U.S. patent application number 09/803942 was filed with the patent office on 2001-10-18 for lens barrel with variable eyepoint position and microscope using the same lens barrel.
Invention is credited to Kawasaki, Kenji.
Application Number | 20010030801 09/803942 |
Document ID | / |
Family ID | 18594110 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030801 |
Kind Code |
A1 |
Kawasaki, Kenji |
October 18, 2001 |
Lens barrel with variable eyepoint position and microscope using
the same lens barrel
Abstract
A lens barrel for microscope comprises a first optical system
(G1), a second optical system (G2), and a third optical system (G3)
. The first optical system (G1) comprises a lens unit (G1L) which
forms an intermediate image, a prism (P1), and deflecting mirrors
(M1, M2). The second optical system (G2) comprises a deflecting
mirror (M3) and a lens unit and converts an intermediate image by
the lens unit (G1L) into a beam of parallel rays. The third optical
system (G3) introduces the beam of parallel rays from the second
optical system (G2) into an ocular. The deflecting mirror (M3) is
configured to be turned around an axis normal to a center axis of
the beam of rays from the first optical system (G1) and to a center
axis of the beam of rays from the second optical system (G2) at the
point P of intersection of these center axes. The horizontal
distance from the optical axis of the objective to the eyepoint
position, the eyepoint height, and the depression angle for
observation are made variable by the lens barrel, so that a person
of whatever build is allowed to perform observation with little
fatigue in a natural posture.
Inventors: |
Kawasaki, Kenji; (Tokyo,
JP) |
Correspondence
Address: |
PILLSBURY WINTHROP LLP
1600 TYSONS BOULEVARD
MCLEAN
VA
22102
US
|
Family ID: |
18594110 |
Appl. No.: |
09/803942 |
Filed: |
March 13, 2001 |
Current U.S.
Class: |
359/384 ;
359/368; 359/382; 359/431 |
Current CPC
Class: |
G02B 21/24 20130101;
G02B 7/24 20130101 |
Class at
Publication: |
359/384 ;
359/368; 359/382; 359/431 |
International
Class: |
G02B 021/00; G02B
023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2000 |
JP |
2000-076351 |
Claims
What is claimed is:
1. A lens barrel comprising, in order from a light incident side: a
first optical system; a second optical system which converts a beam
of rays emergent from said first optical system into a beam of
parallel rays; a third optical system which introduces the beam of
parallel rays emergent from said second optical system into an
ocular; wherein said first optical system comprises a lens unit
which forms an intermediate image and at least three light
deflecting members which deflect the beam of rays, wherein said
second optical system comprises a lens unit and a light deflecting
member, and wherein said light deflecting member of said second
optical system is constructed an arranged to turn around an axis
that is perpendicular to a first optical axis and to a second
optical axis, where a center axis of the beam of rays emergent from
a most second optical system-side one of said light deflecting
members of said first optical system in optical arrangement is
defined as the first optical axis, and a center axis of the beam of
parallel rays emergent from said second optical system is defined
as the second optical axis.
2. A lens barrel comprising, in order from a light incident side: a
first optical system; a second optical system which converts a beam
of rays emergent from said first optical system into a beam of
parallel rays; and a third optical system which introduces the beam
of parallel rays emergent from said second optical system into an
ocular, wherein said first optical system comprises a lens unit
which forms an intermediate image and at least four light
deflecting members which deflect the beam of rays, and wherein a
separation between said second optical system and said third
optical system is variable in a direction along a center axis of
the beam of rays emergent from said second optical system.
3. A lens barrel according to claim 1, wherein said lens barrel is
constructed and arranged so that, when said light deflecting member
of said second optical system is turned by an angle of .alpha., a
rear section of said second optical system disposed behind said
light deflecting member of said second optical system, said third
optical system and the ocular are integrally revolved by an angle
of 2.alpha..
4. A lens barrel according to claim 3, wherein said lens barrel is
constructed and arranged so that a separation between said second
optical system and said third optical system is variable in a
direction along the second optical axis.
5. A lens barrel according to claim 2 or 4, wherein said third
optical system comprises, in order from a side of said second
optical system, a lens unit (L31) having a positive refracting
power, a lens unit (L32) having a negative refracting power, and a
lens unit (L33) having a positive refracting power.
6. A lens barrel according to claim 5, wherein said lens unit (L31)
comprises at least one positive meniscus lens which directs a
concave surface thereof toward said lens unit (L32), and said lens
unit (L33) comprises at least one positive meniscus lens which
directs a concave surface thereof toward said lens unit (L32).
7. A lens barrel according to claim 2 or 4, wherein the following
condition is satisfied:0.7.ltoreq.F1/F.ltoreq.1.4 where F1 is a
focal length of said first optical system and F is a focal length
of an entire system including said first optical system through
said third optical system.
8. A lens barrel according to claim 7, wherein the following
condition is further satisfied:0.5.ltoreq.F3/F.ltoreq.1 where F3 is
a focal length of said third optical system.
9. A microscope provided with a lens barrel, said lens barrel
comprising, in order from a light incident side: a first optical
system; a second optical system which converts a beam of rays
emergent from said first optical system into a beam of parallel
rays; and a third optical system which introduces the beam of
parallel rays emergent from said second optical system into an
ocular; wherein said first optical system comprises a lens unit
which forms an intermediate image and at least three light
deflecting members which deflect the beam of rays, wherein said
second optical system comprises a lens unit and a light deflecting
member, and wherein said light deflecting member of said second
optical system is constructed an arranged to turn around an axis
that is perpendicular to a first optical axis and to a second
optical axis, where a center axis of the beam of rays emergent from
a most second optical system-side one of said light deflecting
members of said first optical system in optical arrangement is
defined as the first optical axis, and a center axis of the beam of
parallel rays emergent from said second optical system is defined
as the second optical axis.
10. A microscope provided with a lens barrel, said lens barrel
comprising, in order from a light incident side: a first optical
system; a second optical system which converts a beam of rays
emergent from said first optical system into a beam of parallel
rays; and a third optical system which introduces the beam of
parallel rays emergent from said second optical system into an
ocular, wherein said first optical system comprises a lens unit
which forms an intermediate image and at least four light
deflecting members which deflect the beam of rays, and wherein a
separation between said second optical system and said third
optical system is variable in a direction along a center axis of
the beam of rays emergent from said second optical system.
11. A microscope according to claim 9, wherein said lens barrel is
constructed and arranged so that, when said light deflecting member
of said second optical system is turned by an angle of .alpha., a
rear section of said second optical system disposed behind said
light deflecting member of said second optical system, said third
optical system and the ocular are integrally revolved by an angle
of 2.alpha..
12. A microscope according to claim 11, wherein said lens barrel is
constructed and arranged so that a separation between said second
optical system and said third optical system is variable in a
direction along the second optical axis.
13. A microscope according to claim 10 or 12, wherein said third
optical system comprises, in order from a side of said second
optical system, a lens unit (L31) having a positive refracting
power, a lens unit (L32) having a negative refracting power, and a
lens unit (L33) having a positive refracting power.
