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Thermal imaging device with selectively replaceable telescopic lenses and automatic lens identification

  • US 5,673,143 A
  • Filed: 10/11/1995
  • Issued: 09/30/1997
  • Est. Priority Date: 10/11/1995
  • Status: Expired due to Fees
First Claim
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1. A thermal imaging device comprising:

  • a device housing sealingly defining a chamber therein, said device housing having at least a portion which is magnetically-permeable to allow penetration of an external magnetic field into said chamber; and

    said device housing defining an optical aperture allowing admission of infrared thermal radiation into said chamber, said optical aperture being sealingly closed by a window member which is transparent to thermal radiation;

    a lens assembly having an optical axis, and a respective lens housing removably attachable to said device housing at said optical aperture to align said optical axis with said optical aperture, thus to direct infrared thermal radiation from a viewed scene into said chamber via said optical aperture, said lens assembly including a movable power-adjustment portion movement of which changes a power of telescopic magnification for said lens assembly;

    a magnet fixedly positioned on said lens housing, when said lens housing is attached to said device housing said magnet being in juxtaposition to said magnetically-permeable portion of said device housing;

    a second magnet moving between a first position and a second position dependent upon position of said power-adjustment portion, said second magnet in only one of said first and second positions providing a magnetic field which penetrates into said chamber via said magnetically-permeable portion of said device housing;

    a magnetically-responsive sensor disposed within said chamber in juxtaposition to said magnetically permeable portion of said device housing;

    whereby said magnetically-responsive sensor indicates the presence of said lens assembly at said optical aperture; and

    another magnetically-responsive sensor responding to said magnetic field of said second magnet in said one of said first and second positions to uniquely identify the power setting of said lens assembly.

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