Cage System Iris Diaphragms

  • 16 mm, 30 mm, or 60 mm Cage System Compatible Irises
  • Continuously Variable Lever-Actuated Aperture
  • Button Head Lever Allows Actuation while Iris is Installed


For 30 mm
Cage Systems


For 60 mm
Cage Systems

Application Idea

CP20S Iris in a Cage System with
KCB1C Right-Angle Kinematic Mount and
CP33 Cage Plate Holding an SM1L10 Lens Tube


For 16 mm Cage Systems

Related Items

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Thorlabs’ Cage System Irises are designed for use within a cage system. The button head lever on these irises clears the fourth cage rod, allowing for aperture adjustments within the cage system.


  • One-Piece Irises for 16 mm, 30 mm, or 60 mm Cage System
  • Continuously Variable Iris Diaphragms
    • SP8D: Ø0.7 mm to Ø8.0 mm Aperture
    • CP20D: Ø0.8 mm to Ø20.0 mm Aperture
    • LCP50D: Ø2.0 mm to Ø50.0 mm Aperture
  • Ultra-Thin Cage Plate Design
    • SP8D: 0.23'' (5.7 mm) Thick
    • CP20D: 0.28" (7.0 mm) Thick
    • LCP50D: 0.40" (10.1 mm) Thick
  • Black-Anodized Aluminum Housing Limits Reflection

These lever-actuated, continuously variable, cage-system-compatible iris diaphragms are designed to provide smooth operation over many thousands of cycles. These irises are mounted in ultra-thin, cage-system-compatible plates. Three cage rods are engaged with locking screws that accept a 0.05" (1.3 mm) hex key for the SP8D or a 5/64" (2.0 mm) hex key for the CP20D and LCP50D. If replacement setscrews are needed for the SP8D, we offer SS4B013 brass setscrews, which use a 0.05" (1.3 mm) hex. The steel leaves that comprise the iris are actuated by a button head lever that clears the fourth cage rod, as shown in the video to the right, allowing for operation within a cage system. The SP8D, CP20D, and LCP50D irises have maximum apertures of Ø8.0 mm, Ø20.0 mm, and Ø50.0 mm, respectively, and are permanently installed in the cage plates.

In addition to the cage system irises sold on this page, our SM-threaded ring-actuated irises can also be utilized in a cage system with the use of an SM-threaded cage plate. However, the cage system irises featured on this page offer thinner profiles and larger maximum apertures than the equivalent ring-actuated irises. For non-cage system use, we also offer post-mountable irises, SM-threaded lever-actuated irises, and unmounted irises with no mounting holes.

Posted Comments:
David Melenberg  (posted 2021-04-22 15:02:10.927)
Dear Thorlabs Team, as part of my research project, I am looking for an aperture that can be rotated to the center of the post as well as provide a way to integrate into the cage system. This is supposed to be used to adjust the optical axis of the setup, as well as to align subsequent parts more precisely. I have noticed that there is no such product in your catalog. Therefore, I have the suggestion to add a thread (counterbore) to the Cage System Iris Diaphragms product line on one side to mount the diaphragms to a post. My special wish would be to realize this for the model CP20S. It would certainly be useful for the other diaphragms in the product line. I thank you very much in advance and hope that you could implement my idea. With warm regards cand. Ba.Sc. David Melenberg University of Lübeck
YLohia  (posted 2021-04-22 03:39:12.0)
Hello David, thank you for your feedback and suggestion. We will consider offering such a product in the future.
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Cage System Iris Diaphragms

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SP8D Support Documentation
SP8D16 mm Cage System Iris Diaphragm (Ø0.7 - Ø8.0 mm)
CP20D Support Documentation
CP20D30 mm Cage System Iris Diaphragm (Ø0.8 - Ø20 mm)
LCP50D Support Documentation
LCP50D60 mm Cage System Iris Diaphragm (Ø2.0 - Ø50.0 mm)