U.S. patent application number 09/745799 was filed with the patent office on 2001-09-20 for zoom lens system.
This patent application is currently assigned to ASAHI KOGAKU KOGYO KABUSHIKI KAISHA. Invention is credited to Enomoto, Takashi.
Application Number | 20010022697 09/745799 |
Document ID | / |
Family ID | 18498967 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022697 |
Kind Code |
A1 |
Enomoto, Takashi |
September 20, 2001 |
Zoom lens system
Abstract
A zoom lens system including a first through third lens groups.
The combined power of the first and second lens groups is positive.
Upon zooming from the short focal length extremity towards the long
focal length extremity, all the three lens groups are moved from
the image towards the object. The zoom lens system satisfies the
following conditions: 0.01<(d.sub.12W-d.sub.12T)/f.sub.W<0.1
(1); 3.5<f.sub.T/f.sub.12W<6.0 (2);
4.0<f.sub.T/.vertline.f.sub.3G.vertline.<8.0 (3); wherein
d.sub.12W designates the distance between the first and second lens
groups at the short focal length extremity; d.sub.12T designates
the distance between the first and second lens groups at the long
focal length extremity; f.sub.W designates the focal length of the
entire zoom lens system at the short focal length extremity;
f.sub.T designates the focal length of the entire zoom lens system
at the long focal length extremity; f.sub.12W designates the
combined focal length of the first and second lens groups at the
short focal length extremity; and f.sub.3G designates the focal
length of the third lens group.
Inventors: |
Enomoto, Takashi; (Chiba,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
|
Assignee: |
ASAHI KOGAKU KOGYO KABUSHIKI
KAISHA
|
Family ID: |
18498967 |
Appl. No.: |
09/745799 |
Filed: |
December 26, 2000 |
Current U.S.
Class: |
359/689 ;
359/682; 359/695 |
Current CPC
Class: |
G02B 15/143503
20190801 |
Class at
Publication: |
359/689 ;
359/695; 359/682 |
International
Class: |
G02B 015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 1999 |
JP |
11-371587 (P) |
Claims
What is claimed is:
1. A zoom lens system comprising a negative first lens group, a
positive second lens group, and a negative third lens group, in
this order from an object, wherein the combined power of said
negative first lens group and said positive second lens group is
positive, wherein upon zooming from the short focal length
extremity towards the long focal length extremity, all of said
three lens groups are arranged to be monotonously moved from the
image side towards the object side, and wherein said zoom lens
system satisfies the following
conditions:0.01<(d.sub.12W-d.sub.12T)/f.sub.W&-
lt;0.13.5<f.sub.T/f.sub.12W<6.04.0<f.sub.T/.vertline.f.sub.3G.ver-
tline.<8.0wherein d.sub.12W designates the distance between said
first lens group and said second lens group at the short focal
length extremity; d.sub.12T designates the distance between said
first lens group and said second lens group at the long focal
length extremity; f.sub.W designates the focal length of the entire
zoom lens system at the short focal length extremity; f.sub.T
designates the focal length of the entire zoom lens system at the
long focal length extremity; f.sub.12W designates the combined
focal length of said first lens group and said second lens group at
the short focal length extremity; and f.sub.3G designates the focal
length of said third lens group.
2. The zoom lens system according to claim 1, satisfying the
following
condition:0<log.sub.eZ.sub.12/log.sub.eZ<0.07wherein
Z.sub.12=f.sub.12T/f.sub.12W; Z=f.sub.T/f.sub.W; and f.sub.12T
designates the combined focal length of said first lens group and
said second lens group at the long focal length extremity.
3. The zoom lens system according to claim 1, satisfying the
following condition:-2.5 <f.sub.T/f.sub.1G-<0.5wherein
f.sub.1G designates the focal length of said first lens group.
4. The zoom lens system according to claim 1, wherein said first
lens group comprises a positive first sub-lens group and a negative
second sub-lens group, in this order from said object, wherein said
first sub-lens group comprises a positive single lens element, and
satisfies the following
condition:1.4<f.sub.T/f.sub.1P<4.0wherein f.sub.1P designates
the focal length of said first sub-lens group.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a zoom lens system of a
compact camera, and in particular, to attaining a high zoom ratio
and miniaturization of the zoom lens system.
