Absorbing dichroic filters
First Claim
1. A dichroic filter, comprising a periodic stack of relatively low index of refraction material (L) and relatively high index of refraction material (H), one of the materials having metal-like properties in a relatively short wavelength region of the visible spectrum and one of the materials having dielectric properties in a relatively longer wavelength region of the visible spectrum, the materials providing a cut-on transition from metal-like absorption to dielectric transmission at the relatively longer wavelength region, for selectively transmitting light in a selected region of the longer wavelength region of the visible spectrum.
2 Assignments
0 Petitions
Accused Products
Abstract
High purity (95-99.5 percent) red, orange and yellow filters are disclosed which comprise a periodic stack of relatively low index of refraction dielectric material (L) such as SiO2 or MgF2 and absorbing relatively high index material such as silicon or Fe2 O3. Together, the low and high index materials provide a high index ratio (typically 1.7 to 2.5). The filters are fabricated according to designs such as (H/2 L H/2)n, typically using only 5 to 7 layers. Despite the very small layer count, these filters provide overall optical performance which is at least the equivalent of all-dielectric filters of 30 or more layers, with color purity that is unachievable by all-dielectric filters and simple low cost design. In addition, our filters have inherently low stress levels and absorb and reflect unwanted light such as blue light. As a consequence, the filters are ideally suited for coating on flexible substrates such as plastics and for coating on lamp envelopes to form red or yellow bulbs which are ideally suited, for example, for use as automobile tail light bulbs, side marker bulbs and turn signal bulbs.
89 Citations
12 Claims
- 1. A dichroic filter, comprising a periodic stack of relatively low index of refraction material (L) and relatively high index of refraction material (H), one of the materials having metal-like properties in a relatively short wavelength region of the visible spectrum and one of the materials having dielectric properties in a relatively longer wavelength region of the visible spectrum, the materials providing a cut-on transition from metal-like absorption to dielectric transmission at the relatively longer wavelength region, for selectively transmitting light in a selected region of the longer wavelength region of the visible spectrum.
Specification