Imaging Lens Resin First Element Temperature Focus Shift
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Solution Overview
Problem
On-board cameras experience significant focus shift due to temperature fluctuations, particularly in vehicles where the imaging lens is exposed to direct sunlight, leading to reduced performance in capturing images of traffic lights and brake lamps from a distance.
Innovation Solution
The imaging lens configuration consists of a series of lenses with specific refractive powers and focal lengths, including a convex first lens and negative second lens, along with positive third, fourth, and fifth lenses, and a negative sixth lens, optimized to minimize focus shift through conditional expressions that balance refractive powers and reduce temperature-induced deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the first lens is made of glass with large refractive power to achieve wide-angle performance, then the wide-angle capability is improved, but the focus shift caused by temperature fluctuation increases
Solution Approach 1:
The imaging lens is divided into multiple lens elements (first through sixth lenses) with alternating positive and negative refractive powers. The first lens has negative power and is made of resin, while subsequent lenses have positive or negative powers. This segmentation allows the optical system to achieve wide-angle performance without concentrating excessive refractive power in a single glass lens that would be susceptible to temperature-induced focus shift.
Solution Approach 2:
The patent changes the material parameter from glass to resin for the first lens, and adjusts the refractive power distribution across multiple lens elements. By making the first lens convex toward the object side with negative power and using resin material, the system achieves wide-angle capability while reducing temperature sensitivity. The conditional expressions define specific ranges for focal lengths and refractive powers to optimize this balance.
2Reliability
If the first lens is made of resin to reduce focus shift, then focus stability is improved, but yellowing and scratch resistance deteriorate
Solution Approach 1:
The optical system is segmented into multiple lens elements with different materials and functions. The first lens (resin, negative power) handles the wide-angle function with temperature stability, while subsequent lenses (positive and negative powers) work together to correct optical aberrations and provide protective functions. This segmentation allows each element to be optimized for its specific role without requiring a single material to satisfy all requirements.
Solution Approach 2:
The imaging lens uses composite construction with multiple lens elements made of different materials (resin and glass). The first lens is made of resin for temperature stability, while other lenses may use glass or different resin compositions. This composite approach combines the advantages of different materials: resin provides thermal stability while glass or coated surfaces provide scratch and yellowing resistance.
3Adaptability or versatility
If the refractive power of the first lens is increased to achieve wide-angle performance, then the wide-angle capability is improved, but the amount of focus shift caused by temperature fluctuation increases
Solution Approach 1:
The total refractive power required for wide-angle performance is segmented and distributed across multiple lens elements rather than concentrated in the first lens. The first lens has negative power and moderate magnitude, while positive and negative lenses follow to achieve the overall wide-angle effect. This segmentation prevents excessive refractive power in any single element, reducing temperature-induced focus shift while maintaining wide-angle capability.
Solution Approach 2:
The patent defines specific parameter ranges through conditional expressions to control the distribution of refractive power. The first lens has negative power with focal length within a specific range relative to the total system focal length. Subsequent lenses have positive or negative powers that compensate and balance the optical system. These parameter constraints ensure wide-angle performance is achieved without excessive focus shift.
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 configuration allows for stable imaging performance across a wide temperature range, maintaining focus and reducing aberrations, thereby enhancing the camera's ability to detect traffic lights and brake lamps with improved resolution.
Implementation Method 1
a first lens (L1) that is convex toward the object side and has a negative refractive power
Implementation Method 2
a power of the first lens made of glass, which less causes deformation due to temperature fluctuation, is increased, and a power of the second lens made of resin, which more causes the deformation due to temperature fluctuation, is decreased
Data Source
AI summary
Provided are an imaging lens that has a small amount of focus shift caused by temperature fluctuation and an imaging apparatus that has this imaging lens. The imaging lens consists of, in order from an object side: a first lens that is convex toward the object side and has a negative refractive power; a second lens that has a negative refractive power; a third lens that has a positive refractive power; a fourth lens that has a positive refractive power; a fifth lens that has a positive refractive power; and a sixth lens that has a negative refractive power. The imaging lens satisfies the following conditional expressions (1) to (4).−0.89<f/f12<−0.53 (1)−0.19<f/f1<−0.1 (2)−0.70<f/f2<−0.45 (3)2.4<f1/f2<5.7 (4)