U.S. patent application number 13/909456 was filed with the patent office on 2013-11-28 for imaging optical system, microscope apparatus including the imaging optical system, and stereoscopic 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, Hiroaki Nakayama, Yumiko Ouchi.
Application Number | 20130314776 13/909456 |
Document ID | / |
Family ID | 42395557 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130314776 |
Kind Code |
A1 |
MIZUTA; Masahiro ; et
al. |
November 28, 2013 |
IMAGING OPTICAL SYSTEM, MICROSCOPE APPARATUS INCLUDING THE IMAGING
OPTICAL SYSTEM, AND STEREOSCOPIC MICROSCOPE APPARATUS
Abstract
A variable power optical system used in a parallel stereoscopic
microscope apparatus includes a plurality of optical paths in which
optical axes are arranged substantially parallel, a plurality of
lens groups that change the magnification of a diameter of a
luminous flux entering substantially parallel to each of the
optical paths to eject the luminous flux as substantially parallel
luminous fluxes, and at least two lens groups move along the
optical axis in each optical path according to the change in the
magnification. At least two lens groups of at least one optical
path among the plurality of optical paths move in a direction
including a component perpendicular to the optical axis according
to the change in the magnification at at least part of a section
where the magnification is changed from a high-power end state to a
low-power end.
Inventors: |
MIZUTA; Masahiro; (Kawasaki,
JP) ; Nakayama; Hiroaki; (Kawasaki, JP) ;
Ouchi; Yumiko; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIKON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
42395557 |
Appl. No.: |
13/909456 |
Filed: |
June 4, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13190733 |
Jul 26, 2011 |
8477417 |
|
|
13909456 |
|
|
|
|
PCT/JP2010/050872 |
Jan 25, 2010 |
|
|
|
13190733 |
|
|
|
|
Current U.S.
Class: |
359/374 ;
359/380; 359/676 |
Current CPC
Class: |
G02B 21/082 20130101;
G02B 15/1421 20190801; G02B 21/22 20130101; G02B 21/025 20130101;
G02B 15/14 20130101 |
Class at
Publication: |
359/374 ;
359/676; 359/380 |
International
Class: |
G02B 15/14 20060101
G02B015/14; G02B 21/22 20060101 G02B021/22; G02B 21/02 20060101
G02B021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2009 |
JP |
2009-018207 |
Mar 13, 2009 |
JP |
2009-061032 |
Apr 10, 2009 |
JP |
2009-095469 |
Jun 10, 2009 |
JP |
2009-138876 |
Jul 31, 2009 |
JP |
2009-178820 |
Nov 26, 2009 |
JP |
2009-268501 |
Claims
1-24. (canceled)
25. An imaging optical system that forms an image through an
objective lens and an observation optical system and that is
configured to be able to change the magnification of the image,
wherein the observation optical system comprises a plurality of
lens groups, and each of at least two lens groups among the
plurality of lens groups moves in a direction including a component
perpendicular to a reference optical axis of the observation
optical system at at least part of a section where the
magnification is changed from a high-power end state to a low-power
end state, when an amount of movement in a direction perpendicular
to the reference optical axis of the observation optical system, in
which a direction from the reference optical axis of the
observation optical system to an optical axis of the objective lens
is defined as negative, in a plane including the optical axis of
the objective lens and the reference optical axis of the
observation optical system is expressed as a function of a
position, which is on the reference optical axis of the observation
optical system of the lens group arranged closest to the objective
lens among the lens groups moved during the change in the
magnification and in which a direction for moving from the
low-power end state to the high-power end side is defined as
positive, at least one lens group arranged closest to the objective
lens among the at least two lens groups moves so that a first
derivative of the function is 0 or more and a second derivative of
the function is 0 or less at at least part of the section for
changing the magnification when the magnification is changed from
the low-power end state to the high-power end state.
26. The imaging optical system according to claim 25, wherein an
incident position of a principal ray with a largest angle relative
to the reference optical axis of the observation optical system
among the principal rays entering the observation optical system in
a tangent plane of a plane of the observation optical system
closest to the object is changed so that the position approaches
the reference optical axis side of the observation optical system
at least up to a predetermined focal length state when the
magnification is changed from the low-power end state to the
high-power end state.
27. The imaging optical system according to claim 25, wherein the
observation optical system comprises a plurality of optical paths
and ejects light from the objective lens from each of the plurality
of optical paths, and each of the optical paths comprises the
plurality of lens groups, at least one of the lens groups that move
in the direction including the component perpendicular to the
reference optical axis of the observation optical system is a first
correction lens group that moves to reduce a distance between the
optical axes of the lens groups in the plurality of optical paths
when the magnification is changed from the high-power end state to
the low-power end state, and remaining lens groups of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system are second correction lens groups that correct the
optical paths changed by the first correction lens group to eject
the light so that the image is formed at an image forming position
where the image would be formed when the plurality of lens groups
are arranged so that optical axes of the plurality of lens groups
match.
28. The imaging optical system according to claim 25, wherein the
observation optical system comprises an afocal variable power
optical system, and the afocal variable power optical system
comprises the at least two lens groups.
29. The imaging optical system according to claim 25, wherein the
optical axes of the plurality of lens groups substantially coincide
in the high-power end state.
30. The imaging optical system according to claim 25, wherein the
plurality of lens groups comprise: a first lens group arranged
closest to the object and fixed during the change in the
magnification; and a second lens group that is arranged on the
image side of the first lens group and that is one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system, and the optical axis of the second lens group is
decentered relative to the optical axis of the first lens group in
the low-power end state.
31. The imaging optical system according to claim 25, wherein the
plurality of optical paths of the observation optical system
comprises two optical paths for right eye and left eye.
32. A microscope apparatus comprising the imaging optical system
according to claim 25.
33. A stereoscopic microscope apparatus comprising: an objective
lens; a plurality of afocal variable power optical systems that
each eject a parallel light ejected substantially parallel to an
optical axis of the objective lens from the objective lens to be a
plurality of parallel lights; and a plurality of imaging lenses
that collect the parallel lights ejected from the plurality of
afocal variable power optical systems, wherein at least one of the
plurality of afocal variable power optical systems comprises at
least two lens groups that move in a direction including a
component perpendicular to a reference optical axis of the afocal
variable power optical systems at at least part of a section where
the magnification is changed from a low-power end state to a
high-power end state, when an amount of movement in a direction
perpendicular to the reference optical axis of the afocal variable
power optical systems, in which a direction from the reference
optical axis of the afocal variable power optical systems to an
optical axis of the objective lens is defined as negative, in a
plane including the optical axis of the objective lens and the
reference optical axis of the afocal variable power optical systems
is expressed as a function of a position, which is on the reference
optical axis of the afocal variable power optical systems of the
lens group arranged closest to the objective lens among the lens
groups moved during the change in the magnification and in which a
direction for moving from the low-power end state to the high-power
end side is defined as positive, at least one lens group arranged
closest to the objective lens among the at least two lens groups
moves so that a first derivative of the function is 0 or more and a
second derivative of the function is 0 or less at at least part of
the section for changing the magnification when the magnification
is changed from the low-power end state to the high-power end
state.
34-56. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application, filed under
35 U.S.C. .sctn.111(a), of International Application
PCT/JP2010/050872, filed Jan. 25, 2010, which claimed priority to
Japanese Application No. 2009-018207 filed Jan. 29, 2009, Japanese
Application No. 2009-061032 filed Mar. 13, 2009, Japanese
Application No. 2009-095469 filed Apr. 10, 2009, Japanese
Application No. 2009-138876 filed Jun. 10, 2009, Japanese
Application No. 2009-178820 filed Jul. 31, 2009 and Japanese
Application No. 2009-268501 filed Nov. 26, 2009, the disclosures of
which are hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to an imaging optical system,
a microscope apparatus including the imaging optical system, and a
stereoscopic microscope apparatus.
BACKGROUND ART
[0003] A stereoscopic microscope apparatus 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 microscope apparatus 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 apparatus, an optical
system of 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.
[0004] In the stereoscopic microscope apparatus, an example of a
typical method for obtaining a stereoscopic vision includes a
parallel stereoscopic microscope apparatus (parallel
single-objective binocular microscope apparatus). As shown in FIG.
30(a), a parallel stereoscopic microscope apparatus 100' includes
one objective lens 1' and two observation optical systems 2' for
right eye and left eye arranged parallel to the optical axis of the
objective lens 1'. Each of the observation optical systems 2'
usually includes a variable power mechanism which will be called a
variable power optical system 3' below. Each of the observation
optical systems 2' also includes an imaging lens 4'.
[0005] In the parallel stereoscopic microscope apparatus 100', the
objective lens 1' 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 optical systems 3'
for left and right eyes. The parallel luminous flux ejected from
the objective lens 1' is divided into the two variable power
optical systems 3' and is separately delivered to the left and
right eyes. As shown in FIG. 30(b), each of the two variable power
optical systems 3' is provided with a diaphragm S'. The position of
the entrance pupil here is a position where a diaphragm image
formed by a lens group in the variable power optical system 3'
closer to an object O than the diaphragm S' is created. In the
parallel stereoscopic microscope apparatus 100' with the
configuration, the definition of the objective lens numerical
aperture is different from that of a normal objective lens
numerical aperture as shown in FIG. 30(a). More specifically, if
the medium between the object O and the objective lens 1' is air,
the normal objective lens numerical aperture is defined by sine of
a half angle .alpha. of an angle of aperture of a luminous flux
which is spread over the entire aperture of the objective lens 1'
from the light ejected from a point on the optical axis of the
object O. The objective lens numerical aperture in the parallel
stereoscopic microscope apparatus 100' is defined by sine of a half
angle .beta. of an angle of aperture when the light ejected from a
point on the optical axis of the object O is spread to the maximum
diaphragm diameter of the diaphragm S' of one of the variable power
optical systems 3'.
[0006] FIG. 30(b) is a diagram enlarging the objective lens 1' and
part of the variable power optical system 3' of one side of FIG.
30(a). The light exited from the center of the surface of the
object O enters the objective lens 1' to form a parallel luminous
flux, and the parallel luminous flux enters the variable power
optical system 3'. Since the objective lens 1' sufficiently
satisfies the sine conditions, the parallel luminous flux diameter
is twice the product of a focal length fobj of the objective lens
and the objective lens numerical aperture sin .beta.. The luminous
flux needs to be guided to the variable power optical system 3' to
exhibit the performance in accordance with the objective lens
numerical aperture. Assuming that the effective diameter of the
variable power optical system 3' is Dep, a relationship of the
effective diameter Dep.gtoreq.the parallel luminous flux diameter
(=2fobjsin .beta.) needs to be satisfied. In other words, the
objective lens numerical aperture sin .beta. in the parallel
stereoscopic microscope apparatus 100' depends on the size of the
effective diameter Dep of the variable power optical system 3'. As
described, the stereoscopic microscope apparatus includes two
optical paths for left eye and right eye for stereoscopic vision,
and since the left and right optical paths are adjacent, the
enlargement of the effective diameters Dep of the variable power
optical systems 3' is synonymous with the enlargement of the
distance between left and right optical axes of the variable power
optical systems 3'. To put it plainly, it can be stated that the
distance between the left and right optical axes of the variable
power optical systems 3' determines the numerical aperture of the
parallel stereoscopic microscope apparatus 100'. The variable power
optical systems 3' are constituted as afocal variable power optical
systems in which an entering luminous flux and an ejected luminous
flux are parallel, and the imaging lenses 4' arranged subsequently
form an image. The magnification of the afocal variable power
optical system (hereinafter, called "afocal magnification") is
calculated by dividing the parallel luminous flux diameter on the
incident side by the parallel luminous flux diameter on the
ejection side. The magnification of the image can be calculated by
dividing a value fzoom, which is obtained by multiplying the focal
length of the imaging lens 4' by the afocal magnification, by the
focal length fobj of the objective lens 1'. 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. Consequently, a variable power
optical system is proposed in which the variable power range is
enlarged while the total length is controlled (for example, see
Patent Literature 1).
CITATION LIST
Patent Literature
[0007] Patent Literature 1 Japanese Patent Laid-Open No.
2005-91755
SUMMARY OF INVENTION
Technical Problem
[0008] However, there is a problem that not only the variable power
optical system, but also the objective lens is enlarged if the
variable power range is enlarged to the low-power side. FIG. 31
shows optical path diagrams of the objective lens 1' and part of
the variable power optical system 3' of one side. The variable
power optical system 3' in two different states of magnification is
connected to the same objective lens 1', and the diagrams are
arranged above and below. FIG. 31(a) shows a low-power end state,
and FIG. 31(b) shows a high-power end state. As is clear from FIG.
31, the position where the ray passes through the objective lens 1'
is totally different during low-power and during high-power of the
variable power optical system 3'. As described, the magnification
is calculated by dividing the value fzoom, which is obtained by
multiplying the focal length of the imaging lens by the afocal
magnification, by the focal length fobj of the objective lens 1'.
As is clear from the definition, the value fzoom needs to be
reduced, or the focal length fobj 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 length fobj of the
objective lens 1' leads to the enlargement of the objective lens
1', and the increase needs to be avoided. Consequently, the value
fzoom is inevitably reduced. Assuming that an image height is y and
a value obtained by multiplying the focal length of the imaging
lens 4' by the afocal magnification is fzoom, 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. 31(a)) is in accordance with y=fzoomtan .theta.'. Since the
size of the image is constant, .theta.' increases if fzoom is
reduced. As is clear from FIG. 31(a), the main cause of the
enlargement of the objective lens 1' is a light flux with a large
angle .theta.'. It can be recognized that the object O side of the
objective lens 1' is particularly enlarged. Although only one
example will be described here, the ray on the high-power side
usually determines the size on the image side of the objective lens
1', and the ray on the low-power side determines the size on the
objective side of the objective lens 1'. Particularly, the
enlargement of the object O side of the objective lens 1' is
disadvantageous in that the field of view of the surface of the
object is hidden as seen from the user, and the enlargement needs
to be avoided.
[0009] The present invention has been made in view of the problem,
and an object of the present invention is to provide an imaging
optical system capable of enlargement to a low-power range while
avoiding the enlargement of the objective lens in a microscope
apparatus that includes the objective lens and observation optical
systems (imaging optical system as a whole), and another object of
the present invention is to provide a microscope apparatus
including the imaging optical system and a stereoscopic microscope
apparatus.
Solution to Problem
[0010] To solve the problem, an imaging optical system according to
the present invention is an imaging optical system that forms an
image through an objective lens and an observation optical system
and that is configured to be able to change the magnification of
the image, characterized in that the observation optical system
comprises a plurality of optical paths and ejects light from the
objective lens from each of the plurality of optical paths, and
each of the optical paths comprises a plurality of lens groups, in
at least one of the plurality of optical paths, each of at least
two lens groups among the plurality of lens groups moves in a
direction including a component perpendicular to a reference
optical axis of the observation optical system at at least part of
a section where the magnification is changed from a high-power end
state to a low-power end state, at least one of the lens groups
that move in the direction including the component perpendicular to
the reference optical axis of the observation optical system is a
first correction lens group that moves so that a position of light
passing outermost from an optical axis of the objective lens moves
toward the optical axis of the objective lens compared with a case
of moving in a direction including only a component substantially
parallel to the reference optical axis, when the magnification is
changed from the high-power end state to the low-power end state,
and remaining lens groups of the lens groups that move in the
direction including the component perpendicular to the reference
optical axis of the observation optical system is a second
correction lens group that corrects the optical paths changed by
the first correction lens group.
