Zoom lens device with four lens unit

A zoom lens device including a total of four lens units, which are in order of lens units from the lens unit closest to an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having either a positive or negative refractive power, with a stop provided between the second lens unit and the fourth lens unit. The first lens unit comprises two lenses, a positive lens and a negative lens. The second lens unit comprises one or two negative lenses and one positive lens. The third lens unit comprises at least one positive lens and one negative lens. When magnification is being changed from a wide angle end to a telephoto end, the first, third, and fourth lens units are moved toward the object side such that the distance between the first lens unit and second lens unit increases, the distance between the second lens unit and the third lens unit decreases, and the distance between the third lens unit and the fourth lens unit changes. The zoom lens device has a magnification change-over ratio of about 2 to 3.5, a smaller overall length of the lens system, and provides excellent optical performance over the entire magnification change-over range.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 to 7 are cross sections of lens unit systems at the wide angle end 
in Numerical Examples 1 to 7, respectively, in accordance with the present 
invention. 
FIGS. 8A-8D, 9A-9D, and 10A-10D illustrate diagrams showing aberrations at 
the wide angle end, an intermediate state between the wide angle end and 
the telephoto end, and the telephoto end, respectively, in Numerical 
Example 1 in accordance with the present invention. FIGS. 11A-11D, 
12A-12D, and 13A-13D illustrate diagrams showing aberrations at the wide 
angle end, an intermediate state between the wide angle end and the 
telephoto end, and the telephoto end, respectively, in Numerical Example 2 
in accordance with the present invention. FIGS. 14A-14D, 15A-15D, and 
16A-16D illustrate diagrams showing aberrations at the wide angle end, an 
intermediate state between the wide angle end and the telephoto end, and 
the telephoto end, respectively, in Numerical Example 3 in accordance with 
the present invention. FIGS. 17A-17D, 18A-18D, and 19A-19D illustrate 
diagrams showing aberrations at the wide angle end, an intermediate state 
between the wide angle end and the telephoto end, and the telephoto end, 
respectively, in Numerical Example 4 in accordance with the present 
invention. FIGS. 20A-20D, 21A-21D, and 22A-22D illustrate diagrams showing 
aberrations at the wide angle end, an intermediate state between the wide 
angle end and the telephoto end, and the telephoto end, respectively, in 
Numerical Example 5 in accordance with the present invention. FIGS. 
23A-23D, 24A-24D, and 25A-25D illustrate diagrams showing aberrations at 
the wide angle end, an intermediate state between the wide angle end and 
the telephoto end, and the telephoto end, respectively, in Numerical 
Example 6 in accordance with the present invention. FIGS. 26A-26D, 
27A-27D, and 28A-28D illustrate diagrams showing aberrations at the wide 
angle end, an intermediate state between the wide angle end and the 
telephoto end, and the telephoto end, respectively, in Numerical Example 7 
in accordance with the present invention. 
Referring to the figures (e.g., FIGS. 1 through 7), L1 denotes a first lens 
unit with a positive refractive power, L2 denotes a second lens unit with 
a negative refractive power, L3 represents a third lens unit with a 
positive refractive power, L4 denotes a fourth lens unit with a positive 
refractive power, SP denotes a stop which is disposed between the second 
lens unit and the fourth lens unit and, in the present invention, 
forwardly of the third lens unit. FP denotes a flare cut stop which is 
disposed between the third lens unit and the fourth lens unit. IP denotes 
the image plane. 
In the present embodiment, when magnification changes from the wide angle 
end to the telephoto end, the first, third, and fourth lens units move 
toward the object side such that the distance between the first and second 
lens units is increased, the distance between the second and third lens 
units is decreased, and the distance between the third and fourth lens 
units is decreased. The stop SP and the flare cut stop FP move integrally 
with the third lens unit. Focusing is performed by moving the second lens 
unit. 
In the Numerical Examples 1 to 5 of FIGS. 1 to 5, respectively, the first 
lens unit L1 comprises two lenses, a meniscus negative lens and a meniscus 
positive lens. The meniscus negative lens and the meniscus positive lens 
have their convex surfaces facing the object side. The second lens unit L2 
comprises three lenses, a meniscus negative lens, a negative lens, and a 
meniscus positive lens. The meniscus negative lens has its convex surface 
facing the object side, the negative lens is a biconcave lens, and the 
meniscus positive lens has its convex surface facing the object side. The 
third lens unit L3 comprises two lenses which may be a biconvex positive 
lens and a negative lens, or a meniscus negative lens with its convex 
surface facing the object side and a positive lens. The fourth lens unit 
L4 may comprise one lens which is a meniscus positive lens having its 
convex surface facing the image side, or two lenses, one of which is a 
biconvex positive lens and the other of which is a biconcave negative 
lens. 
