U.S. patent application number 13/644930 was filed with the patent office on 2013-05-23 for microscope apparatus.
This patent application is currently assigned to Nikon Corporation. The applicant listed for this patent is Nikon Corporation. Invention is credited to Masahiro MIZUTA.
Application Number | 20130128344 13/644930 |
Document ID | / |
Family ID | 42268811 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130128344 |
Kind Code |
A1 |
MIZUTA; Masahiro |
May 23, 2013 |
MICROSCOPE APPARATUS
Abstract
A microscope apparatus configured to enlarge entrance pupils
while maintaining the rotational symmetry of optical systems of a
plurality of optical paths after ejection of light from an
objective lens to bring out the performance of the objective lens.
A microscope apparatus includes an objective lens having a function
of collecting light from the object; and optical paths in which all
lens groups are rotational symmetric systems and through which
light exited from the objective lens passes, wherein when a sum of
maximum diameters of entrance pupils of optical systems forming any
two of the optical paths is set as .SIGMA.Di, and an axial luminous
flux diameter determined from a maximum aperture angle .alpha. and
a focal distance f of the objective lens is set as Dobj, a
condition of the following expression is satisfied,
.SIGMA.Di>Dobj where Dobj=2fsin .alpha..
Inventors: |
MIZUTA; Masahiro;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nikon Corporation; |
Tokyo |
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JP |
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|
Assignee: |
Nikon Corporation
Tokyo
JP
|
Family ID: |
42268811 |
Appl. No.: |
13/644930 |
Filed: |
October 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13156644 |
Jun 9, 2011 |
8305684 |
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13644930 |
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PCT/JP2009/070943 |
Dec 16, 2009 |
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13156644 |
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Current U.S.
Class: |
359/376 |
Current CPC
Class: |
G02B 21/22 20130101 |
Class at
Publication: |
359/376 |
International
Class: |
G02B 21/22 20060101
G02B021/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2008 |
JP |
2008-323463 |
Sep 18, 2009 |
JP |
2009-216524 |
Claims
1. A microscope apparatus comprising, in order from an object side:
an objective lens having a function of collecting light from the
object; and two or more optical paths through which the light
exited from the objective lens passes, wherein when maximum
diameters of entrance pupils of optical systems forming any two of
the optical paths among the two or more optical paths are set as
Dep1 and Dep2, a sum of the maximum diameters of the two entrance
pupils is set as .SIGMA.Di'', a distance between centers of the two
entrance pupils is set as Dx, and an axial luminous flux diameter
determined from a maximum aperture angle .alpha. and a focal
distance f of the objective lens is set as Dobj, a condition of the
following expression is satisfied, .SIGMA.Di''>Dobj
Dx.gtoreq.Dep1 Dep1=Dep2 where Dobj=2fsin .alpha..
2. The microscope apparatus according to claim 1, wherein the
number of the optical paths is 2.
3. The microscope apparatus according to claim 1, wherein the
number of the optical paths is 3.
4. The microscope apparatus according to claim 1, wherein the two
or more optical paths are movable relative to the optical axis of
the objective lens while a positional relationship of each other is
maintained.
5. The microscope apparatus according to claim 1, wherein at least
one of the two or more optical paths comprises: afocal variable
power optical systems that eject light, which is ejected
substantially parallel to the optical axis of the objective lens
from the objective lens, as a plurality of substantially parallel
lights; and an imaging lens that collects the substantially
parallel lights ejected from the afocal variable power optical
system, and at least one of the afocal variable power optical
systems comprises, at at least part of a section for changing the
magnification from a high-power end state to a low-power end state,
at least two lens groups that move to include components in a
direction orthogonal to the optical axis of the objective lens.
Description
TECHNICAL FIELD
[0001] The present invention relates to a microscope apparatus.
BACKGROUND ART
[0002] A stereoscopic microscope as an example of a microscope
apparatus can stereoscopically observe an object with protrusions
and recesses as if the object is viewed by both eyes. Therefore, a
distance relationship between a tool, such as tweezers, and an
object can be easily recognized in an operation with the
microscope. Thus, the stereoscopic microscope is particularly
effective in a field that requires precise procedures, such as
precision machinery industry and anatomy or surgery of living
organisms. In such a stereoscopic microscope, an optical system
that guides the luminous flux entering left and right eyes is at
least partially separated to cause the optical axes to intersect
over the surface of the object to obtain a parallax for
stereoscopically observing the object. Enlarged images of the
object viewed from different directions are created, and the images
are observed through an eyepiece to stereoscopically view a minute
object. An example of a typical configuration of the stereoscopic
microscope includes a parallel stereoscopic microscope. The
parallel stereoscopic microscope (parallel single-objective
binocular microscope) includes one objective lens and two
observation optical systems for right and left eyes arranged
parallel to the optical axis of the objective lens. In this case,
the objective lens that has brought the focus position in line with
the surface of the object plays a role of guiding the parallel
luminous flux to the following variable power lens groups for left
and right eyes. The parallel luminous flux ejected from the
objective lens is divided into two optical paths (variable power
lens groups or observation optical systems) and is separately
delivered to the left and right eyes.