[0003] 2. Description of the Related Art
[0004] A zoom lens system for a compact camera does not require a
long back focal distance, unlike a zoom lens system for a single
lens reflex (SLR) camera in which a space to provide a mirror
behind the photographing lens system is required. Accordingly, in a
compact camera, a telephoto type lens system including a positive
lens group and a negative lens group, in this order from the
object, has been employed, while in a SLR camera, a retrofocus type
lens system including a negative lens group and a positive lens
group, in this order from the object, has been employed. In the
above two-lens-group conventional zoom lens system for a compact
camera, if an attempt is made to obtain a zoom ratio of about 3.5,
it has been difficult to correct aberrations, in particular,
curvature of field. Therefore a three-lens-group zoom lens system
in which each lens group is arranged to move independently upon
zooming has been employed. In such a three-lens-group zoom lens
system, a high zoom ration is obtained by moving all the three lens
groups. For example, in the case where a three-lens-group zoom lens
system including a positive lens group, a positive lens group and a
negative lens group, in this order from the object, is provided,
the distance between the first and second lens groups has to be
made long in order to obtain a high zoom ratio. However, if an
attempt is made to obtain a zoom ratio of about 3.5 in the above
conventional positive-positive-negative zoom lens system, the
distance, at the short focal length extremity, between the most
object-side surface of the first lens group and the most image-side
surface of the second lens group becomes long, and the diameter of
the most object-side lens element in the first lens group has to be
made large in order to maintain light amount at and around the
short focal length extremity. An increase of the diameter of the
most object-side lens element is quite disadvantageous for
miniaturization of a camera.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a
miniaturized three-lens-group zoom lens system which (i) has a zoom
ratio of about 3.5, and (ii) can reduce the diameter of the most
object-side lens element in the most object-side lens group, though
the zoom lens system is the three-lens-group arrangement.
[0006] In order to achieve the above-mentioned object, there is
provided a zoom lens system including a negative first lens group,
a positive second lens group, and a negative third lens group, in
this order from the object. The combined power of the negative
first lens group and the positive second lens group is positive. In
the zoom lens system, upon zooming from the short focal length
extremity towards the long focal length extremity, all the three
lens groups are arranged to be monotonously moved from the image
side towards the object side. Further, the zoom lens system
satisfies the following conditions:
0.01<(d.sub.12W-d.sub.12T)/f.sub.W<0.1 (1)
3.5<f.sub.T/f.sub.12W<6.0 (2)
4.0<f.sub.T/.vertline.f.sub.3G.vertline.8.0 (3)
[0007] wherein
[0008] d.sub.12W designates the distance between the first lens
group and the second lens group at the short focal length
extremity;
[0009] d.sub.12T designates the distance between the first lens
group and the second lens group at the long focal length
extremity;
[0010] f.sub.W designates the focal length of the entire zoom lens
system at the short focal length extremity;
[0011] f.sub.T designates the focal length of the entire zoom lens
system at the long focal length extremity;
[0012] f.sub.12W designates the combined focal length of the first
lens group and the second lens group at the short focal length
extremity; and
[0013] f.sub.3G designates the focal length of the third lens
group.
[0014] The zoom lens system according to the present invention can
constitute a telephoto type zoom lens system which has a positive
front lens group and a negative rear lens group. This is because
both the first lens group and the second lens group can be
considered to be a front lens group due to the above-explained
positive combined power thereof, and the negative third lens group
can be considered to be the rear lens group.
[0015] The zoom lens system of the present invention preferably
satisfies the following condition:
0<log.sub.eZ.sub.12/log.sub.eZ<0.07 (4)
[0016] wherein
[0017] Z.sub.12=f.sub.12 T/f.sub.12W;
[0018] Z=f.sub.T/f.sub.W; and
[0019] f.sub.12T designates the combined focal length of the first
lens group and the second lens group at the long focal length
extremity.