[0011] Preferably, the imaging optical system is characterized in
that the first correction lens group moves to reduce a distance
between the optical axes of the lens groups in the plurality of
optical paths, and the second correction lens group ejects the
light so that the image is formed at an image forming position
where the image would be formed when the plurality of lens groups
are arranged so that each optical axis of the plurality of lens
groups matches the reference optical axis.
[0012] Preferably, the imaging optical system is characterized in
that the observation optical system comprises a diaphragm, and the
diaphragm moves in the direction including the component
perpendicular to the reference optical axis of the observation
optical system at at least part of the section for changing the
magnification from the low-power end state to the high-power end
state.
[0013] Preferably, the diaphragm is characterized by moving
following the lens groups that move in the direction including the
component perpendicular to the reference optical axis, and a center
of an exit pupil as an image of the diaphragm exists across the
entire variable power range on the reference optical axis of the
observation optical system.
[0014] Preferably, the imaging optical system is characterized in
that the observation optical system comprises a diaphragm, and the
diaphragm comprises, as an aperture section, the entire area where
the luminous flux moved by the lens groups that move in the
direction including the component perpendicular to the reference
optical axis is swept at at least part of the section for changing
the magnification from the low-power end state to the high-power
end state.
[0015] Preferably, the aperture section of the diaphragm is
characterized by being a precise circle including the entire
area.
[0016] Preferably, the imaging optical system is characterized in
that a light shielding unit is arranged at least on the optical
axis side of the objective lens of the lens groups that move in the
direction including the component perpendicular to the reference
optical axis of the observation optical system, the light shielding
unit blocking light passing through a space generated between the
lens groups and the optical axis of the objective lens along with
the movement of the lens groups in the direction perpendicular to
the reference optical axis.
[0017] Preferably, the light shielding unit is characterized by
being attached to connect each of the lens groups that move in the
direction including the component perpendicular to the optical axis
of the objective lens arranged on the plurality of optical paths
and expands and contracts along with the movement in the direction
including the component perpendicular to the reference optical axis
of the lens groups.
[0018] Preferably, the light shielding unit is characterized by
comprising: a first member formed by a member that blocks light,
provided with an aperture that is penetrated in a parallel
direction of the optical axis of the objective lens and that is in
substantially the same size as the lens groups that move in the
direction including the component perpendicular to the reference
optical axis of the observation optical system, and held by
setting, in the apertures, the lens groups that move in the
direction including the component perpendicular to the reference
optical axis of the observation optical system; and a second member
formed by a member that blocks light, movable in the optical axis
direction of the objective lens, holding the first member so that
the first member can be moved in the direction perpendicular to the
reference optical axis, and provided with aperture sections
penetrated in the parallel direction of the optical axis of the
objective lens, and the aperture sections of the second member are
formed so that the lens groups are positioned in the aperture
sections regardless of the movement of the lens groups that move in
the direction including the component perpendicular to the
reference optical axis.
[0019] Preferably, the first member is characterized by being
formed to cover the portion other than the lens groups that move in
the direction including the component perpendicular to the
reference optical axis of the observation optical system in the
aperture sections.
[0020] Preferably, the first member is characterized by including
elastic members that expand and contract in accordance with the
movement of the first member at both end portions in the direction
perpendicular to the reference optical axis.
[0021] Preferably, the first member and the elastic members are
characterized by being formed to cover the portion other than the
lens groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system in the aperture sections.
[0022] Preferably, the imaging optical system is characterized in
that the observation optical system comprises an afocal variable
power optical system, and the afocal variable power optical system
comprises the at least two lens groups.
[0023] Preferably, the imaging optical system is characterized in
that the optical axes of the plurality of lens groups substantially
coincide in the high-power end state.
[0024] Preferably, the imaging optical system is characterized in
that the plurality of lens groups comprise: a first lens group
arranged closest to the object and fixed during the change in the
magnification; and a second lens group that is arranged on the
image side of the first lens group and that is one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis, and the optical axis
of the second lens group is decentered relative to the optical axis
of the first lens group in the low-power end state.
[0025] Preferably, the imaging optical system is characterized in
that the plurality of optical paths of the observation optical
system comprises two optical paths for right eye and left eye.
[0026] A microscope apparatus according to the present invention is
characterized by comprising: an illumination optical system that
comprises a surface light emitter including a planar light emission
area and that directs light radiated from the surface light emitter
to an object; and any one of the imaging optical systems that
comprises an objective lens and that collects light from the object
to form an image of the object, wherein the surface light emitter
is arranged at a position conjugate to an entrance pupil of the
objective lens or near the position.
[0027] A microscope apparatus according to the present invention is
characterized by comprising: any of the imaging optical systems
that comprises an objective lens and that collects light from an
object to form an image of the object; and an illumination optical
system that collects light from a light source by an illumination
lens to guide the light to an optical path of the imaging optical
system and that directs the light to the object through the
objective lens, wherein the illumination optical system is
configured to move an image of the light source in accordance with
an exit pupil moved by the lens groups moved in the direction
including the component perpendicular to the reference optical axis
of the observation optical system.
[0028] Preferably, the illumination optical system is characterized
by steplessly and continuously moving the illumination lens in the
direction including the component perpendicular to the optical
axis.
[0029] Preferably, the illumination optical system is characterized
by moving the illumination lens in the direction including the
component perpendicular to the optical axis based on switching of
at least two positions.
[0030] Preferably, the microscope apparatus is characterized in
that the light source is steplessly, continuously, or based on
switching of at least two positions, moved in the direction
including the component perpendicular to the optical axis.
[0031] A microscope apparatus according to the present invention is
characterized by comprising: any one of the imaging optical systems
that comprises an objective lens and that collects light from an
object to form an image of the object; and an illumination optical
system that collects light from a light source by an illumination
lens to guide the light to an optical path of the imaging optical
system and that directs the light to the object through the
objective lens, wherein the illumination optical system forms an
image of the light source in a size including a trajectory of an
exit pupil moved by the lens groups that move in the direction
including the component perpendicular to the reference optical axis
of the observation optical system.
[0032] A stereoscopic microscope apparatus according to the present
invention is a stereoscopic microscope apparatus characterized by
comprising: an objective lens; a plurality of afocal variable power
optical systems that eject, as a plurality of parallel lights, a
parallel light ejected substantially parallel to an optical axis of
the objective lens from the objective lens; and a plurality of
imaging lenses that collect the parallel lights ejected from the
plurality of afocal variable power optical systems, wherein at
least one of the plurality of afocal variable power optical systems
comprises at least two lens groups that move in a direction
including a component perpendicular to a reference optical axis of
the afocal variable power optical systems at at least part of a
section where the magnification is changed from a high-power end
state to a low-power end state, at least one of the lens groups
that move in the direction including the component perpendicular to
the reference optical axis of the afocal variable power optical
systems is a first correction lens group that moves so that a
position of light passing outermost from an optical axis of the
objective lens moves toward the optical axis of the objective lens
compared with a case of moving in a direction including only a
component substantially parallel to the reference optical axis,
when the magnification is changed from the high-power end state to
the low-power end state, and remaining lens groups of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the afocal variable
power optical systems is a second correction lens group that
corrects the optical paths changed by the first correction lens
group.
[0033] Preferably, the stereoscopic microscope apparatus is
characterized by comprising an illumination optical system that
comprises a surface light emitter including a planar light emission
area and that directs light radiated from the surface light emitter
to an object, wherein the surface light emitter is arranged at a
position conjugate to an entrance pupil of the objective lens or
near the position.
[0034] An imaging optical system according to the present invention
is an imaging optical system that forms an image through an
objective lens and an observation optical system and that is
configured to be able to change the magnification of the image,
characterized in that the observation optical system comprises a
plurality of lens groups, and each of at least two lens groups
among the plurality of lens groups moves in a direction including a
component perpendicular to a reference optical axis of the
observation optical system at at least part of a section where the
magnification is changed from a high-power end state to a low-power
end state, when an amount of movement in a direction perpendicular
to the reference optical axis of the observation optical system, in
which a direction from the reference optical axis of the
observation optical system to an optical axis of the objective lens
is defined as negative, in a plane including the optical axis of
the objective lens and the reference optical axis of the
observation optical system is expressed as a function of a
position, which is on the reference optical axis of the observation
optical system of the lens group arranged closest to the objective
lens among the lens groups moved during the change in the
magnification and in which a direction for moving from the
low-power end state to the high-power end side is defined as
positive, at least one lens group arranged closest to the objective
lens among the at least two lens groups moves so that a first
derivative of the function is 0 or more and a second derivative of
the function is 0 or less at at least part of the section for
changing the magnification when the magnification is changed from
the low-power end state to the high-power end state.
[0035] Preferably, the imaging optical system is characterized in
that an incident position of a principal ray with a largest angle
relative to the reference optical axis of the observation optical
system among the principal rays entering the observation optical
system in a tangent plane of a plane of the observation optical
system closest to the object is changed so that the position
approaches the reference optical axis side of the observation
optical system at least up to a predetermined focal length state
when the magnification is changed from the low-power end state to
the high-power end state.
[0036] Preferably, the imaging optical system is characterized in
that the observation optical system comprises a plurality of
optical paths and ejects light from the objective lens from each of
the plurality of optical paths, and each of the optical paths
comprises the plurality of lens groups, at least one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system is a first correction lens group that moves to
reduce a distance between the optical axes of the lens groups in
the plurality of optical paths when the magnification is changed
from the high-power end state to the low-power end state, and
remaining lens groups of the lens groups that move in the direction
including the component perpendicular to the reference optical axis
of the observation optical system are second correction lens groups
that correct the optical paths changed by the first correction lens
group to eject the light so that the image is formed at an image
forming position where the image would be formed when the plurality
of lens groups are arranged so that optical axes of the plurality
of lens groups match.
[0037] Preferably, the imaging optical system is characterized in
that the observation optical system comprises an afocal variable
power optical system, and the afocal variable power optical system
comprises the at least two lens groups.
[0038] Preferably, the imaging optical system is characterized in
that the optical axes of the plurality of lens groups substantially
coincide in the high-power end state.
[0039] Preferably, the imaging optical system is characterized in
that the plurality of lens groups comprise: a first lens group
arranged closest to the object and fixed during the change in the
magnification; and a second lens group that is arranged on the
image side of the first lens group and that is one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system, and the optical axis of the second lens group is
decentered relative to the optical axis of the first lens group in
the low-power end state.
[0040] Preferably, the imaging optical system is characterized in
that the plurality of optical paths of the observation optical
system comprises two optical paths for right eye and left eye.
[0041] A microscope apparatus according to the present invention is
characterized by comprising any one of the imaging optical
system.
[0042] A stereoscopic microscope apparatus according to the present
invention is a stereoscopic microscope apparatus characterized by
comprising: an objective lens; a plurality of afocal variable power
optical systems that each eject a parallel light ejected
substantially parallel to an optical axis of the objective lens
from the objective lens to be a plurality of parallel lights; and a
plurality of imaging lenses that collect the parallel lights
ejected from the plurality of afocal variable power optical
systems, wherein at least one of the plurality of afocal variable
power optical systems comprises at least two lens groups that move
in a direction including a component perpendicular to a reference
optical axis of the afocal variable power optical systems at at
least part of a section where the magnification is changed from a
low-power end state to a high-power end state, when an amount of
movement in a direction perpendicular to the reference optical axis
of the afocal variable power optical systems, in which a direction
from the reference optical axis of the afocal variable power
optical systems to an optical axis of the objective lens is defined
as negative, in a plane including the optical axis of the objective
lens and the reference optical axis of the afocal variable power
optical systems is expressed as a function of a position, which is
on the reference optical axis of the afocal variable power optical
systems of the lens group arranged closest to the objective lens
among the lens groups moved during the change in the magnification
and in which a direction for moving from the low-power end state to
the high-power end side is defined as positive, at least one lens
group arranged closest to the objective lens among the at least two
lens groups moves so that a first derivative of the function is 0
or more and a second derivative of the function is 0 or less at at
least part of the section for changing the magnification when the
magnification is changed from the low-power end state to the
high-power end state.
[0043] An imaging optical system according to the present invention
is an imaging optical system that forms an image through an
objective lens and an observation optical system and that is
configured to be able to change the magnification of the image,
characterized in that the observation optical system comprises a
plurality of lens groups and a diaphragm, and each of at least two
lens groups among the plurality of lens groups moves in a direction
including a component perpendicular to a reference optical axis of
the observation optical system at at least part of a section where
the magnification is changed from a low-power end state to a
high-power end state, and the diaphragm moves following the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system, and a center of an exit pupil as an image of the
diaphragm exists across the entire variable power range on the
reference optical axis of the observation optical system.
[0044] An imaging optical system according to the present invention
is an imaging optical system that forms an image through an
objective lens and an observation optical system and that is
configured to be able to change the magnification of the image,
characterized in that the observation optical system comprises a
plurality of lens groups and a diaphragm, and each of at least two
lens groups among the plurality of lens groups moves in a direction
including a component perpendicular to a reference optical axis of
the observation optical system at at least part of a section where
the magnification is changed from a low-power end state to a
high-power end state, and the diaphragm comprises, as an aperture
section, the entire area where the luminous flux moved by the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system is swept.
[0045] Preferably, the imaging optical system is characterized in
that the aperture section of the diaphragm is a precise circle
including the entire area.
[0046] Preferably, the imaging optical system is characterized in
that the observation optical system comprises a plurality of
optical paths and ejects light from the objective lens from each of
the plurality of optical paths, and each of the optical paths
comprises the plurality of lens groups, at least one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system is a first correction lens group that moves to
reduce a distance between the optical axes of the lens groups in
the plurality of optical paths when the magnification is changed
from the high-power end state to the low-power end state, and
remaining lens groups of the lens groups that move in the direction
including the component perpendicular to the reference optical axis
of the observation optical system are second correction lens groups
that correct the optical paths changed by the first correction lens
group to eject the light so that the image is formed at an image
forming position where the image would be formed when the plurality
of lens groups are arranged so that optical axes of the plurality
of lens groups match.
[0047] Preferably, the imaging optical system is characterized in
that the observation optical system comprises an afocal variable
power optical system, and the afocal variable power optical system
comprises the at least two lens groups.
[0048] Preferably, the imaging optical system is characterized in
that the optical axes of the plurality of lens groups and the
center of the diaphragm substantially coincide in the high-power
end state.
