To control oil contamination is one of the most important tasks in operating a mechanical device. Oil contamination
level is a quantitative parameter used to determine the level of contamination by measuring the number, sizes and
distributions of solid particles in an oil substance. According to classification standards of particles contamination level,
a novel method with microscopic digital image processing is proposed to measure it. At first the oil sample to be
measured is filtered by a vacuum assisted device to gather the solid particles. The filter paper is placed in between two
glasses, and the microscopic digital images of it are captured by an optical microscope and a Charge Coupled Device
(CCD) camera. The images are then segmented and extracted accordingly. After processing these images, binary images
are produced to facilitate the measurement of particle size distribution, which is used to classify the contamination level.
Thanks to the application of microscopic digital image processing, the proposed method is able to produce a reliable
result with much cheaper expense, which was proven by the results of an experiment.