[0020] The zoom lens system of the present invention preferably
satisfies the following condition:
-2.5<f.sub.T/f.sub.3G<-0.5 (5)
[0021] wherein
[0022] f.sub.1G designates the focal length of the first lens
group.
[0023] For example, the first lens group can be constituted by a
positive first sub-lens group and a negative second sub-lens group,
in this order from the object. In this case, preferably, the first
sub-lens group includes a positive single lens element, and
satisfies the following condition:
1.4<f.sub.T/f.sub.1P<4.0 (6)
[0024] wherein
[0025] f.sub.1P designates the focal length of the first sub-lens
group.
[0026] The present disclosure relates to subject matter contained
in Japanese Patent Application No. Hei-11-371587 (filed on Dec. 27,
1999) which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention will be discussed below in detail with
reference to the accompanying drawings, in which:
[0028] FIG. 1 is a lens arrangement of a zoom lens system according
to a first embodiment of the present invention;
[0029] FIGS. 2A, 2B, 2C and 2D show aberrations, at the short focal
length extremity, occurred in the lens arrangement shown in FIG.
1;
[0030] FIGS. 3A, 3B, 3C and 3D show aberrations, at an intermediate
focal length, of the lens arrangement shown in FIG. 1;
[0031] FIGS. 4A, 4B, 4C and 4D show aberrations, at the long focal
length extremity, of the lens arrangement shown in FIG. 1;
[0032] FIG. 5 is a lens arrangement of a zoom lens system according
to a second embodiment of the present invention;
[0033] FIGS. 6A, 6B, 6C and 6D show aberrations, at the short focal
length extremity, occurred in the lens arrangement shown in FIG.
5;
[0034] FIGS. 7A, 7B, 7C and 7D show aberrations, at an intermediate
focal length, of the lens arrangement shown in FIG. 5;
[0035] FIGS. 8A, 8B, 8C and 8D show aberrations, at the long focal
length extremity, of the lens arrangement shown in FIG. 5;
[0036] FIG. 9 is a lens arrangement of a zoom lens system according
to a third embodiment of the present invention;
[0037] FIGS. 10A, 10B, 10C and 10D show aberrations, at the short
focal length extremity, occurred in the lens arrangement shown in
FIG. 9;
[0038] FIGS. 11A, 11B, 11C and 11D show aberrations, at an
intermediate focal length, of the lens arrangement shown in FIG.
9;
[0039] FIGS. 12A, 12B, 12C and 12D show aberrations, at the long
focal length extremity, of the lens arrangement shown in FIG. 9;
and
[0040] FIG. 13 shows the lens-group moving paths for the first
through third embodiments.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] As shown in the lens-group moving paths of FIG. 13, the zoom
lens system of the present invention includes a negative first lens
group 10, a positive second lens group 20, and a negative third
lens group 30, in this order from the object. Upon zooming from the
short focal length extremity towards the long focal length
extremity, all the lens groups move from the image side towards the
object side, while the distances therebetween are varied. In
particular, as shown in FIG. 13, in regard to the distance
d.sub.12W between the negative first lens group 10 and the positive
second lens group 20 at the short focal length extremity, and the
distance d.sub.12T therebetween at the long focal length extremity,
it should be understood that the difference between these distances
is small A diaphragm S is provided between the second lens group 20
and the third lens group 30, and moves together with the second
lens group 20.
[0042] Condition (1) specifies the change of the distances
d.sub.12W and d.sub.12T between the first lens group 10 and the
second lens group 20, respectively at the short focal length
extremity and the long focal length extremity. By reducing the
change of the distances therebetween (d.sub.12W-d.sub.12T) so that
condition (1) is satisfied, the distance, at the short focal length
extremity, from the most object-side surface of the first lens
group 10 to the most image-side surface of the second lens group 20
can be reduced, and the diameter of the most object-side lens
element of the first lens group 10 can be reduced, thereby
miniaturization of the lens system can be attained.
[0043] If (d.sub.12W-d.sub.12T)/f.sub.W exceeds the upper limit of
condition (1), the amount of the distance-change between the first
lens group 10 and the second lens group 20 becomes large, so that
it is difficult to attain miniaturization of the lens system.
