Vehicle Headlight Projection Lens Chromaticity Control
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Solution Overview
Problem
Conventional vehicle headlight systems using semiconductor light emitting devices and light-transmitting members, such as yellow YAG phosphor, often result in chromaticity issues where the light distribution pattern falls outside the white range, due to uneven absorption and conversion of blue light, leading to color unevenness in the light distribution.
Innovation Solution
A vehicle headlight configuration with a projection lens and light source that emits white light by combining blue and yellow light, where the light emitting surface and incident surface are designed to control light direction, ensuring the chromaticity of the light distribution pattern falls within the white range by adjusting light incidence angles and colors based on position, using semiconductor light emitting devices and light-transmitting members like YAG phosphor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light source combining semiconductor light emitting device and light-transmitting member (yellow phosphor) is used, then white light is emitted, but the chromaticity of the light distribution pattern falls outside the white range due to insufficient blue light absorption
Solution Approach 1:
The patent applies local quality by varying the phosphor layer thickness across different regions of the light emitting device. The phosphor layer has a first thickness in a first region and a second thickness (greater than the first) in a second region, creating spatially non-uniform light conversion properties that compensate for the non-uniform blue light absorption path lengths
Solution Approach 2:
The patent changes the physical parameter of phosphor layer thickness to control the absorption and conversion characteristics. By adjusting the thickness parameter in different regions, the patent optimizes the conversion efficiency of blue light to yellow light, ensuring uniform chromaticity across the light distribution pattern
2Use of energy by moving object
If blue light travels a shorter distance through the light-transmitting member in the normal direction, then more blue light passes through without conversion, but this causes chromaticity to fall outside the white range
Solution Approach 1:
The patent creates different optical paths by varying phosphor layer thickness. Regions with shorter blue light paths have thicker phosphor layers to increase absorption, while regions with longer paths have thinner phosphor layers, achieving uniform chromaticity despite varying path lengths
Solution Approach 2:
The phosphor layer acts as an intermediary that converts blue light to yellow light. By controlling the thickness of this intermediary layer, the patent regulates the conversion efficiency and achieves uniform white light chromaticity across different viewing angles
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
The solution ensures that the entire light distribution pattern, including high-beam patterns, falls within the white range as per JIS D5500 standards, preventing color unevenness and dark areas, thereby enhancing the lighting performance and compliance with color standards.
Implementation Method 1
a light source that uses a combination of a semiconductor light emitting device (such as a blue LED) and a light-transmitting member (such as a yellow YAG phosphor)
Data Source
AI summary
A vehicle headlight can form a predetermined high-beam light distribution pattern, while being capable of causing the chromaticity of the entire light distribution pattern to fall within a white range (JIS D5500). The vehicle headlight can include: a projection lens that can control light incident on its light incident surface at a first incident position near its optical axis to be directed in a direction not parallel to the optical axis, can control light incident at a second incident position away from the optical axis to be directed in a direction parallel to the optical axis, and can control light incident at an incident position between the first and second incident positions to be directed in a direction closer to the direction parallel to the optical axis as the light is incident at an incident position closer from the first incident position to the second incident position.