1. Field of the Invention
This invention relates generally to dichroic filters, and, more particularly, to flexible dichroic filters formed of multiple layers comprising silicon and carbon chemical elements.
2. Description of the Related Art
The term dichroic is derived from the Greek word dikhroos, which means two-colored. When used in the optical arts, the term dichroic refers to any optical device which can split a beam of light into two beams with differing wavelengths. Dichroic color filters selectively transmit light with a small range of colors (i.e., a frequency or wavelength range) while reflecting other colors of light. Dichroic color filters may be formed by layering multiple thin films or coatings over a surface of a transparent material. The layers or coatings are formed used materials having different refractive indices and are applied in thicknesses of one-quarter or one-half a selected wavelength. The wavelength or frequency bands that are transmitted and/or reflected can be controlled by varying the thicknesses and/or the refractive indices of the layers. For example, conventional dichroic optical filters are based on a quarter wave stack design, in which alternating layers of high and low refractive index materials are deposited on a transparent substrate in quarter wave optical thicknesses. Thus, a filter can be designed to transmit specific wavelengths and reflect those which are undesirable.
Conventional dichroic optical filters are formed of a relatively large number of layers. For example, more than 20 layers of alternating high and low refractive index material may be used to form a conventional dichroic optical filter. Consequently, the deposition time required to form the layers of a conventional dichroic optical filter may be relatively large and the resulting structure may have relatively low mechanical stability. Thus, conventional dichroic filters formed of a large number of layers may be stress inherent and relatively expensive to build. Furthermore, conventional dichroic optical filters are formed using multiple layers of metal oxides that are produced by physical vapor deposition.