Optical Filters for Electronics

Optical filters are devices that selectively transmit light of different wavelengths (seen as different colours in the spectrum) usually implemented as plane glass or plastic devices in the optical path. They are either dyed in the bulk or have interference coatings. They have a number of applications and are essential in fluorescence microscopy and spectroscopy. There are two basic types of optical filters: absorptive and interference/dichroic filters. Absorptive filters are made of glass with compounds, which absorb some wavelengths and transmit others. The compound can be added to plastic to produce gel filters. Dichroic filters consist of a glass substrate with optical coatings, which reflect the unwanted portion of light and reflect the rest. They tend to be used for precision scientific work. Etalons are another variation with transparent fibres whose polished ends act like mirrors. Other types of filters include infrared and ultraviolet filters. Apart from scientific research, optical filters are also used in many optical instruments. Cameras and photography equipment make use of them too. They can be seen in the colouring of stage lighting in the theatre. They can be used for eye protection in welding helmets and sunglasses. Etalons are mainly manufactured for separating the wavelengths of channels in telecommunications networks.