Wide band color correcting infrared lens system

• US 4,999,005 A
• Filed: 10/19/1988
• Issued: 03/12/1991
• Est. Priority Date: 10/19/1988
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cooper, Erwin E.
• Primary Examiner(s): Arnold, Bruce Y.
• Application Number:
  US07/259,822
• Time in Patent Office: 874 Days
• Field of Search: 350/1.1, 350/1.2, 350/1.3, 350/1.4, 350/501, 350/463, 350/474, 350/475, 362/326, 362/330, 362/331, 362/332, 362/333, 362/334
• US Class Current: 359/356
• CPC Class Codes: G02B 13/146 with corrections for use in multiple wavelength bands, such as infrared and visible light, e.g. FLIR systems

Abstract

An infrared refractive lens triplet having color correcting properties for radiation within the 3 to 13 micrometer spectral band. In certain embodiments of the invention the triplet is capable of simultaneously focusing radiation in the 3-5 micrometer and the 8-12 micrometer atmospheric windows for imaging about a single focal plane. In these embodiments one lens comprises germanium and another is formed of materials selected from the group consisting of sulfides and selenides of zinc and combinations thereof. A third lens is a glass characterized by chromic properties corresponding approximately to

40<V<46

with

V=(N.sub.D -1)/(N.sub.13 -N.sub.3),

wherein:

N_D is the refractive index at 8 micrometers,

N₁₃ is the refractive index at 13 micrometers, and

N₃ is the refractive index at 3 micrometers.

Claims

1. An optional system which comprises:

(a) an infrared refractive lens triplet having color correcting properties for radiation ranging from about 3.5 to about 12 micrometers, said triplet comprising;

(b) a first lens having chromic properties corresponding approximately to about 40 <

V <

46, where;

space="preserve" listing-type="equation">V =(N.sub.D -

     1)/(N.sub.13 -N.sub.3), ps

wherein, for said first lens glass;

N_D is the refractive index at 8 micrometers,

N₁₃ is the refractive index at 13 micrometers, and

N₃ is the refractive index at 3 micrometers;

(c) a second lens comprising germanium; and

(d) a third lens;

(e) said triplet of lenses being capable of simultaneously focusing radiation in the 3.5 -≡

micrometer and the 8 -12 micrometer range for imaging about a single focal plane.

2. The system of claim 1 wherein said triplet of lenses is capable of simultaneously focusing radiation throughout the 3.4 to 13 micrometer range for imaging upon a single focal plane.

3. The system of claim 1 wherein the first lens is a chalcogenide glass and said triplet is capable of simultaneously focusing radiation throughout the 3 to 12 micrometer range for imaging upon a single focal plane.

4. The system of claim 3 wherein:

the first lens is a positive element;

the second lens is a negative element having a power between 0.2 and 0.3 that of the first lens; and

the third lens is a negative element having a power between 0.5 and 0.6 that of the first lens.

5. The system of claim 4 wherein the power of the second lens is 0.24 that of the first lens and the power of the third lens is 0.52 that of the first lens.

6. The system of claim 5 wherein the triplet is ordered such that incoming radiation is first received by the first lens and last transmitted by the third lens.

7. The system of claim 3 wherein:

the first lens is a positive element;

the second lens is a negative element having a power between 0.40 and 0.48 that of the first lens; and

the third lens is a negative element having a power between 0.18 and 0.26 that of the first lens.

8. The system of claim 7 wherein the power of the second lens is 0.44 that of the first lens and the power of the third lens is 0.22 that of the first lens.

9. The system of claim 8 wherein the triplet is ordered such that incoming radiation is first received by the first lens and last transmitted by the third lens.

10. The system of claim 1 wherein the first lens is a ternary glass composition comprising germanium, antimony and selenium.

11. The system of claim 1 wherein the first lens glass predominantly comprises geranium, antimony and selenium according to the formula GE₂₈ Sb₁₂ Se₆₀.

12. The system according to claim 1 wherein the first lens is predominantly a ternary glass composition comprising germanium, arsenic and selenium.

13. The system of claim 1 wherein the first lens glass predominantly comprises germanium, arsenic and selenium according to the formula Ge₃₃ As₁₂ Se₅₅.

14. The system of claim 1 wherein the third lens is a chalcogenide.

15. The system of claim 1 wherein the third lens predominantly comprises zinc sulfide.

16. The system of claim 1 wherein the third lens predominantly comprises zinc selenide.

17. The system of claim 1 wherein the first and third lenses are each a chalcogenide.

18. The system of claim 17 wherein the second lens predominantly comprises germanium.

19. The system of claim 1 wherein:

the first lens is selected from the group of glasses consisting of Ge_X Sb _Y Se_Z and Ge_X As_Y Se_Z ; and

the third lens is formed of materials selected from the group consisting of sulfides and selenides of zinc and combinations thereof.

20. The system of claim 1 wherein:

the first lens predominantly comprises germanium, antimony and selenium according to the formula Ge₂₈ Sb₁₂ Se₆₀ ; and

the third lens predominantly comprises zinc sulfide.

