Plastic Projection Lens Gate Mark Orientation
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Solution Overview
Problem
The manufacturing of aspheric projection lenses for projectors using injection molding often results in defects like bubbles and striae near the gate mark, and more recently, weld lines form on the opposite side, impairing optical performance, especially in large diameter concave meniscus lenses.
Innovation Solution
A projection lens design where the gate mark is positioned on the lens outer edge, and the weld line extends towards the central portion, with the gate mark facing a long side of the rectangular image light pattern, ensuring the weld line remains outside the optical usage area, and the lens is rotatable to prevent weld lines from entering the image pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If injection molding is used to manufacture aspheric projection lenses, then manufacturability and cost are improved, but optical defects such as bubbles, striae, and weld lines are formed around the gate mark and opposite side
Solution Approach 1:
The invention extracts and removes the defective peripheral portion of the lens containing the gate mark and weld lines through a specific cutting process. This separates the harmful defective areas from the optical usage area, allowing the lens to maintain both injection molding manufacturability and high optical quality in the remaining functional portion.
Solution Approach 2:
The invention converts the harmful effect of weld lines and gate marks into a beneficial positioning reference. By deliberately orienting the lens so that these defects are located at specific positions (peripheral areas outside the optical path), the manufacturing characteristics become a useful feature for quality control and optical performance optimization.
2Ease of manufacture
If the gate mark is positioned on the lens outer edge for injection molding, then manufacturing is simplified, but weld lines form on the opposite side extending toward the central portion
Solution Approach 1:
The invention introduces asymmetric positioning of the gate mark on the lens periphery rather than symmetric central positioning. This asymmetric placement, combined with specific rotation angles during installation, ensures that weld lines form in predetermined peripheral locations that fall outside the rectangular optical usage area, thus maintaining both manufacturing ease and optical quality.
Solution Approach 2:
The invention adds a rotational dimension to the lens installation process. By specifying precise rotation angles based on the gate mark position, the solution moves from a two-dimensional lens surface problem to a three-dimensional spatial orientation problem, allowing weld lines to be positioned in safe peripheral zones through rotational adjustment.
3Reliability
If the lens is designed with large diameter concave meniscus shape, then projection performance is improved, but weld lines extend to near the central portion of the lens
Solution Approach 1:
The invention applies local quality differentiation by treating the lens periphery and central optical area differently. The peripheral portion is designed to accommodate manufacturing defects (gate mark and weld lines), while the central optical usage area maintains high quality. The cutting process removes only the defective peripheral zone, preserving the high-performance central region.
Solution Approach 2:
The invention performs preliminary cutting and removal of the defective peripheral portion during the manufacturing process, before the lens is installed in the projector. This preliminary action ensures that weld lines and gate marks are eliminated from the final optical system, preventing future image quality issues while maintaining the projection performance of the remaining lens.
4Manufacturing precision
If weld lines are reduced by controlling molding conditions, then optical performance is improved, but it is difficult to eliminate weld lines completely while preventing defects around the gate mark
Solution Approach 1:
The invention extracts and removes the problematic gate mark area and associated defects through a dedicated cutting process. This extraction approach simplifies the overall solution by physically removing the source of defects rather than attempting to control and prevent them through complex molding parameter optimization, thereby reducing device complexity while maintaining optical performance.
Data Source
AI summary
A projector includes a projection lens having a first lens. The first lens is a plastic lens made by injection molding using a single gate, and has a gate mark on its outer edge. The first lens also has a weld line at the opposite side to the gate mark, which extends from the outer edge. The first lens is positioned such that the gate mark faces a long side of a rectangular pattern of image light on the lens surface, and the weld line becomes disposed outside the rectangular pattern.