[0049] Preferably, the imaging optical system is characterized in
that the plurality of lens groups comprise: a first lens group
arranged closest to the object and fixed during the change in the
magnification; and a second lens group that is arranged on the
image side of the first lens group and that is one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system, and the optical axis of the second lens group is
decentered relative to the optical axis of the first lens group in
the low-power end state.
[0050] Preferably, the imaging optical system is characterized in
that the plurality of optical paths of the observation optical
system comprises two optical paths for right eye and left eye.
[0051] A microscope apparatus according to the present invention is
characterized by comprising any one of the imaging optical
system.
[0052] A stereoscopic microscope apparatus according to the present
invention is a stereoscopic microscope apparatus characterized by
comprising: an objective lens; a plurality of afocal variable power
optical systems that each eject a parallel luminous flux ejected
substantially parallel to an optical axis of the objective lens
from the objective lens to be a plurality of parallel luminous
flux; and a plurality of imaging lenses that collect the parallel
luminous flux ejected from the plurality of afocal variable power
optical systems, wherein at least one of the plurality of afocal
variable power optical systems comprises at least two lens groups
and a diaphragm, the at least two lens groups move in a direction
including a component perpendicular to a reference optical axis of
the afocal variable power optical systems at at least part of a
section where the magnification is changed from a low-power end
state to a high-power end state, and the diaphragm moves following
the lens groups that move in the direction including the component
perpendicular to the reference optical axis of the afocal variable
power optical systems, and a center of an exit pupil as an image of
the diaphragm exists across the entire variable power range on the
reference optical axis of the afocal variable power optical
systems.
[0053] A stereoscopic microscope apparatus according to the present
invention is a stereoscopic microscope apparatus characterized by
comprising: an objective lens; a plurality of afocal variable power
optical systems that each eject a parallel luminous flux ejected
substantially parallel to an optical axis of the objective lens
from the objective lens to be a plurality of parallel luminous
flux; and a plurality of imaging lenses that collect the parallel
luminous flux ejected from the plurality of afocal variable power
optical systems, wherein at least one of the plurality of afocal
variable power optical systems comprises at least two lens groups
and a diaphragm, the at least two lens groups move in a direction
including a component perpendicular to a reference optical axis of
the afocal variable power optical systems at at least part of a
section where the magnification is changed from a low-power end
state to a high-power end state, and the diaphragm comprises, as an
aperture section, the entire area where the luminous flux moved by
the lens groups that move in the direction including the component
perpendicular to the reference optical axis of the afocal variable
power optical systems is swept.
[0054] An imaging optical system according to the present invention
is an imaging optical system that forms an image through an
objective lens and an observation optical system and that is
configured to be able to change the magnification of the image,
characterized in that the observation optical system comprises a
plurality of optical paths and ejects light from the objective lens
from each of the plurality of optical paths, and each of the
optical paths comprises a plurality of lens groups, in at least one
of the plurality of optical paths, each of at least two lens groups
among the plurality of lens groups moves in a direction including a
component perpendicular to a reference optical axis of the
observation optical system at at least part of a section where the
magnification is changed from a high-power end state to a low-power
end state, and a light shielding unit is arranged at least on the
optical axis side of the objective lens of the lens groups that
move in the direction including the component perpendicular to the
reference optical axis of the observation optical system, the light
shielding unit blocking light passing through a space generated
between the lens groups and the optical axis of the objective lens
along with the movement of the lens groups in the direction
perpendicular to the reference optical axis.
[0055] Preferably, the imaging optical system is characterized in
that the light shielding unit is attached to connect each of the
lens groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system arranged on the plurality of optical paths and
expands and contracts along with the movement in the direction
including the component perpendicular to the reference optical axis
of the lens groups.
[0056] Preferably, the imaging optical system is characterized in
that the light shielding unit comprises: a first member formed by a
member that blocks light, provided with an aperture that is
penetrated in a parallel direction of the optical axis of the
objective lens and that is in substantially the same size as the
lens groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system, and held by setting, in the apertures, the lens
groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system; and a second member formed by a member that blocks
light, movable in the optical axis direction of the objective lens,
holding the first member so that the first member can be moved in
the direction perpendicular to the reference optical axis, and
provided with aperture sections penetrated in the parallel
direction of the optical axis of the objective lens, and the
aperture sections of the second member are formed so that the lens
groups are positioned in the aperture sections regardless of the
movement of the lens groups that move in the direction including
the component perpendicular to the reference optical axis.
[0057] Preferably, the imaging optical system is characterized in
that the first member is formed to cover the portion other than the
lens groups that move in the direction including the component
perpendicular to the reference optical axis of the observation
optical system in the aperture sections.
[0058] Preferably, the imaging optical system is characterized in
that the first member includes elastic members that expand and
contract in accordance with the movement of the first member at
both end portions in the direction perpendicular to the reference
optical axis.
[0059] Preferably, the imaging optical system is characterized in
that the first member and the elastic members are formed to cover
the portion other than the lens groups that move in the direction
including the component perpendicular to the reference optical axis
of the observation optical system in the aperture sections.
[0060] Preferably, the imaging optical system is characterized in
that the observation optical system comprises an afocal variable
power optical system, and the afocal variable power optical system
comprises the at least two lens groups.
[0061] Preferably, the imaging optical system is characterized in
that the optical axes of the plurality of lens groups substantially
coincide in the high-power end state.
[0062] Preferably, the imaging optical system is characterized in
that the plurality of lens groups comprise: a first lens group
arranged closest to the object and fixed during the change in the
magnification; and a second lens group that is arranged on the
image side of the first lens group and that is one of the lens
groups that move in the direction including the component
perpendicular to the reference optical axis, and the optical axis
of the second lens group is decentered relative to the optical axis
of the first lens group in the low-power end state.
[0063] Preferably, the imaging optical system is characterized in
that the plurality of optical paths of the observation optical
system comprises two optical paths for right eye and left eye.
[0064] A microscope apparatus according to the present invention is
characterized by comprising any one of the imaging optical
system.
[0065] A stereoscopic microscope apparatus according to the present
invention is a stereoscopic microscope apparatus characterized by
comprising: an objective lens; a plurality of afocal variable power
optical systems that each eject a parallel light ejected
substantially parallel to an optical axis of the objective lens
from the objective lens to be a plurality of parallel lights; and a
plurality of imaging lenses that collect the parallel lights
ejected from the plurality of afocal variable power optical
systems, wherein at least one of the plurality of afocal variable
power optical systems comprises at least two lens groups that move
in a direction including a component perpendicular to the optical
axis of the objective lens at at least part of a section where the
magnification is changed from a high-power end state to a low-power
end state, a light shielding unit is arranged at least on the
optical axis side of the objective lens of the lens groups that
move in the direction including the component perpendicular to the
optical axis of the objective lens, the light shielding unit
blocking light passing through a space generated between the lens
groups and the optical axis of the objective lens along with the
movement of the lens groups in the direction perpendicular to the
optical axis of the objective lens.
Advantageous Effects of Invention
[0066] If the imaging optical system, the microscope apparatus, and
the stereoscopic microscope apparatus according to the present
invention are configured as described above, the enlargement of the
objective lens can be prevented, and the enlargement to the
low-power range is possible.
BRIEF DESCRIPTION OF DRAWINGS
[0067] FIG. 1 is a perspective view showing an appearance of a
parallel stereoscopic microscope apparatus.
[0068] FIG. 2 is an explanatory view showing a configuration of an
optical system of the microscope apparatus.
[0069] FIG. 3 shows lens cross-sectional views indicating an
imaging optical system of the parallel stereoscopic microscope
apparatus, (a) showing a low-power end state, (b) showing a
high-power end state.
[0070] FIG. 4 shows lens cross-sectional views indicating a
variable power optical system, (a) showing a low-power end state,
(b) showing a medium power state, and (c) showing a high-power end
state.
[0071] FIG. 5 shows explanatory views indicating arrangements of
lens groups constituting the variable power optical system at a
low-power end and a high-power end according to a first example,
(a) showing a low-power end state when a third lens group serves as
a second correction lens group, (b) showing a low-power end state
when a fourth lens group serves as the second correction lens
group, (c) showing a high-power end state.
[0072] FIG. 6 shows explanatory views indicating arrangements of
the lens groups constituting the variable power optical system at
the low-power end and the high-power end according to a second
example, (a) indicating a low-power end state when the third lens
group serves as the second correction lens group, (b) indicating a
low-power end state when the fourth lens group serves as the second
correction lens group, and (c) indicating a high-power end
state.
[0073] FIG. 7 shows explanatory views indicating arrangements of
the lens groups constituting the variable power optical system at
the low-power end and the high-power end according to a third
example, (a) showing a low-power end state when the third lens
group serves as the second correction lens group, (b) showing a
low-power end state when the fourth lens group serves as the second
correction lens group, (c) showing a low-power end state when a
fifth lens group serves as the second correction lens group, and
(d) showing a high-power end state.
[0074] FIG. 8 shows explanatory views indicating arrangements of
the lens group constituting the variable power optical system at
the low-power end and the high-power end according to a fourth
example, (a) showing a low-power end state when the third lens
group serves as the second correction lens group, (b) showing a
low-power end state when the fourth lens group serves as the second
correction lens group, (c) showing a case in which the fifth lens
group serves as the second correction lens group, (d) showing a
high-power end state.
[0075] FIG. 9 is a graph showing a relationship between an amount
of movement in an optical axis direction of the second lens group
in which a moving direction to the image side is defined as
positive and an entrance pupil position in which a direction away
from an object-side vertex of the first lens group (vertex of an
object-side surface of a lens positioned closest to the object
side) is defined as positive.
[0076] FIG. 10 is a graph showing a relationship between the amount
of movement in the optical axis direction of the second lens group,
in which the moving direction to the image side is defined as
positive, and tangent of a principal ray incidence angle entering
the variable power optical system.
[0077] FIG. 11 shows explanatory views indicating relationships
between the variable power optical system and the principal ray,
(a) showing the principal ray incidence angle, (b) showing a
principal ray incidence height.
[0078] FIG. 12 is a graph showing a relationship between the amount
of movement in the optical axis direction of the second lens group,
in which the moving direction to the image side is defined as
positive, and the principal ray incidence height.
[0079] FIG. 13 shows explanatory views for explaining the principal
ray and the principal ray incidence height, (a) showing a low-power
end state when the second and third lens groups are not decentered,
(b) showing a low-power end state when the second and third lens
groups are decentered.
[0080] FIG. 14 is a graph showing a trajectory of the second lens
group of the variable power optical system.
[0081] FIG. 15 is a graph showing a relationship of the principal
ray incidence height relative to the amount of movement in the
optical axis direction of the second lens group.
[0082] FIG. 16 shows explanatory views explaining an eye point
decentered by decentering of the second correction lens group, (a)
showing a state in which the second correction lens group is not
decentered, (b) showing a state in which the second correction lens
group is decentered, (c) showing a state in which the decentering
of the eye point based on the decentering of the second correction
lens group is corrected by decentering of a diaphragm.
[0083] FIG. 17 is an explanatory diagram for explaining a diaphragm
including an aperture section that includes the entire area in
which the diaphragm decentered by the decentering of the second
correction lens group moves.
[0084] FIG. 18 is an explanatory diagram for explaining another
embodiment in relation to a diaphragm including an aperture section
that includes the entire area in which the diaphragm decentered by
the decentering of the second correction lens group moves.
[0085] FIG. 19 shows cross-sectional views of the optical system
indicating from a conjugate image of an entrance pupil to the
diaphragm of the imaging optical system of the parallel
stereoscopic microscope apparatus, (a) showing a low-power end
state of a normal stereoscopic microscope apparatus, (b) showing a
high-power end state of the stereoscopic microscope, (c) showing a
low-power end state of a stereoscopic microscope apparatus
configured to move part of the lens groups of the variable power
optical system to reduce the distance between the optical axes on
the low-power side.
[0086] FIG. 20 is an explanatory view showing a configuration of
the stereoscopic microscope apparatus when a coaxial
epi-illumination apparatus is inserted between the objective lens
and the observation optical system.
[0087] FIG. 21 is an explanatory view showing a configuration of
the stereoscopic microscope apparatus when the coaxial
epi-illumination apparatus is inserted between the variable power
optical system and the imaging lens group inside the observation
optical system.
[0088] FIG. 22 is an explanatory view showing a configuration of an
optical system of the coaxial epi-illumination apparatus.
[0089] FIG. 23 is an explanatory view showing a trajectory of a ray
in the optical system.
[0090] FIG. 24 is a schematic diagram of the stereoscopic
microscope apparatus including light shielding units according to a
first example.
[0091] FIG. 25 shows explanatory views indicating arrangements of
the lens group constituting the light shielding units and the
variable power optical system at the low-power end and the
high-power end according to the first example, (a) showing a
high-power end state, (b) showing a low-power end state.
[0092] FIG. 26 is a schematic diagram of the stereoscopic
microscope apparatus including the light shielding units according
to a second example.
[0093] FIG. 27 shows explanatory views indicating arrangements of
the lens group constituting the light shielding units and the
variable power optical system at the low-power end and the
high-power end according to the second example, (a) showing a
high-power end state, (b) showing a low-power end state.
[0094] FIG. 28 shows diagrams indicating configurations of the
light shielding units and a movable group of the variable power
optical system according to the second example, (a) showing a
high-power end state, (b) showing a low-power end state.
[0095] FIG. 29 shows diagrams indicating configurations of the
light shielding units and the movable group of the variable power
optical system according to a modified example of the second
example, (a) showing a high-power end state, and (b) showing a
low-power end state.
[0096] FIG. 30 shows explanatory views for explaining an objective
lens numerical aperture of the parallel stereoscopic microscope
apparatus, (a) showing the entire optical system of the microscope
apparatus, (b) showing an enlarged state of main parts.
[0097] FIG. 31 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.
DESCRIPTION OF EMBODIMENTS
[0098] Hereinafter, preferred embodiments of the present invention
will be described with reference to the drawings. A configuration
of a parallel stereoscopic microscope apparatus 100 as an example
of a microscope apparatus will be described using FIGS. 1 and 2.
The parallel stereoscopic microscope apparatus 100 is a microscope
apparatus with a single-objective binocular configuration, and an
optical system of the parallel stereoscopic microscope apparatus
100 includes: an imaging optical system 5 that collects light
illuminated by a transmitted illumination apparatus not shown and
transmitted through an object O to form a first image IM of the
object O; and eyepieces 6 for enlarging and observing the first
image IM formed by the imaging optical system 5. The imaging
optical system 5 includes: an objective lens 1 that collects light
from the object O to convert the light into a luminous flux
substantially parallel to an optical axis; variable power optical
systems 3 that change an observation magnification (change the
magnification) of an image of the object O; and imaging lenses 4
that collect the light ejected from the variable power optical
systems 3 to form the first image IM. Optical systems including the
variable power optical systems 3 and the imaging lenses 4 will be
called observation optical systems 2, and the microscope apparatus
100 includes: two observation optical systems 2 in which the
optical axes extend parallel to each other; and two eyepieces
6.