In Numerical Example 6 of FIG. 6, the first lens unit L1 comprises two 
lenses, a meniscus negative lens with its convex surface facing the object 
side, and a meniscus positive lens with its convex surface facing the 
object side. The second lens unit comprises two lenses, a biconcave 
negative lens and a meniscus positive lens with its convex surface facing 
the object side. The third lens unit comprises two lenses, a biconvex 
positive lens and a meniscus negative lens with its convex surface facing 
the image plane side. The fourth lens unit comprises one lens which is a 
meniscus positive lens having its convex surface facing the image plane 
side. 
In Numerical Example 7 of FIG. 7, the first lens unit comprises two lenses, 
a positive lens and a meniscus negative lens with its convex surface 
facing the object side. The second lens unit comprises two lenses, a 
biconcave negative lens and a meniscus positive lens with its convex 
surface facing the object side. The third lens unit comprises two lenses, 
a biconvex positive lens and a meniscus negative lens with its convex 
surface facing the image plane side. The fourth lens unit comprises one 
lens which is a meniscus positive lens with its convex surface facing the 
image plane side. 
Accordingly, in the present invention, a predetermined magnification 
change-over ratio is obtained, and the entire lens system is reduced in 
size as a result of constructing the lens units in a particular manner. 
The first lens unit is reduced in size by constructing it out of two 
lenses with a predetermined shape. The second lens unit is constructed 
from two or three lenses with a predetermined shape in order to form the 
portion of the second lens unit on the optical axis thinner and reduce the 
size of the first lens unit. 
More specifically, in general, the outer diameter of a lens unit can be 
made smaller by placing the lens unit closer to a stop. In the present 
invention, in order to reduce changes in the f-number which occur as 
magnification changes from the wide angle end to the telephoto end, the 
stop is placed away from the second lens unit and towards the image plane 
side, at the wide angle side. Constructing the second lens unit as 
described above and making the portion of the lens unit on the optical 
axis thinner decreases the distance between the first lens unit and the 
stop, thus decreasing the outer diameter of the first lens unit. A 
decrease in the outer diameter allows sufficient edge thickness to be 
provided for the positive lens in the first lens unit, resulting in an 
even thinner lens unit. 
Formation of the third lens unit with a positive lens and a negative lens 
provides good optical performance because chromatic aberration produced by 
the positive lens is canceled by the negative lens. 
When magnification changes from the wide angle end to the telephoto end, 
the stop is brought closer to the second lens unit; therefore placing the 
stop at the wide angle side away from the second lens unit and towards the 
image plane side is effective in further controlling changes in the 
f-number which occur as the magnification changes. Bringing the stop and 
the second lens unit closer together at the telephoto end makes it 
possible to control the on-axis light beams diverging from the second lens 
unit using a relatively small diameter stop, so that the f-number at the 
wide angle side is not set at a value causing too much brightness. 
According to the present embodiment, the stop is disposed close to or 
within the third lens unit, whereby the first and fourth lens units are 
formed with proper outer diameters. In addition, the stop and the third 
lens unit are integrally moved when the magnification is being changed in 
order to simplify the lens barrel structure. 
According to the present embodiment, when magnification is being changed, 
the distance between the third and fourth lens units is changed so that 
the non-axial light beams leaving the third lens unit passes the fourth 
lens unit at different heights at the wide angle end and at the telephoto 
end. Consequently, distortion is effectively corrected at the wide angle 
end and at the telephoto end. When magnification is being changed from the 
wide angle side to the telephoto side, the distance between the third and 
fourth lens units is decreased in order to correct distortion even more 
effectively. 
According to the present embodiment, it is preferable that the fourth lens 
unit has a positive refractive power or a weak negative refractive power, 
whereby at the wide angle end sufficient back focus can be obtained. When 
the fourth lens unit has a very strong negative refractive power, the 
principle point of the entire lens system shifts toward the object side, 
thus making it difficult to obtain a sufficient back focus. 
