Compact Imaging Lens with Concave Second Group for Onboard Cameras
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Solution Overview
Problem
Onboard cameras require a compact and lightweight imaging lens system with excellent optical performance capable of operating across a wide temperature range and waveband, including the visible and near-infrared regions, while maintaining a small exterior size to protect the car's appearance.
Innovation Solution
A 4-group imaging lens configuration with a first lens group having positive power, a second lens group featuring a concave surface on the object side, a third lens group as a cemented lens with positive and negative powers, and a fourth lens group with negative power, optimized to correct field curvature and chromatic aberration, and optionally a 4-group 6-lens or 5-lens configuration with specific surface orientations and refractive indices to minimize size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional 4-group lens system with a convex surface on the object side of the second lens group is used, then chromatic aberration can be corrected, but the lens system size and weight are large
Solution Approach 1:
The patent changes the surface configuration parameter of the second lens group from convex to concave on the object side, and optimizes the focal length ratios between lens groups. This parameter change enables a more compact lens design while maintaining chromatic aberration correction through the cemented lens structure in the third group.
Solution Approach 2:
The lens system is divided into four distinct lens groups with specific functions: the first group for positive power, the second group with concave surface for field curvature correction, the third cemented group for chromatic aberration correction, and the fourth group for negative power. This segmentation allows each group to be optimized independently for size and performance.
2Measurement precision
If the first lens group has a large diameter to maintain optical performance, then imaging quality is improved, but the exposed lens size increases and car appearance is compromised
Solution Approach 1:
The patent optimizes the focal length ratios between lens groups, specifically setting the ratio of the second lens group focal length to the whole system focal length within a specific range. This parameter optimization allows for a smaller first lens group diameter while maintaining imaging quality through the coordinated design of all four lens groups.
3Weight of stationary object
If a compact lens design is pursued to reduce size and weight, then onboard camera requirements are met, but optical performance and aberration correction deteriorate
Solution Approach 1:
The third lens group uses a cemented lens structure combining a positive power lens and a negative power lens with different Abbe numbers. This composite structure corrects chromatic aberration across the visible to near-infrared waveband while maintaining a compact overall lens size, achieving both size reduction and optical performance.
4Ease of manufacture
If the second lens group has a convex surface on the object side as in conventional designs, then manufacturing is simplified, but field curvature is not well corrected and radial size is large
Solution Approach 1:
The patent inverts the conventional design by making the object-side surface of the second lens group concave instead of convex. This inversion effectively corrects field curvature and reduces the radial size of the lens system. The concave surface configuration refracts off-axis beams along the optical axis, achieving compact radial dimensions while maintaining manufacturability through standard molding techniques.
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 configuration achieves a significant reduction in size and weight while maintaining excellent optical performance, correcting various aberrations and ensuring high-resolution imaging signals across the desired waveband, and reducing the exposed lens diameter to minimize external exposure.
Implementation Method 1
a lens in the most object side of the second lens group has a concave surface on the object side... off-axis beam is refracted along an optical axis
Implementation Method 2
the third lens group is set to be the cemented lens of a lens having a positive power and a lens having a negative power... chromatic aberration is corrected well in a wide waveband from a visible range to a near infrared region
Data Source
AI summary
An imaging lens is provided and includes: in order from an object side of the imaging lens, a first lens group having a positive power as a whole; a second lens group including a lens in the most object side thereof, the lens having a concave surface on the object side thereof; a third lens group including a cemented lens of a lens having a positive power and a lens having a negative power; and a fourth lens group having a negative power as a whole.