[0044] If (d.sub.12W-d.sub.12T)/f.sub.W exceeds the lower limit of
condition (1), an effect of zooming due to changing the distance
between the first lens group 10 and the second lens group 20 cannot
be obtained.
[0045] Condition (2) specifies the combined focal length of the
first lens group 10 and the second lens group 20. By satisfying
this condition, the traveling distances of the first and second
lens groups can be reduced, so that miniaturization of the lens
system can be attained.
[0046] If f.sub.T/f.sub.12W exceeds the upper limit of condition
(2), the combined power of the first lens group 10 and that of the
second lens group 20 become too strong, so that aberrations
occurred in these lens groups become large. Consequently,
fluctuations of aberrations upon zooming becomes large.
[0047] If f.sub.T/f.sub.12W exceeds the lower limit of condition
(2), the traveling distances of the first and second lens groups
become long, so that it is difficult to attain miniaturization of
the lens system.
[0048] Condition (3) specifies the focal length of the negative
third lens group 30. By satisfying this condition, the traveling
distance of the third lens group 30 can be reduced, so that
miniaturization of the lens system can be attained.
[0049] If f.sub.T/.vertline.f.sub.3G.vertline. exceeds the upper
limit of condition (3), the power of the third lens group 30
becomes too strong. As a result, aberrations occurred in the third
lens group 30 become large, so that fluctuations of aberrations
upon zooming become large.
[0050] If f.sub.T/.vertline.f.sub.3G.vertline. exceeds the lower
limit of condition (3), the traveling distance of the third lens
group 30 becomes long, so that miniaturization of the lens system
cannot be attained.
[0051] Condition (4) specifies the combined focal length of the
first lens group 10 and the second lens group 20. By satisfying
this condition, the change of the distance between these lens
groups can be reduced, and miniaturization of the lens system
cannot be attained.
[0052] If log.sub.eZ.sub.12/log.sub.eZ exceeds upper limit of
condition (4) the change of the distance between the first and
second lens groups becomes large, so that miniaturization of the
lens system cannot be attained.
[0053] If log.sub.eZ.sub.12/log.sub.eZ exceeds lower limit of
condition (4), an effect of zooming due to changing the distance
between the first lens group 10 and the second lens group 20 cannot
be obtained.
[0054] Condition (5) specifies the focal length of the negative
first lens group 10. By satisfying this condition, the traveling
distance of the first lens group 10 can be reduced, so that
miniaturization of the lens system can be attained.
[0055] If f.sub.T/f.sub.1G exceeds the upper limit of condition
(5), the traveling distance of the first lens group 10 becomes
long, so that miniaturization of the lens system cannot be
attained.
[0056] If f.sub.T/f.sub.1G exceeds the lower limit of condition
(5), the power of the first lens group 10 becomes too strong,
aberrations occurred therein become large. As a result,
fluctuations of aberrations upon zooming is large.
[0057] Condition (6) specifies the focal length of a positive first
sub-lens group 10a in the case where the negative first lens group
10 includes the positive first sub-lens group 10a and a negative
second sub-lens group 10b in this order from the object. By
satisfying this condition, the divergence of the negative first
lens group 10 can be corrected, so that aberrations occurred
therein can be made small.
[0058] If f.sub.T/f.sub.1P exceeds the upper limit of condition
(6), the power of the first sub-lens group 10a becomes too strong,
so that production thereof is difficult.
[0059] If f.sub.T/f.sub.1P exceeds the lower limit of condition
(6), diverging aberrations in the negative first lens group 10
cannot be reduced.
[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 solid line and
the two types of dotted lines respectively indicate magnification
with respect to the d, g and C lines. 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 (.degree.), 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 v
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 (1/r);
[0065] h 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] [Embodiment 1]
[0072] FIG. 1 is a lens arrangement of a zoom lens system according
to the first embodiment of the present invention. FIGS. 2A through
2D show aberrations, at the short focal length extremity, occurred
in the lens arrangement shown in FIG. 1. FIGS. 3A through 3D show
aberrations, at an intermediate focal length, of the lens
arrangement shown in FIG. 1. FIGS. 4A through 4D show aberrations,
at the long focal length extremity, of the lens arrangement shown
in FIG 1. Table 1 shows the numerical data thereof. Surface Nos. 1
through 5 represent the negative first lens group 10, surface Nos.
