Environmental Modeling and Athermalization in CODE V

This white paper explains how CODE V’s Multi‑Environment Coupling (MECo) streamlines environmental modeling and athermalization for optical systems that must perform across wide temperature and pressure ranges. It details why environmental effects degrade image quality, how MECo builds coupled environmental configurations directly from a nominal design, and how engineers can use Automatic Design and Glass Expert to create super‑athermalized lenses with low environmental sensitivity. The document covers supported mounting schemes, material handling, analysis tools and macros, and a practical workflow that demonstrates performance improvements (e.g., reduced defocus and stable MTF across a ~200 °C span).

Why Environmental Modeling and Athermalization Matter

Modern optical systems—spanning aerospace and defense, automotive, consumer electronics, industrial/machine vision, agriculture/environmental monitoring, and underwater imaging—face substantial environmental variability. Changes in temperature and pressure alter refractive indices, lens shapes, spacings, and housing dimensions, shifting focus and introducing aberrations. Without early consideration of these effects, imaging performance degrades in the field. The white paper motivates the need for passive athermalization—designing lenses that maintain focus and image quality as conditions change—and positions MECo as a direct, efficient solution inside CODE V.

What MECo Does

MECo leverages the nominal lens defined in CODE V and automatically creates environmentally coupled positions representing different temperatures and pressures. Because these positions coexist in a single model, designers can:

• Optimize across environments using Automatic Design, ensuring merit functions reflect multi-condition performance.
• Select materials with Glass Expert to minimize dn/dT and CTE-driven sensitivity, pursuing super‑athermalized outcomes.
• Tune housing materials and mounting approaches to manage mechanical deformations.

MECo computes thermal impacts on refractive index, element curvature, thickness, airspaces, and mount locations. Designers can assign distinct temperatures and pressures to each element, space, or housing zone, enabling realistic modeling of systems such as cryogenic dewar‑based IR cameras where optical and structural temperatures diverge.

Supported Mounting Schemes and System Types

Robust athermal design requires accurate representation of how lenses are held. MECo supports spacer‑based, seat‑based, edge‑mounted, and flange/notch contacts—as well as combinations—so users can reflect real opto‑mechanical interfaces without building a full CAD mount. Systems can be axisymmetric, folded, or zoom (multi‑configuration). Surface types include spherical, conic, rotationally symmetric asphere, Qcon/Qbfs aspheres, and Zernike (standard and fringe), covering common forms used in precision imaging designs.

Material Handling and Environmental Data

Accurate thermal modeling hinges on material properties. MECo:

• Loads catalog dn/dT and CTE data for common glasses, with straightforward entry for user-defined materials and housing alloys (e.g., custom aluminum, private glass melts).
• Uses exponential thermal expansion calculations (more accurate than purely linear assumptions).
• Provides a consolidated environmental listing (ELI) so designers can review temperatures, pressures, contact definitions, and computed mechanical changes by surface and configuration.

Analysis and Optimization Toolkit

The white paper describes macros and analyses that accelerate evaluation and optimization:

• Performance vs. temperature plots for aberration terms, RMS wavefront error, best composite focus shift, and MTF.
• Material‑data fitting tools for dn/dT and CTE models to align vendor or melt data with the design database.
• Fabrication‑temperature sensitivity analysis.
• Utilities to convert a MECo-coupled zoom to an uncoupled system for alternate workflows or downstream tasks.

Practical Workflow and Results

Using a triplet lens example spanning –80 °C to +120 °C, the paper walks through:

1. Defining independent/dependent environments (nominal manufacturing condition plus multiple dependent cases).

2. Specifying material properties (catalog data plus custom CTE/dn/dT as needed).

3. Assigning temperatures/pressures per surface or space, including different housing and element temperatures to reflect limited thermal coupling.

4. Setting housing links and contact points (spacer or seat schemes) and visualizing them in the 3D viewer to understand thermal expansions/contractions.

5. Analyzing and optimizing with Automatic Design and Glass Expert to achieve athermal performance.

Measured outcomes include significant reduction of defocus at hot/cold extremes, transverse aberrations reduced from >0.02 mm to <0.007 mm, and MTF stabilized near the diffraction-limited curve across the temperature range. These results illustrate how MECo, combined with Glass Expert material selection, lowers environmental sensitivity and maintains image quality in extreme conditions.

Applications and Use Cases

The capability benefits:

• Spaceborne optics (thermal vacuum extremes).
• Infrared systems in cryogenic dewars with differential structural/optical temperatures.
• Consumer camera modules that must endure hot/cold outdoor use.
• Automotive and surveillance optics exposed to large daily/seasonal swings.
• Underwater imaging facing pressure variations.
• Industrial machine vision demanding precision, stability, and repeatability under thermal drift.

Key Takeaways

• Topic: Environmental modeling and athermalization for optical design.
• Product/Feature: CODE V – Multi‑Environment Coupling (MECo) with Glass -Expert integration and Automatic Design.
• Value: Faster, more accurate creation of super‑athermalized lenses; realistic modeling of temperature/pressure impacts; comprehensive support for mounting schemes, materials, and system types.
• Outcome: Higher reliability and image quality across extreme environments, reduced redesign cycles, and confident performance in real‑world deployments.

Bottom line: MECo provides a seamless, end‑to‑end workflow to model, analyze, and optimize optical systems over wide environmental ranges—delivering athermalized, high‑performance lenses for demanding markets such as automotive, aerospace/defense, consumer, and industrial imaging.