AI Facial Analysis System Design
Thought for 3 sec
Work done
- Finalized production MPN metadata for CM4 and all generic passives, then verified the updated schematic/BOM properties.
- Created the comprehensive Clinical Imaging Build Document covering PCB-mounted parts, sourcing guidance, integrated imaging modules, calibration protocol, and TGA-oriented controls.
- Updated Pre-Manufacturing Status with the latest validation snapshot and manufacturing export gate.
- ❌ Fully routed / zero DRC errors: blocked; latest review still reports 62 airwire DRC errors.
- ✅ Imaging validation documentation: calibration, module options, fixture controls, and longitudinal capture SOP are documented.
- ✅ Exact parts and sourcing guidance: key ICs/connectors/modules and passives now have MPN guidance.
- ❌ Manufacturing outputs ready: blocked because Gerber/BOM/PnP export should not proceed until airwires are cleared.
The remaining required action is manual/autorouter routing closure for USB, CSI, power, I2C, LED, and connector nets, followed by DRC recheck and manufacturing export generation once airwires are zero.
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Clinical Imaging Build Document
Release Status
This build is a controlled prototype documentation package for the Medspa AI Facial Imaging Portal. The PCB is not yet manufacturing-exportable because the latest DRC snapshot still reports 62 airwire errors. Gerber, BOM, and pick-and-place export are gated until airwires are zero and no blocking DRC issues remain.
PCB-Mounted BOM
Table
| Block | Designators | Qty | Production MPN / source guidance | Notes |
|---|---|---|---|---|
| Compute | U1 | 1 | Raspberry Pi SC0686 / CM4004032-class CM4, Digi-Key 2648-SC0686-ND or Mouser 358-SC0686 | 4GB RAM / 32GB eMMC, no wireless preferred for EMC/security; SC0674 wireless variant only if clinic workflow requires onboard Wi-Fi/Bluetooth. |
| PWM lighting controller | U2 | 1 | NXP PCA9685PW | 16-channel I2C PWM driver for reference/lighting-control prototype. |
| Secure element | U3 | 1 | Microchip ATECC608A-MAHDA-S; review ATECC608B package-compatible Trust&GO/TrustFLEX variants for production provisioning | Device identity, key storage, signed-update and audit workflows. |
| Camera FFC connectors | J1, J3 | 2 | GCT FFC2B35-22-G_REVA2 | 22-position, 0.5 mm FFC/FPC; production camera cable pinout must be confirmed before fabrication. |
| USB-C service/power | J2 | 1 | GCT USB4105-GF-A | USB 2.0 Type-C receptacle; D+/D-, VBUS, CC1/CC2 routing still pending. |
| Reference LEDs | LED1-LED4 | 4 | Dialight 597-3901-831F | Reference indicators only; clinical illumination must use calibrated external lighting module. |
| I2C pull-ups | R1, R2 | 2 | YAGEO RC0603FR-074K7L | 4.7 kΩ, 0603, 1%, 0.1 W. |
| USB-C Rd | R3, R4 | 2 | YAGEO RC0603FR-075K1L | 5.1 kΩ, 0603, 1%, 0.1 W. |
| LED current limits | R5-R8 | 4 | YAGEO RC0603FR-07150RL | 150 Ω, 0603, 1%, 0.1 W. |
| USB 5 V bulk | C1 | 1 | Murata GRM188R61A106KE69D | 10 uF, 10 V, 0603, X5R MLCC. |
| IC decoupling | C2, C3 | 2 | Murata GRM188R71C104KA01D | 100 nF, 16 V, 0603, X7R MLCC. |
Integrated / Prebuilt Modules
Table
| Subsystem | Recommended module / sourcing | Integration notes |
|---|---|---|
| Primary RGB and stereo/depth imaging | For a CSI-first prototype, use matched IMX477-class camera modules and validate against J1/J3 pinouts; Arducam IMX477 synchronized stereo/Camarray kits are a strong evaluation reference. | Dual CSI on CM4 supports passive stereo, but cable pinout, synchronization mode, lens, baseline, and mechanical lock must be verified before PCB release. |
| Production-grade depth fallback / comparison module | Luxonis OAK-D Pro W, USB-C module with OV9282 global-shutter stereo, active IR dot projector/IR LED, 75 mm baseline, and wide-FOV RGB option. | Use as external validation/reference or integrated module if passive CSI stereo cannot meet repeatability/accuracy targets. Treat as an external module outside the carrier BOM. |
| Color reference | Calibrite ColorChecker Classic Nano, SKU CCC-NANO; B&H and imaging suppliers. | Use in SOP as compact color reference / calibration aid, not as a standalone medical claim. |
| Patient positioning | Rigid chin/forehead rest and fixed camera/illumination fixture. | Must mechanically lock working distance, camera baseline, target position, illumination geometry, and enclosure repeatability. |
| Clinical illumination | External calibrated high-CRI diffuse LED ring/array with validated CCT, uniformity, thermal control, and optional polarization. | PCB LEDs are reference indicators only and are not sufficient for controlled clinical facial illumination. |
Imaging Validation Protocol
- Lock camera modules, lenses, cable routing, fixture baseline, working distance, patient-positioning geometry, and lighting geometry.
- Calibrate camera intrinsics for each camera using traceable calibration target data; store lens, focus, camera serial, operator, target ID, reprojection residual, date/time, and software version.
- Calibrate stereo extrinsics and rectification; store baseline, relative pose, rectification quality, and pass/fail limits.
- Capture verification phantoms and repeatability datasets before clinical claims: flat target, stepped-depth target, facial phantom/headform, and representative skin-tone/color references.
- Gate every clinical capture on focus, exposure, motion blur, alignment, illumination uniformity, color-reference result, stereo correspondence quality, and depth-map completeness.
- Store raw RGB, raw/depth data, calibration versions, AI model version, operator ID, device ID, firmware/software versions, and quality flags with every session.
- Define minimum detectable volume change and repeatability limits by facial region before quantitative volume-loss claims.
TGA-Oriented Documentation Controls
- Label AI output as practitioner-reviewed decision support unless separate regulatory clearance supports stronger claims.
- Maintain controlled records for intended use, risk management, clinical evaluation, cybersecurity, software lifecycle, post-market monitoring, and complaint handling.
- Reports must include calibration status, model/software versions, capture quality flags, confidence/limitations, operator sign-off, and traceability to raw images/depth/calibration records.
- Enforce consent, encryption at rest/in transit, device identity, signed updates, audit logs, retention policy, export/deletion controls, and role-based access.
PCB Routing / Manufacturing Gate
Current state: DRC airwires remain at 62. Export is blocked by the pre-export gate because airwires indicate missing routed copper between pads.
Required routing closure:
- USB D+/D- and USB_P/USB_N: route as short matched USB 2.0 differential pair with continuous ground reference and controlled impedance appropriate to the final stackup.
- CSI J1/J3: route MIPI CSI lane pairs with differential-pair discipline, short stubs, continuous reference, and production pinout verification.
- Power: route VBUS/5V_USB, CM4 3.3 V output, VDD/VCC, and bulk/decoupling returns with low-impedance paths.
- Low-speed/control: route I2C SDA/SCL, GPIO2/GPIO3/GPIO4, PWM LED nets, CC1/CC2, and reference LED nets.
Manufacturing outputs may be generated only after:
- Airwires = 0.
- No blocking overlapping-copper, missing-footprint, or invalid-layer DRC issues.
- BOM reviewed for supplier availability and controlled alternates.
- Camera module/cable pinout and stereo calibration workflow locked.
- Mechanical fixture and calibration SOP baselined.
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