Recessed Core Lens for Stress-Free Thick Optical Components

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Solution Overview

Problem

The challenge is to create a thick optical component with a smaller size without increasing molding time, while preventing the generation of vacuum bubbles and residual internal stress, which is difficult due to the difference in contraction between the surface plastic layer and the inner plastic portion during the injection molding process.

Innovation Solution

The solution involves integrating a core lens with a covering plastic, where the covering plastic is introduced into recessed portions on the front and back surfaces of the core lens, allowing for a smaller outer shape without increasing molding time and eliminating voids and internal stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the thickness of optical component is increased, then the optical performance is improved, but vacuum bubbles and residual internal stress are generated due to contraction difference between surface and inner portions

Engineering Contradiction:
Improvethickness of optical componentVSAvoidvacuum bubble and residual internal stress
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The invention divides the optical component into two segments: a core lens and a covering plastic layer. The core lens is formed first with predetermined thickness, then the covering plastic is injected to cover the front and back optical surfaces. This segmentation allows the core lens to provide the necessary optical thickness while the covering plastic protects the surfaces, avoiding the contraction stress problems that would occur in a monolithic thick component.

Inventive Principle:
Principle #1Segmentation

2Volume of moving object

If the thickness of optical component is increased, then the optical performance is improved, but the molding cycle time is considerably lengthened

Engineering Contradiction:
Improvethickness of optical componentVSAvoidmolding cycle time
Core Design Contradiction:
Volume of moving objectVSLoss of time

Solution Approach 1:

The core lens is formed in advance with the predetermined thickness required for optical performance. Then, in a separate injection molding step, the covering plastic is injected to cover the surfaces. This preliminary formation of the core lens allows the final assembly to be completed quickly without requiring extended cooling times for a single thick component, thus reducing the overall molding cycle time.

Inventive Principle:
Principle #10Preliminary action

3Volume of moving object

If the outer shape of optical component is reduced to match core lens dimensions, then the component size is reduced, but it becomes difficult to prevent vacuum bubbles and internal stress

Engineering Contradiction:
Improveouter shape sizeVSAvoidvacuum bubble and residual internal stress
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The covering plastic is injected to cover only the front and back optical surfaces of the core lens, creating a local quality enhancement at the critical optical interfaces. This localized covering protects the optical surfaces and reduces stress concentration at the interfaces, preventing vacuum bubbles and internal stress while maintaining a compact overall component size that matches the core lens dimensions.

Inventive Principle:
Principle #3Local quality

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 approach enables the production of a thick optical component with a smaller size, maintaining optical performance and reducing the visibility of the bonded interface, thus achieving a compact design without the drawbacks of increased molding time or internal stress.

Implementation Method 1

a covering plastic is introduced onto the front and back optical surfaces of the core lens through a recessed portion

Methodology Applied
Scientific EffectInjection molding:

Implementation Method 2

an increase in stress occurs due to the difference between contraction of a surface plastic layer, which first solidifies during a molding process, and contraction of an inner plastic portion, which solidifies afterwards

Methodology Applied
Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentEP2495096B1Optical component and method of making the same
Publication Date: 2019.09.04 CANON KK
  • EP2495096B1 patent drawingFigure 1A~2
  • EP2495096B1 patent drawingFigure 3A~3B
  • EP2495096B1 patent drawingFigure 4A~4K

AI summary

A recessed portion (4), through which a covering plastic (14) that has been melted and that is used for covering a core lens (1) is introduced in a bifurcating manner, is formed in the core lens (1), and the covering plastic (14) is introduced simultaneously onto the front and back surfaces (5, 6) of the core lens (1) through the recessed portion (4).