Zoom lens

This specification discloses a zoom lens which has, in succession from the object side, a first lens unit of positive refractive power, a second lens unit having negative refractive power and movable during a focal length change, a third lens unit for correcting the changing of an image plane resulting from the movement of the second lens unit, and a fixed fourth lens unit having positive refractive power, and in which an aspherical surface of a predetermined shape for correcting well spherical aberration and distortion resulting from a focal length change is provided on a predetermined lens surface in the first lens unit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a zoom lens, and particularly to a zoom lens 
suitable for a television camera, a phototaking camera, or a video camera, 
in which an aspherical surface is appropriately used in a portion of a 
lens system, whereby the zoom lens has good optical performance over an 
entire variable power range and has as large an aperture as the F-number 
of the order of 1.7 at the wide angle end and moreover a wide angle (a 
wide angle end angle of view 2.omega.=58.degree.-70.degree.) and as high a 
variable power ratio as a variable power ratio of the order of 12-35. 
2. Related Background Art 
Zoom lenses having a large aperture and high variable power and moreover 
having high optical performance have heretofore been required of 
television cameras, phototaking cameras and video cameras. 
In addition, particularly in color television cameras for broadcasting, 
importance has been attached to operability and mobility and in compliance 
with these requirements, a compact CCD (solid state image pickup element) 
of 2/3 inch or 1/2 inch has become the mainstream as an image pickup 
device. 
This CCD has its entire image pickup range having substantially uniform 
resolving power and therefore, for a zoom lens using it, it is required 
that the resolving power be substantially uniform from the center of the 
image field to the periphery of the image field. 
For example, it is required that various aberrations such as astigmatism, 
distortion and chromatic difference of magnification be corrected well and 
the entire image field have high optical performance. Further, it is 
desired that the zoom lens have a large aperture, a wide angle and a high 
variable power ratio and moreover be compact and light in weight, and have 
a long back focus because a color resolving optical system and various 
kinds of filters are disposed forwardly of image pickup means. 
Among zoom lenses, a so-called four-unit zoom lens comprising, in 
succession from the object side, four lens units, i.e., a first lens unit 
of positive refractive power for focusing, a second lens unit of negative 
refractive power for focal length change, a third lens unit of positive or 
negative refractive power for correcting the image place changing with a 
focal length change, and a fourth lens unit of positive refractive power 
for imaging can be relatively easily made to have a high variable power 
ratio and a large aperture and therefore is often used as a zoom lens for 
a color television camera for broadcasting. 
Of four-unit zoom lenses, a four-unit zoom lens having a great aperture 
ratio and high variable power in which F-number is of the order of 1.6-1.9 
and the variable power ratio is of the order of 13 is proposed, for 
example, in Japanese Laid-Open Patent Application No. 54-127322. 
In a zoom lens, to obtain a great aperture ratio (F-number 1.7-1.8) and a 
high variable power ratio (variable power ratio 12-35) and a wide angle (a 
wide angle end angle of view 2.omega.=58.degree.-70.degree.) and moreover, 
high optical performance over the entire variable power range, it is 
necessary to set the refractive power and lens construction of each lens 
unit appropriately. 
Generally, to have a small aberration fluctuation over the entire variable 
power range and obtain high optical performance, it becomes necessary to 
increase, for example, the number of lenses in each lens unit to thereby 
increase the degree of freedom of design in aberration correction. 
Therefore, if an attempt is made to achieve a zoom lens having a great 
aperture ratio, a wide angle and a high variable power ratio, there 
unavoidably arises the problem that the number of lenses is increased and 
the entire lens system becomes bulky, and the desire for compactness and 
lighter weigh cannot be met. 
Also, regarding the imaging performance, firstly, the changing of the point 
at the center of the image field whereat the image contrast is best, i.e., 
the so-called best image plane, resulting from a focal length change poses 
a problem. This is attributable chiefly to the changing of spherical 
aberration resulting from a focal length change. This spherical aberration 
influences by the cube of the aperture in the area of third-order 
aberration coefficient and therefore, is the greatest problem against a 
larger aperture. 
Generally, the changing of spherical aberration resulting from a focal 
length change, when the zoom ratio is Z and the focal length of the wide 
angle end is fw, tends to become under (minus) relative to the Gaussian 
image plane from the wide angle end at which spherical aberration is 0 to 
the vicinity of a zoom position fm=fw.times.Z.sup.1/4, as shown in FIG. 33 
of the accompanying drawings. When the vicinity of the zoom position 
fm=fw.times.Z.sup.1/4 is passed, the under amount becomes small and at a 
certain zoom position, it becomes 0 and now tends to become over (plus). 
In the foregoing, fw is the focal length of the wide angle end, and Z is a 
zoom ratio. 
The changing of spherical aberration becomes most over (plus) near a zoom 
position fd=(Fno. w/Fno. t).times.ft at which F drop in which F-number 
becomes great (the lens system becomes dark) begins, and when this zoom 
position is passed, the over amount becomes small to the telephoto end, 
and becomes nearly 0 at the telephoto end. 
In the foregoing, Fno. w and Fno. t are F-numbers at the wide angle end and 
the telephoto end, respectively, and ft is the focal length of the 
telephoto end. 
As described above, particularly in a zoom lens having a position at which 
F drop begins, the control of spherical aberration on the telephoto side 
becomes very difficult. 
Next, regarding the wider angle of a zoom lens, of the imaging performance, 
distortion becomes the greatest problem. This is because in the area of 
third-order aberration coefficient, distortion influences by the cube of 
the angle of view. 
As shown in FIG. 34 of the accompanying drawings, distortion is 
considerably greatly under (minus) at the wide angle end (focal length 
fw). From the wide angle end fw toward the telephoto end (focal length 
ft), distortion sequentially becomes greater in the over (plus) direction, 
and passes a zoom position at which distortion is 0, and the over value 
becomes greatest near the zoom position fm=fw.times.Z.sup.1/4. From the 
focal length fm to the telephoto end ft, the over amount sequentially 
becomes smaller. This tendency becomes greater as the angle of view at the 
wide angle end becomes greater and therefore, when the wider angle of a 
zoom lens is contrived, the control of distortion on the wide angle end 
becomes very difficult. 
In order to correct such changing of various aberrations well over the 
entire variable power range, the number of lenses in the lens unit for 
focusing or the focal length changing system has been increased to thereby 
correct it. This has led to the problem that the entire lens system 
becomes bulky and complicated. 
Also, the introduction of an aspherical surface for the solution of such a 
problem is proposed, for example, in Japanese Laid-Open Patent Application 
No. 7-35978. 
However, the specification of zoom lenses has been improved, and in a zoom 
lens having a great aperture ratio and moreover having a high variable 
power ratio beginning from a super-wide angle, the revision of the method 
of introducing an aspherical surface has become necessary. 
In a zoom lens having a great aperture ratio and moreover having a high 
variable power ratio beginning from a super-wide angle, spherical 
aberration changes greatly on the telephoto side and distortion changes 
greatly on the wide angle side. To correct both of these aberrations well, 
it is necessary to apply an aspherical surface on to an appropriate lens 
surface in a focal length changing portion. 
SUMMARY OF THE INVENTION 
The present invention has as its object the provision of a so-called 
four-unit zoom lens having an F-number of the order of 1.7 at the wide 
angle end and a wide angle (a wide angle end angle of view 
2.omega.=58.degree.-70.degree.) as well as a great aperture ratio of the 
order of 12-35 and a high variable power ratio in which the refractive 
power, F-number value, etc. of each lens unit are appropriately set and an 
aspherical surface is provided on at least one lens surface to thereby 
reduce the changing of various aberrations resulting from a focal length 
change and particularly spherical aberration on the telephoto side and 
distortion on the wide angle side are corrected well and which has high 
optical performance over the entire variable power range. 
