U.S. patent application number 09/761836 was filed with the patent office on 2001-07-26 for zoom lens system, and image pickup system using the same.
Invention is credited to Kashiki, Yasutaka.
Application Number | 20010009479 09/761836 |
Document ID | / |
Family ID | 18537778 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009479 |
Kind Code |
A1 |
Kashiki, Yasutaka |
July 26, 2001 |
Zoom lens system, and image pickup system using the same
Abstract
The invention provides a compact, low-cost zoom lens system
comprising a positive lens group and a negative lens group. The
system comprises a first lens group G1 having positive refracting
power and a second lens group G2 having negative refracting power.
The second lens group comprises, in order from an object side
thereof, a positive lens 2-1, a negative lens 2-2 and a negative
lens 2-3. The lens 2-1 is a plastic lens. The second lens group G2
further satisfies: 1.05.ltoreq.f.sub.21/f.sub.T<5 (1)
3.8<f.sub.22/f.sub.G2<8 (2) Here f.sub.21 is the focal length
of lens 2-1 in the second lens group, f.sub.22 is the focal length
of lens component 2-2 in the second lens group, f.sub.T is the
focal length of the zoom lens system, and f.sub.G2 is the composite
focal length of the second lens group.
Inventors: |
Kashiki, Yasutaka; (Tokyo,
JP) |
Correspondence
Address: |
Pillsbury Madisosn & Sutro LLP
Intellectual Property Group
East Tower, Ninth Floor
1100 New York Avenue, N.W.
Washington
DC
20005-3918
US
|
Family ID: |
18537778 |
Appl. No.: |
09/761836 |
Filed: |
January 18, 2001 |
Current U.S.
Class: |
359/692 ;
359/691 |
Current CPC
Class: |
G02B 15/142 20190801;
G02B 15/1421 20190801 |
Class at
Publication: |
359/692 ;
359/691 |
International
Class: |
G02B 015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2000 |
JP |
2000-009656 |
Claims
What we claim is:
1. A zoom lens system comprising, in order from an object side of
the zoom lens system, a first lens group having positive refracting
power and a second lens group having negative refracting power,
wherein: said second lens group comprises, in order from an object
side thereof, a positive lens component 2-1, a negative lens
component 2-2 and a negative lens component 2-3, with said lens
component 2-1 comprising a plastic lens element, and said second
lens group satisfies the following conditions (1) and (2):
1.05.ltoreq.f.sub.21/f.sub.T<5 (1) 3.8<f.sub.22/f.sub.G2<8
(2) where f.sub.21 is a focal length of said lens component 2-1 in
said second lens group, f.sub.22 is a focal length of said lens
component 2-2 in said second lens group, f.sub.T is a focal length
of said zoom lens system at a telephoto end thereof, and f.sub.G2
is a composite focal length of said second lens group.
2. The zoom lens system according to claim 1, wherein said first
lens group comprises, in order from an object side thereof, a front
lens unit comprising a negative lens component 1-1 and a positive
lens component 1-2 and having negative refracting power and a rear
lens unit comprising a positive lens component, said lens component
1-2 being a plastic lens component including an aspherical surface
whose off-axis power is smaller than axial power.
3. The zoom lens system according to claim 1 or 2, which further
satisfies the following condition (3):
1<(R.sub.22r+R.sub.23f)/(R.sub.22r-R.sub.- 23f)<2.5 (3) where
R.sub.22r is an image-side radius of curvature of said lens
component 2-2 in said second lens group, and R.sub.23f is the
object-side radius of curvature of said lens 2-3 component in said
second lens group.
4. A zoom lens system comprising, in order from an object side of
the zoom lens system, a first lens group having positive refracting
power and a second lens group having negative refracting power,
wherein: said second lens group comprises, in order from an object
side thereof, a positive lens component 2-1, a negative lens
component 2-2 and a negative lens component 2-3, with said lens
component 2-1 comprising a plastic lens element, and said second
lens group satisfies the following conditions (1), (2) and (4):
1.05.ltoreq.f.sub.21/f.sub.T<5 (1) 3.8<f.sub.22/f.sub.G2<8
(2) 1.01.ltoreq.S.sub.G21<1.24 (4) where f.sub.21 is a focal
length of said lens component 2-1 in said second lens group,
f.sub.22 is a focal length of said lens component 2-2 in said
second lens group, f.sub.T is a focal length of said zoom lens
system at a telephoto end thereof, f.sub.G2 is a composite focal
length of said second lens group, and S.sub.G21 is a specific
gravity of said lens component 2-1 in said second lens group.
5. The zoom lens system according to claim 1 or 4, wherein said
positive lens component 2-1 is only one positive lens component in
said second lens group, and is disposed nearest to an object side
of said second lens group.
6. The zoom lens system according to claim 2, wherein said positive
lens component 1-2 is designed to correct fluctuations of focal
length with temperature changes within the same.
7. The zoom lens system according to claim 2, wherein said front
lens unit in said first lens group consists of, in order from an
object side thereof, a negative meniscus lens element and a
positive meniscus lens element convex on an object side
thereof.
8. The zoom lens system according to claim 2 or 7, wherein said
rear lens unit in said first lens group consists of a positive
double-convex lens component.
9. The zoom lens system according to claim 1, 2 or 4, wherein said
second lens group consists of, in order from an object side
thereof, a positive meniscus lens element concave on an object side
thereof, a negative lens element concave on an object side thereof
and a negative meniscus lens element concave on an object side
thereof.
10. The zoom lens system according to claim 2, wherein an
object-side surface of said lens component 1-2 in said first lens
group and an object-side surface of said positive lens component
2-1 in said second lens group are defined by aspherical
surfaces.
11. The zoom lens system according to claim 2, wherein a surface of
said positive lens component 1-2 in said first lens group, said
surface being disposed on the object side of said first lens group,
is defined by said aspherical surface that has positive power on an
optical axis and is configured in such a way as to have a point of
inflexion on section including said optical axis.
12. The zoom lens system according to claim 1, 2 or 4, wherein
between said first lens group and said second lens group there is
disposed a stop that moves together with said first lens group
during zooming.
13. The zoom lens system according to claim 1, 2 or 3, wherein upon
zooming from a wide-angle end to a telephoto end of said zoom lens
system, said first lens group, and said second lens group moves
toward the object side of said zoom lens system with a varying
space therebetween.
14. The zoom lens system according to claim 1, 2 or 4, wherein of
lens groups comprising lenses, only said first and second lens
groups move upon zooming from the wide-angle end to the telephoto
end, with a zoom ratio of 2.5 or greater.
15. The zoom lens system according to claim 14, wherein said zoom
ratio is 3.1 or greater.
16. An image pickup system wherein the zoom lens system according
to claim 1, 2 or 4 is used as an image pickup system and a viewing
device to observe an image formed by said zoom lens system is
provided.
Description
[0001] This application claims benefit of Japanese Patent
Application(s) No. 2000-9656 filed in Japan on Jan. 19, 2000, the
contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
[0002] So far, a number of zoom lens systems, each comprising two
lens groups or a positive and a negative lens group, wherein the
space between them is varied for zooming, have been known as
effective arrangements for achieving size and cost reductions and
capable of zooming with a simple mechanism. Recently developed zoom
lens system are increasingly required to have higher zoom ratios
than ever before. Prior zoom lens arrangements to meet such
requirements are disclosed in JP-A's 9-90220, 9-96761, etc.
[0003] These arrangements comprising a relatively small number of
lenses have a zoom ratio of 2 to 3, and some of them have a zoom
ratio of 3 or greater. To reduce the number of lenses used, the
second lens group is composed of two lenses or a positive and a
negative lens (one of which is an aspherical lens). By making
correction for aberrations in the second lens group, performance is
maintained all over the zooming zone. However, there is severe
degradation of performance due to decentration in the second lens
group, because various aberrations are corrected with two lenses.
