Light Guide Element With Polarization Separation for Ghost Reduction
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Solution Overview
Problem
Existing image display apparatuses suffer from low light utilization efficiency due to unnecessary light, such as ghosts, caused by unequal reflectance of P-polarized and S-polarized light.
Innovation Solution
A light guide element with a separating portion having multiple separating surfaces with different spectral reflectances, and an emitting portion with dielectric films, designed to optimize the separation and emission of light towards the pupil, ensuring balanced reflectance for both polarizations and enhancing light utilization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light guide plate is used to guide light to the pupil, then light guidance function is achieved, but light utilization efficiency decreases due to unnecessary light
Solution Approach 1:
The light guide plate is divided into functionally distinct regions: an entrance portion for light input, a separating portion with multiple separating surfaces to divide light into P-polarized and S-polarized components, and an emitting portion for light output. This segmentation allows each region to perform its specific function optimally, separating useful light from unnecessary light to improve light utilization efficiency.
Solution Approach 2:
Different portions of the light guide plate are assigned different optical properties. The separating portion has surfaces with specific spectral reflectances designed to selectively reflect P-polarized light while transmitting S-polarized light. The emitting portion has optimized surface characteristics for efficient light extraction toward the pupil. This local differentiation of optical properties enables precise control over light propagation and reduces unnecessary light.
2Productivity
If separating surfaces with different spectral reflectances are used, then light separation efficiency is improved, but device complexity increases
Solution Approach 1:
Multiple separating surfaces with different spectral reflectances are integrated into a single light guide plate structure. The first, second, and third separating surfaces are formed within the same component, combining multiple light separation functions into one element. This merging approach achieves efficient light separation while avoiding the complexity of assembling multiple separate components.
Solution Approach 2:
The light guide plate employs composite optical structures with surfaces having different spectral reflectance characteristics. By integrating multiple separating surfaces with varying optical properties into a single component, the design achieves sophisticated light separation functionality without proportionally increasing structural complexity.
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 design achieves high light utilization efficiency by condensing light effectively on the pupil, reducing unnecessary light, and maintaining uniform illuminance, thereby improving image quality.
Implementation Method 1
the separating portion has a first separating surface, a second separating surface, and a third separating surface... Re(α, n, S) is a reflectance [%] to S-polarized light... Re(α, n, P) is a reflectance [%] to P-polarized light
Implementation Method 2
a dielectric film including a plurality of layers... spectral reflectances different from each other
Data Source
AI summary
A light guide element is configured to guide light from a display element to a pupil and includes an entrance portion which the light is to enter, a separating portion configured to separate the light in a first direction, and an emitting portion configured to emit the light toward the pupil. The separating portion has a plurality of separating surfaces with spectral reflectances different from each other. The plurality of separating surfaces include a dielectric film including a plurality of layers.