Authored By Akash Arora

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Introduction

In OpticStudio's Sequential Mode, rays are traced step-by-step, hitting each surface only once. In systems where light interacts with a surface or element more than once - a double pass system - the user must use additional surfaces in the Lens Data Editor to define a second pass instance. As such, the system must be wholly redefined in reverse. This is tedious at best, and prone for errors at worst. Luckily, OpticStudio has "Make Double Pass" tool that can automate this time-consuming process. 

Make Double Pass tool

The Make Double Pass tool is found in the toolbar of the LDE: Lens Data Editor...Make Double Pass.

The make double pass tool is very simple to use and only requires the user to specify the surface at which rays are to reflect. The reflect surface is converted to a mirror, all surfaces prior to it are replicated in reverse after the mirror, and pickup solves are applied to all parameters (including lens and extra data values) to link the first and second pass surface data. Note that any nominal surfaces that come after the reflect surface will be deleted when using this tool.

Open the sample file attached to this article. The file models an aplanatic laser beam delivery system with a decentered beam incident upon the optical system. Suppose the goal is to simulate a double pass system, whereby the beam reflects from the image plane and travels back through the optical components. This can easily be done with the Make Double Pass tool. Open the tool and select surface 14 as the reflect surface.

After pressing OK, notice the layout updates to show the beam coming in through the bottom of the lenses, reflecting off surface 14, and exiting through the top of the lenses. To accomplish this, OpticStudio duplicated the surfaces in reverse order and applied pickup solves. The solves make it possible to modify, optimize, or tolerance this system while maintaining the same surface definitions in the forward and reverse passes. Replicating the surfaces manually and applying pickup solves would have been a lengthy process.

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