Abstract: An in-situ imaging system suitable for analyzing particles or droplets contained in process reactor vessels or pipelines at full process concentrations is disclosed. The system includes a light source capable of high peak power output operated in a pulsed mode that is located inside of a probe. The light from the light source is coupled into an optical fiber. The light is carried by the optical fiber to a lens system near the end of the probe which focuses the light through a window to the area which coincides with the field of view in the focal plane of the imaging optics. The imaging optics collect the light which is back-scattered from particles or droplets, magnifying the image and projecting it onto an image detector such as a CCD array.