HUD Combiner Wavelength Selective Reflection
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Solution Overview
Problem
Head-up display (HUD) devices with combiners suffer from colored reflection issues, particularly yellow reflections, which interfere with the driver's view due to the trade-off between transmittance and reflectance, and existing combiners do not adequately address these reflections at varying incident angles.
Innovation Solution
A combiner with a reflecting surface that has an average reflectance of 30% or greater for incident light within specific angles and wavelengths, and a semi-transmitting film structure that adjusts reflectance peaks to minimize yellow reflections by ensuring the upper-limit wavelength of high reflectance is shorter than 700 nm and the S-wave component's peak wavelength is less than 570 nm, especially at an incident angle of 70°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the reflectance is increased to enhance virtual image brightness, then colored reflections (particularly yellow) appear and interfere with the driver's view
Solution Approach 1:
The patent applies color changes by designing the combiner to selectively reflect different wavelengths of light based on incident angle. The optical structure is configured to reflect blue-green wavelengths (480-520 nm) from the HUD display while allowing yellow wavelengths (560-580 nm) from the road to pass through. This wavelength-selective reflection eliminates the yellow coloration problem that occurs with conventional high-reflectance combiners, as the yellow light is not reflected toward the driver's eyes.
Solution Approach 2:
The patent employs composite materials by combining multiple layers with different refractive indices and optical properties. The combiner consists of a substrate layer and a semi-transmissive film layer with specific refractive index ranges (1.4-1.7), creating a composite structure that achieves both high reflectance for HUD light and high transmittance for road light. This composite structure enables simultaneous optimization of virtual image brightness and elimination of colored reflections.
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 effectively reduces colored reflections, enhancing the driver's visibility by minimizing yellow and blue components, allowing more green and purple light to pass through, resulting in a whiter virtual image and improved visibility without increasing the cost of LED drivers or compromising heat dissipation.
Implementation Method 1
a reflecting surface that reflects incident light
Implementation Method 2
the upper-limit wavelength of a wavelength range having a reflectance of 90% or more of a reflectance peak of the incident light is shorter than 700 nm. Besides, when the incident angle of the incident light takes a second value in a range from 60° to 85°, inclusive, in the wavelength range from 400 nm to 700 nm, inclusive, a reflectance peak of a S-wave component of the incident light has a wavelength shorter than 570 nm
Data Source
AI summary
The combiner has a reflecting surface that reflects incident light. When the incident light has an incident angle in a range from 0° to 25°, inclusive, defined as a first value, in a wavelength range from 400 nm to 700 nm, inclusive, the upper limit wavelength of a wavelength range having a reflectance of 90% or more of the reflectance peak of the incident light is shorter than 700 nm. When the incident angle takes a second value in a range from 60° to 85°, inclusive, in the wavelength range from 400 nm to 700 nm, inclusive, the reflectance peak of an S-wave component contained in the incident light has a wavelength shorter than 570 nm.