Validation

Optiland’s own test suite shows that Optiland agrees with itself over time. It cannot show that the physics is right. The only way to show that is to trace the same system in independently developed, widely used tools and compare numbers.

This page reports that comparison. Four reference systems were traced in Zemax OpticStudio and CODE V and compared with Optiland, quantity by quantity.

Summary

On all four systems, first-order properties, third-order (Seidel) aberrations and real-ray intercepts agree with both OpticStudio and CODE V, to the last printed digit in most cases and to better than 1 × 10^-6 mm on real-ray intercepts. Image-quality metrics (spot size, wavefront error, MTF) have been compared in more limited form and agree within the stated tolerances, with a few open items listed below.

Note

This is a comparison on four systems, not a certification. It does not cover every surface type, material model or analysis in Optiland. The scope section says exactly what has and has not been checked.

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At a glance

System	OpticStudio	CODE V	What it exercises
Singlet, stop on rear surface	Tier 1 agrees	Tier 1 agrees	Real-ray and first-order correctness on a strongly aberrated lens
Cooke triplet	Tier 1 and Tier 2 agree	Tier 1 agrees (see glass note)	Interior stop, three-element design, glass catalog handling
Double Gauss, F/5	Tier 1 agrees	Tier 1 agrees	Aperture defined by image-space F/#, cemented doublets, pupil solving
Hubble Space Telescope	Tier 1 agrees, Tier 2 mostly (one open item)	Tier 1 agrees	Mirrors, conics, negative thicknesses, central obscuration, curved image

Tier 1 is first-order properties, Seidel sums and single real-ray intercepts. Tier 2 is spot radii, wavefront error, distortion, field curvature, Zernike coefficients and MTF.

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What was compared

First order

Effective focal length, entrance and exit pupil size and position, image-space F/#, back focal point, principal plane, Lagrange invariant.

Third-order aberrations

Seidel sums S1 to S5 plus longitudinal axial and lateral color.

Real rays

Six individual rays per system (on axis, full field, 70 % field, several pupil positions): image-plane position and direction cosines.

Agreement criteria

Quantity	Counted as agreement when
First-order properties	Within 1 × 10-4 relative
Real-ray intercepts	Within 1 × 10-6 mm
Seidel sums	Within 1 %, ignoring the overall sign convention
Spot radii	Within 1 %
RMS wavefront error	Within 1 % or 0.01 waves, whichever is larger
MTF	Within 0.01 absolute

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Results

Tool versions: OpticStudio 2023 R1.02, 2025 R2.02 and 2026 R1.00 (depending on the system) and CODE V 2025.03.

Real rays

Real-ray intercepts are the most demanding test, because small errors in surface intersection, refraction or reflection show up directly.

System	OpticStudio	CODE V
Singlet	Agrees to every printed digit	Agrees to every printed digit
Cooke triplet	Agrees to every printed digit (< 1 × 10-6 mm)	Up to 2.3 × 10-5 mm, entirely from a glass substitution; agrees to 5 × 10-7 mm with the exact glass data
Double Gauss	Within 5 × 10-10 mm	Within 5 × 10-7 mm
Hubble	Within 5 × 10-9 mm	Within 1 × 10-8 mm

First-order properties

Effective focal length, as an example of the first-order comparison:

System	Optiland	OpticStudio	CODE V
Singlet	101.501826	101.501826	101.501826
Cooke triplet	49.999783	49.999783	49.999598 [1]
Double Gauss	100.003748	100.003748	100.003748
Hubble	57600.080998	57600.079948 [2]	57600.080998

All other first-order quantities follow the same pattern; the full tables are in the discussion linked below.

Seidel aberrations

Magnitudes agree on every system with both tools. Two conventions to know:

• OpticStudio reports S1 to S5 and lateral color with the opposite sign to Optiland. This is an overall sign-convention difference, not a disagreement. CODE V’s signs match Optiland’s.

• Use the plain Seidel Aberration Coefficients listing in OpticStudio, not the separate in Waves listing, which is a different normalization and differs by roughly a factor of 200.

Image quality (Tier 2)

Compared with OpticStudio on the Cooke triplet and, in part, Hubble. Spot radii agree within 1 % (largest deviation 0.77 %), RMS wavefront error within 1 % (largest 0.13 %), and distortion and sagittal field curvature to the printed digits. Zernike coefficients (Fringe, 37 terms) agree to about 1 × 10^-5 waves. CODE V Tier 2 results are still to come.

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Open items

These are known, tracked, and not hidden. None affects the Tier 1 results above.

Item	Status
Hubble tangential field-curvature shift differs by 0.6 % from OpticStudio (sagittal agrees to 2 × 10-8)	Unexplained. Checked against sampling and finite-difference step
Double Gauss polychromatic on-axis MTF: gap grows with spatial frequency (about +0.01 at 20 cycles/mm to -0.05 at 50 cycles/mm)	Unresolved. Does not shrink with finer sampling. Suspected pupil-extent or apodization convention
Cooke triplet FFT MTF: one low-contrast point (Hy = 1.0, 40 lp/mm, tangential)	A sampling effect: converges to OpticStudio as Optiland’s pupil sampling increases
Double Gauss Tier 2 (wavefront, Zernike, MTF) not yet compared against any tool	Awaiting contributions
CODE V Tier 2 not yet reported	Awaiting contributions

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Scope and limits

Covered: sequential ray tracing of spherical, conic and mirror systems; paraxial properties; Seidel aberrations; real-ray intercepts; spot, wavefront, distortion, field curvature, Zernike and FFT MTF on the systems noted above.

Not covered: aspheric and freeform surfaces, gradient-index media, diffractive surfaces, tilted and decentered systems, polarization and coatings, non-sequential tracing, tolerancing and optimization. Absence from this page means not yet compared, not known to differ.

Single reporter per tool. Each tool and version was run by one person. The numbers are most useful when someone else with the same tool reproduces them. Anyone with OpticStudio, CODE V or another tool is invited to contribute.

Glass data. Optiland resolves glasses from refractiveindex.info. The Cooke triplet uses Hikari SK16, which CODE V’s catalog does not carry. The closest CODE V glass shifts EFL by 4 parts per million, and every Cooke residual in CODE V follows from that. With a private glass carrying Optiland’s exact indices, CODE V reproduces Optiland’s EFL, back focal point, color and rays.

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Reproduce it, or add your own

• Full tables, prescriptions and tool settings: GitHub issue #710. It also has ready-to-open .zmx files, and the template for reporting your own comparison.

• Optiland side: the four systems ship with Optiland.

  from optiland.samples.simple import SingletStopSurf2
  from optiland.samples.objectives import CookeTriplet, DoubleGauss
  from optiland.samples.telescopes import HubbleTelescope
  

• Regression test: the OpticStudio Hubble reference values are encoded in tests/test_cross_tool_validation.py and run with the test suite, so a change that breaks agreement is caught.

Notes

[1]

CODE V has no Hikari SK16 and the closest catalog glass was used; with Optiland’s exact SK16 indices CODE V gives 49.999783.

[2]

This value matches Optiland run on a .zmx written with 9-significant-digit curvatures (the writer before #712), and CODE V reproduces it from that same 9-digit lens. It is expected to match 57600.080998 when re-measured on the current file; that re-measurement is pending.