a range of competitively priced coated viewports UHV Conflat, ISO or
KF including antireflection and ITO coatings
Transmission & Anti-Reflection Coatings
All windows and viewports suffer Fresnel reflectivity losses
Reflectivity r = [(n-1)/(n+1)]2
(where n is the refractive index)
which can be on the order of 6% per face for high refractive index
windows such as Sapphire. The reflection is different for p and s
polarised waves, and is a function of angle.
This problem can be a severe limitation in many applications
requiring optical fidelity, viewing of low luminosity against a high
ambient, power transmission etc.
However the problem can be mitigated using anti-reflection coatings.
In the case of Sapphire, due to a fortuitous relationship between
the refractive indices, a considerable improvement can be obtained
using a simple single QWOT (Quarter Wave Optical Thickness) of MgF2.
For more conventional viewport materials such as Kodial and fused
quartz this simple approach would provide less obvious, but still
More complex multi-layer dielectric coatings enable a wide variety
of tailored transmission / reflection characteristics giving for
example virtually zero reflection at a single design wavelength (‘V’
coating) or at two wavelengths (‘W’ coating), or over a wide band
BBAR or a neutral density attenuation, and many others.
A 4 layer Broad Band AR Coating – optimised typically but not
exclusively for the visible range and giving the best general
performance, with a reflected luminosity of only 0.13% and
transmitted luminosity of 99.86%
For applications requiring the best transmission at a single
wavelength, such as high power laser applications, Ceramisis can
provide a ‘V’ Coating having just about zero reflection at a design
wavelength 550, 1064 nm etc. for example
Ceramisis can also provide more exotic coated viewports such as
MgF2, CaF2, ZnSe, with coatings to provide optimum transmission in
the Infrared or UV end of the spectrum
Lead Glass windows are often used in conjunction with vacuum
viewports to reduce the 'leakage' of ionising radiation. However the
high lead content gives the glass a high refractive index, and
therefore a high reflectivity also.
Again the application of an AR coating can considerably improve the
visibility of lead glass windows.
Ceramisis Viewport Range