In addition, the power of the second lens group must be increased
because the overall negative power of the diverging second lens
group is compensated for by the negative lens in the second lens
group. This is unfavorable for correction of aberrations.
[0004] Referring to JP-A's 5-119258, 4-22911, etc., a compact yet
wide-angle zoom lens system is disclosed. The second lens group is
composed of three lenses or a positive, a negative and a negative
lens so that various aberrations therein can be corrected. The
power of the second lens group is allocated to the three lenses so
that the degradation of performance due to decentration can be
reduced. However, all three lenses are formed of glass, and so the
second lens group is higher in cost than that made up of two
lenses. In addition, the back focus is short. This does not only
add mechanical constrains to the zoom lens system but also offers
several problems such as transfer onto film of dust deposits on the
surface of a lens in the vicinity of an image plane, an increase in
the diameter of the rear lens, etc. The zoom ratio is far short of
2.
[0005] Referring to JP-A 3-267909, etc., the second lens is
composed of three lenses or a positive, a negative and a negative
lens, with the positive lens being formed of a plastic lens. A
plastic lens is excellent in mass productivity, and so has the
merit of achieving lower costs as compared with a glass lens.
However, a problem with the plastic lens is that its refractive
index and shape are prone to large variations depending on ambient
temperatures. Accordingly, meticulous care must be taken when the
plastic lens is used for a camera's phototaking optical system. To
this end, it is often attempted to make the power of the plastic
lens weak. However, such care is not found in the example of JP-A
3-267909 because the power of the plastic lens is still strong.
[0006] Referring then to JP-A's 5-119258, 10-197793, etc., the
second lens group is composed of three lenses or a positive, a
negative and a negative lens, with the positive lens being formed
of a plastic lens, as is the case with JP-A 3-267909. In
consideration of the changes of the plastic lens depending on
ambient temperatures, the power of the plastic lens is made weak.
However, when the power becomes too weak, the effect on correction
of aberrations becomes slender. In addition, the principal point
positions of the second lens group are shifted to the object side
under the power of the second negative lens, resulting in problems
such as a decreased back focus. For this reason, how the power of
the second negative lens located at a middle position in the second
negative lens is determined is important for power profile. The
examples show that the power of the second negative lens group is
still strong, resulting in a decreased back focus. This does not
only add mechanical constrains to the zoom lens system but also
offers several problems such as transfer onto film of dust deposits
on the surface of a lens in the vicinity of an image plane, an
increase in the diameter of the rear lens, etc. When the power of
the second negative lens is too weak, on the other hand, the effect
on correction of aberrations becomes slender; in other words, the
merit of +-- construction is lost.
SUMMARY OF THE INVENTION
[0007] In view of such problems associated with the prior art, an
object of the present invention is to provide a compact, low-cost
zoom lens system of +- construction, which comprises two lens
groups, and an image pickup system using the same.
[0008] According to one aspect of the invention, this object is
achieved by the provision of a zoom lens system comprising, in
order from an object side of the zoom lens system, a first lens
group having positive refracting power and a second lens group
having negative refracting power, wherein:
[0009] said second lens group comprises, in order from an object
side thereof, a positive lens component 2-1, a negative lens
component 2-2 and a negative lens component 2-3, with said lens
component 2-1 comprising a plastic lens element, and
[0010] said second lens group satisfies the following conditions
(1) and (2):
1.05.ltoreq.f.sub.21/f.sub.T<5 (1)
3.8<f.sub.22/f.sub.G2<8 (2)
[0011] where f.sub.21 is the focal length of the lens component 2-1
in the second lens group, f.sub.22 is the focal length of the lens
component 2-2 in the second lens group, f.sub.T is the focal length
of the zoom lens system at a telephoto end thereof, and f.sub.G2 is
the composite focal length of the second lens group.
[0012] According to another aspect of the invention, there is
provided a zoom lens system comprising, in order from an object
side of the zoom lens system, a first lens group having positive
refracting power and a second lens group having negative refracting
power, wherein:
[0013] said second lens group comprises, in order from an object
side thereof, a positive lens component 2-1, a negative lens
component 2-2 and a negative lens component 2-3, with said lens
component 2-1 comprising a plastic lens element, and
[0014] said second lens group satisfies the following conditions
(1), (2) and (4):
1.05.ltoreq.f.sub.21/f.sub.T<5 (1)
3.8<f.sub.22/f.sub.G2<8 (2)
1.01.ltoreq.SG.sub.21<1.24 (4)
[0015] where f.sub.21 is the focal length of the lens component 2-1
in the second lens group, f.sub.22 is the focal length of the lens
component 2-2 in said second lens group, f.sub.T is the focal
length of the zoom lens system at a telephoto end thereof, f.sub.G2
is the composite focal length of the second lens group, and
SG.sub.21 is the specific gravity of the lens component 2-1 in the
second lens group.
[0016] Why the aforesaid arrangements are used in the invention,
and how they work is now explained.
[0017] According to the present invention, the zoom lens system
comprises a first lens group having positive refracting power and a
second lens group having negative refracting power. The second lens
group then comprises a positive lens 2-1, a negative lens 2-2 and a
negative lens 2-3. The positive lens 2-1 is formed of a plastic
lens. This arrangement is of the simplest two-group construction in
zoom lens constructions, and is constructed of the telephoto type
so as to achieve size reductions on the telephoto side. By
providing the diverging second lens group of +-- construction, and
especially allocating the high proportion of negative refracting
power to two lenses, it is possible to reduce the influence of
decentration produced within the second lens group and make
correction for aberrations, especially off-axis coma. By
constructing the positive lens 2-1 of a plastic lens, size and
weight reductions can be achieved.
[0018] Referring here to why the plastic lens is used for the lens
2-1 rather than for the lenses 2-2 and 2-3, the lens 2-1 is only
the positive lens in the second lens group that has generally
negative power, and so can be constructed with a relatively gentle
power. In addition, the lens 2-1 is the outermost lens favorable
for assembly control. For instance, a plastic lens is fabricated by
an injection molding process that does not rely on the centering
step needed for glass lenses. This is favorable in consideration of
cost, but makes the surface of the lens prone to decentration with
respect to the outside shape of the lens. For this reason, it is
desired to control the decentration of the plastic lens during
assembly. The control should then preferably be carried out with
respect to the axes of other lenses forming the same group. This is
the reason that the plastic lens should preferably be disposed at
the outermost position. How to perform this control, for instance,
is set forth in JP-A 6-265766.
[0019] Condition (1) provides a definition of the focal length
ratio of the lens 2-1 with respect to the zoom lens system at the
telephoto end. The outermost lens or plastic lens 2-1 varies in
shape and refractive index with temperatures. Such variations occur
largely at the telephoto end of the zoom lens system, and have some
considerable influences on image-formation capabilities and focal
shifts as well. When the lower limit of 1.05 to this condition is
not reached, the focal length of the lens 2-1 becomes short (or the
refracting power thereof increases strong), resulting in
unacceptably large changes of the focal length due to temperature,
etc. When the upper limit of 5 is exceeded, the focal length of the
lens 2-1 becomes too long to make correction for aberrations,
especially chromatic aberrations. This phenomenon becomes
perceptible with increasing zoom ratios.
[0020] It is here noted that the lower and upper limits to
condition (1) may be 1.3 and 3.5, respectively.
