Ray paths in a non-sequential system can be very complex, especially when ray splitting is allowed. In many cases, it can be useful to limit the ray paths that are observed either in the Layout plot or on the Detector Viewer.

When ZEMAX traces a ray, it records exactly what happens to that ray. For example, the ray may reflect from object 13, split into two at object 46, etc. Filter strings allow you to identify specific characteristics of the rays that you want to see.

ZEMAX offers many filter strings that can be used to provide limitations on ray paths - either during the ray trace itself, or when viewing the results in the Layout plot or Detector Viewer - and supports the ability to combine filter strings using logical operands. More information may be found in section of the ZEMAX manual entitled “The filter string”, located in the chapter of the manual entitled “Non-Sequential Components”.

In this article, a few examples will be provided to illustrate the use of logical operands in constructing filter strings for isolating specific rays.