ZEMAX Users' Knowledge Base - http://www.zemax.com/kb
How to Analyze Your Tolerance Results
http://www.zemax.com/kb/articles/109/1/How-to-Analyze-Your-Tolerance-Results/Page1.html
By Dan Hill
Published on 19 June 2006
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 indidvidually 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.
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.
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):
FILE: Single Element Lens.ZMX (attached to last page of article)
Page 1 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
In the Sensitivity Analysis of the tolerance output, we can see the criteria value as well as the
change in criteria as a function of our TETX tolerance.
In this case, the tilt did not affect the RMS Spot Radius very much, but we can review what
ZEMAX has done more closely by saving the file ZEMAX internally constructed to perform this
perturbation.
In the Tolerance Data Editor, under the TETX line, insert a SAVE tolerance control operand.
Page 2 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
The SAVE command allows you to save the previous tolerance to a ZEMAX Lens File with the
specified “File #.” A file will be saved for both the maximum and minimum tolerance. The file
names will be TSAV_MIN_xxxx.ZMX and TSAV_MAX_xxxx.ZMX for the min and max tolerance
analysis, respectively, where xxxx is the integer number specified in the Int1 column. In this
case, the integer number is 5, so the minimum tolerance file will be TSAV_MIN_0005.ZMX.
Note that the saved file is saved into the same directory as the current lens file.
Run the tolerance analysis once more with the SAVE operand in place (use the same tolerance
settings).
Once the analysis is complete, open the TSAV_MIN_0005.ZMX file from the appropriate
directory. Note the modifications made to the Lens Data Editor. To tilt the element about the
X axis, ZEMAX inserted a pair of Coordinate Break Surfaces with the appropriate solves and
values. ZEMAX even places text in the Comment column to indicate which tolerance each
surface represents. Also note the marginal ray height solve on surface 6. Remember, we
chose to have Paraxial Focus as our compensator when performing the tolerance analysis! With
this choice, ZEMAX compensates for tolerance perturbations by moving the image
surface in such a way that the perturbed system has the same amount of paraxial defocus as
the original system. Thus, the marginal ray height solve on surface 6 brings surface 7 to
paraxial focus, and the thickness of surface 7 maintains the paraxial defocus present in the
original system.
Page 3 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
With this capability, we can clearly review what ZEMAX has done to ensure any given tolerance
is performed the way we expect. Most importantly, we can thoroughly investigate any
tolerance which we find to produce curious results.
In the saved file, it is also possible to review the merit function which ZEMAX constructed to
evaluate the RMS Spot Radius criteria. The Merit Function Value is equivalent to the criteria
value reported in the tolerance output:
Page 4 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
Saving Monte Carlo Tolerance Files
Much like the SAVE tolerance control operand (which is useful for evaluating one tolerance at a
time), you may also save each individual Monte Carlo file generated during the tolerance
analysis. This option exists in the Tolerancing dialog. In the top-most portion of the dialog,
you may choose to specify how many Monte Carlo runs to perform as well as how many of
these Monte Carlo files you would like to save for viewing after the analysis is complete.
The benefits to saving the Monte Carlo files are the same to that of the SAVE tolerance control
Page 5 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
operand. However, the Monte Carlo analysis simulates the effect of all perturbations
simultaneously. Thus, the saved files will contain the modified Lens Data Editor with possibly
many changes/additions (depending upon the number of tolerance operands you have for your
system).
Saved Monte Carlo files are also saved to the directory of the nominal lens file and any number
of Monte Carlo files may be saved. The lens files are named MC_T000x.zmx, where x is the
value 1 through the maximum number of specified Monte Carlo files to be saved.
In most cases, it isn’t necessary or desirable to review each individual saved Monte Carlo file.
You may use the Monte Carlo Analysis output to help pick out any specific trial that you would
like to later review in ZEMAX format:
Page 6 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
Summary and References
When tolerancing and optical system, it is very important that you analyze and understand the
results of the tolerance analysis. Sometimes, a certain tolerance or Monte Carlo run might
produce suspicious results, requiring further in-depth analysis. The SAVE tolerance control
operand and the ability to save Monte Carlo files make this job much easier and give you full
access to what ZEMAX has done to the compute the tolerance analysis.
REFERENCES
ZEMAX Optical Design Program User's Guide, ZEMAX Development Corporation
Page 7 of 7
2011-9-15http://www.zemax.com/kb/articles/109/1/HowtoAnalyzeYour...
20
11
本文档为【ZEMAX_中如何进行公差分析】,请使用软件OFFICE或WPS软件打开。作品中的文字与图均可以修改和编辑,
图片更改请在作品中右键图片并更换,文字修改请直接点击文字进行修改,也可以新增和删除文档中的内容。
该文档来自用户分享,如有侵权行为请发邮件ishare@vip.sina.com联系网站客服,我们会及时删除。
[版权声明] 本站所有资料为用户分享产生,若发现您的权利被侵害,请联系客服邮件isharekefu@iask.cn,我们尽快处理。
本作品所展示的图片、画像、字体、音乐的版权可能需版权方额外授权,请谨慎使用。
网站提供的党政主题相关内容(国旗、国徽、党徽..)目的在于配合国家政策宣传,仅限个人学习分享使用,禁止用于任何广告和商用目的。