[0021] Condition (2) provides a definition of the ratio of the
focal length of the lens 2-2 with respect to the composite focal
length of the second lens group. To satisfy this condition, the
combined negative power of the lenses 2-2 and 2-3 must be stronger
than the overall negative power of the rear lens group (the second
lens group). Basically, positive and negative powers are allocated
to the object and image sides of the second lens group,
respectively, so that the principal points thereof can be
positioned on the object side. By meeting condition (2) in
consideration of such requirements, it is possible to ensure the
preferable positions for the principal points of the second lens
group, and make correction for aberrations of the lens 2-2 in
particular. To be more specific, when the lower limit 3.8 to
condition (2) is not reached, the proportion of the refracting
power of the lens 2-2 in the second lens group becomes large, and
so the principal points of the second lens group are shifted toward
the object side in the second lens group; that is, the second lens
group is as a whole positioned on the image plane side of the zoom
lens system. This makes it difficult to ensure any satisfactory
back focus. The reduced back focus does not only add mechanical
constrains to the zoom lens system but also offers problems such as
lens diameter increases, transfer onto film of dust deposits on
lens surfaces, etc. When the upper limit of 8 is exceeded, the
refracting power of the lens 2-2 becomes too weak to make effective
correction for aberrations.
[0022] It is here noted that the upper and lower limits to
condition (2) may be 5.0 and 7.4, respectively.
[0023] By meeting such requirements as mentioned above, it is
possible to achieve a compact, low-cost zoom lens system.
[0024] In the zoom lens system of such construction as described
above, the first lens group comprises, in order from an object side
thereof, a front lens unit comprising a negative lens 1-1 and a
positive lens 1-2 and having negative refracting power and a rear
lens group comprising a positive lens. Preferably in this case, the
lens 1-2 is a plastic lens comprising an aspherical surface whose
off-axis power is smaller than axial power.
[0025] By the wording "aspherical surface whose off-axis power is
smaller than axial power" used herein is intended an aspherical
surface including a surface region wherein, when the axial power is
positive power, the off-axis power is smaller than that, and an
aspherical surface including a surface region wherein, when the
axial power is negative power, the off-axis negative power is
stronger than that.
[0026] Since the power profile of the first lens group is of the -+
retrofocus type, it is possible to locate the principal points in
the first lens group in the rear of the first lens group and so
ensure some space between the first and second lens group even at
the telephoto end of the zoom lens system. To ensure high zoom
ratios, it is essentially required to make good correction for
various aberrations within each lens group. However, the first lens
group comprises a smaller number of lenses with a large proportion
of the positive power allocated to the rear unit, and so the first
lens group remains undercorrected. To compensate for this, it is
required to use an aspherical surface having negative power that
becomes strong at locations off the axis. In consideration of cost,
it is preferable to use a plastic aspherical lens because a glass
aspherical lens costs much. Since the aspherical surface used is
designed to have negative power at locations off the axis, it is
preferable to make use of positive paraxial power because
fluctuations of focal length with temperature changes can be
mutually compensated for within the single lens, so that the
fluctuations of focal length with temperature can be reduced.
[0027] Preferably, thus constructed zoom lens system should further
meet condition (3) given below.
1<(R.sub.22r+R.sub.23f)/(R.sub.22r-R.sub.23f)<2.5 (3)
[0028] Here R.sub.22r is the image-side radius of curvature of the
lens 2-2 in the second lens group, and R.sub.23f is the object-side
radius of curvature of the lens 2-3 in the second lens group.
[0029] Condition (3) provides a definition of the shape factor of
an air lens formed between the lenses 2-2 and 2-3. When the lower
limit of 1 is not reached, it is required to allow an air space
between the lenses 2-2 and 2-3, thereby preventing their
interference, resulting in an increase in the axial center
thickness of the two lens groups and an increase in the thickness
of the collapsible mount. In turn, this does not only form an
obstacle to size reductions, but also causes the back focus to
become short because the principal point positions of the second
lens group are shifted toward the object side under the refracting
power of the lens 2-2. Exceeding the upper limit of 2.5 to
condition (3) means that the air lens defined between the lenses
2-2 and 2-3 takes a meniscus form having close radii of curvature.
In other words, at a location off the axis of the air lens,
surfaces having close radii of curvature are disposed close to each
other. Consequently, light rays reflected at the object-side
surface of the lens 2-3, and especially at the periphery of that
surface, are reflected at the image-side surface of the lens 2-2.
The thus reflected light rays then arrive at an effective screen,
yielding ghost or flare components that are harmful to images.
[0030] It is here noted that lower and upper limits to condition
(3) may be 1.8 and 2.3, respectively.
[0031] According to another aspect of the present invention, there
is provided a zoom lens system comprising, in order from an object
side of the zoom lens system, a first lens group having positive
refracting power and a second lens group having negative refracting
power, wherein:
[0032] said second lens group comprises, in order from an object
side thereof, a positive lens 2-1, a negative lens 2-2 and a
negative lens 2-3, with said lens 2-1 comprising a plastic lens
element, and
[0033] said second lens group satisfies the following conditions
(1), (2) and (4):
1.05.ltoreq.f.sub.21/f.sub.T<5 (1)
3.8<f.sub.22/f.sub.G2<8 (2)
1.01.ltoreq.S.sub.G21<1.24 (4)
[0034] where f.sub.21 is the focal length of the lens 2-1 in the
second lens group, f.sub.22 is the focal length of the lens 2-2 in
the second lens group, f.sub.T is the focal length of the zoom lens
system at a telephoto end thereof, f.sub.G2 is the composite focal
length of the second lens group, and S.sub.G21 is the specific
gravity of the lens 2-1 in the second lens group.
[0035] According to this aspect, too, the zoom lens system
comprises a first lens group having positive refracting power and a
second lens group having negative refracting power. The second lens
group then comprises a positive lens 2-1, a negative lens 2-2 and a
negative lens 2-3. The positive lens 2-1 is formed of a plastic
lens. This arrangement is of the simplest two-group construction in
zoom lens constructions, and is constructed of the telephoto type
so as to achieve size reductions on the telephoto side. By
providing the diverging second lens group of +-- construction, and
especially allocating the high proportion of negative refracting
power to two lenses, it is possible to reduce the influence of
decentration produced within the second lens group and make
correction for aberrations, especially off-axis coma. By
constructing the positive lens 2-1 of a plastic lens, size and
weight reductions can be achieved.
[0036] Referring here to why the plastic lens is used for the lens
2-1 rather than for the lenses 2-2 and 2-3, the lens 2-1 is only
the positive lens in the second lens group that has generally
negative power, and so can be constructed with a relatively gentle
power. In addition, the lens 2-1 is the outermost lens favorable
for assembly control. For instance, a plastic lens is fabricated by
an injection molding process that does not rely on the centering
step needed for glass lenses. This is favorable in consideration of
cost, but makes the surface of the lens prone to decentration with
respect to the outside shape of the lens. For this reason, it is
desired to control the decentration of the plastic lens during
assembly. The control should then preferably be carried out with
respect to the axes of other lenses forming the same group. This is
the reason that the plastic lens should preferably be disposed at
the outermost position. How to perform this control, for instance,
is set forth JP-A 6-265766.
[0037] Condition (1) provides a definition of the focal length
ratio of the lens 2-1 with respect to the zoom lens system at the
telephoto end. The outermost lens or plastic lens 2-1 varies in
shape and refractive index with temperatures. Such variations occur
largely at the telephoto end of the zoom lens system, and have some
considerable influences on image-formation capabilities and focal
shifts as well. When the lower limit of 1.05 to this condition is
not reached, the focal length of the lens 2-1 becomes short (or the
refracting power thereof increases strong), resulting in
unacceptably large changes of the focal length due to temperature,
etc. When the upper limit of 5 is exceeded, the focal length of the
lens 2-1 becomes too long to make correction for aberrations,
especially chromatic aberrations. This phenomenon becomes
perceptible with increasing zoom ratios.
