Filter mounts for varifocal lenses

Categories: LensesPublished On: March 15th, 20249.9 min read
Nigel Paine

Traditionally varifocal lenses do not feature a filter mount thread at the front.  This is because the surveillance industry mainly does not have the need to fit a filter.  However high quality varifocal lenses are becoming increasingly popular for use in industrial, broadcast and medical applications.  All these industries may well have a requirement to attach a ND, polarising, band pass filter to improve image quality or simply a skylight filter for protection.  As such it is important to be able to have the ability to attach these filters and SeeSense can offer a series of solutions.

Theia Technologies ML610 with filter mount

Firstly and most importantly our partner Theia Technologies has always offered a high quality range of innovative C and CS mount varifocal lenses which are extensively used  to meet the exacting requirements of machine vision, intelligent transportation, security and the other imaging applications mentioned above.  These applications are often more demanding and may require the use of a filter to adjust the light or simply to protect the lens from damage.

The Theia Technologies FMT3555 filter mount is designed to slip on to lenses with a 35mm barrel diameter and fastened by tightening a series of small sharp-point grub screws.  Specifically the FMT-3555 is designed for use with Theia Technologies 4-10, 6-10 and 2.3mm lenses and the FMT-3555S is machined slightly thinner to fit the 12-50mm lens series.  They allow any M55 x 0.75mm thread external filter such as a band-pass or polarising filter to be added to the system.

The advantage of this system is that you can fit interchangeable filters on to the lens.  SeeSense can also offer a range of filters designed with a slip mount rather than a filter thread. Unlike the Theia adapter these have the filter permanently to the slip ring.

If your camera system requires a high quality lens with an adjustable angle of view AND the ability utilise a filter then please CONTACT SEESENSE and we will happy to advise.

Theia Technologies FMT3555 lens Filter mount
Theia Technologies SL1250 with FMT3555 filter mount