14. A microscope according to claim 13, wherein said lens unit
(L31) comprises at least one positive meniscus lens which directs a
concave surface thereof toward said lens unit (L32), and said lens
unit (L33) comprises at least one positive meniscus lens which
directs a concave surface thereof toward said lens unit (L32).
15. A microscope according to claim 10 or 12, wherein the following
condition is satisfied:0.7.ltoreq.F1/F.ltoreq.1.4where F1 is a
focal length of said first optical system and F is a focal length
of an entire system including said first optical system through
said third optical system.
16. A microscope according to claim 15, wherein the following
condition is further satisfied:0.5.ltoreq.F3/F.ltoreq.1 where F3 is
a focal length of said third optical system.
Description
BACKGROUND OF THE INVENTION
[0001] 1) Field of the Invention
[0002] The present invention relates to a lens barrel with variable
eyepoint position and a microscope using the same lens barrel.
Hereafter, this type of lens barrel will be simply referred to as
"variable lens barrel".
[0003] 2) Description of Related Art
[0004] Various proposals have been made for a lens barrel used in
microscopy regarding adjustment of the position at which the ocular
is looked into (i. e. eyepoint) so as to allow an observer to
easily perform observation in relaxed posture.
[0005] For example, Japanese Patent Application Preliminary
Publication (KOKAI) No. Hei 4-166907 proposes a tilting lens barrel
which is provided with a mechanism for adjusting the depression
angle, or the angle in which an observer looks into the ocular of
the binocular section. This configuration is intended to adjust the
height and position of the eyepoint by changing the depression
angle.
[0006] Also, Japanese Patent Application Preliminary Publication
(KOKAI) No. Hei 8-278448 proposes to lower the eyepoint position by
deflecting a beam of rays emergent from the objective using a
deflecting member. The object of this proposal is to allow an
observer to perform observation in relaxed posture by preliminarily
lowering the eyepoint position.
[0007] Also, Japanese Patent Application Preliminary Publication
(KOKAI) No. Hei 10-142473 proposes a lens barrel that is provided
with a tilting mechanism for changing the depression angle and a
mechanism for moving it along the observation optical axis. The
object of this proposal is to change each of the height of the
eyepoint position and the horizontal distance from the optical axis
of the objective to the position of the eye of an observer.
[0008] Also, Japanese Patent Application Preliminary Publication
(KOKAI) No. Hei 9-73031 discloses a microscope comprising an
optical system that is made afocal between an objective and an
imaging lens, which is housed in a movable lens barrel. The afocal
beam between the objective and the imaging lens is deflected in the
horizontal direction by a first deflecting member and is further
deflected by 90.degree. by a second reflecting member, to enter the
imaging lens. A guide is provided between the first deflecting
member and the second reflecting member so that the second
deflecting member and the movable lens barrel are integrally moved
for changing the eyepoint position.
[0009] In microscopy, especially in the case where inspection of a
large number of specimens or samples takes a long time, it is very
important, for preventing fatigue of an observer/inspector and
inaccurate inspection result caused by carelessness, to allow the
observer to work in a relaxed posture. FIG. 22 shows the outer
dimensions of an ordinary microscope. In order to relieve fatigue
of each observer in the case where tall and large-built individuals
and short and small-built individuals have to use a common
microscope, it is important that values of 1) the height H from a
desk top surface 2 to an eyepoint position E of an ocular OC, 2)
the angle (depression angle) .theta. at which the observer looks
into the ocular OC, and 3) the horizontal distance d from the
optical axis of an objective OB to the eyepoint position E of the
ocular are appropriately set for each observer. In order to allow
an observer of whatever build to perform long-time observation in a
natural posture, the eyepoint position E of the ocular OC is
required to be at the eyes of the observer under the condition
where the observer puts the hand on a focusing wheel 3 in a natural
posture. Regarding an ordinary microscope, the height of the
specimen surface 1 from the desk top surface 2 is 200 mm, and the
height of a lens barrel 4-side mount position 8 of a microscope
body 5 is 305 mm from the desk top surface 2. In FIG. 22, the
reference numeral 6 and the reference numeral 7 represent a
condenser lens and a stage control, respectively.
[0010] If a titling lens barrel proposed by Japanese Utility Model
Application Preliminary Publication (UM-KOKAI) No. 4-124218 is
combined with this microscope, the minimum height of the eyepoint
position E from the desk top surface 2 is approximately 400 mm.
Also, since the tilting lens barrel can change the depression angle
.theta., the height from the desk top surface 2 is variable
approximately in a range from 400 mm to 500 mm. Also, the distance
from the optical axis of the objective OB to the center position of
the focusing wheel 3 is approximately 100 mm. In the case of an
ordinary lens barrel, the eyepoint position E is distant from the
optical axis of the objective OB approximately by 195 mm. In the
case of a tilting lens barrel, which can change the depression
angle .theta., the horizontal distance is variable approximately in
a range from 140 mm to 195 mm.
[0011] If the depression angle .theta. is changed using the
above-mentioned tilting lens barrel, which simply changes the
depression angle, the horizontal distance from the optical axis of
the objective OB to the eyepoint position E is changed only by a
small amount. However, the horizontal distance becomes shorter as
the angle in reference to a horizontal plane is larger. This
correlation makes it impossible to allow any observer of whatever
build to perform observation in a natural posture. A tall and
large-built person requires a longer horizontal distance from the
optical axis of the objective and, as a matter of course, a higher
eyepoint position than a short and small-built person does. For
example, the optimum height of the eyepoint from the desk top
surface 2 for a person of 1580 mm height is approximately 430 mm,
whereas, for a person of 1840 mm height, the lowest necessary
height of the eyepoint is approximately 510 mm from the desk top
surface 2 and the optimum height of the eyepoint is approximately
600 mm from the desk top surface 2 on condition that the height of
the desk top surface 2 from the floor is 70 cm and the height of a
chair used during observation is appropriately adjusted. Therefore,
even if the eyepoint height is adjusted to the maximum height using
the conventional lens barrel 4, the person of 1840 mm height is
obliged to keep an unnatural posture. In addition, the horizontal
distance from the optical axis of the objective to the eyepoint
also is too short, and, as a result, the posture of the observer
looks as if he hunches over and hugs the microscope, to increase
fatigue during observation, which is a problem. Also, even if an
intermediate lens barrel is combined with the tilting lens barrel
for adjustment of the eyepoint height, the eyepoint is allowed to
be raised approximately by 60 mm at most, in effect. If the
eyepoint is set higher than this limit, eclipse or short amount of
marginal rays affects the image. As discussed above, use of the
tilting lens barrel obliges a tall and large-built person to take
an unnatural posture.
