Non-destructive thickness measurement of optically scattering polymer films using image processing

Abstract

We establish a sample- and data-processing pipeline that allows for high-throughput optical microscope measurement of porous films, provided they are sufficiently optically scattering. Here, self-limiting electrospray deposition (SLED) is used to manufacture scattering films of different morphologies. This technique compensates for the scattering of the films through background subtraction of the reflection image with the transmission image. This process is implemented through a combination of an ImageJ and MATLAB data pipeline; the Canny edge-detector is used as the image-processing algorithm to identify the boundaries of the film. This process is verified against manually measured images; a comparative study between cross-sectional scanning electron microscopy (where scattering effects are diminished) and optical microscopy also verifies that our optical microscopy technique can be used to consistently, non-destructively measure film thickness regardless of film morphology. In addition, this technique can be used in combination with dense film measurements to measure film porosity.