Dynamic Measurement of density using terahertz radiation with real-time thickness measurement for process control

摘要

A method of determining a density of a roller compacted ribbon 230 is disclosed. The method comprises compacting dry pharmaceutical powder between press rollers (125, Fig 1) of a roller compactor to produce a compact ribbon 230. A thickness at a point on the compact ribbon is determined in a non-invasive manner after it has rolled out from in between the press rollers. The compact ribbon is passed through a gap in between a terahertz emitter 220 and a terahertz detector 240. The method comprises determining a refractive index at the point on the compact ribbon using a measurement value from the terahertz emitter and the terahertz detector and a measured value for the thickness at the point. Finally, the method comprises computing a density of the compact ribbon at the point using a value of the refractive index. The thickness may be determined by passing the ribbon through a gap between two laser micrometers 250. The method may employ a terahertz time-domain spectroscopy technique which employs determining a time-of-flight duration of a radiation pulse emitted by the terahertz emitter 220.