The zoom lens of the present invention is a zoom lens which has, in 
succession from the object side, a first lens unit of positive refractive 
power fixed during a focal length change, a second lens unit of negative 
refractive power for focal length change, a third lens unit for correcting 
the changing of an image plane resulting from a focal length change, and a 
fixed fourth lens unit of positive refractive power and in which when in 
the first lens unit, the zoom ratio is Z and the maximum incidence height 
of an on-axis light beam is ht and the maximum incidence height in an 
off-axis light beam of a maximum angle of view at the wide angle end is hw 
and the maximum incidence height of the off-axis light beam of the maximum 
angle of view at a zoom position at a variable power ratio Z.sup.1/4 is 
hz, an aspherical surface AS1 is provided on at least one lens surface at 
a position satisfying 0.95&gt;hw/ht and 0.90&gt;hw/hz, the aspherical surface 
AS1, when provided on a positive refracting surface, forms a shape in 
which positive refractive power becomes weaker toward the peripheral 
portion of the lens, and when provided on a negative refracting surface, 
forms a shape in which negative refractive power becomes stronger toward 
the peripheral portion of the lens, and when the aspherical amounts of the 
aspherical surface AS1 at 100%, 90% and 70% of the effective diameter of 
the lens are .DELTA.10, .DELTA.9 and .DELTA.7, respectively, and focal 
length of the first lens unit is f1, the following conditions are 
satisfied: 
##EQU1## 
Also, when the focal length and F-number of the total system at the 
telephoto end are ft and Fno. t, respectively, and the focal length of the 
first lens unit is f1 and the F-number thereof is Fno. 1=f1/(ft/Fno. t) 
and the lateral magnification of the second lens unit at the wide angle 
end is .beta.2w and the zoom ratio thereof is Z, the following conditions 
are satisfied: 
EQU 10&lt;Z 
EQU 0.8&lt;Fno. 1&lt;1.6 (2) 
EQU -0.45&lt;.beta.2w&lt;-0.15 (3) 
Also, the first lens unit is comprised, in succession from the object side, 
of at least one negative lens and at least three positive lenses, and when 
the Abbe number of the negative lens is .nu.1n and the average value of 
the Abbe numbers of the three positive lenses is .nu.1p, the first lens 
unit satisfies the following condition: 
EQU .vertline..nu.1n-.nu.1p.vertline.&gt;42.5 (4) 
Further, at least one aspherical surface AS2 is applied to the second lens 
unit, and the aspherical surface AS2, when provided on a positive 
refracting surface, forms a shape in which positive refractive power 
becomes stronger toward the peripheral portion of the lens, and when 
provided on a negative refracting surface, forms a shape in which negative 
refractive power becomes weaker.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 to 4 are lens cross-sectional views of Numerical Value Embodiments 
1 to 4 of the present invention at the wide angle end thereof. 
In FIGS. 1 to 4, the letter F designates a focusing lens unit (front lens 
unit) of positive refractive power as a first lens unit. 
The letter V denotes a variator of negative refractive power for focal 
length change as a second lens unit, and the variator V is monotonously 
(monotonically) moved on the optical axis thereof toward the image plane 
side to thereby effect a focal length change from the wide angle end 
(wide) to the telephoto end (tele). The letter C designates a compensator 
of negative refractive power, and the compensator C is moved non-linearly 
with a convex locus on the optical axis thereof toward the object side to 
correct the changing of the image plane resulting from a focal length 
change. The variator V and the compensator C together constitute a focal 
length changing system. 
The letters SP denote a stop, and the letter R designates a fixed relay 
lens unit of positive refractive power as a fourth lens unit. The letter P 
denotes a color resolving prism, an optical filter or the like which is 
shown as a glass block in FIGS. 1 to 4. 
In the zoom lens shown in FIGS. 1 to 4, the above-mentioned conditions are 
satisfied to thereby correct the changing of aberrations well over an 
entire variable power range and obtain high optical performance. 
Description will now be made of the features of the aspherical surface of 
the zoom lens according to the present invention. 
In a zoom lens wherein the wide angle end angle of view begins from 
2.omega.=58.degree.-70.degree. and the zoom ratio is of the order of 12 to 
35 times, the incidence heights of an on-axis ray of light onto the front 
lens unit and the variator sequentially become higher from the wide angle 
end to the telephoto end as shown in FIGS. 25 to 28, and in a zoom lens 
wherein there is F drop, they become highest at an F drop starting 
position (a zoom position fd, FIG. 27). At the telephoto end, due to F 
drop, the incidence height becomes constant in the front lens unit, and 
becomes low in the variator. 
In contrast, the incidence height of an off-axis ray of light passes fully 
the effective diameter of the variator at the wide angle end, but at a 
zoom position fm=fw.times.Z.sup.1/4, the incidence height in the front 
lens unit suddenly becomes high, and conversely the incidence height in 
the variator suddenly becomes low. This tendency becomes remarkable when a 
wider angle, a higher magnification and compactness and lighter weight are 
aimed at. 
When an aspherical surface is provided in the front lens unit to thereby 
suppress the changing of aberrations, if an attempt is made to efficiently 
correct both of distortion which greatly changes on the wide angle side 
and spherical aberration which greatly changes on the telephoto side by a 
single aspherical surface, it will become very difficult. This is because 
between distortion and spherical aberration, due to the problem of their 
natures as aberrations, the aspherical shape for correcting them and the 
aspherical amount thereof differ greatly and therefore when an aspherical 
surface is provided with attention paid to one of the aberrations, it has 
a bad influence such as a high-order aberration upon the other aberration. 
So, in the present embodiment, it is the greatest feature that in order to 
correct spherical aberration which influences by the cube of the incidence 
height of the on-axis ray of light, an aspherical surface AS1 is provided 
on at least one of the lens surfaces constituting the front lens unit in 
which the on-axis ray of light becomes highest in the entire variable 
power range which satisfies 0.95&gt;hw/ht and 0.90&gt;hw/hz, where ht is the 
maximum incidence height of the on-axis light beam, hw is the maximum 
incidence height of the off-axis light beam of a maximum angle of view at 
the wide angle end, and hz is the maximum incidence height of the off-axis 
light beam of a maximum angle of view at a zoom position at a variable 
power ratio Z.sup.1/4. 
This aspherical surface, when the aspherical surface for correcting the 
changing of spherical aberration on the telephoto side is applied onto a 
positive refracting surface in the front lens unit F, forms a shape in 
which positive refractive power becomes weaker toward the peripheral 
portion of the lens, and when the aspherical surface is provided on a 
negative refracting surface, forms a shape in which negative refractive 
power becomes stronger toward the peripheral portion of the lens, to 
thereby correct the spherical aberration near the telephoto end becoming 
under (minus), thereby suppressing well the changing of the spherical 
aberration on the telephoto side. 
As an additional effect of this aspherical shape, it also becomes possible 
to suppress the over (plus) of distortion attributable to the fact that 
the off-axis incidence height in the front lens unit at the zoom position 
fm=fw.times.Z.sup.1/4 suddenly becomes high, whereby the off-axis ray of 
light is strongly jumped up by the positive refractive power of the front 
lens unit. 
