Refractive/diffractive infrared imager and optics

• US 5,973,827 A
• Filed: 01/20/1998
• Issued: 10/26/1999
• Est. Priority Date: 03/27/1997
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Chipper, Robert B.
• Primary Examiner(s): HENRY, JON W
• Application Number:
  US09/009,323
• Time in Patent Office: 644 Days
• Field of Search: 359/19, 359/15, 359/16, 359/565, 359/566, 359/558, 359/355, 359/356, 359/357
• US Class Current: 359/356
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 27/0037 with diffracting elements G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876
• CPC Class Codes: G02B 27/4211 correcting chromatic aberrations G02B27/0056, G02B27/4222, G02B27/4227 take precedence
• CPC Class Codes: G02B 27/4216 correcting geometrical aberrations
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 27/4277 being separated by an air space
• CPC Class Codes: G02B 5/1809 with pitch less than or comparable to the wavelength

Abstract

This patent teaches a low cost imager. The imager has an refractive objective lens 10 having a surface with a color correcting diffractive pattern 16 and an infrared transmitting polymeric field lens 18 having a substantially flat surface with a first field-correcting diffractive pattern. In this imager, the first field-correcting diffractive pattern operates to reduce aberrations of an image. In some embodiments, the imager further has a second field-correcting diffractive pattern on the field lens, where the first and second field-correcting diffractive pattern cooperating to reduce aberrations of the image. Additionally, this patent teaches a refractive/diffractive achromatic lens group 30. This achromat 30 can be used in the disclosed imager or in other optical devices. The achromatic group 30 has a refractive lens 10 and a lens 28 having a substantially flat surface with a surface diffractive pattern 16, the surface diffractive pattern cooperating with the refractive lens to reduce chromatic aberrations. Preferably, the second lens is formed from a polymeric sheet. These optics of the present invention can be used in infrared or visible optical devices.

Claims

1. An infrared imager comprising:

an infrared transmitting glass objective lens having a surface with a color correcting diffractive pattern; and

an infrared transmitting polymeric field lens having a substantially flat surface with a first field-correcting diffractive pattern, the first field-correcting diffractive pattern operating to reduce aberrations of an image.

2. The imager of claim 1, further comprising a second field correcting diffractive pattern on the field lens, the first and second field-correcting diffractive patterns cooperating to reduce aberrations of the image.

3. The imager of claim 1, wherein the objective lens glass is selected from the group consisting of Ge, chalcogenide glass, ZnS, ZnSe, GaAs, and TI-1173 glass.

4. An infrared imager comprising:

an infrared transmitting achromatic lens group, the group comprising an infrared transmitting glass objective lens, and a second infrared transmitting lens having a substantially flat surface with a surface diffractive pattern, the surface diffractive pattern cooperating with the glass lens to reduce chromatic aberrations; and

an infrared transmitting polymeric field lens having a substantially flat surface with a first field-correcting diffractive pattern, the first field-correcting diffractive pattern operating to reduce aberrations of an image.

5. The imager of claim 4, further comprising a second field-correcting diffractive pattern on the field lens, the first and second field-correcting diffractive patterns cooperating to reduce aberrations of the image.

6. The imager of claim 4, wherein the objective lens glass is selected from the group consisting of Ge, chalcogenide glass, ZnS, ZnSe, GaAs, and TI-1173 glass.

7. The imager of claim 4, further comprising a fold mirror.

8. The imager of claim 4, further comprising a chopper between the field lens and the image.

9. The imager of claim 4, wherein the objective lens is a meniscus lens.

10. An infrared imager comprising:

objective optics selected from the group consisting of

1) an infrared transmitting, refractive objective lens having a first surface and a second surface, and

2) an infrared transmitting achromatic lens group, the group including an infrared transmitting, refractive objective lens, and a second infrared transmitting lens having a substantially flat surface with a surface diffractive pattern, the surface diffractive pattern cooperating with the refractive lens to reduce chromatic aberrations; and

an infrared transmitting field lens having a third surface and a fourth surface, one of the field lens surfaces including a diffractive pattern that reduces aberrations of an image;

wherein the imager does not use any additional elements to form the image, except elements that have no optical power.

11. The imager of claim 10, further comprising an optical element selected from the group consisting of fold mirrors, windows, and filters.

