Online monitoring of pore distribution in microporous membrane

The present investigation describes about the development of a cost effective system for real time monitoring of porosity of ion track etched membranes. The system uses a complementary metal oxide semiconductor (CMOS) image sensor to capture the image of the membranes from the optical microscope's projector lens and a field-programmable gate array (FPGA) chip to process the capture image and transfer the pore distribution result to a LCD display. The porosity of the membrane is measured directly from the distribution of pores in the membrane. In the image processing by FPGA the pixels intensity greater than the threshold value is considered to be due to the presence of pores. This technique canot be utilized in membranes with pore size less than 1 micron due to the limitationof magnification of the optical microscope. The porosities of three gamma ray irradiated thin track etched polycarbonate membranes of pore sizes 5, 8 and 10 μm are determined with the system and calculated to be in the range 8.1-10.5, 2.0-9.8 and 4.9-9.6% respectively. The system is designed at minimum cost and provides more detailed data at a faster rate. Evaluation of the performance characteristics of the setup indicates that is performance is comparable with much costlier systems.