According to the present embodiment, the four lens units having the 
aforementioned refractive powers and constructions, are moved as described 
above when the magnification is being changed, and the refractive powers 
of the first and second lens units are set such that Conditions (1) and 
(2) are satisfied, respectively. Therefore, each of the lens units takes a 
proper part in changing the magnification, thereby making it easier to 
achieve high magnification changes and properly correct aberrations over 
the entire magnification change-over range. 
A description will now be given of the technical meaning of aforementioned 
Conditions (1) and (2). 
Condition (1) specifies the focal length of the first lens unit. When the 
upper limit is exceeded, the zoom lens device cannot function 
satisfactorily at the telephoto side, making it difficult to set the 
f-number of the zoom lens device at a value which provides brightness. 
When the focal length is less than the lower limit, it becomes difficult 
to correct spherical aberration and positive distortion at the telephoto 
side with a few lenses. 
In the present embodiment, the optical performance of the zoom lens device 
is improved when the f1/fw value range of Condition (1) is limited to the 
f1/fw value range of Condition (1a): 
EQU 1.9&lt;f1/fw&lt;3.0 (1a) 
Condition (2) specifies the focal length range of the second lens unit. 
When the upper limit is exceeded, it becomes difficult to continue 
performing high magnification changes. When the -f2/fw value is less than 
the lower limit, it becomes difficult to properly correct negative 
distortion at the wide angle side with a few lenses. 
In the present embodiment, the optical performance of the zoom lens device 
is improved when the -f2/fw value range of Condition (2) is limited to the 
-f2/fw value range of Condition (2a): 
EQU 0.44&lt;-f2/fw&lt;1.0 (2a) 
In the above-described embodiment, when the lens device is a zoom-type lens 
device whose lens units are properly constructed, the overall length of 
the lens system is reduced, with a wider angle of view at the wide angle 
end. In addition, the magnification change-over ratio can be set within a 
range of from about 2 to 3.5. Further aberration changes which occur as 
the magnification changes can be properly corrected, whereby high optical 
performance is provided over the entire magnification change-over range. 
In the present embodiment, the optical performance of the zoom lens is 
improved, and the overall length thereof is decreased, when at least one 
of the following conditions is satisfied: 
(A1) The third lens unit comprises a positive lens and a negative lens, and 
has an f3/fw value satisfying Condition (3): 
EQU 0.5&lt;f3/fw&lt;2.0 (3) 
where f3 is the focal length of the third lens unit. 
In the present invention, the various aberrations, particularly chromatic 
aberration, and the overall size of the lens system are reduced as a 
result of making the f3/fw value of the third lens unit satisfy Condition 
(3). 
When the upper limit of Condition (3) is exceeded, the third lens unit must 
be moved by a larger amount during magnification changes, resulting in a 
larger overall size of the lens system. When the f3/fw value is less than 
the lower limit, it becomes difficult to properly correct, in particular, 
spherical aberration. 
In the invention, it is preferable that the range of Condition (3) be 
limited to the range set in Condition (3a): 
EQU 0.6&lt;f3/fw&lt;1.8 (3a) 
(A2) Condition (4) is satisfied: 
EQU f4/fw&lt;20 (4) 
where f4 is the focal length of the fourth lens unit. 
When Condition (4) is satisfied, sufficient back focus is provided at the 
wide angle end, and negative distortion at the wide angle side is properly 
corrected. 
It is preferable that the f4/fw value range of Condition (4) be limited to 
the value range set in Condition (4a): 
EQU 1.2&lt;f4/fw&lt;20 (4a) 
When the fourth lens unit comprises one positive lens, it is preferable 
that the f4/fw value range of Condition (4) is limited to the value range 
set in Condition (4b) below: 
EQU 3.0&lt;f4/fw&lt;20 (4b) 
(A3) The fourth lens unit comprises a positive lens, or two lenses, one of 
which is positive and the other of which is negative; in addition, the 
fourth lens unit has at least one surface thereof being aspherical. 
When Condition (A3) is satisfied, the overall size of the lens system is 
reduced, and negative distortion at the wide angle end is properly and 
easily corrected. 
(A4) The second lens unit is moved to focus an object. 
