Extruded filters bridge the gap between high performance and low cost
By Gail Overton
Vacuum-processing methods such as ion-beam sputtering and plasma-enhanced evaporation produce thin-film optical filters with exceptional environmental stability, tight cutoff wavelengths, and tailored spectral bandwidths or reflection values; however, these methods are not easily scaled for volume and require expensive equipment. And although roll-to-roll co-extrusion and nanolamination processes are specifically geared to high-volume applications such as LED backlight distribution, these techniques lack the layer uniformity, complexity, and quality needed for selective optical filtering in higher-end applications, including optics for point-of-care diagnostics and multispectral imaging.
Bridging the gap between high performance and low cost is a new class of extruded thin-film filters from Everix (Orlando, FL). In a process that combines optical-fiber drawing and plastic-film-extrusion methods to provide precise control of layer thickness and refractive index, Everix is producing complex multilayer interference filters for high-volume markets in which laser damage, thermal drift, and narrower operating temperature ranges are not an issue. For example, their 120-layer blue-blocking notch filter has a bandwidth of 20 nm full-width half-maximum and edge slopes of 10–13 nm (approximately 2%) on both sides of the rejection band. This bandwidth enables its use in high-volume applications in migraine relief, macular-degeneration prevention, and reduction of sleep disruption, fatigue, and eye strain caused by LED displays and lighting at a fraction of hard-coated filter prices. In addition to single-notch filters, multinotch, narrowband, and short- and long-pass filters with high optical densities are in the product pipeline. Contact E. Hooman Banaei at email@example.com.