Why Opto Engineering® telecentric lenses do not integrate an iris?
Our TC lenses don’t feature an iris, but we can easily adjust the
aperture upon request prior to shipping the lens, without any additional
costs or delays for the customer. The reasons why our lenses don’t
feature an iris are so many that the proper question would be why other manufacturers do integrate irises?
- adding an iris makes a lens more expensive because of a feature
that would only be used once or twice throughout the product life
- iris insertion makes the mechanics less precise and the optical alignment much worse
- we would be unable to test the lenses at the same aperture that the customer would be using
- iris position is much less precise than a metal sheet aperture: this strongly affects telecentricity
iris geometry is polygonal, not circular: this changes the inclination
of the main rays across the FOV, thus affecting the lens distortion
- irises cannot be as well centered as fixed,
round, diaphragms: proper centering is essential to ensure a good
telecentricity of the lens
- only a circular, fixed, aperture makes brightness the same for all lenses
adjustable iris is typically not flat and this causes uncertainty in
the stop position, which is crucial when using telecentric lenses!
is a moving part that can be dangerous in most industrial environments.
Vibrations could easily disassemble the mechanics or change the lens
- the iris setting can be accidentally changed by the user and that would change the original system configuration
- end-users prefer having fewer options and only a few things that have to be tuned in a MV system
smaller than what is delivered by OE as a standard will not make sense
as the resolution will decay because of diffraction limit; on the other
hand, much wider apertures would cause a reduction of the field depth.
- the standard aperture of OE lenses is meant to optimize image resolution and field depth.