Imaging Lens System Thermal Defocus Compensation
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Solution Overview
Problem
Existing imaging lens systems face challenges in maintaining optical characteristics across a wide temperature range while being compact and efficient, leading to defocus issues due to refractive index changes and thermal expansion.
Innovation Solution
The proposed imaging lens system consists of a configuration with a first lens group having negative power, a second lens group with positive power, and a third lens group including both positive and negative power lens elements, optimized to satisfy specific relative refractive index temperature coefficients and Abbe number conditions, ensuring minimal defocus and aberration correction across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact imaging lens system is designed, then the size is reduced, but temperature characteristics deteriorate due to defocus from refractive index changes
Solution Approach 1:
The patent applies parameter changes by carefully selecting lens materials with specific relative refractive index temperature coefficients (dn/dt) and Abbe numbers. The first lens group uses materials with dn/dt between 2.0×10^-6 and 8.0×10^-6, while the second lens group uses materials with dn/dt between -8.0×10^-6 and -2.0×10^-6. This parameter selection compensates for thermal defocus while maintaining a compact lens structure.
Solution Approach 2:
The patent employs composite materials by combining lens elements with different thermal optical properties. The first lens group combines positive and negative power elements with specific dn/dt values, creating a composite structure that counteracts thermal expansion effects. This allows the compact lens to maintain focus across temperature ranges by balancing the refractive index changes of different materials.
2Reliability
If lens elements with specific refractive index temperature coefficients are selected, then temperature characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The patent defines specific parameter ranges for manufacturability: dn/dt for the first lens group between 2.0×10^-6 and 8.0×10^-6, and for the second lens group between -8.0×10^-6 and -2.0×10^-6. These ranges balance temperature compensation performance with the availability of standard optical materials, making the design practical for manufacturing while achieving excellent temperature characteristics.
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 maintains optical performance and reduces defocus caused by temperature changes, making it suitable for applications in varying environmental conditions, such as on-vehicle cameras, by controlling refractive index changes and thermal expansion effects.
Implementation Method 1
an imaging lens system includes, in order from an object side to an image side: a first lens group having negative power; a second lens group having positive power; and a third lens group having positive power
Implementation Method 2
excellent temperature characteristics that the optical characteristics does not vary with a wide range of temperature change
Implementation Method 3
dn/dt pi is a relative refractive index temperature coefficient, of any i-th lens element having positive power included in an entire system, for light in a wavelength range from 580 nm to 640 nm, inclusive, in air in a range from 0°C to 20°C, inclusive
Data Source
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AI summary
An imaging lens system includes, in order from an object side: a first lens group consisting of at least one lens element having negative power; a second lens group having positive power and configured with a single lens element; and a third lens group having power, and the third lens group includes a lens element having positive power and a lens element having negative power. In addition, conditional expressions (1) and (2) shown below are simultaneously satisfied: -1.2 × 10-5 < dn/dtpi< 0, where i ≥ 1 (1); -1.0 × 10-6 < dn/dtmi < 1.5 × 10-5, where i ≥ 1 (2), where dn/dtpi is a relative refractive index temperature coefficient, of an i-th lens element having positive power included in an entire system for light in a wavelength range from 580 nm to 640 nm in air in a range from 0°C to 20°C, and dn/dtmi is a relative refractive index temperature coefficient, of an i-th lens element having negative power included in the entire system for light in a wavelength range from 580 nm to 640 nm in air in a range from 0°C to 20°C.