Also, conversely speaking, this aspherical surface is a contrary effect 
regarding the distortion at the wide angle end, and under (minus) 
distortion attributable to the strong negative refractive power at the 
wide angle end is strongly jumped up by positive refractive power, whereby 
it becomes difficult to suppress distortion. 
That is, the introduction of the aspherical surface AS1 into that lens 
surface of the front lens unit which satisfies 0.95&gt;hw/ht and 0.9&gt;hw/hz 
means that the maximum incidence height of the on-axis ray of light in the 
entire variable power range is higher than the incidence height of the 
off-axis light beam of the maximum angle of view at the wide angle end and 
the change in the incidence height of the off-axis ray of light of the 
maximum angle of view at the zoom position fm=fw.times.Z.sup.1/4 is great, 
and well corrects the under spherical aberration at the telephoto end and 
the over distortion at the zoom position fm=fw.times.Z.sup.1/4 and yet 
does not impart any bad influence to the under distortion at the wide 
angle end, and is very effective as the effect of this aspherical shape. 
Further, in the present embodiment, in order to correct well the spherical 
aberration on the telephoto side by the wider angle, the aspherical shape 
of the front lens unit is made into a shape in which the central portion 
of the aspherical surface is a substantially spherical surface and the 
aspherical surface becomes larger in the peripheral portion thereof, so as 
to satisfy the aforementioned conditional expression (1). 
The above-mentioned conditional expression (1) is for suppressing in the 
focal length changing system of the zoom lens, the distortion increasing 
action of the aspherical surface only in some zoom range of the entire 
zoom area which is near the wide angle end, and deriving the effect of 
correcting aberrations such as spherical aberration and distortion to the 
maximum in the other zoom areas. 
Thus, in the present embodiment, the lens surface to which the aspherical 
surface is applied is appropriately set and the changing of the distortion 
on the wide angle side and the spherical aberration on the telephoto side 
is correct well, and high optical performance is obtained in the entire 
variable power range. 
Further, in order to realize a zoom lens having a zoom ratio z of 10 times 
or greater (10&lt;z) and having a large aperture in the entire zoom area, the 
present invention uses such a bright lens unit that satisfies conditional 
expression (2) as the front lens unit F. Thereby, the spherical aberration 
at the telephoto end is corrected well and yet the larger aperture and 
downsizing of the entire lens system are achieved at a time. 
If the lower limit value of conditional expression (2) is exceeded, the 
sharing of aberrations of the front lens unit F on the telephoto side will 
suddenly increase and therefore, it will become difficult to correct the 
changing of spherical aberration well, and if the upper limit value of 
conditional expression (2) is exceeded, the larger aperture and downsizing 
of the entire lens system will become difficult. 
Next, design is made such that the lateral magnification of the variator V 
satisfies conditional expression (3). Thereby, a predetermined variable 
power ratio is secured and yet the changing of aberrations is small over 
the entire variable power range and good optical performance is obtained. 
If the lower limit value of conditional expression (3) is exceeded, a 
higher magnification will become difficult to obtain, and if the upper 
limit value of conditional expression (3) is exceeded, the sharing of 
aberration correction in the focal length changing system will suddenly 
increase and therefore, it will become difficult to reduce the changing of 
aberrations over the entire variable power range and obtain high optical 
performance. 
Further, in the present embodiment, the front lens unit is comprised, in 
succession from the object side, of at least one negative lens and at 
least three positive lenses, and spherical aberration is caused to diverge 
by the negative lens and the principal point in the entire front lens unit 
is pushed out toward the object side to thereby achieve the higher 
performance and downsizing of the zoom lens and in addition, when the Abbe 
number of the negative lens is .nu.1n and the average value of the Abbe 
numbers of the three positive lenses is .nu.1p, the front lens unit 
satisfies conditional expression (4) to thereby make the achromatism 
chiefly on the telephoto side by a higher magnification sufficient. 
For example, even if in order to correct well the achromatism in the front 
lens unit, an optical material of which the Abbe number exceeds 90 is 
partly used for the convex lens in the front lens unit, the achromatism of 
the entire front lens unit will not be easily improved. This is because 
the other convex lenses and concave lenses also need share the 
achromatism. Therefore, in the present embodiment, the achromatizing 
condition in the entire front lens unit is set as shown in conditional 
expression (4) by the use of the average of the Abbe numbers of the convex 
lenses constituting the front lens unit. 
The features of each embodiment (numerical value embodiment) of the present 
invention will now be described. 
Embodiment 1 shown in FIG. 1 has a zoom ratio of 20 times and the wide 
angle end angle of view 2.omega. thereof exceeds 69.degree.. R1 to R8 
designate a front lens unit F having positive refractive power for 
focusing. R9 to R17 denote a variator V monotonously movable to the image 
plane side from the wide (wide angle end) toward the tele (telephoto end). 
R18 to R20 designate a compensator C having the image point correcting 
action resulting from a focal length change, and having negative power 
(refractive power) and moved toward the object side so as to describe a 
convex arc during the focal length change from wide to tele. SP (R21) 
denotes a stop. R22 to R38 designate a relay lens unit R having the 
imaging action, and R39 to R41 designate a glass block equivalent to a 
color resolving prism. 
In this Embodiment 1, when as the index of a large aperture, F number Fno. 
1 is defined as Fno. 1=f1/(ft/Fno. t) in the front lens unit, the aperture 
is a large aperture of Fno. 1=1.09. For these large apertures, the front 
lens unit is comprised, in succession from the object side, of four 
concave, convex, convex and convex lenses, and spherical aberration is 
caused to diverge by the concave lens to thereby suppress the occurrence 
of spherical aberration in the front lens unit. Further, in order to 
correct well the achromatism in the front lens unit, an optical material 
of which the Abbe number exceeds 90 is partly used in the convex lenses of 
the front lens unit. However, if an optical material of which the Abbe 
number exceeds 90 is simply used for some of the convex lenses, the 
achromatism of the entire front lens unit will not be improved. Therefore, 
in the present embodiment, the Abbe number of the concave lens 
constituting the front lens unit is of the order of 25 and the average of 
the Abbe numbers of the convex lenses is of the order of 74, whereby the 
achromatism in the entire front lens unit is made good. At this time, the 
aforementioned conditional expression is 
.vertline..nu.1n-.nu.1p.vertline.=48.5. 
As regards the lateral magnification .beta.2w of the variator V at the wide 
angle end, the zoom ratio is 20 times and therefore, the absolute value of 
the lateral magnification is .beta.2w=-0.255. The variator V is comprised, 
in succession from the object side, of a concave lens having its sharp 
concave surface facing the image plane side, a convex lens of a relatively 
small Abbe number, a concave lens, a convex lens of a relatively small 
refractive index, and a concave lens, to thereby suppress the occurrence 
of distortion, spherical aberration and coma in the variator and also 
effectively correct the changing of chromatic aberration. 
The aspherical surface in the front lens unit is applied onto a surface R5, 
and efficiently corrects the under spherical aberration at the telephoto 
end in the front lens unit and the over distortion at the zoom position 
fm=fw.times.Z.sup.1/4 at the same time. At this time, it effectively 
utilizes that the maximum incidence height of the on-axis ray of light in 
the entire variable power range is higher than the incidence height of the 
off-axis ray of light of the maximum angle of view at the wide angle end 
and the change in the incidence height of the off-axis ray of light of the 
maximum angle of view at the wide angle end and the zoom position 
fm=fw.times.Z.sup.1/4 is great, and hw/ht=0.781 and hw/hz=0.745. The 
direction of the aspherical surface is a direction in which positive power 
becomes weaker as the amount of separation from the optical axis becomes 
greater, and in order to correct spherical aberration and distortion 
efficiently up to a high-order area, up to aspherical surface coefficients 
B, C, D and E are used. The aspherical amount at this time is 302.4 .mu.m 
at the maximum height of the incident ray of light on R5. 
