Primer (web-enriched 2026-08-03)
A SPAD is an avalanche photodiode biased above breakdown (“Geiger mode”), so a single photon triggers a self-sustaining avalanche and a digital pulse. That makes it a photon counter with picosecond timing rather than an analogue light-level sensor — the basis for time-of-flight ranging, fluorescence-lifetime imaging (FLIM), Raman spectroscopy, quantum optics and photon-counting imaging.
The commercially interesting shift is compute under the pixel: 3D-stacking digital logic beneath the SPAD array so counting, timing and histogramming happen on-chip before data leaves the sensor. Both independents and incumbents are now competing on this ground.
Market structure — the incumbent is STMicroelectronics
This corrects a long-standing framing error in Image Sensor Silicon, which anchored its incumbent argument on Sony’s ~50% CMOS-image-sensor share. That is the mainstream CIS roof and does not describe SPAD.
- Stmicroelectronics leads, on CMOS-integrated SPAD, vertical manufacturing, and huge consumer + automotive ranging volume. 28 nm FD-SOI integration, sub-40 ps timing.
- Sony Semiconductor Solutions — mass production of a 512x512 SPAD for LiDAR and AR headsets since Jan 2024.
- Hamamatsu Photonics — strong in scientific and medical instrumentation.
- Canon — CES Jan 2026 prototype: 2/3”, ~2.1 MP, 156 dB (~26 stops) via “weighted photon counting” (estimate total arrivals from time-to-first-photon). Computation applied at the counting layer. Canon states it aims for mass production.
The absorption read: incumbents are not absent from computational SPAD. They are building it, at volume, aimed at automotive and consumer. Independents cluster in scientific, quantum and medical instrumentation, where volumes are inherently low.
The independent cohort
Note the lineage concentration: Edinburgh (Robert Henderson’s lab) and EPFL (Charbon) produce most of the European independents.
Open question
Why have the incumbents not fully internalised in-pixel-compute SPAD, and can they? Canon’s weighted-photon-counting prototype suggests they are moving on exactly this ground. This is the single question that decides whether Image Sensor Silicon is a theme or a thesis, and it remains unresolved.
Full scan, sources and source-quality flags:.