U.S. patent application number 09/791771 was filed with the patent office on 2001-11-01 for zoom lens system.
This patent application is currently assigned to ASAHI KOGAKU KOGYO KABUSHIKI KAISHA. Invention is credited to Enomoto, Takashi.
Application Number | 20010036021 09/791771 |
Document ID | / |
Family ID | 18569841 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010036021 |
Kind Code |
A1 |
Enomoto, Takashi |
November 1, 2001 |
Zoom lens system
Abstract
A zoom lens system includes a positive first lens group and a
negative second lens group. In a short-focal-length side zooming,
the first and second lens groups are moved towards the object,
while the moveable sub-lens group is stationary at the object-side
end. At the intermediate switching focal length, the moveable
sub-lens group is moved to the image-side end, and the first and
second lens groups are moved towards the image plane. In a
long-focal-length side zooming range, the first and second lens
groups are moved towards the object, while the moveable sub-lens
group is stationary at the image-side end. Moreover, the zoom lens
system satisfies 0.3<logZi/logZ<0.8 . . . (1); wherein
Zi=fm/fw; Z=ft/fw; fw designates the focal length at the short
focal length extremity; ft designates the focal length at the long
focal length extremity; and fin designates the intermediate
switching focal length.
Inventors: |
Enomoto, Takashi; (Chiba,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
ASAHI KOGAKU KOGYO KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
18569841 |
Appl. No.: |
09/791771 |
Filed: |
February 26, 2001 |
Current U.S.
Class: |
359/692 ;
359/691 |
Current CPC
Class: |
G02B 15/177
20130101 |
Class at
Publication: |
359/692 ;
359/691 |
International
Class: |
G02B 015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2000 |
JP |
2000-47619 |
Claims
What is claimed is:
1. A zoom lens system comprising a positive first lens group and a
negative second lens group, in this order from an object, wherein
one of said first lens group and said second lens group comprises a
switching lens group, and said switching lens group comprises more
than two sub-lens groups; wherein one sub-lens group is made
moveable, with respect to other sub-lens groups, to either the
object-side end or the image-side end; wherein in a
short-focal-length side zooming range from the short focal length
extremity to an intermediate switching focal length, said first
lens group and said second lens group are moved towards said
object, and the distance therebetween is varied, while said
moveable sub-lens group in said switching lens group is being made
stationary at the object-side end; wherein at said intermediate
switching focal length, said moveable sub-lens group is moved to
the image-side end, and said first lens group and said second lens
group are moved towards the image plane; wherein in a
long-focal-length side zooming range from said intermediate
switching focal length to the long focal length extremity, said
first lens group and said second lens group are moved towards said
object, and the distance therebetween is varied, while said
moveable sub-lens group in said switching lens group is being made
stationary at the image-side end; and wherein said zoom lens system
satisfies the following condition: 0.3<logZi/logZ<0.8 wherein
Zi=fm/fw; Z=ft/fw; fw designates the focal length at the short
focal length extremity; ft designates the focal length at the long
focal length extremity; and fm designates said intermediate
switching focal length.
2. The zoom lens system according to claim 1, wherein said first
lens group comprises said switching lens group, and said first lens
group comprises a negative first sub-lens group and a positive
second sub-lens group, in this order from said object.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a zoom lens system for a
compact camera.
[0003] 2. Description of the Related Art
[0004] In a zoom lens system, a requirement for a high zoom ratio
and a requirement for miniaturization are not compatible. For
example, in a zoom lens system of two-lens-group arrangement which
can be miniaturized, if lens-group moving paths are designed, i.e.
a solution of the lens-group moving path is obtained, with the aim
of obtaining a high zoom ratio, lens groups come into contact with
each other at the long focal length extremity, or lens groups and
the image plane cause interference therebetween at the short focal
length extremity. On the other hand, in the case of a zoom lens
system of three-lens-group arrangement, the zoom ratio can be made
higher than that of a two-lens-group zoom lens system; however,
miniaturization of the zoom lens system is difficult. Furthermore,
if the optical power (hereinafter, power) of each lens group is
determined to obtain an even higher zoom ratio, error sensitivity
of each lens group becomes too high, so that a mechanism which can
maintain necessary precision on the operations of the lens system
under such a high sensitivity is not practical to be obtained.
