The Stock Lens Matching tool will swap out the lenses in a design for the nearest equivalents in the selected vendors’ catalogs, and offers the potential to make great cost savings in the finished design by eliminating the need for custom manufacture.

Authored By Mark Nicholson

Downloads

Article Attachments

Introduction

Using vendor-generated stock lenses in a design is usually more cost-effective than using custom lenses. That is why OpticStudio has the Stock Lens Matching tool, which will swap out lenses in a design for the nearest equivalents in the selected vendor catalogs.

Since most stock lenses are plano-curved or equi-curved, this tool works far better in systems with modest field angles and narrow wavelength ranges. It is also due to this reason that any asymmetric bi-curved lenses should be replaced with two plano-curved lenses when using this tool.

As is shown in this article, when the lens is swapped, the system may need to be refocused and some merit function constraints may need to be relaxed or removed - particularly ray height operands.

Stock Lens Matching example

Consider the beam expander sample file, "Beam Expander optimum solution.zmx." This file shows the design of a 5x beam expander that has approximately λ/10 wavefront error.

In the initial sample file, the design was optimized using one radius of curvature of each lens (making the lenses plano-curved) and by adding a REAY operand that targets the Marginal Ray to land at a radial height of 12.5 mm (giving a 5x magnification over the 2.5 mm radial height of the incoming Marginal Ray) and with the lens-to-lens distance fixed at 200 mm to yield a reasonably compact design. If you simply run the Stock Lens Matching tool with the design as currently set up, the performance will degrade substantially, and you will be disappointed!

Now open the file "Beam Expander Setup for Lens matching.zmx." Two changes have been made:

1. The lens-to-lens spacing (thickness of surface 3) has been made a variable so that as OpticStudio swaps the lenses out for catalog ones, it can refocus the gap to compensate the small changes of EFL:

2. The merit function constraint REAY has been modified to allow a small range of allowable magnification:

Now, run the Stock Lens Matching tool with the default settings:

OpticStudio will find the closest equivalents for each lens individually, and also find the best combination of those chosen lenses:

Since we left "Save Best Combination" selected, you will find that the optimal system was saved to the same directory as the current lens file. This optimal system is represented by the attached sample file "Beam Expander Setup for Lens Matching_SLM.zmx." Open that file, and you will see that the OPD is very slightly worse:

Note that the magnification has also changed slightly (the marginal ray height is 12.4950 mm instead of 12.5, so the magnification is 4.9980 instead of exactly 5).

This decrease in performance is expected! Assuming your starting position is well optimized, this tool will always make performance worse. This is because the design will now be constrained to using only catalog values of parameters, rather than the absolute optimum. Your starting design should therefore be well within the required specification before running the tool.

KA-01368