This article describes how to use “Equation Driven Import” option in OpticsBuilder to expose the OpticStudio equations and import with surfaces created directly from the equations.

**Authored By Mojtaba Falahati**

## Downloads

All the examples and features are showcased with Creo Parametric 7 and are given installation default settings, all sample files can be found in the following directory:

..\Documents\Zemax\Samples\OpticsBuilderCreo

## Introduction

Zemax OpticsBuilder helps CAD users directly convert complete optical designs from Zemax OpticStudio into a CAD Environment, analyze the influence of the mechanical components on the optical performance and export optical drawings to manufacturing. The ability to save the parts into PDM systems now includes the option to recall the equations used to generate the surfaces. In the Zemax OpticsBuilder 22.3 / Ansys Zemax OpticsBuilder 2022 R2.02 release and later, users have the choice to expose the OpticStudio equations and import into OpticsBuilder with surfaces created directly from the equations.

## Equation-Driven Import

Legacy import of optical geometries into OpticsBuilder uses splines/NURBS sampling based on the equations provided by OpticStudio which offers speed and accuracy high enough for most applications. The new option allows for more accurate surface representation using the exposed equations to create parts and makes it possible to be integrated into the part file. This feature helps those users who need to design complex mechanical mounting edges with higher accuracies. If you wish to expose the OpticStudio equations and import with surfaces created directly from the equations, you may choose the “Equation Driven Import” option under “Preferences” before you import the .ZBD file. Please note that Equation-driven import is only available for Standard, Even Asphere, Odd Asphere, Binary 2 and Off-Axis Mirror object types.

The equations used to describe the surfaces are the same used in OpticStudio. See the definition of the equations below:

1. Standard Lens

2. Even Aspheric

3. Odd Aspheric

4. Binary2

Gratings are not modelled in the geometry since OpticStudio does not model the wavelength-scale grooves directly. Instead, OpticStudio uses the phase advance or delay represented by the surface locally to change the direction of propagation of the ray. So, the geometry will be same as standard lens.

5. Off-Axis mirror

For the base surface we use standard surface equation

And for the cutting angle calculations we use the equation below.

where Y_{0} is off axis offset, k is conic constant, c is curvature of the surface and H is half-width of the object. H is used to decide the height and width of cut. Also, both circle and rectangle shapes are covered.

OpticsBuilder can create an equation driven off-axis mirror provided that above mentioned condition is satisfied, in cases where the condition is not satisfied it will represent it as an imported STEP file if one is available from OpticStudio.

## Equation-Driven Import of the Flash Lidar Model

To showcase this feature, we use the Flash Lidar sample file which can be found in the Zemax Samples folder, located at {Zemax}\Samples\ OpticsBuilderCreo\ FlashLidar\ FlashLidar_FullSystem_Start.zbd. The Flash Lidar optics includes several aspheric elements.

First open Creo Parametric and select the “Equation Driven Import” checkbox in OpticsBuilder…Preferences:

Now click "Import ZBD File", navigate to the Flash Lidar ZBD file and open it as shown below:

Parameters of the parts (optical components) can be exposed using two different approaches, whether imported in standard mode or with equation driven surfaces.

1- Through the Creo Parametric Tools tab: Click "Parameters" in the Tools tab and select "Part" from the drop-down menu in the Parameters prompt. Now you can select the part of interest from the Model Tree and view the surfaces parameters.

2- Through the OpticsBuilder tab: In OB Input Tree right-click on the component of interest and select "Edit Optical Properties" ("View Optical Properties" if the ZBD file is Read-only). The surfaces parameters can be viewed in the Lens tab of the optical properties window.

Since we imported the ZBD file with "Equation Driven Import" selected we can expose the main curves equation for the surfaces. To do so, in Model Tree open the part menu, click on the FRONTCURVE or BACKCURVE and click "Edit Definition".

Now click "Equation" button from the "CURVE: From Equation" tab to see the equation definition.

Here, you can edit the curve parameters as well. But note that changes to the equation may break the link back to OpticStudio resulting in STEP file export from OpticsBuilder. So, we recommend, if you need to change the equation, that you do it in OpticStudio and then Update the .ZBD file in OpticsBuilder.

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