Abstract

An optical scheme for in situ identification of particulates in fluid such s engine oil, in which a portion of the fluid flow is tapped, fed via a conduit to a pair of optically transparent opposed plates, imaged through the plates, and the fluid returned to the main flow. Imaging is preferably done with a laser and photodetector array, and the output fed to a computer for image processing. Separation between the plates ensures that all the oil therebetween will be in the imaging system's near field.Preferably, the computer counts the number of particles in the oil, and classifies their shape, by scanning the image until it hits an object (i.e. hits an opaque pixel), using known chain code to trace the object's outline, determining the object's aspect ratio, and repeating for each object in the image.One embodiment uses a planar rotary member which is scalloped about its periphery. The scallops act to push oil continuously against an outer casing. The casing has a light source for directing coherent light at the rotary member, which is made reflective. As the rotary member moves in the casing, it carries fluid with it, and packs the fluid against the casing. The gap between the light source and the rotary member then constitutes the passageway which is imaged.