This is a frequently asked question. To answer this question, let's slightly discuss how spherical reference works.When calculating Huygens PSF with Spherical Reference, OpticStudio will first trace rays to image surface and then "go back" to exit pupil like below.Then each ray interception point on the exit pupil will be considered as point source that radiate spherical waves and interfere on the image plane. This is called spherical reference.On the other hand, when in planar reference, each ray is simply considered as a plane wave and still interfere on the image plane, which is same as spherical reference.

I'm going to plot diff between two operands vs thickness by using the feature Universal Plot, but the analysis window always show 'Error in operand parameters', how to avoid this error?

I'm running a sensitvity tolerancing analysis, with the option Separate Fields/Configs unchecked. My question is on which field of view did the analysing result based?  And what's the difference between check and uncheck this option? 

Question: When using Sequential Mode with the 'Afocal Image Space' option enabled, the units for the Spot Diagram become angular (milliradian). What angle is this referring to?

Question:  I'm trying to use the API to connect to OpticStudio. I'm using the default template script to establish a connection. When I run the script, I get an error message "License Check Failed" or "License is not valid for ZOSAPI use".   

I'm trying to write a ZPL macro in Notepad but I can't figure out how to save the file with the .zpl extension. Every time I try to save, the file name ends up looking like "MyMacro.zpl.txt". How can I change this?

What does it mean to do a virtual propagation of rays?

Why is the nominal criterion value different from my Merit Function value in some cases? Is there a different analysis feature in OpticStudio that the nominal criterion is supposed to match up to? If not, then how is it being computed?

I thought OpticStudio was supposed to utilize multi-threading for a faster optimization process. Why is my optimization running as a single-threaded process? Is this a setting I could change?

I'm working in a wide angle system and would like to ignore the stop setting so that different fields can have different stop locations. How can I do this?

The Help file defines Radiant Intensity as “The incoherent intensity of the ray in cosine space (Radiant Intensity) This is the sum of the ray intensity divided by the solid angle subtended by the pixel." The question I have is how this solid angle subtended by the pixel is defined?

OpticStudio seems to have four accepted values for the mode flag under a "Birefringent In" surface: 0, 1, 2, 3. What are they for, and when do I use them?

What is the best way to reference a surface or object in ZPL so that the macro still works even when the numbering changes because surfaces/objects are inserted or deleted?

What are the s- and p-polarization states? How do I make my incoming beam s-polarized?  

I am trying to save my Non-Sequential system as an archived file (ZAR) but the file is very large. I know that the ZAR file type is a compilation of several different files that help define the lens file but can I safely remove certain files to reduce the overall file size?

I want to use Importance Sampling to trace scattered rays, but when I do, no rays are traced. How do I fix this without changing my optical design?

I am currently working on a Professional edition of OpticStudio and wish to import a Zemax Part Designer file (.ZPO) into my optical design. However, I am finding that the option to import an object of type “CAD: Zemax Part Designer” is only available in the Premium edition of OpticStudio. Can I import my .ZPO file or do I have to work on a Premium edition of OpticStudio?

What are the benefits of Express View? What are its limitations?

How can I model an elliptical beam in a sequential system?

Does OpticStudio have a preferred compiler that I need to use in order to create my own source?

When I open an archived (.ZAR) file, I get a pop-up referencing existing files. Which option should I choose? Do I always have to overwrite files with the same name, or can I merge them?

I’m building a system in Non-Sequential Mode but keep getting “Geometry error” on the screen when I include layout rays. How do I fix this?

I am working with a system that has a user-defined DLL surface and want to obtain the settings. The ZOS-API recognizes that I am using a user-defined DLL but is not returning the correct file as defined in my code.

Is there a way to model and analyze a system using physical optics calculations instead of a ray trace?

I'm trying to optimize a system with a partner but our results keep coming back different from one another even though we are using the same operands and variables. Why is this happening?