IR Linear Polarizer.
Although they will certainly transmit infrared light without any problem, visible polarizers do not work in the near infrared. MidOpt near-infrared polarizers 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 lnfrared linear polarizers are sold 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 accidentally move the filter and adversely effect the system's performance. For this reason, MidOpt polarizers are supplied with locking thumbscrews to insure that jarring or accidental movement during cleaning does not result in a change in filter position.