Re-imaging optical system employing refractive and diffractive optical elements

• US 5,257,133 A
• Filed: 09/11/1991
• Issued: 10/26/1993
• Est. Priority Date: 09/11/1991
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Chen, Chungte W.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Glick, Edward J.
• Application Number:
  US07/757,795
• Time in Patent Office: 776 Days
• Field of Search: 359/355, 359/356, 359/357, 359/423, 359/424, 359/434, 359/435, 359/558, 359/565, 359/566, 359/569, 359/570, 359/571, 359/741, 359/742, 359/13, 359/14, 359/16, 359/19, 359/630 , 359/637
• US Class Current: 359/565
• 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 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08

Abstract

A re-imaging optical system (36) is provided which utilizes a combination of refractive and diffractive optical elements. The system includes an objective lens group (38) for focusing an incoming beam of light to a first image plane. A relay lens group (40) refocuses the beam of light in a second image plane after it passes through the first image plane. The relay lens group (40) includes a diffractive optical element (48) for correcting aberrations introduced by the objective and relay lens groups. The diffractive optical element (48) eliminates a number of individual optical elements which would otherwise be required to correct aberrations, thereby reducing the total number of optical elements in the system. In the preferred embodiment, the diffractive optical element (48) comprises a binary optical element. The resulting system yields better image quality, better throughput, and a lighter, less bulky, re-imaging optical system (36).

Claims

1. A re-imaging optical system comprising:

an objective lens means for focusing an incoming beam of light to a first image plane;

a relay lens means for refocusing said beam of light in a second image plane after it has passed through said first image plane; and

said relay lens means including a binary optical element which introduces magnifying power in addition to any magnifying power introduced by refraction in the relay lens, the binary optical element also correcting aberrations introduced by said objective and relay lens means.

2. The re-imaging optical system of claim 1 wherein said objective lens means and said relay lens means both contain similar optical elements which tend to balance out their respective aberrations according to the symmetry principle.

3. The re-imaging optical system of claim 2 wherein said objective lens means and said relay lens means both contain silicon refractive lenses.

4. The re-imaging optical system of claim 3 wherein said silicon lenses contained in said objective and relay lens means are both aspherical lenses.

5. The re-imaging optical system of claim 1 wherein said relay optical lens means includes a germanium lens.

6. The re-imaging optical system of claim 1 wherein said binary optical element contains a Fresnel zone plate attached to a lens in said relay lens means, wherein said binary optical element provides chromatic aberration correction.

7. The re-imaging optical system of claim 6 wherein said binary optical element also corrects spherochromatism.

8. The re-imaging optical system of claim 6 wherein said binary optical element also corrects chromatic coma.

9. The re-imaging optical system of claim 1 wherein said beam of light is infrared light.

10. An optical system comprising:

a first lens means for focusing an incoming beam of light to an image plane;

a second lens means for receiving and refracting said beam of light after it passes through said image plane;

said first and second lens means together being partially self correcting of aberrations according to the symmetry principle, whereby the aberrations in said first and second lens means tend to balance each other out; and

a binary optical element in the path of said beam of light which introduces magnifying power in addition to any magnifying power introduced by refraction in the second lens means the binary optical element also correcting a portion of the optical aberrations not corrected by said first and second lens means.

11. The optical system of claim 10 further comprising a detector for receiving said beam of light after it is refracted by said second lens means.

12. The optical system of claim 10 wherein said second lens means refocuses said beam of light.

13. The optical system of claim 10 wherein said aberrations corrected by said first and second lens means include lateral color and coma.

14. The optical system of claim 13 wherein said portion of optical aberrations corrected by said binary optical element includes axial color.

15. The optical system of claim 10 wherein said first and second lens means both comprise silicon lenses.

16. The optical system of claim 10 wherein said first and second lens means both comprise aspherical lenses.

17. The optical system of claim 16 wherein said second optical system includes silicon and germanium lenses.

18. A re-imaging optical system comprising:

an objective lens means for focusing an incoming beam of infrared light to a first image plane;

a relay lens means for refocusing said beam of light in a second image plane after it has passes through said first image plane;

said objective lens means and said relay lens means both containing silicon aspherical refractive lenses which tend to balance out their respective aberrations according to the symmetry principle;

said relay lens means including a binary optical element including a Fresnel zone plate attached to a lens in said relay means;

said binary optical element providing magnifying power in addition to any magnifying power introduced by refraction in the relay lens, the binary optical element also providing chromatic aberration correction; and

a detector means for receiving said beam of light after it is refocused by said relay lens means.