alias opなし → table(引数だけで決まる op —— 画像やデータの入力を取らない)import fullseye as fs; fs.ledger.sampling_alias_distance(period_m, pitch_deg, lattice='hex', view_angle_deg=0.0, acceptance_deg=0.0, obliquity='along') (実装を直接呼ぶなら import flyvision; flyvision.sampling_alias_distance(period_m, pitch_deg, lattice='hex', view_angle_deg=0.0, acceptance_deg=0.0, obliquity='along')、台帳から引くなら opsflyvision.get("sampling_alias_distance"))The distance beyond which a periodic target aliases on a sampling lattice.
A period period_m seen from distance d at viewing angle theta has
the angular period P cos^2(theta)/d (the cos^2 is the derivative of the
line-of-sight intercept; obliquity="across" — the period runs
perpendicular to the plane of obliquity — makes it a single cos). A lattice
of pitch pitch_deg resolves angular periods down to sqrt(3) * pitch
(hexagonal: the inscribed circle of its Brillouin zone) or 2 * pitch
(square), so the target aliases once::
d > period_m * cos^2(theta) / (sqrt(3) * pitch) (hex)
d > period_m * cos^2(theta) / (2 * pitch) (square)
The same number is the working-distance rule of an inspection camera: pitch_deg is the pixel’s instantaneous field of view, period_m the pitch of the display, mesh, weave or halftone being inspected, and beyond the returned distance the picture carries a moire that is not in the part (Petersen & Middleton 1962 for the lattice Nyquist regions).
period_m: the target’s spatial period, metres.
pitch_deg: the sample spacing — inter-ommatidial angle or pixel IFOV, degrees.
lattice: one of :data:SAMPLING_LATTICES.
view_angle_deg: the obliquity of the line of sight, |theta| < 90.
acceptance_deg: the FWHM of the Gaussian acceptance (or pixel blur), degrees;
0 means a delta sampler.
obliquity: one of :data:OBLIQUITIES.
Returns a dict {"distance_m", "nyquist_cycles_per_rad", "period_floor_deg",
"mtf_at_nyquist", "lattice", "view_angle_deg"} — the alias distance, the
lattice’s Nyquist frequency, the smallest angular period it resolves, and the
acceptance’s modulation transfer at that limit (1.0 for a delta sampler).
Ground truth (pinned in the tests): a 7 cm period on a 1.1-degree hexagonal eye aliases beyond 2.105 m head-on and 0.526 m at 60 degrees; on a 4.63-degree eye beyond 0.500 m and 0.125 m; with a 1-degree acceptance the hexagonal 1.1-degree eye keeps 0.375 of the contrast at Nyquist, the 8.23-degree acceptance of a 4.63-degree eye keeps 0.024.
Raises ValueError: a non-positive period_m / pitch_deg (an empty
period_m is refused as not a number), a negative acceptance_deg, a
view_angle_deg at or beyond 90, and an unknown lattice / obliquity.
py -3.11 examples/poc_zebra_stripes_fly_eye.pytable を入力に取れる)fly_t4t5_field · fly_flow_from_directions · fly_matched_filter · fly_egomotion_from_flow · fly_eye_merge · fly_view_plane_texture · fly_hex_resample · fly_expansion_readout
alias)Provenance: flyvision.py — FLYVISION operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.