U.S. patent application number 09/945674 was filed with the patent office on 2002-05-02 for eyepiece lens.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Mouri, Motohisa, Nozaki, Hitoshi, Oshita, Kouichi.
Application Number | 20020051300 09/945674 |
Document ID | / |
Family ID | 27344553 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020051300 |
Kind Code |
A1 |
Mouri, Motohisa ; et
al. |
May 2, 2002 |
Eyepiece lens
Abstract
In order to provide an eyepiece lens which has a sufficiently
long eye relief and a high magnification, there is provided an
eyepiece lens for observing an image formed by an objective lens
through an erect system, at least comprising a first lens group 4
having a positive refracting power and a second lens group 3 having
a negative refracting power in this order from the side of an
observer, and satisfying the following condition: -3<SF1<-1
(1) where SF1 indicates a shape factor of the first lens group 4,
and SF indicates a shape factor of the lens group, which is defined
by: SF=(Rs+RE)/(Rs-RE), where Rs indicates a radius of curvature of
a lens surface which is closest to the object side and RE indicates
a radius of curvature of a lens surface which is closest to the
observer side.
Inventors: |
Mouri, Motohisa;
(Kawasaki-shi, JP) ; Oshita, Kouichi; (Tokyo,
JP) ; Nozaki, Hitoshi; (Natori-shi, JP) |
Correspondence
Address: |
MILES & STOCKBRIDGE PC
1751 PINNACLE DRIVE
SUITE 500
MCLEAN
VA
22102-3833
US
|
Assignee: |
Nikon Corporation
|
Family ID: |
27344553 |
Appl. No.: |
09/945674 |
Filed: |
September 5, 2001 |
Current U.S.
Class: |
359/646 ;
359/645 |
Current CPC
Class: |
G02B 25/001
20130101 |
Class at
Publication: |
359/646 ;
359/645 |
International
Class: |
G02B 025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2000 |
JP |
2000-269193 |
Sep 6, 2000 |
JP |
2000-270687 |
Aug 23, 2001 |
JP |
2001-252345 |
Claims
What is claimed is:
1. An eyepiece lens for observing an image formed by an objective
lens through an erect system, at least comprising a first lens
group having a positive refracting power and a second lens group
having a negative refracting power in the order from the side of an
observer, and satisfying the following condition:-3<SF1<-1
(1)where SF1 indicates a shape factor of said first lens group, and
SF indicates a shape factor of the lens group, which is defined
by:SF=(Rs+RE)/(Rs-RE),wh- ere Rs indicates a radius of curvature of
a lens surface which is closest to the object side and RE indicates
a radius of curvature of a lens surface which is closest to the
observer side.
2. An eyepiece lens according to claim 1, wherein said second lens
group satisfies the following condition:1<SF2<6 (2)where SF2
indicates the shape factor of said second lens group.
3. An eyepiece lens according to claim 2, wherein said second lens
group is comprised of at least a lens group having a negative
refracting power and a lens group having a positive refracting
power in the order from the observer side, and said positive lens
group in said second lens group satisfies the following
condition:-2<SF2p<-1 (3)where SF2p indicates the shape factor
of said positive lens group in said second lens group.
4. An eyepiece lens according to claim 1, wherein said first lens
group having the positive refracting power or a lens component
having a positive refracting power in said first lens group is
moved along the optical axis so as to adjust the diopter.
5. An eyepiece lens according to claim 3, wherein said negative
lens group for satisfying the following condition in said second
lens group is moved along the optical axis so as to adjust the
diopter:0.5<.vertline.f2n.v- ertline./f1<1 (4)where f2n
indicates a focal length of said negative lens group in said second
lens group, and f1 indicates a focal length of said first lens
group.
6. An eyepiece lens according to claim 1, wherein at least one lens
group in said lens group satisfies the following
condition:Dx/fe.gtoreq.0.08 (5)where Dx indicates a thickness of
the lens group, and fe indicates a focal length of said eyepiece
lens at the dopier of -1.
7. An eyepiece lens according to claim 1, wherein a condenser lens
satisfying the following condition is inserted between an imaging
surface and the erect system:1<fc/fe<3 (6)where fc indicates
a focal length of the condenser lens, and fe indicates a focal
length of the entire eyepiece lens at the diopter of -1.
8. An eyepiece lens according to claim 1, wherein said second lens
group is comprised of at least a lens group having a negative
refracting power and a lens group having a positive refracting
power in the order from the observer side, and said positive lens
group in said second lens group satisfies the following
condition:-2<SF2p<-1 (3)where SF2p indicates the shape factor
of said positive lens group in said second lens group.
9. An eyepiece lens according to claim 8, wherein said negative
lens group for satisfying the following condition in said second
lens group is moved along the optical axis so as to adjust the
diopter:0.5<.vertline.f2n.v- ertline./f1<1 (4)where f2n
indicates a focal length of said negative lens group in said second
lens group, and f1 indicates a focal length of said first lens
group.
10. An eyepiece lens for observing an image of an object through an
erect system, comprising a first lens group having a positive
refracting power, a second lens group having a negative refracting
power, and a third lens group having a positive refracting power,
wherein at least one lens group out of said lens groups having the
positive refracting power satisfies the following
condition:Dp/fe>0.1 (7)where Dp indicates a thickness of said
lens group having the positive refracting power, and fe indicates a
focal length of said eyepiece lens optical system at the diopter of
-1.
11. An eyepiece lens according to claim 10, further satisfying the
following condition:Dt/fe>0.2 (8)where Dt indicates a total
thickness of said eyepiece lens.
12. An eyepiece lens according to claim 11, wherein said lens group
having the positive refracting power has a positive meniscus lens
with a convex surface facing the object side.
13. An eyepiece lens according to claim 12, wherein said positive
meniscus lens satisfies the following condition:1.3<SF<2
(9)where SF indicates a shape factor of said positive meniscus
lens, which is defined by the following
formula:SF=(R2+R1)/(R2-R1),where R1 and R2 respectively indicate a
radiuses of curvature of said positive meniscus lens in the order
from the object side.
