Destructive Interference Structure for Head Mounted Display Ghost Image Reduction
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Solution Overview
Problem
Head mounted display devices face challenges in reducing reflectance and improving display quality, particularly in providing clear images without ghost images and increasing light efficiency, which existing technologies have not adequately addressed.
Innovation Solution
The display module incorporates a destructive interference structure with a phase control layer and a reflection preventing layer, along with a phase compensating layer and a thin film encapsulating layer, to adjust optical distances and refractive indices, causing destructive interference and reducing reflectance while enhancing light efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional display structure without destructive interference is used, then the structure is simple, but reflectance is high causing ghost images and reduced display quality
Solution Approach 1:
The patent applies destructive interference to convert the harmful reflected light into beneficial cancellation. By designing the phase control layer and reflection preventing layer to create a phase difference of 160° to 200° between reflected light beams, the patent transforms the harmful ghost images caused by reflection into a benefit where the reflected light is destructively interfered and eliminated, thereby reducing overall reflectance and improving display quality
Solution Approach 2:
The patent changes the optical parameters of the display structure by introducing a phase control layer with specific optical thickness and refractive index. The optical thickness is precisely controlled to create the required phase difference, and the refractive index is selected to optimize the destructive interference effect. This parameter change transforms the conventional reflective structure into one that actively cancels reflections through controlled optical path differences
2Productivity
If light efficiency is increased by reducing reflectance, then display quality improves, but more complex optical control mechanisms are required
Solution Approach 1:
The patent merges the phase control function and reflection prevention function into a unified optical structure. The phase control layer and reflection preventing layer work together as an integrated system where the phase control layer simultaneously manages both the phase of reflected light and the overall reflection control, rather than requiring separate mechanisms for each function. This merging achieves improved light efficiency while limiting the increase in complexity
Solution Approach 2:
The phase control layer acts as an intermediary between the reflection preventing layer and the external environment. It mediates the optical interaction by controlling the phase of light before it reaches the reflection preventing layer, thereby enabling destructive interference to occur. This intermediary approach allows for sophisticated optical control through a single intermediate layer rather than requiring multiple complex control mechanisms
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 effectively reduces ghost images and increases light efficiency, providing clearer images with reduced reflectance and improved display quality in head mounted display devices.
Implementation Method 1
The phase control layer adjusts an optical distance between the second electrode and the reflection preventing layer such that a phase difference between a first light beam reflected from the optical lens and then from the second electrode, and a second light beam reflected image from the optical lens and then from the reflection preventing layer is 160° to 200° to cause destructive interference
Data Source
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Figure 1B
Figure 1C
AI summary
Provided is a head mounted display device including a housing for providing a darkroom space, a display module in the housing and to display an image, and an optical lens for expanding the image to provide the image to a user. The display module includes a destructive interference structure which removes the image reflected from the optical lens without reflecting the image again.