alias op• 資料種類:無 → table(僅由參數決定的運算子 —— 不接受影像或資料輸入)
• 呼叫: 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')(要直接呼叫實作,import flyvision; flyvision.sampling_alias_distance(period_m, pitch_deg, lattice='hex', view_angle_deg=0.0, acceptance_deg=0.0, obliquity='along');從台帳取用則 opsflyvision.get("sampling_alias_distance"))
週期性目標在取樣晶格上發生混疊的距離——檢測相機工作距離的規則。
> 以下的詳細說明為原文 —— 摘要與標題已翻譯。
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 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 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*.
• 範例資料目錄(下載 URL / 授權) —— 2-D 用 skimage.data(BSD/公有領域)加合成圖,3-D 給出真實資料源(Stanford/PDS 等)的下載 URL。
• 運算子來歷與參考文獻 —— 該運算子族所依據的研究/方法出處。
• 演算法的正典(作者、年份)與用途見上面的族使用指南。
• poc_zebra_stripes_fly_eye — py -3.11 examples/poc_zebra_stripes_fly_eye.py
table 作為輸入)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 運算子登記表。本條目由 tools/opdocs.py md 自動產生(請勿手動編輯)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.