14. An eyepiece lens according to claim 10, wherein said lens group
having the positive refracting power has a positive meniscus lens
with a convex surface facing the object side.
15. An eyepiece lens according to claim 14, wherein said positive
meniscus lens satisfies the following condition:1.3<SF<2
(9)where SF indicates a shape factor of said positive meniscus
lens, which is defined by the following
formula:SF=(R2+R1)/(R2-R1),where R1 and R2 respectively indicate
the radiuses of curvature of said positive meniscus lens in the
order from the object side.
Description
[0001] This application claims the benefit of Japanese Patent
applications Nos. 2000-269193, 2000-270687 and 2001-252345 which
are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an eyepiece lens and, more
particularly, to an eyepiece lens most suitably for the use in a
camera, etc.
[0004] 2. Related Background Art
[0005] In an eyepiece lens for observing an image formed by an
objective lens through an erect system, it is necessary to enlarge
the erect system in order to obtain a higher magnification since a
light beam spreads. Then, since the length of an optical path for
the light beam is prolonged, the focal length of the eyepiece lens
has to be increased in proportion thereto. As a result, it is
impossible to achieve a higher magnification. Particularly, an
eyepiece lens having a long eye relief (the distance from the
eyepiece lens to the eyepoint) has this tendency conspicuously.
[0006] Moreover, as an eyepiece lens for an observing optical
system of a camera, or the like, there is known a lens which is
comprised of three groups including a positive lens group, a
negative lens group and another positive lens group, so as to move
an arbitrary lens group along the optical to correct the diopter.
As such an eyepiece lens, various lenses have been proposed
including one which is disclosed in Japanese Patent
Post-Examination Publication No. 61-19968.
[0007] With the recent electronization of cameras, etc., various
display devices such as an image pick-up device or a monitor are
increasingly mounted on a camera body As a result, the camera body
has to be enlarged, and an optical finder is required to have a
greater distance between the focal surface and the eyepoint
correspondingly, compared with conventional ones. Also, an image
formation area on an image pick-up device is made smaller than one
frame of a conventional silver halide film, so that a finder
magnification is also required to be greater. Further, the eyepiece
lens is required to additionally have a diopter correcting
function, and the like, in order to cope with the visual acuity of
any photographer.
SUMMARY OF THE INVENTION
[0008] The present invention has been contrived taking the above
inconveniences into consideration, and an object of the invention
is to provide an eyepiece lens having an excellent aberration
performance with a sufficient eye relief length and high
magnification, and preferably, an eyepiece lens further having a
diopter adjusting function.
[0009] In order to solve the above problems, there is provided an
eyepiece lens for observing an image formed by an objective lens
through an erect system, at least comprising a first lens group
having a positive refracting power and a second lens group having a
negative refracting power in the order from the side of an
observer, and satisfying the following condition:
-3<SF1<-1 (1)
[0010] where SF1 indicates a shape factor of the first lens group,
and SF indicates a shape factor of the lens group, which is defined
by:
SF=(Rs+RE)/(Rs-RE),
[0011] where Rs indicates the radius of curvature of a lens surface
closest to the object side and RE indicates the radius of curvature
of a lens surface closest to the observer side.
[0012] According to the present invention, with the above
structure, it is possible to move the principal point of the entire
eyepiece lens to the observer side, and to prevent a prolongation
of the focal length of the eyepiece lens which may be caused by the
prolongation of the optical path length of the erect system,
thereby raising the magnification. It is also possible to secure a
sufficient eye relief length since this eyepiece lens has a
retro-focus type layout which has positive and negative refracting
powers when seen from the object side toward the observer side.
[0013] Also according to the present invention, it is preferable to
satisfy the following condition:
-3<SF1<-1 (1)
[0014] Above the upper limit of the condition (1), the lens is not
preferable for improving the finder magnification. On the contrary,
below the lower limit of the condition (1), it is difficult to
correct a distortion and a coma. This case is not preferable also
in terms of manufacturing since a fluctuation in aberration becomes
great due to an error such as eccentricity. Accordingly, it is
practically desirable to satisfy the condition (1) that
-3<SF1<-1.
[0015] In this case, the layout of the second lens group and the
first lens group is of a retro-focal type having the negative and
positive refracting powers when seen from the object side to the
observer side, so that a sufficient length for the eye relief can
be secured.
[0016] According to the present invention, it is preferable to
adjust the diopter by moving the first lens group having the
positive refracting power or a lens component having a positive
refracting power in the first lens group, along the optical axis.
In this manner, it is possible to adjust the diopter while
maintaining a corrected aberration state, and particularly,
excellent distortion. It is also possible to adjust the diopter by
moving a lens component having a negative refracting power in the
second lens group along the optical axis. In this case, a lens
closer to the focal surface has a greater fluctuation in aberration
when the diopter is changed. As a result, it is preferable to
adjust the diopter by moving a lens component which is positioned
on the observer side, in the second lens group.
[0017] Also, according to the present invention, it is preferable
to satisfy, in addition to the above condition (1), the following
condition (2):
1<SF2<6 (2)
[0018] where SF2 indicates the shape factor of the second lens
group.
[0019] If the condition (2) is satisfied and the second lens group
is formed in a meniscus shape concave on the observer side, an
excellent aberration state can be securely obtained. Also, since
the principal point of the entire eyepiece lens is moved to the
image formation surface side, a high magnification can be achieved.
Below the lower limit of the condition (2), an astigmatism or a
coma which is generated in the first lens group satisfying the
condition (1) can not be sufficiently corrected. On the contrary,
above the upper limit of the condition (2), it is difficult to
correct a distortion. As a result, it is preferable to satisfy the
condition (2) that 1<SF2<6.
[0020] Further, according to the present invention, in addition to
satisfy the condition (1), it is preferable to constitute the
second lens group having the negative refracting power with a lens
group having a negative refracting power and a lens group having a
positive refracting power in this order from the observer side.
