Dichroic filters with low nm per degree sensitivity

摘要

Multilayer thin film dichroic filters composed of alternating layers of high (H) and low (L) refractive index have three groups, a lower group next to the substrate having a ratio Ra of high and low index layers Ra1; a second mid group having a ratio Ra of high and low index layers Ra2; and a third upper group having a ratio Ra of high and low index layers Ra3; and the ratios have the relationship Ra1<Ra2<Ra3. Such filters exhibit improved angle sensitivity and wavelength transition values, and are useful for example in color projection displays.