[0038] It is here noted that the lower and upper limits to
condition (1) may be 1.3 and 3.5, respectively.
[0039] Condition (2) provides a definition of the ratio of the
focal length of the lens 2-2 with respect to the composite focal
length of the second lens group. To satisfy this condition, the
combined negative power of the lenses 2-2 and 2-3 must be stronger
than the overall negative power of the rear lens group (the second
lens group). Basically, positive and negative powers are allocated
to the object and image sides of the second lens group,
respectively, so that the principal points thereof can be
positioned on the object side. By meeting condition (2) in
consideration of such requirements, it is possible to ensure the
preferable positions for the principal points of the second lens
group, and make correction for aberrations of the lens 2-2 in
particular. To be more specific, when the lower limit 3.8 to
condition (2) is not reached, the proportion of the refracting
power of the lens 2-2 in the second lens group becomes large, and
so the principal points of the second lens group are shifted toward
the object side in the second lens group; that is, the second lens
group is as a whole positioned on the image plane side of the zoom
lens system. This makes it difficult to ensure any satisfactory
back focus. The reduced back focus does not only add mechanical
constrains to the zoom lens system but also offers problems such as
lens diameter increases, transfer onto film of dust deposits on
lens surfaces, etc. When the upper limit of 8 is exceeded, the
refracting power of the lens 2-2 becomes too weak to make effective
correction for aberrations.
[0040] It is here noted that the upper and lower limits to
condition (2) may be 5.0 and 7.4, respectively.
[0041] Condition (4) provides a definition of the specific gravity
of the plastic lens 2-1. As already explained, a plastic lens can
contribute to weight reductions because of being smaller in
specific gravity than a glass lens. With size reductions of a
camera, weight reductions of lenses, too, provide effective means
for saving the power and energy of a built-in motor.
[0042] With the second embodiment of the present invention, too, a
compact, low-cost zoom lens system can be achieved by meeting such
requirements as mentioned above.
[0043] Preferably, the front lens unit in the first lens group
should consist of, in order from an object side thereof, a negative
meniscus lens element and a positive meniscus lens element convex
on an object side thereof.
[0044] Preferably, the rear lens unit in the first lens group
should consist of a positive double-convex lens component.
[0045] Preferably, the second lens group should consists of, in
order from an object side thereof, a positive meniscus lens element
concave on an object side thereof, a negative lens element concave
on an object side thereof and a negative meniscus lens element
concave on an object side thereof.
[0046] It is thus possible to construct a high-performance zoom
lens system of a reduced number of lenses.
[0047] Preferably in view of processability and correction of
aberrations, aspherical surfaces should be used at the object-side
surface of the lens component 1-2 in the first lens group and the
object-side surface of the lens component 2-1 in the second lens
group.
[0048] When an aspherical surface is used at the object-side
surface of the lens component 1-2 in the first lens group, it
should preferably have positive power on the optical axis, and be
configured in such a way as to have a point of inflexion on section
including the optical axis.
[0049] Preferably, a stop designed to move together with the first
lens group during zooming should be disposed between the first and
second lens groups.
[0050] Upon zooming from the wide-angle end to the telephoto end of
the zoom lens system, both the first and second lens groups should
preferably move toward the object side of the zoom lens system with
a varying separation between them.
[0051] Of groups comprising lenses, only the first and second lens
groups should preferably move upon zooming from the wide-angle end
to the telephoto end, with a zoom ratio of 2.5 or greater. More
preferably, the zoom ratio should be 3.1 or greater.
[0052] According to a further aspect of the present invention, the
zoom lens system of the present invention may be used as an image
pickup device to construct an image pickup system comprising a
viewing device for viewing an image formed by the zoom lens
system.
[0053] Still other objects and advantages of the invention will in
part be obvious and will in part be apparent from the
specification.
[0054] The invention accordingly comprises the features of
construction, combinations of elements, and arrangement of parts
which will be exemplified in the construction hereinafter set
forth, and the scope of the invention will be indicated in the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIGS. 1(a), 1(b) and 1(c) are sectional views of Example 1
of the zoom lens system according to the invention at a wide angle
end, an intermediate setting and a telephoto end thereof,
respectively.
[0056] FIGS. 2(a), 2(b) and 2(c) are sectional views, similar to
FIGS. 1(a), 1(b) and 1(c), of Example 2 of the zoom lens system
according to the invention.
[0057] FIGS. 3(a), 3(b) and 3(c) are sectional views, similar to
FIGS. 1(a), 1(b) and 1(c), of Example 3 of the zoom lens system
according to the invention.
[0058] FIGS. 4(a), 4(b) and 4(c) are sectional views, similar to
FIGS. 1(a), 1(b) and 1(c), of Example 4 of the zoom lens system
according to the invention.
[0059] FIGS. 5(a), 5(b) and 5(c) are sectional views, similar to
FIGS. 1(a), 1(b) and 1(c), of Example 5 of the zoom lens system
according to the invention.
[0060] FIGS. 6(a), 6(b) and 6(c) are aberration diagrams for
Example 1 upon focused at infinity.
[0061] FIGS. 7(a), 7(b) and 7(c) are aberration diagrams for
Example 2 upon focused at infinity.
[0062] FIGS. 8(a), 8(b) and 8(c) are aberration diagrams for
Example 3 upon focused at infinity.
[0063] FIGS. 9(a), 9(b) and 9(c) are aberration diagrams for
Example 4 upon focused at infinity.
[0064] FIGS. 10(a), 10(b) and 10(c) are aberration diagrams for
Example 5 upon focused at infinity.
[0065] FIGS. 11(a), 11(b) and 11(c) are aberration diagrams for
Example 6 upon focused at infinity.
[0066] FIGS. 12(a), 12(b) and 12(c) are aberration diagrams for
Example 7 upon focused at infinity.
[0067] FIGS. 13(a), 13(b) and 13(c) are aberration diagrams for
Example 8 upon focused at infinity.
[0068] FIGS. 14(a), 14(b) and 14(c) are aberration diagrams for
Example 9 upon focused at infinity.
[0069] FIG. 15 is a perspective view illustrative of one
construction of the compact camera with which the zoom lens system
of the invention is used.
[0070] FIG. 16 is a sectional schematic illustrative of the
construction of the compact camera of FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] The zoom lens system of the present invention is now
explained with reference to Examples 1 to 9. FIGS. 1(a), 1(b) and
1(c) through 5(a), 5(b) and 5(c) are sectional views of the lens
arrangements of Examples 1 to 5 at the wide-angle ends,
intermediate settings and telephoto ends thereof, respectively. It
is noted that sectional views of the lens arrangements of Examples
6 to 9 are omitted, and numerical data on each example will be
enumerated later.
EXAMPLE 1
[0072] This example is directed to a zoom lens system having a
focal length of 39.33 to 115.80 mm and an F-number of 3.80 to
11.18. As shown in FIGS. 1(a) to l(c), the zoom lens system is
composed of a first lens group G1 having positive refracting power
and a second lens group G2 having negative refracting power. From
the wide-angle end to the telephoto end of the zoom lens system,
the first lens group G1, and the second lens group G2 moves toward
the object side of the zoom lens system while the space between
them becomes narrow.
[0073] The first lens group G1 is made up of a front lens unit G1f
consisting of a negative meniscus lens convex on an object side
thereof and a positive meniscus lens convex on an object side
thereof, a rear lens unit G1r composed of a doublet consisting of a
negative meniscus lens convex on an object side thereof and a
double-convex lens, and an aperture stop. The second lens group G2
is made up of a positive meniscus lens, a negative meniscus lens
and a negative meniscus lens, each concave on an object side
thereof. Two aspherical surfaces are used; one at the object-side
surface of the positive meniscus lens in the front lens unit G1f in
the first lens group G1, and another at the object-side surface of
the positive meniscus lens in the second lens group G2.