[0005] More concretely, in a two-lens-group zoom lens system, if a
zoom ratio is 3.5 or more, the entire zoom lens system has to be
made larger since the distance between the lens groups has to be
increased. Furthermore, in a two-lens-group zoom lens system, since
there are limitations in adequately balancing aberrations at a
focal length point in the range defined by the short focal length
extremity to the long focal length extremity, a three-lens-group
zoom lens system has to be employed. However, a three-lens-group
zoom lens system of the prior art is not suitable for achieving a
miniaturized zoom lens system, since the overall length thereof and
the diameter of the front lens group are large compared with those
a two-lens-group zoom lens system.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
two-lens-group zoom lens system for a compact camera, which has a
high zoom ratio, while the overall length and the lens diameters of
the zoom lens system are miniaturized.
[0007] In order to achieve the above-mentioned object, there is
provided a zoom lens system including a positive first lens group
and a negative second lens group, in this order from the object.
One of the first lens group and the second lens group constitutes a
switching lens group. The switching lens group includes more than
two sub-lens groups, and one sub-lens group is made moveable, with
respect to other sub-lens groups, to either the object-side end or
the image-side end.
[0008] In a short-focal-length side zooming range from the short
focal length extremity to an intermediate switching focal length,
the first lens group and the second lens group are moved towards
the object and the distance therebetween is varied, while the
moveable sub-lens group in the switching lens group is being made
stationary at the object-side end.
[0009] At the intermediate switching focal length, the moveable
sub-lens group is moved to the image-side end, and the first lens
group and the second lens group are moved towards the image
plane.
[0010] In a long-focal-length side zooming range from the
intermediate switching focal length to the long focal length
extremity, the first lens group and the second lens group are moved
towards the object, and the distance therebetween is varied, while
the moveable sub-lens group in the switching lens group is being
made stationary at the image-side end.
[0011] Furthermore, the zoom lens system preferably satisfies the
following condition:
0.3<logZi/logZ<0.8 (1)
[0012] wherein
[0013] Zi=fm/fw;
[0014] Z=ft/fw;
[0015] fw designates the focal length at the short focal length
extremity;
[0016] ft designates the focal length at the long focal length
extremity; and
[0017] fm designates the intermediate switching focal length.
[0018] In the case where the first lens group constitutes the
switching lens group, the first zoom lens group can include a
negative first sub-lens group and a positive second sub-lens group,
in this order from the object.
[0019] The present disclosure relates to subject matter contained
in Japanese Patent Application No. 2000-047619 (filed on Feb. 24,
2000) which is expressly incorporated herein by reference in its
entirety.
[0020] Copending and commonly assigned U.S. patent application to
"A Zoom Lens System", listing as an inventor Takashi ENOMOTO, filed
concurrently with the present application, having Attorney docket
No. P20648; and Japanese Patent Application No. 2001-015741 (filed
on Jan. 24, 2001), from which the application designated by
Attorney docket No. P20648 claims priority, are expressly
incorporated herein by reference in their entireties.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will be discussed below in detail with
reference to the accompanying drawings, in which:
[0022] FIG. 1 is a lens arrangement of the zoom lens system at the
short focal length extremity, according to first through fourth
embodiments of the present invention;
[0023] FIGS. 2A, 2B, 2C and 2D show aberrations of the lens
arrangement shown in FIG. 1;
[0024] FIG. 3 is a lens arrangement of the zoom lens system at the
long focal length extremity, according to the first through fourth
embodiments of the present invention;
[0025] FIGS. 4A, 4B, 4C and 4D show aberrations of the lens
arrangement shown in FIG. 3;
[0026] FIG. 5 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the first embodiment is made
stationary at the object-side end;
[0027] FIGS. 6A, 6B, 6C and 6D show aberrations of the lens
arrangement shown in FIG. 5;
[0028] FIG. 7 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the first embodiment is made
stationary at the image-plane side end;
[0029] FIGS. 8A, 8B, 8C and 8D show aberrations of the lens