In the lens construction of the present invention, the refractive power of 
the second lens unit is stronger than that of other lens units. Therefore, 
the use of the second lens unit to bring an object into focus reduces the 
amount of movement involved during focusing, thereby reducing the size of 
the lens-barrel structure. In addition, compared to the common focusing 
method in which the first lens unit is moved for focusing, this focusing 
method is advantageous in that the front lens diameter is smaller, and in 
that close-distance shooting is possible. 
A description will now be given of the numerical examples of the present 
invention. In the numerical examples, Ri represents the radius of 
curvature of the ith lens surface from the object; Di represents the 
thickness of the ith lens in order of lenses from the object and the air 
gap; and Ni and .nu.i represent the refractive index and the Abbe 
constant, respectively, of the ith lens in order of lenses from the 
object. Also, stop refers to stop SP and flare cutter refers to flare cut 
stop FP. 
Table 8 gives the relationship between the above-described conditions and 
the numerical examples. 
The aspherical shape is defined by the following formula: 
##EQU1## 
where the X-axis extends along the optical axis, the H-axis extends along 
a direction perpendicular to the optical axis, the direction of travel of 
light is defined as positive, R is the paraxial radius of curvature, and 
A, B, C, D, and E each represent aspherical coefficients. e-X represents 
10.sup.-x. 
______________________________________ 
(Numerical Example 1) 
______________________________________ 
F = 28.90 .about. 77.18 FN0 = 4.60 .about. 5.88 2.omega. = 73.6.degree. 
.about. 31.3.degree. 
R1 = 33.94 D1 = 1.50 N1 = 1.84665 
.nu. 1 = 23.8 
R2 = 25.51 D2 = 0.22 
R3 = 26.03 D3 = 7.00 N2 = 1.69679 
.nu. 2 = 55.5 
R4 = 127.30 
D4 = variable 
R5 = 89.22 D5 = 1.10 N3 = 1.71299 
.nu. 3 = 53.8 
R6 = 10.93 D6 = 4.70 
R7 = -107.83 
D7 = 1.00 N4 = 1.71299 
.nu. 4 = 53.8 
R8 = 22.92 D8 = 0.12 
R9 = 16.59 D9 = 3.05 N5 = 1.76182 
.nu. 5 = 26.5 
R10 = 93.07 
D10 = variable 
R11 = stop D11 = 1.00 
R12 = 15.64 
D12 = 2.85 N6 = 1.66671 
.nu. 6 = 48.3 
R13 = -23.93 
D13 = 0.03 
R14 = -24.07 
D14 = 1.00 N7 = 1.80518 
.nu. 7 = 25.4 
R15 = 65.66 
D15 = 5.43 
R16 = flare 
D16 = variable 
cutter 
R17 = 20.57 
D17 = 3.55 N8 = 1.67790 
.nu. 8 = 55.3 
R18 = -29.37 
D18 = 0.12 
R19 = -54.19 
D19 = 1.20 N9 = 1.71999 
.nu. 9 = 50.3 
R20 = 25.73 
D20 = variable 
______________________________________ 
TABLE 1 
______________________________________ 
Focal length 28.90 46.89 77.18 
Variable Interval 
D4 2.11 10.57 20.50 
D10 15.24 7.71 1.50 
D16 2.50 1.84 1.33 
D20 0.00 8.18 14.91 
______________________________________ 
Aspherical surface coefficient 18th surface (R18) 
A = 0 B = 9.156e - 05 C = 4.162e - 08 D = 0 E = 0 
______________________________________ 
______________________________________ 
(Numerical Example 2) 
______________________________________ 
F = 28.90 .about. 77.19 FN0 = 4.57 .about. 5.88 2.omega. = 73.6.degree. 
.about. 31.3.degree. 
