Pyrometer with sighting window cleanliness monitor

Claim 1

Apparatus for measuring temperature of a high temperature irradiant mass, said apparatus comprising: (a) pyrometer means for measuring temperature of said irradiant mass including: (i) a first housing closed at one end and having a sighting window at an opposite end, said sighting window having an outside surface subject to environmental matter; (ii) pyrometer detector means within said first housing for producing a signal which varies proportional to the irradiant mass temperature and an optical error induced by the environmental matter on said outside surface of said sighting window; (iii) lens means within said first housing for focusing an irradiant image of said irradiant mass on said pyrometer detector means; and (iv) said first housing fitted within an adjustable mount in a second housing, (b) sighting window cleanliness monitor means for detecting sighting window cleanliness including: (i) monitor light assembly means for generating a stable source of light; (ii) first light conducting fibre optic means within said second housing and outside said sighting window for transmitting light from said monitor light assembly means first through the environmental matter on said outside surface and thereafter through said sighting window into said pyrometer detector means; and (c) circuit means with means for indicating the need for correcting the irradiant mass temperature signals from said pyrometer detector means due to optical error induced by the environmental matter on said outside surface of said sighting window.