Although they will certainly transmit infrared light without any
problem, visible polarisers do not work in the near infrared and
MidOpt near-infrared polarisers are for use in the 850-2000nm
range. The extinction ratio over this range is 1,000:1 to 10,000:1;
polarizing efficiency is 99.9 to 99.99%.
Single substrate infrared linear polarisers are available in
rotating mounts but are also available in "fixed" mounts.
Once the filter is screwed into the lens, the upper portion of
the mount that contains the linear polarizer can be easily rotated
to find the optimum setting.
Because the mount rotates freely, it may be possible to move
the filter accidentally and adversely effect the system's performance.
For this reason, polarisers are supplied with locking thumbscrews
to insure that jarring or accidental movement during cleaning
does not result in a change in filter position.
The appropriate filter position can be set by first screwing
the filter into the mount all the way, and then while observing
the image, rotating the filter until the glare disappears or is
reduced as much as possible.
MidOpt also offers infrared linear polarisers in Slip
Mounts (to fit over the outside diameter of the front of a
lens). These mounts are usually employed when the lens does not
have a filter thread. In these cases, the mount and filter can
be easily positioned on the lens such that rotating mounts are