EXAMPLE 2
[0074] This example is directed to a zoom lens system having a
focal length of 39.34 to 110.45 mm and an F-number of 4.14 to
11.63. As shown in FIGS. 2(a) to 2(c), the zoom lens system is
composed of a first lens group Gl having positive refracting power
and a second lens group G2 having negative refracting power. From
the wide-angle end to the telephoto end of the zoom lens system,
the first lens group G1, and the second lens group G2 moves toward
the object side of the zoom lens system while the space between
them becomes narrow.
[0075] The first lens group G1 is made up of a front lens unit G1f
consisting of a negative meniscus lens convex on an object side
thereof and a positive meniscus lens convex on an object side
thereof, a rear lens unit G1r composed of a double-convex lens, and
an aperture stop. The second lens group G2 is made up of a positive
meniscus lens, a negative meniscus lens and a negative meniscus
lens, each concave on an object side thereof. Two aspherical
surfaces are used; one at the object-side surface of the-positive
meniscus lens in the front lens unit G1f in the first lens group
G1, and another at the object-side surface of the positive meniscus
lens in the second lens group G2.
EXAMPLE 3
[0076] This example is directed to a zoom lens system having a
focal length of 39.33 to 115.83 mm and an F-number of 3.81 to
11.22. As shown in FIGS. 3(a) to 3(c), the zoom lens system is
composed of a first lens group G1 having positive refracting power
and a second lens group G2 having negative refracting power. From
the wide-angle end to the telephoto end of the zoom lens system,
the first lens group G1, and the second lens group G2 moves toward
the object side of the zoom lens system while the space between
them becomes narrow.
[0077] The first lens group Gl is made up of a front lens unit G1f
consisting of a negative meniscus lens concave on an object side
thereof and a positive meniscus lens convex on an object side
thereof, a rear lens unit G1r composed of a doublet consisting of a
negative meniscus lens convex on an object side thereof and a
double-convex lens, and an aperture stop. The second lens group G2
is made up of a positive meniscus lens, a negative meniscus lens
and a negative meniscus lens, each concave on an object side
thereof. Two aspherical surfaces are used; one at the object-side
surface of the positive meniscus lens in the front lens unit G1f in
the first lens group G1, and another at the object-side surface of
the positive meniscus lens in the second lens group G2.
EXAMPLE 4
[0078] This example is directed to a zoom lens system having a
focal length of 36.17 to 103.49 mm and an F-number of 3.97 to
11.35. As shown in FIGS. 4(a) to 4(c), the zoom lens system is
composed of a first lens group G1having positive refracting power
and a second lens group G2 having negative refracting power. From
the wide-angle end to the telephoto end of the zoom lens system,
the first lens group G1, and the second lens group G2 moves toward
the object side of the zoom lens system while the space between
them becomes narrow.
[0079] The first lens group G1 is made up of a front lens unit G1f
consisting of a negative meniscus lens concave on an object side
thereof and a positive meniscus lens convex on an object side
thereof, a rear lens unit G1r composed of a doublet consisting of a
negative meniscus lens convex on an object side thereof and a
double-convex lens, and an aperture stop. The second lens group G2
is made up of a positive meniscus lens, a negative meniscus lens
and a negative meniscus lens, each concave on an object side
thereof. Two aspherical surfaces are used; one at the object-side
surface of the positive meniscus lens in the front lens unit G1f in
the first lens group G1, and another at the object-side surface of
the positive meniscus lens in the second lens group G2.
EXAMPLE 5
[0080] This example is directed to a zoom lens system having a
focal length of 36.16 to 107.97 mm and an F-number of 3.80 to
11.35. As shown in FIGS. 5(a) to 5(c), the zoom lens system is
composed of a first lens group G1 having positive refracting power
and a second lens group G2 having negative refracting power. From
the wide-angle end to the telephoto end of the zoom lens system,
the first lens group G1, and the second lens group G2 moves toward
the object side of the zoom lens system while the space between
them becomes narrow.
[0081] The first lens group G1 is made up of a front lens unit G1f
consisting of a negative meniscus lens concave on an object side
thereof and a positive meniscus lens convex on an object side
thereof, a rear lens unit G1r composed of a doublet consisting of a
negative meniscus lens convex on an object side thereof and a
double-convex lens, and an aperture stop. The second lens group G2
is made up of a positive meniscus lens, a negative meniscus lens
and a negative meniscus lens, each concave on an object side
thereof. Two aspherical surfaces are used; one at the object-side
surface of the positive meniscus lens in the front lens unit G1f in
the first lens group G1, and another at the object-side surface of
the positive meniscus lens in the second lens group G2.
EXAMPLE 6
[0082] The instant example is directed to a zoom lens system having
a focal length of 39.33 to 148.37 mm and an F-number of 3.80 to
14.32. In the zoom lens system of this example, the space between
the lens groups at the telephoto end of Example 1 is made narrow to
extend the telephoto end. The power profile, direction of movement,
and lens arrangement, of each lens group are the same as in Example
1, and so are not shown.
EXAMPLE 7
[0083] The instant example is directed to a zoom lens system having
a focal length of 39.33 to 144.50 mm and an F-number of 3.81 to
14.00. In the zoom lens system of this example, the space between
the lens groups at the telephoto end of Example 3 is made narrow to
extend the telephoto end. The power profile, direction of movement,
and lens arrangement, of each lens group are the same as in Example
3, and so are not shown.
EXAMPLE 8
[0084] The instant example is directed to a zoom lens system having
a focal length of 36.17 to 126.19 mm and an F-number of 3.97 to
16.00. In the zoom lens system of this example, the space between
the lens groups at the telephoto end of Example 4 is made narrow to
extend the telephoto end. The power profile, direction of movement,
and lens arrangement, of each lens group are the same as in Example
4, and so are not shown.
EXAMPLE 9
[0085] The instant example is directed to a zoom lens system having
a focal length of 36.16 to 126.35 mm and an F-number of 3.80 to
16.00. In the zoom lens system of this example, the space between
the lens groups at the telephoto end of Example 5 is made narrow to
extend the telephoto end. The power profile, direction of movement,
and lens arrangement, of each lens group are the same as in Example
5, and so are not shown.
[0086] Set out below are the numerical data on each example. The
symbols used hereinafter but not hereinbefore have the following
meanings.
[0087] f: the focal length of the zoom lens system,
[0088] FNO: F-number,
[0089] 2.omega.: field angle,
[0090] FB: back focus,
[0091] WE: wide-angle end,
[0092] ST: intermediate settings,
[0093] TE: telephoto end,
[0094] r.sub.1, r.sub.2, the radius of curvature of each lens
surface,
[0095] d.sub.1, d.sub.2, the space between adjacent lens
surfaces,
[0096] n.sub.d1, n.sub.d2, the d-line refractive index of each
lens, and
[0097] .nu..sub.d1, .nu..sub.d2, the Abbe number of each lens.
[0098] Length is given in mm. Here let x represent an optical axis
where the propagation direction of light is positive and y
represent a direction perpendicular to the optical axis. Then, the
shape of an aspherical surface is given by
x=(y.sup.2/r)/[1+{1-(K+1)(y/r).sup.2}.sup.1/2]+A.sub.4y.sup.4+A.sub.6y.sup-
.6+A.sub.8y.sup.8+A.sub.10y.sup.10+A.sub.12y.sup.12
[0099] Here r is a paraxial radius of curvature, K is a conical
coefficient, and A4, A6, A8, A10 and A12 are the fourth, sixth,
eighth, tenth and twelfth aspherical coefficients.
