Wavelength Beam Splitters: Edge Filters

Wavelength Beam Splitters: Edge Filters, Long Wave Passes, Short Wave Passes, Hot and Cold Mirror

Wavelength Beam Splitters are know by many names: Beam Splitters(splitting the spectrum rather than Intensity), Edge Filters,  Long Wave Passes, Short Wave Passes, and some are specifically know as Hot and Cold Mirrors:  It is customary to specify the 50% peak Transmission point as a way of designating the location of the splitter.  It is also necessary to specify the overall transmission and rejection zones(Band Width about either side of the slope).  In addition, the slope of the Transmission curve can be defined together with a, so-called, Cut-On point for Long Wave Passes and Cut Off point for Short Wave Passes. The Cut-On and Off points are typically defined as 5% of the peak transmission   

All Cascade Optical Corporation's Dielectric coatings pass MIL-C-48497 and can be made to pass even the severe abrasion requirements of MIL-C-675.  We have a Environmental test Lab department to qualify each and every coating run


Various Applications for Wavelength Splitters

Below are some featured Coatings where customers wanted a specific splitter to meet the requirements of their application.  To the left, the image illustrates a blue Long Wave Pass we coated for AAO



Covert Black Out IR Lights For The Military

Please pay attention to the round object located on the front left hand side of the tank.  The IR Radiation, goes right through the green paint and lights up the battlefield for NIR cameras.  Below, you will find the specifications and spectral graph of a typical Covert Long Wave Pass


 Covert Long Wave Passes Spectral Graph 

T<.01% Or OD4 from 380-780nm

T=50% @970nm

Tavg>75% from 1000-1200nm



Hot and Cold Mirrors are special cases of Short and Long Wave pass filters

Dental Mirrors: It can be advantageous to utilize both Hot and Cold Mirrors in Conjunction with One Another:

Dental Hot Mirror(Front Optic):  Typical Hot Mirror reflects wavelengths longer than 700nm and transmit spectrum below 600nm. In this case, 650nm is usually selected as a Half-Maximum T point.  This Hot Mirror can be used as the front cover of the illumination system.  Since some of the red is being removed by the cut-off point at 600nm the overall appearance is an intentional, "cool",  bluish tinge(towards the patient).

Dental Cold Mirror(Rear Optic): Would be the inverse of the Hot Mirror and would be mounted behind the light to reflect useful visible light while transmitting the IR(HEAT) away from the patient and allowing for a temperature sustainable work environment

Now a days, there are many variations on this configuration and with the invention of the low IR emitting LED it may not even be necessary.  Some only have a cold mirror with the light source pointed towards it, eliminating the need for the Hot Mirror cover(See picture to the right)

Submit Specifications below: