Steerable wide-angle imaging system

• US 4,908,705 A
• Filed: 01/21/1988
• Issued: 03/13/1990
• Est. Priority Date: 01/21/1988
• Status: Expired due to Term

• Current Assignee: Fairchild Weston Systems Inc.
• Original Assignee: Fairchild Weston Systems Inc.
• Inventors: Wight, Ralph
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Kostak, Victor R.
• Application Number:
  US07/146,696
• Time in Patent Office: 782 Days
• Field of Search: 358/109, 358/113, 358/225, 358/88, 358/87, 358/229, 250/578, 250/239
• US Class Current: 348/145
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G01C 11/025 by scanning the object
• CPC Class Codes: G01S 3/782 Systems for determining direction or deviation from predetermined direction
• CPC Class Codes: G02B 13/00 Optical objectives specially designed for the purposes specified below with variable magnification in general G02B15/00
• CPC Class Codes: G02B 13/06 Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
• CPC Class Codes: H04N 23/58 Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/701 Line sensors
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

An electro-optic system which is advantageous for low altitude, high speed aerial reconnaissance. A linear imager is movably positioned in the focal plane of a fixedly mounted wide-angle lens system. The fore-aft motion capability of the imager can be used to select an optimal viewing angle for recognition, for image motion compensation (to reduce smear), or for other functions.

Claims

1. A reconnaissance system, for mounting in an aircraft, comprising:

a wide-angle lens positioned to image ground-level surface onto a fixed focal plane; and

an electro-optic imager having a substantially one-dimensional imaging area, and movable within the focal plane defined by said lens and having its long dimension oriented substantially normal to the vector within the image of the ground-level surface which corresponds to the flight track of the aircraft; and

one or more mechanical linkages which move said imager within said focal plane to point to a desired strip which is either forward or aft of the nadir of the aircraft.

2. The system of claim 1, wherein a first element of said lens is reduced in size in one dimension, to reduce its field of view in the fore-aft direction.

3. The system of claim 1, wherein a first element of said lens is slabbed in one dimension.

4. The system of claim 1, wherein said lens is substantially apochromatic.

5. The system of claim 1, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

6. The system of claim 1, wherein said lens is fixedly mounted.

8. The system of claim 1, wherein said imager comprises a linear charge-coupled device.

9. The system of claim 1, wherein said imager comprises two linear imagers butted together, said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof.

10. The system of claim 1, wherein said imager comprises a quasilinear charge-coupled device.

11. The system of claim 1, wherein said lens has a field of view greater than 120°

, and wherein the calibrated pincushion distortion of said lens at 60°

off-axis is much less than 3%.

12. The system of claim 1, wherein said lens has a field of view greater than 120°

, and wherein said lens images equal areas onto substantially equal areas.

13. The system of claim 1, wherein said imager sees a field of view greater than 120°

, and wherein the maximum calibrated linear distortion across the width of said imager is less than 10%.

14. The system of claim 1, wherein outputs of said imager are pixel-shifted to compensate for image motion components parallel to the long dimension of said imager.

15. The system of claim 1, wherein a transparent cover is hermetically sealed in a fixed relationship to said imager, and said cover moves with said imager.

16. The system of claim 1, wherein said imager is mounted to a thermoelectric cooler, and said cooler moves with said imager.

7. The system of claim wherein said imager comprises a charge-coupled device.

17. An imaging system for producing an image with substantially high resolution and low distortion throughout, the imaging system comprising:

(a) a wide-angle lens positioned substantially fixedly, the lens imaging equal areas onto substantially equal areas;

(b) an electro-optic imager having an imaging area which is elongated in one dimension; and

(c) one or more mechanical linkages which controllably move said imager

(1) within the focal plane defined by said lens,

(2) in a direction substantially normal to the long dimension of said imager,

(3) to image a desired portion of the field of view of said lens which can selectably be either

(i) entirely on one side of the center of the field of view of said lens, or

(ii) entirely on the other side of the center of the field of view of said lens,

wherein the electro-optic imager contributes to the formation of the image having substantially high resolution and low distortion throughout.

18. The system of claim 17, wherein a first element of said lens is reduced in size in one dimension, to reduce its field of view in the fore-aft direction.

19. The system of claim 17, wherein a first element of said lens is slabbed in one dimension.

20. The system of claim 17, wherein said lens is substantially apochromatic.

21. The system of claim 17, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

22. The system of claim 17, wherein said lens is fixedly mounted.

23. The system of claim 17, wherein said imager comprises a linear charge-coupled device.

24. The system of claim 17, wherein said imager comprises two linear imagers butted together, said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof.

25. The system of claim 17, wherein said imager comprises a quasi-linear charge-coupled device.

26. The system of claim 17, wherein said imager sees a field of view greater than 120°

, and wherein the maximum calibrated linear distortion of said lens across the width of said imager is less than 10%.

27. The system of claim 17, wherein outputs of said imager are pixel-shifted to compensate for image motion components parallel to the long dimension of said imager.

28. The system of claim 17, wherein a transparent cover is hermetically sealed in a fixed relationship to said imager, and said cover moves with said imager.

