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Stray Light Analysis Overview

Stray light analysis is the analysis of unwanted light. Stray light is usually due to a bright source in the scene. Identification of the root causes of stray light early in the process is important to be able to reduce it during the design phase of the system before any prototype. There could be several root causes of stray light: ghost reflection on optical components, scattering reflection on mechanical components, reflection on imager, light leakage, … 


Applications: Camera, Telescope, Head-Up Display, AR/VR…


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Step 1: Optical Design

In this step, the engineer designs the optical system to optimize the performance of the system based on the specifications. 


Ansys Zemax OpticStudio is recommended for this step.


The following articles describe examples:

Step 2: Ghost mitigation and optimization of optical system

In this step, the engineer optimizes the optical system to reduce energy of stray light paths due to ghost reflections and keep good performance of the main light path considering all the optical components. 


Ansys Zemax OpticStudio is recommended for this step.


An initial analysis can be done in sequential mode to estimate which double bounce could add stray light in the image pupil plane, optimization of the optical system (shape and optical property) can be done considering reducing potential stray light. Then a more advanced analysis can be done in non-sequential mode to analyze all the different potential stray light paths in the optical system and optimize the optical system (coatings) to reduce impact of stray light paths. 


Functionalities like Ghost Generator and Sequence Selector can be used during this step. (see Ansys Learning Hub courses for more details about those features).


The following articles describe examples:

Between step 2 and step 3, the data can be transferred from Ansys Zemax OpticStudio to Ansys Speos using Optical Design Exchange (*.odx). 

 

Step 3: Visualization analysis of the full system

 

In this step, the engineer analyzes the performance of the full system including optical components and mechanical components. He identifies the root causes of the stray light paths. He optimizes the mechanical components (shape and optical property) to reduce stray light paths. In addition, the engineer can analyze the final image quality of the full system including flare.


Ansys Speos is recommended for this step.


The following articles describe examples:

This article provides optical and stray light engineers with custom Speos/SpaceClaim scripts designed to automate critical steps in the Stray Light Analysis workflow.

Functionalities like Geometry Update, Sequence Detection tool, Layer by Sequence, Light Expert, Physical Camera can be used during this step (see Ansys Learning Hub courses for more details about those features).

 

Going further: 

Those steps can be automated to facilitate the iterations and optimize the optical components and the mechanical components considering stray light paths.

The article presents a Python based workflow that bridges Ansys Zemax OpticStudio (AZOS) and Ansys Speos via Optical Design Exchange (ODX). The goal is to automate stray light detection, iteratively apply coatings to both optical and mechanical surfaces, and optimize system signal-to-noise ratio (SNR)

Step 4: Visualization analysis in a 3D scene


In this step, the engineer analyzes the final image quality of the full scene in a 3D scene under different lighting conditions.


Ansys Speos is recommended for this step.


The following articles describe examples:

  • Stray Light Analysis in a 3D scene (upcoming article)
     

Learning Paths (per application)

 

You can find below some learning paths based on application: 


Camera Learning Path: 

Telescope Learning Path: 


Additional Resources


Relevant Zemax Ansys Learning Hub courses:


Relevant Speos Ansys Learning Hub courses:

 

Associated files

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