Then, it is possible to conduct excellent aberration correction
while maintaining a wide distance between the lens group having the
positive refracting power and the lens group having the negative
refracting power in the second lens group. It is also possible to
maintain a long distance from the focal surface to the eyepoint to
cope with enlargement of a camera size while aiming cost reduction
of the glass material.
[0021] It is also preferable to satisfy the following condition
(3):
-2<SF2p<-1 (3)
[0022] where SF2p indicates the shape factor of the positive lens
in the second lens group. When the positive lens group in the
second lens group is formed into a meniscus form which is concave
on the observer side, the principal point of the entire eyepiece
lens is moved to the imaging surface side. By the use of this
phenomenon, the focal length of the entire eyepiece lens can be
reduced to thereby raise the magnification. Above the upper limit
of the condition (3), it is difficult to improve the finder
magnification. On the contrary, below the lower limit of the
condition (3), it is difficult to correct a distortion and a coma.
Accordingly, it is preferable to satisfy the condition (3) that
-2<SF2p<-1.
[0023] Also, according to the present invention, it is preferable
to satisfy the following condition (5):
Dx/fe.gtoreq.0.08 (5)
[0024] where Dx indicates the thickness of a lens group, and fe
indicates the focal length of the eyepiece lens when the dopier is
-1, respectively.
[0025] If the condition (5) is satisfied, an excellent aberration
state can be obtained. Below the lower limit of the condition (5),
a coma can not be sufficiently corrected.
[0026] The unit of diopter is expressed in "dpt" in the following
description. The diopter X [dpt] indicates a state in which an
image obtained by the eyepiece lens can be formed at a position of
1/X [m] on the optical axis from the eyepoint (the sign is negative
when the image is formed closer to the object than the
eyepoint).
[0027] By satisfying such condition, it is possible to increase the
distance between the erect system and the eyepoint by making at
least one of the lens groups to be thicker to prolong the optical
path length while enhancing the magnification.
[0028] Particularly, as to the first lens group having the positive
refracting power, if the concave surface on the observer side is
moved backward to make the lens group thicker, the distance between
the erect system and the eyepoint can be wider. In addition, the
convex surface on the image formation surface side which has a
strong refracting power because of the meniscus shape satisfying
the condition (1) is not moved. For this reason, the focal length
of the first lens group can be effectively reduced while
maintaining an excellent aberration state. In the similar manner,
as to the lens group having the positive refracting power in the
second lens group satisfying the meniscus shape of the condition
(3), it is possible to increase the distance between the erect
system and eyepoint while maintaining the excellent aberration
state by making the lens group thicker by retreating the concave
surface on the observer side. In addition, as for the lens group
having the negative refracting power, if the lens group is made
thicker by moving forward the surface on the image formation
surface side, the concave surface on the observer side which has a
strong refracting power because of the shape satisfying the
condition (2) is not moved. As a result, it is possible to increase
the distance between the erect system and the eyepoint while
maintaining an excellent aberration state.
[0029] Further, it is desirable to constitute at least of the first
lens group satisfying the condition (1) and the second lens group
satisfying the condition (2) with a single cemented lens. In this
case, a longitudinal chromatic aberration and a chromatic
aberration of magnification can be easily corrected if the above
cemented lens is formed of glasses having different dispersions
which satisfy the following condition:
.vertline..nu.a-.nu.b.vertline.>8
[0030] where .nu.a and .nu.b respectively indicate the average
rates of dispersion of the glass materials for constituting the
cemented lens. It is also possible to reduce the processing cost of
a thick lens by constituting the cemented lens with lens components
of the same glass.
[0031] In addition, if the first lens group becomes thicker, it is
difficult to adjust the diopter by moving the first lens group
along the optical axis. Then, according to the present invention,
it is desirable to constitute the second lens group with a lens
group having a negative refracting power and a lens group having a
positive refracting power in this order from the observer side, and
to satisfy the following condition (4):
0.5<.vertline.f2n.vertline./f1<1 (4)
[0032] where f2n indicates the focal length of the negative lens
group in the second lens group, and f1 indicates the focal length
of the first lens group, respectively.
[0033] By satisfying the above condition to provide the negative
lens group in the second lens group with the strong refracting
power and to move this lens group along the optical axis, a diopter
adjusting function is additionally provided.
[0034] Above the upper limit of the condition (4), an amount of
movement of the negative lens group becomes great so that the
effect of adjusting the diopter by moving the negative lens in the
second lens group becomes poor. On the other hand, below the lower
limit of the condition (4), the refracting power of a lens which is
moved for adjusting the diopter becomes great, so that a
fluctuation in aberration due to a mechanical backlash becomes
unfavorably great. As a result, in order to adjust the diopter by
moving the negative lens in the second lens group, it is preferable
to satisfy the condition (4) that 0.5<.vertline.f2n.vertlin-
e./fe<1. More preferably, the upper limit of the condition (4)
should be set to 0.5 or around in order to reduce a Petzval
sum.
[0035] Furthermore, according to the present invention, it is
preferable to introduce a condenser lens between the imaging
surface and the erect system and to satisfy the following condition
(6):
1<fc/fe<3 (6)
[0036] where fc indicates the focal length of the condenser lens,
and fe indicates the focal length of the entire eyepiece lens at -1
dpt, respectively.
[0037] In this manner, it is possible to enhance the magnification
of the entire eyepiece lens by using the refracting power of the
condenser lens itself while, at the same time, correcting the
distortion. Above the upper limit of the condition (6), there
arises little effect for enhancing the magnification of the entire
eyepiece lens. On the contrary, below the lower limit of the
condition (6), it becomes difficult to correct the distortion.
