Time-Division-Multiplexed (TDM) NIR strobe & trigger hub for multi-camera hand/gesture capture. Designed for 2–4 stereo rigs (i.e., 4–8 mono cameras) with small, staggered baselines to improve precision and occlusion robustness.
- Per-frame strobing: supports single-strobe patterns (one pulse per exposure).
- Optics: the prototype uses 120° emitters for fast bring-up; production targets 60° / 90° for higher efficiency (less wasted light, better SNR in the target ROI).
- Spectrum: default 850 nm NIR illumination. 850 nm and 940 nm are both IR-A and not inherently eye-safe—safe operation depends on irradiance, duty cycle, distance, and exposure time (see Safety below).
Note: Off-the-shelf strobe hubs with the required deterministic MCU timing/control are not available; this module is custom-built.
Safety: Never look into emitters. Both 850 nm and 940 nm can be hazardous at sufficient intensity. 940 nm may reduce visible glow, but it is not automatically safer. See the Safety section below.
Status: Early prototype (electronics/firmware WIP). Interfaces, API, and connectors may change.
- Simple host control over UART: the MCU is configured from a Raspberry Pi 5 (or any Linux host) via a minimal UART protocol.
- Deterministic timing on the MCU: the host only sets parameters; the MCU executes trigger + strobe timing with microsecond-level determinism.
- Deterministic lighting for global-shutter stereo/triangulation.
- TDM (A/B/C/D) phase scheduling prevents cross-illumination between stereo pairs.
- Low-latency trigger fan-out with a simple 4-wire sync option (for chaining / multi-node setups).
- Integrated dimming (global & per-channel) for fine-grained brightness control.
- Deterministic timing: microsecond-level trigger + strobe timing is executed on the MCU (not in Linux userspace).
- Low latency: minimize buffering and keep the host path simple (UART config + status only).
- Scalable multi-rig: support 2–4 stereo rigs by time-slicing illumination into phases (A/B/C/D).
- Repeatable and debuggable: explicit states (ARM/RUN/STOP), readable status, and clear fault reporting.
- Hardware-first safety: conservative defaults, explicit enable, and documented eye-safety constraints.
TDM = Time Division Multiplexing. The frame time is split into phases (A/B/C/D).
In each phase, only one rig (or one illumination group) is allowed to emit NIR.
This prevents cross-illumination (rig A lighting rig B’s exposure) and keeps stereo matching stable.
coming soon.
Apache‑2.0 (code, firmware, docs). Hardware files: to be added; may use CERN‑OHL‑S.
- Never look into emitters. Use black matte baffles/shields, aim emitters away from faces, and add hardware interlocks (LEDs off on loss of sync, open covers, or presence detection).
- Keep exposure short (strobe pulses strictly within camera exposure) and average irradiance low.
- Prefer 850 nm band-pass filters on cameras to reduce the required LED output power.
- 850 nm and 940 nm are both IR-A and are not inherently eye-safe; safety depends on irradiance, geometry, duty cycle, distance, and exposure time (IEC 62471).
Option A — Prefer more viewpoints over more power (recommended for 940 nm)
- If 940 nm illumination is preferred (reduced visible glow), the recommended approach is to increase the number of stereo rigs (viewpoints) to maintain SNR while keeping irradiance low, rather than compensating with higher-power NIR emitters.
Option B — Side / rear placement (recommended)
- Mount stereo pairs left/right and slightly behind the workspace, aimed toward the work area. Add one or two top stereo pairs for occlusion-free coverage. This directs NIR away from the eyes while maintaining uniform scene illumination. Future refinement: recess-mount one stereo pair near the table center and another near the back edge for a slimmer, more robust setup.
Option C — Front placement with HMD only
- If stereo pairs must face forward, operate with a closed VR headset (no see-through optics) so the user’s eyes are occluded. Baffles and interlocks are still required to protect bystanders.
Option D — IR-filtering safety eyewear
- Use visible-light-transmitting eyewear that strongly attenuates near-IR (≈ 780–950 nm) (specified optical density at 850 nm / 940 nm) so users retain normal vision while IR exposure is reduced.
Option E — Side-shield eyewear (“horse-blinkers” concept)
- Provide IR-blocking safety glasses with side shields for operators and visitors when emitters face forward. Ensure proper near-IR attenuation ratings and a snug fit to block off-axis radiation.
Prototype hardware. Use at your own risk. Ensure eye‑safety and proper thermal design in all setups.