Also, an aspherical surface is applied onto a surface R9 in the variator, 
and corrects the under distortion near the wide angle end particularly by 
the utilization of the fact that the off-axis ray of light passes only 
near the wide angle end. The direction of the aspherical surface is a 
direction in which positive power becomes stronger as the amount of 
separation from the optical axis becomes greater, and in order to correct 
distortion efficiently up to a high-order area, up to aspherical surface 
coefficients B, C, D and E are used. The aspherical amount at this time is 
168.4 .mu.m at the maximum height of the incident ray of light on R9. 
FIGS. 5A to 5C to FIGS. 9A to 9C show spherical aberration, astigmatism and 
distortion at respective zoom positions. 
Embodiment 2 shown in FIG. 2 has a zoom ratio of 15 times and the wide 
angle end angle of view 2.omega. thereof exceeds 65.degree.. R1 to R10 
designate a front lens unit having positive refractive power for focusing. 
R11 to R18 denote a variator V monotonously movable toward the image plane 
side from wide (wide angle end) to tele (telephoto end) for focal length 
change. R19 to R21 designate the same compensation C having the image 
point correcting action resulting from a focal length change, and having 
negative power (refractive power) and movable toward the object side so as 
to describe a convex arc during the focal length change from wide to tele. 
SP (R22) denotes a stop. R23 to R39 designate a relay lens unit R having 
the imaging action, and R40 to R42 denote a glass block equivalent to a 
color resolving prism. 
In this Embodiment 2, when as the index of a large aperture, F-number Fno. 
1 is defined as Fno. 1=f1/(ft/Fno. t) n the front lens unit, the aperture 
is a large aperture of Fno. 1=1.10. For these large apertures, the front 
lens unit is comprised, in succession from the object side, of five 
concave, convex, convex, convex and convex lenses, and spherical 
aberration is caused to diverge by the concave lens to thereby suppress 
the occurrence of spherical aberration in the front lens unit. Further, in 
order to correct well the achromatism in the front lens unit, optical 
material of which the Abbe number exceeds 80-90 is partly used in the 
convex lenses of the front lens unit. However, if an optical material of 
which the Abbe number exceeds 80-90 is simply used for some of the convex 
lenses, the achromatism of the entire front lens unit will not be 
improved. Therefore, in the present embodiment, the Abbe number of the 
concave lens constituting the front lens unit is of the order of 25 and 
the average of the Abbe numbers of the convex lenses is of the order of 
74, whereby the achromatism in the entire front lens unit is made good. At 
this time, the aforementioned conditional expression is 
.vertline..nu.1n-.nu.1p.vertline.=48.9. 
As regards the lateral magnification .beta.2w of the variator V at the wide 
angle end, the zoom ratio is 15 times and therefore, the absolute value of 
the lateral magnification is .beta.2w=-0.291. The variator V is comprised, 
in succession from the object side, of a concave lens having its sharp 
concave surface facing the image plane side, a convex lens and concave 
lens, to thereby suppress the occurrence of distortion, spherical 
aberration and coma in the variator and also correct the changing of 
chromatic aberration effectively. 
The aspherical surface in the front lens unit is applied onto a surface R5, 
and efficiently corrects the under spherical aberration at the telephoto 
end in the front lens unit and the over distortion at the zoom position 
fm=fw.times.Z.sup.1/4 at a time. At this time, it effectively utilizes the 
fact that the maximum incidence height of the on-axis ray of light in the 
entire variable power range is higher than the incidence height of the 
off-axis ray of light of the maximum angle of view at the wide angle end 
and the change in the incidence height of the off-axis ray of light of the 
maximum angle of view at the wide angle end and the zoom position 
fm=fw.times.Z.sup.1/4 is great, and hw/ht=0.901 and hw/hz=0.853. 
The direction of the aspherical surface is a direction in which positive 
power becomes weaker as the amount of separation from the optical axis 
becomes greater, and in order to correct spherical aberration and 
distortion efficiently up to a high-order area, up to aspherical surface 
coefficients B, C, D and E are used. The aspherical amount at this time is 
29.7 .mu.m at the maximum height of the incident ray of light on R5. 
Also, an aspherical surface is provided on a surface R18 in the variator, 
and corrects the under distortion near the wide angle end particularly by 
the utilization of the fact that the off-axis ray of light passes only 
near the wide angle end, and also suppresses the diverging action of 
spherical aberration in the variator. The direction of the aspherical 
surface is a direction in which positive power becomes stronger as the 
amount of separation from the optical axis becomes greater, and in order 
to correct distortion and spherical aberration efficiently up to a 
high-order area, up to aspherical surface coefficients B, C, D and E are 
used. The aspherical amount at this time is 102.3 .mu.m at the maximum 
height of the incident ray of light on R18. 
FIGS. 10A to 10C to FIGS. 14A to 14C show spherical aberration, astigmatism 
and distortion at respective zoom positions. 
Embodiment 3 shown in FIG. 3 has a zoom ratio of 12 times, and the wide 
angle end angle of view 2.omega. thereof exceeds 62.degree.. R1 to R10 
designate a front lens unit F having positive refractive power for 
focusing. R11 to R19 denotes a variator V monotonously movable toward the 
image plane side from wide (wide angle end) to tele (telephoto end) for 
focal length change. R20 to R22 designate a compensator having the image 
point correcting action resulting from a focal length change and having 
negative power (refractive power), and movable toward the object side so 
as to describe a convex arc during the focal length change from wide to 
tele. SP (R23) denotes a stop. R24 to R40 designate a relay lens unit R 
having the imaging action, and R41 to R43 denotes a glass block equivalent 
to a color resolving prism. 
In this Embodiment 3, when as the index of a large aperture, F-number Fno. 
1 is defined as Fno. 1=f1/(ft/Fno. t) in the front lens unit, the aperture 
is a large aperture of Fno. 1=0.866. For these large apertures, the front 
lens unit is comprised, in succession from the object side, of five 
concave, convex, convex, convex and convex lenses, and spherical 
aberration is caused to diverge by the concave lens to thereby suppress 
the occurrence of spherical aberration in the front lens unit. Further, in 
order to correct well the achromatism in the front lens unit, an optical 
material of which the Abbe number exceeds 80 is partly used in the convex 
lenses of the front lens unit. However, if an optical material of which 
the Abbe number exceeds 80 is simply used for some of the convex lenses, 
the achromatism of the entire front lens unit will not be improved. 
Therefore, in the present embodiment, the Abbe number of the concave lens 
constituting the front lens unit is of the order of 25 and the average of 
the Abbe numbers of the convex lenses is of the order of 71, whereby the 
achromatism in the entire front lens unit is made good. At this time, the 
aforementioned conditional expression is 
.vertline..nu.1n-.nu.1p.vertline.=45.5. 
As regards the lateral magnification .beta.2w of the variator V at the wide 
angle end, the zoom ratio is 12 times and therefore, the absolute value of 
the lateral magnification is relatively great, namely, .beta.2w=-0.429. 
The variator V is comprised, in succession from the object side, of a 
concave lens of a shape having its sharp concave surface facing the image 
plane side, a convex lens of a relatively small Abbe number, a concave 
lens, a convex lens of a relatively small refractive index, and a concave 
lens, to thereby suppress the occurrence of distortion, spherical 
aberration and coma in the variator and also correct the changing of 
chromatic aberration effectively. 
