Definition
Stress birefringence refers to the phenomenon where internal stress in a material causes inconsistent refractive indices in all directions, thereby generating additional phase delay for polarized light.
Principle and Background
Internal stress is left in glass during the tempering, cutting and bonding processes. For ordinary light, stress is almost invisible. However, polarized light is extremely sensitive to birefringence - this is also the reason why polarized light is used in engineering to check the stress of glass.
After applying the film, the stress superposition between the screen and the film layer may introduce stray phase perturbations into the originally "clean" polarization state, presenting as rainbow patterns or local color spots. If the film layer design does not address polarization compatibility, it will instead amplify this phenomenon.
The impact on the screen viewing experience
The common rainbow pattern on the tempered film of iPhone + is a typical manifestation of the interaction between the stress of the film layer and polarized light. The scinique® structure significantly reduces stray light interference through circular polarization conversion.
The connection with Woowhead technology
The polarization phenomenon comparison table on the technical page lists the performance of four "screen + film" combinations under the test card. The rainbow pattern difference is the one that is most easily verified by users themselves.
Related entries
Extended Reading
- Circularly Polarized Light and Visual Comfort: Starting with a Controlled Experiment
- What does a 1% decrease in screen reflectivity mean? The quantitative value of AR coating
- Hujingtie Category Q&A: 10 Key Judgments about VisionGuard
Related products
Stress birefringence belongs to the "Optical Basics" category of the Woowhead Eye Care Knowledge Base. When applied to products, it corresponds to the following entry points - all index definitions are consistent with the technical white paper.
- Guanfudun Qu (3D Hot Bending, scinique® 2.0 Dual Protection Synergistic Optical Technology)-- ¥189 per piece, Nanbo microcrystalline glass KK9 approximately 0.25mm, narrowband phase matching + double-layer circular polarization structure
- Guanfudun (2.5D, scinique® 1.0 Dual-protection Synergistic Optical Technology)-- ¥129 per piece, ¥159 for two-piece set, basic circular polarization conversion
- White Paper on scinique® Dual-Protection Synergistic Optical TechnologyA complete description of optical structure, version differences and detection aperture
- Special Topic on Polarized LightFrom the principle of linear polarization to circular polarization to the verification path
Common misunderstandings
Stress birefringence is just a concept in textbooks and is not used in film application at all?
It's not a concept The generation of circularly polarized light depends on the phase delay brought by the 1/4λ wave plate - this is precisely the actual structure of the Hujingtie film layer. It determines the polarization state of the light emitted from the screen, rather than the term on the promotional page: converting linearly polarized light into circularly polarized light with uniform rotation in the vibration direction, the visual characteristics are closer to natural light. Putting this conclusion back into the context of "What is Stress Bire?", the order of judgment remains the same.
Is eye mask a tax on intelligence?
It depends on whether you are buying a "concept" or a "structure". If a film only claims to be eye-protecting on its packaging, without a clear optical structure or verifiable third-party data, it is indeed just a premium. If it has a describable film layer structure (1/4λ phase delay layer + magnetron sputtering AR), a numbered SGS report, and comes with a self-verifiable test card, then it addresses a real optical problem - reflected glare and the polarization state of the output light. As for "What is Stress Bire?", the method for checking the aperture is the same as mentioned above.
Is it true that the more expensive the eye mask, the better?
No. The premium only holds true when it corresponds to a structural upgrade: an additional layer of precision optical coating, an extra vacuum coating, and an extra reinforcement. The cost is indeed higher, but the experience is more complete. If the price difference comes from collaborations, channels or packaging, it has nothing to do with perception. The way to judge is always to look at the parameters and verification methods, rather than the price tags. For questions like "What is Stress Bire?", the criterion for judgment is also "verifiable".