Optical system for determining the angular position of a radiating point source and method of employing

• US 20060165312A1
• Filed: 03/08/2006
• Published: 07/27/2006
• Est. Priority Date: 02/13/2002
• Status: Active Grant

• Current Assignee: Northern Digital Inc. (Roper Technologies, Inc.)
• Original Assignee: Ascension Technology Corporation (Roper Technologies, Inc.)
• Inventors: Odell, Don
• Granted Patent: US 7,756,319 B2
• Time in Patent Office: Days
• US Class Current: 382/291
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 3/7835 using coding masks
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves

Abstract

An optical system for determining the angular position of a radiating point source is disclosed, wherein radiation from a point source travels through a mask and onto the surface of a sensor. A preferred embodiment employs a plurality of mask transmission frequencies and a detector designed to be sensitive to the phases of the frequencies. A computer measures the phases of a plurality of detected image frequencies. Measurement of the particular phases of the frequency components allows determination of the image shift on the detector axis. The image shift is then used to compute angle of incidence of the light source upon the detector. The preferred embodiment employs a refractive window, hence the angle of incidence between point radiating source and mask are determined using the window index of refraction and refraction equations. Applications include within the cockpit of a jet aircraft.

Claims

1. A system for determining the angular position and distance of a radiating source with respect to a detector, comprising:

a) a radiation detector;

b) a mask spaced in front of said detector, said mask having a plurality of transmission frequencies;

c) recording means for recording an image cast onto said detector by radiation passing through said mask;

d) computing means for computing data related to said image;

e) identifying means for identifying phases of a plurality of frequencies of said image and creating signals corresponding thereto;

f) determining means for determining angular position of said radiation source with respect to said detector;

g) said determining means receiving said signals and, therefrom, determining said angular position of said radiation source with respect to said detector.

2. The system of claim 1, wherein apertures in said mask comprise a transmissivity pattern varying in one dimension.

3. The system of claim 2, wherein said one dimension comprises a Y-axis.

4. The system of claim 1, wherein said detector and mask are planar and lie in parallel planes.

5. The system of claim 4, wherein said mask and detector are spaced apart by a known distance.

6. The system of claim 1, wherein said mask is spaced from said detector by a refractive medium or window.

7. The system of claim 1, wherein said detector includes a plurality of parallel arrays, each array detecting phase of a unique mask frequency.

8. The system of claim 7, wherein there are three mask frequencies related to one another by the ratio F₀:

5F₀;

25F₀, where F₀ is a fundamental frequency.

9. The system of claim 8, wherein an array of said detector detects phase of said fundamental frequency and provides coarse measurement.

10. The system of claim 9, wherein an array of said detector detects phase of said frequency 25F₀ and provides fine measurement.

11. The system of claim 1, wherein said detector includes a plurality of parallel detector arrays for identifying said phases.

12. The system of claim 11, wherein said plurality parallel detector arrays consist of a coarse, medium, and fine resolution array each responsive to phases of a particular mask image frequency.

13. The system of claim 1, wherein two orthogonal and coplanar arrangements of masks are used on a common window and two underlying orthogonal and coplanar detectors are located on a common substrate to create a two-dimensional angle of incidence sensor.

14. The system of claim 1, located within an aircraft cockpit.

15. The system of claim 14, wherein said aircraft comprises a jet.

16. The system of claim 15, wherein said jet aircraft has a canopy that filters a portion of light spectrum including an optical detection bandwidth.

17. The system of claim 16, wherein said optical detection bandwidth comprises a combined response of an optical detector bandwidth and an overlying detector filter bandwidth.

18. The system of claim 17, wherein said optical detection bandwidth includes an ultraviolet range and uses a detector filter that removes light above a wavelength of 400 nm.

19. The system of claim 17, wherein said optical detection bandwidth includes an infrared range and uses a detector filter that removes light below a wavelength of 1700 nm.

20. The system of claim 1, employing a plurality of detectors that detect emitter light angle of incidence in at least one dimension.

21. A system for determining the angular position and distance of a radiating source with respect to a detector, comprising:

a) a radiation detector, said detector including a plurality of parallel arrays, each array detecting phase of a unique mask frequency;

b) a mask spaced in front of said detector, said mask having a plurality of transmission frequencies, said mask having apertures comprising a transmissivity pattern varying in one dimension, said mask and detector each being planar and lying in parallel planes;

c) recording means for recording an image cast onto said detector by radiation passing through said mask;

d) computing means for computing data related to said image;

e) identifying means for identifying phases of a plurality of frequencies of said image and creating signals corresponding thereto;

f) determining means for determining angular position of said radiation source with respect to said detector;

g) said determining means receiving said signals and, therefrom, determining said angular position of said radiation source with respect to said detector.

