photoelastic op• Data kinds: images → table
• Call: import fullseye as fs; fs.ledger.retardation_unwrap_multiwavelength(deltas_rad, wavelengths_nm, max_retardation_nm, folded=True) (to call the implementation directly, import photoelastic; photoelastic.retardation_unwrap_multiwavelength(deltas_rad, wavelengths_nm, max_retardation_nm, folded=True); from the registry, opsoptics.get("retardation_unwrap_multiwavelength"))
• GPU: yes (mechanical GPU path from the allow-list, CuPy). device="auto" chooses the GPU from the measured size (4,194,304 pixels) up
Absolute retardation (nm) from wrapped retardations at several wavelengths (assuming no dispersion) → dict.
The retardation R = t·Δn [nm] is assumed independent of wavelength (no dispersion of C). For each pixel, every candidate from the first wavelength, R = (k + f)λ1 (and (k + 1 − f)λ1 when folded, f = δ1/2π), up to max_retardation_nm, is scored by how well it predicts the measured phase at every other wavelength (residual in nm); the best candidate wins.
folded=True is for phases in [0, π] that cannot tell δ from 2π − δ (photoelastic_phase_estimate with stokes6); folded=False is for phases wrapped into [0, 2π).
Returns retardation_nm, delta_rad (the unwrapped phase at the first wavelength), residual_nm (best score), margin_nm (second best − best, among candidates more than λ_min/4 away from the answer: when it is small another order fits almost as well — add a wavelength or reduce max_retardation_nm) and valid: False where no candidate up to max_retardation_nm exists for that pixel (its first-wavelength phase alone already needs more), and the four numbers are NaN there.
Raises ValueError: fewer than 2 wavelengths, mismatched counts or shapes, wavelengths outside [10, 20000] nm or repeated, phases outside [0, π] (folded) / [0, 2π) (unfolded), a range over 1000 waves, or a max_retardation_nm below the smallest candidate of every pixel.
Every optics op validates its input before computing (nothing slips through silently):
• Units are baked into the argument name — _mm / _um / _deg / _mrad. Confusing mm with µm does not crash; it yields a plausible-looking wrong answer, so the name prevents it. Nothing here guesses the unit from the magnitude.
• Strings raise ValueError — float('50') succeeds, so an unparsed configuration value would slip through as a length (measured: thin_lens('50', '200') returned a plausible 66.667 mm). bool is refused too, as the implicit promotion True == 1.
• complex / masked arrays raise ValueError (real-valued slots only; silently dropping the imaginary part or peeling off the mask is refused). NaN/Inf raises ValueError on every input. Exception, declared: the u_map of bottle_fit_from_pattern takes pixels that could not be measured as NaN (infinity is still refused).
• Division by zero and its relatives are refused by name: focal length 0, radius of curvature 0, refractive index <= 0, a fully opaque aperture (all zeros, so the normalisation is 0/0), a PSF whose sum is <= 0, a Stokes vector with S0 = 0, and an object sitting at the front focal point (the image is at infinity).
• Only two ops return a non-finite value, and both state it as a contract: depth_of_field returns far_mm = inf beyond the hyperfocal distance (that is what the hyperfocal distance means), and gaussian_beam returns wavefront_radius_mm = inf at the waist (the radius of curvature of a plane wavefront). Both also return a finite companion (far_is_infinite / curvature_per_mm). Any other silent NaN/Inf is detected internally and raises ValueError — "float64 overflowed" and "the answer is infinite" are different claims, so the first is never returned wearing the face of the second. Exception, declared: bottle_background_map returns NaN in u_mm for pixels whose ray is unusable (total internal reflection and the like), together with a valid mask and the counts.
• Size caps: generated grids are capped by optics.MAX_GRID (4096); supplied fields/PSFs/apertures by optics.MAX_FIELD_ELEMENTS (2^24); ABCD element chains by optics.MAX_SYSTEM_ELEMENTS (1024); Zernike by MAX_ZERNIKE_TERMS (512) / MAX_ZERNIKE_ORDER (40) / MAX_ZERNIKE_BASIS (2^25). This closes, fail-closed, the paths where a small argument triggers a huge internal allocation (measured: n_max=40 × 4096² needs 108 GB).
• Physically impossible states are refused too: a Stokes vector with degree of polarisation > 1, negative transmittance, negative intensity, and invalid Zernike indices such as n-|m| odd.
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
• photoelastic_roundtrip — py -3.11 examples/photoelastic_roundtrip.py
table as input)abcd_matrix · wavefront_stats · sfr_from_edge · paraxial_trace · seidel_coefficients · spot_stats · tolerance_analysis · wavefront_from_opd
photoelastic)brazilian_disc_stress · kirsch_plate_stress · principal_stress · retardation_from_birefringence · photoelastic_retardation · retardation_convert · cubic_photoelastic_birefringence · silicon_piezo_optic_coefficients
*Provenance: photoelastic.py — OPTICS operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.