Cemented Lens Unit Resolving Resin Shrinkage Recesses
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Solution Overview
Problem
Conventional lens units with cemented lenses face issues of optical property deterioration due to resin shrinkage during molding, leading to recesses at the convex lens surface, which affect aberration correction and image resolution.
Innovation Solution
The lens unit design ensures a center thickness to flange part thickness ratio of 2.0 to 3.2 for the second lens, regulating the injection pressure and using an adhesive layer with a refractive index closer to the second lens to minimize recess formation, while maintaining a lens diameter to thickness ratio and Abbe number relationships to optimize aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the convex lens surface greatly protrudes from the second flange part to reduce aberration, then the aberration reduction efficiency is improved, but a recess generated due to resin shrinkage occurs at the apex of the convex lens surface
Solution Approach 1:
The patent applies parameter changes by establishing specific numerical ranges for the center thickness T0 and flange part thickness C of the second lens, with the ratio T0/C being 0.7 to 1.5. This quantitative parameter control ensures the convex lens surface can protrude sufficiently for aberration reduction while preventing resin shrinkage recesses during molding, thus resolving the contradiction between optical performance and manufacturing reliability
Solution Approach 2:
The patent uses partial action by allowing the convex lens surface to protrude from the second flange part, but limits this protrusion through the T0/C ratio constraint. This partial protrusion is sufficient to achieve the required aberration reduction without excessive protrusion that would cause resin shrinkage issues, balancing optical efficiency with manufacturing feasibility
2Shape
If the distance from the gate to the apex of the convex lens surface is increased, then the convex lens surface can greatly protrude, but injection pressure cannot be properly transmitted and recesses occur
Solution Approach 1:
The patent resolves this contradiction through parameter changes by defining the center thickness T0 and flange part thickness C with a specific ratio range of 0.7 to 1.5. This parameter control ensures the distance from gate to apex is optimized, allowing sufficient protrusion for aberration reduction while maintaining proper injection pressure transmission to prevent resin shrinkage recesses
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 design effectively reduces chromatic aberration and minimizes optical property deterioration by ensuring proper transmission of injection pressure and filling recesses with the adhesive layer, maintaining image quality.
Implementation Method 1
the recess is filled with an adhesive layer during formation of a cemented lens
Implementation Method 2
the refractive index n0 of the adhesive layer is closer in value to the refractive index n2 of the second lens than the refractive index n1 of the first lens
Data Source
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AI summary
In a cemented lens (4) used for a lens unit, a first lens (6) is a plastic lens including a concave lens surface (620) facing a side of a second lens (7). The second lens (7) is a plastic lens including a convex lens surface (710) bonded by an adhesive layer (5) on the concave lens surface (620), and a second flange part (75) surrounding, at an outer peripheral side, the convex lens surface (710). When T0 denotes a center thickness in an optical axis L direction of the second lens (7) and C denotes a thickness in the optical axis L direction of the second flange part (75), the thicknesses T0 and C satisfy the following relationship of: 2.0 ≤ T0/C ≤ 3.2.