Light Redirecting Layer for Head-Mounted Display Brightness
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Solution Overview
Problem
Conventional display systems face challenges in maximizing the fraction of light emitted by the display panel that is transmitted through the exit pupil, particularly in achieving a wide field of view in compact systems like head-mounted displays, due to limitations in light output direction and collimation.
Innovation Solution
Incorporating a light redirecting layer between the display panel and the partial reflector, or modifying the backlight to include a partially collimating component, which alters the light output to increase the fraction of light transmitted through the exit pupil by adjusting the direction and collimation of the light emitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional display panel is used without light redirecting elements, then the system structure is simple, but the fraction of light transmitted through the exit pupil is limited and the field of view is narrow
Solution Approach 1:
The display panel is divided into individual pixels, and light redirecting elements are assigned to specific groups of pixels rather than covering the entire panel uniformly. This segmentation allows selective light redirection where needed while maintaining system simplicity elsewhere
Solution Approach 2:
Light redirecting elements are introduced as intermediary components between the display panel and the exit pupil. These elements mediate the light path by redirecting and collimating light from specific pixel groups, increasing the fraction of light transmitted through the exit pupil without requiring complete system redesign
2Adaptability or versatility
If light redirecting elements are added to increase light transmission, then brightness and field of view improve, but the device complexity increases
Solution Approach 1:
Light redirecting elements are applied locally to specific groups of pixels rather than uniformly across the entire display panel. Each light redirecting element is positioned and configured to handle light from its associated pixel group, providing localized light redirection that expands the field of view while minimizing overall system complexity
Solution Approach 2:
Instead of implementing light redirection across the entire display panel, the invention applies light redirecting elements to only certain groups of pixels. This partial action approach achieves the desired field of view expansion and brightness improvement without the complexity of a complete light redirection system
3Productivity
If the light output direction is not adjusted, then the optical system is simple, but the fraction of light transmitted through the exit pupil is limited
Solution Approach 1:
A light redirecting layer is introduced as an intermediary component between the display panel and the exit pupil. This layer contains light redirecting elements that actively modify the light output direction from specific pixel groups, thereby increasing the fraction of light transmitted through the exit pupil without requiring complete redesign of the optical system
Solution Approach 2:
The light redirecting layer is segmented into discrete light redirecting elements, each associated with specific groups of pixels. This segmentation allows the system to achieve improved light transmission efficiency by redirecting light only where necessary, rather than requiring a complex omnidirectional light redirection system
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 approach significantly enhances the brightness and contrast ratio at the exit pupil, providing a wider field of view and improved image quality in compact display systems, such as virtual reality displays, by increasing the total luminous energy and brightness by at least 30% compared to equivalent systems without the light redirecting layer.
Implementation Method 1
Each light redirecting element corresponding to a different pixel in the plurality of pixels and receives a first diverging light emitted by the pixel having a first cone angle and transmits the received light as a second diverging light having a second cone angle
Implementation Method 2
a concave light redirecting surface concave toward the light source is provided. The light source includes a plurality of groups of discrete spaced apart pixels. Each different portion of the light redirecting surface corresponds to a different group of pixels
Data Source
AI summary
Light emitting systems and optical systems including a light emitting system and a lens system are described. The light emitting system includes a pixelated light source having a plurality of discrete spaced apart pixels, and includes a plurality of light redirecting elements, each light redirecting element corresponding to a different pixel in the plurality of pixels. The light redirecting elements may be adapted to alter one or both of a central ray direction and a divergence angle of light received from the corresponding pixel. A lens system disposed to receive light from the light emitting system may include a reflective polarizer and a partial reflector.