Rear-view mirror with controlled reflectance and near-infrared transmittance
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Solution Overview
Problem
Existing image pickup device-equipped rear-view mirrors face challenges in achieving both sufficient reflectance for vehicle mirrors and glare prevention, while also ensuring improved image pickup performance and appearance, due to incompatibilities in transmittance and reflectance properties of half mirrors and cold mirrors, and issues with visibility and design when parts of the reflecting film are removed.
Innovation Solution
The solution involves a mirror element with integrating sphere reflectance of 40% to 60% in the visible range and near-infrared transmittance of at least 70% for a near-infrared camera, combined with a dark color mask member providing additional near-infrared transmittance, allowing for effective image pickup and glare prevention, along with a reflecting film composed of high and low refractive index materials to optimize reflectance and transmittance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a cold mirror is used as the mirror element, then the reflectance is close to 100% in visible range, but glare is caused to the driver at night
Solution Approach 1:
The patent resolves the glare issue by changing the reflectance parameter from near-100% (cold mirror) to a controlled range of 40%-60% in the visible range. This parameter adjustment reduces the intensity of reflected light to headlight beams, eliminating the glare effect while maintaining sufficient mirror function.
Solution Approach 2:
The patent applies local quality by creating different optical property zones: the mirror element provides controlled reflectance (40%-60%) in visible range to prevent glare, while the dark color mask member provides high transmittance in near-infrared range for image pickup. Each component has optimized local properties for its specific function.
2Illumination intensity
If a cold mirror is used as the mirror element, then the reflectance is high, but the view angle dependency is large causing discontinuous tone in reflected light
Solution Approach 1:
The patent resolves the view angle dependency issue by changing from a cold mirror with fixed near-100% reflectance to a mirror element with controlled integrating sphere reflectance of 40%-60% in visible range. This parameter change creates more uniform angular distribution of reflected light, eliminating the discontinuous tone effect.
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 meets legal reflectance requirements, reduces glare, enhances image pickup performance, and improves the appearance of the mirror by preventing the inside from being seen through, while maintaining effective near-infrared illumination for night vision and minimizing view angle dependency.
Implementation Method 1
the mirror element has an integrating sphere reflectance of 40% to 60% in the visible range, and a near-infrared transmittance of no less than 70%
Implementation Method 2
a reflecting film composed of high and low refractive index materials to optimize reflectance and transmittance characteristics
Implementation Method 3
a dark color mask member providing additional near-infrared transmittance
Data Source
AI summary
The present invention is intended to provide an image pickup device-equipped rear view mirror with improved image pickup performance, glare prevention and appearance (design) in addition to improved performance as a vehicle mirror. A mirror element is formed by forming a reflecting film consisting of high refractive index material films and a low refractive index material film on a back surface of a transparent glass substrate. The integrating sphere reflectance of the mirror element in the visible range is 40% to 60% and the near-infrared transmittance is no less than 70% for the whole or part of the band belonging to the near-infrared range within the entire sensitive wavelength range of the near-infrared camera. A black mask member is attached to an entire back surface of the reflecting film. The near-infrared camera is arranged behind the black mask member. The region corresponding to the area for the image-pickup by the near-infrared camera within the entire region of the black mask member is formed of a visible-light absorption and near-infrared transmission filter. The near-infrared transmittance of the visible-light absorption and near-infrared transmission filter is no less than 70% for the whole or part of the band belonging to the near-infrared range within the entire sensitive wavelength range of the near-infrared camera.