6 through 10 represent the positive second lens group 20, and
surface Nos. 11 through 14 represent the negative third lens group
30. The first lens group 10 is constituted by a positive lens
element, and cemented lens elements including a negative lens
element and a positive lens element, in this order from the object.
The second lens group 20 is constituted by a positive lens element,
and cemented lens elements including a positive lens element and a
negative lens element, in this order from the object. The third
lens group 30 is constituted by a positive lens element and a
negative lens element, in this order from the object. Furthermore,
the first lens group 10 is constituted by a positive first sub-lens
group (single lens element) 10a (surface Nos. 1 and 2), and a
negative second sub-lens group (negative-positive cemented lens
elements in this order from the object) 10b (surface Nos. 3 through
5).
1TABLE 1 F.sub.NO = 1:5.3-6.9-12.5 f = 39.00-70.00-135.00 (zoom
ratio: 3.46) W = 28.3-16.9-9.1 f.sub.B = 10.73-35.41-86.88 Surface
No. r d Nd .nu. 1 24.813 2.30 1.48000 70.0 2 -593.823 0.93 -- -- 3
-18.110 1.20 1.64757 38.9 4 75.529 2.06 1.68893 31.1 5* -385.488
4.06-3.60-3.14 -- -- 6 -1535.221 2.62 1.48749 70.2 7 -24.075 0.10
-- -- 8 38.413 3.26 1.52882 57.7 9 -10.631 1.10 1.81612 44.4 10
-19.305 1.00 -- -- Diaphragm .infin. 11.60-5.62-1.99 -- -- 11*
-56.547 2.53 1.58547 29.9 12 -21.271 3.45 -- -- 13 -10.106 1.40
1.77500 49.7 14 -102.555 -- -- -- *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 5 0.00 -0.1848 .times. 10.sup.-4 -0.4397
.times. 10.sup.-7 -- 11 0.00 0.7054 .times. 10.sup.-4 0.3686
.times. 10.sup.-6 0.2590 .times. 10.sup.-8
[0074] [Embodiment 2]
[0075] FIG. 5 is a lens arrangement of a zoom lens system according
to the second embodiment of the present invention. FIGS. 6A through
6D show aberrations, at the short focal length extremity, occurred
in the lens arrangement shown in FIG. 5. FIGS. 7A through 7D show
aberrations, at an intermediate focal length, of the lens
arrangement shown in FIG. 5. FIGS. 8A through 8D show aberrations,
at the long focal length extremity, of the lens arrangement shown
in FIG. 5. Table 2 shows the numerical data thereof. The basic lens
construction and the movement of the lens groups is the same as the
first embodiment.
3TABLE 2 F.sub.NO = 1:5.3-6.9-128 f = 39.00-70.00-140.00 (zoom
ratio: 3.59) W = 28.4-16.9-8.8 f.sub.B = 9.14-34.20-90.60 Surface
No. r d Nd .nu. 1 24.518 2.30 1.55234 59.2 2 -296.557 1.03 -- -- 3
-17.830 1.20 1.80460 33.0 4 19.584 2.56 1.72870 28.2 5 -68.966
2.58-2.30-2.02 -- -- 6 --219.350 2.62 1.48749 70.2 7 -15.969 0.10
-- -- 8 111.163 3.26 1.49877 61.6 9 -11.101 1.10 1.80400 46.6 10
-19.450 1.00 -- -- Diaphragm .infin. 13.23-6.34-1.99 -- -- 11*
-42.253 2.53 1.58547 29.9 12 -22.886 4.17 -- -- 13 -10.292 1.40
1.69000 56.2 14 -86.931 -- -- -- *designates the aspherical surface
which is rotationally symmetrical with respect to the optical
axis.
