Dichroic Filters

A dichroic filter is a type of optical filter that is designed to selectively transmit or reflect specific wavelengths of light. These filters are made by coating a substrate material with layers of thin film materials that have different refractive indices. The thickness and arrangement of these layers are carefully designed to produce the desired spectral transmission or reflection characteristics.

Dichroic filters are used in a variety of applications, including scientific instruments, laser systems, and imaging systems. They can be used to isolate specific wavelengths of light for analysis or to separate different colors for display or printing. Dichroic filters are also used in lighting systems to create colored effects or to balance the spectrum of light sources.

Sony VPL-HS1 - beam path, consisting of prisms, mirrors, lenses and a series of dichroic filters — Sony VPL-HS1 – beam path, consisting of prisms, mirrors, lenses and a series of dichroic filters

One of the unique properties of dichroic filters is their ability to transmit light at certain wavelengths while reflecting light at other wavelengths. This is known as dichroism, which is the phenomenon of different absorption of light at different wavelengths. This allows dichroic filters to perform multiple functions in a single device, such as separating colors for display or analysis while also reducing unwanted light interference.

Dichroic filters are typically made from glass or plastic materials that have been coated with thin film layers of metal or dielectric materials. The properties of these layers are carefully engineered to produce the desired spectral transmission or reflection characteristics. The coating process is typically performed using vacuum deposition techniques or chemical vapor deposition methods.

This optical element is used to combine monochrome red, green, and blue images into one color projection. Here white light is shone through the element in reverse, leading to pure red, green, and blue beams emitted through the other three faces.

Dichroic filters are versatile optical filters that are used in a wide range of applications. They offer precise spectral control and can be used to isolate specific wavelengths of light, separate colors, or reduce light interference.