A method for inspecting small holes in a material is disclosed. The method comprises directing a light source through the holes in the material, and then focusing the light passing through the material onto a CCD detector. The focusing techniques allow for a reduction in the size of the image which must be inspected, thereby increasing sample throughput, while still allowing for detailed inspection of the hole number and quality. Methods of producing an aerosolization container and device comprising membranes which pass such an inspection are also provided.