Vehicle HUD Reflective Optical System Chromaticity Control
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Solution Overview
Problem
Conventional head-up display devices face challenges in suppressing chromaticity changes while reducing damage from external sunlight, as infrared rays can cause heat damage to the display unit and lead to elliptical polarization and chromaticity alterations due to the use of dielectric multilayer films in reflective optical systems.
Innovation Solution
A reflective optical system with a dielectric multilayer film is arranged on the path of the source light, with a polarization axis angle between 0 and 90 degrees or 90 and 180 degrees, and a retardation range of subject wavelengths between −π/2 and π/2 radians, to prevent infrared rays from reaching the display unit and minimize chromatic dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a dielectric multilayer film is used as a reflective optical system to block infrared rays, then damage to the display unit from sunlight is reduced, but chromaticity changes occur due to elliptical polarization
Solution Approach 1:
A wavelength plate is introduced as an intermediary component between the display unit and the reflective optical system. This wavelength plate converts the linearly polarized light from the display unit into circularly polarized light before it reaches the dielectric multilayer film, thereby preventing the elliptical polarization and chromaticity changes that would otherwise occur upon reflection.
Solution Approach 2:
The invention changes the polarization state parameter of the light by using a wavelength plate with specific optical properties. The wavelength plate is designed to introduce a phase difference of π/2 between orthogonal polarization components, transforming linear polarization into circular polarization and ensuring that the reflected light maintains its chromaticity.
2Object-affected harmful factors
If a reflective optical system is arranged on the light path to block infrared rays, then heat damage to the display unit is reduced, but the device complexity increases
Solution Approach 1:
The wavelength plate serves multiple functions: it converts the polarization state of the display unit's output light, compensates for the polarization changes induced by the reflective optical system, and maintains the chromaticity of the projected light. By combining these functions into a single component, the overall device complexity is minimized while still achieving the desired protection and optical performance.
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 restricts infrared ray damage to the display unit and suppresses chromaticity changes in the projected light, maintaining color accuracy while reducing heat-induced damage.
Implementation Method 1
The reflective optical system includes a dielectric multilayer film that transmits an electromagnetic wave in an infrared region and reflects an electromagnetic wave in a visible light region
Implementation Method 2
When the source light from the display unit is reflected on the cold mirror, a retardation occurs between s-wave and p-wave, resulting in elliptical polarization
Data Source
AI summary
A head-up display device includes an illumination optical system, an imaging optical system and a reflective optical system. The illumination optical system emits a source light indicating information. The imaging optical system projects the source light to a projection surface. The reflective optical system has a dielectric multilayer film, and is configured so that a retardation of a subject wavelength including at least a part of wavelengths of the source light from the illumination optical system is in a range greater than −π/2 [rad] and smaller than π/2 [rad]. The reflective optical system is arranged on a path from the illumination optical system to the imaging system so that a polarization axis of the source light from the illumination optical system defines an angle α satisfying a relation of 0 degree <α<90 degrees <α<180 degrees, relative to an incident surface.