Backlight Unit with Folded Optical Path for Head-Up Display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional backlight units for head-up display devices experience temperature rise issues due to increased luminous flux and illuminance on liquid crystal panels, leading to potential overheating and reduced performance.
Innovation Solution
A backlight unit design incorporating a light source, a light collecting member, an optical member with micromirrors or microlenses, a polarizing plate, and a diffusing plate, where the polarizing plate transmits light orthogonal to the liquid crystal display element's oscillating direction and reflects light intersecting this direction, effectively reducing heat accumulation by managing light paths and illuminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If total luminous flux and illuminance on liquid crystal panel are increased, then display luminance and eye box are improved, but temperature rise of liquid crystal panel increases
Solution Approach 1:
The backlight unit divides light into multiple independent optical paths using a lens array with multiple lenses. Each lens focuses light onto a corresponding microlens on the liquid crystal panel, creating separate illumination zones. This segmentation allows controlled light distribution that reduces overall heat accumulation while maintaining display luminance through optimized light paths.
Solution Approach 2:
A microlens array is introduced as an intermediary component between the lens array and the liquid crystal panel. The microlenses further divide and redirect light onto specific regions of the panel, acting as a mediator that controls light distribution and reduces direct high-intensity illumination that causes temperature rise.
2Length of stationary object
If backlight unit length in depth direction is shortened, then device compactness is improved, but optical path folding complexity increases
Solution Approach 1:
The optical path is folded back using a reflecting surface that redirects light from the light source in a different spatial dimension. Instead of extending the optical path linearly in the depth direction, the reflector changes the light's propagation direction, allowing the path to loop back and reducing the overall unit length while maintaining optical functionality.
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 suppresses temperature rise in liquid crystal panels, enhances light transmittance, and maintains equivalent display luminance, allowing for larger display angles and reduced overheating, while also downsizing the backlight unit.
Implementation Method 1
a light collecting member that collects light emitted from the light source
Implementation Method 2
an optical member that includes a concave reflecting surface and reflects light entering from the light collecting member toward a light transmissive liquid crystal display element by the reflecting surface
Implementation Method 3
a polarizing plate that is disposed at a position where an optical path between the optical member and the liquid crystal display element is folded back, transmits part of light reflected by the optical member, and reflects the rest of the light toward the liquid crystal display element
Implementation Method 4
a diffusing plate disposed on an optical path between the polarizing plate and the liquid crystal display element
Data Source
AI summary
A backlight unit has a light source, a light collecting member that collects light emitted from the light source, and a micromirror array that has a concave reflecting surface and reflects light entering from the light collecting member toward a liquid crystal panel by the reflecting surface, a polarizing plate that folds back, between the micromirror array and the liquid crystal panel, an optical path of light reflected by the micromirror array toward the liquid crystal panel, and a diffusing plate disposed on an optical path between the polarizing plate and the liquid crystal panel. In the micromirror array, the reflecting surface is composed of a plurality of micromirrors. The polarizing plate transmits light oscillating in a first direction orthogonal to an oscillating direction of light transmitted through the liquid crystal panel and reflects light oscillating in a second direction intersecting the first direction.