Lenticular Lens Array with Intermediate Material to Reduce Fresnel Reflections
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Solution Overview
Problem
Lens arrays suffer from significant Fresnel reflections, leading to reduced image contrast, visibility of the lens surface, and scattering that degrades optical performance, particularly in display applications, where existing solutions like thin film interference coatings are costly and not easily scalable.
Innovation Solution
A lens element comprising a rear and front substrate with surface reliefs and an isotropic intermediate material between them, which reduces Fresnel reflections through total internal reflection and alignment elements, allowing for easier manufacturing and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a lens array is formed with a single substrate having a relief surface, then the device structure is simple and manufacturing is easier, but Fresnel reflections cause reduced image contrast and visibility of the lens surface
Solution Approach 1:
The lens array is divided into two separate substrates, each with its own relief surface. The first substrate contains lens surfaces that direct light into viewing windows, while the second substrate contains additional lens surfaces that work in conjunction with the first. This segmentation allows each substrate to be optimized independently and reduces the harmful Fresnel reflections by distributing the optical functions across multiple interfaces.
Solution Approach 2:
An intermediate material layer is introduced between the first and second substrates. This intermediate material acts as a mediator that optically couples the two substrates while reducing the Fresnel reflections at their interfaces. The intermediate material has a refractive index that is intermediate between the substrates, creating a gradient that minimizes reflection losses and improves image contrast.
2Object-affected harmful factors
If thin film interference coatings are applied to reduce Fresnel reflections, then surface reflectivity is reduced, but the cost increases and scalability is limited
Solution Approach 1:
Instead of applying thin film interference coatings, the invention changes the fundamental parameter of the optical system by using two substrates with relief surfaces and an intermediate material with a specific refractive index. This parameter change approach reduces Fresnel reflections through the optical design itself rather than through costly coating processes, making the solution more scalable and cost-effective for mass production.
3Area of stationary object
If the pitch of lenses is reduced to improve viewing angle, then the lens array can cover more area, but manufacturing precision requirements increase
Solution Approach 1:
By segmenting the lens array into two substrates, each substrate can be manufactured with standard pitch dimensions that are easier to control. The first substrate handles the primary light directing function while the second substrate provides additional optical power. This segmentation allows for more relaxed manufacturing tolerances compared to a single substrate design with reduced pitch.
Solution Approach 2:
The second substrate is essentially a copy of the first substrate, both having relief surfaces with lens structures. This copying approach allows for standardized manufacturing processes and tooling to be used for both substrates, improving manufacturing precision and reducing the complexity of achieving precise pitch control.
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 surface reflections, improving image contrast and optical performance while being cost-effective and suitable for large-scale production.
Implementation Method 1
The liquid or solid isotropic material reduces the degree of Fresnel reflection from the array of lens surfaces, as compared to an equivalent lens element employing a single substrate having a relief surface interfacing with air
Implementation Method 2
The lens element directs light from each image into a respective viewing window
Data Source
AI summary
A lens element comprising: a rear substrate having a front surface provided with a surface relief having a plurality of zones each capable of providing a lens effect; a front substrate disposed in front of the rear substrate and having a rear surface provided with a surface relief having a plurality of zones each capable of providing a lens effect, the zones of the surface reliefs provided on the rear substrate and the front substrate having the same spatial arrangement over the area of the lens element; and solid or liquid, isotropic, intermediate material disposed between the front surface of the rear substrate and the rear surface of the front substrate, the intermediate material having a refractive index different from the refractive index of each of the rear substrate and the front substrate. This construction reduces the degree of Fresnel reflection which would otherwise degrade the optical performance.