Meaning
Non-destructive imaging methods utilize low-coherence light to capture high-resolution, cross-sectional images from within the internal structure of translucent materials. The method of optical coherence tomography uses an interferometer to compare the backscattered light from internal material boundaries with light from a reference arm. In the plastics industry, this technology provides real-time, high-precision measurements of multi-layer coextruded films, clear plastic packaging, and medical tubing.
It allows manufacturers to verify internal dimensions and barrier layer thicknesses without cutting or damaging the product.
Depth Profiling
Optical interferometry enables the measurement of internal features by analyzing the time delay of reflected light. A light source emits a broad spectrum of light into the sample, and the reflections from different material boundaries are collected. By comparing the phase shift of these reflections against the reference path, the instrument determines the precise depth of each interface.
This setup provides sub-micron axial resolution, making it suitable for analyzing thin polymer coatings and micro-molded parts.
Layer Determination
Multi-layer polymer films rely on individual layer thicknesses to provide specific barrier properties against gas and moisture. Continuous monitoring using this tomographic technique ensures that each layer is dispensed at the correct thickness across the entire width of the film. It allows operators to adjust the extruder screw speeds to prevent barrier failure, which would compromise the shelf-life of packaged foods.
Defect Detection
Internal voids, contamination, and delamination can compromise the structural integrity of a molded plastic part. Scanning the part with this optical method reveals internal defects before the product leaves the factory. This reduces the risk of in-field failures in high-reliability applications such as medical catheters and automotive housings.
