An excitation filter is a high quality optical-glass filter commonly used in
fluorescence microscopy and
spectroscopic applications for selection of the excitation wavelength of light from a light source. Most excitation filters select light of relatively short wavelengths from an excitation light source, as only those wavelengths would carry enough energy to cause the object the microscope is examining to fluoresce sufficiently. The excitation filters used may come in two main types — ''short pass filters'' and ''
band pass filters''.
Variations of these filters exist in the form of ''
notch filter
In signal processing, a band-stop filter or band-rejection filter is a filter that passes most frequencies unaltered, but attenuates those in a specific range to very low levels. It is the inverse of a ''band-pass filter''. A notch filter is ...
s'' or deep blocking filters (commonly employed as
emission filters). Other forms of excitation filters include the use of
monochromator
A monochromator is an optics, optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is .
Uses
A device that can ...
s,
wedge prisms coupled with a narrow slit (for selection of the excitation light) and the use of
holographic
Holography is a technique that allows a wavefront to be recorded and later reconstructed. It is best known as a method of generating three-dimensional images, and has a wide range of other uses, including data storage, microscopy, and interfe ...
diffraction grating
In optics, a diffraction grating is an optical grating with a periodic structure that diffraction, diffracts light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffractio ...
s, etc.
or beam diffraction of white laser light into the required excitation wavelength (selected for by a narrow slit)">beam_diffraction.html" ;"title="or beam diffraction">or beam diffraction of white laser light into the required excitation wavelength (selected for by a narrow slit)
An excitation filter is commonly packaged with an emission filter and a dichroic beam splitter in a cube so that the group is inserted together into the microscope. The dichroic beam splitter controls which wavelengths of light go to their respective filter.
References
Optical filters
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