Vehicular Camera Focus Stability via Low CTE Stanchions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Automotive cameras face challenges in maintaining precise lens-to-imager focus across a wide temperature range due to the coefficient of thermal expansion (CTE) of materials used in camera assemblies, leading to focus shifts and difficulties in achieving long-term control.
Innovation Solution
The use of low CTE stanchions or posts made from materials like Invar or Kovar, which have a coefficient of thermal expansion less than 5 ppm/°C, to attach the printed circuit board to the camera housing, allowing for temperature-induced movement that maintains focus by reducing or increasing the effective length of the higher CTE support structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional materials with higher CTE are used in camera assembly, then ease of manufacture is improved, but focus precision deteriorates due to temperature-induced lens-to-imager misalignment
Solution Approach 1:
The patent changes the physical parameter of the support structure material by selecting a material with a specific coefficient of thermal expansion (CTE) that matches or closely approximates the CTE of the lens material. This parameter matching ensures that both components expand and contract at similar rates with temperature changes, maintaining focus precision without requiring complex manufacturing processes or adjustments.
Solution Approach 2:
The patent directly addresses thermal expansion effects by selecting support structure materials whose thermal expansion characteristics match those of the lens. This allows the support structure to compensate for temperature-induced dimensional changes in the lens, preventing focus shifts while using conventional manufacturing techniques for materials like aluminum or aluminum alloys.
2Reliability
If materials with matched CTE are used for lens and support structure, then focus stability over temperature range is improved, but material selection becomes more restricted
Solution Approach 1:
The patent identifies and specifies acceptable ranges for the CTE parameter of support structure materials, allowing engineers to select from multiple material options (including various aluminum alloys and other metals) that fall within these ranges. This approach maintains focus stability while providing sufficient material versatility for different manufacturing requirements and performance specifications.
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 focus of the lens at the imager over a large temperature range, reducing the need for costly re-designs and adjustments, and enhancing the precision of image capture in varying environmental conditions.
Implementation Method 1
the stanchions or posts or attachment elements comprising a material having a coefficient of thermal expansion (CTE) that is very low (such as less than about 5 ppm/° C.), and that is lower than the CTE of the housing and circuit board
Data Source
AI summary
A vehicular camera includes a camera housing having front and rear camera housing portions. An imager is disposed at a printed circuit board. A lens assembly is disposed at the front camera housing portion and accommodates at least one lens. The front camera housing portion is formed of a material having a first Coefficient of Thermal Expansion (CTE). At least two attachment elements are disposed at the front camera housing portion and are formed of a material having a second CTE that is less than the first CTE of the front camera housing portion and that is less than 10 ppm/° C. The printed circuit board is mounted at the attachment elements via fasteners threadedly engaging respective ones of the at least two attachment elements. The front camera housing portion and the attachment elements cooperate to decrease temperature-induced movement of the printed circuit board relative to the at least one lens.