EXAMPLE 1
[0100]
1 r.sub.1 = 229.62 d.sub.1 = 1.30 n.sub.d1 = 1.7283 v.sub.d1 =
28.46 r.sub.2 = 46.52 d.sub.2 = 1.00 r.sub.3 = 28.44(Aspheric)
d.sub.3 = 2.30 n.sub.d2 = 1.5254 v.sub.d2 = 55.78 r.sub.4 = 30.39
d.sub.4 = 7.04 r.sub.5 = 32.03 d.sub.5 = 1.02 n.sub.d3 = 1.7859
v.sub.d3 = 44.20 r.sub.6 = 14.71 d.sub.6 = 4.72 n.sub.d4 = 1.5225
v.sub.d4 = 59.84 r.sub.7 = -14.71 d.sub.7 = 1.20 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -78.84(Aspheric) d.sub.9 = 2.52
n.sub.d5 = 1.5254 v.sub.d5 = 55.78 r.sub.10 = -40.65 d.sub.10 =
2.98 r.sub.11 = -23.75 d.sub.11 = 1.38 n.sub.d6 = 1.4875 v.sub.d6 =
70.23 r.sub.12 = -38.04 d.sub.12 = 4.65 r.sub.13 = -12.61 d.sub.13
= 1.71 n.sub.d7 = 1.6968 v.sub.d7 = 55.53 r.sub.14 = -50.89
Aspherical Coefficients 3rd surface K = 6.5028 A.sub.4 = -1.1286
.times. 10.sup.-4 A.sub.6 = -9.3251 .times. 10.sup.-7 A.sub.8 =
3.6782 .times. 10.sup.-9 A.sub.10 = -7.3820 .times. 10.sup.-11
A.sub.12 = 0 9th surface K = 11.0944 A.sub.4 = 3.4281 .times.
10.sup.-5 A.sub.6 = 3.3435 .times. 10.sup.-7 A.sub.8 = -1.8047
.times. 10.sup.-10 A.sub.10 = -1.8363 .times. 10.sup.-11 A.sub.12 =
1.2456 .times. 10.sup.-13 Zooming Data WE ST TE f 39.33 67.19
115.80 F.sub.NO 3.80 6.48 11.18 2 .omega. (.degree. ) 56.24 35.26
21.08 F B 6.99 29.83 69.67 D 1 14.16 6.96 2.69
EXAMPLE 2
[0101]
2 r.sub.1 = 250.00 d.sub.1 = 1.30 n.sub.d1 = 1.7847 v.sub.d1 =
25.68 r.sub.2 = 48.65 d.sub.2 = 1.50 r.sub.3 = 26.88(Aspheric)
d.sub.3 = 2.30 n.sub.d2 = 1.5254 v.sub.d2 = 55.80 r.sub.4 = 28.89
d.sub.4 = 5.21 r.sub.5 = 194.61 d.sub.5 = 3.50 n.sub.d3 = 1.4875
v.sub.d3 = 70.23 r.sub.6 = -12.35 d.sub.6 = 1.20 r.sub.7 = .infin.
(Stop) D.sub.7 = D1 r.sub.8 = -28.59(Aspheric) d.sub.8 = 2.52
n.sub.d4 = 1.5254 v.sub.d4 = 55.80 r.sub.9 = -20.13 d.sub.9 = 2.52
r.sub.10 = -18.16 d.sub.10 = 1.38 n.sub.d5 = 1.4875 v.sub.d5 =
70.23 r.sub.11 = -28.62 d.sub.11 = 3.80 r.sub.12 = -12.11 d.sub.12
= 1.71 n.sub.d6 = 1.6968 v.sub.d6 = 55.53 r.sub.13 = -31.51
Aspherical Coefficients 3rd surface K = 6.7270 A.sub.4 = -1.6855
.times. 10.sup.-4 A.sub.6 = -1.0574 .times. 10.sup.-6 A.sub.8 =
-9.4838 .times. 10.sup.-9 A.sub.10 = -7.2298 .times. 10.sup.-11
A.sub.12 = 0 8th surface K = 7.4399 A.sub.4 = 7.9041 .times.
10.sup.-6 A.sub.6 = 4.5234 .times. 10.sup.-7 A.sub.8 = -1.7238
.times. 10.sup.-10 A.sub.10 = 6.0203 .times. 10.sup.-11 A.sub.12 =
-3.1965 .times. 10.sup.-14 Zooming Data WE ST TE f 39.34 67.88
110.45 F.sub.NO 4.14 7.12 11.63 2 .omega. (.degree. ) 56.22 35.27
22.17 F B 6.85 33.37 72.45 D 1 16.40 7.77 3.19
EXAMPLE 3
[0102]
3 r.sub.1 = -30.00 d.sub.1 = 1.30 n.sub.d1 = 1.6668 v.sub.d1 =
33.05 r.sub.2 = -69.52 d.sub.2 = 1.20 r.sub.3 = 81.83(Aspheric)
d.sub.3 = 2.30 n.sub.d2 = 1.5842 v.sub.d2 = 30.49 r.sub.4 = 136.38
d.sub.4 = 5.61 r.sub.5 = 31.24 d.sub.5 = 1.04 n.sub.d3 = 1.8340
v.sub.d3 = 37.16 r.sub.6 = 16.00 d.sub.6 = 4.57 n.sub.d4 = 1.5182
v.sub.d4 = 58.90 r.sub.7 = -15.92 d.sub.7 = 1.00 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -90.30(Aspheric) d.sub.9 = 2.52
n.sub.d5 = 1.5842 v.sub.d5 = 30.49 r.sub.10 = -50.33 d.sub.10 =
3.85 r.sub.11 = -90.16 d.sub.11 = 1.38 n.sub.d6 = 1.6516 v.sub.d6 =
58.55 r.sub.12 = -403.64 d.sub.12 = 4.45 r.sub.13 = -14.12 d.sub.13
= 1.67 n.sub.d7 = 1.7292 v.sub.d7 = 54.68 r.sub.14 = -67.39
Aspherical Coefficients 3rd surface K = 7.5594 A.sub.4 = -5.6772
.times. 10.sup.-5 A.sub.6 = -5.2870 .times. 10.sup.-7 A.sub.8 =
7.1209 .times. 10.sup.-9 A.sub.10 = -8.5759 .times. 10.sup.-10
A.sub.12 = 0 9th surface K = 8.3394 A.sub.4 = 1.7453 .times.
10.sup.-5 A.sub.6 = 9.9323 .times. 10.sup.-8 A.sub.8 = -2.4666
.times. 10.sup.-10 A.sub.10 = 3.4004 .times. 10.sup.-11 A.sub.12 =
-3.6578 .times. 10.sup.-13 Zooming Data WE ST TE f 39.33 67.56
115.83 F.sub.NO 3.81 6.54 11.22 2 .omega. (.degree. ) 56.24 35.01
21.06 F B 6.99 30.59 70.95 D 1 14.49 6.66 2.11
EXAMPLE 4
[0103]
4 r.sub.1 = -31.53 d.sub.1 = 1.10 n.sub.d1 = 1.6668 v.sub.d1 =
33.05 r.sub.2 = -77.84 d.sub.2 = 1.10 r.sub.3 = 106.56(Aspheric)
d.sub.3 = 2.05 n.sub.d2 = 1.5254 v.sub.d2 = 55.81 r.sub.4 = 122.04
d.sub.4 = 5.00 r.sub.5 = 33.95 d.sub.5 = 0.92 n.sub.d3 = 1.8340
v.sub.d3 = 37.16 r.sub.6 = 17.48 d.sub.6 = 3.77 n.sub.d4 = 1.5182
v.sub.d4 = 58.90 r.sub.7 = -14.24 d.sub.7 = 1.00 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -29.68(Aspheric) d.sub.9 = 2.35
n.sub.d5 = 1.5254 v.sub.d5 = 55.81 r.sub.10 = -27.39 d.sub.10 =
5.04 r.sub.11 = -26.39 d.sub.11 = 1.31 n.sub.d6 = 1.5163 v.sub.d6 =
64.14 r.sub.12 = -37.75 d.sub.12 = 3.75 r.sub.13 = -14.50 d.sub.13
= 1.62 n.sub.d7 = 1.7292 v.sub.d7 = 54.68 r.sub.14 = -54.38
Aspherical Coefficients 3rd surface K = 7.5594 A.sub.4 = -9.1595
.times. 10.sup.-5 A.sub.6 = -9.1569 .times. 10.sup.-7 A.sub.8 =
1.7094 .times. 10.sup.-8 A.sub.10 = -2.5636 .times. 10.sup.-10
A.sub.12 = 0 9th surface K = 8.3392 A.sub.4 = 6.5726 .times.
