tcspc op• Data kinds: counts → counts
• Call: import fullseye as fs; fs.ledger.tcspc_background_subtract(hist, method='median', leading_bins=None, quantile=0.5, scale=1.0) (to call the implementation directly, import photoncount; photoncount.tcspc_background_subtract(hist, method='median', leading_bins=None, quantile=0.5, scale=1.0); from the registry, opsphoton.get("tcspc_background_subtract"))
Remove the ambient-light / dark-count floor from an arrival-time histogram.
Outdoors, most of what a dToF sensor counts is sunlight: a roughly uniform pedestal under the return pulse. It biases the centroid toward the middle of the window (a floor of b per bin pulls the first moment toward window/2) and it inflates the apparent signal, so it is removed before any depth or lifetime estimate.
The level is estimated by *method* and then subtracted (the sign trap:
the result is hist - level, clipped at 0, never hist + level):
• "median" (default) — the median of every bin. Robust while the pulse occupies well under half the window, which is the normal dToF case.
• "leading" — the mean of the first *leading_bins* bins, the classical choice when the pulse is known to arrive late (a far target).
• "trailing" — the mean of the last *leading_bins* bins, for fluorescence decays where the tail is background.
• "quantile" — the given *quantile* of all bins, for tuning by hand.
*leading_bins* defaults to None = min(8, len(hist)), so the default call works on a short histogram instead of raising over a constant nobody chose (a fixed default of 8 made method="leading" fail on any histogram with fewer than 8 bins).
*scale* multiplies the estimated level before subtraction (scale=1.2 for a deliberately aggressive removal). Clipping at 0 means the result is a valid non-negative histogram that the rest of this module will accept.
Ground truth: on a noiseless histogram with a known flat pedestal of 20 counts/bin under a 5000-photon pulse covering 5.1% of the window, the median estimate recovers 20.000000 and the returned histogram equals the pedestal- free pulse exactly (measured area error 0.0, pinned in the tests).
Returns a float64 1-D histogram of the same length as *hist*.
Raises ValueError: negative, non-finite or non-1-D *hist*, an unknown *method*, a *leading_bins* outside [1, len(hist)], a *quantile* outside [0, 1], and a negative *scale*.
• photon_timeresolved family guide
• 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.
• photon_timeresolved — py -3.11 examples/photon_timeresolved.py
• poc_dtof_ranging — py -3.11 examples/poc_dtof_ranging.py
counts as input)tcspc_coates_correct · tcspc_irf_convolve · tcspc_stats · dtof_depth · lifetime_fit · lifetime_phasor
tcspc)tcspc_simulate · tcspc_irf_convolve · tcspc_stats
*Provenance: photoncount.py — PHOTON 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.