Tolerance Analysis in reTORT
Tolerance Analysis is essential to any optical design to be manufactured. It’s a set of techniques that must exist in every designer’s workflow. It’s up there right after a great global optimizer.
In reTORT, easy access to optimization wizards, tolerancing wizards and our informative status bar gives the optical designer complete command over their workflow. All design parameters are in easy reach as is every step of the design analysis. Modify your design on the fly. Then, restart your analysis, all from one single reTORT screen.
After reading this intro, download the latest version of the Tolerance Analysis User Manual. Now, here’s a brief introduction.
Starting the Tolerance Wizard
It’s easy-peasy. As below, start the tolerancing wizard and an Auto Tolerance Analysis object will automatically be generated.
The Tolerance Wizard Explained
The wizard has two main sections, parameters and settings.
In the first, select which parameters to include in the tolerance analysis. Then, choose which parameters reTORT should use as compensators. Compensators are parameters that are allowed to change during the tolerance analysis, maintaining an optimized solution as close to the original as possible.
This shows the tolerancing wizard parameters with various tolerances and a compensated working distance.
Settings is the main control panel for your tolerance analysis. You can run more than one type of analysis in parallel. You also set whether to use compensators or not. And you can easily pause or stop the analysis at any point.
Running a Tolerance Analysis and Viewing Results
With the wizard open, simply click Run. You can also right-click the tolerance analysis object and select Run:
The status block will be an important resource for you as the tolerance analysis runs.
Any error will appear in red. Notice that direct sensitivity and monte carlo are running at the same time. The status bar provides you with real-time feedback.
The progress bar also provides feedback on how your tolernace analysis is progressing.
To view the results, right click on the type of result you wish to view. Below we want to view a table.
and something like the following would be immediately available to you.
But don’t forget plotting tolerance analysis results
Or you can choose to output a variety of plots.
Get more details and tips to using the reTORT ray tracer tolerance analysis by downloading the user manual.
reTORT and its Global Optimizer
It’s a slightly different workflow but, it works well.
Recently, we ran a focus group about optimizers with a group of our Customers. Through this, we found that many did not use global optimization, at least not until the very end of their design project.
But why? These designers told us that some of the ray tracers they have used took hours or days to run Global Optimization. And then, they returned one hundred or more possible solutions. After that, the designer needed to sift through the solutions to find one or more they wanted to further refine.
That’s a huge time commitment. After all, your time is money. And, it can significantly stall progress on a lens design. But, that’s the way some ray tracers implement Global Optimization.
reTORT is an exception to this rule. In fact, Global Optimization in reTORT is extremely useful and will speed up your workflow.
reTORT‘s global optimizer returns one optimum result within your design constraints. On average, for a typical complex lens, it does this within a few minutes.
This feature allows comparison of alternative designs more quickly.
How reTORT and its optimizer work
In reTORT, optimization wizards allow easy setup and running of global or local optimization. You can run a global or a local optimization from this one window.
reTORT employs evolutionary algorithms for its global optimizers. Specifically, they are based on a modified version of CMAES, or Covariance Matrix Adaptation Evolution Strategy. The E x H modifications to CMAES provide for speedy and accurate results.
Note the wizard provides easy access to the lens system parameters. This example is a gradient index lens employing binary mixtures to achieve the design objectives.
The CMAES global optimizer is capable of optimizing over a very large search space with many variables. CMAES can easily generate new candidate lens designs from scratch with minimal oversight.
E x H found through its research that CMAES is much more efficient if you apply bounds. This may defy logic for some. For us, it has proven to work very well in our own designs.
You might ask, do bounds mean over-constraint? Not at all. All designs have some over-riding design objectives. These provide the basis for applying realistic bounds.
We hope to start bragging about our very useful status bar. You can see it below in an illustration of a global optimization. The status bar shows that 12,000 simulations were run and two can be seen taking from 65 to 85 milliseconds each.
The entire optimization took a total of 3.37 minutes.
Bounded versus Unbounded Optimizer
Please remember, reTORT also offers a very efficient local optimizer based on the Damped Least-Squares (DLS) algorithm. DLS is run unbounded by default. This is in contrast to its global sister.
In our research, we found that bounded DLS algorithms tended to more easily fall into near optimums. In other words, they often take one of the first valleys they find. This is even though a better solution was available in the search space. It acted like one of our favorite little guys searching for an optimum below:
And so, reTORT’s DLS is unbounded based on our preferred workflow of first using bounded global optimization. Global optimization with CMAES is used to find a candidate design within mere minutes. Then, we use local optimization to test variations of that design and tune it even further. In that way, we can hone the design in less time. And with reTORT each iteration is faster than other tools.
But that is just our preferred workflow here at E x H. reTORT allows you to employ the workflow that you prefer. It does not lock you into one workflow or another. Instead, reTORT is extremely flexible.
The choice is always yours. A variety of Workflows are feasible due to the way global and local optimizers are deployed in reTORT. Even our optimization wizard allows quick and easy control of both from the same window.
But There’s More
You can easily have global and local optimizers configured at the same time. But they don’t necessarily run at the same time. You can switch from one to the other as you prefer. You can see this in the Optimizer Settings image above. Both methods are enabled at the same time.
If one of the three workflows above does not suit you, reTORT’s optimization wizard allow you to easily design your own workflow.
Even better, the wizard allows you to follow your creative instincts.
The reTORT wizards also give you immediate control over optimization settings, goals, and parameters. As you proceed with your design, your optimizer controls are right at hand for making quick tweaks.
You can also save multiple optimization configurations. The optimization wizard creates optimizations under the names “AutoCMAES” and “AutoDLS”. Save your optimizations by simply renaming them before running the wizard again. If you wish, come back later to revisit a prior configuration.
And the same power of our optimizers is equally available to you for including gradient index lenses and metasurfaces in your optical lens system design. You are able to use the full power of reTORT using the most powerful and advanced lens features available to any designer today.
The reTORT Ray Tracer is truly a unique state-of-the-art tool for today’s optical lens designer.
Get Your Copy of v2.5.0 of the reTORT Ray Tracer
Current licensees – please use this link to update!
New Users – this download comes with a free trial license you can activate!
Please visit the site to download the most current version of reTORT at any time and update the version you are currently running.
For those who are not yet using our reTORT Ray Tracer, the same download link will provide you with a free two-week trial. Our license pricing and ordering list is the place to go to order.
You will be committing to the most technologically advanced ray tracer available today.
Coming in Future Posts
More on asymmetric aspheres. Look for a new release shortly.
About E x H, Inc.
E x H’s mission is to provide you with advanced optical system simulation tools. The result is tools that allow you to design optical systems that are smaller, lighter and faster. Watch our SWaP reduction use case tutorial for a taste of this.
Some of our solvers are licensed from Penn State University. PSU is one of the leading research institutions in the USA.
We have participated on multiple programs funded by DARPA that have allowed us to develop software on the leading edge of technology.
Outside of the optical space, this same reTORT Ray Tracer was used to fast prototype the transformational optics that proved the concept for Isotropic Systems’ high throughput, multi-beam satellite terminals (https://www.isotropicsystems.com/).
On the business side, we have been backed by Gran Sasso Ventures, the same venture capitalists that funded collaboration software firm Compoze Software, now a part of Oracle [ORCL:NYSE], and multitouch technology inventor FingerWorks, the driver of touch screen technology and now a part of Apple [AAPL:NASDAQ]. E x H is at the forefront of transformation optics.For
