Patent ID: 8786856

Claim:
A method of monitoring combustion properties in an interior of a boiler of the type having walls comprising a plurality of parallel steam tubes separated by a metal membrane, the method comprises: a) providing first and second penetrations in the metal membrane between adjacent tubes on opposite sides of the boiler without relocating the adjacent tubes; b) projecting a beam of light through a pitch optic comprising a pitch collimating lens and a pitch relay lens both residing outside the boiler interior, the pitch relay lens being optically coupled to the first penetration to project the beam into the boiler interior and being configured to have a focal point at the first penetration; c) receiving the beam of light with a catch optic residing outside the boiler interior, the catch optic comprising a catch relay lens optically coupled to the second penetration and a catch collimating lens optically coupled to the catch relay lens; d) determining a strength of the collimated received beam of light; and e) aligning at least one of the pitch collimating lens and the catch collimating lens to maximize the strength of the collimated received beam.