SurfCalc › Optomechanical Software

What is optomechanical software?

Optomechanical software is the missing middle of a structural-thermal-optical performance (STOP) workflow: the layer that turns what a structural analysis predicts about a deforming mirror or bench into something an optical engineer can actually judge a design by.

The gap it fills

Two mature toolchains sit on either side of an optomechanical problem, and neither one crosses the gap by itself.

On one side is structural and thermal finite element analysis — Abaqus, Ansys, Nastran. It predicts, accurately, how a mount, a mirror, or an instrument bench moves and distorts under gravity, thermal soak, launch loads, or wind. Its output is displacement and stress.

On the other side is optical design software such as Zemax OpticStudio or CODE V. It traces rays through an optical prescription and reports image quality. Its input is an optical surface, not a finite element mesh.

Optomechanical software performs the conversion between them. It maps FEA nodes onto the optical surface, removes the rigid body motion (RBM) that a mount takes up rather than the optics, fits the residual shape to an appropriate polynomial basis, and reports the result as surface error and wavefront error — quantities an instrument or telescope designer can hold against a budget.

Why teams outgrow scripted workflows

Most groups build this pipeline themselves the first time they need it: export coordinates from the FEA solver to CSV, hand-write Matlab or Python for rigid-body-motion subtraction and Zernike fitting, then stitch together custom reporting. It works, and for a single study it is often the right call.

It scales badly. The chain breaks on solver updates, coordinate and unit conventions get re-derived from scratch on each project, and the scripts rarely survive the engineer who wrote them. Dedicated optomechanical software exists because that conversion is the same conversion every time — worth solving once, properly, rather than rebuilding per project.

What to look for in optomechanical software

• Native solver import. It should read Abaqus .odb, Ansys .rst, and Nastran .op2 directly, read-only, without a manual CSV export step in the middle.
• Correct rigid body motion handling. Tilt and decenter that a mount absorbs must be separated from the figure error that actually degrades the wavefront.
• The right polynomial bases. Circular Zernike is not enough on its own — obscured apertures need annular Zernike, rectangular optics need Chebyshev, and segmented primaries need a hexagonal basis.
• Output the optical side accepts. Zernike coefficient sets, grid sag files, and interferogram files that go straight into an optical design package.
• Active optics, if the system has actuators. Building an influence matrix from poke-test results and solving for correction forces under real stroke and force limits is a distinct problem from fitting a surface.
• A scripting path. A workflow built once interactively should be automatable afterwards without being rewritten.

Where SurfCalc fits

SurfCalc is optomechanical analysis software that turns structural FEA results into optical surface and wavefront performance data. It is not a ray tracer and does not replace an optical design package — it produces the surface data, grid sags, and interferograms those packages consume. It runs as a standalone Windows desktop application and as a headless CLI, with a matching scripting API, so an analysis set up interactively can be automated later.

Its modules are organised by the role they play in a STOP workflow:

1. Prepare
   Produce a field or basis to fit or correct against.
   • Load Case Combination — combines several FEA load cases (gravity, thermal, wind) into one deformation field.
   • Influence Matrix — compiles per-actuator FEA poke-test results into a coupled influence matrix.
   • Bending Modes — extracts a normal-modes basis from an FEA modal analysis or a hand-built CSV.
   • Sensitivity Matrix — computes a rigid-body to line-of-sight sensitivity matrix from an optical prescription.
2. Solve
   Turn a prepared field into an answer.
   • Surface Deformation — decomposes surface displacement maps into Zernike coefficients and subtracts rigid body motion.
   • Active Optics — solves for optimized actuator correction forces under stroke and force limits.
   • Image Motion — combines per-surface deformation with a sensitivity matrix into a line-of-sight error budget.
   • Random Response Budget — turns an FEA random-vibration result into a 1-sigma Zernike budget.
3. Analyze
   Consume results that have already been solved.
   • Result Comparison — stacks two or more computed results side by side with a numeric PV/RMS metrics strip.

Common questions

Is optomechanical software the same as optical design software?

No. Optical design software traces rays through an optical prescription. Optomechanical software works one step earlier, converting deformed FEA geometry into the surface and wavefront quantities an optical design package can consume. The two are complementary — a STOP analysis normally uses both.

Do I need it if I already have FEA?

FEA gives you displacement and stress; it does not tell you the optical consequence of that displacement. Getting from one to the other is the conversion described above, and it is the part teams without dedicated software end up hand-writing.

What should it be able to read and write?

At minimum the native result formats of the solvers actually in use, and on the output side the formats optical design packages accept. See the User Guide for SurfCalc's full import and export list, or the API Reference for the scripting and headless paths.

Try it on your own model

SurfCalc runs on Windows as a desktop application and as a headless CLI. Trial keys are issued after contact.

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