Thin, high-performance UV-reflective filters from 3M are constructed from engineering-grade polymers and do not require a substrate. Based on the St. Paul, Minn., company's Multilayer Optical Film technology, the flexible filters are 20 to 50 µm thick and eliminate the need to bond components individually. The films typically comprise several hundred layers of two polymers, each with its own Suitable for high-end applications, the multilayer polymer filters can be structured to provide a sharp band edge transition between reflection and transmission. These sharp band transmissions are the result of the control of the hundreds of interference layers with a relatively small difference in refractive index. This combination allows the creation of precise transitions with very little side lobe reflection, resulting in improved UV optical density with very low levels of visible color.These UV filters can be designed to block up to about 420 nm, with very little yellowness, improving their applicability for ophthal-mic devices. They can replace existing filters for applications such as projection systems, UV reduction and scintillator detectors.The company says the filters allow a reduction in weight and size when incorporated into photonic products. They achieve more than 99 percent reflectivity at all angles and use the Giant Birefringent Optical design, which prevents any loss of reflectivity.