Vehicular Camera Thermal Compensation via Flexible PCB Mounting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Automotive cameras face challenges in maintaining precise lens-to-imager relative position across a range of operating temperatures due to differing coefficients of thermal expansion (CTE) between camera assembly materials, leading to potential bending of the printed circuit board (PCB) and resulting focus issues.
Innovation Solution
The system accommodates thermal expansion and contraction by using oversized holes for mounting screws or elongated posts that allow flexible movement perpendicular to the optical axis, ensuring the PCB remains planar and aligned with the lens, thereby maintaining focus across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the circuit board is rigidly mounted to the lens holder, then the structural stability is improved, but the thermal expansion mismatch causes the circuit board to bend and the imaging plane to misalign with the optical axis
Solution Approach 1:
The mounting structure transitions from a rigid fixed connection to a dynamic flexible connection that allows controlled movement. The flexible posts enable the circuit board to move relative to the lens holder in response to thermal expansion differences, preventing board bending while maintaining imaging alignment through controlled compliance rather than rigid constraint
Solution Approach 2:
The invention changes the mechanical parameter of the mounting structure from rigid to flexible by using compliant posts with controlled flexibility. This parameter change allows the mounting system to accommodate thermal dimension changes in the circuit board without transmitting stress that would cause board bending or imaging misalignment
2Stability of the object's composition
If the circuit board is allowed to move freely to accommodate thermal expansion, then the board remains planar, but the imaging plane may shift away from the optical axis
Solution Approach 1:
The flexible posts create a dynamic mounting system that permits controlled movement in specific directions (perpendicular to optical axis) while constraining movement in other directions (along the optical axis). This selective flexibility maintains board planarity through thermal accommodation while preserving optical alignment by preventing displacement in critical directions
Solution Approach 2:
The mounting structure exhibits local quality differences through the flexible posts that provide directional compliance. The posts are designed to be flexible in directions that accommodate thermal expansion while maintaining rigidity in directions critical for optical alignment, creating localized mechanical properties that simultaneously satisfy both board planarity and optical precision requirements
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 solution effectively maintains the focus of the camera by allowing the PCB to adjust to temperature changes without bending, reducing the risk of over or under focusing, even at extreme temperatures.
Implementation Method 1
the circuit board having a coefficient of thermal expansion (CTE) that is different from the CTE of the lens holder or structure at which the circuit board is mounted
Implementation Method 2
different degrees of thermal expansion and contraction of the circuit board relative to the lens holder
Data Source
AI summary
A vehicular camera includes a camera housing having a first portion and a second portion joined to the first portion. The first portion of the camera housing accommodates a lens and has an attaching portion having a first coefficient of thermal expansion (CTE). A circuit board includes circuitry disposed at a circuit board substrate that has a second CTE that is different from the first CTE. The circuitry includes an imager. The circuit board substrate is attached at the attaching portion of the first portion of the camera housing. When the vehicular camera is operated at an operating temperature greater than 50 degrees C., the attaching portion expands a greater degree than the circuit board substrate. When the vehicular camera is operated at an operating temperature below −20 degrees C., the attaching portion contracts a greater degree than the circuit board substrate.