[0012] According to the lens barrel proposed by KOKAI No. Hei
10-142473, the depression angle and the eyepoint position are made
variable independent of each other. However, in the lens
arrangement of KOKAI No. Hei 10-142473, since a beam of rays from
the objective is designed to be relayed to the focal plane of the
ocular without imaging, a sufficiently long path length cannot be
secured in the lens barrel. Therefore, it is substantially
impossible to secure a sufficiently long horizontal distance from
the objective to the eyepoint while providing a wide variable range
of the eyepoint height for the above-mentioned adaptation of the
microscope to variously built observers.
[0013] Also, within the scope of this conventional proposal, if the
movable distance in the afocal section is designed to be long so as
to allow the eyepoint position to be largely spaced away, the
effective diameter through lenses and a binocular prism section
becomes larger with degraded aberration performance by off-axial
rays and the exit pupil position is largely displaced, to cause
eclipse at the ocular.
[0014] Alternatively, if a design is made so that the afocal
magnification of the first optical system and the second optical
system is large and that the focal length of the third optical
system is long for the purpose of spacing the eyepoint position
away, the angle of an off-axial ray emergent from the second
optical system becomes large, and, accordingly, the effective beam
diameter becomes large in and after the third optical system,
aberration performance on the margin is degraded, and inconsistency
of the exit pupil position occurs.
[0015] Furthermore, in the case where a unit for reflecting
illumination, a path dividing unit, a unit for raising the eyepoint
position or the like is additionally arranged in the system, a beam
diameter from the objective lens becomes large and accordingly
effective beam diameter in the first optical system, the second
optical system and the tilting mirror becomes large, to cause short
amount of marginal rays or eclipse. Therefore, it is difficult to
secure a long lens barrel length. If these optical systems are
constructed to be large for adaptation to the large effective beam
diameter, lenses cannot be arranged in a limited space.
[0016] To conclude, regarding the lens barrel proposed by KOKAI No.
Hei 10-142473, it is difficult to secure a sufficient horizontal
distance from the optical axis of the objective to the eyepoint
position. Also, the movable distance of the third optical system
using the afocal section is 30 mm at most. Therefore, it is
difficult to allow variously built observers, especially tall and
large-built persons, to take an optimum posture for observation. In
addition, this prior example fails to disclose particular numerical
data such as the height of the eyepoint position and the horizontal
distance from the optical axis of the objective to the eyepoint
position and thus its superiority to the conventional lens barrel
at that time is not clear.
[0017] Similarly, according to the proposal of KOKAI No. 9-73031
also, since movable range of the lens unit for changing the length
of the afocal beam of rays is physically limited, the eyepoint
position cannot be changed so large as to be well adapted to
variously built observers.
SUMMARY OF THE INVENTION
[0018] The present invention is made in consideration of the
aforementioned problems of the conventional art. An object of the
present invention is to provide a variable lens barrel which can
change the horizontal distance from the optical axis of the
objective to the eyepoint position, the height of the eyepoint, and
the depression angle for observation so that a person of any build
is able to perform observation in a natural posture causing little
fatigue and which can achieve system compatibility with
intermediate lens barrels etc. The present invention is directed to
a microscope using such a variable lens barrel, also.
[0019] In order to attain the above-mentioned objects, a lens
barrel according to the present invention comprises, in order from
the light incident side, a first optical system, a second optical
system which converts abeam of rays emergent from the first optical
system into a parallel beam of rays, and a third optical system
which introduces the beam of parallel rays emergent from the second
optical system into an ocular. The first optical system includes a
lens unit which forms an intermediate image and at least three
light deflecting members which deflect the beam of rays. The second
optical system includes a lens unit and a light deflecting member.
The light deflecting member of the second optical system is
constructed and arranged to turn around an axis that is
perpendicular to a first optical axis and a second optical axis,
where the center axis of the beam of rays emergent from the most
second optical system-side one of the light deflecting members of
the first optical system in optical arrangement is defined as the
first optical axis, and the center axis of the beam of parallel
rays emergent from the second optical system is defined as the
second optical axis.
[0020] According to this configuration, an intermediate image is
formed by the first optical system, is re-imaged by the second
optical system and the third optical system at the focal plane of
the ocular, and is observed. For image observation via the ocular
without eclipse, the entrance pupil position of the ocular is
required to substantially coincide with the exit pupil position of
the lens barrel. For this arrangement, it is necessary to form an
afocal system with the second optical system and the third optical
system. Under this condition, if each lens unit of the second
optical system and the third optical system is constructed with a
cemented lens, separation as much as F2+F3 is required between the
second optical system and the third optical system, where the focal
length of the second optical system is F2 and the focal length of
the third optical system is F3. Also, since the intermediate image
by the first optical system is converted into a beam of parallel
rays, if the lens unit of the first optical system is constructed
of a single lens, the separation between the first optical system
and the second optical system becomes F1+F2, where the focal length
of the first optical system is F1.
[0021] In this way, the configuration in which an intermediate
image is formed inside the lens barrel can secure a sufficiently
long path length of the optical systems arranged in the lens barrel
in comparison with a configuration without an intermediate image.
Accordingly, a wide variety of options are available regarding the
path layout inside the lens barrel, and thus higher flexibility is
assured in eyepoint position setting.
[0022] Also, since at least three optical members and, in addition,
an optical member that it to turn freely are arranged in the lens
barrel for deflecting the beam of rays, the beam of rays are
deflected four times inside the lens barrel, to allow observation
of a correctly erected image. Also, revolving movement of the light
deflecting member of the second optical system, the rear section of
the second optical system arranged behind the light deflecting
member of the second optical system, the third optical system and
the ocular allows adjustment of the depression angle for
observation.
[0023] Also, according to the present invention, the lens barrel is
constructed and arranged so that, when the light deflecting member
of the second optical system is turned by an angle of .alpha., a
rear section of the second optical system disposed behind the light
deflecting member of the second optical system, the third optical
system and the ocular are integrally revolved by an angle of
2.alpha..
[0024] According to this configuration, since the axis of the beam
of rays emergent from the light deflecting member of the second
optical system and the optical axis of the ocular always coincide,
correction of the depression angle in accordance with turn of the
light deflecting member is dispensable, to provide a highly
operable microscope.
[0025] Also, according to the present invention, the lens barrel is
constructed and arranged so that the separation between the second
optical system and the third optical system is variable along the
optical axis.
[0026] According to this configuration, it is possible to change
the eyepoint position by integrally moving the third optical system
and the ocular in the direction of the optical axis of the third
optical system. Also, as described above, the depression angle, at
which an observer looks into the ocular, can be changed by
revolving movement of the light deflecting member of the second
optical system. Therefore, combination of these features allows the
eyepoint position to be changed in height and in distance from the
optical axis of the objective.
[0027] Also, a lens barrel according to the present invention
comprises, in order from the light incident side, a first optical
system, a second optical system which converts a beam of rays
emergent from the first optical system into a beam of parallel
rays, and a third optical system which introduces the beam of
parallel rays emergent from the second optical system into an
ocular. The first optical system comprises a lens unit which forms
an intermediate image and at least four light deflecting members
which deflect the beam of rays. The separation between the second
optical system and the third optical system is variable in a
direction along the center axis of the beam of rays emergent from
the second optical system.
