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A large amount of the filters produced today, including Andover standard products, are classified as commercial quality or instrumentation grade and are not acceptable for use in imaging systems.In response to the need for high quality filters, Andover has developed the "Image Quality Filter". Our image quality filters utilize high-quality optical glass, typically Schott® BK-7 and Schott® filter glass. The surfaces of this material are ground and polished to a flatness of 1/4 wave per inch and parallel to 30 arc seconds or better. If necessary, a higher degree of optical quality is available for the more critical applications. To prevent fringe patterns and multiple images, all coatings are deposited onto a single surface and all exterior surfaces are broadband anti-reflection coated for an average reflection of <=0.5