[0099] The stereoscopic microscope apparatus 100 includes: a base
unit (illumination unit) 101 including a transmitted illumination
apparatus; a variable power lens barrel 103 provided with the
objective lens 1 and the eyepieces 6 and including the variable
power optical systems 3 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 1 is
attached to an objective lens attachment unit 106 provided below
the variable 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 can be selected and attached in
some cases, and a plurality of lenses among the plurality of
predetermined low-power objective lenses and high-power objective
lenses are selected and attached in other cases.
[0100] The variable power optical systems 3 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 optical systems 3 include movable
lens groups, and as the variable power knob 107 is rotated, the
movable lens groups move in an optical axis direction in accordance
with a predetermined amount of movement. The variable power optical
systems 3 include adjustable diaphragms, and an adjustment
mechanism (not shown) 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
optical axis along with the rotation of the focusing knob 108.
Binocular lens barrels 104 including imaging lenses 4 and eyepieces
6 are attached above the variable power lens barrel 103. The
imaging lenses 4 arranged on the left and right collect the
parallel light exited from the variable power optical systems 3 for
left and right eyes to temporarily form the first image IM of the
object, and the eyepieces 6 attached to upper end sections of the
binocular lens barrels 104 can be used to observe the formed first
image IM by left and right naked eyes.
[0101] In the case illustrated in FIGS. 3 and 4, the variable power
optical system 3 includes four lens groups in total, a first lens
group G1 having positive refractive power, a second lens group G2
having negative refractive power, a third lens group G3 having
positive refractive power, and a fourth lens group G4 having
negative refractive power, in order from the object O 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 to the high-power end state. Therefore, the
second lens group G2 and the third lens group G3 are configured 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.
[0102] In the stereoscopic microscope apparatus 100, as described
using FIG. 31, the maximum diameter of the light passing through
the objective lens 1 when the variable power optical system 3 is in
a low-power end state is greater than the maximum diameter of the
light passing through the objective lens 1 in a high-power end
state. More specifically, a peripheral part of the lens
constituting the objective lens 1 is not used during high-power and
is only used during low-power. On the other hand, the maximum
diameter of the light entering the variable power optical system 3
when the variable power optical system 3 is in the high-power end
state is greater than the maximum diameter of the light entered in
the low-power end state. Therefore, in the microscope apparatus 100
according to the present embodiment, the entrance pupil is brought
close to the optical axis of the objective lens 1 to reduce the
diameter of the luminous flux passing through the objective lens 1
on the low-power end side. In other words, as shown in FIG. 3, at
least one of the lens groups constituting the variable power
optical system 3 is moved in a direction including a component
perpendicular to the optical axis during the change in the
magnification (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 as a reference of the power optical system 3 (for
example, an optical axis of a lens group (for example, the first
lens group G1) fixed during the change in the magnification among
the lens groups included in the variable power optical system 3,
and the optical axis will be called a "reference optical axis A").
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. 3 and 4, the second lens group G2 for which the
magnification is changed by the movement along the optical axis
during the change in the magnification serves as the first
correction lens group CG1.
[0103] As described, FIG. 3 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 (observation optical systems 2). In
the variable power lens group 3, some of the lens groups on the
object O 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. In this zoom type, as
shown in FIG. 4(a), the second lens group G2 (the first correction
lens group CG1) is moved to the object side when the magnification
is changed to the low-power end side (when the magnification is
changed), and the second lens group G2 is decentered so that the
optical axis of the second lens group G2 is positioned at a
position deviated from the reference optical axis A. More
specifically, the first correction lens group CG1 (second lens
group G2) is moved to reduce the distance between the optical axes
of the left and right variable power optical systems 3 (bring close
to the optical axis of the objective lens 1). The left and right
pupils are brought close to the optical axis of the objective lens
1 by moving the first correction lens group CG1 during the change
in the magnification. Therefore, the ray at the peripheral part
among the rays passing through the objective lens 1 approaches the
optical axis of the objective lens 1. As a whole, the maximum
diameter of the light passing through the objective lens 1 is
reduced, and the diameter of the objective lens 1 is reduced and
miniaturized. In other words, even if the low-power range is
enlarged, this can be realized by the size of the diameter of the
conventional objective lens. The maximum diameter of the light
entering the variable power optical system 3 is smaller during
low-power than during high-power. Therefore, even if the first
correction lens group CG1 (second lens group G2) is decentered, the
luminous flux can be set within the lens effective diameter
(maximum diameter that the light can enter) of the first lens group
G1. In the present embodiment, the first lens group G1 and the
fourth lens group G4 are fixed in a power changing operation.
[0104] It is desirable in the microscope apparatus 100 that the
variable power optical system 3 is an afocal variable power optical
system that changes the magnification of the diameter of the
entered parallel luminous flux to eject the flux as a parallel
luminous flux (afocal luminous flux). Therefore, to ultimately
cause the variable power optical system 3 to eject the afocal
luminous flux, the deviation of the ejected luminous flux from the
parallel luminous flux after the change in the optical path in the
variable power optical system 3 caused by the decentering of the
second lens group G2 (first correction lens group CG1) needs to be
corrected by moving at least one of the other lens groups in the
direction including a component perpendicular to the optical axis
(the lens group will be called a "second correction lens group
CG2"). More specifically, the second correction lens group CG2
needs to be decentered to correct the optical path changed by the
first correction lens group CG1 to eject light to form an image at
an image forming position where the image would be formed when lens
groups constituting the variable power optical system 3 are
arranged to match the optical axes. In the variable power optical
system 3 shown in FIG. 4, the third lens group G3 with positive
refractive power is used as the second correction lens group CG2.
Therefore, in the low-power end state, the third lens group G3 is
decentered in the same direction as the second lens group G2
relative to the reference optical axis A (optical axis of the first
lens group G1). The amount of decentering of the third lens group
G3 can be uniquely determined from the amount of decentering of the
second lens group G2. When the fourth lens group G4 with negative
refractive power is set as the second correction lens group CG2,
decentering in the opposite direction of the second lens group G2
is needed. The second correction lens group CG2 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, may be at least one of the lens groups not moved
along the optical axis during the change in the magnification, or
may be both.
[0105] The diameter of the luminous flux entering the variable
power optical system 3 is the largest during the highest power.
Therefore, as shown in FIG. 4(c), it is desirable that the optical
axes of all lens groups included in the variable power optical
system 3 (first to fourth lens groups G1 to G4) substantially
coincide (substantially coincide with the reference optical axis A)
to effectively use the entrance pupil of the variable power optical
system 3 during the highest power of the variable power optical
system 3.
[0106] The variable power optical system 3 shown in FIG. 3
illustrates a case in which the first lens group G1 has positive
refractive power, and the second lens group G2 (first correction
lens group CG1) has negative refractive power. Subsequently, there
is a continuation to the lens groups, the imaging lens, and the
eyepiece following the third lens group not shown in FIG. 3 in the
variable power optical system 3, and the image is observed by the
left eye and the right eye. The optical path diagrams shown in FIG.
3 illustrate configurations with substantially the same numerical
apertures as the conventional optical system shown in FIG. 31. As
described, during the highest power of the variable power optical
system 3 shown in FIG. 3(b), it is desirable that the optical axes
of all lens groups match (on the line parallel to the optical axis
of the objective lens 1) to effectively use the entrance pupil of
the variable power optical system 3. Therefore, the optical path
diagram is the same as FIG. 31(b). The following Table 1 shows data
of the objective lens 1 shown in FIG. 3. In Table 1, m denotes a
plane number of an optical plane counted from the object O side, r
denotes a radius of curvature of each optical plane, d denotes a
distance (spacing) on the optical axis from each optical plane to
the next optical plane, nd denotes a reflective index relative to a
d line, and vd denotes an Abbe number. In the following Table 1, a
refractive index 1.00000 of air is not indicated. A unit "mm" is
usually used for the radius of curvature, the spacing, and other
lengths described in all data below. However, a similar optical
performance of the optical system can be obtained after
proportional enlargement or proportional reduction, and the unit is
not limited to this (the same applies to the following data
tables).
TABLE-US-00001 TABLE 1 m r d nd .nu.d 1 -249.743 4.900 1.49782
82.50 2 -66.680 0.500 3 -1600.580 17.900 1.43426 94.85 4 -24.560
4.000 1.71300 53.87 5 -62.490 0.500 6 206.782 15.400 1.49782 82.50
7 -49.681 0.800 8 38.548 15.150 1.43426 94.85 9 107.188 4.000
1.51680 64.11 10 33.123 9.050 11 188.057 15.100 1.56907 71.31 12
-28.609 4.900 1.73400 51.47 13 -85.550
[0107] In the microscope apparatus 100 with the configuration, the
distance between the optical axes of the pair of variable power
optical systems 3 arranged after the ejection from the objective
lens 1 is about 16 mm at the lowest power, and if the amount of
decentering of the second lens group G2 (first correction lens
group CG1) is 3 mm, the distance between the optical axes is about
22 mm at the highest power. In this way, it can be recognized from
FIG. 3 that the objective lens 1 is miniaturized while the same
variable power range is maintained.
Examples of Variable Power Optical System
[0108] Hereinafter, specific examples of configurations of the
variable power optical system 3 according to the present embodiment
will be described. Although the lens actually has a thickness, only
the behavior of the ray entering the lens and the ray ejected from
the lens can be considered as an effect of the lens, and a
replacement to a thin lens with a thickness that can be ignored is
theoretically possible. Particularly, since the number of lens
groups is small in the variable power optical system, approximation
to the thin lens is easy. It is typical to replace the lens groups
by thin lenses to determine the optimal focal length and the
arrangement of the lens groups in accordance with the
specifications. In accordance with the example, each lens group is
replaced by a piece of thin lens in the variable power optical
system 3 in the following description.
First Example
[0109] FIG. 5 shows one of the typical variable power optical
systems 3 with a 4-group configuration including, in order from the
object side, the first lens group G1 with positive refractive
power, the second lens group G2 with negative refractive power, the
third lens group G3 with positive refractive power, and the fourth
lens group G4 with negative refractive power. During the change in
the magnification from the low-power end state to the high-power
end state, 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. Therefore, the second lens group G2 and the third lens group
G3 always move only in certain directions and do not move in
reverse directions in the middle of the power changing
operation.
[0110] In this zoom type, the second lens group G2 is set as the
first correction lens group CG1, and when the magnification is
changed to the low-power side as shown in FIG. 5, the second lens
group G2 is moved to the object side and decentered to reduce the
distance between the optical axes in the two variable power optical
systems 3. As described, the first lens group G1 is fixed in the
power changing operation, and the movement of the lens groups on
the same optical axis as the first lens group G1 is not related to
the decentering correction and will not be described (optical axis
of the first lens group G1 serves as the "reference optical
axis").
[0111] To ultimately eject the light from the variable power
optical system 3 as an afocal luminous flux, a lens group different
from the second lens group G2 needs to be used as the second
correction lens group CG2 for the correction. As shown by an arrow
of FIG. 5(a), in the correction by the third lens group G3 with
positive refractive power, the third lens group G3 needs to be
decentered in the same direction as the second lens group G2. The
amount of decentering can be uniquely determined from the amount of
decentering of the second lens group G2. Specifically, in
accordance with the change in the magnification to the high-power
side, the second lens group G2 approaches the optical axis of the
first lens group G1 while moving to the image side (decentering
movement). Meanwhile, the third lens group G3 approaches the
optical axis of the first lens G1 while moving to the object
side.
[0112] Alternatively, as shown by an arrow of FIG. 5(b), when the
fourth lens group G4 with negative refractive power serves as the
second correction lens group CG2 in the correction, the fourth lens
group G4 needs to be decentered in the opposite direction of the
second lens group G2. The amount of decentering can be uniquely
determined from the amount of decentering of the second lens group
G2. Specifically, in accordance with the change in the
magnification to the high-power side, the second lens group G2
approaches the optical axis of the first lens group G1 while moving
to the image side (decentering movement). Meanwhile, the fourth
lens group G4 does not move in the optical axis direction (only
moves in the vertical direction relative to the optical axis), but
approaches the optical axis of the first lens G1.
[0113] The following Table 2 shows data of the variable power
optical system 3 according to the first example. In Table 2, .beta.
denotes a magnification, f1 denotes a focal length of the first
lens group G1, f2 denotes a focal length of the second lens group
G2, f3 denotes a focal length of the third lens group G3, and f4
denotes a focal length of the fourth lens group G4. Furthermore, d1
denotes a distance between the first lens group G1 and the second
lens group G2 on the optical axis, d2 denotes a distance between
the second lens group G2 and the third lens group G3 on the optical
axis, and d3 denotes a distance between the third lens group G3 and
the fourth lens group G4 on the optical axis. Furthermore,
.epsilon.(G2) denotes an amount of decentering of the second lens
group G2, .epsilon. (G3) denotes an amount of decentering of the
third lens group G3, and .epsilon.(G4) denotes an amount of
decentering of the fourth lens group G4. Upward in the drawings is
indicated as positive for the amount of decentering. The
description of the data table is the same in the following second
example.
TABLE-US-00002 TABLE 2 .beta. = 20x f1 = 88.3 f2 = -20.7 f3 = 51.7
f4 = -55 Low-Power End High-Power End d1 4.0618 57.45 d2 131.7041
21.86519 d3 21.5341 77.9848 Amount of Decentering in Correction by
G3 .epsilon. (G2) -3 0 .epsilon. (G3) -1.2934 0 Amount of
Decentering in Correction by G4 .epsilon. (G2) -3 0 .epsilon. (G4)
1.91325 0
In the correction by both the third lens group G3 with positive
refractive power and the fourth lens group G4 with negative
refractive power, the amounts of decentering of both correction
groups are not uniquely determined. In that case, although the
design freedom improves, the mechanism is complicated.
Second Example
[0114] FIG. 6 shows one of the typical variable power optical
systems with a 4-group configuration including, in order from the
object side, the first lens group G1 with positive refractive
power, the second lens group G2 with negative refractive power, the
third lens group G3 with negative refractive power, and the fourth
lens group G4 with positive refractive power. During the change in
the magnification from the low-power end state to the high-power
end state, the second lens group G2 moves in a certain direction
from the object side to the image side. Meanwhile, the third lens
group G3 moves in a certain direction from the object side to the
image side based on the power arrangement of the variable power
optical system 3 in some cases and reverses in the middle of the
power changing operation to ultimately move to the image side in
other cases.
[0115] In this zoom type, the second lens group G2 is set as the
first correction lens group CG1, and when the magnification is
changed to the low-power side as shown in FIG. 6, the second lens
group G2 is moved to the object side and decentered to reduce the
distance between the optical axes in the two variable power optical
systems 3. The first lens group G1 is also fixed in the power
changing operation in the second example, and the optical axis of
the first lens group G1 serves as the "reference optical axis".