10.sup.-5 A.sub.6 = 1.7278 .times. 10.sup.-7 A.sub.8 = -2.4038
.times. 10.sup.-10 A.sub.10 = 1.1693 .times. 10.sup.-10 A.sub.12 =
-4.6672 .times. 10.sup.-13 Zooming Data WE ST TE f 36.17 67.35
103.49 F.sub.NO 3.97 7.39 11.35 2 .omega. (.degree. ) 60.27 35.23
23.52 F B 4.39 30.93 61.68 D 1 15.50 6.84 3.33
EXAMPLE 5
[0104]
5 r.sub.1 = -22.77 d.sub.1 = 1.10 n.sub.d1 = 1.7408 v.sub.d1 =
27.79 r.sub.2 = -37.64 d.sub.2 = 1.10 r.sub.3 = 110.92(Aspheric)
d.sub.3 = 2.05 n.sub.d2 = 1.5254 v.sub.d2 = 55.81 r.sub.4 = 229.11
d.sub.4 = 4.00 r.sub.5 = 62.19 d.sub.5 = 0.79 n.sub.d3 = 1.8340
v.sub.d3 = 37.16 r.sub.6 = 27.86 d.sub.6 = 3.45 n.sub.d4 = 1.5182
v.sub.d4 = 58.90 r.sub.7 = -13.43 d.sub.7 = 1.00 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -32.02(Aspheric) d.sub.9 = 2.35
n.sub.d5 = 1.5254 v.sub.d5 = 55.81 r.sub.10 = -28.02 d.sub.10 =
4.28 r.sub.11 = -26.05 d.sub.11 = 1.31 n.sub.d6 = 1.5163 v.sub.d6 =
64.14 r.sub.12 = -37.64 d.sub.12 = 3.75 r.sub.13 = -14.50 d.sub.13
= 1.62 n.sub.d7 = 1.7292 v.sub.d7 = 54.68 r.sub.14 = -61.14 3.89
Aspherical Coefficients 3rd surface K = 7.5594 A.sub.4 = -1.0371
.times. 10.sup.-4 A.sub.6 = -7.8770 .times. 10.sup.-7 A.sub.8 =
1.1867 .times. 10.sup.-8 A.sub.10 = -2.4625 .times. 10.sup.-10
A.sub.12 = 0 9th surface K = 8.3393 A.sub.4 = 6.1247 .times.
10.sup.-5 A.sub.6 = 4.2495 .times. 10.sup.-8 A.sub.8 = -2.4386
.times. 10.sup.-10 A.sub.10 = 1.1753 .times. 10.sup.-10 A.sub.12 =
-7.7475 .times. 10.sup.-13 Zooming Data WE ST TE f 36.16 67.41
107.97 F.sub.NO 3.80 7.09 11.35 2 .omega. (.degree. ) 60.05 35.01
22.52 F B 3.89 29.50 62.74 D 1 17.00 8.31 4.53
EXAMPLE 6
[0105]
6 r.sub.1 = 229.62 r.sub.1 = 1.30 n.sub.d1 = 1.7283 v.sub.d1 =
28.46 r.sub.2 = 46.52 d.sub.2 = 1.00 r.sub.3 = 28.44(Aspheric)
d.sub.3 = 2.30 n.sub.d2 = 1.5254 v.sub.d2 = 55.78 r.sub.4 = 30.39
d.sub.4 = 7.04 r.sub.5 = 32.03 r.sub.5 = 1.02 n.sub.d3 = 1.7859
v.sub.d3 = 44.20 r.sub.6 = 14.71 d.sub.6 = 4.72 n.sub.d4 = 1.5225
v.sub.d4 = 59.84 r.sub.7 = -14.71 d.sub.7 = 1.20 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -78.84(Aspheric) d.sub.9 = 2.52
n.sub.d5 = 1.5254 v.sub.d5 = 55.78 r.sub.10 = -40.65 d.sub.10 =
2.98 r.sub.11 = -23.75 d.sub.11 = 1.38 n.sub.d6 = 1.4875 v.sub.d6 =
70.23 r.sub.12 = -38.04 d.sub.12 = 4.65 r.sub.13 = -12.61 d.sub.13
= 1.71 n.sub.d7 = 1.6968 v.sub.d7 = 55.53 r.sub.14 = -50.89
Aspherical Coefficients 3rd surface K = 6.5028 A.sub.4 = -1.1286
.times. 10.sup.-4 A.sub.6 = -9.3251 .times. 10.sup.-7 A.sub.8 =
3.6782 .times. 10.sup.-9 A.sub.10 = -7.3820 .times. 10.sup.-11
A.sub.12 = 0 9th surface K = 11.0944 A.sub.4 = 3.4281 .times.
10.sup.-5 A.sub.6 = 3.3435 .times. 10.sup.-7 A.sub.8 = -1.8047
.times. 10.sup.-10 A.sub.10 = -1.8363 .times. 10.sup.-11 A.sub.12 =
1.2456 .times. 10.sup.-13 Zooming Data WE ST TE f 39.33 67.19
148.37 F.sub.NO 3.80 6.48 14.32 2 .omega. (.degree. ) 56.24 35.26
16.55 F B 6.99 29.83 96.37 D 1 14.16 6.96 1.40
EXAMPLE 7
[0106]
7 r.sub.1 = -30.00 d.sub.1 = 1.30 n.sub.d1 = 1.6668 v.sub.d1 =
33.05 r.sub.2 = -69.52 d.sub.2 = 1.20 r.sub.3 = 81.83(Aspheric)
d.sub.3 = 2.30 n.sub.d2 = 1.5842 v.sub.d2 = 30.49 r.sub.4 = 136.38
d.sub.4 = 5.61 r.sub.5 = 31.24 d.sub.5 = 1.04 n.sub.d3 = 1.8340
v.sub.d3 = 37.16 r.sub.6 = 16.00 d.sub.6 = 4.57 n.sub.d4 = 1.5182
v.sub.d4 = 58.90 r.sub.7 = -15.92 d.sub.7 = 1.00 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -90.30(Aspheric) d.sub.9 = 2.52
n.sub.d5 = 1.5842 v.sub.d5 = 30.49 r.sub.10 = -50.33 d.sub.10 =
3.85 r.sub.11 = -90.16 d.sub.11 = 1.38 n.sub.d6 = 1.6516 v.sub.d6 =
58.55 r.sub.12 = -403.64 d.sub.12 = 4.45 r.sub.13 = -14.12 d.sub.13
= 1.67 n.sub.d7 = 1.7292 v.sub.d7 = 54.68 r.sub.14 = -67.39
Aspherical Coefficients 3rd surface K = 7.5594 A.sub.4 = -5.6772
.times. 10.sup.-5 A.sub.6 = -5.2870 .times. 10.sup.-7 A.sub.8 =
7.1209 .times. 10.sup.-9 A.sub.10 = -8.5759 .times. 10.sup.-11
A.sub.12 = 0 9th surface K = 8.3394 A.sub.4 = 1.7453 .times.