[0003] In the parallel stereoscopic microscope, the observation
optical system divides the light collected by the objective lens
into two optical paths, and the effective diameter is about half
the objective lens. Accordingly, the resolving power is also
approximately halved, and the optical performance of the objective
lens cannot be fully utilized. Therefore, a microscope apparatus is
developed, in which incident effective diameters of left and right
observation optical systems are differentiated to improve the
resolving power of only an optical system of one side to acquire a
high-resolution image (for example, see Patent Literature 1).
CITATION LIST
Patent Literature
[Patent Literature 1] Japanese Patent Laid-Open No. 2007-065651
SUMMARY OF INVENTION
Technical Problem
[0004] However, according to the method of enlarging the incident
effective diameter of one of two observation optical systems, there
is a problem that although the resolving power of the observation
optical system increases, the incident effective diameter of the
other system needs to be reduced, and the resolving power is
further reduced.
[0005] The present invention has been made in view of the problem,
and an object of the present invention is to provide a microscope
apparatus configured to enlarge entrance pupils while maintaining
the rotational symmetry of optical systems of a plurality of
optical paths after ejection of light from an objective lens to
bring out the performance of the objective lens.
Solution to Problem
[0006] To solve the problem, a first present invention provides a
microscope apparatus including, in order from an object side: an
objective lens having a function of collecting light from the
object; and two or more optical paths in which all lens groups are
rotational symmetric systems and through which light exited from
the objective lens passes, wherein when a sum of maximum diameters
of entrance pupils of optical systems forming any two of the
optical paths among the two or more optical paths is set as EDi,
and an axial luminous flux diameter determined from a maximum
aperture angle .alpha. and a focal distance f of the objective lens
is set as Dobj, a condition of the following expression is
satisfied,
.SIGMA.Di>Dobj
[0007] where Dobj=2fsin .alpha..
[0008] A second present invention provides a microscope apparatus
including, in order from an object side: an objective lens having a
function of collecting light from the object; and two or more
optical paths through which the light exited from the objective
lens passes, wherein when a sum of diameters passing through a
center of the objective lens among maximum diameters of entrance
pupils of optical systems forming any two of the optical paths
among the two or more optical paths is set as .SIGMA.Di', and an
axial luminous flux diameter determined from a maximum aperture
angle .alpha. and a focal distance f of the objective lens is set
as Dobj, a condition of the following expression is satisfied,
.SIGMA.Di'>Dobj
[0009] where Dobj=2fsin .alpha..
[0010] A third present invention provides a microscope apparatus
including, in order from an object side: an objective lens having a
function of collecting light from the object; and two or more
optical paths through which the light exited from the objective
lens passes, wherein when maximum diameters of entrance pupils of
optical systems forming any two of the optical paths among the two
or more optical paths are set as Dep1 and Dep2, a sum of the
maximum diameters of the two entrance pupils is set as .SIGMA.Di'',
a distance between centers of the two entrance pupils is set as Dx,
and an axial luminous flux diameter determined from a maximum
aperture angle .alpha. and a focal distance f of the objective lens
is set as Dobj, a condition of the following expression is
satisfied,
.SIGMA.Di''>Dobj
Dx.gtoreq.Dep1
Dep1=Dep2
[0011] where Dobj=2fsin .alpha..
[0012] In the microscope apparatus, it is preferable that the
number of the optical paths is 2. Alternatively, the number of the
optical paths is 3.
[0013] In the microscope apparatus, it is preferable that the two
or more optical paths are movable relative to the optical axis of
the objective lens while a positional relationship of each other is
maintained.