[0038] Also, according to the present invention, there is provided
an eyepiece lens in an eyepiece lens optical system for observing
an image of an object through an erect system which comprises a
first lens group having a positive refracting power, a second lens
group having a negative refracting power, and a third lens group
having a positive refracting power in this order from the object
side, and which is characterized in that at least one lens group
out of the above lens groups having the positive refracting power
satisfies the following condition:
Dp/fe>0.1 (7)
[0039] where Dp indicates the thickness of the lens group having
the positive refracting power, and fe indicates the focal length of
the eyepiece lens when the diopter is 1 dpt.
[0040] According to the present invention, it is possible to obtain
the effect that an optical path length is prolonged by making at
least one of the above positive lens groups thick, so as to enhance
the finder magnification, thereby enlarging the distance between
the erect system and the eyepoint.
[0041] Below the lower limit of the condition (7), it is difficult
to obtain the above effect. However, if the lens is made to be too
thick, the weight or the cost of the cost is unfavorably increased.
Accordingly, it is practically preferable that the lens group is
within the condition of 0.3>Dp/fe>0.1. Particularly, when the
positive lens group is formed of a single lens, it is preferable
that the lens is practically within the condition of
0.2>Dp/fe>0.1. It is also preferable if all of the positive
lens groups for constituting the eyepiece lens satisfy the
condition of Dp/fe>0.1 since the effect of the present invention
can be exhibited more excellently.
[0042] Also according to the present invention, it is preferable to
satisfy the following condition (8):
Dt/fe>0.2 (8)
[0043] where the entire thickness of the eyepiece lens is indicated
by Dt on the condition that the above condition (7) is
satisfied.
[0044] It is possible to enlarge the distance between the erect
system and the eyepoint by satisfying the condition (8). Below the
lower limit of the condition (8), the total length of the erect
system is enlarged, so that it becomes difficult to enhance the
finder magnification. Also, since the eyepiece lens becomes
thinner, the distance between the erect system and the eyepoint can
not be enlarged, so that the object of the present invention can
not be achieved. More preferably, the condition of
0.6>Dt/fe>0.3 should be satisfied. Above this upper limit of
0.6, the erect system becomes thin so that it is difficult to
constitute the finder itself.
[0045] Also, according to the present invention, it is preferable
that the positive lens group which satisfies the above condition
(7) comprises a lens having a meniscus shape with the convex
surface directed to the object side. With such shape, the exit
pupil of the positive lens can be brought closer to the eyepoint As
a result, it is possible to see an image in an enlarged manner and
to enhance the finder magnification.
[0046] Also, according to the present invention, the positive
meniscus shape preferably satisfies the following condition:
1.3<SF<2 (9)
[0047] where SF indicates the same shape factor as that described
above.
[0048] By satisfying the condition (9), it is possible to easily
correct a coma and an astigmatism, so that an excellent aberration
state can be securely obtained while maintaining high finder
magnification. Above the upper limit of the condition (9), the exit
pupil approaches closer to the eyepoint, which is preferable for
enhancing the finder magnification. However, in this case, a
fluctuation of a coma or distortion which is caused by the diopter
adjustment can not be correct. On the contrary, below the lower
limit of the condition (9), a chance of occurring an aberration due
to the diopter adjustment is reduced. However, the exit pupil is
distant from the eyepoint and it becomes difficult to enhance the
finder magnification.
[0049] When all of the positive lens groups for constituting the
eyepiece lens satisfy the conditions (7) and (9), the effect of the
present invention is preferably enhanced. It is needless to say
that the effect of the present invention can be obtained also when
the conditions (7), (8) and (9) are simultaneously satisfied.
[0050] Then, it is also preferable to introduce an aspherical
surface into an eyepiece lens according to the present invention.
Particularly, a distortion can be improved when the aspherical
surface is introduced into the positive lens group, while a
fluctuation in coma in the range of diopter change can be easily
reduced when the aspherical surface is introduced into the negative
lens group. Further, it is effective to employ resin material for
the eyepiece lens according to the present invention. When a resin
material is employed, the aspherical surface can be introduced more
easily because of the lower cost thereof, whereby enabling a mass
production of the eyepiece lens.
[0051] Moreover, it is preferable to constitute a positive lens for
satisfying the condition (7) with a cemented lens. If glasses
having different rates of dispersion are used to constitute the
cemented lens, it becomes easier to correct a longitudinal
chromatic aberration and a chromatic aberration of the
magnification. It is also possible to reduce the processing cost by
constituting the cemented lens with a single glass.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] FIG. 1 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a first
embodiment of the present invention;
[0053] FIGS. 2A through 2D are views for showing aberrations in the
first embodiment;
[0054] FIG. 3 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a second
embodiment of the present invention;
[0055] FIGS. 4A through 4D are views for showing aberrations in the
second embodiment;
[0056] FIG. 5 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a third
embodiment of the present invention;
[0057] FIGS. 6A through 6L are views for showing aberrations when
the diopter in the third embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0058] FIG. 7 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a fourth
embodiment of the present invention;
[0059] FIGS. 8A through 8L are views for showing aberrations when
the diopter in the fourth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0060] FIG. 9 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a fifth
embodiment of the present invention;
[0061] FIGS. 10A through 10L are views for showing aberrations when
the diopter in the fifth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0062] FIG. 11 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a sixth
embodiment of the present invention;
[0063] FIGS. 12A through 12L are views for showing aberrations when
the diopter in the sixth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0064] FIG. 13 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a
seventh embodiment of the present invention;
[0065] FIGS. 14A through 14L are views for showing aberrations when
the diopter in the seventh embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0066] FIG. 15 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to an
eighth embodiment of the present invention;
[0067] FIGS. 16A through 16L are views for showing aberrations when
the diopter in the eighth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0068] FIG. 17 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a ninth
embodiment of the present invention;
[0069] FIGS. 18A through 18L are views for showing aberrations when
the diopter in the ninth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0070] FIG. 19 is a view for showing a lens configuration of a
finder optical system having an eyepiece lens according to a tenth
embodiment of the present invention;
[0071] FIGS. 20A through 20L are views for showing aberrations when
the diopter in the tenth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively;
[0072] FIGS. 21A through 21L are views for showing aberrations when
the diopter in the eleventh embodiment is on the most negative
side, when the diopter is -1 dpt, and when the diopter is on the
most positive side, respectively; and
[0073] FIGS. 22A through 22L are views for showing aberrations when
the diopter in the twelfth embodiment is on the most negative side,
when the diopter is -1 dpt, and when the diopter is on the most
positive side, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0074] Preferred embodiments of the present invention will be
described below with reference to the attached drawings.
