Hi Girish

Sorry just a question about II Tube because I am not sure I understood. Are you modelling that component in OptiStudio or are you expecting to analyse the distortion with the OpticStudio models of the objective and eyepiece but measures of II Tube?

The distortion grid in our software is a comparison between the ray trace of chief rays and the ray trace of the same rays through a reference ABCD matrix. That ABCD matrix is calculated with rays that come from a very small region centered upon the reference field position.

So maybe to find a reference for the whole system, we could imagine replacing the II Tube by an ABCD matrix. That would give the reference. 

Then to evaluate the full distortion of the system, we have to find a way to model a transfer function that would represent the distortion. You could try to set up a model for the II Tube and optimize to find a surface that could create the right transfer. I suppose it depends how complex the shape of the distortion is. 

It is just a first thought so please let me know if I misunderstood.

Just for reference, we also have a macro for a more generalized distortion grid: 

Maybe a modification of this macro could make the trick.