OPTICAL DEVICE FOR CORRECTING GEOSTATIONARY SATELLITE IMAGERY FOR EARTH CURVATURE EFFECTS

• US 20110170797A1
• Filed: 03/08/2010
• Published: 07/14/2011
• Est. Priority Date: 05/01/2006
• Status: Active Grant

• Current Assignee: University Corporation For Atmospheric Research
• Original Assignee: University Corporation For Atmospheric Research
• Inventors: JOHNSON, DAVID B.
• Granted Patent: US 8,189,956 B2
• Time in Patent Office: Days
• US Class Current: 382/275
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 27/0911 Anamorphotic systems
• CPC Class Codes: G06T 3/073 Transforming surfaces of revolution to planar images, e.g. cylindrical surfaces to planar images
• CPC Class Codes: G06T 5/006 Geometric correction correction of chromatic aberrations adapted to be used in an image pickup device containing an electronic image sensor H04N23/10; detecting, correcting, reducing or removing artefacts resulting only from the lens unit, e.g. flare, shading, vignetting or "cos4" H04N25/61
• CPC Class Codes: G06T 5/80 Geometric correction

Abstract

An optical adapter for an imaging system correcting images of spherical or near spherical bodies such as the earth during satellite image collection. An imaging system includes an image collector that collects a two-dimensional image of the body from a distance above the body such as from a satellite in geostationary orbit. The collected image is disk shaped and includes distortion due to earth curvature, primarily in the form of a loss of resolution due to the foreshortening of earth features in a radial direction extending outward from the center of the image disk. The optical adapter receives the collected image, transforms the collected image to correct the distortion, and outputs a corrected image with essentially uniform spatial resolution across the areas for which the correction is applied. An image sensor such as charge-coupled device array senses the corrected image and creates a digital representation of the corrected image.

Claims

1-20. -20. (canceled)

21. An imaging system for use in defining images of a spherical body, comprising:

an optical collector for collecting light so as to define an image of the body from a distance above the body, wherein the collected light defines distorted portions in relation to a plane of said image, said distorted portions being radially spaced apart from a center of the collected light, wherein distortion in the distorted portions is due to curvature of the spherical body or oblique viewing angles, wherein at least some of the radially-spaced, distorted portions extend along a first axis and at some of the radially-spaced, distorted portions extend along a second axis that is transverse to the first axis, and wherein the optical collector is operable to correct at least some of the radially-spaced distorted portions in relation to each of said first and second axes for use in defining an image of the body.

22. The system of claim 21, wherein the optical collector comprises at least one optical component.

23. The system of claim 22, wherein the at least one optical component comprises an aspheric lens or mirror with increasing curvature near an edge portion.

24. The system of claim 22, further comprising:

an image sensor with a receiving surface for receiving the collected, corrected light and generating an electrical signal corresponding to an image of the spherical body.

25. The system of claim 21, wherein the optical collector progressively transforms the radially-spaced distorted portions and substantially continuously transforms the collected light from portions that are relatively near a center of the collected light to portions that are relatively near an edge of the collected light.

26. The system of claim 21, wherein the image defined by the collected, corrected light has substantially uniform resolution.

27. The system of claim 21, wherein the imaging system is mounted upon a satellite for use in geostationary orbit and the optical collector comprises a fixed telescope in geostationary orbit directed straight downward towards the center of the spherical body.

28. The system of claim 21, wherein the correction provided by the optical collector comprises radially stretching segments of the collected light in the distorted portions that are radially spaced apart from a center of the collected light to have a size substantially equivalent to image segments that are near the center of the collected light relative to the distorted portions.

29. The system of claim 28, wherein the image defined by the collected, corrected light has a diameter that is larger than an image that would be defined by light collected by the optical collector without being corrected, by a factor of less than 1.4.

30. The system of claim 21, wherein the image defined by the collected, corrected light has a diameter that is substantially equivalent to or smaller than a diameter of an image that would be defined by light collected by the optical collector without being corrected.

31. The system of claim 21, wherein the correction provided by the optical collector is selected from a group of corrections consisting of equal area correction, curvature correction, equidistant correction, and stereographic correction.

32. The system of claim 31, wherein the optical collector is configured based on a radial stretching factor that defines an amount of stretching applied to the collected light relative to the center of the collected light, and wherein the radial stretching factor is defined by a curve corresponding to the correction selected from the group of corrections.

33. The system of claim 21, wherein the correction of the collected light provided by the optical collector applies pincushion distortion to the collected light.

34. The system of claim 21, wherein the collected light is divided into two or more areas and wherein each of the areas is transformed separately to correct for distortion.

35. The system of claim 21, wherein the collected light is collected at an offset from nadir using conical scanning.

36. The system of claim 21, wherein the optical collector is configured for transforming linear sections of the collected light, and wherein the system comprises a linear array that is conically scanned to gather linear sections.

37. The system of claim 21, wherein the system comprises a linear array that is operated using a pushbroom scan to gather linear sections that are transformed by the optical collector.

38. An imaging system for use in defining images of a spherical body, comprising:

an optical collector for collecting light so as to define an image of the body from a distance above the body, wherein the collected light defines distorted portions in relation to a plane of said image, said distorted portions being radially spaced apart from a center of the collected light, wherein the distortion is due to curvature of the spherical body or oblique viewing angles, and wherein the optical collector is operable to correct at least some of the radially-spaced distorted portions by progressively transforming the radially-spaced distorted portions and substantially continuously transforming the collected light from portions that are relatively near a center of the collected light to portions that are relatively near an edge of the collected light for use in defining an image of the body.

39. The system of claim 38, wherein the optical collector comprises at least one optical component.

40. The system of claim 39, wherein the at least one optical component comprises an aspheric lens or mirror with increasing curvature near an edge portion.

41. The system of claim 39, further comprising:

an image sensor with a receiving surface for receiving the collected, corrected light and generating an electrical signal corresponding to an image of the spherical body.

42. A method for use in defining images of a spherical body, comprising:

collecting light defining distorted portions in relation to a plane of an image defined by said collected light, said distorted portions being distal to a center of the collected light, wherein distortion in the distorted portions is due to curvature of the spherical body or oblique viewing angles, wherein at least some of the distorted portions extend along a first axis and at some of the distorted portions extend along a second axis that is transverse to the first axis; and

correcting at least some of the distorted portions in relation to each of said first and second axes for use in defining an image of the body.

43. The method of claim 42, wherein the correcting step further comprises:

radially stretching at least some of the distorted portions.

44. The method of claim 43, wherein the stretching is performed at a greater rate on segments in the portions near an edge of the collected light and wherein coverage of the image defined by the corrected, collected light extends outward from nadir by an earth angle of less than 65 degrees.

45. The method of claim 43, wherein the stretching is performed such that substantially uniform resolution is provided across the image defined by the collected, corrected light.

46. The method of claim 42, further comprising:

receiving the collected, corrected light on an image sensor.

47. The method of claim 42, wherein the correcting step further comprises:

using at least one optical component.

48. The method of claim 47, wherein the at least one optical component comprises an aspheric lens or mirror with greater curvature near its edge.

49. The method of claim 42, wherein the correcting step further comprises:

progressively transforming the radially-spaced distorted portions and substantially continuously transforming the collected light from portions that are relatively near a center of the collected light to portions that are relatively near an edge of the collected light.