This is the first of a series of posts on the lens design process we utilize at Optica for all of our lens designs. This process has been shown to achieve the necessary design performance while ensuring that the as-built performance will also be maximized.
We will be presenting the basics of this process with a Zemax example that will show how the process works. For brevity we will not include all of the design theory or time consuming processes. This is meant to be a tutorial for the inexperienced lens designer who is interested in learning how to design lenses with Zemax.
Lens Design Process:
Lens Specification
Selection of starting point (either from scratch or a previous similar design)
Optimization
Design for manufacturing
Tolerance sensitivity analysis
Stray light analysis
Mechanical design
Tolerance stack up
Optical and mechanical drawings
First the lens specification is reviewed and modified if needed and agreed upon with the customer.
Next, the lens designer either starts the design by selecting a previous design that is similar as a starting point, or starts the lens design from scratch.
Once the starting point is found the merit function is written to reflect the desired specifications and the optimization is started. During the optimization process the lens designer can move, add or subtract elements in the design to increase performance. The optimization process is complete once the desired performance targets are achieved or the customer agrees to loosen a target that is proving to be difficult.
The fourth step is to make the lens ready for manufacturing by desensitizing it to the parameters that will result in the greatest loss of performance.
Step 5 is closely tied with step 4 in that the lens designer needs to know which tolerances will be most sensitive to try to make them less sensitive, so an iterative approach to steps 4 and 5 is sometimes needed.
Steps 6 and 7 can be done in concert since the stray light analysis depends on the geometry of the mechanics and the mechanics will be modified to block as much stray light as possible.
Once the mechanics are designed, the tolerance stack up can be analyzed to determine what the tolerances on each feature of each optical or mechanical component need to be to deliver acceptable performance.
Lastly, optical and mechanical part drawings need to be made that accurately reflect the necessary features, dimensions and tolerances that were determined previously.
At this point the optical and mechanical components are ready to go into manufacturing and if made to specification will result in an assembly that performs as expected.
In our next post in this series we will discuss Step 1: Lens Specification in more detail.
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