Large-aperture three-lens objective with aspherical-surfaces

• US 5,251,063 A
• Filed: 10/16/1992
• Issued: 10/05/1993
• Est. Priority Date: 10/16/1991
• Status: Expired due to Fees

• Current Assignee: Bodenseewerk Gerätetechnik Gmbh
• Original Assignee: Bodenseewerk Gerätetechnik Gmbh
• Inventors: Baumann, Rainer
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/961,815
• Time in Patent Office: 354 Days
• Field of Search: 359/355, 359/356, 359/357, 359/708, 359/709, 359/716, 359/785
• US Class Current: 359/355
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 9/16 all the components being simple

Abstract

A three-lens objective has the following characteristics: A front lens consists of a first material of relatively low dispersion, a median lens consists of a second material of relatively larger dispersion, and a rear lens consists of a material of relatively low dispersion. The front lens has positive power, the median lens has negative power, and the rear lens has positive power. The spacing between front lens and median lens is substantially smaller than the distance between median lens and rear lens. Each of the lenses has at least one aspherical surface.

Claims

1. A three-lens objective comprising three lenses and having a relatively short and a relatively long back or front focal length, respectively, each of said lenses having a front surface facing an object and a rear surface facing an image of said object, wherein

a front one of said lenses consists of a first material of relatively low dispersion, a median one of said lenses consists of a second material of relatively larger dispersion, and a rear one of said lenses consists of a material of relatively low dispersion,

said front lens has positive power, said median lens has negative power, and said rear lens has positive power,

the spacing between said front lens and said median lens is substantially smaller than the distance between said median lens and said rear lens, and

each of said lenses has at least one aspherical surface.

2. A three-lens objective as claimed in claim 1, wherein each of said lenses has one aspherical surface and one spherical surface.

3. A three-lens objective as claimed in claim 2, wherein each lens has an aspherical front surface and a spherical rear surface.

4. A three-lens objective as claimed in claim 3, wherein the conic constant of said aspherical surface of said front lens is smaller than -0.01, the conic constant of said aspherical surface of said median lens is smaller than -5, and the conic constant of said aspherical surface of said rear lens is smaller than -0.1.

5. A three-lens objective as claimed in claim 1, wherein said aspherical surfaces are pure conic section surfaces of revolution.

6. A three-lens objective as claimed in claim 1, wherein the two positive power lenses have a bending towards the longer one of the back or front focal lengths, respectively.

7. A three-lens objective as claimed in claim 1, wherein the materials of said front lens and of said rear lens are identical.

8. A three-lens objective as claimed in claim 7 for use in the infrared spectral range between the wavelengths of 3 μ

m and 5.5 μ

m, wherein said front lens and said rear lens consist of silicon and the median lens consists of germanium.

9. A three-lens objective as claimed in claim 7 for use in the infrared spectral range between the wavelengths of 8μ

and 12μ

, wherein said front lens and said rear lens consist of germanium and said median lens consists of zinc selenide.

10. A three-lens objective as claimed in claim 7, for use in the infrared spectral range between the wavelengths of 8μ

and 12μ

, wherein said front lens and said rear lens consist of germanium and said median lens consists of zinc sulfide.

11. A three-lens objective as claimed in claim 1, wherein the smallest cross sectional area of all imaging light beams is located behind the rear lens, whereby an aperture stop is placed at this location behind the rear lens without causing vignetting.

12. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 1 ______________________________________ Lens Data Aperture Surface Radius Thickness Radius Material ______________________________________ 1 -- -- 25.576769 Air 2 95.775000 5.700000 25.576769A Si 3 362.560000 9.800000 25.039522 Air 4 -115.480000 4.300000 21.96955 Ge 5 -296.400000 40.000000 22.070983 Air 6 39.525000 5.000000 15.410790 Si 7 40.973000 41.479150 13.972384 Air 8 -- -- 4.519556 Air ______________________________________ Aspheric Surface Data ______________________________________ 2 CC -1.260288 AD -2.10940E - AE -4.82038E - 08 11 4 CC -12.095072 AD 2.05607E - AE -3.62017E - 07 11 6 CC -0.984138 AD 8.95639E - AE -2.08363E - 07 11 ______________________________________ Refractive Indices Abbe- Dispersion Surface Material n1 n2 n3 Number V ______________________________________ 1 Air -- -- -- -- 2 Si 3.424332 3.429186 3.421818 329.041382 3 Air -- -- -- -- 4 Ge 4.021400 4.034114 4.014581 154.677323 5 Air -- -- -- -- 6 Si 3.424332 3.429186 3.421818 329.041382 7 Air -- -- -- -- 8 Air -- -- -- -- ______________________________________

13. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 2 ______________________________________ Lens Data Aperture Srf Radius Thickness Radius Material ______________________________________ 1 -- -13.003369 13.847083 Air 2 40.973000 4.000000 15.493000 Si 3 139.240000 6.450000 14.923000 Air 4 -34.974000 2.000000 10.586000 Ge 5 -102.180000 -- 10.609000 Air 6 -- -- 10.444000 7 -- 13.300000 10.444000 Air 8 23.544000 3.000000 l0.324000 Sil 9 35.481000 3.500000 9.695000 Air 10 -- 3.000000 8.999000 Si Scanner 11 -- .sup. 2.197175V 8.728000 Air 12 -- 2.000000 8.005000 Ge Window 13 -- 2.000000 7.851000 Air 14 -- -- 7.204000 15 -- 6.000000 7.204000 Air 16 -- -- 5.263000 17 -- -- 5.263000 Air 18 -- 1.000000 5.263000 Si 19 -- 2.000000 5.173000 Air 20 -- -- 4.526000 Air ______________________________________ Aspheric Surface Data ______________________________________ 2 CC -0.974975 AD -3.32409E - AE 2.23708E - 07 11 4 CC -10.283235 AD -7.33080E - AE 2.38799E - 07 09 8 CC -0.989312 AD -3.82908E - AE 6.37996E - 06 10 ______________________________________ Refractive Indices Abbe-Dispersion Srf Material Nl N2 N3 Number V ______________________________________ 1 Air -- -- -- -- 2 Si 3.423380 3.426478 3.421153 455.143820 3 Air -- -- -- -- 4 Ge 4.0l8807 4.027057 4.012839 212.321165 5 Air -- -- -- -- 6 1.000000 1.000000 1.000000 -- 7 Air -- -- -- -- 8 Si 3.423380 3.426478 3.421153 455.143820 9 Air -- -- -- -- 10 Si 3.423380 3.426478 3.421153 455.143820 11 Air -- -- -- -- 12 Ge 4.018807 4.027057 4.012839 212.321165 13 Air -- -- -- -- 14 1.000000 1.000000 1.000000 -- 15 Air -- -- -- -- 16 1.000000 1.000000 1.000000 -- 17 Air -- -- -- -- 18 Si 3.423380 3.426478 3.421153 455.143820 19 Air -- -- -- -- 20 Air -- -- -- -- ______________________________________

14. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 3 ______________________________________ Lens Data Aperture Srf Radius Thickness Radius Glass Notes ______________________________________ 1 -- -177.23730 4l.66667 Air 2 70.01694 7.47307 55.00000 Ge 1. Lens 3 71.50233 27.00000 52.43139 S Air 4 -517.42425 5.63758 52.00000 ZnSe 2. Lens 5 -743.63318 52.44256 52.00000 Air 6 85.02567 6.55532 32.00000 Ge 3. Lens 7 112.74740 6.74923 31.00000 Air 8 -- 50.38182 22.27019A Air 9 -- -- 10.98252 Air Focal Plane ______________________________________ Special and Aspheric Data ______________________________________ 2 CC -0.06772 4 CC -16.82474 6 CC -0.28703 ______________________________________ Refractive Indices Srf Glass Nl N2 N3 V ______________________________________ 1 Air -- -- -- -- 2 Ge 4.00420 4.00560 4.00190 811.81345 3 Air -- -- -- -- 4 ZnSe 2.41220 2.41726 2.39296 58.12443 5 Air -- -- -- -- 6 Ge 4.00420 4.00560 4.00190 811.81345 7 Air -- -- -- -- 8 Air -- -- -- -- 9 Air -- -- -- -- ______________________________________

15. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 4 ______________________________________ Lens Data Aperture Srf Radius Thickness Radius Glass Notes ______________________________________ l -- -156.29093 33.33333 Air 2 64.24548 7.47307 45.50000 Ge 1. Lens 3 65.75754 17.00000 42.74139 Air 4 -670.00482 5.63758 42.50000 ZnSe 2. Lens 5 -1105.21495 52.44256 42.50000 Air 6 74.24877 6.55532 23.50000 Ge 3. Lens 7 89.57195 4.00000 22.00000 Air 8 -- 50.38182 17.816l5A Air 9 -- -- 8.78602 Air Focal Plane ______________________________________ Special and Aspheric Data ______________________________________ 2 CC -0.06463 4 CC -91.21630 6 CC -0.37256 ______________________________________ Refractive Indices Srf Glass Nl N2 N3 V ______________________________________ 1 Air -- -- -- -- 2 Ge 4.00420 .4.00560 4.00190 811.81345 3 Air -- -- -- -- 4 ZnSe 2.41220 2.41726 2.39296 58.12443 5 Air -- -- -- -- 6 Ge 4.00420 4.00560 4.00190 811.81345 7 Air -- -- -- -- 8 Air -- -- -- -- 9 Air -- -- -- -- ______________________________________

16. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 5 ______________________________________ Lens Data Aperture Srf Radius Thickness Radius Glass Notes ______________________________________ 1 -- -139.39410 33.08307 Air 2 66.70624 7.47378 44.00000 Ge 1. Lens 3 68.69355 15.00000 41.00000 Air 4 -2421.543l1 5.63812 41.00000 ZnS 2. Lens 5 -4863.26768 52.44758 40.00000 Air 6 10l.51108 6.55595 22.00000 Ge 3. Lens 7 137.03175 54.38703 18.69937A Air 8 -- -- 8.75690 Air Focal Plane ______________________________________ Special and Aspheric Data ______________________________________ 2 CC -0.06888 4 CC -489.14951 6 CC -0.78014 ______________________________________ Refractive Indices Srf Glass Nl N2 N3 V ______________________________________ 1 Air -- -- -- -- 2 Ge 4.00420 4.00560 4.00190 811.81345 3 Air -- -- -- -- 4. ZnS 2.21230 2.22280 2.17000 22.96014 5 Air -- -- -- -- 6 Ge 4.00420 4.00560 4.00190 811.81345 ______________________________________

17. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 6 ______________________________________ Lens Data Aperture Srf Radius Thickness Radius Glass Notes ______________________________________ l -- -42.32215 41.66667 Air 2 69.08962 7.47307 45.50000 Ge 1. Lens 3 70.49711 27.00000 41.52428 Air 4 -467.15591 5.63758 38.00000 ZnSe 2. Lens 5 -703.9l399 52.44256 33.23295A Air 6 80.92787 6.55532 31.33321 Ge 3. Lens 7 105.26772 6.74923 29.36970 Air 8 -- 50.38182 22.27019 Air 9 -- -- 10.98252 Air Focal Plane ______________________________________ Special and Aspheric Data ______________________________________ 2 CC -0.08201 4 CC -52.88740 6 CC -0.32580 ______________________________________ Refractive Indices Srf Glass Nl N2 N3 V ______________________________________ 1 Air -- -- -- -- 2 Ge 4.00420 4.00560 4.00190 811.81345 3 Air -- -- -- -- 4 ZnSe 2.41220 2.41726 2.39296 58.l2443 5 Air -- -- -- -- 6 Ge 4.00420 4.00560 4.00190 811.81345 7 Air -- -- -- -- 8 Air -- -- -- -- 9 Air -- -- -- -- ______________________________________

18. A three-lens objective as claimed in claim 1 and having the following data:

space="preserve" listing-type="tabular"> TABLE 7 ______________________________________ Lens Data Aperture Srf Radius Thickness Radius Glass Notes ______________________________________ 1 -- -24.76890 33.33333 Air 2 75.26509 7.47306 34.33407 Ge 1. Lens 3 80.17272 15.00457V 32.03975 Air 4 7827.23829 5.63758 29.96496 ZnS 2. Lens 5 2903.51135 52.44256 29.29838A Air 6 152.32088 6.55532 24.63244 Ge 3. Lens 7 260.72381 54.38182 23.76313 Air 8 -- -- 8.40445 Air Focal Plane ______________________________________ Special and Aspheric Data ______________________________________ 2 CC -0.08439 4 CC -1.8823E + 04 6 CC -2.47048 ______________________________________ Refractive Indices Srf Glass N1 N2 N3 V ______________________________________ 1 Air -- -- -- -- 2 Ge 4.00420 4.00560 4.00190 811.81345 3 Air -- -- -- -- 4 ZnS 2.21230 2.22280 2.17000 22.96014 5 Air -- -- -- -- 6 Ge 4.00420 4.00560 4.00190 811.81345 7 Air -- -- -- -- 8 Air -- -- -- -- ______________________________________