[0075] (First Embodiment)
[0076] FIG. 1 is a cross-sectional view of a finder optical system
which has an eyepiece lens according to a first embodiment of the
present invention and a fixed diopter of -1 dpt. The finder optical
system is comprised of a focal surface 1, a block part 2 in which
an erect system is developed, a second lens group 3, a first lens
group 4 and a protective plate 5 in the order form the object side.
The position E.P is the eyepoint. In the present embodiment, the
first lens group having a positive refracting power is formed in a
meniscus shape with a concave surface on the observer side, so that
an excellent aberration state can be maintained in spite of a high
magnification.
[0077] Table 1 shows the specifications in the first embodiment.
The surface numbers are given successively in the order from the
object side, and the index of refraction is for the line d
(.lambda.=587.56 nm). In all of the following embodiments, an
aspherical surface is expressed by the following numerical
formula:
X=(Y.sup.2/R)/[1+(1-K.multidot.Y.sup.2/R.sup.2).sup.1/2]+C2.multidot.Y.sup-
.2+C3.multidot.Y.sup.3+C4.multidot.Y.sup.4+ . . . ,
[0078] where the height of the aspherical surface in a direction
perpendicular to the optical axis is Y, the distance along the
optical axis from a tangential surface at the vertex of the
aspherical surface to the position on the aspherical surface at the
height Y (sag amount) is X, the radius of curvature of the vertex
is R, a conic coefficient is K, and the aspherical coefficient of
the n-th order is Cn, respectively.
[0079] In the lens data, the aspherical surface has the mark * on
the left shoulder thereof.
[0080] Though the focal length, the radius of curvature, the
distance, and the other data on the length in the specifications
are generally expressed in "mm", the unit of the data is not
limited to this since the optical system can provide the same
optical performance even if it is proportionally enlarged or
reduced.
1TABLE 1 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 92.797 1.51680 64.10 (Flat surface) 5
.infin. 0.1 1.0 (Flat surface) 6 99.428 1.0 1.80518 25.35 7 25.600
1.9 1.0 8 26.440 4.2 1.80411 46.55 9 800.000 7.9 1.0 10 .infin. 1.0
1.52216 58.80 (Flat surface) 11 .infin. 20.8 1.0 (Flat surface) E.
P fe = 74.4 (Values corresponding to the conditions) (1) SF1 =
-1.068 (2) SF2 = +1.694
[0081] FIGS. 2A through 2D are views for showing the aberrations in
the present embodiment (including spherical aberration,
astigmatism, coma and distortion in the order from the left). In
these views of the aberrations, Y1 indicates the incident height of
a light beam on the erect system, and Y0 the height of the object
on the focal surface, respectively. The unit "D." along the
horizontal axis for the spherical aberration and the astigmatism
indicates the diopter (dpt), and "min" for the coma indicates a
minute of the angular unit. C, F, and D in the views indicate the
aberration curves on the line C (.lambda.=656.28 nm), the line F
(.lambda.=486.13 nm), and the line d (.lambda.=587.56 nm),
respectively. In the following description, the same referential
symbols as those in the present embodiment are used in the
aberration views for all of the embodiments. As clearly seen from
the aberration views, the aberrations are excellently
corrected.
[0082] (Second Embodiment)
[0083] FIG. 3 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a second
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a second lens
group 3, a first lens group 4 and a protective plate 5 in the order
form the object side. The position E.P is the eyepoint. In the
present embodiment, the form of the first lens group is changed
more than that in the first embodiment, so as to achieve a high
magnification while maintaining an excellent aberration state.
[0084] Table 2 shows the specifications in the second
embodiment.
2TABLE 2 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 92.797 1.51680 64.10 (Flat surface) 5
.infin. 0.1 1.0 (Flat surface) 6 17.465 1.0 1.80518 25.35 7 11.918
3.4 1.0 8 13.739 4.7 1.80411 46.55 9 27.675 6.8 1.0 10 .infin. 1.0
1.52216 58.80 (Flat surface) 11 .infin. 20.8 1.0 (Flat surface) E.
P fe = 71.0 (Values corresponding to the conditions) (1) SF1 =
-2.972 (2) SF2 = +5.297
[0085] FIGS. 4A through 4D are views for showing the aberrations in
the present embodiment. As clearly seen from the views, the
aberrations are excellently corrected.
[0086] (Third Embodiment)
[0087] FIG. 5 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a third
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a second lens
group 3, a first lens group 4 and a protective plate 5 in the order
form the object side. The position E.P is the eyepoint. In the
present embodiment, by moving the first lens group along the
optical axis, the focal length of the whole eyepiece lens is
changed to additionally obtain a diopter adjusting function.
[0088] Table 3 shows the specifications in the third
embodiment.
3TABLE 3 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 92.797 1.51680 64.10 (Flat surface) 5
.infin. 0.1 1.0 (Flat surface) 6 27.924 1.0 1.80518 25.35 7 16.875
D1 1.0 8 18.224 3.9 1.80411 46.55 9 57.551 D2 1.0 10 .infin. 1.0
1.52216 58.80 (Flat surface) 11 .infin. D3 1.0 (Flat surface) E. P
(Variable distance data) Diopter -2.5 -1.0 +1.0 D1 1.0 2.5 4.5 D2
8.3 6.8 4.8 D3 20.7 20.8 20.8 fe 77.6 72.8 67.2 (Values
corresponding to the conditions) (1) SF1 = -1.927 (2) SF2 =
+4.055
[0089] FIGS. 6A through 6D, FIGS. 6E through 6H, and FIGS. 6I
through 6L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the views, the aberrations are excellently corrected.
