@Luc.van Vught 

I had a quick look as well and here is some complementary information.

SLAB

I didn’t check but what you say makes sense, its probably not important.

GLAS

The values 1.5 and 40 look suspiciously like refractive index and dispersion, but of course they would be wrong for N-BK7. Interestingly enough, if you change the solve type to Model Glass and then back to Fixed. The LDE still shows N-BK7, but in the ZMX file you get (I’m using the default wavelength of 0.55um):

  GLAS N-BK7 0 0 1.5168000344999999 64.167336237499995 -0.00089999999999999998 0 0 0 0 0

which makes me think once again that those two parameters (third and fourth) are the refractive index and dispersion. The fifth parameter could be dPgF. However, I don’t think it matters when you use glasses from catalogs. I could be wrong but, my guess is that for catalog glasses OpticStudio just uses the name to find the glass in the corresponding catalog. So instead, I think you should make sure that the definition of N-BK7 in the glass catalog files are the same (\Documents\Zemax\Glasscat\SCHOTT.AGF).

OEMA

It seems related to the mechanical diameter of the lens. I have it appear if I have a Chip Zone and a Mech Semi Dia greater than the sum of Clear Semi Dia and Chip Zone. What the final flag does however, I do not know.

Hope this helps and take care,

David

Hi David & Luc,

The SLAB is a Surface Label and is applied to new surfaces in the order there were entered into the LDE.  So if you add surfaces from the top to bottom vs bottom to top, you will have different SLAB values for the exact same geometry in the LDE.  The SLAB was added for bookkeeping, primarily for OpticsBuilder, so a developer can have a little more information about the last surface they added.

As David mentioned, the GLAS only considers the first entry (the glass name) only when you’re using an AGF glass catalog; these extra values past the glass name are only used when entering glass as a MILSPEC or when using solves.  So as long as you’re using the same glass SCHOTT.AGF catalog the dispersion will be the same.

The difference between 0 & 1 in the OEMA is the scale factor when using a pickup solve.  This value is ignored unless the number after the “0.5” is set to 1 (this means that the Mechanical Semi-Diameter has a pickup solve).  If this value is 0, then all the values past this 0 are meaningless.

Basically, when OpticStudio saves a file, there are several different states (fixed, variable, pickup, macro) each surface can have.  When OpticStudio initializes a surface, it has to allocate memory for all the different states, but OpticStudio doesn’t validate the contents of the memory location until that given state becomes active.  So simply reading out the text of a ZMX file doesn’t paint the full picture of what the active state for each surface is.  A better approach would be to create a series of metrics (MFE operands and Analysis Windows), run a regression test against each file, and compare the outputs of the files.

Hi @David.Nguyen and @MichaelH, thank you for your quick replies and the explanation. I'm happy to see that the differences that I ran into were not relevant to this case.

@MichaelH, I of course agree that the best way to compare files is to create a series of metrics and compare those. I started there and initially had some differences, but could not directly figure out their origin. To solve that, I initially started to compare the .zmx files before I remembered that there is a built-in file comparer that directly shows the differences. As a result, I knew about differences in the .zmx files that were not apparent in the file comparer, but your explanation solved it fully!

Thank you both for your time!