Optical systems and methods using microelectromechanical-systems mirrors exceeding thirty microns

• US 7,732,751 B2
• Filed: 04/28/2007
• Issued: 06/08/2010
• Est. Priority Date: 06/13/2005
• Status: Active Grant

• Current Assignee: Arete Associates
• Original Assignee: Arete Associates
• Inventors: Kane, David M.
• Primary Examiner(s): Le; Que T
• Application Number:
  US11/796,603
• Publication Number:
  US 20090015891A1
• Time in Patent Office: 1,137 Days
• Field of Search: 250/216, 250/239, 250/221, 250/208.1, 250/234, 250/235, 359197-291, 385/24, 385/140, 385/73
• US Class Current: 250/216
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/021 using plane or convex mirrors, parallel phase plates, or particular reflectors
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0289 Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4804 Auxiliary means for detecting or identifying lidar signals or the like, e.g. laser illuminators
• CPC Class Codes: G01S 7/495 Counter-measures or counter-counter-measures using electronic or electro-optical means
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence

Abstract

A detector and aperture determine radiation characteristics, including angular direction throughout a specified range, of external articles. Preferably an afocal aperture element enlarges/reduces the article and volume FOR. Mirror(s) along a path between detector and aperture, rotatable about plural axes, make the detector address varying regions. Preferably each mirror is MEMS, exceeding five to thirty microns. The detector “sees” articles throughout the range, at constant magnification. Other aspects rotate magnetically controlled dual-axis MEMS mirrors, each with electrical coils opposed across an axis, and anther magnet whose field interacts with coil-current fields, generating force components: one includes oppositely directed forces, torquing the mirrors; another thrusts mirrors outward from the array rest plane, causing variable “piston”. Alternatively, other forces pull mirror(s) outward—and the second component attracts them inward. Components are adjusted to steer a beam in a desired direction, and wavefronts from adjacent mirrors are in phase for finer diffraction limit.

Claims

1. An optical system for dynamically determining radiation characteristics, including associated angular direction throughout a specified range of angular directions, of an external article in a volume outside the system;

said optical system comprising;

an optical detector;

an entrance aperture;

an afocal element, associated with the aperture, for enlarging or reducing the field of regard of such external article and such volume as seen by the detector; and

disposed along an optical path between the detector and the entrance aperture, at least one mirror, rotatable about plural axes, for causing the detector to address varying portions of such volume outside the optical system;

each mirror of the at least one mirror is a microelectromechanical mirror having dimensions in a range exceeding thirty microns;

wherein, due to said enlarging or reducing of the field of regard together with rotation of the at least one mirror, such external article is visible to the detector throughout the specified range, substantially without changing magnitude of said enlarging or reducing.

2. The optical system of claim 1, wherein:

each mirror of the at least one mirror has dimensions in a range exceeding five millimeters.

3. The optical system of claim 1, wherein:

each mirror of the at least one mirror has dimensions in a range of ten millimeters and above.

4. The optical system of claim 1, wherein:

each mirror of the at least one mirror has dimensions in a range of twenty millimeters and above.

5. The optical system of claim 1, wherein:

each mirror of the at least one mirror has dimensions in a range from five to thirty millimeters.

6. The optical system of claim 1, wherein:

each mirror of the at least one mirror is driven, at least in part, magnetically.

7. The optical system of claim 1, wherein:

the at least one mirror comprises plural mirrors; and

the plural mirrors are each controlled in tip, tilt and piston.

8. The optical system of claim 1, wherein:

the at least one mirror comprises plural mirrors; and

each mirror is controlled in piston by a respective magnetic drive that operates to stand that mirror away from a base or rest plane of that mirror, by a variable distance.

9. The optical system of claim 8, wherein the magnetic drive comprises:

magnetic coils disposed at opposite sides of a rotational flexure; and

means for electrically energizing the magnetic coils generally independently, to substantially balance the mirror at a desired rotational excursion while standing the mirror away from the base or rest plane to achieve a desired piston excursion.

10. The optical system of claim 8, further comprising:

means for controlling rotational and piston excursions of each mirror to generally minimize relative optical phase of optical radiation reflected at the plural mirrors, including adjacent mirrors.

11. The optical system of claim 10, further comprising:

means for detecting or adjusting, or both, relative optical phase.

12. The optical system of claim 11, wherein:

the detecting-or-adjusting means comprise a wavefront sensor.

13. The optical system of claim 11, wherein:

the detecting-or-adjusting means comprise an auxiliary optical path that generates and optimizes a point spread function based upon tip, tilt and piston settings of the plural mirrors.

14. The optical system of claim 10, wherein:

the excursion-controlling means comprise means for holding relative optical phase, of radiation reflected at adjacent mirrors, to modulo 2π

radians within roughly plus-or-minus twenty percent of one wavelength.