[0090] (Fourth Embodiment)
[0091] FIG. 7 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a fourth
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a second lens
group 3, a first lens group 4 and a protective plate 5 in the order
form the side opposite to the observer side. Then, the second lens
group 3 is further comprised of a positive lens group 3p and a
negative lens group 3n. The position E.P is the eyepoint.
[0092] In the present embodiment, the second lens group 3 is
comprised of the lens group 3p having a positive refracting power
and the lens group 3n having a negative refracting power, and a
distance between the focal surface and the eyepoint is maintained
to be wide. Also, a resin material is used for forming the lens
group 3n having the negative refracting power in the second lens
group 3 and the surface thereof is formed to be aspherical, so as
to correct a coma. Further, by moving the first lens group 4 along
the optical axis, the focal length of the entire eyepiece lens is
changed to change the diopter.
[0093] Table 4 shows the specifications in the fourth
embodiment.
4TABLE 4 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 86.518 1.51680 64.10 (Flat surface) 5
.infin. 0.5 1.0 (Flat surface) 6 22.856 6.9 1.71300 53.93 7 800.000
6.5 1.0 8 -102.597 1.5 1.58300 29.90 *9 12.959 D1 1.0 10 21.022 3.5
1.71300 53.93 11 120.000 D2 1.0 12 .infin. 1.0 1.52216 58.80 (Flat
surface) 13 .infin. D3 1.0 (Flat surface) E. P (Aspherical data)
Surface number K C3 *9 1.0 -6.158 .times. 10.sup.-8 (Variable
distance data) Diopter -3.0 -1.0 +1.0 D1 2.5 5.0 7.5 D2 9.5 7.0 4.5
D3 17.5 19.9 22.2 fe 62.8 62.1 61.3 (Values corresponding to the
conditions) (1) SF1 = -1.425 (3) SF2p = -1.059 (5) Dx/fe =
0.240
[0094] FIGS. 8A through 8D, FIGS. 8E through 8H, and FIGS. 8I
through 8L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the views, the aberrations are excellently corrected.
[0095] (Fifth Embodiment)
[0096] FIG. 9 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a fifth
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a second lens
group 3, a first lens group 4 and a protective plate 5 in the order
form the object side. Then, the second lens group 3 is further
comprised of a positive lens group 3p and a negative lens group 3n.
The position E.P is the eyepoint.
[0097] In the present embodiment, the first lens group of the above
fourth embodiment is thickened to enhance the magnification. The
distance from the focal surface to the eyepoint is formed to be
wider while an excellent aberration state is maintained, thereby
aiming a higher magnification. Further, by moving the first lens
group 4 along the optical axis, the focal length of the entire
eyepiece lens is changed to change the diopter.
[0098] Table 5 shows the specifications in the fifth
embodiment.
5TABLE 5 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 86.518 1.51680 64.10 (Flat surface) 5
.infin. 0.5 1.0 (Flat surface) 6 22.856 6.9 1.71300 53.93 7 800.000
6.5 1.0 8 -81.979 1.5 1.58300 29.90 *9 13.400 D1 1.0 10 21.022 5.0
1.71300 53.93 11 120.000 D2 1.0 12 .infin. 1.0 1.52216 58.80 (Flat
surface) 13 .infin. D3 1.0 (Flat surface) E. P (Aspherical data)
Surface number K C3 *9 1.0 -5.500 .times. 10.sup.-8 (Variable
distance data) Diopter -3.0 -1.0 1.0 D1 2.5 5.0 7.4 D2 9.5 7.0 4.6
D3 18.0 20.0 21.9 fe 62.5 61.7 61.0 (Values corresponding to the
conditions) (1) SF1 = -1.425 (3) SF2p = -1.059 (5) Dx/fe =
0.081
[0099] FIGS. 10A through 10D, FIGS. 10E through 10H, and FIGS. 10I
through 10L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the aberration views, the aberrations are excellently
corrected over a wide range of the diopter.
[0100] (Sixth Embodiment)
[0101] FIG. 11 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a sixth
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a second lens
group 3, a first lens group 4 and a protective plate 5 in the order
form the object side. Then, the second lens group 3 is further
comprised of a positive lens group 3p and a negative lens group 3n.
The position E.P is the eyepoint.
[0102] In the present embodiment, in order to make the first lens
thicker, the first lens is formed of a cemented lens. By moving the
negative lens in the second lens group, instead of the thickened
first lens, along the optical axis, the focal length of the entire
eyepiece lens is changed so as to additionally obtain a diopter
adjustment mechanism. Also, a resin material is used to form the
lens group having a positive refracting power in the second lens
group, and an aspherical surface is introduced as a surface
thereof, so as to change a distortion.
[0103] Table 6 shows the specifications in the sixth
embodiment.
6TABLE 6 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 86.518 1.51680 64.10 (Flat surface) 5
.infin. 0.5 1.0 (Flat surface) *6 17.632 6.0 1.49108 57.57 7 60.000
D1 1.0 8 68.000 1.0 1.80518 25.35 9 16.285 D2 1.0 10 21.600 6.1
1.79631 32.16 11 -32.099 7.5 1.72000 40.07 12 67.327 3.5 1.0 13
.infin. 1.0 1.52216 58.80 (Flat surface) 14 .infin. D3 1.0 (Flat
surface) E. P (Aspherical data) Surface number K C2 C4 *6 1.0
-8.000 .times. 10.sup.-5 -1.000 .times. 10.sup.-10 (Variable
distance data) Diopter -2.8 -1.0 +1.0 D1 4.9 3.3 1.2 D2 1.7 3.3 5.4
D3 18.2 20.0 20.1 fe 63.2 62.2 60.3 (Values corresponding to the
conditions) (1) SF1 = -1.945 (2) SF2p = -1.832 (4)
.vertline.f2n.vertline. f1 = 0.84 (5) Dx/fe = 0.22 .vertline..nu.10
- .nu.11.vertline. = 7.91
[0104] FIGS. 12A through 12D, FIGS. 12E through 12H, and FIGS. 12I
through 12L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the aberration views, the aberrations are excellently
corrected over a wide range of the diopter.
