Diffractive Optics Masking Screen Door Effect in VR Headsets
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Solution Overview
Problem
Virtual reality headsets experience increased fixed pattern noise, known as the 'screen door effect,' due to magnification of pixel boundaries, which degrades image quality by making dark spaces between sub-pixels visible to the user.
Innovation Solution
Incorporating a corrective optics block with a diffractive surface, such as a Fresnel or binary surface, that blurs light from sub-pixels to mask the dark spaces between them, thereby reducing the screen door effect, and using software corrections for two-dimensional optical errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnification is increased to improve display resolution, then image clarity is improved, but fixed pattern noise (screen door effect) increases
Solution Approach 1:
A diffractive optical element is introduced as an intermediary component between the display and the user's eye. This element creates a blur kernel that convolves with the displayed image, smoothing the transitions between sub-pixels and masking the dark spaces that cause the screen door effect, while preserving the magnified resolution benefits.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a diffractive surface with specific groove patterns. This modifies the point spread function of the optical system to create controlled blur that masks fixed pattern noise while maintaining the magnified image quality.
2Object-generated harmful factors
If a corrective optics block is added to reduce fixed pattern noise, then screen door effect is reduced, but device complexity increases
Solution Approach 1:
The patent combines multiple optical functions into a single diffractive optical element. This element simultaneously provides magnification, corrects optical aberrations, and reduces fixed pattern noise through its diffractive blur kernel, eliminating the need for separate corrective optics blocks and reducing overall device complexity.
Solution Approach 2:
The diffractive optical element serves multiple functions: it acts as a magnifying lens, corrects optical aberrations including fixed pattern noise, and creates the necessary blur kernel. This multi-functionality reduces the number of separate components needed in the optical 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
The solution effectively reduces the visibility of pixel boundaries, enhancing image quality by blurring sub-pixels to mask dark spaces, thus minimizing the screen door effect and improving the overall display experience in virtual reality headsets.
Implementation Method 1
at least a portion of the optical element is a diffractive surface configured to blur light from the sub-pixels
Data Source
AI summary
A virtual reality (VR) headset includes an electronic display element and a corrective optics block. The electronic display element outputs image light via a plurality of sub-pixels of different colors that are separated from each other by a dark space. The corrective optics block includes an optical element including a diffractive surface. The corrective optics block is configured to magnify the image light and generate optically corrected image light by using the diffractive surface to generate blur spots of each sub-pixel masking dark space between adjacent sub-pixels. Optically corrected light is directed form the corrective optics block to an exit pupil of the VR headset for presentation to a user.