Laser Sensor Technology, Inc.

Jon V Hokanson

Barry W Reed

Ekhard Preikschat

Thomas W Montague

Oliver S Hamann

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.

System for acquiring an image of a multi-phase fluid by measuring

The present invention describes an optical technique for analyzing undiluted, multi-phase fluid flows as typically encountered inside reactor vessels or flow lines in the chemical industries. In particular the technique uses a pulsed, coherent light source and measures the back-scattered light collected over a wide scattering angle. A light beam is relayed via a set of lenses down a long probe tube, through a window at a probe tip to illuminate the material that is passing past the window. The light beam is pulsed to 'freeze' the motion of the particles streaming past the window. The backscattered light is collected by the same set of optics and is focused on the front surface of a CCD chip. The lens closest to the front window has a short focal length with a large numerical aperture to collect the back-scattered light over a wide range of backward angles, thereby increasing the detection sensitivity to larger particles, which lie behind and are partially obscured by the myriad of smaller particles closest to the window. The probe tube is inserted through an insertion assembly so that the front viewing window is in direct contact with the material flow, and can be positioned so that the flow will provide a continuous and representative stream of material past the window. Best measuring conditions are obtained by placing the probe window at a modest angle of 30.degree.-45.degree. into the flow. The preferred embodiment combines imaging technology with a specific probe configuration, which is optimized for use in the chemical process industries.

Apparatus and a method are disclosed for determining the sizes of particles entrained in a fluid over a relatively wide range of sizes and determining the distribution of particles in a plurality of size increments. A sample of particles is fed into a drop tube, allowing the particles to be distributed at a relatively low density and fall through a sensing region defined at an intermediate point in the drop tube. A laser diode produces coherent light that is focused with a lens, forming a sheet of coherent light that is directed transversely through transparent sides of the drop tube toward a lens that focuses the sheet of coherent light on a photodetector. A laser intensity control circuit maintains a constant light intensity output from the laser diode when no particle is present in the sensing region and compensates for ambient light. When a particle in the size range of 32.mu. to 4000.mu. falls through the sensing region, a chord around the particle is illuminated by the relatively thin sheet of coherent light, and the level of an electrical signal produced by photodetector is reduced in direct proportion to the portion of the sheet of coherent light that is occluded by the particle. A peak value of the pulse is thus a measure of the size of the particle. A pulse discrimination circuit detects pulses produced by a plurality of particles in the sensing region, preventing such multiple particles from being analyzed or counted. After the size of a particle is determined, a counter increments the count in an appropriate channel, each channel corresponding to one of plurality of different successive ranges that together cover the total size range of the particle analyzer.

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Redmond, WA, United States of America

Jon V Hokanson