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The normalized field and pupil coordinates (Hx, Hy, Px and Py respectively) of a ray are often used to indicate to ZEMAX exactly which ray is desired for analysis.  For example, the Ray Trace Calculation (via Analysis > Calculations > Ray Trace) requires the specification of Hx, Hy, Px, and Py, as do many of the Merit Function operands.

Ray Trace Settings

Although the ray trace calculation and merit function operands can return very useful information about a given ray, it is also helpful to have a qualitative feel for how a specific ray traverses through your optical system.  This very concept may be applied to the various layout plots in ZEMAX via the RAYLIST.

The layouts in ZEMAX (excluding the 2D Layout) support a number of different Ray Patterns, including XY Fan, X Fan, Y Fan, Ring, Random, Grid, and List.  By choosing List as the “Ray Pattern,” the rays within the layout are traced according to a simple text file.

Selecting List as Ray Pattern

This text file is entitled, “RAYLIST.TXT,” and is located in the main ZEMAX directory.  Note that the filename and directory MUST remain the same.  Any changes made to the filename or the directory in which it is saved will not be recognized by ZEMAX.

The RAYLIST.TXT file is simply of ASCII format, and supports two distinct methods for defining rays, each of which is discussed in more detail in the following pages of this article:

 FORMAT SUMMARY PAGE # 
 IMPLICIT  Rays are defined by the normalized pupil coordinates  2
 EXPLICIT  Rays are defined by their starting coordinates, direction cosines, and wavelength.  3