appearance op• Data kinds: signal → signal
• Call: import fullseye as fs; fs.ledger.thin_film_reflectance(nm, thickness_nm=350.0, n_film=1.33, n_sub=1.0, cos_theta=1.0, n_out=1.0) -> 'np.ndarray' (to call the implementation directly, import matappear; matappear.thin_film_reflectance(nm, thickness_nm=350.0, n_film=1.33, n_sub=1.0, cos_theta=1.0, n_out=1.0) -> 'np.ndarray'; from the registry, opsoptics.get("thin_film_reflectance"))
The spectral reflectance of a thin film (thickness d, index n_film). The closed Airy (multiple-reflection) form.
nm: wavelength [nm] (array allowed).
thickness_nm: film thickness [nm]. 200–800 for a soap bubble, 50–300 for an anodized coating. n_film/n_sub/n_out: refractive index of film / substrate / incident side (real, no absorption).
cos_theta: cos of the angle of incidence on the incident side (array allowed, in a shape broadcastable with nm).
Returns: reflectance R (0–1), in the broadcast shape of nm and cos_theta.
Physics: phase difference from propagation in the film δ = 2π·(2 n_film d cosθ_film)/λ. With the Fresnel coefficients of the interfaces (mean of s and p polarization = unpolarized) as r1, r2, R = |r1 + r2 e^{-iδ}|² / |1 + r1 r2 e^{-iδ}|². Reflection peaks at odd multiples of λ/4 (when n_film > n_sub), and the colour shifts as the thickness changes —— that is the colour of a soap bubble. At film thickness 0, R matches the Fresnel reflection of the bare substrate (verified in tests).
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.
• colorimetry — Colorimetry and spectra — colour is fixed only by spectrum × illuminant × observer
• mv_illumination_practice — Lighting in practice — wavelength, polarisation, drive modes, ambient light, safety
• 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.
• appearance_structural_colour — py -3.11 examples/appearance_structural_colour.py
signal as input)emva_photon_transfer · emva_quantum_efficiency · emva_linearity_error · emva_snr_curve · emva_dark_current · cie_xyz_from_wavelength · spectrum_to_srgb · fresnel_dielectric
appearance)cie_xyz_from_wavelength · spectrum_to_srgb · grating_wavelengths · grating_rgb · thin_film_rgb · ward_anisotropic
*Provenance: matappear.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.