Re: backward ray tracing

Helpful person wrote:
On Feb 21, 11:32 am, surface2air <johnnas...@xxxxxxxxx> wrote:
can any on explain what this phenomenon actually is and why its better
than forward ray tracing.

In analyzing and designing an optical system one should always (if
possible) trace rays towards the short conjugate. This gives better
accuracy in the calculations. (This is easily seen in Zemax which
seems very prone to giving inaccurate answers.)

Interesting. For a straight calculation, with no backward error propagation, I can see that...the incidence angles are smaller and the propagation distance from the first surface is shorter when you're going towards the short conjugate, both of which will tend to reduce the error. Actual ray tracing is so small a task compared with running a GUI, though, that I'm amazed that every code doesn't have some sort of forward-backward algorithm to fix this problem. Matrix solvers use 'iterative improvement' to do much the same thing.

Cheers,

Phil Hobbs
.