Light-Tight Filter Wheel

  • Light-Tight Filter Wheel for Ø1" Filters
  • Compatible with SM1 Lens Tubes and 30 mm Cage System


(Filter Not Included)

LTFW6 Shown with SM1 Lens
Tubes and PDA10DT Detector

Related Items

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FTLW6 Rear Panel Removal
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To switch filter positions, lift the cover on the side of the housing and manually turn the wheel.


  • Light-Tight Housing Ideal for Sensitive Measurements
  • 6 SM1-Threaded Filter Housings Hold Ø1" (Ø25 mm) Filters up to 0.25" (6.4 mm) Thick
  • 30 mm Cage System and SM1 Lens Tube Compatible
  • 8-32 and M4 Adapters Included for Mounting to Ø1/2" Posts

The LFTW6 Six-Position Light-Tight Filter Wheel is designed for situations where a manual filter wheel must be completely isolated from sources of stray light. The outer cover seals out sources of stray light, making this filter wheel ideal for sensitive measurement systems using a detector, such as a PMT.

The filter wheel is equipped with six SM1-threaded filter holders designed for holding Ø1" or Ø25 mm plano optics up to 0.25" (6.4 mm) thick. The rotation mechanism is located under a hinged cover, as shown in the photo to the right. It has a knurled edge to aid in rotating between filters between the various positions. In addition, the wheel edge is also engraved with numbers to identify the filter locations. Once the proper filter is in position, a magnet holds the cover closed. The filter wheel uses a spring-loaded detent mechanism to lock into place at each location and center the filter within the clear aperture.

The outer cover features internal SM1-threaded (1.035"-40) input and output apertures surrounded by 4-40 tapped blind holes for mounting rods for our 30 mm cage system. By attaching SM1 lens tubes to both the entrance and exit apertures, an entire system can be made light tight. Please note that since the SM1 threading extends all the way through the cover, we only recommend threading in components, such as our standard Ø1" lens tubes, that have an external SM1 thread depth of 0.12" or less, or damage to the components may occur.

The plate on the back side of the housing needs to be removed to insert or remove filters. It is secured with three button-head screws that can be loosened with a 0.05” (1.3 mm) hex key, as shown in the two photos below right. Six SM1RR retaining rings are included for securing the filters in the wheel. An SM1 spanner wrench can be used to tighten the retaining rings.

The bottom of the filter wheel is M6 x 0.5 threaded, but adapters with either 8-32 or M4 threads are included to provide post mounting. Additional adapters are available; please contact Tech Support for details.

FTLW6 With Cage System
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The LTFW6 with a 30 mm cage assembly attached.
FTLW6 Rear Panel Removal
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The Filters are held in SM1-Threaded mounts and secured with SM1RR retaining rings.
FTLW6 Rear Panel Removal
Click to Enlarge

The filter access panel is removed by unscrewing three button-head screws with a 0.05" (1.3 mm) balldriver.

Posted Comments:
robert.crabbs  (posted 2015-04-17 13:46:48.327)
I have several of these LTFW6 filter wheels on field-able optical systems. In a short time the screws have rusted due to environmental exposure (salt air). Could you please send me the screw sizes for the filter replacement cover and the main cover so I can procure stainless steel screws and replace? Thanks
cdaly  (posted 2015-04-20 09:15:43.0)
Response from Chris at Thorlabs: The filter access panel is held on by three 1/8" long, #2-56 threaded, button head cap screws. The back cover is held on by four 3/16"long, #4-40 threaded, button head cap screws.
joachim.fischer  (posted 2013-05-15 07:21:05.917)
Hi there! how good is the positioning repeatility of the filter wheel? Is it possible / advisable to use this filter wheel as manual pinhole exchanger in confocal microscopy? Then a repeatability for ~30µm should be given...
sharrell  (posted 2013-05-15 17:00:00.0)
Response from Sean at Thorlabs: Thank you for using our feedback tool. Unfortunately we do not have the repeatability specification for our filter wheels. These items were designed for filters, where the centerline repeatability does not need to be as tightly controlled as needed for your application. If you would like to test the LTFW6 in your application, you may always purchase it and return it if you find it is not what you are looking for.
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Light-Tight Filter Wheel

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LTFW6 Support Documentation
LTFW6Customer Inspired! Light-Tight Filter Wheel for Six Ø1" Filters