Wavefront sensing and correction with deformable mirror

• US 5,026,977 A
• Filed: 06/15/1990
• Issued: 06/25/1991
• Est. Priority Date: 04/05/1989
• Status: Expired due to Term

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Hubbard, James E. Jr.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US07/538,896
• Time in Patent Office: 375 Days
• Field of Search: 250/201.1, 250/578.1, 250/201.9, 356/353, 356/354, 356/359, 356/360
• US Class Current: 250/201.9
• CPC Class Codes: G01J 2009/0249 with modulation
• CPC Class Codes: G01J 9/02 by interferometric methods using interferometers for measuring optically the linear dimensions of objects G01B9/02

Abstract

A closed loop system sends one portion of a coherent laser beam along a first path and another portion of the beam along a second path which is directed at a mirror formed on piezoelectric membrane. After reflection, both return beams are mixed on a photodetector array and the array output is analyzed to determine the values of a charge distribution on the piezoelectric membrane which will null or maintain constant the phase of the mixed beam.

Claims

1. A system for determining the radiation transmission characteristics of a region along a reference axis comprising:

A. means for generating a first substantially single frequency radiation beam along a first axis said first radiation beam being characterized by a wavelength g;

B. beamsplitter including means for splitting said first beam into a second beam and a third beam, means for directing said second beam along a second axis, and means for directing said third beam along a third axis, wherein one of said directed second and third beams at least in part propagates through said region;

C. a first reflector fixedly positioned along said second axis and including means for reflecting said second beam incident thereon back along said second axis;

D. a second reflector including a reflective surface on a piezoelectrically active support, said second reflector being positioned along said third axis for reflecting said third beam incident thereon back along said third axis;

E. charge deposition means for depositing a distribution of charge on the piezoelectrically active support to deform the support and thus the reflective surface in a range extending along said third axis between a first reference point and a second reference point on said third axis;

F. means for establishing a fourth beam and directing said fourth beam along a fourth axis, said fourth beam being a combination of said reflected second and third beams;

G. an array of radiation detectors positioned along and extending transverse to said fourth axis and including means responsive to portions of said fourth beam incident thereon for generating intensity signals, each of said intensity signals being representative of the intensity of the portion of said fourth beam incident on an associated detector of said array; and

H. processing means responsive to said intensity signals for generating control signals which are provided to the charge deposition means to control the distribution of charge such that said fourth beam has a substantially uniform intensity at said array of radiation detectors.

2. A system according to claim 1 wherein said array of detectors is a substantially planar array.

3. A system according to claim 1 wherein said generating means is a light source, whereby said first radiation beam is light beam that is substantially monochromatic.

4. A system according to claim 3, wherein said generating means is a laser, wherebY said first light beam is substantially coherent.

5. A system according to claim 3, wherein said radiation detectors are optical detectors.

6. A system according to claim 5, wherein said array of detectors is a substantially planar array.

7. A system according to claim 1, wherein said generating means is an acoustic source.

8. A system according to claim 7, wherein said radiation detectors are acoustic detectors.

9. A system according to claim 8, wherein said array of detectors is a substantially planar array.

10. A system according to claim 1 wherein said uniform intensity is a minimum intensity.

11. A system according to claim 1, wherein said piezoelectrically active support includes a bimorphous membrane.

12. A system according to claim 11, wherein said bimorphous membrane is formed of PVDF film.

13. A system according to claim 12, wherein said reflective surface is a conductive metal film under one micron thick.

14. A system according to claim 1, wherein said charge deposition means includes means for directing an electron beam at the support to create a spatially varying distribution of charge thereon.

15. A system according to claim 14, wherein said piezoelectrically active support includes a membrane formed of a piezoelectric copolymer or PVDF film.