Optical components for ghost image suppression systems and methods
Various techniques are disclosed to provide for reducing undesired reflections in captured images. In one example, a system includes an optical element configured to pass radiation from a scene. The system also includes an imager configured to capture images in response to the scene radiation and reflect at least a portion of the scene radiation to the optical element. The optical element comprises a surface with a convex radius of curvature facing the imager and configured to receive and return the reflected radiation toward the imager in a distribution pattern to reduce a magnitude of the reflected radiation in the captured images. Additional methods, devices, and systems are also provided.
1. A system comprising:
an optical element configured to pass radiation from a scene;
an imager configured to capture images in response to the scene radiation, wherein the imager is a thermal imager disposed in a vacuum package comprising a lid configured to pass the scene radiation to the imager and reflect at least a portion of the scene radiation to the optical element;
wherein the optical element comprises an inner surface with a convex radius of curvature facing the imager and configured to receive and return the reflected radiation toward the imager in a distribution pattern to reduce a magnitude of the reflected radiation in the captured images; and
wherein the optical element is a zero power curved window comprising an outer surface with a concave radius of curvature facing the scene.
2. The system of claim 1 , further comprising:
a housing;
wherein the imager is disposed within an interior of the housing; and
wherein the optical element is a protective window configured to pass the scene radiation to the interior of the housing.
3. The system of claim 2 , further comprising a lens positioned between the protective window and the imager and configured to focus the scene radiation on the imager.
4. The system of claim 1 , wherein:
the optical element comprises an anti-reflective coating configured to pass the scene radiation over a first wavelength range within an absorption wavelength range of the imager; and
the reflected radiation comprises a second wavelength range separate from the first wavelength range and within the absorption wavelength range of the imager.
5. The system of claim 1 , wherein the optical element has a focal length greater than 100 meters.
6. The system of claim 5 , wherein the optical element is comprised of silicon, germanium, zinc sulfide, and/or zinc selenide.
7. The system of claim 1 , further comprising a filter disposed between the optical element and the imager and configured to attenuate the reflected radiation.
8. A method comprising:
passing radiation from a scene by an optical element;
passing the scene radiation to an imager through a lid, wherein the imager is a thermal imager disposed in a vacuum package comprising the lid;
capturing images in response to the scene radiation by the imager;
reflecting, by the lid, at least a portion of the scene radiation to the optical element by the imager;
receiving the reflected radiation at an inner surface of the optical element having a convex radius of curvature facing the imager;
returning the reflected radiation toward the imager by the inner surface of the optical element in a distribution pattern to reduce a magnitude of the reflected radiation in the captured images; and
wherein the optical element is a zero power curved window comprising an outer surface with a concave radius of curvature facing the scene.
9. The method of claim 8 , wherein:
the imager is disposed within an interior of a housing;
the optical element is a protective window; and
the passing by the optical element comprises passing the scene radiation to the interior of the housing by the protective window.
10. The method of claim 9 , further comprising focusing the scene radiation on the imager by a lens positioned between the protective window and the imager.
11. The method of claim 8 , wherein:
the optical element comprises an anti-reflective coating configured to perform the passing over a first wavelength range within an absorption wavelength range of the imager; and
the reflected radiation comprises a second wavelength range separate from the first wavelength range and within the absorption wavelength range of the imager.
12. The method of claim 8 , wherein the optical element has a focal length greater than 100 meters.
13. The method of claim 12 , wherein the optical element is comprised of silicon, germanium, zinc sulfide, and/or zinc selenide.
14. The method of claim 8 , further comprising attenuating the reflected radiation by a filter disposed between the optical element and the imager.
15. A system configured to perform the method of claim 8 , the system comprising:
the optical element;
the imager; and
the vacuum package.
16. A method comprising:
passing radiation from a scene by an optical element to an interior of a housing, wherein the optical element is a protective window;
passing the scene radiation to an imager through a lid, wherein the imager is a thermal imager disposed in a vacuum package comprising the lid, wherein the vacuum package is disposed within the interior of the housing;
capturing images in response to the scene radiation by the imager;
reflecting, by the lid, at least a portion of the scene radiation to the optical element by the imager;
receiving the reflected radiation at an inner surface of the protective window having a convex radius of curvature facing the imager; and
reducing, by the optical element, a magnitude of the reflected radiation in the captured images, wherein the reducing comprises returning the reflected radiation toward the imager by the inner surface of the protective window in a distribution pattern to reduce the magnitude of the reflected radiation in the captured images.
17. The method of claim 16 , further comprising attenuating the reflected radiation by a filter disposed between the optical element and the imager.
18. The method of claim 16 , wherein the optical element is a zero power curved window comprising an outer surface with a concave radius of curvature facing the scene.
19. A system configured to perform the method of claim 16 , the system comprising:
the optical element;
the imager; and
the vacuum package.
20. The method of claim 16 , wherein:
the optical element comprises an anti-reflective coating configured to perform the passing over a first wavelength range within an absorption wavelength range of the imager; and
the reflected radiation comprises a second wavelength range separate from the first wavelength range and within the absorption wavelength range of the imager.