Motic Instruments Inc. Canada
October 06, 2006
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3.21 Neutral Density Filters
Neutral density filters equally reduce the intensity of all wavelengths of light. These filters
are used for reducing the intensity of the exiting light to prevent photo-bleaching of the
specimen.
Relationship between the ND filters and the brightness
Filter
ND2 (T=50%)
ND4 (T=25%)
ND16 (T=6%)
3.22 Heat absorbing filter
The heat-absorbing filter is placed in front of the light source to reduce heat transfer to
the excitation filter, and damage to the interference filter coatings.
When utilizing the infrared excitation method remove the heat-absorbing filter, as it will
not transmit the near infrared and infrared light.
3.23 Filter
Blocks
A cube shaped modules that hold a matched set of fluorescence filters including
excitation (EX), barrier-emission (BA) and a dichroic mirror (DM).
The excitation filter allows transmission of light at wavelength within the absorption
spectrum of the dye and rejects light at wavelengths within the emission spectrum of the
dye, which could be reflected by the specimen and incorrectly detected as emission
energy.
Barrier filter allows the transmission of light at wavelengths within the emission spectrum
of the dye and rejects and rejects light at wavelengths within the absorption spectrum of
the dye, which could be detected as emission energy.
Dichronic mirror is placed at 45º angle relative to the incoming excitation light, the
dichroic mirror performs two functions: it reflects the shorter wavelength exciting
radiation light to the specimen and transmits the longer wavelength fluorescence.
