We propose an imaging system and method for leakage detection in the consumer electronics manufacturing industry that uses Schlieren imaging with a collimated beam emitted from a white/color LED as a back illumination light to image, locate and characterize a flow of pressurized gas with a refractive index different than that of ambient air from certain leak areas of a sealed device under test (DUT). In particular, the Schlieren imaging system includes a collimated light, a knifeedge spatial filter and a 4F telescopic imaging system used to create an image of the DUT, which is pressurized and monitored for leaks. When a leak is present and in the monitored plane of the DUT, contrast variation reveals the presence, location, and characteristics of the leak. For example, we can evaluate a waterproof/leakproof mobile device for leakage between layers of modules, such as leaks in the housing of a waterproof electronics case. This detection method can allow identification and characterization of leak points via visual identification, where we use a fiber-coupled LED as a light source to create high quality collimated light for the best Fourier filter effect for a 4F imaging system. Our application shows that LED light has sufficient chromatic quality to act as a light source for a Schlieren imaging system with high sensitivity.
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