[0105] (Seventh Embodiment)
[0106] FIG. 13 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a seventh
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a second lens
group 3, a first lens group 4 and a protective plate 5 in the order
form the object side. The position E.P is the eyepoint.
[0107] In the present embodiment, the second lens group 3 having a
negative refracting power is comprised of a cemented lens, so as to
obtain a higher magnification while maintaining an excellent
aberration state. Also, by moving the first lens group 4 along the
optical axis, the focal length of the entire eyepiece lens is
changed to additionally obtain a diopter adjusting function.
[0108] Table 7 shows the specifications in the seventh
embodiment.
7TABLE 7 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 1.2 1.49108 57.57 (Flat surface) 3 .infin. 2.25
1.0 (Flat surface) 4 .infin. 86.518 1.51680 64.10 (Flat surface) 5
.infin. 0.5 1.0 (Flat surface) 6 21.136 7.1 1.71300 53.87 7 96.945
8.0 1.69895 30.13 8 13.330 D1 1.0 9 21.554 5.2 1.77250 49.60 10
83.401 D2 1.0 11 .infin. 1.0 1.52216 58.80 (Flat surface) 12
.infin. D3 1.0 (Flat surface) E. P (Variable distance data) Diopter
-2.7 -1.0 +1.0 D1 2.5 4.7 7.4 D2 9.5 7.3 4.6 D3 18.1 20.2 22.5 fe
61.4 60.7 59.8 (Values corresponding to the conditions) (1) SF1 =
-1.697 (2) SF2 = +4.415 (5) Dx/fe = 0.086 .vertline..nu.6 -
.nu.7.vertline. = 23.74
[0109] FIGS. 14A through 14D, FIGS. 14E through 14H, and FIGS. 14I
through 14L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the aberration views, the aberrations are excellently
corrected over a wide range of the diopter.
[0110] (Eighth Embodiment)
[0111] FIG. 15 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to an eighth
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
condenser lens C, a block part 2 in which an erect system is
developed, a second lens group 3, a first lens group 4 and a
protective plate 5 in the order form the object side. The position
E.P is the eyepoint.
[0112] In the present embodiment, a condenser lens is additionally
attached to the eyepiece lens of the third embodiment, so as to
achieve correction of a distortion and a high magnification. Also,
by moving the first lens group 4 along the optical axis, the focal
length of the entire eyepiece lens is changed to additionally
obtain a diopter adjusting function. The surface of the condenser
lens may be formed as the focal surface.
[0113] Table 8 shows the specifications in the eighth
embodiment.
8TABLE 8 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 3.2 1.49108 57.57 (Flat surface) 3 -103.000 0.75
1.0 4 .infin. 92.797 1.51680 64.10 (Flat surface) 5 .infin. 0.1 1.0
(Flat surface) 6 27.924 1.0 1.80518 25.35 7 16.875 D1 1.0 8 18.224
3.9 1.80411 46.55 9 57.551 D2 1.0 10 .infin. 1.0 1.52216 58.80
(Flat surface) 11 .infin. D3 1.0 (Flat surface) E. P (Variable
distance data) Diopter -2.5 -1.0 +1.0 D1 1.0 2.5 4.6 D2 8.3 6.8 4.7
D3 19.5 20.8 22.1 fe 72.0 70.2 67.7 (Values corresponding to the
conditions) (1) SF1 = -1.927 (2) SF2 = +4.055 (6) fc/fe = 2.99
[0114] FIGS. 16A through 16D, FIGS. 16E through 16H, and FIGS. 16I
through 16L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the aberration views, the aberrations are excellently
corrected over a wide range of the diopter.
[0115] (Ninth Embodiment)
[0116] FIG. 17 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a ninth
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
condenser lens C, a block part 2 in which an erect system is
developed, a second lens group 3, a first lens group 4 and a
protective plate 5 in the order form the object side. Then, the
second lens group 3 is further comprised of a positive lens group
3p and a negative lens group 3n. The position E.P is the
eyepoint.
[0117] In the present embodiment, a condenser lens is additionally
attached to the eyepiece lens of the fourth embodiment, so as to
achieve correction of a distortion and a high magnification. Also,
in the present embodiment, by moving the first lens group 4 along
the optical axis, the focal length of the entire eyepiece lens is
changed to additionally obtain the diopter adjusting function. The
surface of the condenser lens may be formed as the focal
surface.
[0118] Table 9 shows the specifications in the ninth
embodiment.
9TABLE 9 (Lens data) Surface Radius of Surface Index of Abbe Number
curvature distance refraction number 1 .infin. 0.25 1.0 (Focal
surface) 2 .infin. 3.7 1.49108 57.57 (Flat surface) 3 -39.000 0.25
1.0 4 .infin. 86.518 1.51680 64.10 (Flat surface) 5 .infin. 0.5 1.0
(Flat surface) 6 22.856 6.9 1.71300 53.93 7 800.000 6.5 1.0 8
-102.597 1.5 1.58300 29.90 *9 12.959 D1 1.0 10 21.022 3.5 1.71300
53.93 11 120.000 D2 1.0 12 .infin. 1.0 1.52216 58.80 (Flat surface)
13 .infin. D3 1.0 (Flat surface) E. P (Aspherical data) Surface
number K C3 *9 1.0 -6.158 .times. 10.sup.-8 (Variable distance
data) Diopter -3.0 -1.0 +1.0 D1 2.8 5.2 7.7 D2 9.2 6.8 4.2 D3 17.8
20.2 22.4 fe 53.2 57.1 62.0 (Values corresponding to the
conditions) (1) SF1 = -1.425 (2) SF2p = -1.059 (3) fc/fe = 1.39
[0119] FIGS. 18A through 18D, FIGS. 18E through 18H, and FIGS. 18I
through 18L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side. As clearly
seen from the aberration views, the aberrations are excellently
corrected over a wide range of the diopter.