15. The optical system of claim 10, wherein:

the excursion-controlling means comprise means for holding relative optical phase, of radiation reflected at adjacent mirrors, to modulo 2π

radians within roughly plus-or-minus ten percent of one wavelength.

16. The optical system of claim 1, wherein:

each mirror of the at least one mirror has dimensions in a range exceeding five millimeters; and

the afocal element is an afocal lens assembly disposed at the aperture, and that magnifies or reduces the varying introduced by the at least one mirror.

17. The optical system of claim 16, wherein:

the afocal element is disposed generally at the aperture.

18. The optical system of claim 16:

wherein the afocal lens assembly does not focus such external article onto any solid element of the optical system; and

further comprising a focusing lens, associated with the detector, for;

intercepting a radiation beam that has passed through the afocal lens assembly, and that also has been reflected by the at least one mirror, and

focusing rays, in said radiation beam, from such external article onto the detector.

19. The optical system of claim 16, wherein:

the afocal element defines the aperture.

20. The optical system of claim 16:

further comprising an imaging module; and

wherein the afocal element and the at least one mirror are shared by both;

the imaging module, and

the detector with its focusing lens.

21. The optical system of claim 16:

further comprising a spectral-analysis module; and

wherein the afocal element and the at least one mirror are shared by both;

the spectral-analysis module, and

the detector with its focusing lens.

22. The optical system of claim 16:

further comprising an auxiliary optical system that includes at least one of;

a ranging laser for projecting a ranging beam to such article, and

a ranging-laser receiving module, distinct from the aforesaid detector with its focusing lens, for receiving and analyzing the ranging beam after reflection from such article; and

wherein the afocal element and the at least one mirror are shared by both;

one or both of the ranging laser and receiving module, and

the detector with its focusing lens.

23. The optical system of claim 16:

further comprising an auxiliary optical system that includes at least one of;

a communication-beam transmission module for transmitting a first modulated communication beam toward such article, and

a communication-beam reception module, distinct from the aforesaid detector with its focusing lens, for receiving and interpreting a second modulated communication beam received from such article or from a region of such volume that includes such article; and

wherein the afocal element and the at least one mirror are shared by both;

one or both of the transmission and reception modules, and

the detector with its focusing lens.

24. The optical system of claim 16:

further comprising an auxiliary optical system that includes at least one of;

a communication-beam transmission module for transmitting a first modulated communication beam toward such article, and

a communication-beam reception module for receiving and interpreting a second modulated communication beam received from such article or from a region of such volume that includes such article; and

wherein the afocal element and the at least one mirror are shared by one or both of the transmission and reception modules.

25. The optical system of claim 16:

further comprising a powerful laser for projecting a beam to impair function or structural integrity of such article; and

wherein the afocal element and the at least one mirror are shared by both;

the powerful laser, and

the detector with its focusing lens.

26. The optical system of claim 16:

further comprising a laser for dazzling or confusing either a human operator or optical apparatus associated with such article, or both; and

wherein the afocal element and the at least one mirror are shared by both;

the dazzling laser, and

the detector with its focusing lens.

27. The optical system of claim 16, wherein the external article comprises a radiation source of a particular type, said characteristics comprise existence and presence of the source, and the optical system is for detecting the source and determining its angular location, and:

said optical detector is a detector for such radiation from such source of such particular type; and

further comprising means for automatically responding to the detector by actively servocontrolling the at least one mirror to substantially center an image of a detected source on the detector.

28. The optical system of claim 16:

wherein the detector reports relative location of incident radiation on a sensitive surface of the detector; and

further comprising means for automatically responding to the detector by actively servocontrolling the at least one mirror to substantially center an image of a detected source on the detector.

29. The optical system of claim 28, further comprising:

means for reading and interpreting angular position from mirror position feedback signals while the image is substantially centered on the detector.

30. The optical system of claim 28, wherein:

the responding means comprise means for continuing to servocontrol the at least one mirror to track the already detected source substantially at the detector center.

31. The optical system of claim 30, wherein:

the at least one mirror comprises plural mirrors; and

the continuing means comprise means for using one or more mirrors to track the already-detected source, and one or more other mirrors to instead simultaneously perform another function.

32. The optical system of claim 31, wherein:

the other function comprises searching for another source, not yet detected.

33. The optical system of claim 31, wherein:

the other function comprises operating the auxiliary optical system with respect to said already-detected source or another article or scene.

34. The optical system of claim 30, further comprising:

operating a beam-splitter to enable use of an auxiliary optical system, with respect to said already-detected source or another article or scene, simultaneously with said continuing tracking of the already-detected source.

35. The optical system of claim 16, wherein:

the detector is a position-sensing detector (PSD).

36. The optical system of claim 16, wherein:

the detector is a quad cell.

37. The optical system of claim 16, further comprising:

means for substituting a detector array for the detector, to image the already-detected source or associated articles, or both.

