Superzone holographic mirror

• US 5,285,314 A
• Filed: 12/22/1992
• Issued: 02/08/1994
• Est. Priority Date: 05/03/1991
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Futhey, John A.
• Primary Examiner(s): Lerner, Martin
• Application Number:
  US07/995,339
• Time in Patent Office: 413 Days
• Field of Search: 359/565, 359/570, 359/571, 359/572, 359/574, 359/575, 359/576, 359/566, 359/569
• US Class Current: 359/565
• 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
• CPC Class Codes: G02B 5/1895 such optical elements having dioptric power
• CPC Class Codes: G02B 5/32 Holograms used as optical elements

Abstract

A diffractive mirror has a plurality of diffractive zones at least one of which has an optical step having a height equal to jλ/2 and at least one of which has an optical step having a height equal to kλ/2 where λ is a design wavelength of the mirror and j and k are unequal nonzero integers. Alternatively stated at least one of the optical steps induces a relative phase shift of 2jπ at the image point between two light rays emerging from a point source at the object point and striking the lens immediately on opposite sides of the step and at least one of the steps induces a relative phase shift of 2kπ at the image point between two light rays emerging from a point source at the object point and striking the lens immediately on opposite sides of that step.

Claims

1. A mirror having diffractive focusing power, said diffractive power being produced by a plurality of diffractive zones, said diffractive zones being terminated by optical steps, a first group of said diffractive zones having optical steps having heights equal to jλ

/2 and a second group of said diffractive zones having optical steps having heights equal to kλ

/2 where λ

is a design wavelength of light of the mirror and j and k are unequal nonzero integers.

2. The mirror according to claim 1 wherein said mirror has an optic axis passing through a first diffractive zone and said first group of diffractive zones is adjacent said first zone and said second group of diffractive zones are separated from said first zone by said first group of zones, said zones of said first group having optical steps having heights equal to λ

/2 and said zones of said second group having optical steps having heights equal to λ

.

3. The mirror according to claim 2 wherein said zones are circular and concentric.

4. The mirror according to claim 2 wherein said zones are rectangular.

5. The mirror according to claim 2 further comprising a third group of diffractive zones separated from said first zone by said first and second groups of zones, said zones of said third group having optical steps having heights equal to 3λ

/2.

6. The mirror according to claim 5 wherein said zones are circular and concentric.

7. The mirror according to claim 5 wherein said zones are rectangular.

8. The mirror according to claim 1 wherein said zones have circular contours.

9. The mirror according to claim 8 wherein said mirror has an optic axis passing through a first diffractive zone and said first group of diffractive zones is adjacent said first zone and said second group of diffractive zones are separated from said first zone by said first group of zones, said zones of said first group having optical steps having heights equal to λ

/2 and said zones of said second group having optical steps having heights equal to λ

.

10. The mirror according to claim 9 further comprising a third group of diffractive zones separated from said first zone by said first and second groups of zones, said zones of said third group having optical steps having heights equal to 3 λ

/2.

11. The mirror according to claim 1 wherein said zones have linear contours.

12. The mirror according to claim 11 wherein said mirror has an optic axis passing through a first diffractive zone and said first group of diffractive zones is adjacent said first zone and said second group of diffractive zones are separated from said first zone by said first group of zones, said zones of said first group having optical steps having heights equal to λ

/2 and said zones of said second group having optical steps having heights equal to λ

.

13. The mirror according to claim 12 further comprising a third group of diffractive zones separated from said first zone by said first and second groups of zones, said zones of said third group having optical steps having heights equal to 3λ

/2.

14. The mirror of claim 1 wherein said mirror is a first surface reflector.

15. The mirror of claim 14 wherein said mirror includes a polymeric body with a reflective metal coated thereon.

16. The mirror of claim 14 wherein said mirror includes a body of a reflective metal.

17. The mirror of claim 16 wherein said reflective metal is copper.

18. The mirror of claim 1 wherein said mirror is a second surface reflector.

19. The mirror of claim 18 wherein said mirror has a body that provides refractive power.

20. The mirror of claim 18 wherein said mirror includes a transparent body of a polymeric material with a reflective metal coated thereon.

21. A mirror having diffractive power, and object and image points at object and image distances from said mirror respectively, said diffractive power being produced by a plurality of diffractive zones, a first group of said diffractive zones having optical steps with heights selected such that a relative phase shift of 2jπ

at said image point will be introduced between two light rays of a design wavelength emanating from a point source at said object point and striking said mirror immediately on opposite sides of one of said optical steps of said first group and a second group of said diffractive zones having optical steps with heights selected such that a relative phase shift of 2kπ

at said image point will be introduced between two rays of light of said design wavelength emanating from a point source at said object point and striking said mirror immediately on opposite sides of one of said optical steps of said second group, where j and k are unequal nonzero integers.

22. The mirror according to claim 21 wherein said mirror has a first zone and an optical axis passing through said first zone, said first group of zones being adjacent said first zone and said second group of zones being separated from said first zone by said first group of zones, and j is equal to one and k is equal to two.

23. The mirror according to claim 22 wherein said zones are circular and concentric.

24. The mirror according to claim 22 wherein said zones are rectangular.

25. The mirror according to claim 21 further comprising a third group of diffractive zones, said third group being separated from said first zone by said first and second groups of zones, said zones of said third group having optical steps with heights such that a relative phase shift of 6π

will be introduced at said image point between two rays of light of said design wavelength emanating from a point source at said object point and striking said mirror immediately on opposite sides of one of said optical steps of said third group.

26. The mirror according to claim 21 wherein said zones have circular contours.

27. The mirror according to claim 21 wherein said zones have linear contours.

28. The mirror of claim 21 wherein said object and image distances are both finite.

29. The mirror of claim 21 wherein said object distance is infinite.

30. The mirror of claim 21 wherein said image distance is infinite.

31. The mirror of claim 21 wherein said mirror is a first surface reflector.

32. The mirror of claim 31 wherein said mirror includes a polymeric body with a reflective metal coated thereon.

33. The mirror of claim 31 wherein said mirror includes a body of a reflective metal.

34. The mirror of claim 33 wherein said reflective metal is copper.

35. The mirror of claim 21 wherein said mirror is a second surface reflector.

36. The mirror of claim 35 wherein said mirror has a body that provides refractive power.

37. The mirror of claim 35 wherein said mirror includes a transparent body of a polymeric material with a reflective metal coated thereon.

38. A mirror having diffractive power, an object point and an image point, said diffractive power being produced by a plurality of diffractive zones, a first of said diffractive zones having an optical step with a height selected such that a relative phase shift of 2jπ

at said image point will be introduced between two light rays of a design wavelength emanating from a point source at said object point and striking said mirror immediately on opposite sides of said optical step of said first zone and a second of said diffractive zones having an optical step with a height selected such that a relative phase shift of 2kπ

at said image point will be introduced between two rays of light of said design wavelength emanating from a point source at said object point and striking said mirror immediately on opposite sides of said optical step of said second zone, where j and k are unequal nonzero integers.