[0120] (Tenth Embodiment)
[0121] FIG. 19 is a view for showing a cross section of a finder
optical system which has an eyepiece lens according to a tenth
embodiment of the present invention and a fixed diopter of -1 dpt.
The finder optical system is comprised of a focal surface 1, a
block part 2 in which an erect system is developed, a first lens
group 3, a second lens group 4 and a third lens group 5 in the
order form the object side. The position E.P is the eyepoint.
[0122] In the present embodiment, by moving the second lens group 4
along the optical axis, the focal length of the entire eyepiece
lens is changed to change the diopter.
[0123] Table 10 shows the specifications in the tenth
embodiment.
10TABLE 10 (Lens data) Surface Radius of Surface Index of Abbe
Number curvature distance refraction number 1 .infin. 3.3 1.0
(Focal surface) 2 .infin. 82.0 1.51680 64.10 (Flat surface) 3
.infin. 0.3 1.0 (Flat surface) 4 30.000 10.0 1.51680 64.10 5
200.000 D1 1.0 6 150.000 1.0 1.58300 29.90 7 20.000 D2 1.0 8 17.100
4.0 1.51680 64.10 9 82.650 D3 1.0 E. P (Variable distance data)
Diopter -3.0 -1.0 +1.0 (unit: dpt) D1 7.0 4.0 0.5 D2 1.0 4.0 7.5 D3
12.5 15.0 15.0 fe 69.4 67.6 64.7 (Values corresponding to the
conditions) (1) Dp1/fe = 0.147 (Dp1: the thickness of the first
lens group) (2) Dt/fe = 0.340 (3) SF1 = 1.352 (the first group
shape factor)
[0124] FIGS. 20A through 20D, FIGS. 20E through 20H, and FIGS. 20I
through 20L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side (spherical
aberration, astigmatism, coma and distortion, in this order from
the left). As clearly seen from the aberration views, the
aberrations are excellently corrected over a wide range of the
diopter.
[0125] (Eleventh Embodiment)
[0126] A lens configuration of an eyepiece lens according to an
eleventh embodiment of the present invention is substantially the
same as that of the foregoing tenth embodiment, so that description
thereof will be omitted. Table 11 shows the specifications in the
eleventh embodiment.
11TABLE 11 (Lens data) Surface Radius of Surface Index of Abbe
Number curvature distance refraction number 1 .infin. 3.3 1.0
(Focal surface) 2 .infin. 82.0 1.51680 64.10 (Flat surface) 3
.infin. 0.3 1.0 (Flat surface) 4 22.250 5.0 1.77278 49.45 5 61.000
D1 1.0 6 95.000 1.0 1.72825 28.34 7 14.821 D2 1.0 8 17.680 12.0
1.71300 53.92 9 70.730 D3 1.0 E.P (Variable distance data) Diopter
-3.0 -1.0 +2.0 (unit:dpt) D1 5.4 3.7 0.7 D2 1.6 3.3 6.3 D3 8.0 15.0
15.0 fe 59.0 58.4 55.8 (Values corresponding to the conditions) (1)
Dp3 fe = 0.205 (Dp3: the thickness of the third lens group) (2)
Dt/fe = 0.428 (3) SF3 = 1.666 (the third group shape factor)
[0127] FIGS. 21A through 21D, FIGS. 21E through 21H, and FIGS. 21I
through 21L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side (spherical
aberration, astigmatism, coma and distortion, in this order from
the left). As clearly seen from the aberration views, the
aberrations are excellently corrected over a wide range of the
diopter.
[0128] (Twelfth Embodiment)
[0129] A lens configuration of an eyepiece lens according to a
twelfth embodiment of the present invention is substantially the
same as that of the foregoing tenth embodiment, so that description
thereof will be omitted. Table 12 shows the specifications in the
twelfth embodiment.
12TABLE 12 (Lens data) Surface Radius of Surface Index of Abbe
Number curvature distance refraction number 1 .infin. 2.0 1.49108
57.57 (Focal surface) 2 .infin. 0.5 1.0 (Flat surface) 3 .infin.
4.7 1.56882 56.04 (Flat surface) 4 -65.000 1.8 1.0 5 .infin. 96.4
1.51680 64.10 (Flat surface) 6 .infin. 0.1 1.0 (Flat surface) 7
44.000 11.0 1.71300 53.92 8 138.600 D1 1.0 9 128.700 2.0 1.72825
28.34 10 24.538 D2 1.0 11 24.270 11.0 1.71300 53.92 12 121.372 D3
1.0 E.P (Variable distance data) Diopter -3.0 -1.0 +0.5 (unit:dpt)
D1 6.6 3.4 0.9 D2 0.4 3.6 6.1 D3 15.0 18.0 18.0 fe 83.5 79.1 75.5
(Values corresponding to the conditions) (1) Dp1/fe = 0.138 (Dp1:
the thickness of the first group lens) (1) Dp3/fe = 0.138 (Dp3: the
thickness of the third group lens) (2) Dt/fe = 0.391 (3) SF1 =
1.930 (the first group shape factor) (3) SF3 = 1.499 (the third
group shape factor)
[0130] FIGS. 22A through 22D, FIGS. 22E through 22H, and FIGS. 22I
through 22L are views for showing aberrations, respectively, when
the diopter is on the most negative side, when the diopter is -1
dpt, and when the diopter is on the most positive side (spherical
aberration, astigmatism, coma and distortion, in this order from
the left). As clearly seen from the aberration views, the
aberrations are excellently corrected over a wide range of the
diopter.
[0131] As described above, according to the present invention, it
is possible to provide an eyepiece lens having an excellent
aberration performance with a sufficiently long eye relief and high
magnification, and preferably an eyepiece lens further comprising
the diopter adjusting function.
* * * * *