The aspherical surface in the front lens unit is applied onto a surface R9, 
and efficiently corrects the under spherical aberration at the telephoto 
end in the front lens unit and the over distortion at the zoom position 
fm=fw.times.Z.sup.1/4 at a time. At this time, it effectively utilizes the 
fact that the maximum incidence height of the on-axis ray of light in the 
entire variable power range is higher than the incidence height of the 
off-axis ray of light of the maximum angle of view at the wide angle end 
and the change in the incidence height of the off-axis ray of light of the 
maximum angle of view at the wide angle end and the zoom position 
fm=fw.times.Z.sup.1/4 is great, and hw/ht=0.669 and hw/hz=0.786. 
The direction of the aspherical surface is a direction in which positive 
power becomes weaker as the amount of separation from the optical axis 
becomes greater, and in order to correct spherical aberration and 
distortion efficiently up to a high-order area, up to aspherical surface 
coefficients B, C, D and E are used. The aspherical amount at this time is 
241.4 .mu.m at the maximum height of the incident ray of light on R9. 
Also, an aspherical surface is applied onto a surface R11 in the variator, 
and corrects the under distortion near the wide angle end particularly by 
the utilization of the fact that the off-axis ray of light passes only 
near the wide angle end. The direction of the aspherical surface is a 
direction in which positive power becomes stronger as the amount of 
separation from the optical axis becomes greater, and in order to correct 
distortion efficiently up to a high-order area, up to aspherical surface 
coefficients B, C, D and E are used. The aspherical amount at this time is 
651.2 .mu.m at the maximum height of the incidence ray of light on R11. 
FIGS. 15A to 15C to FIGS. 19A to 19C show spherical aberration, astigmatism 
and distortion at respective zoom positions. 
Embodiment 4 shown in FIG. 4 has a zoom ratio of 35 times, and the wide 
angle end angle of view 2.omega. thereof exceeds 57.degree.. R1 to R8 
designates a front lens unit F having positive refractive power for 
focusing. R9 to R16 denote a variator V monotonously movable toward the 
image plane side from wide (wide angle end) to tele (telephoto end) for 
focal length change. R17 to R19 designate a compensator C having the image 
point correcting action resulting from a focal length change and having 
negative power (refractive power), and movable toward the object side so 
as to describe a convex arc during the focal length change from wide to 
tele. SP (R20) denotes a stop. R21 to R37 designate a relay lens unit R 
having the imaging action, and R38 to R40 denote a glass block equivalent 
to a color resolving prism. 
In this Embodiment 4, when as the index of a large aperture F-number Fno. 1 
is defined as Fno. 1=f1/(ft/Fno. t) in the front lens unit, the aperture 
is a large aperture of Fno. 1=1.52. For these large apertures, the front 
lens unit is comprised, in succession from the object side, of four 
concave, convex, convex and convex lenses, and spherical aberration is 
caused to diverge by the concave lens to thereby suppress the occurrence 
of spherical aberration in the front lens unit. Further, in order to 
correct well the achromatism in the front lens unit, an optical material 
of which the Abbe number exceeds 90 is partly used in the convex lenses of 
the front lens unit. However, if an optical material of which the Abbe 
number exceeds 90 is simply used for some of the convex lenses, the 
achromatism of the entire front lens unit is not improved. Therefore, in 
the present embodiment, the Abbe number of the concave lens constituting 
the front lens unit is of the order of 37, but the average of the Abbe 
numbers of the convex lenses is of the order of 82, whereby the 
achromatism in the entire front lens unit is made good. At this time, the 
aforementioned conditional expression is 
.vertline..nu.1n-.nu.1P.vertline.=45.0. 
As regards the lateral magnification .beta.2w of the variator at the wide 
angle end, the zoom ratio is 35 times and therefore, the absolute value of 
the lateral magnification is relatively small, namely, .beta.2w=-0.182. 
The variator V is comprised, in succession from the object side, of a 
concave lens of a shape having its sharp concave surface facing the image 
plane side, a convex lens of a relatively small Abbe number, a concave 
lens, a convex lens of a relatively small refractive index, and a concave 
lens, to thereby suppress the occurrence of distortion, spherical 
aberration and coma in the variator and also corrects the changing of 
chromatic aberration effectively. 
In this Numerical Value Embodiment 4, as shown in FIGS. 29 to 32, by the 
appropriate power arrangement thereof, all the lens surfaces constituting 
the front lens unit in the entire variable power range satisfy the 
aforementioned aspherical surface introducing conditions 0.95&gt;hw/ht and 
0.90&gt;hw/hz. Therefore, the aspherical surfaces in the front lens unit are 
applied onto a surface R1 and a surface R7 to thereby efficiently correct 
the under spherical aberration at the telephoto end in the front lens unit 
and the over distortion at the zoom position fm=fw.times.Z.sup.1/4 at a 
time. At this time, it is effectively utilized that the maximum incidence 
height of the on-axis ray of light in the entire variable power range is 
higher than the incidence height of the off-axis light beam of the maximum 
angle of view at the wide angle end and the change in the incidence height 
of the off-axis ray of light of the maximum angle of view at the wide 
angle end and the zoom position fm=fw.times.Z.sup.1/4 is great, and 
hw/ht=0.506 and hw/hz=0.547. 
As regards the directions of the aspherical surfaces, the direction of the 
aspherical surface on the surface R1 is a direction in which negative 
power becomes stronger as the amount of separation from the optical axis 
becomes greater, and the direction of the aspherical surface on the 
surface R7 is a direction in which positive power becomes weaker as the 
amount of separation from the optical axis becomes greater, and both 
aspherical surfaces use up to aspherical surface coefficients B, C, D and 
E in order to correct spherical aberration and distortion efficiently up 
to a high-order area. The aspherical amounts at this time are 54.5 .mu.m 
and 239.9 .mu.m at the maximum heights of the incident rays of light on R1 
and R7, respectively. 
FIGS. 20A to 20C to FIGS. 24A to 24C show spherical aberration, astigmatism 
and distortion at respective zoom positions. 
Some numerical value embodiments of the present invention will be shown 
below. In the numerical value embodiments, R1 represents the radius of 
curvature of the ith lens surface from the object side, Di represents the 
thickness and air space of the ith lens from the object side, and Ni and 
.nu.i represent the refractive index and Abbe number, respectively, of the 
material of the ith lens from the object side. 
When the direction of the optical axis is the X-axis and the direction 
perpendicular to the optical axis is the H-axis and the direction of 
travel of light is positive and R is the paraxial radius of curvature and 
k, B, C, D and E are aspherical surface coefficients, the aspherical shape 
is represented by the following expression: 
##EQU2## 
__________________________________________________________________________ 
(Numerical Value Embodiment 1) 
f = 8.0 to 160.0 fno = 1.8 to 2.5 2w = 69.degree. to 3.9.degree. 
