Terahertz imaging

摘要

An imaging system with the ability to produce clear images of deposits inside operating high temperature process equipment such as kraft recovery boilers and power utility boilers uses a terahertz/mm-wave imaging system. This system allows direct inspection capability and the ability to directly measure deposit thickness on tubes and other interior surfaces at all locations within the boiler and precipitator. Terahertz and mm-wave imaging systems employ active imaging in which a beam of terahertz or mm-wave radiation generated within the imaging system is used to illuminate a region of the scene under investigation. The reflected radiation is collected by a lens or mirror system and focused onto a detector that converts the collected radiation into an electrical signal. Both the illuminating beam and the receiving optics are scanned across the scene in a raster fashion to produce a time-varying signal that is converted into an image of the scene.

主权项

1. A terahertz/mm-wave imaging system for producing images and quantitative measurements of internal geometric structures, such as steam tubes and interior walls, inside high temperature industrial process units that are visually inaccessible by infrared imaging owing to obscuration by particle laden gases with strong molecular emission and absorption lines, such as power utility boilers, kraft recovery boilers, cement kilns and petrochemical refinery furnaces, comprising:
a generator for generating an illuminating beam of wave radiation in terahertz/mm electromagnetic spectrum, limited to frequencies of operation within the terahertz /mm wave range at which there is minimal obscuration by suspended particles or molecules in the gas, to illuminate said internal structures within said high temperature industrial process units; a receiver, having a field of view, for collecting a portion of the illuminating beam radiation after reflection from the internal structures inside said units; and electronics/software for converting said collected radiation into an electrical signal, and for interpreting said electrical signal to yield information about said geometric structures, such as the presence and thickness of surface deposits on such structures, wherein said frequencies of operation are selected within the range of 100 GHz to 3 THz but avoids specific frequencies where the gases exhibit strong absorption features; said specific frequencies where the gases exhibit strong absorption features include the strongest such absorption features below 500 GHz at 183.5 GHz, 232.7 GHz, 293.8 GHz, 321.4 GHz, 325.3 GHz, 331.2 GHz, 336.5 GHz, 380.6 GHz, 390.6 GHz, 403.3 GHz, 426.1 GHz, 437.7 to 448.4 GHz, 463.4 GHz, 471.3 GHz, 475.1 GHz, and 488.6 GHz.