[0014] It is preferable that one of the two or more optical paths
is movable to bring the optical axis of the optical system forming
the optical path in line with the optical axis of the objective
lens. It is preferable that the, maximum diameter of the entrance
pupil of the optical system forming the optical path including the
optical axis that can be brought in line with the optical axis of
the objective lens is the largest among the maximum diameters of
the entrance pupils of the optical systems forming the two or more
optical paths. It is preferable that one of the two or more optical
paths is used as an illumination optical path.
[0015] It is preferable that one of the two or more optical paths
is movable to completely include the entire entrance pupil of the
optical system forming the optical path within the axial luminous
flux diameter of the objective lens.
[0016] In the microscope apparatus, it is preferable that at least
one of the two or more optical paths includes: afocal variable
power optical systems that eject light, which is ejected
substantially parallel to the optical axis of the objective lens
from the objective lens, as a plurality of substantially parallel
lights; and an imaging lens that collects the substantially
parallel lights ejected from the afocal variable power optical
system, and at least one of the afocal variable power optical
systems includes, at at least part of a section for changing the
magnification from a high-power end state to a low-power end state,
at least two lens groups that move to include components in a
direction orthogonal to the optical axis of the objective lens.
Advantageous Effects of Invention
[0017] If the microscope apparatus according to the present
invention is configured as described above, entrance pupils of
optical systems can be enlarged while maintaining the rotational
symmetry of the optical systems of a plurality of optical paths
after ejection of light from an objective lens to bring out the
performance of the objective lens.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a perspective view showing an appearance of a
parallel stereoscopic microscope.
[0019] FIG. 2 is an explanatory view showing a configuration of an
optical system of a microscope apparatus according to a first
embodiment.
[0020] FIG. 3 is an explanatory view showing a pupil aperture
defined by an objective lens and pupil apertures defined by
variable power lens groups in a conventional microscope.
[0021] FIG. 4A is an explanatory view showing a pupil aperture
defined by an objective lens and pupil apertures defined by
variable power lens groups in a microscope apparatus according to
the first embodiment.
[0022] FIG. 4B is an explanatory view for showing a sum of maximum
diameters of entrance pupils and a distance between the centers in
the pupil aperture defined by the objective lens and the pupil
apertures defined by the variable power lens groups.
[0023] FIG. 5 shows PSF cross-sectional views in the microscope
apparatus according to the first embodiment, (a) being a
cross-sectional view in an X-axis direction, (b) being a
cross-sectional view in a Y-axis direction.
[0024] FIG. 6 shows explanatory views indicating the pupil aperture
defined by the objective lens and the pupil apertures defined by
the variable power lens groups in the microscope apparatus
according to a modified example 1 of the first embodiment, (a)
showing a case in which the entrance pupil of an optical path for
right eye is included in an axial luminous flux diameter of the
objective lens, (b) showing a case in which the entrance pupil of
an optical path for left eye is included in the axial luminous flux
diameter of the objective lens.
[0025] FIG. 7 shows cross-sectional views of an optical system of a
conventional parallel stereoscopic microscope apparatus, (a)
showing a low-power end state, (b) showing a high-power end
state.
[0026] FIG. 8 shows cross-sectional views of a variable power lens
group according to a modified example 2 of the first embodiment,
(a) showing a low-power end state, (b) showing a medium-power
state, (c) showing a high-power end state.
[0027] FIG. 9 shows cross-sectional views of an optical system of a
parallel stereoscopic microscope according to the modified example
2 of the first embodiment, (a) showing a low-power end state, (b)
showing a high-power end state.
[0028] FIG. 10 shows explanatory views indicating a pupil aperture
defined by the objective lens and pupil apertures defined by the
variable power lens groups in a microscope apparatus according to a
second embodiment, (a) showing a case in which a sample is observed
by a stereoscopic vision optical path, (b) showing a case in which
a sample is observed by a vertical vision optical path.
[0029] FIG. 11 shows explanatory views indicating configurations of
an optical system of the microscope apparatus according to the
second embodiment, (a) showing the stereoscopic vision optical
path, (b) showing the vertical vision optical path.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0030] Hereinafter, preferred embodiments of the present invention
will be described with reference to the drawings. In a first
embodiment, a case of dividing light exited from an objective lens
into two optical paths will be described. First, a configuration of
a parallel stereoscopic microscope will be described using FIG. 1.
