Six-Element Imaging Lens Design for Thermal Focal Stability
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Solution Overview
Problem
Surveillance cameras in vehicles face challenges in maintaining consistent optical performance across varying temperatures due to temperature-induced variations in focal length, which is exacerbated by the need for high-resolution imaging for both distant and nearby objects with the addition of autonomous driving functions.
Innovation Solution
An image capturing lens system comprising a sequence of lenses with specific refractive powers and materials, including glass and plastic, designed to maintain constant optical performance by incorporating a stop between certain lenses and using aspherical surfaces to reduce thermal deformation, thereby stabilizing focal length across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical surveillance camera lens is used, then the camera can capture peripheral objects, but the resolution is insufficient for autonomous driving functions requiring clear capture of distant and nearby objects
Solution Approach 1:
The lens system is divided into six distinct lens elements with specific refractive powers and material compositions. Each lens element serves a specific function in correcting optical aberrations and maintaining focal length stability, thereby achieving high-resolution imaging while managing system complexity through functional segmentation
Solution Approach 2:
The patent employs composite material construction where at least one lens element is made of glass and others of plastic, with specific refractive indices and Abbe numbers. This composite approach allows optimization of each element's optical properties to achieve high resolution while controlling overall system complexity
2Reliability
If conventional lens materials are used, then manufacturing is simpler, but focal length varies significantly with temperature changes
Solution Approach 1:
The patent carefully selects and controls specific optical parameters including refractive indices (e.g., 1.50 < n_d < 1.70 for plastic lenses), Abbe numbers (e.g., 20 < ν_d < 40), and focal length ratios (e.g., 0.7 < f3/f < 1.3) to minimize thermal deformation. These parameter constraints ensure focal length stability across temperature variations while remaining manufacturable
Solution Approach 2:
By using composite materials with different thermal expansion characteristics (glass and plastic lenses), the system compensates for thermal effects. The glass lens elements provide thermal stability while plastic elements allow for easier manufacturing and cost-effectiveness, achieving both reliability and ease of manufacture
3Measurement precision
If high-resolution imaging is implemented for autonomous driving, then distant and nearby objects can be clearly captured, but the system becomes more sensitive to temperature-induced focal length variations
Solution Approach 1:
The patent establishes specific parameter ranges for lens elements including refractive indices (1.50 < n_d < 1.70), Abbe numbers (20 < ν_d < 40), and focal length ratios (0.7 < f3/f < 1.3) that are optimized to reduce thermal sensitivity. These controlled parameters enable high-resolution imaging while minimizing the harmful effect of temperature variations on focal length
Solution Approach 2:
The stop (aperture) is positioned between the second and third lenses as an intermediary element that helps control light paths and reduce the impact of temperature-induced aberrations. This intermediary component assists in maintaining image quality across varying temperatures while preserving high-resolution capability
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 lens system achieves high-resolution imaging with reduced temperature-dependent variations in focal length, ensuring consistent optical performance and cost-effective manufacturing.
Implementation Method 1
a first lens having negative refractive power, a second lens having positive refractive power while having a convex object-side surface, a third lens having positive refractive power, a fourth lens having positive refractive power, a fifth lens having negative refractive power while having a concave object-side surface and a concave image-side surface, and a sixth lens having positive refractive power
Implementation Method 2
designed to maintain constant optical performance by incorporating a stop between certain lenses and using aspherical surfaces to reduce thermal deformation, thereby stabilizing focal length across temperature changes
Data Source
AI summary
An image capturing lens system includes a first lens having negative refractive power, a second lens having positive refractive power while having a convex object-side surface, a third lens having positive refractive power, a fourth lens having positive refractive power, a fifth lens having negative refractive power with a concave object-side surface and a concave image-side surface, and a sixth lens having positive refractive power.