Fresnel Lens Member With Diffraction Grating for Thin Light Emission
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Solution Overview
Problem
Conventional Fresnel lenses for light-emitting devices are thickened on the outer peripheral side when formed, leading to increased thickness and longer molding times, which affects cost and mass productivity, while also experiencing issues with light utilization efficiency and ring-shaped lens flare.
Innovation Solution
A lens member with a Fresnel lens on the center axis and a diffraction grating structure around the periphery, featuring annular minute grooves with varying inclination angles, is used to thin the lens while maintaining high light-collecting performance, incorporating a first and second Fresnel lens configuration and a diffraction grating structure to optimize light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional Fresnel lens is used to thin the lens structure, then the lens thickness is reduced, but the outer peripheral side becomes thickened due to the prism shape, increasing overall thickness and molding time
Solution Approach 1:
The lens is divided into two functional zones: a central Fresnel lens region for light collection and an outer diffraction grating region for light redirection. This segmentation allows each zone to be optimized independently, with the diffraction grating region enabling thinner outer periphery while maintaining optical performance.
Solution Approach 2:
Different optical structures are applied to different regions of the lens: the Fresnel lens structure is used in the central region where light collection is critical, while the diffraction grating structure is used in the outer peripheral region where light redirection is needed. This local differentiation optimizes both thickness and productivity.
2Manufacturing precision
If the prism top ends are formed with narrow angles to achieve high-accuracy light reflection, then metal molds with narrow top ends are required, but resin cannot fully enter, causing rounded tops and degraded performance
Solution Approach 1:
The mechanical total internal reflection structure (prisms with narrow top ends) is replaced with an optical diffraction grating structure in the outer peripheral region. This substitution eliminates the mold filling problem while achieving the desired light redirection function through diffraction rather than total internal reflection.
3Manufacturing precision
If light reflection surfaces are set higher to totally reflect light from rounded prism tops, then manufacturing accuracy is improved, but the lens thickness is disadvantageously increased
Solution Approach 1:
The total internal reflection mechanism requiring high prism tops is replaced with a diffraction grating mechanism in the outer peripheral region. The diffraction grating achieves light redirection without requiring the prism tops to be set higher, thereby maintaining thin lens thickness while ensuring complete light utilization.
4Use of energy by moving object
If conventional Fresnel lens design is used, then light collection is achieved, but light loss occurs in areas between the refractive lens portion and reflector portion
Solution Approach 1:
The lens structure is designed to perform multiple functions: the central Fresnel lens region collects light, while the outer diffraction grating region both redirects and utilizes light that would otherwise be lost. This multi-functional design eliminates dead zones and maximizes light utilization efficiency across the entire lens surface.
Solution Approach 2:
The light that would normally be lost in the outer peripheral region is converted into a useful resource by the diffraction grating structure, which redirects this light toward the light emission surface. This transforms what was previously a loss area into a productive light-collecting zone.
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 achieves a thinner lens member with enhanced light-collecting performance, improved light utilization efficiency, and reduced ring-shaped lens flare, enabling cost-effective and high-productivity manufacturing of light-emitting devices with a large light emission area.
Implementation Method 1
a diffraction grating structure arranged around a periphery of the Fresnel lens and arranged to be centered around the center axis
Implementation Method 2
a Fresnel lens arranged on a center axis that passes through a center of the light-incident side
Implementation Method 3
Part of incident light beams is totally reflected by a non-lens surface provided on some of the plurality of prisms
Data Source
AI summary
A lens member includes a light-incident side; a light-exit side that is opposite to the light-incident side, a Fresnel lens arranged on a center axis that passes through a center of the light-incident side, and a diffraction grating structure arranged around a periphery of the Fresnel lens and having a center through which the center axis passes. Also, it is disclosed that the Fresnel lens may include a first Fresnel lens and a second Fresnel lens, the first Fresnel lens includes annular prisms that are divided from a convex lens and having a center through which the center axis of the light-incident side passes, and the second Fresnel lens includes annular prisms that are divided from a TIR lens and arranged around the periphery of the first Fresnel lens, centering around the center axis of the light-incident side.