Quick Answer: The Iris Diaphragm is an adjustable iris aperture that controls how much light passes into a lens, screen or optical bench set-up. Opening or closing it changes beam diameter and brightness for image formation and alignment experiments.
Last updated: October 2026
Key Features
Adjustable iris aperture
Controls beam diameter and transmitted light intensity
Shows how aperture size affects image brightness and sharpness
Used with light sources, lens holders, optical benches, screens and projection set-ups
Helps explain the iris of the human eye and of optical instruments
Technical Specifications
Specification
Value
Aperture type
Adjustable iris aperture
Primary use
Controlling light passage, aperture size, beam diameter and optical alignment
Operation
Manual opening and closing of the aperture
About This Product
Narrowing the iris shows students what the iris of the eye and of optical instruments does: less light reaches the screen while the beam width and image sharpness change. In focal length and projection set-ups it also narrows the beam so alignment is easier. Enquiries from South Africa, Zimbabwe, Republic of the Congo, Rwanda and United Kingdom for the Iris diaphragm receive an export quotation.
Frequently Asked Questions
How is the Iris Diaphragm adjusted?
Open the aperture gradually to let light through the centre, and reduce it to narrow the beam or lower the transmitted intensity. Do not force the iris mechanism or touch the blades.
