Pixel-Shifting Projection Optics for Higher AR Display Resolution
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Solution Overview
Problem
The pixel density of micro-light emitting diode (μLED) and micro-organic light emitting diode (μOLED) displays in augmented reality (AR) eyewear is limited by surface physical processes causing electroluminescence quenching in small volumes, resulting in decreased emission efficiency and limited pixel size, which restricts the achievable resolution and field of view.
Innovation Solution
A polarizing beam splitter (PBS) divides input light into two PBS arms, each synchronized with a pixel shifter and quarter-wave plate, shifting light to create virtual pixels, effectively doubling or quadrupling the perceived display resolution by converting a single pixel into multiple virtual pixels through time-division multiplexing and total internal reflection within a waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is decreased to increase pixel density, then display resolution is improved, but emission efficiency deteriorates due to electroluminescence quenching in small volumes
Solution Approach 1:
The patent segments the light output from a single physical pixel into multiple virtual pixels by introducing optical path differences. A beam splitter divides the light from each pixel into multiple paths, and waveplates create relative phase shifts between these paths. When recombined, these paths interfere constructively and destructively to form multiple virtual pixel positions, effectively segmenting one physical pixel into multiple virtual pixels and achieving higher resolution without reducing physical pixel size
Solution Approach 2:
The patent transitions from spatial resolution enhancement to temporal resolution enhancement by using time-division multiplexing. The system displays different virtual pixel patterns at different time intervals (e.g., alternating between even and odd virtual pixels in successive frames), allowing the human visual system to integrate these temporal patterns into a single high-resolution image. This temporal dimension approach bypasses the physical pixel size limitation
2Measurement precision
If pixel size is decreased to increase pixel density, then display resolution is improved, but field of view is limited by the same physical constraints
Solution Approach 1:
The patent segments the light output from a single physical pixel into multiple virtual pixels by introducing optical path differences. A beam splitter divides the light from each pixel into multiple paths, and waveplates create relative phase shifts between these paths. When recombined, these paths interfere constructively and destructively to form multiple virtual pixel positions, effectively segmenting one physical pixel into multiple virtual pixels and achieving higher resolution without reducing physical pixel size
Solution Approach 2:
The patent transitions from spatial resolution enhancement to temporal resolution enhancement by using time-division multiplexing. The system displays different virtual pixel patterns at different time intervals (e.g., alternating between even and odd virtual pixels in successive frames), allowing the human visual system to integrate these temporal patterns into a single high-resolution image. This temporal dimension approach bypasses the physical pixel size limitation
3Measurement precision
If time-division multiplexing with pixel shifting is implemented, then perceived display resolution is increased, but device complexity increases due to additional optical components
Solution Approach 1:
The patent makes the optical components serve multiple functions. The beam splitter not only divides light paths but also enables the creation of multiple virtual pixels. The waveplates serve both to create phase shifts for virtual pixel formation and to control the polarization state of light. The same optical path is used for both displaying virtual pixels and guiding light through the waveguide, reducing the need for separate component sets
Solution Approach 2:
The patent uses the polarization state of light as a temporary resource that is discarded and recovered in each frame cycle. The system alternates between displaying even and odd virtual pixels by controlling the polarization state and corresponding waveplate orientations. After each virtual pixel pattern is displayed, the polarization state is reset and recovered for the next pattern, allowing efficient time-division multiplexing without permanent polarization component loss
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 preserves the entire intensity of unpolarized input light and provides exceptionally high uniformity of pixel shifting, significantly increasing the perceived display resolution and field of view without reducing light intensity.
Implementation Method 1
A polarizing beam splitter (PBS) divides input light into two PBS arms
Implementation Method 2
total internal reflection within a waveguide
Implementation Method 3
the incoupled light is 'guided' through the substrate, typically by multiple instances of total internal reflection
Data Source
AI summary
A time-division multiplexed projection display is pixel shifted to produce an increased perceived display resolution. A polarizing beam splitter (PBS) divides input unpolarized display light into two orthogonal linear polarizations and directs them to two PBS arms. The PBS arms act to shift the light in synchronization with the time-multiplexed display such that a single pixel of the light engine providing the display light is converted into two or four virtual pixels, effectively increasing the perceived display resolution relative to the native resolution of the light engine. The PBS combines the light from both PBS arms into a single, unpolarized output that may then be projected into a lens or a waveguide incoupler to enable the light to propagate through a waveguide for display at a user's eye.