R1 = 36.17 D1 = 1.50 N1 = 1.84665 
.nu. 1 = 23.8 
R2 = 26.55 D2 = 0.18 
R3 = 27.01 D3 = 6.70 N2 = 1.71299 
.nu. 2 = 53.8 
R4 = 134.87 
D4 = variable 
R5 = 108.06 
D5 = 1.10 N3 = 1.71299 
.nu. 3 = 53.8 
R6 = 11.22 D6 = 4.73 
R7 = -133.04 
D7 = 1.00 N4 = 1.71299 
.nu. 4 = 53.8 
R8 = 25.37 D8 = 0.12 
R9 = 16.87 D9 = 3.00 N5 = 1.76182 
.nu. 5 = 26.5 
R10 = 78.12 
D10 = variable 
R11 = stop D11 = 0.50 
R12 = 18.89 
D12 = 3.15 N6 = 1.71999 
.nu. 6 = 50.3 
R13 = -18.17 
D13 = 0.15 
R14 = -17.41 
D14 = 1.00 N7 = 1.78472 
.nu. 7 = 25.7 
R15 = -949.72 
D15 = 4.88 
R16 = flare 
D16 = variable 
cutter 
R17 = -49.86 
D17 = 1.50 N8 = 1.49171 
.nu. 8 = 57.4 
R18 = -29.09 
D18 = variable 
______________________________________ 
TABLE 2 
______________________________________ 
Focal length 28.90 47.93 77.19 
Variable Interval 
D4 2.23 10.82 20.92 
D10 16.41 7.74 1.50 
D16 5.09 3.96 3.15 
D20 0.00 9.80 16.85 
______________________________________ 
Aspherical surface coefficient 18th surface (R18) 
A = 0 B = 6.365e - 05 C = 1.177e - 07 D = 5.752e - 09 
E = -2.328e - 11 
______________________________________ 
______________________________________ 
(Numerical Example 3) 
______________________________________ 
F = 28.90 .about. 77.18 FN0 = 4.42 .about. 5.88 2.omega. = 73.6.degree. 
.about. 31.3.degree. 
R1 = 36.31 D1 = 1.50 N1 = 1.84665 
.nu. 1 = 23.8 
R2 = 27.07 D2 = 0.16 
R3 = 27.55 D3 = 6.30 N2 = 1.71299 
.nu. 2 = 53.8 
R4 = 136.34 
D4 = variable 
R5 = 99.37 D5 = 1.10 N3 = 1.71299 
.nu. 3 = 53.8 
R6 = 11.26 D6 = 5.52 
R7 = -112.32 
D7 = 1.00 N4 = 1.71299 
.nu. 4 = 53.8 
R8 = 24.51 D8 = 0.12 
R9 = 17.19 D9 = 3.10 N5 = 1.76182 
.nu. 5 = 26.5 
R10 = 81.14 
D10 = variab1e 
R11 = stop D11 = 0 50 
R12 = 18.98 
D12 = 3.25 N6 = 1.71999 
.nu. 6 = 50.3 
R13 = -17.39 
D13 = 0.08 
R14 = -16.95 
D14 = 1.00 N7 = 1.78472 
.nu. 7 = 25.7 
R15 = -385.26 
D15 = 4.36 
R16 = flare 
D16 = variable 
cutter 
R17 = -63.59 
D17 = 2.00 N8 = 1.49171 
.nu. 8 = 57.4 
R18 = -32.42 
D18 = variable 
______________________________________ 
TABLE 3 
______________________________________ 
Focal length 28.90 47.20 77.18 
Variable Interval 
D4 2.34 11.19 21.57 
D10 15.15 7.47 1.50 
D16 5.18 4.09 3.43 
D18 0.00 9.54 17.08 
Aspherical surface coefficient 18th surface (R18) 
A = 0 B = 6.434e - 05 C = 3.126e - 07 D = -2.118e - 09 
E = 5.641e - 11 
______________________________________ 
______________________________________ 
(Numerical Example 4) 
______________________________________ 
F = 28.90 .about. 77.19 FN0 = 4.60 .about. 5.88 2.omega. = 73.6.degree. 
.about. 31.3.degree. 
