Operation Manual

62
DEFINITIONS OF FILTER TERMINOLOGY
Bandpass Filters
Bandpass filters transmit a band of wavelengths and block all light above and below the specified
transmission range. These filters are characterized with respect to optical performance by their centre
wavelength (CWL) and bandwidth, also referred to as the full width at half of maximum transmission
(FWHM). (See Figure Below)
CWL
Center wavelength
For optical bandpass filters, the arithmetic means of the cut-on and cut-off wavelength at 50% of peak
transmission.
DCLP
Dichroic Longpass.
DCXR
Dichroic Longpass, extended reflection including the UV.
FWHM
Bandpass filters are usually named by their filters center wavelength (the arithmetic means of the
wavelengths at 50% of center peak transmission) and by range of wavelengths (bandwidth) of light they
transmit at 50% peak transmittance (full width half maximum, FWHM). Example D350/50x is an
interference filter with maximal transmission at 350nm and transmits light from 325 and 375nm. (See
Figure Below)
GFP
The Green Fluorescent Protein (GFP) from the jellyfish Aequoreavictoriais used as a fluorescent
indicator for monitoring gene expression in a variety of cellular systems, including living organisms and
fixed tissues.
The wild type GFP has a major excitation peak at a wavelength of 395 nm and a minor one at 475 nm.
Its emission peak is at 509 nm which is in the lower green portion of the visible spectrum.
Due to this widespread usage different mutants of GFP have been engineered over the last few years:
Color mutants have been obtained from the GFP gene as well: in particular the cyan fluorescent
protein (CFP) and the yellow fluorescent protein (YFP) are two colour variants employed for
fluorescence resonance energy transfer (FRET) experiments.