Rearview Mirror NIR Filter for Hidden DMS Camera Imaging
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Solution Overview
Problem
Existing interior rearview mirror assemblies face challenges in hiding cameras from vehicle occupants while maintaining efficient infrared (IR) and near-infrared (NIR) light transmission for imaging purposes.
Innovation Solution
The proposed interior rearview mirror assembly incorporates a mirror head with a camera and a light emitter, featuring a light absorption filter layer that absorbs a higher portion of visible light and a lower portion of IR or NIR light, allowing the camera to capture image data while being hidden from view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light absorption filter layer is added to hide the camera from vehicle occupants, then the camera visibility is reduced, but the transmission of IR and NIR light for imaging is blocked
Solution Approach 1:
The light absorption filter layer is designed with wavelength-selective properties, absorbing visible light to hide the camera while transmitting IR and NIR wavelengths for imaging. This local quality differentiation allows the same filter layer to simultaneously achieve both hiding the camera and maintaining imaging functionality.
Solution Approach 2:
The filter layer employs composite material structure combining multiple absorbing layers with different characteristics. This composite approach enables selective absorption of visible light while maintaining transmission of IR and NIR wavelengths, resolving the contradiction between camera concealment and imaging efficiency.
2Object-affected harmful factors
If a light absorption filter layer is added to hide the camera, then the camera is concealed, but heat generation increases due to absorbed light energy
Solution Approach 1:
The filter layer parameters are optimized to absorb only specific visible light wavelengths while allowing IR and NIR transmission. By changing the absorption characteristics to be wavelength-selective rather than broadband, the filter conceals the camera while minimizing total energy absorption and heat generation.
3Object-affected harmful factors
If the light absorption filter layer absorbs more visible light to better hide the camera, then camera concealment improves, but the overall light transmission efficiency decreases
Solution Approach 1:
The filter layer exhibits different optical properties at different wavelengths - high absorption in visible range for concealment, high transmission in IR and NIR ranges for imaging efficiency. This local quality variation resolves the contradiction by making the filter's effect location-specific to different parts of the electromagnetic spectrum.
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 hides the camera from vehicle occupants by absorbing a significant portion of visible light while allowing a high percentage of IR or NIR light to pass through, enhancing the efficiency of the illumination system and minimizing heat generation.
Implementation Method 1
The light absorption filter layer absorbs a portion of light that passes through the light absorption filter layer. When light passes through the light absorption filter layer, the light absorption filter layer absorbs a higher portion of visible light and a lower portion of IR light or NIR light.
Data Source
AI summary
A cabin monitoring system includes an interior rearview mirror assembly including a mirror head having a mirror reflective element that includes (i) a planar glass substrate, (ii) a transflective mirror reflector at the glass substrate and (iii) a light absorption film including a polarizer film. A camera accommodated by the mirror head views through the reflective element. A light emitter accommodated by the mirror head emits near infrared (NIR) light through the reflective element. The light absorption film attenuates greater than 60 percent of visible light and less than 30 percent of NIR light incident on the light absorption film and transmits less than 40 percent of visible light and greater than 70 percent of NIR light through the light absorption film. The camera captures image data representative of NIR light emitted through the reflective element and reflected from the interior cabin of the vehicle back through the reflective element.