Zoom lens system
View Patent ↗A zoom lens system is disclosed. The zoom lens system forms a final image of an object and a first intermediate real image between the object and the final image. The zoom lens system includes a first optical unit located between the object and the first intermediate real image. The first optical unit comprises at least one optical subunit which is moved to change the size (magnification) of the first intermediate real image. The zoom lens system also includes a second optical unit located between the first intermediate real image and the final image, at least a portion of which is moved to change the size (magnification) of the final image. The zoom lens system provides a wide zoom range of focal lengths with continuous zooming between the focal lengths.
1. An infrared zoom lens system for forming a final image of an object, said system having an object side and an image side and forming a first intermediate real image between the object and the final image, said system comprising:
a first lens group including at least two lens elements and located between the object and the first intermediate real image, said first lens group comprising at least one zoom subgroup which is moved to change the size (magnification) of the first intermediate real image;
a second lens group including at least two lens elements and located between the first intermediate real image and the final image, at least a portion of which is moved to change the size (magnification) of the final image; and
an optical stop located between the intermediate image and the final image;
wherein off-axis field beam chief rays first cross an optical axis of the infrared zoom lens system on the object side of the intermediate image and then cross the optical axis again at the optical stop; and
wherein a ratio of a maximum off-axis field beam rim ray to an axial field beam rim ray at a lens surface of the first lens group adjacent to object space at a longest focal length of the zoom lens system is less than about 1.25.
2. The infrared zoom lens system as recited in claim 1 , wherein the optical stop is located between a last element surface of the second lens group and the final image.
3. The infrared zoom lens system as recited in claim 1 , wherein the infrared zoom lens system is capable of forming the final image from received radiation in the range of about 3-5 microns.
4. The infrared zoom lens system as recited in claim 1 , wherein the first lens group comprises five lens elements and the second lens group comprises five lens elements.
5. The infrared zoom lens system as recited in claim 1 , wherein the first lens group and the second lens group comprise a seven group system with one axially stationary lens subgroup and six axially movable zoom subgroups.
6. The infrared zoom lens system as recited in claim 1 , wherein the first lens group comprises three zoom subgroups and the second lens group comprises three zoom subgroups.
7. The infrared zoom lens system as recited in claim 1 , wherein the first lens group comprises one axially stationary lens subgroup.
8. The infrared zoom lens system as recited in claim 1 , wherein the lens elements include one or more germanium lens elements and one or more silicon lens elements.
9. The infrared zoom lens system as recited in claim 1 , wherein at least one of the lens elements includes an aspheric surface.
10. The infrared zoom lens system as recited in claim 5 , wherein the first lens group comprises a first lens subgroup of positive power, a first zoom subgroup of negative power, a second zoom subgroup of positive power, and a third zoom subgroup of positive power, and the second lens group comprises a fourth zoom subgroup of negative power, a fifth zoom subgroup of negative power, and a sixth zoom subgroup of positive power.
11. An infrared zoom lens system for forming a final image of an object, said system having an object side and an image side and forming a first intermediate real image between the object and the final image, said system comprising:
a first lens group including a first five lens elements and located between the object and the first intermediate real image, said first lens group comprising at least one zoom subgroup which is moved to change the size (magnification) of the first intermediate real image;
a second lens group including a second five lens elements and located between the first intermediate real image and the final image, at least a portion of which is moved to change the size (magnification) of the final image; and
an optical stop located between the intermediate image and the final image;
wherein off-axis field beam chief rays first cross an optical axis of the infrared zoom lens system on the object side of the intermediate image and then cross the optical axis again at the optical stop;
wherein a ratio of a maximum off-axis field beam rim ray to an axial field beam rim ray at a lens surface of the first lens group adjacent to object space at a longest focal length of the zoom lens system is less than about 1.25; and
wherein lens element surfaces, a location of an object on the object side identified as (Object), a location of the optical stop identified as (Stop), a location of the final image identified as (Image), radii of corresponding surfaces, distances from one surface to a next surface, material between a corresponding surface and the next surface, and a maximum diametric diameter of light rays passing through the corresponding surface have the following order, relationships and characteristics:
Radius of
Thickness or
Aperture
Sub-
Zoom
Curvature
Separation
Refractive
Diameter
Item
Group
Group
Surface
Position
(mm)
(mm)
Material
(mm)
S0 (Object)
Infinity
25.000
120
151
152
S1
All
215.343
28.544
Silicon
317.642
S2
Z1
269.106*
9.864
308.262
Z2
57.468
Z3
108.517
Z4
117.957
Z5
132.937
Z6
135.615
122
151
153
S3
All
637.888
9.000
Germanium
187.169
S4
All
247.226
11.642
174.123
124
151
153
S5
All
228.929
8.000
Silicon
166.617
S6
Z1
161.278
244.587
157.148
Z2
220.842
Z3
150.487
Z4
74.335
Z5
22.911
Z6
11.974
126
151
154
S7
All
288.682
15.448
Silicon
176.490
S8
Z1
1321.765*
212.856
174.473
Z2
233.828
Z3
270.854
Z4
362.883
Z5
443.606
Z6
460.309
128
151
155
S9
All
83.756*
11.053
Silicon
105.651
S10
Z1
159.357
160.888
103.666
Z2
115.791
Z3
97.933
Z4
72.886
Z5
28.278
Z6
20.171
S11 (dummy)
Z1
Infinity
74.210
Z2
46.803
Z3
3.191
Z4
3.253
Z5
57.219
Z6
19.714
130
156
157
S12
All
−32.997
12.500
Silicon
29.867
S13
Z1
−45.308
1.830
36.698
Z2
29.317
Z3
74.625
Z4
73.197
Z5
0.800
Z6
1.897
132
156
158
S14
All
−28.877
10.206
Germanium
23.882
S15
Z1
−44.286
1.917
30.694
Z2
0.995
Z3
0.100
Z4
0.926
Z5
4.846
Z6
18.907
134
156
159
S16
All
6208.244
13.998
Germanium
37.741
S17
All
264.338
0.400
40.076
136
S18
All
171.855
11.452
Silicon
41.269
S19
All
−84.226
0.400
42.354
138
S20
All
−128.685
1.000
Silicon
41.072
S21
Z1
−156.416*
1.254
41.075
Z2
1.696
Z3
0.750
Z4
1.699
Z5
15.734
Z6
38.441
S22 (Stop)
All
Infinity
79.221
S23 (Image)
All
Infinity
0.000.