29. The system of claim 17, wherein said imager comprises a charge-coupled device.

30. The system of claim 17, wherein said imager is mounted to a thermoelectric cooler, and said cooler moves with said imager.

31. The system of claim 17, wherein said lens is positioned substantially fixedly to look through an external window.

32. A reconnaissance system, for mounting in an aerial platform, comprising:

a wide-angle lens positioned substantially fixedly;

an electro-optic imager having an imaging area which is elongated in one dimension; and

one or more mechanical linkages which controllably move said imager

within the focal plane defined by said lens,

in a direction substantially normal to the long dimension of said imager,

to image a desired portion of the field of view of said lens which can selectably be either entirely on one side of the center of the field of view of said lens or entirely on the other side of the center of the field of view of said lens.

33. The system of claim 32, wherein said lens is fixedly mounted.

34. The system of claim 32, wherein outputs of said imager are pixel-shifted to compensate for image motion components parallel to the long dimension of said imager.

35. The system of claim 32, wherein said lens is substantially apochromatic.

36. The system of claim 32, wherein said imager comprises a charge-coupled device.

37. The system of claim 32, wherein said imager comprises two linear imagers butted together, said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof.

38. The system of claim 32, wherein said imager comprises a quasi-linear charge-coupled device.

39. The system of claim 32, wherein said lens has a field of view greater than 120°

, and wherein the calibrated pincushion distortion of said lens at 60°

off-axis is much less than 3%.

40. The system of claim 32, wherein said lens has a field of view greater than 120°

, and wherein said lens images equal areas onto substantially equal areas.

41. The system of claim 32, wherein said imager sees a field of view greater than 120°

, and wherein the maximum calibrated linear distortion across the width of said imager is less than 10%.

42. The system of claim 32, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

43. The system of claim 32, wherein a transparent cover is hermetically sealed in a fixed relationship to said imager, and said cover moves with said imager.

44. The system of claim 32, wherein said imager is mounted to a thermoelectric cooler, and said cooler moves with said imager.

45. The system of claim 32, wherein a first element of said lens is reduced in size in one dimension, to reduce its field of view in the fore-aft direction.

46. The system of claim 32, wherein said imager comprises a charge-coupled device having a substantially linear imaging area.

47. The system of claim 32, wherein said lens is positioned substantially fixedly to look through an external window.

48. The system of claim 32, wherein

said imager comprises two linear imagers butted together,

said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof,

and pixel values are regenerated for locations falling between said respective extremities, where no respective imaging areas exist.

49. The system of claim 32, wherein said desired portion of the field of view of said lens can be either before or behind the nadir of said aerial platform.

50. A method for providing images of a ground-mounted object using high-speed low-level overflight, comprising the steps of:

flying an air vehicle near the ground-mounted object,

wherein said air vehicle includes a wide-angle lens mounted to image ground-level objects onto a substantially fixed focal plane, and includes an electro-optic imager, having a substantially one-dimensional imaging area, movably mounted within the focal plane defined by said lens, said imager having its long dimension oriented normal to the vector within the image of the ground-level surface which corresponds to the flight track of the aircraft;

moving said imager within said focal plane, normal to the principal axis of said imaging area thereof, until the strip of ground imaged onto said imager is at a viewing angle, with reference to said air vehicle, which is substantially optimal for image understanding under the actual and expected environmental conditions and features to be recognized;

and outputting image data from said imager.

51. The method of claim 50, wherein outputs of said imager are pixel-shifted to compensate for image motion components parallel to the long dimension of said imager.

52. The method of claim 50, wherein said lens is substantially apochromatic.

53. The method of claim 50, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

54. The method of claim 50, wherein said lens is fixedly mounted.

55. The method of claim 50, wherein said imager comprises a charge-coupled device.

56. The method of claim 50, wherein said imager comprises a quasi-linear charge-coupled device.

57. The method of claim 50, wherein said lens has a field of view greater than 120°

, and wherein the calibrated pincushion distortion of said lens at 60°

off-axis is much less than 3%.

58. The method of claim 50, wherein said lens has a field of view greater than 120°

, and wherein said lens images equal areas onto substantially equal areas.

59. The method of claim 50, wherein a transparent cover is hermetically sealed in a fixed relationship to said imager, and said cover moves with said imager.

60. The method of claim 50, wherein said imager is mounted to a thermoelectric cooler, and said cooler moves with said imager.

61. The method of claim 50, wherein said lens is positioned substantially fixedly to look through an external window.

62. The method of claim 50, wherein

said imager comprises two linear imagers butted together,

said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof,

and pixel values are regenerated for locations falling between said respective extremities, where no respective imaging areas exist.

63. A method for providing images of a ground-mounted object using high-speed low-level overflight, comprising the steps of:

flying an air vehicle near the ground-mounted object,

wherein said air vehicle includes a wide-angle lens mounted to image ground-level objects onto a substantially fixed focal plane, and includes an electro-optic imager, having a substantially one-dimensional imaging area, movably mounted within the focal plane defined by said lens, said imager having its long dimension oriented normal to the vector within the image of the ground-level surface which corresponds to the flight track of the aircraft;

moving said imager within said focal plane, normal to the principal axis of said imaging area thereof, in the same direction as the apparent image motion on said focal plane;

and outputting image data from said imager.

