Optical Coating Suppresses Interference Fringes
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Solution Overview
Problem
Plastic optical substrates, such as spectacle lenses, face challenges with interference fringes due to refractive index differences and nonuniform thickness, leading to unsightly appearance and glare, especially under specific light sources like three-band fluorescent lamps, and existing solutions require complex manufacturing facilities and multiple designs for varying refractive indexes.
Innovation Solution
A functional layer with a controlled period of reflectance in the k-space, not exceeding 3.66×10−5 nm−1, is applied to the optical substrate, which suppresses interference fringes by maintaining a consistent refractive index and thickness, allowing for a single coating system to work across different refractive indexes, reducing manufacturing burdens and glare issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is formed on a high refractive index plastic substrate, then scratch resistance is improved, but interference fringes appear due to refractive index difference and thickness nonuniformity
Solution Approach 1:
The hard coating layer is divided into multiple sub-layers with different refractive indexes. The first sub-layer has a refractive index closer to the substrate, the second sub-layer has a refractive index closer to air, creating a gradient that reduces interference fringes while maintaining scratch resistance
Solution Approach 2:
Different portions of the coating system have different refractive indexes tailored to specific functions: the first sub-layer addresses the substrate-coating interface with matching refractive index to minimize reflection, while the second sub-layer provides the hard protective function with higher refractive index
2Length of moving object
If the refractive index of the substrate is increased to reduce lens thickness, then lens thickness is reduced, but interference fringes become denser and more apparent
Solution Approach 1:
The coating is segmented into sub-layers with progressive refractive index changes, allowing the system to accommodate high refractive index substrates without producing visible interference fringes
Solution Approach 2:
The refractive index parameter is changed progressively through the coating thickness, creating a gradient that adapts to the substrate's high refractive index and eliminates the conditions that produce interference fringes
3Object-affected harmful factors
If a special hard coating is designed for each substrate refractive index to suppress interference fringes, then interference fringes are suppressed, but manufacturing facility complexity increases
Solution Approach 1:
The multi-sub-layer coating design is universal and can be applied to substrates with various refractive indexes. By adjusting the thickness ratios of the sub-layers rather than redesigning the entire coating system, the same basic structure serves multiple substrate types
Solution Approach 2:
Instead of changing the coating material composition for each substrate, the solution changes the thickness parameter of existing sub-layers to adapt to different substrate refractive indexes, simplifying manufacturing
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 minimizes perceivable interference fringes, maintains surface accuracy, and allows for a common coating system across various refractive indexes, simplifying production and reducing costs while enhancing the optical article's appearance and functionality.
Implementation Method 1
interference fringes are formed due to the difference in refractive index and nonuniformity in the thickness
Implementation Method 2
the period Pk (nm−1) of reflectance (reflection coefficient) of the functional layer in the k-space
Data Source
AI summary
An optical article includes: an optical substrate, and a functional layer that is light-transmissive and is laminated to the surface of the optical substrate, the period Pk (nm−1) of reflectance of the functional layer in the k-space being not more than 3.66×10−5.