MVLscope LESSON 08 / About 30 min
Find out which rays disagree.
Aberrations & Corrections
Separate focus errors from spherical, chromatic, and field-dependent aberrations, then test whether a correction addresses the cause.
Before you begin
Lenses & Image Formation · Resolution
Try a setting, save an observation, then change one thing. The explanation checks are optional.
Loading the interactive experiment… If it does not appear, reload the page. The lesson outline and model notes below remain available.
MAKE SENSE OF WHAT YOU SEE
A QUESTION TO THINK ABOUT
See the assembly in 3D Optional · all controls also work above
Optional 3D view. The calculated diagram above is the measurement reference.
YOUR EVIDENCE
Keep the comparison.
Saved images and readouts stay as they were when you captured them. Save a second setting to compare side by side.
Your notebook is empty. Use “Save this observation” beside an experiment.
Lesson outline
First test: can focus remove it?
Start with an otherwise ideal lens. The detector is displaced from the image plane, so a point makes a circular ray footprint. Refocusing can make every geometric ray meet again.
A focus error is removable by moving to the conjugate plane; a small geometric spot alone does not prove high optical resolution.
The rim and centre disagree
With spherical aberration, pupil zones do not share one best focus. Refocusing trades the error of central rays against the error of outer rays.
Refocusing can balance spherical error; it cannot remove its pupil-dependent shape.
Different colors, different focus
A lens can place different wavelengths at different axial image positions. Make one color sharp and inspect what the other two do.
A sharp single-color image does not demonstrate broadband color correction.
Check more than the centre
A flat specimen does not guarantee a flat best-focus surface. Field curvature shifts best focus with distance from the centre. Astigmatism also separates two orientation-dependent focuses.
Test centre, edge, and more than one feature orientation before calling an image well corrected.
Match the correction to the symptom
The remedy must act on the error that is present. Compare the untreated system with a selected intervention using the same pupil, wavelengths, field samples, and plotting scale.
Diagnose which rays disagree—by pupil zone, wavelength, field position, or orientation—then choose a matching intervention.
Model, limits & sources
Model: W = (D + Cq + FH²)(x² + y²) + S(x² + y²)² + AH²(x² − y²). Ray error is the gradient of W. Coordinates and coefficients are dimensionless teaching quantities; this is not a measured objective.
The pupil is a uniformly sampled disk. Geometric RMS is computed analytically, while displayed dots are deterministic equal-area samples. The plotted scale remains fixed between presets and comparisons.
The ray-intercept spots omit diffraction, coherent interference, coma, distortion, polarization, scattering, and detector response. They must not be read as intensity PSFs, resolution predictions, or Strehl ratios.
The field astigmatism term uses local radial and tangential pupil axes. The small field map rotates those axes with field direction.
Ideal correction removes one selected polynomial term. Real objective corrections are coupled, finite, wavelength dependent, and contingent on the specified optical assembly.