Head-Up Display Brightness Control Without Color Shift
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Solution Overview
Problem
Existing head-up displays for vehicles face challenges in adjusting image brightness for daytime and nighttime driving, as current methods either fail to reduce brightness sufficiently at night or alter the color of the emitted beam, and generate excessive heat.
Innovation Solution
A control method that independently adjusts light beam intensity using an attenuation unit, comprising an active and passive polarizer, to maintain consistent color and reduce heat, by varying the polarization orientation and using pulse width modulation to control the light source and attenuation unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the supply current to the light source is decreased to reduce light intensity for nighttime driving, then the light intensity is reduced, but the color of the emitted beam changes
Solution Approach 1:
The light intensity control is segmented into two independent parts: the light source intensity control and the attenuation unit control. The attenuation unit (polarizer) is separated from the light source, allowing independent control of light intensity without affecting the light source's operating parameters and color emission characteristics.
Solution Approach 2:
An intermediary element (the attenuation unit/polarizer) is introduced between the light source and the driver's field of vision. This intermediary attenuates the light intensity without requiring changes to the light source current, thereby maintaining color consistency while achieving the desired brightness reduction for nighttime driving.
2Illumination intensity
If the supply current to the light source is decreased to reduce light intensity, then the light intensity is reduced, but the light intensity cannot be reduced as much as desired
Solution Approach 1:
The brightness control function is segmented between the light source (providing base intensity) and the attenuation unit (providing additional attenuation). This segmentation enables a wider overall brightness adjustment range by combining the limited current control range with the polarizer's attenuation capability.
Solution Approach 2:
The attenuation unit serves as an intermediary that extends the brightness adjustment range. By placing the polarizer between the light source and the driver, the system achieves greater light intensity reduction than would be possible by current control alone, while maintaining the light source within its optimal operating range.
3Illumination intensity
If an active polarizer is used to reduce light intensity independently of current supply, then light intensity can be controlled, but significant heat is generated
Solution Approach 1:
The patent replaces the active polarizer (which requires electrical actuation and generates heat) with a passive polarizer. This substitution eliminates the need for electrical control of the polarization element, thereby eliminating the heat generation associated with active polarizer actuation while maintaining the light intensity attenuation function.
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
Achieves high daytime brightness and low nighttime brightness without color loss and minimal heat generation, ensuring safe and effective visibility for drivers.
Implementation Method 1
an active polarizer designed to vary the polarization orientation of the light beam
Implementation Method 2
a passive polarizer. The two polarizers together reduce the intensity of the light beam passing through them
Data Source
Figure 1~2b
AI summary
The invention concerns a method for controlling a head-up display (10) for a motor vehicle (V) which comprises an image generating unit (12) capable of emitting a light beam transporting images (Img), and an attenuation unit (14) for attenuating the luminous intensity of said light beam, said control method comprising: - a step of compiling an instruction for controlling a light source (12A) of the image generating unit, - a step of compiling an instruction for controlling the attenuation unit, and - a step of controlling said light source and said attenuation unit according to the two control instructions; wherein the control instruction of the attenuation unit is compiled according to the setting of a parameter relative to the luminous intensity of said light beam with respect to a threshold value.