Conical Light Guide Stray Light Rejection for Head-Up Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional head-up displays in vehicles adapt the brightness of projected virtual images based on overall ambient light, leading to unsuitable brightness as they consider the entire environment rather than the specific area where the image is superimposed, causing potential distortion.
Innovation Solution
The display's light guide is shaped to eliminate parasitic light radiation from areas beyond the zone of interest, ensuring that only relevant light radiation reaches the light sensor, allowing for precise brightness adjustment of the virtual image based on the local environment's brightness, using a conical light guide with inclined surfaces to deflect and guide light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the light sensor measures the overall ambient light in the environment, then the brightness adaptation covers the entire environment, but the brightness of the virtual image becomes unsuitable because it does not match the local area where the image is superimposed
Solution Approach 1:
The light guide is designed with a specific geometry (conical or pyramidal shape with inclined side walls) to restrict the field of view of the light sensor to only the local area where the virtual image is superimposed. This ensures that the brightness adaptation is locally precise rather than globally averaged, resolving the contradiction between environmental coverage and measurement accuracy.
2Quantity of substance
If the light guide collects light from all directions, then more light reaches the sensor, but stray light from areas beyond the area of interest distorts the brightness adaptation
Solution Approach 1:
The light guide geometry segments the field of view into a useful area (area of interest where the virtual image is displayed) and useless areas (surrounding environment). The inclined side walls create angular acceptance limits that allow light from the relevant area to reach the sensor while blocking stray light from other directions, thus resolving the contradiction between light quantity and stray light rejection.
Solution Approach 2:
The inclined side walls of the light guide, which could potentially reflect stray light into the sensor, are instead designed to reflect such stray light away from the sensor toward the exit face. This converts the potential harmful effect of internal reflections into a beneficial stray light rejection mechanism.
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 solution ensures optimal visibility of the virtual image by accurately adjusting its brightness to match the local ambient conditions, preventing distortion and ensuring clear visibility for the driver without dazzling effects.
Implementation Method 1
a light guide located inside the housing of the display, having an opposite input face and an output face, connected to each other by a side wall, said light guide being configured to, on the one hand, collect at its input face a light radiation coming from outside the housing of the display, and, on the other hand, guide said light radiation to its output face
Implementation Method 2
the side wall of the light guide of the display is shaped so that at least one stray light radiation entering the light guide from an angular area extending beyond an area of interest exits said light guide without reaching the exit face of the light guide
Implementation Method 3
a light sensor, disposed inside said housing, behind the output face of the light guide, adapted to deliver a signal representative of a light intensity which it receives
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention concerns a display (1) comprising: - a housing (10), - inside the housing, a light guide (50) comprising an inlet face and an opposing outlet face, connected by a lateral wall, collecting, at its inlet face, light radiation outside the housing, and guiding the radiation to its outlet face, - behind the outlet face, a light sensor (30) delivering a signal representative of a light intensity that it receives, and, - an image generation unit (20) generating an image. According to the invention, the lateral wall of the light guide is shaped such that stray light radiation entering the light guide from an angular zone extending beyond a zone of interest (Z1) exits the light guide without reaching its outlet face.