. The focusing-unit moving mechanism510is a publicly-known mechanism, such as a mechanism with a rack and a pinion or a mechanism with a ball screw. The focusing unit541has an enclosure548formed into a box, and the illuminating unit512and the magnification converting unit513are provided in the enclosure548. The enclosure548has a bottom plate and a side wall548astanding around the bottom plate.

The revolving nosepiece542includes a supporting body543, a revolving-nosepiece rotary member544, a click mechanism545, and objective lenses546and547. The supporting body543is composed of the bottom plate of the enclosure548, which is formed into a substantially flat plate, and a through-hole551is formed on the center part of the supporting body543. On the upper part of the through-hole551, a spot-faced portion552is formed. The spot-faced portion552is formed so that the upper part of the through-hole551is opened wider than the other part and the opening of the through-hole551is circumferentially stepped. On the spot-faced portion552, a ring-shaped friction reducing member553is provided.

The revolving-nosepiece rotary member544is formed into a plate, and a through-hole555is formed on the center of the revolving-nosepiece rotary member544. The revolving-nosepiece rotary member544has a rotating shaft554, which is the central axis of rotation of the revolving-nosepiece rotary member544. The rotating shaft554is formed into a rod, and one end of the rotating shaft554in a length direction is a head portion554a, the other end is a screw portion554b, and a portion between the head portion554aand the screw portion554bis a body portion554c. The head portion554ais formed to be thicker than the body portion554c, and the body portion554cis formed to be thicker than the screw portion554b. The screw portion554bis formed into a screw by screw thread cutting.

The screw portion554bis fitted into the through-hole555of the revolving-nosepiece rotary member544. A tip of the screw portion554bprojects downward from the through-hole555, a projecting portion of the screw portion554bis fastened by a nut556. The rotating shaft554is fixed to the revolving-nosepiece rotary member544so that the revolving-nosepiece rotary member544is held by a circular bottom surface of the body portion554cof the rotating shaft554and the nut556.

The body portion554cof the rotating shaft554is fitted into the through-hole551of the supporting body543, and the head portion554aprojects upward from the supporting body543. A circular bottom surface of the head portion554ais in contact with the spot-faced portion552and supported by the supporting body543.

In this manner, the revolving-nosepiece rotary member544is rotatably supported by the supporting body543. The objective lenses546and547of different magnifications from each other, which are arranged across the rotating shaft554, are removably mounted on the revolving-nosepiece rotary member544with screws. By rotating the revolving-nosepiece rotary member544, any of the objective lenses546and547to be arranged on the observation optical axis L can be switched.

The click mechanism545is composed of a leaf spring545a, a bearing545b, and click grooves545cand545d. The one end side of the leaf spring545ais fixed to the lower part of the side wall548a, and the other end side is provided with the bearing545b. The bearing545bis formed in a cylindrical shape, and rotatably supported by the leaf spring545a. The click grooves545cand545dare formed to be located at the periphery of the undersurface of the revolving-nosepiece rotary member544, and each formed in the shape of a groove into which the bearing545bfalls. When the revolving-nosepiece rotary member544is rotated, the bearing545bfalls into the click groove545cor the click groove545d, thereby positioning the objective lenses546and547. The click groove545ccorresponds to the objective lens547, and the click groove545dcorresponds to the objective lens546. Namely, in a case where the objective lens546is used for observation, when the objective lens546is arranged on the observation optical axis L, the bearing545bfalls into the click groove545d. On the other hand, in a case where the objective lens547is used for observation, when the objective lens547is arranged on the observation optical axis L, the bearing545bfalls into the click groove545c, thereby positioning the objective lens.

The operation for switching between the objective lenses546and547is explained. To switch to the objective lens547in a state where the objective lens546is arranged on the observation optical axis L, the objective lens546is held and slowly rotated around the rotating shaft554by 180 degrees. As a result, the bearing545bcomes out from the click groove545d, and the bearing545bthen falls into the other click groove545c. In this way, switching between the objective lenses546and547is made. The focusing operation is performed in the same manner as in the second embodiment.

Since configurations of main parts of the microscope540are identical to those of the microscope501according to the second embodiment, the microscope540produces the same effect as the microscope501according to the second embodiment. Furthermore, as the microscope540includes the revolving nosepiece542, an operator can switch to an objective lens to be used without removing a previously-used objective lens to replacing it to the objective lens to be used, so the work burden can be reduced. Other publicly-known means with a bearing can be used as the rotation mechanism of the revolving nosepiece.

In the second to fourth embodiments described above, the imaging element is mounted as an observing means in the observing unit; alternatively, an eyepiece for making a visual observation can be mounted as the observing means. Furthermore, as the observing means, both the imaging element and the eyepiece can be mounted so as to switch between the monitor observation and the visual observation.