R1 = 37.76 D1 = 1.50 N1 = 1.84665 
.nu. 1 = 23.8 
R2 = 29.12 D2 = 0.22 
R3 = 29.85 D3 = 6.20 N2 = 1.69679 
.nu. 2 = 55.5 
R4 = 140.64 
D4 = variable 
R5 = 103.86 
D5 = 1.10 N3 = 1.69679 
.nu. 3 = 55.5 
R6 = 11.59 D6 = 5.71 
R7 = -288.85 
D7 = 1.00 N4 = 1.77249 
.nu. 4 = 49.6 
R8 = 24.66 D8 = 0.2 
R9 = 17.41 D9 = 3.00 N5 = 1.80518 
.nu. 5 = 25 4 
R10 = 67.94 
D10 = variable 
R11 = stop D11 = 0.50 
R12 = 18.20 
D12 = 1.00 N6 = 1.84665 
.nu. 6 = 23.8 
R13 = 10.59 
D13 = 0.15 
R14 = 10.82 
D14 = 3.20 N7 = 1.69679 
.nu. 7 = 55.5 
R15 = -198.16 
D15 = 4.93 
R16 = flare 
D16 = variable 
cutter 
R17 = -26.41 
D17 = 2.00 N8 = 1.49171 
.nu. 8 = 57.4 
R18 = -19.80 
D18 = variable 
______________________________________ 
TABLE 4 
______________________________________ 
Focal length 28.90 47.98 77.19 
Variable Interval 
D4 2.54 12.17 23.46 
D10 16.44 7.64 1.50 
D16 6.72 5.37 4.55 
D18 0.00 10.36 17.58 
Aspherical surface coefficient 18th surface (R18) 
A = 0 B = 4.908e - 05 C = 2.401e - 07 D = 1.049e - 09 
E = 2.310e - 11 
______________________________________ 
______________________________________ 
(Numerical Example 5) 
______________________________________ 
F = 28.90 .about. 101.49 FN0 = 4.06 .about. 5.76 2.omega. = 73.6.degree. 
.about. 24.1.degree. 
R1 = 45.00 D1 = 1.50 N1 = 1.84665 
.nu. 1 = 23.8 
R2 = 32.33 D2 = 0.29 
R3 = 33.32 D3 = 7.40 N2 = 1.71299 
.nu. 2 = 53.8 
R4 = 319.48 
D4 = variable 
R5 = 66.32 D5 = 1.10 N3 = 1.69679 
.nu. 3 = 55.5 
R6 = 12.77 D6 = 5.92 
R7 = -46.98 
D7 = 1.00 N4 = 1.69679 
.nu. 4 = 55.5 
R8 = 28.07 D8 = 0.12 
R9 = 21.09 D9 = 2.70 N5 = 1.84665 
.nu. 5 = 23.8 
R10 = 85.54 
D10 = variable 
R11 = stop D11 = 0.40 
R12 = 18.74 
D12 = 3.30 N6 = 1.60311 
.nu. 6 = 60.7 
R13 = -34.45 
D13 = 1.25 
R14 = -25.89 
D14 = 1.00 N7 = 1.84665 
.nu. 7 = 23.8 
R15 = -234.67 
D15 = 8.02 
R16 = flare 
D16 = variable 
cutter 
R17 = 28.60 
D17 = 4.10 N8 = 1.67790 
.nu. 8 = 55.3 
R18 = -34.68 
D18 = 0.12 
R19 = -92.58 
D19 = 1.20 N9 = 1.77249 
.nu. 9 = 49.6 
R20 = 44.71 
D20 = variable 
______________________________________ 
TABLE 5 
______________________________________ 
Focal length 28.90 54.08 101.49 
Variable Interval 
D4 2.33 14.30 28.36 
D10 19.16 8.93 1.50 
D16 3.92 2.34 1.26 
D20 0.00 13.84 24.73 
Aspherical surface coefficient 5th surface (R5) 
A = 0 B = -3.606e - 06 C = -1.962e - 09 D = -1.383e - 11 
E = 2.549e - 14 
Aspherical surface coefficient 18th surface (R18) 
A = 0 B = 4.417e - 05 C = 1.414e - 08 D = 1.060e - 11 
E = 0 
______________________________________ 
______________________________________ 
(Numerical Example 6) 
______________________________________ 
F = 36.20 .about. 67.58 FN0 = 4.06 .about. 5.53 2.omega. = 61.7.degree. 
.about. 35.5.degree. 
