How to Analyze Your Tolerance Results

Many times it is useful to analyze your tolerances in detail. In Zemax's tolerance analysis, you may save the tolerance results for each Monte Carlo file, or you may save each tolerance in the sensitivity analysis individually in Zemax file format. This article describes how to take a closer look at what Zemax does internally to model each and every tolerance in your design.

Authored By: Dan Hill

Introduction

Zemax offers a built-in tolerancing feature which you may use to perform a complete and accurate tolerance analysis of your optical system.

Although Zemax performs the calculation of each tolerance “behind the scenes,” Zemax also gives you the option to view what it is doing more closely; the operation of the tolerance feature is not always transparent.

There are two different methods to saving the modifications that Zemax made to your lens file to calculate the change in criteria as a function of the specified tolerance(s).

The first option may be defined in the Tolerance Data Editor as a tolerance control operand. The SAVE tolerance control operand can be used after any tolerance you would like to inspect in more detail. For example, suppose that you had a tolerance operand TEDX (tolerance on element decenter in X) in the Tolerance Data Editor. After reviewing the resulting sensitivity analysis, the results did not appear to make sense.

As a result, you may edit the Tolerance Data Editor by adding a SAVE command after the TEDX operand. The next time the tolerance analysis is run, Zemax will save the file used to compute the TEDX tolerance, which you may view as a Zemax lens file.

Applying the SAVE Tolerance Control Operand

To demonstrate, consider a single element for which you would like to know how the RMS Spot Radius changes for a tilt tolerance about the X axis.

FILE: Single Element Lens.ZMX (attached to last page of article)

TETX is the operand for tolerance on element tilt about the X axis. In this case, the single element has a tilt tolerance of +/- 0.5 degrees.

Running the tolerance with the following settings (note that Paraxial Focus is set as the compensator):