21. The system of claim 1 wherein:

the first lens predominantly comprises germanium, arsenic and selenium according to the formula Ge₃₃ As₁₂ Se₅₅ ; and

the third lens predominantly comprises zinc sulfide;

22. The system of claim 1 wherein:

the first lens predominantly comprising germanium, antimony and selenium according to the formula Ge₂₈ Sb₁₂ Se₆₀ ; and

the third lens predominantly comprises zinc selenide.

23. The system of claim 1 wherein:

the first lens predominantly comprises germanium, arsenic and selenium according to the formula Ge₃₃ As₁₂ Se₅₅ ; and

the third lens predominantly comprises zinc selenide.

24. The system of claim 1 further including a second lens group arranged to provide lateral color correction to radiation transmitted by the triplet, the triplet and second lens group forming an afocal lens system.

25. The system of claim 24 wherein:

the first lens is a positive element having V =43;

the second lens is a negative element having a power between 0.40 and 0.48 that of the first lens;

the third lens is a negative element formed of zinc sulfide and having a power between pb 0.18 and 0.26 that of the first lens; and

the second lens group comprises a positive lens having V=43, a negative lens formed of zinc sulfide, a second positive lens having V=43 and a third positive lens having V=43.

26. The system of claim 1 further including a second lens group arranged to correct for off axis color aberrations and wherein the first lens is a positive element having V=44.6, the triplet and second lens group forming an imaging lens system.

27. The system of claim 26 wherein:

the triplet and second lens group form an f/1.5 imaging lens system;

the second lens is a negative element having a power between 0.20 and 0.30 that of the first lens;

the third lens is a negative element formed of zinc selenide and having a power between 0.50 and 0.60 that of the first lens; and

the second lens group comprises a positive lens having V=44.6, a negative lens formed of germanium and a negative lens formed of zinc selenide.

28. A wide spectral band infrared lens system comprising:

a first lens formed of a ternary composition according to the formula Ge_X Sb_Y Se_Z ;

a second lens comprising germanium; and

a third lens comprising zinc sulfide, said lens system capable of simultaneously focusing radiation in the 3 -5 micrometer and the 8 -12 micrometer atmospheric windows for imaging about a single focal plane.

29. The system of claim 28 wherein the first lens is formed of a ternary composition according to the formula Ge₂₈ Sb₁₂ Se₆₀.

30. The system of claim 28 wherein:

the first lens is a positive element;

the second lens is a negative element having a power between 0.40 and 0.48 that of the first lens; and

the third lens is a negative element having a power between 0.18 and 0.26 that of the first lens.

31. The system of claim 30 wherein the power of the second lens is 0.44 that of the first lens and the power of the third lens is 0.22 that of the first lens.

32. The system of claim 28 wherein the triplet is ordered such that incoming radiation is first received by the first lens and last transmitted by the third time.

33. A wide spectral band infrared lens system comprising:

a first lens formed of a ternary composition according to the formula Ge_X As_Y Se_Z ;

a second lens comprising germanium; and

a third lens comprising zincl selenide, said lens system capable of simultaneously focusing radiation in the 3 -5 micrometer and the 9 -12 micrometer atmospheric windows for imaging about a single focal plane.

34. The system of claim 33 wherein the first lens is formed of a ternary composition according to the formula Ge₃₃ As₁₂ Se₅₅.

35. The system of claim 33 wherein:

the first lens is a positive element;

the second lens is a negative element having a power between 0.02 and 0.3 that of the first lens; and

the third lens is a negative element having a power between 0.5 and 0.6 that of the first lens.

36. The system of claim 35 wherein the power of the second lens is 0.24 that of the first lens and the power of the third lens is 0.52 that of the first lens.

37. The system of claim 33 wherein the triplet is ordered such that incoming radiation is first received by the first lens and last transmitted by the third lens.

38. An infrared refractive lens triplet having color correcting properties for radiation ranging from 3 to 13 micrometers, said triplet comprising:

a first lens formed of glass characterized by chromic properties corresponding approximately to 40 <

V <

46,

space="preserve" listing-type="equation">V=(N.sub.D -1)/(N.sub.13 -N.sub.3),

wherein for said first lens glass;

N_D is the refractive index at 8 micrometers,

N₁₃ is the refractive index at 13 micrometers, and

N₃ is the refractive index at 3 micrometers;

a second lens comprising germanium; and

a third lens formed of materials selected from the group consisting of sulfides and selenides of zinc and combinations thereof.

39. The lens triplet of claim 38 wherein the lens powers are formulated to simultaneously focus radiation in the 3 -5 micrometer and the 8 -12 micrometer atmospheric windows for imaging about a single focal plane.

40. The lens triplet of claim 39 wherein said triplet is capable of simultaneously focusing radiation throughout the 3 to 12 micrometer range for imaging upon a single focal plane.

42. The triplet of claim 38 wherein the first lens glass predominantly comprises germanium, arsenic and selenium according to the formula Ge₃₃ As₁₂ Se₅₅.

43. The lens triplet of claim 38 wherein the lens powers are formulated to simultaneously focus all radiation in the 3.5 14 13 micrometer range for imaging about a single focal plane.

41. The triplet of claim c8 wherein the first lens glass predominantly comprises germanium, antimony and selenium according to the formula Ge₂₈ Sb₁₂ Se₆₀.