[0028] According to this configuration, as in the aforementioned
configuration, the intermediate image is formed by the first
optical system, is re-imaged by the second optical system and the
third optical system at the focal plane of the ocular, and is
observed. In this way, the configuration in which the intermediate
image is formed inside the lens barrel can secure a sufficiently
long path length of the optical systems arranged in the lens barrel
in comparison with a configuration without an intermediate image.
Accordingly, a wide variety of options are available regarding the
path layout inside the lens barrel, and thus higher flexibility is
assured in eyepoint position setting.
[0029] Also, in the lens barrel, at least four optical members and,
in addition, an optical member that it to turn freely are
constructed and arranged to deflect the beam of rays six times
inside the lens barrel, so that a correctly erect image can be
observed.
[0030] Furthermore, since the lens barrel is designed so that the
beam of rays traveling between the second optical system and the
third optical system is parallel, the imaging performance and the
image position do not change even if the separation between the
second optical system and the third optical system is changed.
Accordingly, the third optical system and the ocular are allowed to
integrally move in the direction of the optical axis of the third
optical system and thus the eyepoint position can be changed.
[0031] Also, according to the present invention, the third optical
system comprises, in order from the side of the second optical
system, a first lens unit having a positive refracting power, a
second lens unit having a negative refracting power, and a third
lens unit having a positive refracting power.
[0032] According to this configuration, since the separation
between the second optical system and the third optical system is
allowed to be shorter than in a configuration where the third
optical system is composed of a single lens (which may be a
cemented lens) and accordingly the pupil position of the ocular can
be set closer to the third optical system, a conventional ocular is
commonly usable or eclipse at the ocular is avoidable.
[0033] As will be described later in the first embodiment, in a
configuration where the third optical system is composed of a
single cemented lens, if the separation between the second optical
system and the third optical system is short, the pupil position at
the focal plane of the ocular comes closer to the ocular. As a
result, such a phenomenon as limits the optical performance of the
ocular, e.g., increase in effective diameter of the ocular, eclipse
on the margin, takes place. In addition, since a large separation
is necessary between the second optical system and the third
optical system, the path length of the entire system becomes long,
to cause bulkiness of the lens barrel itself. In contrast, in the
above-mentioned configuration where the third optical system is
composed of three lens units of positive-negative-positive, a path
length (space) to accommodate the prism section can be secured in
the lens barrel. Furthermore, this configuration can reduce change
of the entrance pupil position on the side of the objective, which
would be caused by use in combination with an intermediate lens
barrel, and fluctuation of the exit pupil, which would be caused in
accordance with integral movement of the third optical system
through the ocular. Also, eclipse or short amount of marginal rays
can be prevented without increase in the effective diameter of each
lens arranged in the third optical system through the ocular. In
addition, since the total path length can be shortened, compact
sizing of the entire lens barrel can be realized.
[0034] Also, in the third optical system of the present invention,
the first lens unit comprises at least one positive meniscus lens
which directs a concave surface thereof toward the second lens
unit, and the third lens unit comprises at least one positive
meniscus lens which directs a concave surface thereof toward the
second lens unit.
[0035] This configuration can well reduce generation of aberrations
caused by off-axial rays and can maintain the performance in good
condition regarding off-axial aberrations, which would be affected
by fluctuation of the exit pupil position in accordance with the
integral movement of the third optical system through the
ocular.
[0036] Also, the lens barrel according to the present invention is
constructed and arranged to satisfy the condition:
0.7.ltoreq.F1/F.ltoreq.1.4
[0037] where F1 is the focal length of the first optical system,
and F is the focal length of the entire system from the first
optical system through the third optical system.
[0038] According to this configuration, The lens barrel can be made
compact, without increase in lens diameter or unnecessary
prolongation of the path length inside the lens barrel.
Furthermore, the horizontal distance from the optical axis of the
objective to the eyepoint position can be set long. Furthermore,
regarding the eyepoint height, it can be set higher than in the
case of the conventional lens barrel. Furthermore, combination with
the above-mentioned configuration in which the third optical system
through the ocular are integrally movable allows the horizontal
distance from the optical axis of the objective to the eyepoint
position to be largely changed and allows the depression angle also
to be changed. As a result, the eyepoint position can be set more
flexibly in a wider range and thus the observer of whatever build
can take an ideal posture for observation.
[0039] If F1/F falls below the lower limit of the condition in the
case where the value of the focal length F2 of the second optical
system is larger than F1, the focal length F3 (=(F2/F1).times.F) of
the third optical system becomes longer than F and accordingly the
length from the third lens unit to the ocular becomes long. Under
this condition, since the eyepoint position is too distant from the
optical axis of the objective, appropriate posture for observation
cannot be taken. In the case where the value of F2 is smaller than
F1, while the path length can be made short, aberrations cannot be
compensated in good condition or a field lens for adjustment of the
pupil position is necessitated, to result in increase in number of
lenses and accordingly cost rise of the products.
[0040] Also, if an intermediate lens barrel is interposed between
the infinity distance correcting objective and the lens barrel, to
widen the separation between, eclipse or degradation of the
off-axial aberration performance would be caused. Therefore, too
small value of F1/F is not preferable in view of system
compatibility also.
[0041] If F1/F exceeds the upper limit of the condition in the case
where the value of F2 is smaller than F1, F3 also becomes small,
and accordingly a sufficient path length cannot be secured in the
binocular section as to accommodate the prisms. Also, the lens
diameter of the third optical system and the prism size of the
binocular section are obliged to be large. As a result, the parts
used in the lens barrel cannot be standardized with the parts of
the conventional binocular section, to raise cost of the products.
Also, under the condition where the separation between the infinity
distance correcting objective and the lens barrel is small, the
pupil position is not properly located and thus eclipse or
degradation of aberration performance on the margin occurs.
Therefore, too large value of F1/F is not preferable.
[0042] Also, the lens barrel according to the present invention is
configured to satisfy the following condition:
0.5.ltoreq.F3/F.ltoreq.1
[0043] where F3 is the focal length of the third optical
system.
[0044] This configuration allows aberrations to be compensated in
good condition. Therefore, eclipse of the field or short amount of
light on the margin resulting from shift of the pupil position less
occurs even if the pupil position is changed in accordance with
integral movement of the third optical system through the ocular or
with interposition of an intermediate lens barrel unit between the
objective and the lens barrel. Also, layout of the path of rays in
the lens barrel can be made compact and the eyepoint can be set at
a position more distant than in the case of the conventional lens
barrel. Therefore, this configuration is preferable.
[0045] If F3/F falls below the lower limit of the condition, the
path length in the lens barrel becomes extremely long to cause
bulkiness of the lens barrel or, alternatively, F3 is made short
and accordingly a sufficient path length cannot be secured between
the third optical system and the ocular. Also, the pupil position
cannot substantially coincide with the entrance pupil position of
the ocular and accordingly eclipse or degradation of off-axial
aberration performance is caused.
