| CPC G01J 5/53 (2022.01) [G01J 5/061 (2013.01); G01J 5/064 (2022.01); G01J 2005/062 (2013.01); G01J 2005/063 (2013.01); G01J 5/80 (2022.01)] | 14 Claims |

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1. Improved extended area blackbody comprising:
a source plate having a front emitting surface; and
a bottom ledge element disposed in front of and below the source plate for heating air in front of the source plate.
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