Diffractive Optical Element Sealed Dielectric Films Moisture Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Volume holograms in head-mounted displays degrade due to moisture entry, causing deviation of interference stripes and degradation of deflection characteristics, which existing dielectric films fail to adequately prevent.
Innovation Solution
A diffractive optical element with a holographic element sealed by dielectric films on its upper, lower, and side surfaces, including adhesive layers and substrates, functions as a water vapor barrier to prevent moisture entry and maintain deflection characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric films are formed only on upper and lower surfaces of the volume hologram, then the structure is simple and manufacturing is easier, but moisture can still enter through side surfaces causing degradation of deflection characteristics
Solution Approach 1:
The patent extends the protective coverage from two dimensions (upper and lower surfaces) to three dimensions by adding side surface coverage. The water vapor barrier layer is formed to cover not only the upper and lower surfaces but also the side surfaces of the volume hologram, creating a complete three-dimensional barrier against moisture entry.
Solution Approach 2:
The patent employs a thin film water vapor barrier layer that can conform to the three-dimensional structure of the volume hologram. This flexible barrier layer is formed through vapor deposition processes and can effectively seal the side surfaces, preventing moisture penetration while maintaining the compact structure.
2Reliability
If dielectric films are formed on all surfaces including side surfaces, then moisture protection is improved, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The patent uses a universal vapor deposition process that can simultaneously form water vapor barrier layers on multiple surfaces (upper, lower, and side surfaces) in a single operation. This multi-functional approach eliminates the need for separate coating processes for each surface, simplifying the overall manufacturing procedure.
Solution Approach 2:
The patent replaces complex mechanical coating methods with vapor deposition technology. The water vapor barrier layer is formed by depositing material from the vapor phase, which automatically conforms to complex three-dimensional geometries without requiring precise mechanical alignment or multiple positioning steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses moisture absorption and maintains the deflection characteristics of the holographic element, preventing degradation and ensuring reliable operation of the head-mounted display.
Implementation Method 1
a first dielectric film provided between the first substrate and the holographic element, a second dielectric film provided on another surface side of the holographic element, and a third dielectric film provided on a side surface side of the holographic element
Implementation Method 2
By the diffraction of the light at the holographic element, the image light formed by the image formation unit is deflected toward the eyes (pupils) of the user
Data Source
AI summary
A diffractive optical element according to the invention includes a holographic element configured to deflect incident light, a first substrate provided on one surface side of the holographic element, a first dielectric film provided between the first substrate and the holographic element, a second dielectric film provided on another surface side of the holographic element, and a third dielectric film provided on a side surface side of the holographic element.