I have a lens system that contains tilts and decenters. However, when I print out the paraxial setup (PXC) for the lens, or trace paraxial rays (PXT) I get answers that seem incorrect.

For example, the Effective Focal Length (EFL) listed when I choose PXC appears incorrect. What is the problem?

Synopsis

Paraxial constants - for a system with tilts and decenters

Solution

"Note that OSLO has two different forms of commands to calculate paraxial constants: PXC & PXT These commands calculate paraxial parameters using paraxial rays. If you have tilts and decenters, items such as the calculated EFL may appear to be incorrect. *PXC & *PXT These commands calculate paraxial parameters using real rays. Parameters such as EFL should appear ""correct"" even if you have tilts and decenters. Please Note: How OSLO should handle Effective Focal Length (EFL) is a debatable issue. In classic optical texts, EFL is defined as a paraxial parameter and calculating it using commands such as PXC should be correct. However, when optical engineers integrate tilts and decenters into their systems, they sometimes expect the calculation of EFL to incorporate these "non-paraxial" system features, hence the *PXC command might be more appropriate in some cases. Note that OSLO uses the PXC command as a "base" command to many other menu commands, toolbar commands and optimization operands within OSLO. If your system contains tilts and decenters, you should be careful of how you utilize the concept of EFL."