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MidOpt filters
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Polarising Filters

Neutral gray laminated glass filters transmit visible light in only one polarization plane and are used to suppress glare from specular surfaces and are available in linear, circular and infrared polarisers in a variety of sizes. Larger sizes, along with custom laser-cut and laminated glass and plastic sheet materials, are also available for polarizing all commonly used light sources. Please contact Adept for specific needs.
• PI035 – IR Linear Polarizer – reduces only infrared glare • PSxxx – Visible and IR Polarizing Sheets for mounting in front of lighting


PR032 – Rotating Linear Polarizer with locking screw
Model
Transmission
Suitable for
Features
PR032
Passes visible (340nm+) and IR
Absorbs UV 200-340nm
 • Reducing glare in the visible spectrum • Locking thumbscrew to prevent jarring or accidental movement


Used to eliminate glare, a linear polarizer in a rotating mount offers flexibility and ease of use. Once the filter is screwed to the lens, the outer portion of the mount rotates freely. This facilitates determining the point where reduction of glare (or the contrast in stress patterns in glass or plastic materials) is maximized. However, because the mount rotates freely, it is also possible for vibration or other inadvertent interference to cause the filter to move from this position and adversely effect the system's performance. For this reason, these polarisers come with a locking thumbscrew to insure that jarring or accidental movement during cleaning does not result in a change in the filter's position.

MidOpt also offers linear polarisers in Slip Mounts to fit over the outside diameter of the front end of a lens and Quick Mounts to fit the inside diameter of the front of a lens. These mounts are usually employed when the lens does not have a filter thread. In both cases, the mount and filter can be easily positioned on the lens so that rotating mounts are unnecessary.

Note: The polarization of light only takes place over the 400-700nm (visible) range; light in the UV or IR is not polarized.
(left) Unfiltered monochrome image. (right) Correctly aligned polarizing filter eliminates reflections.

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PC052 – Circular Polarizer – reduces glare; for autofocus/autoiris lenses
Model
Transmission
Suitable for
PC052
Passes visible (340nm+) and IR
Absorbs UV 200-340nm

• Visible-spectrum applications
• SLR cameras and camcorders with beam splitters

Circular polariser are mainly used in consumer applications, such as with camcorders or SLR cameras that have a beam splitter that sends part of the light coming through the lens to a viewfinder and part to a light meter.

Light entering the exposure meter is partially polarized by the beam splitter. A linear polarizer over the lens would act as a secondary polarizer and block light going to the meter (but not the sensor or film), resulting in incorrect exposures. A circular polarizer overcomes this problem with the addition of a ¼-wave retarder, which rotates the linearly polarized light 90° so that it appears unpolarised to the light meter, resulting in proper exposure.

 

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PI035 – IR Linear Polarizer – reduces only infrared glare
Model
Transmission
Suitable for
PI035
Passes visible (340nm+) and IR, or only IR (two types available)
Absorbs UV 200-340nm
 • 850-2000nm range applications


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 unnecessary.

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PSxxx – Visible and IR Polarizing Sheets mount in front of lighting. Sheets are available in a range of sizes and thicknesses. Please contact Adept for your specific needs.

 

 

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