[0046] If F3/F exceeds the upper limit of the condition, since the
F3 is long and accordingly the path length from the third optical
system to the ocular becomes long, the eyepoint position is too
distant from the optical axis of the objective, and, in addition,
the total path length also becomes long, to result in bulkiness of
the lens barrel. Therefore, too large value of F3/F is not
preferable. Also, since the pupil position cannot substantially
coincide with the entrance pupil position of the ocular,
unfavorable phenomenon such as eclipse or degradation of off-axial
aberration performance occurs as in the case where F3/F is below
the lower limit.
[0047] This and other objects as well as features and advantages of
the present invention will become apparent from the following
detailed description of the preferred embodiments when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 shows the configuration of a variable lens barrel
according to the first embodiment of the present invention.
[0049] FIG. 2 shows the configuration of a variable lens barrel
according to the second embodiment of the present invention.
[0050] FIG. 3 shows the configuration of a modification example of
the second embodiment.
[0051] FIG. 4 shows the configuration of another modification
example of the second embodiment.
[0052] FIG. 5 shows the configuration of still another modification
example of the second embodiment.
[0053] FIG. 6 shows the configuration of a variable lens barrel
according to the third embodiment of the present invention.
[0054] FIGS. 7A-7D are path diagrams in which the path of rays
according to the third embodiment is schematically exploded
linearly, where FIG. 7A shows the case where D.sub.0=60 mm and
D.sub.1=0, FIG. 7B shows the case where D.sub.0=60 mm and
D.sub.1=45 mm, FIG. 7C shows the case where D.sub.0=170 mm and
D.sub.1=0, and FIG. 7D shows the case where D.sub.0=170 mm and
D.sub.1=45 mm.
[0055] FIGS. 8A-8E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 7A of the third
embodiment.
[0056] FIGS. 9A-9E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 7B of the third
embodiment.
[0057] FIGS. 10A-10E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 7C of the third
embodiment.
[0058] FIGS. 11A-11E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 7D of the third
embodiment.
[0059] FIGS. 12A-12D are path diagrams in which the path of rays
according to the fourth embodiment is schematically exploded
linearly, where FIG. 12A shows the case where D.sub.0=60 mm and
D.sub.1=0, FIG. 12B shows the case where D.sub.0=60 mm and
D.sub.1=45 mm, FIG. 12C shows the case where D.sub.0=170 mm and
D.sub.1=0, and FIG. 12D shows the case where D.sub.0=170 mm and
D.sub.1=45 mm.
[0060] FIGS. 13A-13E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 12A of the
fourth embodiment.
[0061] FIGS. 14A-14E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 12B of the
fourth embodiment.
[0062] FIGS. 15A-15E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 12C of the
fourth embodiment.
[0063] FIGS. 16A-16E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 12D of the
fourth embodiment.
[0064] FIGS. 17A-17D are path diagrams in which the path of rays
according to the fifth embodiment is schematically exploded
linearly, where FIG. 17A shows the case where D.sub.0=60 mm and
D.sub.1=0, FIG. 17B shows the case where D.sub.0=60 mm and
D.sub.1=45 mm, FIG. 17C shows the case where D.sub.0=170 mm and
D.sub.1=0, and FIG. 17D shows the case where D.sub.0=170 mm and
D.sub.1=45 mm.
[0065] FIGS. 18A-18E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 17A of the fifth
embodiment.
[0066] FIGS. 19A-19E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 17B of the fifth
embodiment.
[0067] FIGS. 20A-20E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 17C of the fifth
embodiment.
[0068] FIGS. 21A-21E are aberration diagrams showing aberration
performance at the ocular in the condition of FIG. 17D of the fifth
embodiment.
[0069] FIG. 22 is a schematic side view of an ordinary conventional
microscope.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0070] First Embodiment
[0071] In reference FIG. 1, description will be made of the first
embodiment of the variable lens barrel according to the present
invention. According to this embodiment, light from the specimen
surface 1 is converted into an infinite distance beam of rays by an
infinite distance correcting objective OB and is observed via a
variable lens barrel and an ocular OC. The variable lens barrel
comprises, in order from the side of the objective OB, a first
optical system G1, a second optical system G2, and a third optical
system G3. The first optical system comprises a first lens unit G1L
which converges the beam of rays from the objective OB, a prism P1
which deflects the beam of rays from the first lens unit G1L by
90.degree. so that the beam of rays travels horizontal and away
from an observer (or the ocular OC), and deflecting mirrors M1, M2
which deflect the beam of rays from the prism P1 by 90.degree. by
reflecting it twice so that the beam of rays emerges in a vertical
direction. The second optical system G2 comprises a turnable
deflecting mirror M3 which deflects the beam of rays from the
deflecting mirror M2 toward the observer and a lens unit which
converts an intermediate image formed by the first lens unit G1L
into a beam of parallel rays. The third optical system G3 re-images
the intermediate image. The re-formed image is observed via the
ocular OC. A binocular section including a prism section is not
shown in the figure. The turnable deflecting mirror M3 is
constructed and arranged to turn around an axis that passes an
intersection P of a first optical axis and a second optical axis
and that is perpendicular to a plane on which the deflecting mirror
M2 and the second optical axis lie, where a center axis of the beam
of rays emergent from the deflecting mirror M2 is defined as the
first optical axis, and a center axis of the beam of rays emergent
from the second optical system G2 is defined as the second optical
axis. The rear section of the second optical system G2, or the lens
unit of the second optical system G2 disposed behind the deflecting
mirror M3, the third optical system G3, the binocular section and
the ocular OC are constructed and arranged to revolve around the
point P.
[0072] Since the first embodiment is thus configured, the beam of
the rays from the objective OB is converged by the first lens unit
G1L, deflected by the prism P1 in the horizontal direction, and is
deflected by the two deflecting mirrors M1, M2 in the vertical
direction. The intermediate image IO is formed by the first lens
unit G1L between the deflecting mirrors M1 and M2. The intermediate
image IO is converted into the beam of parallel rays by the second
optical system G2 and re-imaged by the third optical system G3 at
the focal position I of the ocular OC. In this configuration, if
the rear section of the second optical system G2, the third optical
system G3, the binocular section and the ocular OC are integrally
revolved about the axis that is perpendicular to the plane on which
the first optical axis and the second optical axis lie and that
passes the point P, the depression angle for observation is
adjusted by the mirror M3. Also, if the lens barrel is configured
so that the rear section of the second optical system G2, the third
optical system G3, the binocular section and the ocular OC are
integrally revolved by an angle 2.alpha. in accordance with turn of
the deflecting mirror M3 by an angle .alpha., observation can be
performed without shift of the center position of the observation
field.
[0073] In the configuration where an intermediate image is formed
inside the lens barrel in this way, since the path length can be
secured sufficiently long in the lens barrel, the position of the
point P can be substantially freely set upon appropriate setting of
the positions of the four deflecting members, i. e. the three
deflecting members (the prism P1 and the deflecting mirrors M1, M2)
of the first optical system G1 and the deflecting mirror M3 of the
second optical system G2. Accordingly, the horizontal distance of
the eyepoint from the optical axis of the objective OB or from the
center of the focusing wheel 3 and the eyepoint height (i. e. the
eyepoint position E) can be appropriately adjusted.
[0074] Also, since at least three optical members and, in addition,
an optical member that is to turn freely are arranged in the lens
barrel for deflecting the beam of rays, reflection occurs four
times inside the lens barrel while relay of the intermediate image
takes place only once, to allow observation of a correctly erected
image. Also, in accordance with the turn of the deflecting mirror
M3 around the point P, the rear section of the second optical
system G2, the third optical system G3, the binocular section and
the ocular OC are integrally revolved around the point P to achieve
flexible adjustment of the depression angle for observation.
Therefore, the eyepoint height is freely changeable. In this way,
if the configuration of the present invention is employed, more
appropriate setting of the eyepoint position is realized in
comparison with the conventional tilting lens barrel. Adjustment of
the eyepoint position E can be made also by changing the separation
d.sub.0 from the infinite distance correcting objective OB to the
first lens unit G1L by means of insertion and removal of an
intermediate lens barrel unit or the like.
[0075] Second Embodiment
[0076] In reference to FIG. 2, description will be made of the
variable lens barrel according to the second embodiment of the
present invention. This embodiment differs from the first
embodiment in that the separation between the second optical system
G2 and the third optical system G3 is changeable. The substantially
same members as in the first embodiment are represented by the same
reference symbols and explanation is omitted here regarding the
same structure and function as in the first embodiment. In this
embodiment, the third optical system G3, the binocular section and
the ocular OC are integrally shifted in the direction along the
second optical axis to change the separation D.sub.1 between the
second optical system G2 and the third optical system G3. Since the
second optical system G2 through the third optical system G3 are
made afocal, the eyepoint position E can be changed without change
of the image position or the magnification even if the third
optical system G3 performs the above-mentioned movement. Therefore,
according to this embodiment, the horizontal distance from the
eyepoint position E to the optical axis of the objective or to the
focusing wheel 3 and the eyepoint height are flexibly adjustable by
means of integral shift of the third optical system G3, the
binocular section and the ocular OC for adaptation to the build of
the observer, in addition to the change of the eyepoint position by
means of the same operation as in the first embodiment.
[0077] As in the modification examples shown in FIGS. 3, 4 and 5,
the second embodiment can be variously modified. These modification
examples differ from each other in the arrangement of the first
optical system G1. To be specific, according to the FIG. 3 example,
a prism P1, a deflecting mirror M1, deflecting prisms P2, P3 and
the turnable deflecting mirror M2 form the deflecting members so
that reflection occurs six times, to allow a correctly erected
image to be observed. According to the FIG. 4 example, a deflecting
prism P1', deflecting mirrors M1, M2 and a turnable deflecting
mirror M3 form the deflecting members so that reflection occurs
four times, to allow a correctly erected image to be observed.
According to the FIG. 5 example, a prism P1, deflecting mirrors M1,
M2 and a turnable deflecting mirror M3 form the deflecting members
so that reflection occurs four times, to allow a correctly erected
image to be observed. These modified examples are applicable to the
first embodiment, as a matter of course.
[0078] Third Embodiment
[0079] In reference to FIG. 6, FIGS. 7A-7D, 8A-8E through 11A-11E,
description will be made of the variable lens barrel according to
the third embodiment of the present invention. According to this
embodiment, the third optical system G3 comprises, in order from
the side of the second optical system G2, a single meniscus lens
unit L31 with a positive refracting power, a lens unit L32 with a
negative refracting power, and a lens unit L33 with a positive
refracting power including a single meniscus lens with a positive
refracting power. Other structures, functions and effects are
fundamentally similar to the second embodiment. According to the
third embodiment, since the three lens-unit structure of the third
optical system G3 allows the image position at the focal plane of
the ocular OC to be close to the third optical system G3 even if
the separation between the second optical system G2 and the third
optical system G3 is shorter than the sum of the focal length F2 of
the second optical system and the focal length F3 of the third
optical system, the path length can be made short, to realize a
compact lens barrel. As a result, the lens barrel is compatible
with a conventional ocular in a microscope or the eclipse at the
ocular can be prevented.
[0080] According to the above-mentioned configuration of the third
optical system, as is understood from the paraxial amounts shown in
the lens data below, even under the variable condition regarding
the separation D.sub.0 between the objective OB and the first
optical system G1 and the separation D.sub.1 between the second
optical system G2 and the third optical system G3, change of the
entrance pupil position on the objective side and the fluctuation
of the exit pupil position are reduced while the path length in the
binocular section for prism arrangement is secured, and the short
amount of marginal off-axial rays and the eclipse can be prevented
without increase in effective diameter of each lens in the third
optical system G3 through the ocular OC.
[0081] The focal length F1 of the first optical system G1 is 180
mm, the focal length F2 of the second optical system G2 is 135.68
mm, the focal length F3 of the third optical system G3 is 135.68
mm, and the focal length F of the entire system is 180 mm. Since
F1/F =1, the condition 0.7.ltoreq.F1/F.ltoreq.1.4 is satisfied.
Furthermore, since F3/F=0.75, the condition
0.5.ltoreq.F3/F.ltoreq.1 also is satisfied.
[0082] Even if the separation D.sub.0 between the objective OB and
the first optical system G1, or the space for the intermediate lens
barrel unit, and the separation D.sub.1 between the second optical
system G2 and the third optical system G3 are changed as shown in
the exploded view of the path shown in FIGS. 7A-7D, the aberrations
at the focal plane of the ocular OC are well compensated in either
condition, as shown in the corresponding aberration diagrams.
Therefore, observation is always facilitated by good optical
performance even if the eyepoint position E is changed. The
aberration diagrams shown in FIGS. 8A-8E, FIGS. 9A-9E, FIGS.
10A-10E, and FIGS. 11A-11E correspond to the conditions shown in
FIG. 7A, FIG. 7B, FIG. 7C and FIG. 7D, respectively.
[0083] In the optical arrangement shown in FIG. 6, where D.sub.0=60
mm, the depression angle .theta. is variable in the range from
0.degree. (horizontal position) to 25.degree. (position shown by
the dot & dash line), the height of the eyepoint position E
from the lens barrel side mount position 8 is in the range of 110.4
mm-259.5 mm, the height from the specimen surface 1 to the lens
barrel side mount position 8 is 105 mm, the height from the desk
top surface 2 (see FIG. 22) to the specimen surface 1 is 200 mm,
the height H from the desk top surface 2 to the eyepoint position E
is in the range of 415.4 mm-564.5 mm, and the horizontal distance d
from the optical axis of the objective to the eyepoint position E
is in the range of 201.2 mm-265 mm. Where D.sub.0=170, the height
from the desk top surface 2 to the lens barrel side mount position
8 is 415 mm, and the height H from the desk top surface 2 to the
eyepoint position E is in the range of 525.4 mm-674.5 mm.