64. The method of claim 63, wherein a first element of said lens is reduced in size in one dimension, to reduce its field of view in the fore-aft direction.

65. The method of claim 63, wherein said lens is substantially apochromatic.

66. The method of claim 63, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

67. The method of claim 63, wherein said lens is fixedly mounted.

68. The method of claim 63, wherein said imager comprises a charge-coupled device.

69. The method of claim 63, wherein said imager comprises a linear charge-coupled device.

70. The method of claim 63, wherein said imager comprises a quasi-linear charge-coupled device.

71. The method of claim 63, wherein said lens has a field of view greater than 120°

, and wherein said lens images equal areas onto substantially equal areas.

72. The method of claim 63, wherein said imager sees a field of view greater than 120°

, and wherein the maximum calibrated linear distortion across the width of said imager is less than 10%.

73. The method of claim 63, wherein outputs of said imager are pixel-shifted to compensate for image motion components parallel to the long dimension of said imager.

74. The method of claim 63, wherein said imager is mounted to a thermoelectric cooler, and said cooler moves with said imager.

75. The method of claim 63, wherein said lens is positioned substantially fixedly to look through an external window.

76. The method of claim 64, wherein

said imager comprises two linear imagers butted together,

said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof,

and pixel values are regenerated for locations falling between said respective extremities, where no respective imaging areas exist.

77. A method for providing images of a ground-mounted object using high-speed low-level overflight, comprising the steps of:

flying an air vehicle near the ground-mounted obJect,

wherein said air vehicle includes a wide-angle lens mounted to image ground-level objects onto a substantially fixed focal plane, and includes an electro-optic imager, having a substantially one-dimensional imaging area, movably mounted within the focal plane defined by said lens, said imager having its long dimension oriented normal to the vector within the image of the ground-level surface which corresponds to the flight track of the aircraft;

moving said imager within said focal plane, normal to the principal axis of said imaging area thereof, in a direction opposite to the apparent image motion on said focal plane;

and outputting image data from said imager.

78. The method of claim 77, wherein a first element of said lens is reduced in size in one dimension, to reduce its field of view in the fore-aft direction.

79. The method of claim 77, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

80. The method of claim 77, wherein said lens is fixedly mounted.

81. The method of claim 77, wherein said imager comprises a charge-coupled device.

82. The method of claim 77, wherein said imager comprises two imaging areas which are substantially abutted at respective extremities thereof.

83. The method of claim 77, wherein said lens has a field of view greater than 120°

, and wherein the calibrated pincushion distortion of said lens at 60°

off-axis is much less than 3%.

84. The method of claim 77, wherein said lens has a field of view greater than 120°

, and wherein said lens images equal areas onto substantially equal areas.

85. The method of claim 77, wherein said imager sees a field of view greater than 120°

, and wherein the maximum calibrated linear distortion across the width of said imager is less than 10%.

86. The method of claim 77, wherein said lens is positioned substantially fixedly to look through an external window.

87. The method of claim 77, wherein the air vehicle is operated in a terrain-following mode, and wherein said imager is moved opposite to the apparent image motion within the focal plane at a time when the air vehicle is making a pop-up.

88. A method for providing three-dimensional images of a ground-mounted object, comprising the steps of:

flying an air vehicle near the ground-mounted object,

wherein said air vehicle includes a wide-angle lens mounted to image ground-level obJects onto a substantially fixed focal plane, and includes an electro-optic imager, having a substantially one-dimensional imaging area, movably mounted within the focal plane defined by said lens, said imager having its long dimension oriented normal to the vector within the image of the ground-level surface which corresponds to the flight track of the aircraft;

moving said imager within said focal plane to image the ground-mounted object at a first relative position while the object is ahead of said aircraft;

and moving said imager within said focal plane to image the ground-mounted object at a second relative position while the object is less far ahead of said aircraft;

and deriving three-dimensional information regarding the object from correlation of data provided by said imager at said first position and at said second position.

89. The method of claim 88, wherein said lens has a field of view which is more than 135 degrees wide in at least one direction.

90. The method of claim 88, wherein said lens is fixedly mounted.

91. The method of claim 88, wherein said imager comprises a substantially linear charge-coupled device.

92. The method of claim 88, wherein said imager comprises two linear imagers butted together, said linear imagers having respective imaging areas which are substantially abutted at respective extremities thereof.

93. The method of claim 88, wherein said lens has a field of view greater than 120°

, and wherein the calibrated pincushion distortion of said lens at 60°

off-axis is much less than 3%.

94. The method of claim 88, wherein said lens has a field of view greater than 120°

, and wherein said lens images equal areas onto substantially equal areas.

95. The method of claim 88, wherein said imager sees a field of greater than 120°

, and wherein the maximum calibrated linear distortion across the width of said imager is less than 10%.

96. The method of claim 88, wherein, at said second relative position, the object is behind said aircraft.