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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
CP02 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
    • CP20S: Ø0.8 mm to Ø20.0 mm Aperture
    • LCP50S: Ø2.0 mm to Ø50.0 mm Aperture
  • Ultra-Thin Cage Plate Design
    • SP8D: 0.23'' (5.7 mm) Thick
    • CP20S: 0.25" (6.3 mm) Thick
    • LCP50S: 0.33" (8.3 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. The SP8D engages three cage rods with locking screws that accept a 0.05'' (1.3 mm) hex key while the CP20S and LCP50S use a flexure mechanism that tightens using a 5/64" (2.0 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, CP20S, and LCP50S 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 larger apertures and thinner profiles than the 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.

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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)
CP20S Support Documentation
CP20SCustomer Inspired! 30 mm Cage System Iris Diaphragm (Ø0.8 - Ø20 mm)
LCP50S Support Documentation
LCP50SCustomer Inspired! 60 mm Cage System Iris Diaphragm (Ø2 - Ø50 mm)
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