Light Guide Prism Layout for Narrow-Angle Virtual Image Projection
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Solution Overview
Problem
Existing optical systems for head-up displays in vehicles face challenges in achieving high light extraction efficiency while maintaining a narrow viewing angle and high light intensity, particularly due to issues with light leakage and the need for additional optical elements.
Innovation Solution
The optical system incorporates a light guide member with a prism structure that reflects light towards an emergent surface, along with a light control member that narrows the divergence angle of light, allowing most light to be directly reflected and emitted without repeated total reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional optical systems use multiple total reflections to guide light, then light can be directed to the emergent surface, but light extraction efficiency decreases and light leakage occurs
Solution Approach 1:
The optical system pre-conditions light rays at the incident surface by selecting only those rays that satisfy the emergence condition (rays that can directly reach the emergent surface without total reflection). This preliminary selection prevents light leakage and maximizes extraction efficiency by ensuring only suitable rays enter the light guide member.
Solution Approach 2:
The invention extracts and eliminates the problematic multiple total reflection pathway from the optical system. By using a prism structure that enables direct reflection and emergence, the system removes the need for repeated total reflections, thereby preventing light leakage and improving extraction efficiency.
2Ease of operation
If additional optical elements are added to control light direction, then viewing angle can be narrowed, but device complexity increases
Solution Approach 1:
The incident surface serves multiple functions: it acts as both the entry point for light and the control element for selecting emergence-eligible rays. This multi-functionality narrows the viewing angle without requiring separate control elements, thereby maintaining simplicity while achieving precise angular control.
Solution Approach 2:
The invention merges the light entry function and the viewing angle control function into a single integrated incident surface structure. This consolidation eliminates the need for additional optical elements while achieving narrow viewing angle control through the geometric selection of emergence-eligible rays.
3Illumination intensity
If light undergoes multiple total reflections, then light can be guided through the system, but light intensity decreases due to losses
Solution Approach 1:
The optical system ensures continuous and direct light propagation from the incident surface to the emergent surface through emergence-eligible rays. This continuous pathway without interruptions or multiple reflections maintains light intensity and maximizes guidance efficiency by eliminating loss points.
Solution Approach 2:
The invention converts the potential harm of light leakage and intensity loss into benefit by using the prism structure to directly reflect and emerge light in a single step. This approach transforms what would be lossy multiple reflections into an efficient direct pathway, thereby maintaining high light intensity.
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 enhances light extraction efficiency, reduces light leakage, and eliminates the need for additional optical elements, thereby achieving a narrower viewing angle and higher light intensity suitable for head-up displays.
Implementation Method 1
The prism is provided for the first surface and reflects, toward the second surface, the light passing inside the light guide member
Data Source
AI summary
An optical system includes a light guide member having an incident surface, a first surface and a light emergent surface; and at least one prism provided on the first surface and configured to reflect light received by the incident surface and travelling inside the light guide member, towards the light emergent surface. The light guide member provides an optical path along which the light that has entered through the incident surface is directly reflected from the prism and allowed to emerge from the light emergent surface. The light guide member also provides another optical path along which the light that has entered through the incident surface is once reflected from the second surface, reflected again from the prism, and then allowed to emerge from the light emergent surface. The optical system is configured to be coupled to a light source, to illuminate a display system which projects a virtual image onto a target space.