This article explains:

• How to analyze stray light in Non-Sequential ZEMAX via use of the Filter String
• What Filter Strings are and how to write them.
• How to locate rays with specific properties via the Filter String.
• How to use Filter Strings with the Layout plots, Detector Viewer, and Ray Database Viewer.

This article is accompanied by a sample file which is used to demonstrate some of the powerful uses of the Filter String.  The file is available via download from the very last page of the article. 

Veiling glare is a term that is often used in the field of imaging system design. Technically, veiling glare is stray light that reaches the sensor plane of an imaging system, and it can cause a decrease in the imaging system’s performance.

Often,  a full non-sequential treatment is needed for accurate results. However, for many optical imaging systems, a first-cut look at forward scattering effects is all that is really required. This article will show how to make just such a preliminary veiling glare measurement using tools that are already built into ZEMAX. This analysis will require just a few minutes to perform, and will give very useful results.

This article describes how to model a partially reflective surface which diffusely scatters a fraction of incident energy into a specific distribution.