[0084] In this way, if the lens barrel of this embodiment is
combined with an ordinary microscope, the height of the eyepoint
position E from the desk top surface is variable approximately in
the range of 410 mm-565 mm and the horizontal distance from the
optical axis of the objective to the eyepoint position E is
variable approximately in the range of 201 mm-265 mm because the
eyepoint position E can be shifted substantially from the same
position as with the conventional lens barrel by 45 mm along the
center axis of the beam of rays emergent from the second optical
system G2 away from the optical axis of the objective and the
depression angle .theta. also is changeable. Therefore, variously
built persons--from a short and small-built person to a tall and
large-built person--can perform observation in an natural and
relaxed posture. Furthermore, if an intermediate lens barrel unit
or the like is combined, the height of the eyepoint position E can
be further heightened by 110 mm, to achieve the maximum eyepoint
height of 675 mm. As a result, both of the height of the eyepoint
and the horizontal distance from the optical axis of the objective
can be widened in reference to the eyepoint position of the
conventional tilting lens barrel, and thus the microscope is well
adaptable to a large-built person.
[0085] Also, the optical arrangement in the lens barrel may be any
one of those shown in FIG. 3, FIG. 4 and FIG. 5 as long as the
optical path length is kept constant. According to the
configuration of the present embodiment, since the focal length F1
of the first optical system G1 equals to the focal length F of the
entire system, a path dividing element such as a prism may be
removably mounted between the first optical system G1 and the
second optical system G2 for providing a photographing path. Also,
in the configuration of FIG. 6, the deflecting mirror M1 may be
configured to achieve removable mount or may be constructed with a
half mirror, so as to introduce the intermediate image toward is
the photographing path.
[0086] The lens data and the optical paraxial amounts of the lens
barrel according to the present embodiment are presented below. In
the lens data, the surface arrangement number 0 corresponds to an
imaginary object surface, not shown in FIGS. 7A-7D, indicating that
the object is located at the infinite distance, the surface
arrangement number 1 corresponds to the entrance pupil position of
this optical system which appears at the leftmost position in FIGS.
7A-7D. The surfaces denoted by the subsequent surface arrangement
numbers are shown in FIGS. 7A-7D in order from the left side. The
surface arrangement number 3 corresponds to an imaginary surface
indicating the mount position of the objective. The surface
arrangement number 4 corresponds to the mount position of the lens
barrel which supports this optical system. The surface arrangement
numbers 4-6 correspond to the surfaces of the first lens unit G1L.
The surface arrangement numbers 7-9 correspond to the surfaces of
the prism P1, where the number 7 corresponds to an entrance
surface, the number 8 corresponds to a reflecting surface, and the
number 9 corresponds to an exit surface. The surface arrangement
numbers 10-12 correspond to the mirrors M1, M2 and M3,
respectively. The surface arrangement numbers 13-15 correspond to
surfaces of the lens unit of the second optical system. The surface
arrangement number 16 corresponds to an imaginary surface. In the
third optical system, the surface arrangement numbers 17-18
correspond to the surfaces of the lens L31, the surface arrangement
numbers 19-20 correspond to the surfaces of the lens L32, and the
surface arrangement numbers 21-25 correspond to the surfaces of the
lens unit L33. The surface arrangement numbers 26-27 correspond to
the surfaces of the prism in the binocular section. The surface
arrangement number 28 corresponds to the image position.
1 F1 = 180 mm Surface Radius of Refractive Index Vd Arrange.No.
Curvature Separation (n) (587.56 nm) (Abbe's Number) 0 (OBJ) INF
INF 1 1 (ENP) INF 8 1 2 (IMAGINARY) INF 60 1 3 (IMAGINARY) INF
20.39 1 4 146.7488 4 1.48749 70.23 5 -64.4255 4.6 1.7495 35.28 6
-118.8028 12.0681 1 7 INF 17 1.51633 64.14 8 INF 17 1.51633 64.14 9
INF 94.1134 1 10 (M1) INF 39.7582 1 11 (M2) INF 104.1134 1 12 (M3)
INF 35.2444 1 13 191.392 7.4 1.48749 70.23 14 -42.135 4.05 1.72825
28.46 15 -69.213 14.6 1 16 (IMAGINARY) INF D.sub.1 (variable) 1 17
38.939 5.4 1.48749 70.23 18 303.576 47.55 1 19 -17.507 1.8 1.64769
33.79 20 62.517 23.569 1 21 -48.734 3.7 1.6779 55.34 22 -25.167 0.4
1 23 63.383 3 1.7495 35.28 24 31.369 4.9 1.56384 60.67 25 -130.265
3.93 1 26 INF 91 1.56883 56.36 27 INF 29.6541 28 (IMG) INF 0
D.sub.1 (variable): 0.about.45 mm
[0087] vertex of the first lens unit G1L to the image surface:
568.85 mm
2 Paraxial Amount D.sub.0 60 60 170 170 D.sub.1 0 45 0 45 G1 alone
Entrance pupil radius 7.2 7.2 7.2 7.2 7.2 Image height 11 11 11 11
11 Focal length 180 180 180 180 180 Exit pupil position -123.8
-177.2 -213 -443.1 -226 Exit pupil radius 4.9 7.1 8.5 17.7 14.8
[0088] Fourth Embodiment
[0089] The present embodiment has the optical arrangement similar
to the third embodiment (see FIG. 6), but differs in that the focal
length F1 of the first optical system G1 is configured to be longer
than the focal length F of the entire system. According to this
embodiment, the focal length F1 of the first optical system G1 is
215 mm, the focal length F2 of the second optical system is 115.4
mm, the focal length F3 of the third optical system G3 is 96.62 mm,
and the focal length F of the entire system is 180 mm, Since
F1/F=1.19, the condition 0.7.ltoreq.F1/F.ltoreq.1- .4 is satisfied.
Furthermore, since F3/F=0.54, the condition
0.5.ltoreq.F3/F.ltoreq.1 also is satisfied.
[0090] According to the present embodiment, as in the case of the
third embodiment, even if the separation D.sub.0 between the
objective OB and the first optical system G1, or the space for the
intermediate lens barrel unit, and the separation D.sub.1 between
the second optical system G2 and the third optical system G3 are
changed as shown in the exploded view of the path shown in FIGS.
12A-12D, the aberrations at the focal plane of the ocular OC are
well compensated in either condition, as shown in the corresponding
aberration diagrams. Also, the present embodiment is good at system
compatibility.
[0091] The aberration diagrams shown in FIGS. 13A-13E, FIGS.
14A-14E, FIGS. 15A-15E, and FIGS. 16A-16E correspond to the
conditions shown in FIG. 12A, FIG. 12B, FIG. 12C and FIG. 12D,
respectively. Also, as is obvious from the lens data below, the
optical path length of the entire lens barrel optical system is
substantially the same as in the case of the third embodiment, and
thus application of the layout similar to the third embodiment
allows variously built observers to take a natural posture. Also,
the layout shown in any one of FIG. 3. FIG. 4, FIG. 5 is applicable
to the fourth embodiment, as a matter of course.