22. The system of claim 21, wherein said mask and detector are spaced apart by a known distance.

23. The system of claim 21, wherein said mask is spaced from said detector by a refractive medium or window.

24. The system of claim 21, wherein there are three mask frequencies related to one another by the ratio F₀:

5F₀;

25F₀, where F₀ is a fundamental frequency.

25. The system of claim 24, wherein a first array of said detector detects phase of said fundamental frequency and provides coarse measurement and a second array of said detector detects phase of said frequency 25F₀ and provides fine measurement.

26. The system of claim 21, wherein said plurality parallel detector arrays consist of a coarse, medium, and fine resolution array each responsive to phases of a particular mask image frequency.

27. The system of claim 21, wherein two orthogonal and coplanar arrangements of masks are used on a common window and two underlying orthogonal and coplanar detectors are located on a common substrate to create a two-dimensional angle of incidence sensor.

28. The system of claim 21, located within a jet aircraft cockpit.

29. The system of claim 28, wherein said jet aircraft has a canopy that filters a portion of light spectrum including an optical detection bandwidth.

30. The system of claim 29, wherein said optical detection bandwidth comprises a combined response of an optical detector bandwidth and an overlying detector filter bandwidth.

31. The system of claim 30, wherein said optical detection bandwidth includes an ultraviolet range and uses a detector filter that removes light above a wavelength of 400 nm.

32. The system of claim 31, wherein said optical detection bandwidth further includes an infrared range and uses a detector filter that removes light below a wavelength of 1700 nm.

33. A system for determining the angular position and distance of a radiating source with respect to a detector comprising:

a) a source of radiation;

b) a radiation detector;

c) filter means in front of said detector for filtering sunlight while permitting radiation from said source to impinge upon an active area of said radiation detector;

d) said radiation detector generating signals related to an image cast onto said detector by radiation from said source passing through said filter means and impinging on said active area;

e) computing means for receiving said signals and, therefrom, determining angular position and distance of said radiating source with respect to said detector.

34. The system of claim 33, wherein said filter means comprises a first filter overlying said detector and filtering sunlight while permitting radiation from said source to pass therethrough.

35. The system of claim 34, wherein said filter means further comprises a second filter distal from said detector with respect to said first filter.

36. The system of claim 35, wherein said second filter filters sunlight.

37. The system of claim 36, wherein said source is located between said first and second filters.

38. The system of claim 37, wherein said second filter comprises a canopy of an aircraft.

39. The system of claim 38, wherein said aircraft comprises a jet aircraft.

40. The system of claim 35, wherein said detector includes an optical detection bandwidth including wavelengths of light in common with wavelengths of sunlight, said second filter filtering sunlight from said optical detection bandwidth.

41. The system of claim 40, wherein said optical detection bandwidth is defined by said first filter.

42. The system of claim 41, wherein said optical detection bandwidth includes an ultraviolet range and said first filter removes light above a wavelength of 400 nm.

43. The system of claim 41, wherein said optical detection bandwidth includes an infrared range, and said first filter removes light below a wavelength of 1700 nm.

44. The system of claim 35, wherein said second filter comprises a canopy of an aircraft.

45. The system of claim 38, wherein said source of radiation comprises at least one light source mounted on a helmet of a pilot of said aircraft.

46. The system of claim 33, wherein said radiation detector comprises a plurality of coplanar detectors.

47. The system of claim 46, wherein said coplanar detectors are orthogonal with respect to one another.

48. A radiation detector comprising:

a) a plurality of coplanar arrays;

b) a first said array detecting radiation at a first frequency;

c) a second array detecting radiation at a second frequency comprising an integer multiple of said first frequency.

49. The detector of claim 48, further including a third array coplanar with said first and second arrays, said third array detecting radiation at a third frequency comprising integer multiples of said first and second frequencies.

50. The detector of claim 49, wherein said second frequency is a number 5 times the first frequency.

51. The detector of claim 50, wherein said third frequency is a number 25 times the first frequency and 5 times the second frequency.

52. The detector of claim 49, further including a second detector including a second plurality of coplanar arrays perpendicular to said first-mentioned plurality of coplanar arrays.

53. The detector of claim 52, wherein each of said detectors includes three coplanar arrays.

54. The detector of claim 53, wherein each detector includes a first array detecting radiation at a first frequency, a second array detecting radiation at a second frequency comprising 5 times said first frequency, and a third array detecting radiation at a third frequency comprising 5 times said second frequency.