R1 = 45.00 D1 = 1.50 N1 = 1.84665 
.nu. 1 = 23.8 
R2 = 30.18 D2 = 0.15 
R3 = 29.72 D3 = 6.00 N2 = 1.69679 
.nu. 2 = 55.5 
R4 = 106.57 
D4 = variable 
R5 = -228.24 
D5 = 1.10 N3 = 1.69679 
.nu. 3 = 55 5 
R6 = 11.38 D6 = 3.56 
R7 = 18.69 D7 = 3.10 N4 = 1.58306 
.nu. 4 = 30.2 
R8 = 41.35 D8 = variable 
R9 = stop D9 = 0.50 
R10 = 18.10 
D10 = 3.50 N5 = 1.69679 
.nu. 5 = 55.5 
R11 = -32.69 
D11 = 2.05 
R12 = -22.25 
D12 = 1.00 N6 = 1.84665 
.nu. 6 = 23.8 
R13 = -77.32 
D13 = 1.18 
R14 = flare 
D14 = variable 
cutter 
R15 = -40.1.0 
D15 = 2.00 N7 = 1.49170 
.nu. 7 = 57.4 
R16 = -32.80 
D16 = variable 
______________________________________ 
TABLE 6 
______________________________________ 
Focal length 36.20 48.66 67.58 
Variable Interval 
D4 5.31 12.81 20.70 
D8 15.66 10.33 4.98 
D14 6.59 5.94 5.62 
D16 0.00 5.01 10.46 
Aspherical surface coefficient 8th surface (R8) 
A = 0 B = -4.604e - 05 C = -4.013e - 08 D = 2.221e - 09 
E = 0 
Aspherical surface coefficient 16th surface (R16) 
A = 0 B = 7.417e - 05 C = 2.433e - 07 D = -2.215e - 09 
E = 0 
______________________________________ 
______________________________________ 
(Numerical Example 7) 
______________________________________ 
F = 36.20 .about. 67.59 FN0 = 4.60 .about. 5.62 2.omega. = 61.7.degree. 
.about. 35.5.degree. 
R1 = 42.42 D1 = 5.50 N1 = 1.69679 
.nu.1= 55.5 
R2 = 1137.89 
D2 = 0.10 
R3 = 497.78 
D3 = 1.50 N2 = 1.84665 
.nu.2 = 23.8 
R4 = 101.62 
D4 = variable 
R5 = -198.04 
D5 = 1.10 N3 = 1.69679 
.nu.3 = 55.5 
R6 = 11.81 D6 = 3.45 
R7 = 19.09 D7 = 3.10 N4 = 1.58306 
.nu.4 = 30.2 
R8 = 45.30 D8 = Variable 
R9 = stop D9 = 0.50 
R10 = 17.65 
D10 = 3.50 N5 = 1.69679 
.nu.5 = 55.5 
R11 = -34.72 
D11 = 2.74 
R12 = -21.40 
D12 = 1.00 N6 = 1.84665 
.nu.6 = 23.8 
R13 = -99.52 
D13 = 1.38 
R14 = flare 
D14 = variable 
cutter 
R15 = -49.01 
D15 = 2.00 N7 = 1.49171 
.nu.7 = 57.4 
R16 = -30.52 
D16 = variable 
______________________________________ 
TABLE 7 
______________________________________ 
Focal length 36.20 48.98 67.59 
Variable Interval 
D4 5.50 13.81 22.25 
D8 15.51 9.89 4.62 
D14 5.41 4.91 4.61 
D16 0.00 5.28 11.20 
______________________________________ 
Aspherical surface coefficient 8th surface (R8) 
A = 0 B = -3.917e - 05 C = -3.860e - 08 D = -1.616e - 09 
E = 0 
Aspherical surface coefficient 16th surface (R16) 
A = 0 B = 7.447e - 05 C = 2.276e - 07 D = 2.956e - 09 
E = 0 
______________________________________ 
TABLE 8 
______________________________________ 
Numerical Examples 
Condition 
1 2 3 4 5 6 7 
______________________________________ 
(1) f1/fw 
2.517 2.614 2.610 2.824 2.866 2.529 2.850 
(2) -f2/fw 
0.610 0.639 0.611 0.655 0.623 0.627 0.662 
(3) f3/fw 
1.309 1.010 0.974 0.992 1.499 0.763 0.808 
(4) f4/fw 
2.02 4.09 4.56 5.07 1.87 9.29 4.39 
______________________________________ 
As can be understood from the foregoing description, the zoom lens device 
comprises a total of four lens units which are properly constructed, so 
that the magnification change-over ratio is about 2 to 3.5, the shooting 
angle of view is wide at 60 to 75 degrees, the overall length of the lens 
system is reduced, and excellent optical performance is achieved over the 
entire magnification change-over range. 
While the present invention has been described with respect to what is 
presently considered to be the preferred embodiments, it is to be 
understood that the invention is not limited to the disclosed embodiments. 
To the contrary, the invention is intended to cover various modifications 
and equivalent arrangements included within the spirit and scope of the 
appended claims. The scope of the following claims is to be accorded the 
broadest interpretation so as to encompass all such modifications and 
equivalent structures and functions.