[0092] The lens data and the optical paraxial amounts of the lens
barrel according to the present embodiment are presented below.
Correspondence of the surface arrangement numbers to the surfaces
is the same as the third embodiment, and thus explanation about
them is omitted.
3 F1 = 215 mm Surface Radius of Refractive Index Vd Arrange.No.
Curvature Separation (n) (587.56 nm) (Abbe's Number) 0 (OBJ) INF
INF 1 1 (ENT) INF 8 1 2 (IMAGINARY) INF 60 1 3 (IMAGINARY) INF 35 1
4 93.526 7.3 1.48749 70.23 5 -118.961 5.95 1.7495 35.28 6 -455.864
9.869 1 7 INF 17 1.51633 64.14 8 INF 17 1.51633 64.14 9 INF 94.1134
1 10 (M1) INF 39.7582 1 11 (M2) INF 104.1134 1 12 (M3) INF 46.9336
1 13 125.461 7.4 1.48749 70.23 14 -50.486 4.05 1.72825 28.46 15
-75.666 6.312 1 16 (IMAGINARY) INF D.sub.1 (variable) 1 17 41.531
5.4 1.48749 70.23 18 194.44 46.9843 1 19 -18.936 1.9 1.6727 32.1 20
41.156 23.4596 1 21 -114.12 4 1.788 47.37 22 -28.387 0.4 1 23
62.323 3 1.7495 35.28 24 26.871 5.25 1.48749 70.23 25 -106.711
3.7951 1 26 INF 91 1.56883 56.36 27 INF 30 1 28 (IMG) INF 0 D.sub.1
(variable): 0.about.45 mm
[0093] vertex of the first lens unit G1L to the image surface:
574.99 mm
4 Paraxial Amount D.sub.0 60 60 170 170 D.sub.1 0 45 0 45 G1 alone
Entrance pupil radius 7.2 7.2 7.2 7.2 7.2 Image height 11 11 11 11
11 Focal length 180 180 180 180 215 Exit pupil position -112.5
-245.6 -181.9 -1478.4 -240 Exit pupil radius 4.5 9.8 7.3 59.1
13.9
[0094] Fifth Embodiment
[0095] The present embodiment has the optical arrangement similar
to the third embodiment (see FIG. 6), but differs from the third or
fourth embodiment in that the focal length F1 of the first optical
system G1 is configured to be shorter than the focal length F of
the entire system. According to this embodiment, the focal length
F1 of the first optical system G1 is 160 mm, the focal length F2 of
the second optical system is 153.16 mm, the focal length F3 of the
third optical system G3 is 172.3 mm, and the focal length F of the
entire system is 180 mm, Since F1/F=0.89, the condition
0.7.ltoreq.F1/F.ltoreq.1.4 is satisfied. Furthermore, since
F3/F=0.957, the condition 0.5.ltoreq.F3/F.ltoreq.1 also is
satisfied.
[0096] According to the present embodiment, as in the case of the
third embodiment, even if the separation D.sub.0 between the
objective OB and the first optical system G1, or the space for the
intermediate lens barrel unit, and the separation D.sub.1 between
the second optical system G2 and the third optical system G3 are
changed as shown in the exploded view of the path shown in FIGS.
17A-17D, the aberrations at the focal plane of the ocular OC are
well compensated in either condition, as shown in the corresponding
aberration diagrams. Also, the present embodiment is good at system
compatibility.
[0097] The aberration diagrams shown in FIGS. 18A-18E, FIGS.
19A-19E, FIGS. 20A-20E, and FIGS. 21A-21E correspond to the
conditions shown in FIG. 17A, FIG. 17B, FIG. 17C and FIG. 17D,
respectively. Also, as is obvious from the lens data below, the
optical path length of the entire lens barrel optical system is
substantially the same as in the case of the third embodiment, and
thus application of the layout similar to the third embodiment
allows variously built observers to take a natural posture. Also,
the layout shown in any one of FIG. 3. FIG. 4, FIG. 5 is applicable
to the fifth embodiment, as a matter of course.
[0098] The lens data and the optical paraxial amounts of the lens
barrel according to the present embodiment are presented below.
Correspondence of the surface arrangement numbers to the surfaces
is the same as the third embodiment, and thus explanation about
them is omitted.
5 F1 = 160 mm Surface Radius of Refractive Index Vd Arrange.No.
Curvature Separation (n) (587.56 nm) (Abbe's Number) 0 (OBJ) INF
INF 1 1 (ENT) INF 8 1 2 (IMAGINARY) INF 60 1 3 (IMAGINARY) INF 35 1
4 143.034 5 1.48749 70.23 5 -58.001 4.4 1.7495 35.28 6 -101.666
4.3529 1 7 INF 17 1.51633 64.14 8 INF 17 1.51633 64.14 9 INF
94.1134 1 10 (M1) INF 39.7582 1 11 (M2) INF 104.1134 1 12 (M3) INF
41.4164 1 13 156.798 7.4 1.48749 70.23 14 -50.373 4 1.72151 29.23
15 -89.166 6.1626 1 16 (IMAGINARY) INF D.sub.1 (variable) 1 17
39.608 5.4 1.48749 70.23 18 346.666 47.7192 1 19 -19.962 2.35
1.6727 32.1 20 599.477 24.309 1 21 -61.53 3.8 1.6779 55.34 22
-32.636 0.4 1 23 518.19 3.95 1.6393 44.87 24 32.11 6.1 1.57135
52.95 25 -67.13 6.5109 1 26 INF 91 1.56883 56.36 27 INF 30 1 28
(IMG) INF 0 D.sub.1 (variable): 0.about.45 mm
[0099] vertex of the first lens unit G1L to the image surface:
566.25 mm
6 Paraxial Amount D.sub.0 60 60 170 170 D.sub.1 0 45 0 45 G1 alone
Entrance pupil radius 7.2 7.2 7.2 7.2 7.2 Image height 11 11 11 11
11 Focal length 180 180 180 180 160 Exit pupil position -120 -146.7
-202.2 -292.2 -356.2 Exit pupil radius 4.8 5.9 8.1 11.7 22
[0100] In the aberration diagrams of the third to fifth
embodiments, the broken line presents aberration performance at the
wavelength of 435.84 nm, the single dot and dash line presents
aberration performance at the wavelength of 486.13 nm, the dotted
line presents aberration performance at the wavelength of 656.27
nm, and the solid line presents aberration performance at the
wavelength of 587.56 nm.
[0101] As described above, the present invention is able to provide
a variable lens barrel which can change the eyepoint position by a
large amount in comparison with the conventional lens barrel or a
tilting lens barrel, to allow variously-built persons,--from tall
persons to small-built persons--to perform observation in a natural
and relaxed posture and thus which is effective in relieving
fatigue, and which is favorable in view of system compatibility
with an intermediate lens barrel unit or the like. The present
invention is able to provide a microscope using this variable lens
barrel, also.
* * * * *