A parallel stereoscopic microscope 100 is a microscope apparatus
with a single-objective binocular configuration and includes: a
base unit (illumination unit) 101 including a transmitted
illumination apparatus; a variable power lens barrel 103 provided
with an objective lens and an eyepiece and including variable power
lens groups (variable power optical systems) inside; and a focusing
apparatus 105. A sample platform 102 embedded with a transparent
member is provided on the upper surface of the base unit 101. The
objective lens is attached to an objective lens attachment unit 106
provided below the variable power lens barrel 103. In the objective
lens attachment unit 106, one of a plurality of predetermined
low-power objective lenses and high-power objective lenses is
selected and attached in some cases, and a plurality of lenses
among a plurality of predetermined low-power objective lenses and
high-power objective lenses are selected and attached in other
cases.
[0031] Variable power lens groups for left eye and right eye are
arranged inside the variable power lens barrel 103, and a variable
power knob 107 is arranged outside the variable power lens barrel
103. The variable power lens groups include movable groups for
changing the magnification, and as the variable power knob 107 is
rotated, the variable power lens groups move in an optical axis
direction in accordance with a predetermined amount of movement.
The variable power lens groups include adjustable diaphragms, and
an adjustment mechanism of the adjustable diaphragms is arranged in
the variable power lens barrel 103. The focusing apparatus 105
includes a focusing knob 108 and a mechanism unit (not shown) that
vertically moves the variable power lens barrel 103 along the axis
based on the rotation of the focusing knob 108. Binocular lens
barrels 104 including imaging lenses and eyepieces are attached
above the variable power lens barrel 103. The imaging lenses
arranged on the left and right collect the parallel light exited
from the variable power lens groups for left and right eyes to
temporarily form images of the sample, and the eyepieces attached
to upper end sections of the binocular lens barrels 104 can be used
to observe the formed images by the naked eye.
[0032] FIG. 2 shows a configuration of an optical system of the
parallel stereoscopic microscope 100 with the single-objective
binocular configuration. As described, the parallel stereoscopic
microscope 100 includes, in order from the object side, an
objective lens 1 and two optical paths for right eye and left eye
that are arranged parallel to the optical axis of the objective
lens 1 and that include optical axes different from (do not match)
the optical axis of the objective lens 1 (hereinafter, the optical
paths will be called "observation optical systems 2"). In the
parallel stereoscopic microscope 100 shown in FIG. 2, each of the
two observation optical systems 2 includes an afocal variable power
lens group 3 and an imaging lens 4. In the parallel stereoscopic
microscope 100, the objective lens 1 that has focused the surface
of the object plays a role of guiding the afocal luminous flux to
the following variable power lens groups 3 for left and right eyes.
The parallel luminous flux radiated from the object and ejected
from the objective lens 1 is divided into the two variable power
lens groups 3, and the luminous flux diameter is changed. The
imaging lenses 4 then form enlarged images of the object, and a
minute object can be stereoscopically viewed by separately
observing the images by left and right eyes through eyepieces not
shown. Therefore, the numerical aperture that determines the
resolving power of the parallel stereoscopic microscope 100 is not
an axial ray angle .alpha. entering the objective lens 1, but is an
angle .beta. based on the optical axes of the variable power lens
groups 3 inclined to the surface of the object. Meanwhile, the
luminous flux is not divided in a normal optical microscope, and
the numerical aperture is defined by the angle .alpha..
[0033] Entrance pupils of the variable power lens groups (variable
power optical systems) 3 in the parallel stereoscopic microscope
are the largest when the magnification is the highest power, and
the entrance pupil diameters are substantially equal to the lens
effective diameters closest to the objective lens 1 (equivalent to
Dep1 and Dep2 of FIG. 2). Therefore, the maximum diameters of the
entrance pupils of the two variable power lens groups 3 will be
indicated as Dept and Dep2 in the following description. FIG. 3
shows pupil apertures of the objective lens 1 and the variable
power lens groups 3 in a plane .xi. shown in FIG. 2 in a
conventional stereoscopic microscope, and only shaded sections
enter the left and right variable power lens groups 3 in an ejected
axial luminous flux diameter of the objective lens 1 indicated by a
circle with a diameter Dobj. More specifically, if the incident
effective diameters Dep1 and Dep2 of the two variable power lens
groups 3 are equal, the angle .beta. is approximately half the
angle .alpha.. Therefore, if the objective lens 1 that is the same
as a normal optical microscope is mounted on the parallel
stereoscopic microscope 100, the resolving power of the parallel
stereoscopic microscope 100 is approximately half that of the
normal optical microscope.