arrangement shown in FIG. 7;
[0030] FIG. 9 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the second embodiment is made
stationary at the object-side end;
[0031] FIGS. 10A, 10B, 10C and 10D show aberrations of the lens
arrangement shown in FIG. 9;
[0032] FIG. 11 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the second embodiment is made
stationary at the image-plane side end;
[0033] FIGS. 12A, 12B, 12C and 12D show aberrations of the lens
arrangement shown in FIG. 11;
[0034] FIG. 13 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the third embodiment is made
stationary at the object-side end;
[0035] FIGS. 14A, 14B, 14C and 14D show aberrations of the lens
arrangement shown in FIG. 13;
[0036] FIG. 15 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the third embodiment is made
stationary at the image-plane side end;
[0037] FIGS. 16A, 16B, 16C and 16D show aberrations of the lens
arrangement shown in FIG. 15;
[0038] FIG. 17 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the fourth embodiment is made
stationary at the object-side end;
[0039] FIGS. 18A, 18B, 18C and 18D show aberrations of the lens
arrangement shown in FIG. 17;
[0040] FIG. 19 is a lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group of the fourth embodiment is made
stationary at the image-plane side end;
[0041] FIGS. 20A, 20B, 20C and 20D show aberrations of the lens
arrangement shown in FIG. 19;
[0042] FIG. 21 shows lens-group moving paths for zooming in the
zoom lens system according to the present invention;
[0043] FIG. 22 shows another example lens-group moving paths for
zooming in the zoom lens system according to the present invention;
and
[0044] FIG. 23 shows still another example lens-group moving paths
for zooming in the zoom lens system according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] As shown in the lens-group moving paths of FIG. 21, the zoom
lens system includes a positive first lens group 10, and a negative
second lens group 20, in this order from the object. The first lens
group (switching lens group) 10 includes a first sub-lens group 10a
and a second sub-lens group 10b, in this order from the object.
Upon zooming from the short focal length extremity fw toward the
long focal length extremity ft, the first lens group 10 and the
second zoom lens group 20 are arranged to move as follows:
[0046] In a short-focal-length side zooming range Zw from the short
focal length extremity fw to the intermediate switching focal
length fm, the first lens group 10 and the second lens group 20 are
moved toward the object, while the distance therebetween is
varied.
[0047] At the intermediate switching focal length fm, the first
lens group 10 and the second lens group 20 are moved towards the
image plane by a predetermined distance.
[0048] In a long-focal-length side zooming range Zt from the
intermediate switching focal length to the long focal length
extremity, the first lens group and the second lens group are moved
towards the object, while the distance therebetween is varied.
Furthermore, the first sub-lens group (moveable sub-lens group) 10a
can be alternatively moveable, with respect to the second sub-lens
group, to either the object-side end or the image-plane side end.
In the short-focal-length side zooming range Zw, the first sub-lens
group 10a is made stationary at the object-side end; at the
intermediate switching focal length fm, the first sub-lens group
10a is moved to the image-plane side end; and in the
long-focal-length side zooming range Zt, the first sub-lens group
10a is made stationary at the image-plane side end. The aperture
stop S moves together with the second sub-lens group 10b during
zooming.
[0049] The lens-group-moving paths shown in FIG. 21 are simply
depicted as straight lines. It should however be noted that actual
lens-group-moving paths are not necessarily straight lines.
Furthermore, focusing is performed by integrally moving the first
sub-lens group 10a and the second sub-lens group 10b, i.e., the
first lens group 10 regardless of the zooming ranges.
[0050] The lens-group-moving paths have discontinuities at the
intermediate switching focal length fm; however, by adequately
determining the positions of the first sub-lens group 10a, the
second sub-lens group 10b and the second lens group 20 respectively
at the short focal length extremity fw, the intermediate switching
focal length fin and the long focal length extremity ft, solutions
by which an image is correctly formed on a predetermined plane can
be obtained. According to the lens-group-moving paths with these
solutions, a zoom lens system which is miniaturized and has a high
zoom ratio can be obtained.