__________________________________________________________________________ 
r 1 = 
-398.617 
d 1 = 2.00 
n 1 = 
1.81265 
.nu. 1 = 
25.4 
r 2 = 138.411 d 2 = 5.88 
r 3 = 190.482 d 3 = 11.07 n 2 = 1.43985 .nu. 2 = 95.0 
r 4 = -158.221 d 4 = 6.95 
aspherical r 5 = 104.571 d 5 = 10.45 n 3 = 1.62033 .nu. 3 = 63.3 
surface r 6 = -361.269 d 6 = 0.20 
r 7 = 61.616 d 7 = 8.76 n 4 = 1.62033 .nu. 4 = 63.3 
r 8 = 240.012 d 8 = variable 
aspherical r 9 = 623.406 d 9 = 0.80 n 5 = 1.88815 .nu. 5 = 40.8 
surface r10 = 15.320 d10 = 5.99 
r11 = -120.427 d11 = 6.55 n 6 = 
1.81264 .nu. 6 = 25.4 
r12 = -13.787 d12 = 0.80 n 7 = 1.77621 .nu. 7 = 49.6 
r13 = 31.762 d13 = 0.20 
r14 = 23.275 d14 = 4.97 n 8 = 1.57047 .nu. 8 = 42.8 
r15 = -66.697 d15 = 1.11 
r16 = -28.678 d16 = 0.80 n 9 = 1.88815 .nu. 9 = 40.8 
r17 = -58.591 d17 = variable 
r18 = -30.127 d18 = 0.80 n10 = 1.82017 .nu.10 = 46.6 
r19 = 69.206 d19 = 2.34 n11 = 1.93306 .nu.11 = 21.3 
r20 = -290.396 d20 = variable 
r21 = (stop) d21 = 1.30 
r22 = 766.570 d22 = 4.10 n12 = 1.62286 .nu.12 = 60.3 
r23 = -42.080 d23 = 0.15 
r24 = 148.919 d24 = 3.22 n13 = 1.52033 .nu.13 = 58.9 
r25 = -90.383 d25 = 0.15 
r26 = 61.396 d26 = 6.60 n14 = 1.52033 .nu.14 = 58.9 
r27 = -35.780 d27 = 1.15 n15 = 1.79012 .nu.15 = 44.2 
r28 = 698.727 d28 = 34.00 
r29 = 79.382 d29 = 5.22 n16 = 1.51825 .nu.16 = 64.1 
r30 = -47.920 d30 = 2.24 
r31 = -86.685 d31 = 1.15 n17 = 1.80401 .nu.17 = 42.2 
r32 = 25.952 d32 = 6.44 n18 = 1.52032 .nu.18 = 59.0 
r33 = -144.488 d33 = 0.15 
r34 = 59.870 d34 = 6.98 n19 = 1.48915 .nu.19 = 70.2 
r35 = -27.698 d35 = 1.15 n20 = 1.81078 .nu.20 = 40.9 
r36 = -219.881 d36 = 0.15 
r37 = 48.862 d37 = 5.74 n21 = 1.52032 .nu.21 = 59.0 
r38 = -55.798 d38 = 4.50 
r39 = .infin. d39 = 30.00 n22 = 1.60718 .nu.22 = 38.0 
r40 = .infin. d40 = 16.20 n23 = 1.51825 .nu.23 = 64.2 
r41 = .infin. 
__________________________________________________________________________ 
TABLE 1 
______________________________________ 
Variable Focal length 
spacing 8.00 16.92 48.00 115.20 
160.00 
______________________________________ 
d 8 0.80 23.10 41.56 49.92 51.77 
d17 53.41 27.52 6.51 3.44 6.19 
d20 4.50 8.08 10.63 5.34 0.74 
______________________________________ 
Aspherical Lens Shape 
surface R5 
reference spherical 
aspherical 
surface R = 104.571 amount (R5) h .DELTA. 
______________________________________ 
aspherical 70% (26.97mm) 70.0 .mu.m 
coefficient 90% (34.67mm) 195.6 .mu.m 
k = 2.258 .times. D.sup.-1 100% (38.53mm) 302.4 .mu.m 
B = -1.034 .times. D.sup.-7 
.vertline..DELTA.10/f1.vertline. = 4.320 .times. 10.sup.-3 
C = 3.972 .times. D.sup.-12 .vertline. .DELTA.9/f1.vertline. 
= 2.795 .times. 10.sup.-3 
D = 4.819 .times. D.sup.-16 .vertline. .DELTA.7/f1.vertline. = 1.060 
.times. 10.sup.-3 
E = -3.114 .times. D.sup.-19 
surface R9 
reference spherical 
Zoom parameter 
surface R =623.406 
aspherical Fno. 1 = 1.09 
coefficient .beta.2w = -0.255 
k = 1.561 .times. D.sup.-3 .vertline..nu.1n-.nu.1p.vertline. = 48.5 
B = 7.730 .times. D.sup.-6 hw/ht = 0.781 
C = -3.619 .times. D.sup.-8 hw/hz = 0.745 
D = 1.176 .times. D.sup.-10 
E = -2.852 .times. D.sup.-13 
______________________________________ 
__________________________________________________________________________ 
(Numerical Value Embodiment 2) 
f = 8.5 to 127.5 fno = 1.7 to 2.0 2w = 65.8.degree. to 4.9.degree. 
__________________________________________________________________________ 
r 1 = 
-244.102 
d 1 = 2.00 
n 1 = 
1.81265 
.nu. 1 = 
25.4 
r 2 = 158.001 d 2 = 7.15 
r 3 = 248.421 d 3 = 9.83 n 2 = 1.43985 .nu. 2 = 95.0 
r 4 = -162.011 d 4 = 7.23 
aspherical r 5 = 169.967 d 5 = 8.29 n 3 = 1.49845 .nu. 3 = 81.5 
surface r 6 = -334.274 d 6 = 0.20 
r 7 = 116.489 d 7 = 7.61 n 4 = 1.62286 .nu. 4 = 60.3 
r 8 = -2771.455 d 8 = 0.20 
aspherical r 9 = 63.214 d 9 = 7.01 n 5 = 1.62286 .nu. 5 = 60.3 
surface r10 = 147.412 d10 = 
variable 
r11 = 74.395 d11 = 0.80 n 6 = 1.83945 .nu. 6 = 42.7 
r12 = 16.628 d12 = 7.63 
r13 = -49.291 d13 = 0.80 n 7 = 1.77621 .nu. 7 = 49.6 
r14 = 59.918 d14 = 2.70 
r15 = 42.118 d15 = 5.61 n 8 = 1.85501 .nu. 8 = 23.9 
r16 = -33.757 d16 = 1.23 
r17 = -24.733 d17 = 0.80 n 9 = 1.77621 .nu. 9 = 49.6 
r18 = 118.870 d18 = variable 
r19 = -28.022 d19 = 0.80 n10 = 1.77621 .nu.10 = 49.6 
r20 = 39.558 d20 = 2.87 n11 = 1.85501 .nu.11 = 23.9 
r21 = -1317.486 d21 = variable 
r22 = (stop) d22 = 2.00 
r23 = -183.995 d23 = 3.75 n12 = 1.62286 .nu.12 = 60.3 
r24 = -37.732 d24 = 0.15 
r25 = 114.677 d25 = 3.02 n13 = 1.51976 .nu.13 = 52.4 
r26 = -147.958 d26 = 0.15 
r27 = 38.367 d27 = 7.89 n14 = 1.51976 .nu.14 = 52.4 
r28 = -37.297 d28 = 1.15 n15 = 1.79012 .nu.15 = 44.2 
r29 = 372.464 d29 = 25.00 
r30 = 80.115 d30 = 5.23 n16 = 1.51825 .nu.16 = 64.1 
r31 = -47.881 d31 = 1.22 
r32 = -148.415 d32 = 1.15 n17 = 1.83945 .nu.17 = 42.7 
r33 = 23.676 d33 = 7.22 n18 = 1.50349 .nu.18 = 56.4 
r34 = -77.651 d34 = 0.15 
r35 = 36.972 d35 = 7.27 n19 = 1.48915 .nu.19 = 70.2 
r36 = -28.179 d36 = 1.15 n20 = 1.83932 .nu.20 = 37.2 
r37 = 265.720 d37 = 0.15 
r38 = 40.982 d38 = 5.67 n21 = 1.48915 .nu.21 = 70.2 
r39 = -49.496 d39 = 4.50 
r40 = .infin. d40 = 30.00 n22 = 1.60718 .nu.22 = 38.0 
r41 = .infin. d41 = 16.20 n23 = #.51825 .nu.23 = 64.2 
r42 = .infin. 
