Agile beam steering using phased-array-like elements

• US 6,480,334 B1
• Filed: 01/18/1994
• Issued: 11/12/2002
• Est. Priority Date: 01/18/1994
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Farn, Michael Wayne
• Primary Examiner(s): Spyrou, Cassandra
• Application Number:
  US08/183,505
• Time in Patent Office: 3,220 Days
• Field of Search: 359/565, 359/566, 359/569, 359/573, 359/571, 359/574, 359/575
• US Class Current: 359/575
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 27/0087 Phased arrays
• CPC Class Codes: G02B 27/4227 in image scanning systems
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• 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 5/1885 Arranged as a periodic array

Abstract

Agile steering of a laser beam using a pair of complementary optical elements which are mechanically translated. The elements consist of pixelated steps of varying depth. Structure is provided to steer a laser beam by translating one element with respect to the other element by a distance that is an integer multiple of the step width.

Claims

1. Optical apparatus for agile steering of a light beam comprising:

a complementary pair of first and second optical elements, each of the elements including a phased-array-like profile of pixelated steps with no step introducing a phase delay greater than one wave; and

structure to position the elements to face each other in close proximity and to translate one element with respect to the other element by a distance equal to an integer multiple of the width of the pixelated step.

2. The device of claim 1 wherein the phased-array-like profile is piecewise flat.

3. The device of claim 1 wherein, said beam is steered to the 0 order when said elements are aligned with each other.

4. The device of claim 1 wherein, said beam is steered into the nth order when said elements are translated by an amount nΔ

x, where Δ

x is the step width.

5. The device of claim 1 wherein, said first element introduces a phase delay of φ

(x), and said second element introduces a phase delay of −

φ

(x+nΔ

x) when shifted by amount Δ

x.

6. The device of claim 5 wherein, the phased-array-like profile is φ

_P(x)=(−

π

m²/N)mod 2π

for mΔ

x−

Δ

x/2<

x mΔ

x+Δ

x/2, where m is an integer.

7. The device of claim 6 wherein, said phased-array-like profile results in an imperfect blaze but a completely filled aperture.

8. The device of claim 1 wherein general diffraction efficiency is sinc²(l/N) if l=N+mN and m is an integer and 0 otherwise, where l is any diffraction order, nΔ

x is the amount the first optical element is translated with the respect to the second optical element and N is the number of steps in one dimension of a cell.

9. The device of claim 1 wherein, the efficiency with which said beam is steered into the nth order is

10. The device of claim 1 wherein, sidelobe diffractions are confined to a small number of orders which are far away from the target order.

11. The device of claim 1 wherein each element consists of one cell.

12. The device of claim 1 wherein each element consists of an array of cells.

13. The device of claim 1 wherein the phased-array-like profile produced by a single cell and that produced by multiple cells always differ by an integer multiple of waves such that said phased-array-like profiles are equivalent.

14. The device of claim 1 wherein said phased-array-like profile consists of parallel grooved steps whereby said beam is steered in a direction perpendicular to the edges of the steps.

15. The device of claim 1 wherein said phased-array-like profile consists of square or rectangular steps whereby said beam is steered in two directions perpendicular to the edges of the steps.

16. The device of claim 14 or 15 wherein a phase delay of each step is caused by variations in physical height.

17. The device of claim 1 wherein, said elements are fabricated on quartz substrates.

18. The device of claim 1 wherein said elements are fabricated with four binary masks.

19. The device of claim 1 wherein, said elements are quantized to 16 phase levels with a minimum feature size of 5.0 μ

m.

20. An optical device for agile steering a light beam comprising a complementary pair of binary optics elements with phased array profiles, the first element having a planar surface with one or more steps with each step introducing a phase delay of not more than one wave, the second element being identical to the first element but each step having phase delay opposite of said delay of the complementary step in the first element, wherein said elements with the profiled surfaces positioned to face each other in close proximity and mechanically translated in the direction parallel to any side of the elements by a distance that is an integer multiple of the step width, thus diffracting the incoming light beam into any diffraction order.

21. The device of claim 20 wherein, said elements are fabricated with contact lithography and diffusion.

22. The device of claim 20 wherein, said elements are stripes, squares, rectangles or hexagons.