How to use the Stock Lens Matching tool

Updated: 2024-Feb-16

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

Updated by Yihua Hsiao

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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.

Layout_5-beam expander

OPD_Fan

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:

Lens_data_thickness

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

Merit_function_REAY

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

Stock_lens_matching

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

Text_viewer

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:

OPD_Fan_2

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.

 

New capabilities

Starting from Ansys OpticStudio 2023 R2.01, The Stock Lens Matching tool not only filters out suitable lenses based on the original criteria of EFL and EPD but also introduces support for two new options: Match Shape and Match Orientation.

 

Regarding Match Shape, we first define the shape factor using the following equation.

,where C is the curvature of the lens face.

If the Match Shape is checked, it means that within the Stock Lens, any lens with a shape factor difference within a certain range from the originally designed lens will be filtered out. If it is not checked, it indicates that the filtering criteria do not consider the proximity of the shape factor.

Regarding Match Orientation, if checked, the Stock Lens with different positive and negative signs of the shape factor will be reversed, while those with the same sign will retain their original orientation. The comparison of Merit function values will then take place. If unchecked, the Merit function values will be compared for each Stock Lens in both directions.

For instance, consider the following six stock lenses in the picture below, and in our current design scenario, assuming we have a lens system with S>0. If the "Match Orientation" button is checked: Lenses A, B, and C will be flipped, resulting in reversed-A, reversed-B, and reversed-C, respectively. Additionally, lenses D, E, and F will remain unchanged. Consequently, a total of 6 lenses (rev-A, rev-B, rev-C, D, E, F) will be compared based on their Merit Function values. If the "Match Orientation" button is unchecked: Lenses A, B, C, D, E, and F will retain their original orientation, while their reversed counterparts will also be considered. This yields a total of 12 lenses (A, B, C, D, E, F, rev-A, rev-B, rev-C, rev-D, rev-E, rev-F) for comparison in terms of their Merit Function values.

Therefore, these two functionalities collectively result in four possible scenarios, each outlined as follows:

  • When Match Shape is CHECKED & Match Orientation is CHECKED: Filters for EFL, EPD, and Shape factor, then assesses matching orientation and finally compares the merit function and ranking. (This functionality remains the same as before 23 R2.01).
  • When Match Shape is CHECKED & Match Orientation is UNCHECKED: Filters for EFL, EPD, and Shape factor, then test both orientations and finally compare the merit function and ranking.
  • When Match Shape is UNCHECKED & Match Orientation is UNCHECKED: Filters for EFL and EPD only, then tests all shapes with both orientations and finally compares the merit function and ranking.
  • When Match Shape is UNCHECKED & Match Orientation is CHECKED: Filters for EFL and EPD only, then assesses matching orientation and finally compares the merit function and ranking.

In the final report, if any of the utilized Stock lenses have been flipped in orientation, a notation will be made above the Orientation column indicating "Reverse".

 

Therefore, the implementation of this new functionality provides users with greater flexibility in selecting how to utilize Stock lenses. This enhanced flexibility can assist users in identifying lenses that align with their desired optical system designs, thereby facilitating the optimization of optical systems to meet specific requirements and objectives.

 

 

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