looming opsignal → signalimport fullseye as fs; fs.ledger.fly_tau_from_expansion(theta_signal, dt_s, shape='sphere') (実装を直接呼ぶなら import flyvision; flyvision.fly_tau_from_expansion(theta_signal, dt_s, shape='sphere')、台帳から引くなら opsflyvision.get("fly_tau_from_expansion"))Time-to-contact from optical expansion — the tau margin.
From the subtended angle and its rate::
shape="disk": tau = sin(theta) / theta'
shape="sphere": tau = 2*tan(theta/2) / theta'
theta_signal is the full subtended angle over time, radians.
★ The two object models differ by 33% at a 60-degree subtense (sin 60 = 0.866
vs 2 tan 30 = 1.155); using the wrong one silently mis-times a landing, so
the model is a required, named choice rather than a default guess.
theta_signal: the full subtended angle per sample, radians.
dt_s: the sample interval, seconds.
shape: "disk" (a frontal circular disk) or "sphere".
Returns a 1-D float64 array of the time-to-contact per sample, seconds.
Non-expanding samples (theta' <= 0) return NaN — a documented
non-finite, because a contracting or static angle has no time-to-contact and
inventing one would be a plausible-wrong number.
Ground truth: for the model’s own object geometry (theta = 2 asin(l/d) for a
sphere, theta = 2 atan(l/d) for a disk) approaching at speed |v|, the
returned tau equals the true distance-over-speed d/|v| (pinned in the
tests).
Raises ValueError: a non-1-D / empty / too-short (< 3) / non-finite
theta_signal, a signal over :data:MAX_SIGNAL_POINTS, a non-positive dt_s,
and an unknown shape. A non-expanding angle is not an error — it is the
documented NaN return above.
py -3.11 examples/poc_fly_vision.pysignal を入力に取れる)fly_emd_response · fly_lgmd_eta · fly_dsi
looming)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.