[0034] In the first embodiment, the lens effective diameters Dep1
and Dep2 of the two variable power lens groups (variable power
optical systems) 3 closest to the objective lens 1 are designed to
satisfy the following conditional expression (1) relative to the
axial luminous flux diameter Dobj by which the axial light emitted
from the intersection between the sample surface and the optical
axis of the objective lens 1 is ejected from the objective lens 1.
It is assumed that the effective diameters Dep1 and Dep2 of the
variable power lens groups 3 satisfy the following expression (2)
(therefore, the effective diameters are the same).
Dep1+Dep2>Dobj (1)
Dep1=Dep2 (2)
[0035] FIG. 4A shows pupil apertures of the objective lens 1 and
the variable power lens groups 3 in the plane .xi. shown in FIG. 2
when the objective lens 1 and the two variable power lens groups 3
satisfy the expressions (1) and (2). In the ejected axial luminous
flux diameter of the objective lens 1 indicated by a circle with
the diameter Dobj, only the sections (shaded sections) that overlap
with the circles with the diameters Dep1 and Dep2 enter the left
and right variable power lens groups 3. In this case, Dobj is
defined by the following expression (3) based on .alpha. shown in
FIG. 2 and a focal distance f of the objective lens 1 and is
substantially the same as the ejection-side effective diameter of
the objective lens 1.
Dobj=2fsin .alpha. (3)
[0036] Assuming a direction that the two variable power lens groups
3 are lined up (direction connecting the optical axes of the
variable power lens groups 3) is an X axis and a direction
orthogonal to the X axis is a Y axis in FIG. 4A, aperture shapes of
the pupil apertures defined by .beta. are not optical-axis
symmetric (point symmetric), but are Y-axis symmetric (line
symmetric). As a result, the resolving power varies depending on
the direction. FIG. 5 displays, on top of each other, values of PSF
(point image distribution function) in the conventional parallel
stereoscopic microscope shown in FIG. 3 and values of PSF in the
parallel stereoscopic microscope 100 according to the first
embodiment shown in FIG. 4A (therefore, the parallel stereoscopic
microscope 100 satisfying the expressions (1) and (2)). FIG. 5(a)
is a PSF cross-sectional view of the X-axis direction in FIG. 4A,
and FIG. 5(b) is a PSF cross-sectional view of the Y-axis direction
in FIG. 4A. The PSF cross-sectional views are on the assumption
that there is no aberration in the optical system of the parallel
stereoscopic microscope 100. As is clear from FIGS. 3 and 4A, a
pupil aperture diameter DepX in the X-axis direction is not
different between the conventional parallel stereoscopic microscope
and the parallel stereoscopic microscope 100 according to the first
embodiment, and there is no change in the values of PSF. However, a
pupil aperture diameter DepY' of the Y-axis direction in the first
embodiment is larger than a pupil aperture diameter DepY in the
conventional Y-axis direction, and the half width of PSF in the
Y-axis direction is different. The half width of the parallel
stereoscopic microscope 100 according to the first embodiment is
smaller, and it can be recognized that the resolving power is
increased.
[0037] In this way, according to the parallel stereoscopic
microscope 100 of the first embodiment, the entrance pupils can be
enlarged while maintaining the rotational symmetry of the optical
systems (variable power lens groups 3) of the plurality of optical
paths after ejection of light from the objective lens 1, and the
performance of the objective lens 1 can be brought out.
[0038] Although a case of dividing the light exited from the
objective lens 1 into two optical paths has been described in the
above description, the conditional expression (1) is also effective
when the light is divided into three or more optical paths. In that
case, a sum EDi of the maximum diameters of the entrance pupils of
the optical systems forming any two optical paths among two or more
optical paths needs to satisfy the condition of the following
expression (4) relative to the ejected axial luminous flux diameter
Dobj defined by the maximum aperture angle .alpha. and the focal
distance f of the objective lens 1. In this case, all lens groups
of two optical paths (observation optical systems 2) have
rotational symmetric shapes.
.SIGMA.Di>Dobj (4)
[0039] where Dobj=2fsin .alpha.
[0040] Alternatively, a sum .SIGMA.Di' of the diameters passing
through the center of the objective lens 1 (see FIG. 4B) among the
maximum diameters of the entrance pupils of the optical systems
forming any two optical paths among two or more optical paths needs
to satisfy the condition of the following expression (5) relative
to the ejected axial luminous flux diameter Dobj determined from
the maximum aperture angle .alpha. and the focal distance f of the
objective lens 1.
.SIGMA.Di'>Dobj (5)
[0041] where Dobj=2f-sin .alpha.