[0116] To ultimately eject the light from the variable power
optical system 3 as an afocal luminous flux, a lens group different
from the second lens group G2 needs to be used as the second
correction lens group CG2 for the correction. As shown by an arrow
of FIG. 6(a), in the correction by the third lens group G3 with
negative refractive power, the third lens group G3 needs to be
decentered in the opposite direction of the second lens group G2.
The amount of decentering can be uniquely determined from the
amount of decentering of the second lens group G2. Specifically, in
accordance with the change in the magnification to the high-power
side, the second lens group G2 approaches the optical axis of the
first lens group G1 while moving to the image side (decentering
movement). Meanwhile, the third lens group G3 approaches the
optical axis of the first lens group G1 while moving to the object
side in some cases and reverses the direction in the middle of the
power changing operation to ultimately approach the optical axis of
the first lens group G1 while moving to the image side in other
cases.
[0117] Alternatively, as shown by an arrow of FIG. 6(b), when the
fourth lens group G4 with positive refractive power serves as the
second correction lens group CG2 in the correction, the fourth lens
group G4 needs to be decentered in the same direction as the second
lens group G2. The amount of decentering can be uniquely determined
from the amount of decentering of the second lens group G2.
Specifically, in accordance with the change in the magnification to
the high-power side, the second lens group G2 approaches the
optical axis of the first lens group G1 while moving to the image
side (decentering movement). Meanwhile, the fourth lens group G4
does not move in the optical axis direction (only moves in the
vertical direction relative to the optical axis), but approaches
the optical axis of the first lens group G1.
[0118] The following Table 3 shows data of the variable power
optical system 3 according to the second example.
TABLE-US-00003 TABLE 3 .beta. = 20x f1 = 107.96 f2 = -32.23 f3 =
-70.44 f4 = 110.86 Low-Power End High-Power End d1 27.8043 79 d2
51.8816 68 d3 70.3141 3 Amount of Decentering in Correction by G3
.epsilon. (G2) -3 0 .epsilon. (G3) 3.2507 0 Amount of Decentering
in Correction by G4 .epsilon. (G2) -3 0 .epsilon. (G4) -1.91619
0
[0119] In the correction by both the third lens group G3 with
negative refractive power and the fourth lens group G4 with
positive refractive power, the amounts of decentering of both
correction groups are not uniquely determined. In that case,
although the design freedom improves, the mechanism is
complicated.
Third Example
[0120] FIG. 7 shows a variable power optical system with a 5-group
configuration additionally provided with a new lens group with
negative refractive power between the second lens group G2 and the
third lens group G3 shown in FIG. 5 (the new lens group will be
referred to as G3 which is followed by G4 and G5). The newly added
third lens group G3 may be configured to move along the optical
axis in the power changing operation or may be fixed.
[0121] In this zoom type, the second lens group G2 is set as the
first correction lens group CG1, and when the magnification is
changed to the low-power side as shown in FIG. 7, the second lens
group G2 is moved to the object side along the optical axis and
decentered to reduce the distance between the optical axes in the
two variable power optical systems 3. The first lens group G1 is
also fixed in the power changing operation in the third example,
and the optical axis of the first lens group G1 serves as the
"reference optical axis".
[0122] To ultimately eject the light from the variable power
optical system 3 as an afocal luminous flux, a lens group different
from the second lens group G2 needs to be used as the second
correction lens group CG2 for the correction. As shown by an arrow
of FIG. 7(a), in the correction by the third lens group G3 with
negative refractive power, the third lens group G3 needs to be
decentered in the opposite direction of the second lens group G2.
The amount of decentering can be uniquely determined from the
amount of decentering of the second lens group G2. Specifically, in
accordance with the change in the magnification to the high-power
side, the second lens group G2 approaches the optical axis of the
first lens group G1 while moving to the image side (decentering
movement). Meanwhile, in some cases the third lens group G3
approaches the optical axis of the first lens group G1 without
moving in the optical axis direction (but moving in the vertical
direction relative to the optical axis), and in other cases the
third lens group G3 approaches the optical axis of the first lens
group G1 while moving to the image side or the object side.
[0123] Alternatively, as shown by an arrow of FIG. 7(b), when the
fourth lens group G4 with positive refractive power serves as the
second correction lens group CG2 in the correction, the fourth lens
group G4 needs to be decentered in the same direction as the second
lens group G2. The amount of decentering can be uniquely determined
from the amount of decentering of the second lens group G2.
Specifically, in accordance with the change in the magnification to
the high-power side, the second lens group G2 approaches the
optical axis of the first lens group G1 while moving to the image
side (decentering movement). Meanwhile, the fourth lens group G4
approaches the optical axis of the first lens group G1 while moving
to the object side (decentering movement).
[0124] Alternatively, as shown by an arrow of FIG. 7(c), when the
fifth lens group G5 with negative refractive power serves as the
second correction lens group CG2 in the correction, the fifth lens
group G5 needs to be decentered in the opposite direction of the
second lens group G2. The amount of decentering can be uniquely
determined from the amount of decentering of the second lens group
G2. Specifically, in accordance with the change in the
magnification to the high-power side, the second lens group G2
approaches the optical axis of the first lens group G1 while moving
to the image side (decentering movement). Meanwhile, the fifth lens
group G5 does not move in the optical axis direction (only moves in
the vertical direction relative to the optical axis), but
approaches the optical axis of the first lens group G1. The amounts
of decentering of the correction groups are not uniquely determined
in the correction by at least two or more groups among the third
lens group G3 with negative refractive power, the fourth lens group
G4 with positive refractive power, and the fifth lens group G5 with
negative refractive power. In that case, although the design
freedom improves, the mechanism is complicated.
[0125] The following Table 4 shows data of the variable power
optical system 3 according to the third example. In Table 4, .beta.
denotes a magnification, f1 denotes a focal length of the first
lens group G1, f2 denotes a focal length of the second lens group
G2, f3 denotes a focal length of the third lens group G3, f4
denotes a focal length of the fourth lens group G4, and f5 denotes
a focal length of the fifth lens group G5. Furthermore, d1 denotes
a distance between the first lens group G1 and the second lens
group G2 on the optical axis, d2 denotes a distance between the
second lens group G2 and the third lens group G3 on the optical
axis, d3 denotes a distance between the third lens group G3 and the
fourth lens group G4 on the optical axis, and d4 denotes a distance
between the fourth lens group and the fifth lens group on the
optical axis. Furthermore, .epsilon.(G2) denotes an amount of
decentering of the second lens group, .epsilon.(G3) denotes an
amount of decentering of the third lens group G3, .epsilon.(G4)
denotes an amount of decentering of the fourth lens group G4, and
.epsilon.(G5) denotes an amount of decentering of the fifth lens
group G5. Upward in the drawings is indicated as positive for the
amount of decentering. The description of the data table is the
same in the following fourth example.
TABLE-US-00004 TABLE 4 .beta. = 20x f1 = 76.8 f2 = -42.2 f3 = -37.9
f4 = 44.1 f5 = -84.1 Low-Power End High-Power End d1 3 47 d2 45 1
d3 59 1.1628 d4 3 60.8 Amount of Decentering in Correction by G3
.epsilon. (G2) -3 0 .epsilon. (G3) 1.847 0 Amount of Decentering in
Correction by G4 .epsilon. (G2) -3 0 .epsilon. (G4) -0.73312 0
Amount of Decentering in Correction by G5 .epsilon. (G2) -3 0
.epsilon. (G5) 1.44487 0
[0126] During the change in the magnification to the high-power
side, not only the second lens group G2, but also the third lens
group G3 approaches the optical axis of the first lens group G1
together relative to the first lens group G1. When the second lens
group G2 and the third lens group G3 serve as the first correction
lens group CG1, a lens group other than the second lens group G2
and the third lens group G3 needs to be used as the second
correction lens group CG2 for the correction to ultimately eject
the light from the variable power optical system 3 as an afocal
luminous flux.
[0127] When the fourth lens group G4 with positive refractive power
serves as the second correction lens group CG2 in the correction,
the fourth lens group G4 needs to be decentered in the same
direction as the second lens group G2 and the third lens group G3.
The amount of decentering can be uniquely determined from the
amounts of decentering of the second lens group G2 and the third
lens group G3. Specifically, as the magnification is changed to the
high-power side, the second lens group G2 approaches the optical
axis of the first lens group G1 while moving to the image side
(decentering movement). In some cases the third lens group G3
approaches the optical axis of the first lens group G1 without
moving in the optical axis direction (but moving in the vertical
direction relative to the optical axis), and in other cases the
third lens group G3 approaches the optical axis of the first lens
group G1 while moving to the image side or the object side.
Meanwhile, the fourth lens group G4 approaches the optical axis of
the first lens group G1 while moving to the object side
(decentering movement).
[0128] Alternatively, when the fifth lens group G2 with negative
refractive power serves as the second correction lens group CG2 in
the correction, the fifth lens group G5 needs to be decentered in
the opposite direction of the second lens group G2 and the third
lens group G3. The amount of decentering can be uniquely determined
from the amounts of decentering of the second lens group G2 and the
third lens group G3. Specifically, as the magnification is changed
to the high-power side, the second lens group G2 approaches the
optical axis of the first lens group G1 while moving to the image
side (decentering movement). In some cases the third lens group G3
approaches the optical axis of the first lens group G1 without
moving in the optical axis direction (but moving in the vertical
direction relative to the optical axis), and in other cases the
third lens group G3 approaches the optical axis of the first lens
group G1 while moving to the image side or the object side
(decentering movement). Meanwhile, the fifth lens group G5 does not
move in the optical axis direction (only moves in the vertical
direction relative to the optical axis), but approaches the optical
axis of the first lens group G1. In the correction by both the
fourth lens group G4 with positive refractive power and the fifth
lens group G5 with negative refractive power, the amounts of
decentering of both correction groups are not uniquely determined.
In that case, although the design freedom improves, the mechanism
is complicated.
Fourth Example
[0129] FIG. 8 shows a variable power optical system with a 5-group
configuration additionally provided with a new lens group with
positive refractive power between the second lens group G2 and the
third lens group G3 shown in FIG. 6 (the new lens group will be
referred to as G3 which is followed by G4 and G5). The newly added
third lens group G3 may be configured to move along the optical
axis in the power changing operation or may be fixed.
[0130] In this zoom type, the second lens group G2 is set as the
first correction lens group CG1, and when the magnification is
changed to the low-power side as shown in FIG. 8, the second lens
group G2 is moved to the object side along the optical axis and
decentered to reduce the distance between the optical axes in the
two variable power optical systems 3. The first lens group G1 is
also fixed in the power changing operation in the fourth example,
and the optical axis of the first lens group G1 serves as the
"reference optical axis".
[0131] To ultimately eject the light from the variable power
optical system 3 as an afocal luminous flux, a lens group different
from the second lens group G2 needs to be used as the second
correction lens group CG2 for the correction. As shown by an arrow
of FIG. 8(a), in the correction by the third lens group G3 with
positive refractive power, the third lens group G3 needs to be
decentered in the same direction as the second lens group G2. The
amount of decentering can be uniquely determined from the amount of
decentering of the second lens group G2. Specifically, in
accordance with the change in the magnification to the high-power
side, the second lens group G2 approaches the optical axis of the
first lens group G1 while moving to the image side (decentering
movement). Meanwhile, in some cases the third lens group G3
approaches the optical axis of the first lens group G1 without
moving in the optical axis direction (but moving in the vertical
direction relative to the optical axis), and in other cases the
third lens group G3 approaches the optical axis of the first lens
group G1 while moving to the image side or the object side.
[0132] Alternatively, as shown by an arrow of FIG. 8(b), when the
fourth lens group G4 with negative refractive power serves as the
second correction lens group CG2 in the correction, the fourth lens
group G4 needs to be decentered in the opposite direction of the
second lens group G2. The amount of decentering can be uniquely
determined from the amount of decentering of the second lens group
G2. Specifically, in accordance with the change in the
magnification to the high-power side, the second lens group G2
approaches the optical axis of the first lens group G1 while moving
to the image side (decentering movement). Meanwhile, the fourth
lens group G4 approaches the optical axis of the first lens group
G1 while moving to the object side (decentering movement).
[0133] Alternatively, as shown by an arrow of FIG. 8(c), when the
fifth lens group G5 with positive refractive power serves as the
second correction lens group CG2 in the correction, the fifth lens
group G5 needs to be decentered in the same direction as the second
lens group G2. The amount of decentering can be uniquely determined
from the amount of decentering of the second lens group G2.
Specifically, in accordance with the change in the magnification to
the high-power side, the second lens group G2 approaches the
optical axis of the first lens group G1 while moving to the image
side (decentering movement). Meanwhile, the fifth lens group G5
does not move over the optical axis (only moves in the vertical
direction relative to the optical axis), but approaches the optical
axis of the first lens group G1. The amounts of decentering of the
correction groups are not uniquely determined in the correction by
at least two or more groups among the third lens group G3 with
positive refractive power, the fourth lens group G4 with negative
refractive power, and the fifth lens group G5 with positive
refractive power. In that case, although the design freedom
improves, the mechanism is complicated. The following Table 5 shows
data of the variable power optical system 3 according to the fourth
example.
TABLE-US-00005 TABLE 5 .beta. = 20x f1 = 103.6066 f2 = -21.44 f3 =
83.547 f4 = -82.5 f5 = 133.03 Low-Power End High-Power End d1
16.2154 77 d2 63.7846 3 d3 26.6432 67 d4 43.3577 3 Amount of
Decentering in Correction by G3 .epsilon. (G2) -3 0 .epsilon. (G3)
-3.60856 0 Amount of Decentering in Correction by G4 .epsilon. (G2)
-3 0 .epsilon. (G4) 3.64982 0 Amount of Decentering in Correction
by G5 .epsilon. (G2) -3 0 .epsilon. (G5) -3.9912 0
[0134] During the change in the magnification to the high-power
side, not only the second lens group G2, but also the third lens
group G3 approaches the optical axis of the first lens group G1
together relative to the first lens group G1. When the second lens
group G2 and the third lens group G3 serve as the first correction
lens group CG1, a lens group other than the second lens group G2
and the third lens group G3 needs to be set as the second
correction lens group CG2 for the correction to ultimately eject
the light from the variable power optical system 3 as an afocal
luminous flux.
[0135] When the fourth lens group G4 with negative refractive power
serves as the second correction lens group CG2 in the correction,
the fourth lens group G4 needs to be decentered in the opposite
direction of the second lens group G2 and the third lens group G3.
The amount of decentering can be uniquely determined from the
amounts of decentering of the second lens group G2 and the third
lens group G3. Specifically, as the magnification is changed to the
high-power side, the second lens group G2 approaches the optical
axis of the first lens group G1 while moving to the image side
(decentering movement). In some cases the third lens group G3
approaches the optical axis of the first lens group G1 without
moving in the optical axis direction (but moving in the vertical
direction relative to the optical axis), and in other cases the
third lens group G3 approaches the optical axis of the first lens
group G1 while moving to the image side or the object side
(decentering movement). Meanwhile, the fourth lens group G4
approaches the optical axis of the first lens group G1 while moving
to the image side (decentering movement).