[0051] The existence of solutions for the lens-group-moving paths
of the first embodiment can be explained, for example, by the
following discussions:
[0052] The zoom lens system of the first embodiment can be divided
into a negative lens group, a positive lens group, and a negative
lens group, in this order from the object. Here, the negative and
the positive lens groups on the object side (i.e., the first
sub-lens group 10a and the second sub-lens group 10b) are
considered to be a positive front lens group (the first lens group
10) in which the relative position of the negative and positive
lens groups is fixed respectively at the long focal length
extremity ft and at the short focal length extremity fw. Since the
distance between the first sub-lens group 10a and the second
sub-lens group 10b is longer at the short focal length extremity fw
than at the long focal length extremity ft (d1>d2), the focal
length Pt of the first lens group 10 at the long focal length
extremity ft is longer than the focal length Pw thereof at the
short focal length extremity fw, i.e., Pt>Pw. In other words,
the first lens group 10 with the focal length Pt and the second
lens group 20 can be considered to be a two-lens-group zoom lens
system, and the first lens group 10 with the focal length Pw and
the second lens group 20 can be considered to be another two-lens
group zoom lens system. Therefore solutions for each zoom lens
system can be obtained. More concretely, one of the two solutions
is the lens-group-moving paths in the short-focal-length side
zooming range Zw, and the other solution is the lens-group-moving
paths in the long-focal-length side zooming range Zt. However, at
the intermediate switching focal length fm, these paths are
discontinued, and the distance between the negative and the
positive lens groups in the front lens group is not the same. It
should be understood that though the movement of the lens groups
upon zooming is substantially the same as that of a two-lens-group
zoom lens system, a miniaturized zoom lens system with a high zoom
ratio can be obtained by (i) providing the discontinuities along
the lens-group-moving paths for the first lens group 10 and the
second lens group 20 at the intermediate switching focal length fm,
and (ii) by varying the distance between the negative and the
positive lens groups in the first lens group 10. The above is
discussed for the first embodiment; however, the discussions are
also applicable for other embodiments.
[0053] It is noted that, because of the aforementioned
discontinuities and varying of distances, the switching lens groups
of the invention do not necessarily fit within the ordinary meaning
of an "N lens group" system (where N is a whole number).
[0054] For example, in the case of a lens having a switching lens
group and one "conventional" lens group, the present disclosure
characterizes, for the purposes of explanation, such a lens both
(i) as having three lens groups and (ii) as having a first zooming
lens group 10 (with first and second sub-lens groups 10a and 10b)
and a second zooming lens group 20. However, the use of the two
different characterizations does not mean that a "switching lens
group" according to the invention should be considered to be a
conventional "lens group". The use of two different
characterizations emphasizes that the switching lens groups
disclosed herein are different from ordinary "lens groups".
[0055] Accordingly, the claims and disclosure of the present
application should be interpreted to be consistent with the meaning
of "lens group"; "sub-lens group"; "switching lens group"; and
"zooming lens group" as set forth herein where such terms would be
inconsistent with the same terms as otherwise employed in the
art.
[0056] Condition (1) specifies the intermediate switching focal
length fin at which the sub-lens group of the switching lens group
is moved. By satisfying this condition, aberrations can be suitably
corrected in a range where a zoom ratio is high up to about
3.5.
[0057] If logZi/logZ exceeds the upper limit of condition (1),
optical performance of the zoom lens system from the short focal
length extremity fw to the intermediate focal length fin cannot be
obtained.
[0058] If logZi/logZ exceeds the lower limit of condition (1),
optical performance of the zoom lens system from the intermediate
switching focal length fin to the long focal length extremity
cannot be obtained.
[0059] It is practical to apply the above-described zoom lens
system to a photographing lens system of a camera in which the
photographing lens system and a finder optical system are
independently provided. Moreover, with respect to each lens group,
positions at which the lens group stops upon zooming are preferably
determined in a stepwise manner along the lens-group-moving path,
i.e., it is preferable to provide a plurality of focal-length
steps. FIGS. 22 and 23 show that positions for stopping each lens
group are determined in a stepwise manner along the
lens-group-moving paths. Since these lens systems shown in FIGS. 22
and 23 are the same as that of FIG. 21, the identical components
are provided with the same numerals. In FIG. 22, the
lens-group-moving paths are depicted with dotted lines; and
positions at which each lens group is to be stopped are indicated
with black dots along the dotted lines. Further, in FIG. 23, the
dots are connected by smooth curved lines. According to an actual
mechanical structure, each lens group can be moved along such
smooth curved lines.
[0060] Specific numerical data of the embodiments will be described
hereinafter. In the diagrams of chromatic aberration (axial
chromatic aberration) represented by spherical aberration, the
solid line and the two types of dotted lines respectively indicate
spherical aberrations with respect to the d, g and C lines. Also,
in the diagrams of lateral chromatic aberration, the two types of
dotted lines respectively indicate magnification with respect to
the g and C lines; however, the d line as the base line coincides
with the ordinate. S designates the sagittal image, and M
designates the meridional image. In the tables, Fno designates the
F-number, f designates the focal length of the entire zoom lens
system, m designates the transverse magnification, W designates the
half angle-of-view ( ), fB designates the back focal distance, r
designates the radius of curvature, d designates the lens-element
thickness or distance between lens elements, Nd designates the
refractive index at the d-line, and .nu. designates the Abbe
number.