__________________________________________________________________________ 
TABLE 2 
______________________________________ 
Variable Focal length 
spacing 8.50 17.00 51.00 108.38 
127.50 
______________________________________ 
d10 1.23 21.80 41.49 48.94 50.03 
d18 51.71 28.49 7.37 4.83 5.73 
d21 4.00 6.65 8.08 3.16 1.18 
______________________________________ 
Aspherical Lens Shape 
surface R5 
reference spherical 
aspherical 
surface R =169.967 amount (R5) h .DELTA. 
______________________________________ 
aspherical 70% (27.68mm) 7.6 .mu.m 
coefficient 90% (35.58mm) 19.6 .mu.m 
k = 1.799 .times. D.sup.0 100% (39.54mm) 29.7 .mu.m 
B = -5.947 .times. D.sup.-8 
.vertline..DELTA.10/f1.vertline. = 4.237 .times. 10.sup.-4 
C = -3.462 .times. D.sup.-12 .vertline. .DELTA.9/f1.vertline. 
= 2.798 .times. 10.sup.-4 
D = 2.547 .times. D.sup.-15 .vertline. .DELTA.7/f1.vertline. = 1.084 
.times. 10.sup.-4 
E = -1.186 .times. D.sup.-18 
surface R18 
reference spherical 
Zoom parameter 
surface R = 118.870 Fno.1 = 1.10 
aspherical 
coefficient .beta.2w = -0.291 
k = -6.054 .times. D.sup.1 .vertline..nu.1n-.nu.1p.vertline. = 48.9 
B = -3.099 .times. D.sup.-6 hw/ht = 0.901 
C = -6.745 .times. D.sup.-10 hw/hz = 0.853 
D = -5.509 .times. D.sup.-11 
E = -1.583 .times. D.sup.-13 
______________________________________ 
__________________________________________________________________________ 
(Numerical Value Embodiment 3) 
f = 9.0 to 108.0 fno = 1.7 2w = 62.9.degree. to 5.8.degree. 
__________________________________________________________________________ 
r 1 = 
-122.883 
d 1 = 2.30 
n 1 = 
1.81265 
.nu. 1 = 
25.4 
r 2 = 197.553 d 2 = 5.56 
r 3 = 244.561 d 3 = 10.45 n 2 = 1.49845 .nu. 2 = 81.5 
r 4 = -123.313 d 4 = 5.09 
aspherical r 5 = 186.700 d 5 = 8.25 n 3 = 1.49845 .nu. 3 = 81.5 
surface r 6 = -223.938 d 6 = 0.20 
r 7 = 97.053 d 7 = 8.50 n 4 = 1.62286 .nu. 4 = 60.3 
r 8 = 10246.315 d 8 = 0.20 
aspherical r 9 = 50.457 d 9 = 9.31 n 5 = 1.62286 .nu. 5 = 60.3 
surface r10 = 138.046 d10 = 
variable 
r11 = 291.368 d11 = 0.80 n 6 = 1.88815 .nu. 6 = 40.8 
r12 = 16.177 d12 = 6.60 
r13 = -1315.056 d13 = 6.93 n 7 = 1.81264 .nu. 7 = 25.4 
r14 = -16.342 d14 = 0.80 n 8 = 1.77621 .nu. 8 = 49.6 
r15 = 25.169 d15 = 0.20 
r16 = 20.444 d16 = 6.04 n 9 = 1.57047 .nu. 9 = 42.8 
r17 = -61.211 d17 = 1.50 
r18 = -24.211 d18 = 0.80 n10 = 1.74678 .nu.10 = 49.3 
r19 = -57.128 d19 = variable 
r20 = -28.241 d20 = 0.80 n11 = 1.77621 .nu.11 = 49.6 
r21 = 83.585 d21 = 2.36 n12 = 1.85501 .nu.12 = 23.9 
r22 = -207.605 d22 = variable 
r23 = (stop) d23 = 1.40 
r24 = -5760.891 d24 = 3.01 n13 = 1.51976 .nu.13 = 52.4 
r25 = -59.636 d25 = 0.20 
r26 = 117.576 d26 = 3.00 n14 = 1.65223 .nu.14 = 33.8 
r27 = -99.997 d27 = 0.20 
r28 = 61.101 d28 = 6.55 n15 = 1.51976 .nu.15 = 52.4 
r29 = -28.796 d29 = 1.30 n16 = 1.73234 .nu.16 = 54.7 
r30 = -1741.609 d30 = 25.00 
r31 = 1590.884 d31 = 4.21 n17 = 1.48915 .nu.17 = 70.2 
r32 = -39.140 d32 = 0.20 
r33 = -506.290 d33 = 1.50 n18 = 1.83932 .nu.18 = 37.2 
r34 = 26.889 d34 = 6.08 n19 = 1.48915 .nu.19 = 70.2 
r35 = -113.555 d35 = 0.20 
r36 = 73.457 d36 = 4.94 n20 = 1.48915 .nu.20 = 70.2 
r37 = -41.482 d37 = 1.50 n21 = 1.81265 .nu.21 = 25.4 
r38 = -107.712 d38 = 0.20 
r39 = 28.325 d39 = 4.43 n22 = 1.48915 .nu.22 = 70.2 
r40 = 245.562 d40 = 4.40 
r41 = .infin. d41 = 30.00 n23 = 1.60718 .nu.23 = 38.0 
r42 = .infin. d42 = 16.20 n24 = 1.51825 .nu.24 = 64.2 
r43 = .infin. 
__________________________________________________________________________ 
TABLE 3 
______________________________________ 
Variable Focal length 
spacing 9.00 16.75 36.00 72.00 108.00 
______________________________________ 
d10 0.96 15.05 26.39 32.49 34.62 
d19 37.52 21.49 10.46 9.61 13.29 
d22 10.00 11.94 11.63 6.38 0.57 
______________________________________ 
Aspherical Lens Shape 
surface R9 
reference spherical 
aspherical 
surface R =50.457 amount (R9) h .DELTA. 
______________________________________ 
aspherical 70% (23.06mm) 40.9 .mu.m 
coefficient 90% (29.65mm) 137.5 .mu.m 
k = -3.622 .times. D.sup.-3 100% (32.94mm) 241.4 .mu.m 
B = -1.041 .times. D.sup.-7 
.vertline..DELTA.10/f1.vertline. = 4.390 .times. 10.sup.-3 
C = -6.671 .times. D.sup.-11 .vertline. .DELTA.9/f1.vertline. 