[0136] Alternatively, when the fifth lens group G5 with positive
refractive power serves as the second correction lens group CG2 in
the correction, the fifth lens group G5 needs to be decentered in
the same direction as the second lens group G2 and the third lens
group G3. The amount of decentering can be uniquely determined from
the amounts of decentering of the second lens group G2 and the
third lens group G3. Specifically, as the magnification is changed
to the high-power side, the second lens group G2 approaches the
optical axis of the first lens group G1 while moving to the image
side (decentering movement). The third lens group G3 does not move
in the optical axis direction (only moves in the vertical direction
relative to the optical axis). In some cases the third lens group
G3 approaches the optical axis of the first lens group G1 without
moving in the optical axis direction (but moving in the vertical
direction relative to the optical axis), and in other cases the
third lens group G3 approaches the optical axis of the first lens
group G1 while moving to the image side or the object side
(decentering movement). In the correction by both the fourth lens
group G4 with negative refractive power and the fifth lens group G5
with positive refractive power, the amounts of decentering of the
correction groups are not uniquely determined. In that case,
although the design freedom improves, the mechanism is
complicated.
[0137] The foregoing are typical zoom types of the variable power
optical system used in the parallel stereoscopic microscope
apparatus 100 and examples of the zoom types. As described, it is
desirable if the optical axes of all lens groups coincide at the
highest power of the variable optical system 3 (the optical axes
are on a line parallel to the optical axis of the objective lens 1)
because the entrance pupil of the variable power optical system 3
is larger than when part of the lens groups is decentered at the
highest power. Other than the examples described above, there are
countless solutions for decentering the optical axis while
maintaining the afocal variable power optical system by increasing
the movable groups in the variable power optical system 3 or
changing the combination of the lens groups to be decentered to
complicate the movements of the decentering correction groups.
However, the solutions can be easily imagined from the description,
and the solutions are considered to be included in the present
invention.
Trajectory during Change in Magnification of Variable Power Optical
System
[0138] If the incident position is a position away from the optical
axis when a ray with a large angle .theta.' enters the object-side
surface of the lens arranged closest to the object of the variable
power optical system 3' in FIG. 31, the ray approaches the aperture
radius of the lens. This leads to a reduction in the amount of
ambient light and causes a reduction in the amount of light.
Therefore, a configuration of the imaging optical system 5,
specifically, the variable power optical system 3, with controlled
reduction in the amount of light during the change in the
magnification will be described.
[0139] Hereinafter, a case in which the variable power optical
system 3 includes lens data shown in Table 6 will be described. In
Table 6, f1 denotes a focal length of the first lens group G1, f2
denotes a focal length of the second lens group G2, f3 denotes a
focal length of the third lens group G3, and f4 denotes a focal
length of the fourth lens group G4. Furthermore, d1 denotes a
distance between principal points of the first lens group G1 and
the second lens group G2, d2 denotes a distance between principal
points of the second lens group G2 and the third lens group G3, d3
denotes a distance between principal points of the third lens group
G3 and the fourth lens group G4, and f denotes a combined focal
length between the variable power optical system 3 and an imaging
lens group not shown. Table 6 shows values in a low-power end
state, a medium power state, and a high-power end state for each.
The magnification of the variable power optical system 3 is 25
times, and the focal length of the imaging lens is 200 mm. 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 when the magnification is changed from the
low-power end state to the high-power end state.
TABLE-US-00006 TABLE 6 f1 = 88.423 f2 = -20.702 f3 = 51.711 f4 =
-55.136 Low-Power End Medium Power High-Power End d1 4.08 47.02
58.69 d2 131.80 62.02 13.86 d3 21.44 48.29 84.77 f 50.40 322.18
1259.33
[0140] In general, the trajectories of the movable groups
constituting the variable power optical system during the change in
the magnification are uniquely determined from focal lengths of the
groups and intervals between principal points at a predetermined
magnification in the variable power range. First, a case in which
the variable power optical system 3 is not decentered during the
change in the magnification (the second lens group G2 and the third
lens group G3 move only along the optical axes) will be
described.
[0141] As shown in FIG. 9, if the second lens group G2 is moved
from the low-power end state to the high-power end state along the
optical axis, the distance from an object-side vertex of the first
lens group G1 (vertex of the object-side surface of the lens
positioned closest to the object) to an entrance pupil plane
(entrance pupil position) increases. The amount of movement in the
optical axis direction of the second lens group G2 in FIG. 9 is
indicated by setting the low-power end state as 0 and setting the
direction moving toward the high-power end side as positive. The
same applies to other drawings. As shown in FIG. 10, tangent (tan
.theta.) of an angle (principal ray incidence angle) .theta.
relative to the reference optical axis A of a principal ray
entering the variable power optical system 3 relative to the amount
of movement in the optical axis direction of the second lens group
G2 decreases as the magnification is changed from the low-power end
state to the high-power end state, and the amount of change also
decreases. As shown in FIG. 11(a), the principal ray in FIG. 10 is
a principal ray (hereinafter, called "principal ray m") with the
largest angle (principal ray incidence angle .theta.) entering the
variable power optical system 3 (first lens group G1) among the
principal rays passing through the center of the diaphragm S of the
variable power optical system 3.
[0142] Assuming that the distance between the position where the
principal ray m enters the tangent plane passing through the vertex
on the optical axis of the first lens group G1 and the reference
optical axis A (incidence height of the principal ray m relative to
the tangent plane of the first lens group G1, hereinafter called
"principal ray incidence height") is h as shown in FIG. 11(b), the
principal ray incidence height h can be calculated by a product of
the distance from the object-side vertex of the first lens group G1
to the entrance pupil and the tangent of the principal ray
incidence angle .theta. entering the variable power optical system
3. The principal ray incidence height h relative to the amount of
movement in the optical axis direction of the second lens group G2
changes as shown in FIG. 12. More specifically, during the change
in the magnification from the low-power end state to the high-power
end state, the height first increases in a direction away from the
optical axis and then approaches the optical axis direction after a
predetermined amount of movement in the optical axis direction and
decreases.
[0143] Meanwhile, if the first correction lens group CG1 (second
lens group G2) is decentered during the change in the magnification
as shown in FIG. 13(b) in the variable power optical system 3, the
principal ray incidence height becomes larger than the principal
ray incidence height h without decentering shown in FIG. 13(a)
(incident position of the principal ray to the tangent plane of the
first lens group G1 moves away from the optical axis). As a result,
the incident position of the principal ray m to the tangent plane
of the first lens group G1 approaches the aperture radius of the
first lens group G1, and the amount of ambient light is
reduced.
[0144] Therefore, to prevent the reduction in the amount of ambient
light, it is necessary to select the trajectory during the change
in the magnification of the second lens group G2 so that the
tangent plane incident position of the first lens group G1 of the
principal ray m is not too apart from the reference optical axis A.
As described, the principal ray incidence height h temporarily
increases and then decreases when the magnification is changed from
the low-power end state (at the lowest power) to the high-power end
side in the variable power optical system 3. Meanwhile, the second
lens group G2 (first correction lens group CG1) is decentered to
the greatest extent from the reference optical axis A in the
low-power end state (at the lowest power), and as the magnification
is changed to the high-power end side, the second lens group G2
moves to coincide with the reference optical axis A. The optical
axes of all lens groups G1 to G4 substantially match in the
high-power end state (at the highest power). Therefore, the amount
of change in the amount of movement to the reference optical axis A
side of the second lens group G2 (amount of change in the amount of
movement in the direction perpendicular to the reference optical
axis A) is increased in the low-power end side to control the
increase in the principal ray incidence height h on the low-power
end side during the change in the magnification.
[0145] Specifically, as shown in FIG. 14, when the amount of
movement in the optical axis direction of the second lens group G2
is set as X, and the amount of movement in the direction
perpendicular to the reference optical axis A (amount of movement
in the perpendicular direction) is set as Y in the plane including
the reference optical axis A of the variable power optical system 3
and the optical axis of the objective lens 1 to express the
trajectory during the change in the magnification of the second
lens group G2 (amount of movement Y in the perpendicular direction)
as a function of the amount of movement X in the optical axis
direction, the trajectory is constituted to satisfy a condition in
which a first derivative of the function Y by X is 0 or more at at
least part of the section of the variable power range, and a second
derivative is 0 or less. In the function, the direction away from
the reference optical axis A is defined as a negative direction
(direction in which the optical axis is 0, and values away from the
optical axis are negative) for the amount of movement Y in the
perpendicular direction, and the direction moving toward the image
is defined as a positive direction (direction in which the
low-power end state (at the lowest power) is 0, and the value
increases toward the high-power end side) for the amount of
movement X in the optical axis direction.
[0146] If the first derivative of the trajectory (function Y)
during the change in the magnification of the second lens group G2
is negative, the incident position of the principal ray m to the
tangent plane of the first lens group G1 is farther away from the
reference optical axis A when the magnification is changed from the
low-power end state (at the lowest power) to the high-power end
side regardless of the result of the second derivative. Therefore,
the ray approaches the aperture radius of the first lens group G1,
and the amount of ambient light decreases. If the first derivative
of the trajectory (function Y) is 0 or more in the variable power
range, and the second derivative is positive, it is difficult to
cancel the increase in the incidence height h of the principal ray
m to the tangent plane of the first lens group G1 in association
with the change in the magnification by the amount of decentering
of the second lens group G2. Although the trajectory for canceling
the tangent plane incidence height h can be theoretically
considered, the trajectory is not preferable because a
configuration of the mechanism for moving the second lens group G2
is difficult. As a result, the incident position of the principal
ray m to the tangent plane of the first lens group G1 in
association with the variable power approaches the aperture radius
of the first lens group G1 if the second derivative is positive.
Therefore, the amount of ambient light decreases.
[0147] If the second lens group G2 is moved along the trajectory
shown in FIG. 14, the principal ray incidence height h of the
principal ray m relative to the tangent plane of the first lens
group G1 is as shown in FIG. 15 relative to the amount of movement
in the optical axis direction of the second lens group G2. More
specifically, as a result of the adjustment of the trajectory
during the change in the magnification of the second lens group G2,
the principal ray incidence height h temporarily decreases
(principal ray incident position at the tangent plane approaches
the optical axis) during the movement from the low-power end state
(at the lowest power) to the high-power end side and increases up
to a predetermined amount of movement in the optical axis
direction. The principal ray incidence height h then decreases, and
the principal ray incidence height h can be configured not to be
higher than the height at the low-power end state (during the
lowest power) in the entire variable power range from the low-power
end state to the high-power end state. Therefore, designing the
aperture radius of the first lens group G1 to the size not reducing
the amount of ambient light in the low-power end state (at the
lowest power) allows a configuration for preventing the amount of
ambient light from being reduced during the change in the
magnification. FIG. 14 shows a case in which the second lens group
G2 moves to form a trajectory according to the function indicated
by the following expression (1). The first derivative is positive,
and the second derivative is negative.
Y=-2+X 0.1733 (1)
[0148] First Derivative 0.1733X -0.8267>0
[0149] Second Derivative -0.14326711X -1.8267<0
Movement of Diaphragm
[0150] In the microscope apparatus 100 according to the present
embodiment, the diaphragm S constituting the variable power optical
system 3 is arranged between the second lens group G2 (first
correction lens group CG1) and the third lens group G3 (second
correction lens group CG2) as described above. The entrance pupil
of the variable power optical system 3 is an image of the diaphragm
S created by the first lens group G1 and the second lens group G2
(first correction lens group CG1), and the exit pupil of the
variable power optical system 3 is an image of the diaphragm S
created by the third lens group G3 and the fourth lens group G4 (at
least one of the groups is the second correction lens group CG2).
Therefore, if the second lens group G2 (first correction lens group
CG1) and the third lens group G3 or the fourth lens group G4
(second correction lens group CG2) are decentered, the images of
the diaphragm S, or the entrance pupil and the exit pupil, are also
decentered. As described, the maximum diameter of the light passing
through the objective lens 1 is reduced by decentering the entrance
pupil, and there is an advantage that the diameter of the objective
lens 1 can be reduced and miniaturized. Meanwhile, although the
exit pupil is relayed by the imaging lens 4 and the eyepiece 6 to
form an eye point EP (location where the eye of the observer should
be placed) shown in FIG. 16, if the exit pupil is decentered, the
eye point EP positioned on the optical axis as shown in FIG. 16(a)
is decentered as in FIG. 16(b). As described, since the amount of
decentering of the lens group changes along with the change in the
magnification in the variable power optical system 3, the amount of
decentering of the eye point EP also changes along with the change
in the magnification, and the observation is obstructed. To prevent
this, the diaphragms S are decentered along with the change in the
magnification in the present embodiment. More specifically, the
diaphragms S are moved to reduce the distance between the centers
of the diaphragms S of the left and right variable power optical
systems 3 (bring close to the optical axis of the objective lens 1)
to cancel the decentering of the exit pupil caused by decentering
of the third lens group G3 or the fourth lens group G4 (second
correction lens group CG2). As a result, the decentering of the eye
point EP is corrected as shown in FIG. 16(c).
[0151] The luminous flux entering the variable power optical system
3 is the maximum during the highest power. Therefore, as described,
it is desirable that the optical axes of all lens groups and the
centers of the diaphragms S included in the variable power optical
system 3 substantially match (substantially coincide with the
reference optical axis A) to effectively use the entrance pupil of
the variable power optical system 3 during the highest power of the
variable power optical system 3.
[0152] Instead of decentering the diaphragms S along with the
decentering of the second correction lens group CG2, if a precise
circle including the entire area where an aperture section of the
diaphragm S is swept in the variable-power section is set as an
aperture section as shown in FIG. 17, in other words, if a
diaphragm S1 including an aperture section including the entire
area of the luminous flux moved by the change in the magnification
is arranged, or if the entire area where an aperture section of the
diaphragm S is swept in the variable-power section is set as an
aperture section as shown in FIG. 18, in other words, if a changed
diaphragm S2 including an aperture section including the entire
area of the luminous flux moved by the change in the magnification
is arranged, the eye point EP is not out of sight of the observer
even if the eye point EP shown in FIG. 16 is enlarged and
decentered. In FIGS. 17 and 18, the position in the low-power end
state of the diaphragm S decentered according to the change in the
magnification of the variable power optical system 3 (position in
the decentered state) is set as SL, and the position in the
high-power end state (position without decentering) is set as
SH.
