Patent ID: 8238698

Claim:
Optical reflection measurement probe ( 10 ) for process monitoring of a material in a medium, comprising a) a distal end ( 11 ) with a light entrance opening ( 12 ), b) a proximal end ( 13 ) coupled to an evaluation device, c) a rigid sleeve ( 14 ) comprising a first light-guiding connection between the distal and proximal ends of the measurement probe, arranged between the two ends, wherein the light guiding connection involves fibre-optic waveguides or optical waveguide bundles without any flexible sheathing and wherein (d) the measurement probe has, in its distal region ( 11 ) relative to the rigid sleeve ( 14 ) and/or the proximal end ( 13 ), a reduced external diameter, wherein a transition between the rigid sleeve ( 14 ) and the distal region is conically shaped for reducing contamination, wherein the measurement probe has a purging device ( 15 ) with a purging duct arranged in the rigid sleeve ( 14 ) and with a purging opening ( 16 ) arranged in the distal end, proximate to the light entrance opening, wherein the purging duct conveys the same medium as the medium used in the process that is being monitored, wherein the purging can be carried out continuously, at fixed intervals or if cleaning is required and wherein the purging device creates pulsed purges or high-pressure purges.