[0061] In addition to the above, an aspherical surface which is
symmetrical with respect to the optical axis is defined as
follows:
x=cy.sup.2/(1+[1-{1+K}c.sup.2y.sup.2].sup.1/2)+A4y.sup.4+A6y.sup.6+A8y.sup-
.8+A10y.sup.10 . . .
[0062] wherein:
[0063] x designates a distance from a tangent plane of an
aspherical vertex;
[0064] c designates a curvature of the aspherical vertex (l/r)
[0065] y designates a distance from the optical axis;
[0066] K designates the conic coefficient; and
[0067] A4 designates a fourth-order aspherical coefficient;
[0068] A6 designates a sixth-order aspherical coefficient;
[0069] A8 designates a eighth-order aspherical coefficient; and
[0070] A10 designates a tenth-order aspherical coefficient.
[0071] In each of the first through fourth embodiments, the
different intermediate switching focal length fm is indicated.
Accordingly, the lens arrangement at the short focal length
extremity fw and the long focal length extremity ft are the same in
the first through fourth embodiments. FIGS. 1 and 3 show the lens
arrangements thereof, and FIGS. 2A through 2D, and 4A through 4D
show the aberrations thereof.
[0072] FIG. 1 is the lens arrangement of the zoom lens system at
the short focal length extremity, according to first through fourth
embodiments. FIGS. 2A through 2D show aberrations of the lens
arrangement shown in FIG. 1. FIG. 3 is the lens arrangement of the
zoom lens system at the long focal length extremity, according to
the first through fourth embodiments. FIGS. 4A through 4D show
aberrations of the lens arrangement shown in FIG. 3. Table 1 shows
numerical data of the first through fourth embodiments. Lens
surface Nos. 1 through 8 constitute the positive first lens group
(switching lens group) 10, lens surface Nos. 9 through 12
constitute the negative second lens group 20. The first lens group
10 includes the first sub-lens group 10a constituted by
negative-and-positive cemented lens elements; and a second sub-lens
group 10b constituted by positive-and-negative cemented lens
elements, and a positive lens element, in this order from the
object. The second lens group 20 includes a positive lens element
and a negative lens element, in this order from the object. The
aperture stop S is positioned at the distance of 1.0 millimeter
from the image-side of surface No. 8.
1TABLE 1 F.sub.NO = 1:5.2-12.0 f = 29.00-112.00 (zoom ratio: 3.86)
W = 36.7-10.9 f.sub.B = 8.45-76.08 Surface No. r d N.sub.d
.multidot. 1 -19.417 1.20 1.74330 49.3 2 48.529 1.90 1.65917 32.3
3* -97.703 3.05-0.25 -- -- 4 15.956 4.06 1.48749 70.2 5 -10.901
1.50 1.84204 32.3 6 -52.374 0.88 -- -- 7 52.891 2.83 1.73077 40.5
8* -18.318 11.39-3.01 -- -- 9* -50.943 2.69 1.58547 29.9 10 -21.717
4.55 -- -- 11 -10.024 1.40 1.80238 45.9 12 -87.799 -- -- --
*designates the aspherical surface which is rotationally
symmetrical with respect to the optical axis.
[0073] Aspherical surface data (the aspherical surface coefficients
not indicated are zero (0.00)):
2 Surf. No. K A4 A6 A8 3 0.00 0.3653 .times. 10.sup.-5 -0.1700
.times. 10.sup.-6 -- 8 0.00 0.6172 .times. 10.sup.-4 0.8952 .times.
10.sup.-8 0.8233 .times. 10.sup.-9 9 0.00 0.5891 .times. 10.sup.-4
-0.1232 .times. 10.sup.-6 0.6298 .times. 10.sup.-8
[0074] [Embodiment 1]
[0075] FIGS. 5 through 8 show the first embodiment in which the
intermediate switching focal length fin is 50.00 mm. FIG. 5 is the
lens arrangement of the zoom lens system at the intermediate
switching focal length fin under the condition that the moveable
sub-lens is made stationary at the object-side end. FIGS. 6A
through 6D show aberrations of the lens arrangement shown in FIG.
