Subwave Grating Optical Element for Reducing Fresnel Reflection
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Solution Overview
Problem
Conventional optical scanning devices face issues with Fresnel reflection on plastic lens surfaces, leading to flare and ghosting due to the difficulty in applying anti-reflection coatings, which deteriorate image quality.
Innovation Solution
An optical element with a two-dimensionally arranged subwave structural grating is introduced, where the distances between subwave structures vary, and the grating pitch is set to be shorter than the wavelength of light, achieving an anti-reflection effect without additional coatings by controlling reflectance through specific geometric relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plastic lenses are used in the optical system, then manufacturing cost and ease of production are improved, but Fresnel reflection occurs on the lens surfaces causing flare and ghosting
Solution Approach 1:
The patent divides the lens surface into multiple regions by forming a subwave structural grating consisting of numerous small protrusions or recesses. This segmentation of the surface structure creates multiple interfaces that reduce Fresnel reflection through distributed scattering and interference effects, while the base lens remains a single plastic component for easy manufacturing.
Solution Approach 2:
The patent applies the subwave structural grating only to specific optical surfaces where Fresnel reflection is problematic, rather than modifying the entire lens uniformly. The grating structure is localized to the surface layer while the bulk plastic material maintains its original properties, achieving reflection reduction without compromising manufacturing simplicity.
2Object-generated harmful factors
If anti-reflection coating is applied to reduce Fresnel reflection, then image quality is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines the anti-reflection function with the lens manufacturing process itself by forming the subwave structural grating directly on the lens surface during molding or finishing operations. This merging eliminates the need for separate anti-reflection coating steps, reducing manufacturing complexity while achieving the same optical effect.
Solution Approach 2:
The subwave structural grating provides self-service anti-reflection functionality through its geometric structure alone, without requiring additional coating materials or complex multi-layer structures. The grating's physical form factor (subwave scale dimensions) inherently provides the anti-reflection effect through optical interference, making the system self-sufficient.
3Object-generated harmful factors
If subwave structural grating is formed on lens surface, then Fresnel reflection is reduced improving image quality, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the grating parameters (protrusion height, spacing, cross-sectional shape) to achieve effective anti-reflection within practical manufacturing tolerances. By selecting specific parameter ranges for the subwave structure, the design achieves reflection reduction while remaining compatible with standard manufacturing capabilities for plastic optical components.
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
This solution effectively reduces Fresnel reflection, improving image quality by minimizing flare and ghosting, and maintaining uniform light intensity distribution on the scanned surface without the need for additional processing like coating.
Implementation Method 1
an optical element in which a subwave structural grating having an anti-reflection function associated with an incident angle of a light beam is provided
Data Source
AI summary
Provided is an optical element capable of reducing Fresnel (surface) reflection on a lens surface which causes flare or ghost, an optical system including the optical element, and an optical scanning device including the optical element. The optical element includes: a plurality of two-dimensionally arranged subwave structures having an anti-reflection function, and in the optical element when directions orthogonal to each other within a plane including a tangent of a vertex of the optical surface are set as a first and second directions, each of distances between the subwave structures changes in at least one of the first and second directions, and an arbitrary subwave structure is located with a state in which a distance between the arbitrary subwave structure and one of the subwave structures closest to the arbitrary subwave structure is shorter than ½ of an average wavelength of the light beam incident on the optical surface.