Rearview Mirror Camera Layout With OCA for Low-Visibility Cabin Monitoring
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Solution Overview
Problem
Existing vehicle vision systems face challenges in reducing the visibility of cameras integrated into mirror assemblies, particularly due to issues with camera placement, optical path clarity, and minimizing contrast with surrounding components.
Innovation Solution
The system incorporates a prismatic mirror reflective element with a wedge-shaped glass substrate and a mirror reflective coating, utilizing an optically clear adhesive (OCA) and a neutral density (ND) filter to improve the optical path and reduce camera visibility. The camera is positioned to view through the OCA, mirror reflector coating, and glass substrate, with optional ND filter and light emitter configurations for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the camera is integrated into the mirror assembly, then the system achieves compact integration and reduced component count, but the camera visibility increases and optical path clarity deteriorates
Solution Approach 1:
An optically clear adhesive (OCA) layer is introduced as an intermediary between the camera lens and the mirror reflective element. This OCA layer serves as a mediator that maintains optical clarity while enabling the camera to be positioned behind the mirror element, thus reducing visible camera presence while preserving image quality.
Solution Approach 2:
The camera is repositioned from a traditional front-facing location to a rearward position behind the mirror reflective element. This dimensional relocation allows the camera to capture images through the mirror element, thereby concealing the camera while maintaining its imaging function.
2Object-affected harmful factors
If the camera is positioned behind the mirror reflective element, then camera visibility is reduced, but optical path clarity and image capture quality worsen
Solution Approach 1:
The optically clear adhesive (OCA) acts as a high-quality optical intermediary that minimizes light scattering and refraction. This mediator ensures that light passing from the scene through the mirror element to the camera maintains optimal clarity, thereby preserving image capture quality despite the camera's rearward position.
Solution Approach 2:
The optical parameters of the adhesive layer are carefully controlled to optimize light transmission. By selecting materials with specific refractive indices and controlling the thickness and uniformity of the OCA layer, the system maintains optimal optical transmission characteristics while enabling the camera to view through the mirror element.
3Object-affected harmful factors
If an optically clear adhesive (OCA) is applied at the mirror reflector coating, then optical path clarity is improved and camera visibility is reduced, but manufacturing complexity increases
Solution Approach 1:
The OCA application process is merged with the existing mirror assembly manufacturing workflow. The adhesive is applied during the same assembly sequence where the camera and mirror element are integrated, combining multiple functions (optical coupling, mechanical bonding, and sealing) into a single manufacturing step, thereby minimizing additional complexity.
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 reduces the visibility of the camera while maintaining optimal image capture capabilities, addressing issues of camera visibility and optical clarity in vehicle vision systems.
Implementation Method 1
The camera views through (i) the OCA, (ii) the mirror reflector coating of the prismatic mirror reflective element, and (iii) the glass substrate of the prismatic mirror reflective element
Implementation Method 2
a mirror assembly that is adjustably mounted to an interior portion of a vehicle... The mirror casing and reflective element are pivotable about either or both of the ball pivot joints by a user that is adjusting a rearward field of view of the reflective element
Implementation Method 3
Optionally, a neutral density (ND) filter is disposed between the mirror reflector coating and the foam tape and the camera views through the ND filter
Implementation Method 4
A light emitter may be accommodated by the mirror head and operable, when electrically powered to emit light, to emit near infrared (NIR) light
Data Source
AI summary
A vehicular cabin monitoring system includes an interior rearview mirror assembly having a mirror head that accommodates a prismatic mirror reflective element. A camera is accommodated by the mirror head. The mirror reflective element is adhesively attached at a mirror back plate of the mirror head. An optically clear adhesive (OCA) and a neutral density (ND) filter are disposed between the mirror back plate and a mirror reflector coating disposed at a rear side of the mirror reflective element. The camera views through (i) the OCA, (ii) the ND filter, (iii) the mirror reflector coating of the mirror reflective element, and (iv) the glass substrate of the mirror reflective element. With the interior rearview mirror assembly attached at an interior portion of a vehicle, image data captured by the camera is processed at an electronic control unit (ECU) for a cabin monitoring function.