= 2.499 .times. 10.sup.-3 
D = 1.446 .times. D.sup.-14 .vertline. .DELTA.7/f1.vertline. = 7.432 
.times. 10.sup.-3 
E = -3.093 .times. D.sup.-17 
surface R11 
reference spherical 
Zoom parameter 
surface R = 291.368 Fno. 1 = 0.866 
aspherical 
coefficient .beta.2w = -0.429 
k = 9.963 .times. D.sup.-4 .vertline..nu.1n-.nu.1p.vertline. = 45.5 
B = 8.515 .times. D.sup.-6 hw/ht = 0.669 
C = -1.308 .times. D.sup.-8 hw/hz = 0.786 
D = 2.225 .times. D.sup.-11 
E = -2.364 .times. D.sup.-14 
______________________________________ 
__________________________________________________________________________ 
(Numerical Value Embodiment 4) 
f = 10.0 to 350.0 fno = 2.0 to 3.8 2w = 57.6.degree. to 1.8.degree. 
__________________________________________________________________________ 
r 1 = 
-4936.075 
d 1 = 2.50 
n 1 = 
1.83932 
.nu. 1 = 
37.2 
r 2 = 162.964 d 2 = 1.53 
r 3 = 185.106 d 3 = 12.11 n 2 = 1.43985 .nu. 2 = 95.0 
r 4 = -336.653 d 4 = 0.25 
aspherical r 5 = 116.937 d 5 = 15.29 n 3 = 1.49845 .nu. 3 = 81.5 
surface r 6 = -377.042 d 6 = 0.25 
r 7 = 103.823 d 7 = 8.18 n 4 = 1.48915 .nu. 4 = 70.2 
r 8 = 268.086 d 8 = variable 
aspherical r 9 = 140.048 d 9 = 1.00 n 5 = 1.82017 .nu. 5 = 46.6 
surface r10 = 19.197 d10 = 6.82 
r11 = -124.220 d11 = 6.48 n 6 = 
1.81264 .nu. 6 = 25.4 
r12 = -18.406 d12 = 1.00 n 7 = 1.82017 .nu. 7 = 46.6 
r13 = 79.566 d13 = 0.25 
r14 = 30.350 d14 = 6.97 n 8 = 1.57047 .nu. 8 = 42.8 
r15 = -42.567 d15 = 1.00 n 9 = 1.88815 .nu.9 = 40.8 
r16 = 282.784 d16 = variable 
r17 = -44.889 d17 = 1.00 n10 = 1.80401 .nu.10 = 42.2 
r18 = 57.767 d18 = 3.41 n11 = 1.93306 .nu.11 = 21.3 
r19 = 957.007 d19 = variable 
r20 = 0.000 (stop) d20 = 1.30 
r21 = 1384.436 d21 = 5.25 n12 = 1.62286 .nu.12 = 60.3 
r22 = -51.145 d22 = 0.20 
r23 = 110.714 d23 = 4.21 n13 = 1.52033 .nu.13 = 58.9 
r24 = -161.931 d24 = 0.20 
r25 = 43.436 d25 = 9.10 n14 = 1.48915 .nu.14 = 70.2 
r26 = -61.248 d26 = 1.50 n15 = 1.83932 .nu.15 = 37.2 
r27 = 91.884 d27 = 42.50 
r28 = -9205.397 d28 = 4.94 n16 = 1.52033 .nu.16 = 58.9 
r29 = -54.256 d29 = 0.70 
r30 = 68.482 d30 = 1.50 n17 = 1.80401 .nu.17 = 42.2 
r31 = 29.516 d31 = 6.45 n18 = 1.52032 .nu.18 = 59.0 
r32 = 188.141 d32 = 0.33 
r33 = 33.043 d33 = 7.87 n19 = 1.48915 .nu.19 = 70.2 
r34 = -67.049 d34 = 1.50 n20 = 1.79012 .nu.20 = 44.2 
r35 = 122.181 d35 = 3.87 
r36 = -148.214 d36 = 2.04 n21 = 1.52033 .nu.21 = 58.9 
r37 = -125.900 d37 = 5.50 
r38 = 0.000 d38 = 37.50 n22 = 1.60718 .nu.22 = 38.0 
r39 = 0.000 d39 = 20.25 n23 = 1.51825 .nu.23 = 64.2 
r40 = 0.000 
__________________________________________________________________________ 
TABLE 4 
______________________________________ 
Variable Focal length 
spacing 10.00 24.32 60.00 184.00 
350.00 
______________________________________ 
d 8 0.70 50.73 81.20 102.02 108.13 
d16 117.58 62.05 26.81 8.64 13.22 
d19 4.00 9.49 14.26 11.61 0.92 
______________________________________ 
Aspherical Lens Shape 
surface R1 
reference spherical 
aspherical 
surface R =-4936.075 amount (R1) h .DELTA. 
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aspherical 70% (34.82mm) 9.9 .mu.m 
coefficient 90% (44.77mm) 33.1 .mu.m 
k = 2.206 .times. D.sup.2 100% (49.74mm) 54.5 .mu.m 
B = -4.706 .times. D.sup.-9 aspherical 
C = -7.537 .times. D.sup.-13 amount (R7) h .DELTA. 
D = -8.844 .times. D.sup.-16 70% (31.46mm) 50.8 .mu.m 
E = 2.191 .times. D.sup.-9 90% (40.45mm) 149.3 .mu.m 
100% (44.94mm) 239.9 .mu.m 
surface R7 
reference spherical 
Zoom parameter 
surface R =103.823 Fno.1 = 1.52 
aspherical 
coefficient .beta.2w = -0.182 
k = -1.362 .times. D.sup.-1 .vertline..nu.1n-.nu.1p.vertline. = 45.0 
B = -3.063 .times. D.sup.-8 hw/ht = (R1)0.796,(R7)0.5 
06 
C = -5.959 .times. D.sup.-12 hw/hz = (R1)0.733,(R7)0.547 
D = 2.115 .times. D.sup.-15 
E = -7.751 .times. D.sup.-19 
surface R1 
.vertline..DELTA.10/f1.vertline. = 3.891 .times. 10.sup.-4 
.vertline. .DELTA.9/f1.vertline. = 2.364 .times. 10.sup.-4 
.vertline. .DELTA.7/f1.vertline. = 7.079 .times. 10.sup.-5 
surface R7 
.vertline..DELTA.10/f1.vertline. = 1.713 .times. 10.sup.-3 
.vertline. .DELTA.9/f1.vertline. = 1.067 .times. 10.sup.-3 
.vertline. .DELTA.7/f1.vertline. = 3.626 .times. 10.sup.-4 
______________________________________ 
According to the present invention, as described above, there can be 
achieved a so-called four-unit zoom lens in which the lateral aberration 
of a focal length changing lens unit at the wide angle end, the F-number 
of a front lens unit, the lens arrangement of a variator, etc. are 
appropriately set and at least one aspherical surface is provided on at 
least one lens surface satisfying 0.95&gt;hw/ht and 0.90&gt;hw/hz, where ht is 
the maximum incidence height of an on-axis light beam in the front lens 
unit, hw is the maximum incidence height of an off-axis light beam of a 
maximum angle of view at the wide angle end, and hz is the maximum 
incidence height of an off-axis light beam of a maximum angle of view at a 
zoom position at a variable power ratio Z.sup.1/4, whereby the spherical 
aberration near the telephoto end is reduced and further, by an aspherical 
surface being provided in the variator, the changing of distortion on the 
wide angle side is corrected and furthermore, the changing of astigmatism, 
coma and chromatic aberration resulting from a focal length change is 
well-balancedly corrected and which has high optical performance over an 
entire variable power range and has a large aperture, a wide angle and a 
high variable power ratio of F-number 1.7 or so at the wide angle end, a 
wide angle end angle of view 2.omega.=57.degree.-70.degree. and a variable 
power ratio 12-35.