[0076] Aspherical surface data (the aspherical surface coefficients
not indicated are zero (0.00)):
4 Surf. No. K A4 A6 A8 11 0.00 0.7141 .times. 10.sup.-4 0.1977
.times. 10.sup.-6 0.3589 .times. 10.sup.-8
[0077] [Embodiment 3]
[0078] FIG. 9 is a lens arrangement of a zoom lens system according
to the third embodiment of the present invention. FIGS. 10A through
10D show aberrations, at the short focal length extremity, occurred
in the lens arrangement shown in FIG. 9. FIGS. 11A through 11D show
aberrations, at an intermediate focal length, of the lens
arrangement shown in FIG. 9. FIGS. 12A through 12D show
aberrations, at the long focal length extremity, of the lens
arrangement shown in FIG. 9. Table 3 shows the numerical data
thereof. Surface Nos. 1 through 4 represent the negative first lens
group 10, surface Nos. 5 through 9 represent the positive second
lens group 20, and surface Nos. 10 through 13 represent the
negative third lens group 30. The first lens group 10 is
constituted by a positive lens element, and a negative lens
element, in this order from the object. The second lens group 20 is
constituted by a positive lens element, and cemented lens elements
including a positive lens element and a negative lens element, in
this order from the object. The third lens group 30 is constituted
by a positive lens element and a negative lens element, in this
order from the object. Furthermore, the first lens group 10 is
constituted by a positive first sub-lens group (single lens
element) 10a (surface Nos. 1 and 2), and a negative second sub-lens
group (single lens element) 10b (surface Nos. 3 and 4).
5TABLE 3 F.sub.NO = 1:5.3-6.9-12.5 f = 39.00-70.00-135.00 (zoom
ratio: 3.46) W = 28.4-16.9-9.1 f.sub.B = 8.72-33.19-84.22 Surtace
No. r d Nd .nu. 1 20.889 2.30 1.48089 69.6 2 184.972 1.18 -- -- 3*
-17.730 1.50 1.84666 41.7 4* -70.882 3.22-3.00-2.72 -- -- 5
-197.826 2.62 1.48030 67.6 6 -15.553 0.70 -- -- 7 111.299 3.26
1.50101 58.2 8 -10.429 1.10 1.80400 46.6 9 -18.074 1.00 -- --
Diaphragm .infin. 13.01-6.17-2.04 -- -- 10* -51.096 2.53 1.58547
29.9 11 -26.692 4.41 -- -- 12 -10.340 1.40 1.69000 56.2 13 -83.401
-- -- -- *designates the aspherical surface which is rotationally
symmetrical with respect to the optical axis.
[0079] Aspherical surface data (the aspherical surface coefficients
not indicated are zero (0.00)):
6 Surf. No. K A4 A6 A8 3 0.00 0.2451 .times. 10.sup.-4 -0.5420
.times. 10.sup.-6 -- 4 0.00 0.2998 .times. 10.sup.-4 -0.5386
.times. 10.sup.-6 -- 10 0.00 0.7348 .times. 10.sup.-4 0.1225
.times. 10.sup.-6 0.3939 .times. 10.sup.-8
[0080] Table 4 shows the numerical values of each condition of each
embodiment.
7 TABLE 4 Embodiment 1 Embodiment 2 Embodiment 3 Cond.(1) 0.024
0.015 0.013 Cond.(2) 5.25 5.11 4.89 Cond.(3) 6.49 6.26 6.14
Cond.(4) 0.011 0.006 0.007 Cond.(5) -1.57 -1.60 -1.74 Cond.(6) 2.72
3.41 2.77
[0081] As can be understood by the above, each embodiment satisfies
each condition. Furthermore, as shown in the aberration diagrams,
the various aberrations are adequately corrected.
[0082] [0024]
[0083] According to the above description, a miniaturized
three-lens-group zoom lens system which has the following features
can be obtained, though the zoom lens system is the
three-lens-group arrangement in which a negative lens group, a
positive lens group and a negative lens group in this order from
the object are provided:
[0084] (i) a zoom ratio is about 3.5; and
[0085] (ii) the diameter of the most object-side lens element in
the most object-side lens group can be reduced.
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