Optical stability that holds through PPAP — and through SOP.
Cabin-sensing programs live or die on the optical envelope: NIR transmission, scatter, off-axis ghosting, and alignment to the image sensor. PPAP confirms dimensions; we make sure the optics get qualified, too. We engage before tool kickoff and stay in the release record through SOP.
The five places a cabin-sensing program slips on optics.
- Cover / window
- Hard-coat AR stack tuned to the NIR illuminator wavelength, with abrasion and chemical-cleaner exposure budgets that hold through the program's defined service life.
- IR transmission
- Resin and stack chosen so the NIR band is transmitted with the uniformity the sensor's auto-exposure budget assumes — not the band the marketing datasheet hints at.
- Scatter
- Surface roughness and bulk scatter held below the threshold where cabin sunlight rinses out near-eye features. Verified on production cavities, not prototypes.
- Off-axis ghosting
- Internal reflections and stray-light from cabin trim sit inside the modeled budget; coatings and baffles co-designed with the optical-mechanical stack.
- Alignment to image sensor
- Datum strategy locks the optical axis to the sensor package mechanically and through the assembly fixture. Tolerance stack-up covers PCB warp, adhesive cure shrink, and thermal cycle.
PPAP can pass and the optics can still fail — here is how that happens.
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Failure mode
Design freeze without manufacturability sign-off bakes in rework the PPAP cannot rescue.
What we do about it: pre-tool DFM with the actual press, resin, and coating chamber on the table. Gating and clear-aperture conflicts are resolved on paper, before tooling money moves.
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Failure mode
PPAP dimensional pass + optical fail — every calibration looks right on the CMM and wrong on the bench.
What we do about it: wavefront, transmitted MTF, and stray-light measurements ride alongside CMM on the release record. A part that ships is a part qualified for what the sensor actually does.
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Failure mode
Sterilization-free, but thermal-cycle drift surfaces at customer durability — months after PPAP closes.
What we do about it: thermal-cycle coupons from the production cavity, AR-stack shift tracked against the as-deposited reference, and a delta budget the program's reliability lead can audit.
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Failure mode
Supplier handoff at tool kickoff treats the optical engineer as an observer.
What we do about it: a written engagement plan that names the Sandia owner for prescription, DFM, gauge R&R, and PPAP — and the customer-side owner for each. Handoff is documented, not assumed.
Pre-tool work that keeps optical risk out of the PPAP package.
- Pre-tool DFM review — gating, draft, vent placement, sink risk, and clear-aperture conflicts marked up against the prescription.
- Mold-flow analysis on the as-designed cavity, with shear and frozen-stress maps overlaid on the optical aperture.
- Birefringence model under the operating thermal range, with measurement plan on the first molded coupons.
- Datum and alignment strategy locking the optical axis to the sensor package across the tolerance stack.
- Gauge R&R plan for the dimensional and optical measurements that travel with the part to PPAP.
What gets checked, and what evidence travels with the part.
Optical risk checks by lifecycle phase — DMS/OMS programs
| Phase | Optical risk check | Evidence captured |
|---|---|---|
| Concept | Resin and stack feasibility against NIR band, scatter, and birefringence budget | Prescription review notes; polymer selection rationale |
| DFM | Gating and draft compatibility with clear aperture; mold-flow stress map | DFM mark-up; mold-flow report with stress overlay |
| Prototype | First-article wavefront, MTF, stray-light, and AR-stack transmission | Interferometry and spectrophotometer scans on diamond-turned or short-run parts |
| Tool sample | Production-cavity birefringence under crossed polarizers; gate-area witness | Polariscope images; coupon stress data lot-correlated to cavity |
| PPAP | Dimensional CMM plus optical release — wavefront, MTF, thermal-cycle delta | PPAP record extended with optical and environmental sections |
| SOP | Per-lot wavefront, AR-stack shift, and CMM trends against control limits | Lot release record traveling with the parts; SPC charts on critical optical metrics |
Related capabilities
- design Optical & Mechanical Design Imaging and illumination optics designed for manufacturability — DFM lives in the prescription, not the review meeting.
- manufacture Polymer Injection Molding Six all-electric presses, ISO Class 8 cleanroom, closed-loop hold and pack on every cavity.
- finish Metrology & Testing Interferometry, profilometry, spectrophotometry, MTF, and environmental — every part has a number behind it.
Get a DFM review of your DMS/OMS optical stack.
Send the prescription, the sensor datasheet, and the validation matrix. We will tell you where the optical risk concentrates and what we would do about it before tool kickoff.