[0042] Alternatively, when the maximum diameters of the entrance
pupils of the optical systems forming any two optical paths among
two or more optical paths are assumed as Dep1 and Dep2, a sum
.SIGMA.Di'' of the maximum diameters of the two entrance pupils
needs to satisfy the condition of the following expression (6)
relative to the ejected axial luminous flux diameter Dobj
determined from the maximum aperture angle .alpha. and the focal
distance f of the objective lens 1, and a distance Dx between the
centers of the two entrance pupils needs to satisfy the following
expression (7). In this case, it is assumed that the maximum
diameters Dep1 and Dep2 of the entrance pupils satisfy the
following formula (8) (therefore, the diameters are the same).
.SIGMA.Di''>Dobj (6)
Dx.gtoreq.Dep1 (7)
Dep1=Dep2 (8)
[0043] where Dobj=2fsin .alpha.
Modified Example 1 of First Embodiment
[0044] Although a case of symmetrically arranging the two
observation optical systems 2 (variable power lens groups 3) in the
X-axis direction of FIG. 4A relative to the optical axis of the
objective lens 1 has been described in the above description, the
entire variable power lens barrel 103 can be moved relative to the
optical axis so that the axial luminous flux diameter Dobj of the
objective lens 1 completely includes the entrance pupil of one of
the two observation optical systems 2 as shown in FIG. 6 to
increase the numerical aperture of at least the optical path of one
side compared to the numerical aperture of the conventional
parallel stereoscopic microscope apparatus in which the numerical
aperture is limited to the distance between the optical axes.
Particularly, if the axial luminous flux diameter Dobj of the
objective lens 1 is designed to be able to include any one of, the
entrance pupils of the left and right optical paths (entrance pupil
indicated by Dep1 or entrance pupil indicated by Dep2) as shown in
FIGS. 6(a) and (b), any one of the left and right optical paths can
be selected as an optical path with high numerical aperture
depending on the dominant eye of the observer, and the convenience
of the observer can be improved.
Modified Example 2 of First Embodiment
[0045] In recent years, demand for a stereoscopic microscope
apparatus capable of observing a wide variable power range by one
apparatus is increasing along with the diversification of
applications. Particularly, there is a strong demand for the
enlargement to the low-power range that allows viewing the entire
image of a small animal or the like. FIG. 7 shows optical path
diagrams of the objective lens 1 and the variable power lens group
3 of one side, and configurations in which the variable power lens
group 3 in two different states of magnification is set to the same
objective lens 1 are arranged above and below. FIG. 7(a) shows a
low-power end state, and FIG. 7(b) shows a high-power end state. As
is clear from FIG. 7, the position of the ray passing through the
objective lens 1 is totally different during low-power and during
high-power of the variable power lens group 3.
[0046] The magnification of the observation optical system 2 can be
calculated by dividing a value f zoom, which is obtained by
multiplying a focal distance of the imaging lens not shown in FIG.
7 by an afocal magnification of the variable power lens group 3, by
a focal distance f obj of the objective lens 1. As is clear from
the definition, the value f zoom needs to be reduced, or the focal
distance f obj of the objective lens 1 needs to be increased to
enlarge the variable power range to the low-power side. However,
the increase in the focal distance f obj of the objective lens 1
leads to the enlargement of the objective lens 1, and the increase
needs to be avoided. Consequently, the reduction in the value f
zoom is inevitably required. An angle .theta. of the ray ejected
from the objective lens 1 and entering the variable power lens
group 3 relative to the optical axis (shown in FIG. 7(a)) is in
accordance with an image height y=f zoomtan .theta.. Since the size
of the image is constant, the angle .theta. increases if the value
f zoom decreases. As is clear from FIG. 7(a), the main cause of the
enlargement of the objective lens 1 is a light flux with large
angle .theta.. It can be recognized that the object side of the
objective lens 1 is particularly enlarged. Although only one
example will be described here, the ray on the low-power side (FIG.
7(a)) generally determines the size of the diameter on the object
side of the objective lens 1, and the ray on the high-power side
(FIG. 7(b)) determines the size of the diameter on the image side
of the objective lens 1. The luminous flux on the high-power side
is limited by the diameter of the lens positioned on the object
side of the variable power lens group 3, and the luminous flux on
the low-power side is limited by the diameter of the lens
positioned on the image side of the variable power lens group 3.
