Lens Unit Sealing Structure for In-Vehicle Camera Moisture Control
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Solution Overview
Problem
Existing in-vehicle camera lens units face issues with moisture entering through various paths, leading to dew condensation on lens surfaces, which degrades image quality and resolution.
Innovation Solution
A lens unit configuration that integrates the first and second lenses with an annular body, which fits over the outer circumferences of these lenses to cover the joint portion and provide a seal portion to prevent water vapor from entering the inter-lens space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an O-ring is interposed between the first lens and the lens barrel for waterproofing, then water and dust can be prevented from entering the lens group, but moisture can still enter through gaps between the caulking portion and the first lens, leading to dew condensation
Solution Approach 1:
The sealing function is divided into multiple segments: the O-ring seals the gap between the lens barrel and first lens, while the second seal structure (including the second O-ring and seal resin) seals the inter-lens space between the first and second lenses. This segmentation approach ensures that moisture cannot penetrate through either path, effectively preventing dew condensation while maintaining waterproofing performance
Solution Approach 2:
The inter-lens space between the first and second lenses is sealed in advance using the second seal structure before moisture can enter and cause condensation. The seal resin fills and seals the gap between the second lens and lens barrel, creating a preliminary barrier that prevents moisture migration into the inter-lens space where temperature differences could cause condensation
2Adaptability or versatility
If the lens unit is installed outside the vehicle, then the first lens is exposed to outside air and rain causing cooling, but the image sensor generates heat creating a temperature difference that promotes water vapor condensation
Solution Approach 1:
The inter-lens space between the first and second lenses is extracted and sealed as a separate sealed chamber using the second seal structure. This isolation prevents moisture from the warm image sensor area from migrating into the cooler inter-lens space, thereby preventing condensation while maintaining the ability to install the lens unit outdoors where temperature differences occur
3Reliability
If a diameter-reduced portion is provided on the first lens for O-ring attachment, then the O-ring can be compressed to seal the lens barrel, but gaps remain between the caulking portion and the first lens allowing moisture entry
Solution Approach 1:
The first and second seal structures are merged into a coordinated sealing system. The first seal (O-ring at the diameter-reduced portion) handles the external seal, while the second seal (O-ring and seal resin at the inter-lens space) handles the internal seal. This merging of sealing functions into a unified system ensures comprehensive moisture protection without requiring excessive separate components
Solution Approach 2:
The second lens acts as an intermediary element that, together with the second O-ring and seal resin, creates a secondary sealing barrier. This intermediary seal structure bridges the gap between the first lens assembly and the lens barrel, preventing moisture from passing through the first seal's gaps and entering the inter-lens space
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 effectively suppresses water vapor entry into the inter-lens space, preventing dew condensation on lens surfaces and maintaining image quality and resolution, even in high-humidity environments.
Implementation Method 1
the annular body includes a seal portion for tightly sealing an inside of an inter-lens space between the first lens and the second lens against the outside
Implementation Method 2
an image sensor (imaging element) for receiving light condensed through, for example, the lens unit and converting the light into an electric signal
Implementation Method 3
the temperature in the lens unit rises due to heat transferred from a constantly electrically-conductive image sensor
Implementation Method 4
the temperature in the lens unit rises due to heat transferred from a constantly electrically-conductive image sensor (imaging element) for receiving light condensed through, for example, the lens unit and converting the light into an electric signal
Implementation Method 5
when the difference between an outside air temperature and a temperature in the lens unit increases, the water vapor in the lens unit condenses and dew condensation occurs on a lens surface
Data Source
AI summary
A lens unit including a lens group formed by aligning a plurality of lenses along an optical axis; and a lens barrel having a cylindrical shape and including an inner accommodation space for accommodating and holding the lens group, the lens group including a first lens located to be closest to an object side and a second lens adjacent to the first lens on an image side, the lens unit including an annular body that integrates the first lens and the second lens and that is fit to outer circumferences of the first lens and the second lens to cover a joint portion between the first lens and the second lens from an outside, and the annular body is fit to an inner circumferential surface of the lens barrel, and includes a seal portion for tightly sealing an inside of an inter-lens space.