12. The imager of claim 10, further comprising a chopper between the field lens and an image plane.

13. The imager of claim 12, wherein the chopper includes an opaque surface to block optical energy.

14. The imager of claim 12, wherein the chopper includes a defocusing optical element to defocus the image.

15. The imager of claim 10, wherein the objective optics include the refractive objective lens having the first and second surfaces, and wherein one of the first and second surfaces of the refractive objective lens further includes a color correcting diffractive pattern.

16. The imager of claim 10, wherein the third and fourth surfaces of the field lens include diffractive patterns, the third and fourth surface diffractive patterns cooperating to reduce aberrations of the image.

17. The imager of claim 10, wherein the field lens includes a polymer.

18. The imager of claim 17, wherein the surface of the field lens other than the surface having the diffractive pattern includes an anti-reflective sub-wavelength structure.

19. The imager of claim 10, wherein the field lens includes a polymer and the diffractive pattern is embossed.

20. The imager of claim 10, wherein the field lens includes a glass material.

21. The imager of claim 10, wherein the objective optics include the infrared transmitting achromatic lens group, and wherein the surface diffractive pattern of the second infrared transmitting lens further cooperates with the refractive lens to also reduce monochromatic aberrations.

22. An infrared transmitting achromatic lens group, comprising:

an infrared transmitting glass lens; and

a second infrared transmitting lens having a substantially flat surface with a surface diffractive pattern, the surface diffractive pattern cooperating with the glass lens to reduce chromatic aberrations;

wherein the second infrared transmitting lens is a polymeric lens; and

wherein the glass lens is a meniscus lens.

23. The achromatic lens group of claim 22, wherein the polymeric lens is mounted on a flat surface of the glass lens.

24. An infrared transmitting achromatic lens group, comprising:

an infrared transmitting glass lens; and

a second infrared transmitting lens having a substantially flat surface with a surface diffractive pattern, the surface diffractive pattern cooperating with the glass lens to reduce chromatic aberrations;

wherein the second infrared transmitting lens is a polymeric lens; and

wherein the glass lens is a biconvex lens.

25. An infrared transmitting achromatic lens group, comprising:

an infrared transmitting glass lens; and

a second infrared transmitting lens having a substantially flat surface with a surface diffractive pattern, the surface diffractive pattern cooperating with the glass lens to reduce chromatic aberrations;

wherein the second infrared transmitting lens is a polymeric lens; and

wherein the glass lens is a biconcave lens.

26. An infrared imager, comprising:

infrared transmitting objective optics which include a refractive objective lens, and which include a first diffractive structure that is operable primarily to reduce chromatic aberrations; and

infrared transmitting field optics which include a second diffractive structure that is operable primarily to reduce field aberrations, the second diffractive structure being disposed between the objective optics and an image plane.

27. An imager according to claim 26, wherein the field optics includes a non-refractive element having the second diffractive structure thereon.

28. An image according to claim 27, wherein the second diffractive structure includes an approximately flat diffractive surface on one side of the non-refractive element.

29. An imager according to claim 28, including an anti-reflective sub-wavelength structure on a side of the non-refractive element opposite from the diffractive surface.

30. An imager according to claim 27, wherein the second diffractive structure includes first and second approximately flat diffractive surfaces which are disposed on opposite sides of the non-refractive element, and which cooperate to reduce field aberrations.

31. An imager according to claim 27, wherein the non-refractive element is approximately flat and made from a polymeric material.

32. An imager according to claim 31, wherein the second diffractive structure is embossed on the non-refractive element.

33. An imager according to claim 26, wherein the first diffractive structure includes the refractive objective lens having on one side thereof a diffractive surface.

34. An imager according to claim 26, wherein the objective optics includes a non-refractive element, and the first diffractive structure includes an approximately flat diffractive surface provided on one side of the non-refractive elememt.

35. An imager according to claim 34, wherein the non-refractive element is made from a polymeric material.

36. An imager according to claim 26, including a stop disposed optically between the refractive objective lens and the second diffractive structure.

37. An imager according to claim 26, including a chopper disposed optically between the field optics and an image plane.

38. An imager according to claim 26, wherein the objective and field optics are free of other image-forming elements with optical power.