Example
[0153] The following Table 7 shows amounts of decentering of the
lens groups G2 and G3 and an amount of decentering of the diaphragm
S when the second lens group G2 is set as the first correction lens
group CG1, and the third lens group G3 is set as the second
correction lens group CG2 in the variable power optical system 3
with a negative-positive-negative-positive 4-group configuration
shown in FIG. 4 in which the second lens group G2 and the third
lens group G3 move in opposite directions along the optical axis
during the change in the magnification. In Table 7, f1 denotes a
focal length of the first lens group G1, f2 denotes a focal length
of the second lens group G2, f3 denotes a focal length of the third
lens group G3, and f4 denotes a focal length of the fourth lens
group G4. Furthermore, D1 denotes a spacing between the first lens
group G1 and the second lens group G2 on the optical axis, D2
denotes a spacing between the second lens group G2 and the
diaphragm S on the optical axis, D3 denotes a spacing between the
diaphragm S and the third lens group G3 on the optical axis, and D4
denotes a spacing between the third lens group G3 and the fourth
lens group G4 on the optical axis. Although the lens actually has a
thickness, only the behavior of the ray entering the lens and the
ray ejected from the lens can be considered as an effect of the
lens, and a replacement to a thin lens with a thickness that can be
ignored is theoretically possible. Particularly, since the number
of lens groups is small in the variable power optical system,
approximation to the thin lens is easy. It is typical to replace
the lens groups by thin lenses to determine the optimal focal
length and the arrangement of the lens groups corresponding to the
specifications. In accordance with the example, each lens group is
replaced by a piece of thin lens in the following variable power
optical system 3.
TABLE-US-00007 TABLE 7 f1 = 88.42 f2 = -20.70 f3 = 51.71 f4 =
-55.14 Low-Power End High-Power End D1 4.08 58.69 D2 63.54 8.93 D3
68.26 4.93 D4 21.44 84.77 Amount of Decentering of Second -3.00
0.00 Lens Group Amount of Decentering of Third -1.29 0.00 Lens
Group Amount of Decentering of -1.70 0.00 Diaphragm
[0154] As shown in Table 7, if the second lens group G2, the third
lens group G3, and the diaphragm S are decentered, miniaturization
of the objective lens 1 can be realized based on the second lens
group G2 decentered in accordance with the power changing operation
of the variable power optical system 3. A substantially parallel
luminous flux entered in the variable power optical system 3 can be
ejected as a substantially parallel luminous flux as a result of
the decentering of the third lens group G3, and decentering of the
eye point can be prevented even if the third lens group G3 is
decentered as a result of the decentering of the diaphragm S.
Configuration of Illumination Optical System
[0155] The entrance pupil of the imaging optical system 5 needs to
be filled by the illumination light to perform an appropriate
transmitted illumination observation in the microscope apparatus.
This also requires filling the entrance pupil conjugate image of
the imaging optical system 5 in the opposite direction of the
objective lens 1 as seen from the surface of the object (called
"illumination optical system side" in the following description)
with the illumination light. However, as shown in FIG. 19(a), the
entrance pupil of a stereoscopic microscope apparatus 100' is
decentered relative to the optical axis of an objective lens 1'
because a variable power optical system 3' is divided into two
optical paths. Accordingly, an entrance pupil conjugate image PI'
on the side of a transmissive illumination optical system 20' is
also decentered relative to the optical axis of the objective lens
1'. Therefore, the transmissive illumination optical system 20'
needs to supply the illumination light to a location away from the
optical axis of the objective lens 1', and there is an enlargement
in the vertical plane relative to the optical axis of the objective
lens 1' (diameter d1 in FIG. 19(a)). In general, the position of
the entrance pupil conjugate image PI' is farther (away from the
optical axis in a direction perpendicular to the optical axis of
the objective lens 1') in a low-power end state shown in FIG. 19(a)
than in a high-power end state shown in FIG. 19(b). Therefore, the
enlargement of the required transmissive illumination optical
system 20' is more noticeable than in the high-power end state.
[0156] However, as described, the entrance pupil of the imaging
optical system (variable power optical system 3) decenters in a
direction in which the distance between optical axes of the left
and right optical paths is reduced during low-power in the
microscope apparatus 100 according to the present embodiment. More
specifically, as shown in FIG. 19(c), the entrance pupil of the
imaging optical system 5 decenters in the direction in which the
distance between the optical axes of the left and right optical
paths is reduced. Therefore, an entrance pupil conjugate image PI
on the side of a transmissive illumination optical system 20 also
approaches the optical axis of the objective lens 1. As a result, a
diameter d2 of the transmissive illumination optical system 20 that
supplies illumination light to the microscope apparatus 100
according to the present embodiment has a relationship of d1>d2
in relation to a diameter d1 of the transmissive illumination
optical system 20' of the conventional microscope apparatus 100',
and the required transmissive illumination optical system 20 can be
reduced.
[0157] As for the angles of the illumination light directing the
samples (surfaces of the objects O and O'), .theta.2 of FIG. 19(c)
is smaller than .theta.1 of FIG. 19(a). In general, the luminance
is higher near the optical axis direction in the illumination
optical system. Therefore, a bright illumination optical system can
be more easily constructed in the present embodiment. Specific
examples of configuration of the illumination optical system
include arranging a surface light source near the entrance pupil
conjugate image PI and forming a light source image near the
entrance pupil conjugate image PI. Particularly, the size of the
surface light source directly affects the cost when the surface
light source is arranged. Therefore, a large advantage can be
obtained by the present embodiment that can reduce the size of the
illumination optical system.
[0158] Like the transmitted illumination observation, a coaxial
epi-illumination observation is also possible in the microscope
apparatus according to the present embodiment. The coaxial
epi-illumination is an illumination method of matching the optical
axis of the observation optical system and the optical axis of the
epi-illumination optical system. FIG. 20 shows a case of arranging
a coaxial epi-illumination apparatus 109 in which deflection
elements 7 (for example, half mirrors) are inserted between the
objective lens 1 and the observation optical systems 2 (variable
power optical systems 3) to insert the illumination light from the
light source 110 through an epi-illumination optical system 8 from
the side. According to the configuration shown in FIG. 20, the
illumination light exited from the light source 109 passes through
the epi-illumination optical system 8, is reflected by the
defection element 7, enters the objective lens 1, is collected by
the objective lens 1, and is directed to the sample (object) on the
sample platform 102. The coaxial epi-illumination observation is
possible in the entire variable power range of the variable power
optical system 3 by including the variable power optical system for
illumination light with the same variable power range as the
variable power optical system 3 in the epi-illumination optical
system 8. Alternatively, the coaxial epi-illumination apparatus 109
with a compact configuration can be formed by forming the
epi-illumination optical system 8 not for the entire variable power
range, but for part of the variable power range, or the
epi-illumination optical system 8 with a fixed magnification. The
coaxial epifluorescent observation is also possible by arranging in
the epi-illumination optical system 8 a filter that selectively
transmits an excitation wavelength and arranging dichroic mirrors
as the deflection elements 7 that selectively reflect the
excitation wavelength and that selectively transmit a fluorescence
wavelength generated by the sample (object).
[0159] FIG. 21 shows a case in which a coaxial epi-illumination
apparatus 111 is inserted between the variable power optical
systems 3 and the imaging lenses 4 inside the observation optical
systems 2. According to the configuration shown in FIG. 21, the
illumination light ejected from light sources 112 passes through
epi-illumination optical systems 10, is reflected by defection
elements 9 (for example, beam splitter prisms), and enters the
variable power optical systems 3. The illumination light is guided
to the objective lens 1 by the variable power optical systems 3 and
directed to the sample (surface of the object O). In this case,
since the variable power optical system 3 is shared by the
observation optical systems 2 and the epi-illumination optical
systems 10, the coaxial epi-illumination observation is possible
across the entire variable power range without including
independent variable power optical systems for illumination light
in the epi-illumination optical systems 10. As in the case of FIG.
20, simultaneous epifluorescent observation is possible by
arranging in the epi-illumination optical system 10 a filter that
selectively transmits an excitation wavelength and arranging
dichroic mirrors as the deflection elements 9 that selectively
reflect the excitation wavelength and that selectively transmit a
fluorescence wavelength generated by the sample (object).
[0160] However, when the coaxial epi-illumination apparatus 111 is
inserted at the position indicated in FIG. 21, the first correction
lens group CG1 (second lens group G2) and the second correction
lens group CG2 (third lens group G3) in the variable power optical
systems 3 move in the direction including the component
perpendicular to the reference optical axis A during the change in
the magnification. Therefore, as described, the exit pupils also
move in the direction including the component perpendicular to the
reference optical axis A. Thus, a decentering mechanism that
decenters the illumination lenses of the epi-illumination optical
systems 10 in accordance with the decentering of the exit pupils of
the imaging optical systems 5 (variable power optical systems 3) to
move the light source images can be arranged to cause the light
source images to overlap the exit pupils. This can realize
efficient illumination. An example of configuration of the coaxial
epi-illumination apparatus 111 will be described below.
First Example
[0161] As shown in FIG. 22, the variable power optical systems 3
are arranged on the image side of the objective lens 1 in the
microscope apparatus 100 according to a first embodiment, and the
coaxial epi-illumination apparatus 111 is mounted further close to
the image. Although the epi-illumination optical systems 10
constituting the coaxial epi-illumination apparatus 111 are
actually folded and arranged at the back of FIG. 22, the
epi-illumination optical systems 10 are illustrated in the same
plane for convenience of description. The light sources 112 shown
in FIG. 21 are guided through fibers from a light source apparatus
not shown, and end faces of the fibers serve as the light sources
112 in the description here.
[0162] The illumination lenses 11 collect the illumination light
ejected from the light sources (fiber end faces) 112. The
deflection elements (divided composite prisms) 9 reflect the
illumination light, and the illumination light enters the same
optical path as the imaging optical system 5. In the coaxial
epi-illumination apparatus 111, an afocal optical system including
positive lens groups 13 and negative lens groups 16 is arranged at
the front and back of the deflection elements 9. The afocal optical
system has a function of restoring the exit pupils of the first
image IM formed by the imaging lenses 6 arranged on the image side
to their original positions when the exit pupils get far away from
their positions in the first image IM before the insertion of the
coaxial epi-illumination apparatus 111 due to the thickness of the
coaxial epi-illumination apparatus 111 being inserted into the
optical paths of the imaging optical system 5. Such a Galileo-type
afocal optical system usually shifts the imaging magnification to
the high-power side by about 1.2 to 1.5 times. The illumination
light is reflected by the deflection elements 9 and enters the
variable power optical system 3 through the positive lens groups 13
of the afocal optical system.
[0163] As shown in FIG. 22, polarizers 12 and analyzers 15 are
arranged on the side of the light sources 112 and on the side of
the imaging lenses 6 of the deflection elements 9, and a
quarter-wave plate 14 is arranged on the object O side of the
objective lens 1. The polarizers 12 and the analyzers 15 are in a
crossed Nicols arrangement, and the quarter-wave plate 14 is
rotatable so that the fast axis stops at positions forming 45
degrees to the axes of the polarizers 12 and the analyzers 15.
These components function as a optical isolator. Although the
illumination light subjected to linear polarization by the
polarizers 12 becomes noise light when the illumination light is
reflected by lens surfaces in the variable power optical systems 3,
the analyzers 15 block the noise light. Meanwhile, when the
illumination light passes through the variable power optical
systems 3 and the objective lens 1 and enters the quarter-wave
plate 14, the polarization state becomes circular polarization.
Therefore, even if the reflectivity of the object O is dependent on
the polarization, the dependency does not affect the observed
image, and the light can be observed as bright-field illumination.
The circular polarization reflected by the object O becomes linear
polarization (therefore, the same polarization direction as the
analyzers 15) perpendicular to the entered linear polarization
(polarization direction of the polarizers 12) when the light passes
through the quarter-wave plate 14 again. After subjected to an
enlargement action by the objective lens 1 and the variable power
optical systems 3, the signal light transmits the deflection
elements 9 and transmits the analyzers 15. In this way, the
microscope apparatus 100 includes a mechanism for improving S/N of
the observed image.
[0164] Configurations of the lenses that guide the illumination
light ejected from the light sources 112 to the variable power
optical systems 3 among the lenses constituting the coaxial
epi-illumination apparatus 111 will be described using data. Here,
the ray will be followed in order of the object O, the objective
lens 1, the variable power optical systems 3, and the coaxial
epi-illumination apparatus 111. The data of the objective lens 1 is
illustrated in Table 1, and the data of the variable power optical
systems 3 is illustrated in Table 2 (the third lens group G3 serves
as the second correction lens group CG2). Therefore, the coaxial
epi-illumination apparatus 111 is inserted after a 13th plane of
Table 1 through the variable power optical systems 3 of Table
2.
[0165] The following Table 8 shows data of the optical system
constituting the coaxial epi-illumination apparatus 111. Plane
numbers in Table 8 are as shown in FIG. 23. A 17th plane and an
18th plane indicate optical planes of the deflection element 9, and
a 21st plane denotes the light source 112 (fiber end). In a radius
of curvature r of Table 8, .infin. denotes a plane (the same
applies to the following description).
TABLE-US-00008 TABLE 8 m r d nd vd 14 54.472 1.6 1.671629 38.798 15
22.0875 2.7 1.60411 60.645 16 -177.143 6.2 17 .infin. 16 1.568829
56.048 18 .infin. 66 19 20.122 3 1.516800 64.103 20 -20.122 21 21
.infin.
[0166] In FIG. 23, X denotes how the ray passing through the center
of the diaphragm S passes through the optical system of the coaxial
epi-illumination apparatus 111 in the variable power optical system
3 in the optical path on the right side. In the microscope
apparatus 100 according to the present embodiment, the ray X
passing through the center of the diaphragm S of the variable power
optical system 3 is decentered by -0.58 mm in the low-power end
state of the variable power optical system 3 when the ray X reaches
the 21st plane (fiber end) of the epi-illumination apparatus 111.
(The decentering direction shown in FIG. 23 that is .delta. shown
in FIG. 23 is illustrated as negative.) This is the amount of
decentering of the exit pupil generated in association with the
decentering of the second correction lens group CG2 (third lens
group G3) of the variable power optical system 3. If the
illumination lens 11 is decentered to make a correction so that the
ray X reaches the center of the 21st plane, the exit pupil and the
light source image can be placed on top of each other. As for the
amount of correction, the illumination lens 11 can be decentered by
+0.51 mm relative to the amount of decentering -1.2934 mm of the
third lens group G3. In another example, instead of decentering the
illumination lens 11, the end face may be decentered by +0.58 mm if
a light source such as an optical fiber is used. In the
configuration shown in FIGS. 22 and 23, a two-branch fiber with a
.phi.4 mm ejection end face is used to deliver the light from the
light source apparatus for fiber to the illumination systems of two
systems (left and right optical paths). If the decentering of the
illumination lens 11 (or fiber end) is steplessly and continuously
driven in association with the decentered trajectory of the second
correction lens group CG2 of the variable power optical system 3,
the observer can perform observation without stress.
[0167] If at least two positions (for example, two positions on the
low-power side and the high-power side) can be switched in the
decentering mechanism of the illumination lens 11 (or fiber end)
instead of steplessly driving the decentering mechanism, the
configuration of the decentering mechanism of the epi-illumination
apparatus 111 is simplified, and the cost is reduced.