5. FIG. 7 is the lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group is made stationary at the image-plane
side end. FIGS. 8A through 8D show aberrations of the lens
arrangement shown in FIG. 7. Table 2 shows the numerical data of
the first embodiment.
3TABLE 21 fm(Zw) = 50.00 (F.sub.NO = 7.8; W = 23.6; f.sub.B =
28.75; D3 = 3.05; D8 = 5.56) fm(Zt) = 50.00 (F.sub.NO = 7.8; W =
22.6; f.sub.B = 23.12; D3 = 0.25; D8 = 8.04)
[0076] [Embodiment 2]
[0077] FIGS. 9 through 12 show the second embodiment in which t the
intermediate switching focal length fin is 60.00 mm. FIG. 9 is the
lens arrangement of the zoom lens system at the intermediate
switching focal length fin under the condition that the moveable
sub-lens is made stationary at the object-side end. FIGS. 10A
through 10D show aberrations of the lens arrangement shown in FIG.
9. FIG. 11 is the lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group is made stationary at the image-plane
side end. FIGS. 12A through 12D show aberrations of the lens
arrangement shown in FIG. 11. Table 3 shows the numerical data of
the second embodiment.
4TABLE 3 fm(Zw) = 60.00 (F.sub.NO = 8.8; W = 20.0; f.sub.B = 38.42;
D3 = 3.05; D8 = 4.22) fm(Zt) = 60.00 (F.sub.NO = 8.8; W = 19.4;
f.sub.B = 31.66; D3 = 0.25; D8 = 6.53)
[0078] [Embodiment 3]
[0079] FIGS. 13 through 16 show the third embodiment in which the
intermediate switching focal length fm is 70.00 mm. FIG. 13 is the
lens arrangement of the zoom lens system at the intermediate
switching focal length fin under the condition that the moveable
sub-lens is made stationary at the object-side end. FIGS. 14A
through 14D show aberrations of the lens arrangement shown in FIG.
13. FIG. 15 is the lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group is made stationary at the image-plane
side end. FIGS. 16A through 16D show aberrations of the lens
arrangement shown in FIG. 15. Table 4 shows the numerical data the
third embodiment.
5TABLE 41 fm(Zw) = 70.00 (F.sub.NO = 9.5; W = 17.3; f.sub.B =
48.08; D3 = 3.05; D8 = 3.27) fm(Zt) = 70.00 (F.sub.NO = 9.5; W =
16.9; f.sub.B = 40.21; D3 = 0.25; D8 = 5.44)
[0080] [Embodiment 4]
[0081] FIGS. 17 through 20D show the fourth embodiment in which the
intermediate switching focal length is 80.00 mm. FIG. 17 is the
lens arrangement of the zoom lens system at the intermediate
switching focal length fin under the condition that the moveable
sub-lens group is made stationary at the object-side end. FIGS. 18A
through 18D show aberrations of the lens arrangement shown in FIG.
17. FIG. 19 is the lens arrangement of the zoom lens system at the
intermediate switching focal length fin under the condition that
the moveable sub-lens group is made stationary at the image-plane
side end. FIGS. 20A through 20D show aberrations of the lens
arrangement shown in FIG. 19. Table 5 shows the numerical data of
the fourth embodiment.
6TABLE 5 fm(Zw) = 80.00 (F.sub.NO = 9.8; W = 15.2; f.sub.B = 57.75;
D3 = 3.05; D8 = 2.55) fm(Zt) = 80.00 (F.sub.NO = 9.8; W = 15.0;
f.sub.B = 48.75; D3 = 0.25; D8 = 4.63)
[0082] Table 6 shows the numerical values of condition (1) of each
embodiment.
7 TABLE 6 Embod. 1 Embod. 2 Embod. 3 Embod. 4 Cond. (1) 0.40 0.54
0.65 0.75
[0083] As can be understood by Table 6, each embodiment satisfies
condition (1), and as can be understood from the drawings, various
aberrations at each focal length have been adequately
corrected.
[0084] In the first through fourth embodiments, the first lens
group constitutes the switching lens group; however, the second
lens group can alternatively be the switching lens group.
[0085] According to the above description, a two-lens-group zoom
lens system for a compact camera, which has a high zoom ratio, and
the miniaturized overall length and lens diameters, can be
obtained.
* * * * *