Looking through optics.scad, there are rms_f50d13 and rms_infinity_f50d13 options that set different parameters, and in the comments:
“tube_length is the distance behind the objective’s “shoulder” where the image is formed. This should be infinity (safe to use 9999) for infinity-corrected lenses, or 150 for 160mm tube length objectives (the image is formed ~10mm from the end of the tube).”
The provided transmission illumination optics module appears to be the finite-conjugate variety only, and the build script seems to confirm this. Even the reflection version has the short path length.
When configuring the cartesian version of the microscope, selecting the infinity optics version requires a taller base due to the longer optics module. Looking at the delta and cartesian optics modules side by side the delta one is clearly shorter, even though the optics path should essentially be the same. Is this how it’s supposed to be?