A typical microscope has three basic filters: an excitation filter (or exciter), a dichroic beamsplitter (or dichroic mirror), and an emission filter (or emitter). Many filters work by absorbing light, while others reflect unwanted light, but pass a selected region of wavelengths. The color temperature of light can be fine-tuned with filters to produce a spectrum of light having the characteristics of bright daylight, the evening sky, indoor tungsten. A Dichroic Filter is a type of filter used to transmit or reflect light, depending on the wavelength; light of a specific wavelength range is transmitted, while light of a different range is reflected or absorbed (Figure 4). Dichroic filters are commonly used for longpass and shortpass. An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. Learn more about different optical coatings.
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