Max Exposure per Line.

The math behind this calc is the simplest possible formulation: a linescan camera, by construction, reads exactly one row of pixels at each readout event, and consecutive readouts happen at a fixed rate (the line rate, in Hz). The time between consecutive readouts is 1 ÷ line rate — that's the row period (T_row). The maximum possible integration time per row is exactly T_row: any longer and the camera's exposure for one row would overlap with the next row's readout, corrupting the per-row pixel values by mixing photons from two distinct intervals. The relationship is hard physics — exposure cannot exceed the inter-readout interval — and the upper bound is exactly that interval. Practical operating points often use shorter exposures than the maximum (to avoid motion-blur during transport, to gate strobe pulses to a sub-row window, or to stay within the camera's electronic exposure-control limits), but the maximum is the ceiling above which the line readouts overlap.

The per-row exposure budget sits at the centre of linescan illumination strategy. At default 50 kHz line rate the calc lands t_exposure_max = 20 μs — the standard MV linescan production register where high-flux LED bar illumination delivers adequate SNR for typical inspection contrast. The budget compresses linearly with line rate: doubling to 100 kHz collapses the budget to 10 μs; doubling again to 200 kHz collapses it to 5 μs (squarely in very-tight territory where high-flux halogen line lights or very-high-flux LED arrays with strobe-sync timing become the only viable illumination strategies); halving to 25 kHz expands it to 40 μs (moderate territory where standard LED bars suffice). The slow end of typical MV linescan operation (1–10 kHz line rates for low-feature-density inspection or scanning-microscope applications) lands the budget in the 100–1000 μs ample territory where even continuous-current LED illumination delivers sufficient flux. The fast end (≥ 500 kHz; specialty silicon inspection, printing-press inspection, TDI-stage operations) crosses into critical territory below 2 μs where single-stage SNR is physically limiting and TDI delay-and-add (LS6) becomes the operational answer to multiply effective exposure across N parallel sensor stages.

The exposure-budget-class register below the diagram reads off the computed maximum exposure directly: ample (≥ 500 μs) is slow-line-rate territory where standard-flux LED bar or even continuous-current LED illumination suffices for adequate SNR (specialty inspection, scanning-microscope-style line readouts, low-feature-density inspection of large parts at low line rates); moderate (50–500 μs) is moderate-line-rate inspection territory (2–20 kHz; standard-flux LED bar illumination delivers adequate SNR; exposure budget is comfortable but not abundant); tight (10–50 μs) is the standard MV linescan production register (20–100 kHz; default 50 kHz → 20 μs lands here — the canonical mid-range MV inspection register; high-flux LED bar illumination required for adequate SNR; the standard production-line camera + lighting pairing); very-tight (2–10 μs) is high-speed production inspection territory (100–500 kHz; demands very-high-flux LED illumination with strobe-sync timing OR high-flux halogen line lights with active cooling); critical (< 2 μs) is TDI / specialty / ultra-fast linescan (≥ 500 kHz; single-stage exposure budgets become physically limiting; inspection often migrates to TDI stages — LS6 — to multiply effective exposure via delay-and-add). This calc is the per-row exposure ceiling for the chosen line rate; pair it with the Along-Scan Pixel Size calc (verify the resulting along-scan pitch matches the cross-scan target), the Line Rate For Square Pixels calc (size the line rate that delivers square reconstruction; the exposure budget at THAT rate is the binding illumination constraint), and the TDI Signal/SNR Gain calc (for low-light high-speed setups where single-stage SNR is inadequate, TDI multiplies effective exposure across N stages). For areascan sensors the exposure budget is set by the frame-rate ceiling rather than the per-row line-rate ceiling — a different binding question (M2 — Rolling Shutter Flash Duration — covers the analogous areascan timing constraint when strobing is required).