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EP-4363920-B1 - HEATED CAMERAS AND RELATED METHODS

EP4363920B1EP 4363920 B1EP4363920 B1EP 4363920B1EP-4363920-B1

Inventors

  • FAIRFIELD, NILE E.
  • HALL, WILLIAM J.
  • DISPENZA, JACE
  • TAUBER, Sean
  • OVRUTSKY, DAVID
  • LIN, Stephanie

Dates

Publication Date
20260506
Application Date
20220629

Claims (15)

  1. An apparatus comprising a lens assembly comprising: a front region comprising an entrance window of the lens assembly, and a window structure at the entrance window; a back region; a lens (132) between the window structure and the back region; and a heater (148) coupled to heat the window structure; wherein the lens assembly comprises a reflective surface (150), wherein the front region is on a first side of the reflective surface, the back region is on a second side of the reflective surface, and the reflective surface is configured to reflect thermal radiation generated by the heater, the reflected thermal radiation being reflected towards the first side.
  2. The apparatus of claim 1, wherein the reflective surface is configured to direct at least some of the reflected thermal radiation towards the window structure.
  3. The apparatus of claim 1, wherein the lens is disposed on the second side of the reflective surface.
  4. The apparatus of claim 1, wherein the reflective surface is a surface of an integral member.
  5. The apparatus of claim 1, wherein the reflective surface is integrated with the lens.
  6. The apparatus of claim 1, wherein the lens assembly comprises a barrel (128) comprising a flange (128L) between the window structure and the lens, the flange comprising the reflective surface.
  7. The apparatus of claim 1, wherein the reflective surface comprises an aperture stop defining an entrance pupil of the lens assembly.
  8. The apparatus of claim 1, wherein the window structure comprises a wavelength filter for thermal imaging.
  9. The apparatus of claim 1, wherein the heater comprises a resistive heater.
  10. The apparatus of claim 9, further comprising: a barrel housing (128) that houses the lens and the heater; and a cable (212) inside the barrel housing, the cable extending from the heater towards the back region, for providing electric power to the heater.
  11. The apparatus of claim 1, further comprising an imaging sensor at the back region.
  12. A method comprising: heating by a heater (148) a window structure of an apparatus comprising a lens assembly comprising: a front region comprising an entrance window of the lens assembly, wherein the window structure is located at the entrance window; a back region; a lens between the window structure and the back region; and the heater; a reflective surface (150), wherein the front region is on a first side of the reflective surface, and the back region is on a second side of the reflective surface; and the method further comprises reflecting, by the reflective surface, thermal radiation generated by the heater, the reflected thermal radiation being reflected towards the first side.
  13. The method of claim 12, wherein the reflecting comprises directing at least some of the reflected thermal radiation towards the window structure.
  14. The method of any one or more of claims 12 or 13, wherein the reflecting comprises reflecting at least some of the reflected thermal radiation away from the sensor and/or the lens.
  15. The method of any one or more of claims 12, 13, or 14, wherein: the heater comprises a resistive heater; the apparatus further comprises a barrel housing (128) that houses the lens and the heater; and the heating comprises providing electric power to the heater via a cable (212) inside the barrel housing, the cable extending from the heater towards the back region.

Description

TECHNICAL FIELD The present invention relates to cameras that generated heat to reduce or eliminate ice formation or moisture condensation that can impair image quality. BACKGROUND Ice or moisture can be deposited on camera elements in the optical path due to environmental conditions such as temperature changes, and the deposits may reduce image quality. To alleviate this problem, camera elements can be heated to melt/evaporate ice or moisture, or to prevent or reduce their formation. The present disclosure describes effective techniques associated with such heating. WO 2019/225745 discloses a lens unit 100 including: a cylindrical lens barrel 10; and a plurality of lenses 1-4 which are disposed on the inner circumferential side of the lens barrel 10 and lined up along the axial direction of the lens barrel 10. A heater 40 that generates heat by conduction is disposed between: a flange section (flat section) 1b of the lens 1 which is disposed closest to the object side of the lens barrel 10; and a flange section (flat section) 2b of the lens 2 which is adjacent to the lens 1. US 2017/285335 discloses an imaging system that includes a de-icing assembly. The de-icing assembly may include a de-icing window and a window frame. The de-icing window may be constructed from Float Zone Silicon, single crystal sapphire, and/or germanium. The de-icing assembly may be coupled to a lens barrel of a camera. Heat generated by a heater element of the camera may be conducted via the housing and the lens barrel of the camera to the de-icing assembly. EP 3 352 008 discloses a camera module thin film heater comprising: an electrode; a thin film heating body electrically connected to the electrode and having a variable resistance corresponding to a heating temperature; and an insulating member surrounding the electrode and the thin film heating body. SUMMARY Systems and methods are disclosed herein for preventing, reducing, or correcting image artifacts that could be caused by a heater. According to a first aspect of the present invention, there is provided an apparatus according to claim 1. According to a second aspect of the present invention, there is provided a method according to claim 12. The scope of the invention is defined by the claims. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a camera in accordance with an embodiment of the disclosure.Fig. 2 is a perspective view of a camera with housing removed in accordance with an embodiment of the disclosure.Figs. 3A, 3B, 4A, 4B are perspective views of camera portions in accordance with an embodiment of the disclosure.Fig. 5 is a schematic top view of a camera heater in accordance with an embodiment of the disclosure.Fig. 6 is a top view of a camera heater in accordance with an embodiment of the disclosure.Fig. 7 is a cross sectional view of a camera portion in accordance with an embodiment of the disclosure.Fig. 8 is a flowchart of image correction to remove heater-related artifacts in accordance with an embodiment of the disclosure.Fig. 9 is a flowchart of a setup process (calibration process) for image correction to remove heater-related artifacts in accordance with an embodiment of the disclosure.Figs. 10, 11, 12 show dark field images and pixel value graphs obtained in test results involving an embodiment of the disclosure.Fig. 13 shows a scene image captured in accordance with an embodiment of the disclosure. Embodiments of the invention and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. DETAILED DESCRIPTION Techniques and mechanisms are provided to reduce or correct image artifacts caused by heating the camera. The inventors have observed that heating a camera element can create image artifacts, especially in thermal (thermographic) cameras, due to stray thermal radiation caused by the heater. The inventors provide structural features and image processing techniques to reduce or eliminate such artifacts. More particularly, the inventors have observed that the stray radiation emitted by the heater may heat up other camera elements, e.g. lenses, which can radiate heat towards the camera's imaging sensor, i.e. the sensor that converts thermal radiation to electrical signals to form an image. As a result, the image can be distorted. The problem can be particularly acute if the heater is placed inside the lens barrel, as is done in miniaturized cameras according to some embodiments of the present disclosure, because in such embodiments the