Camera Module Thermal Focus Compensation via Threaded Lens Holder
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Solution Overview
Problem
Automotive camera modules face challenges in maintaining focus stability over varying temperatures due to thermal expansion of the lens holder, which causes the image sensor to move out of the image plane, deteriorating image quality.
Innovation Solution
The camera module design includes a lens objective with outer threads and a lens holder with co-operating inner threads, where the lens objective is engineered to increase the distance between the image plane and itself with temperature, balancing thermal expansion and maintaining the image plane near the image sensor, using materials like glass, plastics, and metal for lenses and spacers to enhance temperature insensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lens holder is made of standard materials, then it is easy to manufacture, but the distance between the lens objective and image sensor changes with temperature causing focus deterioration
Solution Approach 1:
The patent applies thermal expansion by designing the lens objective with an outer thread and the lens holder with a co-operating inner thread, where the threaded connection is engineered to increase the distance between the image plane and lens objective with increasing temperature. This thermal expansion mechanism compensates for the lens holder's expansion, maintaining focus stability without requiring additional compensating parts.
Solution Approach 2:
The patent changes physical parameters by designing the threaded connection with specific pitch and engagement characteristics that cause the distance between the image plane and lens objective to vary with temperature. By carefully selecting thread parameters and engagement depth, the system achieves automatic focus compensation through parameter changes rather than mechanical adjustment.
2Reliability
If additional compensating elements are added to counteract thermal expansion, then focus stability is improved, but device complexity and mounting difficulty increase
Solution Approach 1:
The patent merges the thermal compensation function into the existing lens objective and lens holder assembly by using their threaded connection. Instead of adding separate compensating elements, the design combines the structural support function with the thermal compensation function in the same components, reducing overall device complexity while maintaining focus stability.
Solution Approach 2:
The lens objective and lens holder perform self-compensation for thermal expansion through their threaded connection design. The system automatically adjusts the image plane distance in response to temperature changes without requiring external control mechanisms or additional compensating parts, making the components self-sufficient for both structural and compensation functions.
3Manufacturing precision
If the distance between lens objective and image sensor is tightly controlled, then image quality is maintained, but thermal expansion causes the sensor to move out of focus
Solution Approach 1:
The patent applies preliminary anti-action by designing the threaded connection to preemptively counteract the effects of thermal expansion. The thread pitch and engagement are calculated in advance to produce an opposing distance change that cancels out the lens holder's expansion, maintaining focus across temperature ranges before problems occur.
Solution Approach 2:
The patent introduces dynamics by allowing the distance between the lens objective and image sensor to vary dynamically with temperature through the threaded connection mechanism. Rather than maintaining a fixed rigid distance, the system adapts the spacing dynamically in response to thermal conditions, preserving focus stability across varying temperatures.
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 design ensures clear image detection across a wide temperature range by compensating for thermal expansion, maintaining precise focus stability and image quality in motor vehicle applications.
Implementation Method 1
the lens holder expands with increasing temperature, and therefore the distance between the lens objective and the image sensor increases along the optical axis with increasing temperature
Data Source
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AI summary
A camera module (12) for a motor vehicle comprises a lens objective (20), a lens holder (53) holding said lens objective (20), and a back plate (32) connected to said lens holder (53) and holding an image sensor (24) in or close to an image plane (A) of the lens objective (20). The materials, shapes and/or relative positions of the components of the lens objective (20) are designed to keep the image plane A in or close to the sensitive plane of the image sensor (24) over an operating temperature range of the camera module (12).