Second Embodiment
[0168] Although a case in which the illumination lens 11 (or fiber
end) is decentered in accordance with the exit pupil decentered by
the movement of the second correction lens group CG2 has been
described in the first embodiment, the light source image formed by
the illumination lens 11 can be enlarged so that the exit pupil
does not extend beyond the light source image even if the exit
pupil is moved (form a light source image in a size including the
trajectory of the exit pupil moved during the change in the
magnification of the variable power optical system 3). As a result
of enlarging the light source image, the decentering mechanism for
the illumination optical system 10 of the coaxial epi-illumination
apparatus 111 is not necessary, and the configuration can be
simplified. The enlargement of the light source image can be
realized by enlarging the used light source (enlarge the fiber
ejection end face) or enlarging the light source magnification of
the illumination optical system 10. The focal length of the
illumination lens 11 can be reduced to enlarge the light source
magnification. For example, the enlargement can be realized by
setting the optical system as shown in the following Table 9. The
configuration of the coaxial epi-illumination apparatus 111 is the
same as in the first example.
TABLE-US-00009 TABLE 9 m r d nd vd 14 54.472 1.6 1.671629 38.798 15
22.0875 2.7 1.60411 60.645 16 -177.143 6.2 17 .infin. 16 1.568829
56.048 18 .infin. 66 19 10.0 3 1.516800 64.103 20 -10.0 10 21
.infin.
[0169] As a result of using the optical system with the data shown
in Table 9, the amount of decentering of the illumination lens 11
can be reduced to -0.28 mm relative to the amount of decentering
-1.2934 mm of the third lens group G3. Therefore, the amount of
decentering relative to the size of the light source can be
ignored, and the illumination range is not deviated by the
decentering.
Light Shielding Method in Imaging Optical System
[0170] As described, in the variable power optical system 3 of the
microscope apparatus 100 according to the present embodiment, left
and right lens groups constituting the second lens group G2 and the
third lens group G3 as movable groups move over the reference
optical axis A in accordance with the magnification and move in the
direction perpendicular to the reference optical axis A. Therefore,
as the left and right second lens group G2 and third lens group G3
move in the direction perpendicular to the optical axis, the space
changes (for example, the size of the space (gap) generated between
the left and right lens groups changes). Therefore, the light
outside the field of view may not enter the second lens group G2
and the third lens group G3, but may pass through the space to
enter the following lens groups or optical systems to cause flare
or ghost. Thus, the microscope apparatus 100 according to the
present embodiment includes light shielding units that block at
least the light passing through the optical axis side of the
objective lens 1 among the light passing through the space around
the lens groups G2 and G3 without entering the second lens group G2
and the third lens group G3 as movable groups to prevent the
generation of flare or ghost.
[0171] Hereinafter, a specific configuration of the light shielding
units arranged on the second lens group G2 and the third lens
groups G3 as movable groups of the variable power optical system 3
according to the present embodiment will be described. The same
constituent members as described above are designated with the same
reference numerals, and the detailed description will not be
repeated. In the following description, L is added to reference
numerals of the members arranged in the optical path on the left
side, and R is added to reference numerals of the members arranged
in the optical path on the right side. In the drawings, M denotes
eyes of the observer.
First Example
[0172] A configuration of the variable power optical system 3 of
the microscope apparatus 100 according to a first example will be
described using FIGS. 24 and 25. As shown in FIG. 24, light
shielding units H2 and H3 are arranged between the left and right
lens groups (G2L, G2R; G3L, G3R) of the second lens group G2 and
the third lens group G3 in the variable power optical system 3, the
light shielding units H2 and H3 connecting the lens groups (G2L,
G2R; G3L, G3R). The light shielding units H2 and H3 are arranged to
have structures in which the sizes (lengths in the direction
perpendicular to the optical axis of the objective lens 1 (or
lengths in the direction perpendicular to the reference optical
axis A, the same applies hereinafter)) of the light shielding units
H2 and H3 change along with the movement of the left and right lens
groups (G2L, G2R; G3L, G3R), and the light passing through the
space generated between the lens groups (G2L, G2R; G3L, G3R) is
blocked. More specifically, although the shapes of the light
shielding units H2 and H3 can be any shapes as long as the light
shielding units H2 and H3 can freely expand and contract along with
the movement of the left and right lens groups (G2L, G2R; G3L,
G3R), it is preferable that the light shielding units H2 and H3
have structures bendable in expansion/contraction directions, such
as a bellows structure and a folding-screen structure. The
expansion/contraction directions are directions perpendicular to
the optical axis of the objective lens 1 between the left and right
lens groups (G2L, G2R; G3L, G3R) and are left and right directions
in the drawings.
[0173] More specifically, as shown in FIG. 25(a), the left and
right lens groups (G2L, G2R; G3L, G3R) of the second lens group G2
and the third lens group G3 move away from each other in directions
perpendicular to reference optical axes AL and AR when the
magnification is changed to the high-power end side. In this case,
the light shielding units H2 and H3 arranged between the left and
right lens groups (G2L, G2R; G3L, G3R) extend in directions of the
movement of the left and right lens groups (G2L, G2R; G3L, G3R). On
the other hand, as shown in FIG. 25(b), the left and right lens
groups (G2L, G2R; G3L, G3R) of the second lens group G2 and the
third lens group G3 move to approach each other in directions
perpendicular to the reference optical axes when the magnification
is changed to the low-power end side. In this case, the light
shielding units H2 and H3 arranged between the left and right lens
groups (G2L, G2R; G3L, G3R) contract in the moving directions of
the left and right lens groups. This can block the light passing
through the space formed between the left and right lens groups
(G2L, G2R; G3L, G3R) of the second lens group G2 and the third lens
group G3 as movable groups to prevent the light from entering the
following lens groups or optical systems, and the generation of
flare or ghost can be prevented.
Second Example
[0174] A configuration of the variable power optical system 3 of
the microscope apparatus 100 according to a second example will be
described using FIGS. 26 to 28. As shown in FIG. 26, different
points from the first example in the microscope apparatus 100
according to the second example are configurations of the second
lens group G2 and the third lens group G3 of the variable power
optical system 3. Like the second lens group G2 and the third lens
group G3 according to the second embodiment, the second lens group
G2 and the third lens group G3 of the variable power optical system
3 of the microscope apparatus 100 according to the present example
are movable groups, and the groups can move in directions of the
reference optical axes AL and AR and in directions perpendicular to
the optical axes. The moving directions of the second and third
lens groups G2 and G3 when the magnification is changed from the
low-power end state to the high-power end state are the same as in
the first example.
[0175] As shown in FIG. 27, the second lens group G2 of the
variable power optical system 3 includes first members 21 that hold
the left and right lens groups G2L and G2R and a second member 22
that moves the entire second lens group G2 in the optical axis
direction and that holds the left and right lens groups G2L and G2R
held by the first members 21 so that the left and right lens groups
G2L and G2R can be moved in directions perpendicular to the optical
axis. Similarly, the third lens group G3 includes first members 31
that hold the left and right lens groups G3L and G3R and a second
member 32 that moves the entire third lens group G3 in the optical
axis direction and that holds the left and right lens groups G3L
and G3R held by the first members 31 so that the left and right
lens groups G3L and G3R can move in directions perpendicular to the
optical axis.
[0176] As shown in FIG. 28, the second members 22 and 32 of the
second lens group G2 and the third lens group G3 are formed by a
material that blocks the light, and a pair of left and right
aperture sections 25 and 35 that penetrate through the optical axis
direction of the first lens group G1 are arranged. In the aperture
sections 25 and 35, the left and right lens groups (G2L, G2R; G3L,
G3R) of the second and third lens groups G2 and G3 are always
positioned within the aperture sections 25 and 35 as seen from the
optical axis direction, regardless of the movement of the left and
right first members 21 and 31 in the directions perpendicular to
the optical axis of the first lens group G1 relative to the second
members 22 and 32. Therefore, the aperture sections 25 and 35 have
shapes formed by cutting out, in semicircular shapes, left and
right end portions (end portions in the moving directions of the
lens groups) of the rectangular-shaped apertures extending in the
directions perpendicular to the optical axis of the objective lens
1. In the first members 21 and 31, apertures in substantially the
same size as the left and right lens groups (G2L, G2R; G3L, G3R)
are formed on plate-shaped members that block light, and the left
and right lens groups (G2L, G2R; G3L, G3R) are held by being set in
the apertures. The first members 21 and 31 have a size (for
example, a rectangular shape larger than the aperture sections 25
and 35 as seen from the optical axis direction) that always covers
portion other than the lens groups (G2L, G2R; G3L, G3R) in the
aperture sections 25 and 35 even if the left and right lens groups
(G2L, G2R; G3L, G3R) move in directions perpendicular to the
optical axis of the objective lens 1. Therefore, even if the left
and right lens groups (G2L, G2R; G3L, G3R) move in directions
perpendicular to the optical axis of the objective lens 1 during
the change in the magnification, the light does not enter the lens
groups (G2L, G2R; G3L, G3R) constituting the second and third lens
groups G2 and G3, and the light about to pass through the
peripheral section can be blocked. As a result, the light does not
enter the following lens groups or optical systems, and the
generation of flare or ghost can be prevented.
Modified Example of Second Example
[0177] If the first members 21 and 31 are formed in rectangular
shapes as shown in FIG. 28, the size of the first members 21 and 31
is a predetermined length in a direction perpendicular to the
optical axis to cover the portion other than the lens groups in the
aperture sections 25 and 35 even if the left and right lens groups
(G2L, G2R; G3L, G3R) move. Therefore, the size of the second
members 22 and 32 in the horizontal directions is large at
high-power as shown in FIG. 28(a), and the lens groups (G2L, G2R;
G3L, G3R) cannot be brought closer to the optical axis of the
objective lens 1 than the length in the optical axis direction of
the first members 21 and 31 at low-power as shown in FIG. 28(b). As
a result, the entire variable power optical system 3 is
enlarged.
[0178] Therefore, as shown in FIG. 29, the length of the first
members 21 and 31 in the direction perpendicular to the optical
axis is set to about the size that allows holding the left and
right lens groups (G2L, G2R; G3L, G3R, the size just slightly
greater than the diameters of the lens groups), and elastic members
26 and 36 that can expand and contract in the direction
perpendicular to the optical axis of the objective lens 1 are
attached to both end portions of the first members 21 and 31
(shapes for expansion and contraction are the same as in the first
example). The elastic members 26 and 36 include inner elastic
members 26a and 36a, in which ends on one side are attached to the
optical axis side of the first members 21 and 31, and outer elastic
members 26b and 36b attached to the other side of the optical axes.
The other ends of the inner elastic members 26a and 36a are
attached to substantially center sections of the second members 22
and 32 in the direction perpendicular to the optical axis of the
objective lens 1 (closer to optical axis than the aperture sections
25 and 35), and the other ends of the outer elastic members 26b and
36b are attached to both end portions of the second members 22 and
32 in the direction perpendicular to the optical axis of the
objective lens 1 (more outside than the aperture section 25). The
sizes of the inner elastic members 26a and 36a and the outer
elastic members 26b and 36b in the width direction (sizes in the
vertical direction of FIG. 29) are substantially the same as the
sizes of the first members 21 and 31 in the width direction.
[0179] According to the configuration of the second lens group G2
and the third lens group G3, if the first members 21 and 31 are
moved to move the left and right lens groups (G2L, G2R; G3L, G3R)
in the direction perpendicular to the optical axis of the objective
lens 1 during the change in the magnification, the elastic members
26 and 36 expand and contract in accordance with the movement of
the first members 21 and 31. Therefore, the first members 21 and 31
and the elastic members 26 and 36 can always cover the portion
other than the lens groups (G2L, G2R; G3L, G3R) at the aperture
sections 25 and 35. Thus, the light does not enter the lens groups
(G2L, G2R; G3L, G3R), and the light about to pass through the
peripheral section can be blocked. Therefore, the light does not
enter the following lens groups or optical systems, and the
generation of flare or ghost can be prevented. The elastic members
26 and 36 that expand and contract along with the movement of the
first members 21 and 31 are attached to the both end portions of
the first members 21 and 31 in the direction perpendicular to the
optical axis of the objective lens 1. Therefore, the size of the
second members 22 and 32 in the direction perpendicular to the
optical axis of the objective lens 1 can be just slightly greater
than the periphery of the aperture sections 25 and 35, and the left
and right lens groups (G2L, G2R; G3L, G3R) can be brought close to
the optical axis of the objective lens 1 to reduce the variable
power optical system 3 as a whole.
[0180] In this way, as shown in the first and second examples of
the microscope apparatus 100, the arrangement of the light
shielding units to the lens groups included in the variable power
optical system 3 that move in the direction perpendicular to the
reference optical axes AL and AR during the change in the
magnification can avoid the enlargement of the objective lens in
the microscope apparatus including the objective lens and the
observation optical system (coupled optical system as a whole), and
the imaging optical system can be enlarged to the low-power range
while reducing the generation of flare or ghost.
Other Modified Examples
[0181] Although the configurations in which the first correction
lens group CG1 and the second correction lens group CG2 serving as
the variable power optical systems 3 perform decentering operations
throughout the entire variable power range have been described, the
arrangement is not limited to this. A configuration in which the
decentering operations are performed only at sections close to the
low-power end where the maximum diameter of the light passing
through the objective lens 1 is wide is also possible. Both the
variable power optical systems 3 for left and right eyes may
perform the decentering operations, or only one of the variable
power optical systems 3 may perform the decentering operations.
Although the case in which two optical paths (observation optical
systems 2) are arranged for the objective lens 1 has been
described, the same applies to an arrangement of three or more
optical paths (for example, configuration of two observation
optical systems and one illumination optical system).
[0182] Although the imaging optical system is divided into three
optical systems, the objective lens, the afocal variable power
optical system, and the imaging lens, in the description, the lens
group closest to the image in the afocal variable power optical
system and the imaging lens may be designed as one lens group. Even
if the light ejected from the objective lens is a convergent or
divergent luminous flux in some degree instead of the parallel
luminous flux, an imaging optical system similar to the objective
lens that ejects the parallel luminous flux can be formed if the
following optical systems correct the light. Therefore, the
variable power optical system does not have to be an afocal system
in the present invention.
REFERENCE SIGNS LIST
[0183] 1 objective lens [0184] 2 observation optical system [0185]
3 variable power optical system [0186] G1 first lens group [0187]
G2 (CG1) second lens group (first correction lens group) [0188] G3
(CG2) third lens group (second correction lens group) [0189] 4
imaging lens [0190] 5 imaging optical system [0191] 8, 10
illumination optical systems [0192] 20, 110, 112 light sources
[0193] 21, 31 first members [0194] 22, 32 second members [0195] 25,
35 aperture sections [0196] 26, 36 elastic members [0197] S, S1, S2
diaphragms [0198] H2, H3 light shielding units [0199] IM first
image A reference optical axis [0200] 100 parallel stereoscopic
microscope apparatus (microscope apparatus)
* * * * *