38. The optical system of claim 16, further comprising:

means for directing a response toward the detected article or an article associated therewith, or both.

39. The optical system of claim 38, wherein:

the response-directing means comprise means for emitting a beam of radiation that uses said entrance aperture as an exit aperture and is reflected from said at least one mirror;

wherein the response-directing means share, with such radiation from such source, both;

said entrance aperture, and

said at least one mirror.

40. An optical system for dynamically determining radiation characteristics, including associated angular direction, of an external article in a volume outside the system;

said optical system comprising;

an optical detector;

an entrance aperture;

an afocal optically powered element, associated with the aperture, for modifying the field of regard of such external article and such volume as seen by the detector;

wherein the afocal element does not focus such external article onto any solid element of the optical system; and

disposed along an optical path between the detector and the entrance aperture, at least one microelectromechanical-systems mirror, rotatable about plural axes, for causing the detector to address varying portions of such volume outside the optical system and with the enlarged field of regard produced by the afocal element;

said at least one mirror having dimensions in a range greater than five millimeters.

41. The optical system of claim 40, wherein:

said mirror is driven magnetically about at least one of the plural axes.

42. The optical system of claim 41, wherein:

the at least one mirror comprises plural mirrors; and

the plural mirrors are each controlled in tip, tilt and piston.

43. The optical system of claim 42, wherein:

each mirror is controlled in piston by a magnetic drive that operates to stand that mirror away from, or draw it inward toward, a base or rest plane of that mirror, by a variable distance.

44. The optical system of claim 43, wherein the magnetic drive comprises:

magnetic coils disposed at opposite sides of a rotational flexure; and

means for electrically energizing the magnetic coils generally independently, to substantially balance the mirror at a desired rotational excursion while standing the mirror away from, or drawing it in toward, the rest plane or base to achieve a desired piston excursion.

45. The optical system of claim 43, further comprising:

means for controlling rotational and piston excursions of the mirrors to generally minimize relative optical phase of optical radiation reflected from the plural mirrors.

46. The optical system of claim 45, further comprising:

means for detecting or adjusting, or both, relative optical phase.

47. The optical system of claim 46, wherein:

the detecting-or-adjusting means comprise a wavefront sensor.

48. The optical system of claim 46, wherein:

the detecting-or-adjusting means comprise an auxiliary optical path that generates and optimizes a point spread function based upon tip, tilt and piston settings of the plural mirrors.

49. The optical system of claim 45, wherein:

the excursion-controlling means comprise means for holding relative optical phase, of radiation reflected from adjacent mirrors, to modulo 2π

radians within roughly plus-or-minus twenty percent of one wavelength.

50. The optical system of claim 45, wherein:

the excursion-controlling means comprise means for holding relative optical phase, of radiation reflected at adjacent mirrors, to modulo 2π

radians within roughly plus-or-minus ten percent of one wavelength.

51. The optical system of claim 40, wherein:

said mirror dimensions are approximately ten millimeters, or greater.

52. The optical system of claim 40, wherein:

said mirror dimensions are approximately twenty millimeters, or greater.

53. The optical system of claim 40, wherein:

said mirror dimensions are approximately thirty millimeters, or greater.

54. The optical system of claim 40, wherein:

the afocal element is disposed generally at the aperture.

55. The optical system of claim 40, wherein:

the afocal enlarging element defines the aperture.

56. The optical system of claim 40:

further comprising a spectral-analysis module; and

wherein the afocal enlarging element and the at least one mirror are shared by both;

the spectral-analysis module, and

the detector with its focusing lens.

57. The optical system of claim 40:

further comprising an auxiliary optical system that includes at least one of;

a ranging laser for projecting a ranging beam to such article, and

a ranging-laser receiving module, distinct from the aforesaid detector with its focusing lens, for receiving and analyzing the ranging beam after reflection from such article; and

wherein the afocal element and the at least one mirror are shared by both;

one or both of the ranging laser and receiving module, and

the detector with its focusing lens.

58. The optical system of claim 40:

further comprising an auxiliary optical system that includes at least one of;

a communication-beam transmission module for transmitting a first modulated communication beam toward such article, and

a communication-beam reception module, distinct from the aforesaid detector with its focusing lens, for receiving and interpreting a second modulated communication beam received from such article or from a region of such volume that includes such article; and

wherein the afocal element and the at least one mirror are shared by both;

one or both of the transmission and reception modules, and

the detector with its focusing lens.

59. The optical system of claim 40:

further comprising a powerful laser for projecting a beam to impair function or structural integrity of such article; and

wherein the afocal element and the at least one mirror are shared by both;

the powerful laser, and

the detector with its focusing lens.

60. The optical system of claim 40:

further comprising a laser for dazzling or confusing either a human operator or optical apparatus associated with such article, or both; and

wherein the afocal element and the at least one mirror are shared by both;

the dazzling laser, and

the detector with its focusing lens.