Therefore, an entrance pupil diameter D_Low on the low-power side
decreases relative to an entrance pupil diameter D_High on the
high-power side. Due to the forgoing reasons, the entrance pupil on
the low-power side is small, and the angle .theta. of the ray
inevitably becomes large. Since the expression (4) is satisfied in
the present embodiment, the distance between optical axes is longer
than that of the conventional parallel stereoscopic microscope
apparatus. Consequently, the ambient light apart from the optical
axis of the objective lens 1 is rejected if the size of the
effective diameter of the objective lens 1 is maintained. On the
high-power side, the entrance pupil diameter D_High is large, and
the angle .theta. is small. Therefore, even if the luminous flux is
limited by the diameter of the objective lens 1, only the amount of
ambient light is reduced, and the field of view is not lost.
However, on the low-power side, the entrance pupil diameter D_Low
is small, and the angle .theta. is large as described above.
Therefore, the limitation by the diameter of the objective lens 1
has a great impact. In some cases, not only the amount of ambient
light is reduced, but also part of the field of view is completely
lost.
[0047] In the present modified example, a parallel stereoscopic
microscope will be described in which at least one of the plurality
of variable power lens groups 3 includes at least two lens groups
that move to include components in a direction orthogonal to the
optical axis of the objective lens 1 in at least part of the
section for changing the magnification from the high-power end
state to the low-power end state to prevent the ambient luminous
flux in low-power from being rejected as shown in FIG. 8.
[0048] A case is illustrated in which the variable power lens group
3 arranged on the parallel stereoscopic microscope according to the
present modified example includes four lens groups in total, a
first lens group G1 with positive refractive power, a second lens
group G2 with negative refractive power, a third lens group G3 with
positive refractive power, and a fourth lens group G4 with negative
refractive power, in order from the object side. In the variable
power optical system 3, the second lens group G2 moves in a certain
direction from the object side to the image side, and the third
lens group G3 moves in a certain direction from the image side to
the object side during the change in the magnification from the
low-power end state (FIG. 8(a)) to the high-power end state (FIG.
8(c)). Therefore, the second lens group G2 and the third lens group
G3 are designed to always move in certain directions only and not
to move in reverse directions in the middle of the change in the
magnification. A diaphragm S is arranged between the second lens
group G2 and the third lens group G3. The first lens group G1 and
the fourth lens group G4 are fixed during the change in the
magnification.
[0049] In the parallel stereoscopic microscope, at least one of the
lens groups constituting the variable power lens groups 3 is moved
to include components in the vertical direction of the optical axis
(hereinafter, the lens group will be called a "first correction
lens group CG1"). More specifically, the optical axis of the first
correction lens group CG1 is decentered relative to an optical axis
A (for example, an optical axis of a fixed lens group (for example,
the first lens group G1) among the lens groups included in the
variable power lens group 3) as a basis of the variable power lens
group 3. The first correction lens group CG1 may be at least one of
the lens groups for which the magnification is changed by the
movement along the optical axis during the change in the
magnification, the first correction lens group CG1 may be at least
one of the lens groups not moved along the optical axis during the
change in the magnification, or the first correction lens group CG1
may be both (in FIGS. 8 and 9, the second lens group G2 for which
the magnification is changed by the movement along the optical axis
during the change in the magnification is set as the first
correction lens group CG1).
[0050] As described, FIG. 9 shows the objective lens 1 and the
variable power lens group 3 of one side arranged on the optical
paths for left and right eyes. In the variable power lens group 3,
some of the lens groups on the object side (the first lens group G1
fixed during the change in the magnification and the second lens
group G2 moved during the change in the magnification) are
illustrated. As shown in FIG. 9, when the magnification is changed
to the low-power side, the second lens group G2 (the first
correction lens group CG1) is moved to reduce the distance between
the optical axes of the left and right variable power lens groups 3
(to bring close to the optical axis of the objective lens 1). Even
if the first correction lens group CG1 is moved this way during the
change in the magnification, the maximum diameter of the light
entering the variable power lens groups 3 is smaller during the
low-power than during the high-power as described above. Therefore,
the light can be set within the lens effective diameter (maximum
diameter that the light can enter) of the first lens group G1. As a
result, the ray at the peripheral part among the rays passing
through the objective lens 1 approaches the optical axis side of
the objective lens 1, and the rejection of the ambient luminous
flux in the low-power can be prevented.