10.sup.-5 A.sub.6 = 9.9323 .times. 10.sup.-8 A.sub.8 = -2.4666
.times. 10.sup.-10 A.sub.10 = 3.4004 .times. 10.sup.-11 A.sub.12 =
-3.6578 .times. 10.sup.-13 Zooming Data WE ST TE f 39.33 67.56
144.50 F.sub.NO 3.81 6.54 14.00 2 .omega. (.degree. ) 56.24 35.01
16.98 F B 6.99 30.59 94.93 D 1 14.49 6.66 0.85
EXAMPLE 8
[0107]
8 r.sub.1 = -31.53 d.sub.1 = 1.10 n.sub.d1 = 1.6668 v.sub.d1 =
33.05 r.sub.2 = -77.84 d.sub.2 = 1.10 r.sub.3 = 106.56(Aspheric)
d.sub.3 = 2.05 n.sub.d2 = 1.5254 v.sub.d2 = 55.81 r.sub.4 = 122.04
d.sub.4 = 5.00 r.sub.5 = 33.95 d.sub.5 = 0.92 n.sub.d5 = 1.8340
v.sub.d3 = 37.16 r.sub.6 = 17.48 d.sub.6 = 3.77 n.sub.d4 = 1.5182
v.sub.d4 = 58.90 r.sub.7 = -14.24 d.sub.7 = 1.00 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -29.68(Aspheric) d.sub.9 = 2.35
n.sub.d5 = 1.5254 v.sub.d5 = 55.81 r.sub.10 = -27.39 d.sub.10 =
5.04 r.sub.11 = -26.39 d.sub.11 = 1.31 n.sub.d6 = 1.5163 v.sub.d6 =
64.14 r.sub.12 = -37.75 d.sub.12 = 3.75 r.sub.13 = -14.50 d.sub.13
= 1.62 n.sub.d7 = 1.7292 v.sub.d7 = 54.68 r.sub.14 = -54.38
Aspherical Coefficients 3rd surface K = 7.5594 A.sub.4 = -9.1595
.times. 10.sup.-5 A.sub.6 = -9.1569 .times. 10.sup.-7 A.sub.8 =
1.7094 .times. 10.sup.-8 A.sub.10 = -2.5636 .times. 10.sup.-10
A.sub.12 = 0 9th surface K = 8.3392 A.sub.4 = 6.5726 .times.
10.sup.-5 A.sub.6 = 1.7278 .times. 10.sup.-7 A.sub.8 = -2.4038
.times. 10.sup.-10 A.sub.10 = 1.1693 .times. 10.sup.-10 A.sub.12 =
-4.6672 .times. 10.sup.-13 Zooming Data WE ST TE f 36.17 67.35
126.19 F.sub.NO 3.97 7.80 16.00 2 .omega. (.degree. ) 60.27 35.23
19.40 F B 4.39 30.93 81.00 D 1 15.50 6.84 2.15
EXAMPLE 9
[0108]
9 r.sub.1 = -22.77 d.sub.1 = 1.10 n.sub.d1 = 1.7408 v.sub.d1 =
27.79 r.sub.2 = -37.64 d.sub.2 = 1.10 r.sub.3 = 110.92(Aspheric)
d.sub.3 = 2.05 n.sub.d2 = 1.5254 v.sub.d2 = 55.81 r.sub.4 = 229.11
d.sub.4 = 4.00 r.sub.5 = 62.19 d.sub.5 = 0.79 n.sub.d3 = 1.8340
v.sub.d3 = 37.16 r.sub.6 = 27.86 d.sub.6 = 3.45 n.sub.d4 = 1.5182
v.sub.d4 = 58.90 r.sub.7 = -13.43 d.sub.7 = 1.00 r.sub.8 = .infin.
(Stop) d.sub.8 = D1 r.sub.9 = -32.02(Aspheric) d.sub.9 = 2.35
n.sub.d5 = 1.5254 v.sub.d5 = 55.81 r.sub.10 = -28.02 d.sub.10 =
4.28 r.sub.11 = -26.05 d.sub.11 = 1.31 n.sub.d6 = 1.5163 v.sub.d6 =
64.14 r.sub.12 = -37.64 d.sub.12 = 3.75 r.sub.13 = -14.50 d.sub.12
= 1.62 n.sub.d7 = 1.7292 v.sub.d7 = 54.68 r.sub.14 = -61.14
Aspherical Coefficients 3rd surface K = 7.5594 A.sub.4 = -1.0371
.times. 10.sup.-4 A.sub.6 = -7.8770 .times. 10.sup.-7 A.sub.8 =
1.1867 .times. 10.sup.-8 A.sub.10 = -2.4625 .times. 10.sup.-10
A.sub.12 = 0 9th surface K = 8.3393 A.sub.4 = 6.1247 .times.
10.sup.-5 A.sub.6 = 4.2495 .times. 10.sup.-8 A.sub.8 = -2.4386
.times. 10.sup.-10 A.sub.10 = 1.1753 .times. 10.sup.-10 A.sub.12 =
-7.7475 .times. 10.sup.-13 Zooming Data WE ST TE f 36.16 67.41
126.35 F.sub.NO 3.80 7.80 16.00 2 .omega. (.degree. ) 60.05 35.01
19.34 F B 3.89 29.50 77.79 D 1 17.00 8.31 3.62
[0109] FIGS. 6(a), 6(b) and 6(c) through 14(a), 14(b) and 14(c) are
aberration diagrams for Examples 1 through 9 upon focused at
infinity. In these figures, (a), (b) and (c) show aberrations at
the wide-angle ends, intermediate settings, and telephoto ends,
respectively, and SA, AS, DT, CC and FIY represent spherical
aberrations, astigmatism, distortion, chromatic aberrations of
magnification, and image height, respectively.
[0110] Enumerated below are the values of conditions (1) to (4) and
zoom ratios in Examples 1 to 9.
10 Condition (1) (2) (3) (4) Zoom Ratio Example 1 1.35 5.66 1.99
1.01 2.94 Example 2 1.06 3.86 2.47 1.01 2.81 Example 3 1.64 7.19
1.07 1.2 2.95 Example 4 4.82 7.37 2.25 1.01 2.86 Example 5 3.28
7.23 2.25 1.01 2.99 Example 6 1.05 5.66 1.99 1.01 3.77 Example 7
1.32 7.19 1.07 1.2 3.67 Example 8 3.95 7.37 2.25 1.01 3.49 Example
9 2.81 7.23 2.25 1.01 3.49
[0111] Such a zoom lens as described above may be used as a
phototaking objective lens a for a compact camera, one example of
which is shown in the perspective view of FIG. 15 and the sectional
view of FIG. 16, wherein G1 is the first lens group having positive
refracting power and G2 is the second lens group having negative
refracting power. In FIG. 15 and 16, L.sub.b and L.sub.e stand for
a phototaking optical path and a finder optical path, respectively.
The phototaking optical path L.sub.b is parallel to the finder
optical path L.sub.e. A subject image is observed through a finder
comprising a finder objective, an image erecting prism, a stop and
an eyepiece, and is formed on film via the phototaking objective
lens a.
[0112] The zoom lens of the present invention may also be used as a
phototaking objective lens for a compact electronic camera wherein
an electronic image pickup device such as a CCD is used in place of
film.
[0113] As detailed above and as can be seen from each example, the
present invention can provide a compact, low-cost zoom lens system
comprising a positive lens group and a negative lens group, wherein
a plastic lens is used.
* * * * *