photoelastic op• Data kinds: image2d → polsweep
• Call: import fullseye as fs; fs.ledger.photoelastic_polarization_images(delta_rad, axis_deg=0.0, analyzers='camera4', intensity=1.0) (to call the implementation directly, import photoelastic; photoelastic.photoelastic_polarization_images(delta_rad, axis_deg=0.0, analyzers='camera4', intensity=1.0); from the registry, opsoptics.get("photoelastic_polarization_images"))
• GPU: none (CPU reference implementation only)
Images of a specimen under circularly polarised light taken by a polarisation camera (0/45/90/135 deg) or a six-intensity polarimeter → (K, H, W).
The specimen (retardance δ, fast axis θ) is lit with right-circular light S = I(1, 0, 0, 1); the emerging Stokes vector is computed with a per-pixel Mueller retarder (same convention as optics.mueller_element, whose angle is the fast axis — for a stress field pass angle_deg + 90,
see photoelastic_retardation), S' = I(1, −sin2θ sinδ, cos2θ sinδ, cosδ). Each analyser transmits ½(S0 + S1 cos2α + S2 sin2α) (linear at α) or ½(S0 ± S3) (right / left circular).
analyzers="camera4" returns the 4 frames of a division-of-focal-plane camera (0, 45, 90, 135 deg — the order optics.polarization_demosaic returns); "stokes6" adds the right- and left-circular frames. The left-circular frame equals polariscope_intensity with setup="circular_dark".
Raises ValueError: an unknown analyser set, non-2-D or non-finite inputs, a negative intensity, or |δ| beyond 200 fringes.
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.
• 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.
• 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
polsweep as input)photoelastic_phase_estimate · sfp_normals
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.