[0051] It is desirable that the variable power lens group 3 is an
afocal variable power optical system that changes the luminous flux
diameter of the entering parallel luminous flux to eject the
parallel luminous flux. Therefore, as the first correction lens
group CG1 is decentered, the optical path in the variable power
lens group 3 is changed, and the ejected luminous flux is deviated
from the parallel luminous flux. The deviation needs to be
corrected by moving at least one of the other lens groups
(hereinafter, the lens group will be called a "second correction
lens group CG2", and the lens group is the third lens group G3 in
FIG. 8) to include components in the vertical direction of the
optical axis to eject the light as a parallel luminous flux. The
luminous flux entering the variable power lens group 3 is the
maximum during the highest power. Therefore, during the highest
power of the variable power lens group 3, it is desirable that the
optical axes of all lens groups included in the variable power lens
group 3 substantially match (substantially coincide with the
optical axis A as a basis) to effectively use the entrance pupil of
the variable power lens group 3.
Second Embodiment
[0052] In the parallel stereoscopic microscope, the variable power
ratio of the variable power lens group 3 is changed to observe the
sample (object). Not much resolving power is required to observe a
relatively wide section of the sample at low-power, but high
resolving power is required to enlarge and observe a narrower
section at high-power. On the other hand, there is a high demand
for stereoscopically viewing the sample by setting two observation
optical systems for left and right eyes in the observation at
low-power, but the stereoscopic vision is not much needed in the
observation at high-power. Therefore, a second embodiment describes
a microscope apparatus that includes a stereoscopic vision optical
path for stereoscopically viewing the sample by two optical paths
(observation optical systems 2) and a vertical vision optical path
for improving the resolution of the image of the sample by one
optical path (observation optical system 2') depending on the
object of the observation (therefore, the light exited from the
objective lens 1 is divided into three optical paths in total).
[0053] A parallel microscope 100' according to the second
embodiment shown in FIG. 10 includes the normal observation optical
systems 2 arranged on the left and right of the optical axis of the
objective lens 1 (hereinafter, also called "stereoscopic vision
optical paths 2") as in the parallel stereoscopic microscope
(microscope apparatus) 100 according to the first embodiment and
also includes another optical path 2' for vertical vision in
addition to the optical paths. In the microscope apparatus 100'
with the configuration, the vertical vision optical path 2' is used
not as an observation optical path, but as an illumination optical
path in the stereoscopic vision observation of the sample using the
left and right observation optical paths (stereoscopic vision
optical paths 2) as shown in FIG. 10(a). This can prevent the
self-fluorescence of glass caused by the illumination light from
becoming noise. As shown in FIG. 10(b), if the entire variable
power lens barrel 103 is moved relative to the optical axis of the
objective lens 1 to bring the optical axis of the objective lens 1
in line with the optical axis of the vertical vision optical path
2', the vertical vision is possible. A prism element 5 for dividing
the light for the binocular lens barrels as shown for example in
FIG. 11(b) can be included in the vertical vision optical path 2'
to smoothly switch the observation by both eyes for the
stereoscopic vision and the vertical vision. As shown in FIG.
11(a), the mechanisms of the left and right optical path diameters
(Dep1 and Dep2) are close to each other in the stereoscopic vision
optical path 2, and the enlargement of one side interferes the
other. Therefore, it is difficult to enlarge the optical path
diameters. However, in the vertical vision optical path 2' shown in
FIG. 11(b), there is no pair of optical paths that limits the
optical path diameter (Dph), and the diameter can be easily
enlarged. Therefore, a bright image with higher resolving power can
be obtained. A bright image with higher resolving power than the
normal stereoscopic microscope can be obtained when a condition of
Dph>0.5 Dobj is satisfied. Particularly, the sample can be
observed by twice or more brightness during the fluorescence
observation when a condition of Dph>0.6 Dobj is satisfied.
[0054] As described, an object of the vertical vision optical path
2' is to improve the resolution. Therefore, it is desirable that
the maximum diameter Dph of the entrance pupil of the vertical
vision optical path 2' is the largest among the maximum diameters
of the entrance pupils of the plurality of optical paths arranged
in the microscope apparatus 100' (in the present embodiment, it is
desirable that the maximum diameter Dph is greater than the
entrance pupils Dep1 and Dep2 of the two stereoscopic vision
optical paths 2).
REFERENCE SIGNS LIST
[0055] 1 objective lens 2, 2' observation optical systems (optical
paths) [0056] 3 variable power lens group 4 imaging lens [0057]
100, 100' parallel stereoscopic microscopes (microscope
apparatuses) [0058] CG1 (G2) first correction lens group [0059] CG2
(G3) second correction lens group
* * * * *