Optical System Thermal Expansion Compensation
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Solution Overview
Problem
Temperature changes in camera systems for advanced driver assist systems (ADAS) cause fluctuations in the back focal length, leading to defocusing and degradation of image quality due to expansion or contraction of lens elements.
Innovation Solution
An optical system with a lens barrel integrally formed with a lens mount, where both are connected to a substrate, featuring specific coefficients of thermal expansion (CTEs) that limit changes in the back focal length, maintaining image clarity across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lens elements are used to direct light into the image sensor, then image capture function is achieved, but temperature changes cause back focal length changes leading to defocusing and image quality degradation
Solution Approach 1:
The patent changes the physical parameters of the lens barrel and lens mount by selecting materials with specific coefficients of thermal expansion (CTE). The lens barrel has a first CTE and the lens mount has a second CTE, which are carefully chosen to compensate for thermal expansion effects and maintain stable back focal length across temperature variations.
Solution Approach 2:
The patent employs composite material selection where the lens barrel and lens mount are made from materials with different CTEs. This composite approach allows the system to leverage the thermal expansion characteristics of each material to achieve overall dimensional stability of the back focal length despite temperature changes.
2Reliability
If the lens barrel and lens mount are made from materials with different CTEs, then thermal stability of back focal length is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the lens barrel and lens mount into a single integrated component. This consolidation simplifies the manufacturing process by reducing the number of separate parts and assembly steps, while still maintaining the functional distinction between the lens barrel and lens mount through appropriate material selection and design within the integrated structure.
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
Prevents defocusing and image degradation by ensuring the back focal length remains stable despite temperature changes, ensuring consistent image quality for ADAS applications.
Implementation Method 1
The lens barrel has a first coefficient of thermal expansion (CTE). The lens mount has a second CTE. At least one of the first and second CTEs limits a change in the back focal length as a result of a change in temperature of the optical system
Data Source
AI summary
An optical system includes a substrate. An image sensor is on the substrate. The image sensor has an image plane. A lens barrel defines a mechanical axis that intersects the image sensor and image plane. The lens barrel has a first coefficient of thermal expansion (CTE). A lens mount is integrally formed with the lens barrel. The lens mount is connected to the substrate. The lens mount has a second CTE. At least one lens element is in the lens barrel on the mechanical axis and defines an optical axis. A last powered optical surface of the at least one lens element is spaced along the optical axis from the image plane by a back focal length. At least one of the first and second CTEs limiting a change in the back focal length as a result of a change in temperature of the optical system.