Patent Document ID: 4124803
Application ID: 05753193
Patent Flag: 1

Claim One:
1. Structure comprising: a radiant energy source; a first sensing means: first path means for transmitting radiant energy from said source to the surface of a material, and for transmitting radiant energy reflected from said surface to said first sensing means, said first sensing means producing a first intermediate signal representing the radiant energy from said source reflected by said surface; a second sensing means; second path means for transmitting radiant energy from said source through substantially the same environment passed through by the radiant energy transmitted by said first path means to said second sensing means, said second sensing means producing a second intermediate signal representing the radiant energy transmitted through said second path means. a third sensing means; third path means for transmitting radiant energy from said source to the surface of a reference standard, and for transmitting the radiant energy reflected by said reference standard to said third sensing means, said third sensing means producing a third intermediate signal representing the radiant energy reflected by said reference standard; a fourth sensing means; fourth path means for transmitting radiant energy from said source to fourth sensing means, said fourth sensing means producing a fourth intermediate signal representing the radiant energy of the said radiant energy source only; means for processing said first, second, third and fourth intermediate signals to provide a measure of the radiant energy reflected by said surface of a material, said measure being independent of environmental contaminants which interfere with the radiant energy transmitted through said first path means; also independent of degradation of said radiant energy source.