Filters0 pages

Filters

Filters

Artifex

Engineering

Filters are optical elements with specific spectral transmission characteristics. They are used to
modify the properties of a light source or to block unwanted wavelengths of light.
There are two principle types of optical filter: absorption filters and dielectric filters.
Absorption filters (colour filters) function on the basis of choosing a glass recipe with
chromophoric constituents which absorb a specific range of wavelengths. Typically these are
long pass edge filters, but some bandpass types with limited functionality are available. Note that
this filter type may fluoresce when used for blocking UV light.
Dielectric filters absorb very little light. The functionality is based on reflection of the unwanted
spectral regions based on optical interference within the layer structure of the filter coating. In
order to reduce the number of coating layers - and thus the cost - a combination may be made
by dielectric coating a colour glass substrate. This is common for some bandpass filters.
The following table gives an overview of the main criteria for deciding between these two filter
types.

Price

Power

Angle

Handling

Tolerance

Absorption

Low

Heating due to
absorption:
may break at
high power

Dielectric

High in Small
volumes. Low
to mid in high
volumes

Withstand high
optical power
due to low
absorption

Artifex Engineering e.K.
Dortmunder Str. 16-18
26723 Emden, Germany

Thickness

Dysfunction

May fluoresce
when blocking
UV light

Wide angle
tolerance

Level of
blocking
depends on
thickness.
Typ. 2-3mm

Functional
spectrum blue
shifts with angle

May be very
thin eg
0.5mm

Managing Director: Dr. Steven Wright
Registry Number: HRA 200036

None

Reflection

RoHS
Conform

Low

Many types "No"
but with "legal
exeption" status

Low in
transmission
region, high in
blocking region

Yes

Tel: +49-(0)4921-58908-0
eMail: sales@afx-eng.de
Web: http://www.afx-eng.de/