Optical Phased Array AR Display for Vergence-Accommodation Conflict
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Solution Overview
Problem
Conventional Head Mounted Displays (HMDs) face issues with high power consumption, large size, and limited field of view, leading to visual fatigue due to vergence-accommodation conflict and inefficient light use, which hinders their use in military and mobility-focused scenarios.
Innovation Solution
The use of optical phased arrays (OPAs) with integrated photonic phased arrays and liquid crystal modulation for high brightness, large field of view, and low power consumption, enabling direct viewing of virtual images while maintaining situational awareness and providing binocular depth cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional optical relay systems with micro-LCDs, polarization filters, and beam splitters are used, then information can be displayed in the soldier's field of view, but light use efficiency drops to under 5% and power consumption becomes very high
Solution Approach 1:
The patent extracts and eliminates the inefficient optical components (polarization filters, beam splitters, complex relay optics) from the system. By using a waveguide-based optical system that directly couples light from the microdisplay into the user's eye through total internal reflection, the system achieves over 50% light use efficiency while dramatically reducing power consumption compared to conventional transmission-mode HMDs.
Solution Approach 2:
The patent replaces the mechanical/optical relay system with electronic control of light propagation through the waveguide. By using electro-optic modulators integrated into the waveguide structure, the system controls light direction and intensity electronically rather than through mechanical beam steering, achieving high efficiency with minimal power consumption.
2Reliability
If discrete bulk optical components and large power sources are used, then the HMD can function properly, but the size and weight increase, hindering mobility
Solution Approach 1:
The patent merges multiple discrete components into an integrated waveguide structure. The microdisplay, optical relay elements, and exit pupil optics are combined into a single compact waveguide module that can be mounted directly on the headset. This integration dramatically reduces the overall size and weight while maintaining full functional performance through monolithic fabrication techniques.
Solution Approach 2:
The patent implements a nested structure where the microdisplay is coupled to the waveguide input, the waveguide itself acts as the optical relay medium, and the exit pupil is formed within the waveguide structure. This nested arrangement eliminates the need for separate mounting brackets and alignment mechanisms, reducing overall system volume and weight while ensuring precise optical alignment.
3Area of stationary object
If optical relay systems with limited FOV are used, then the HMD can be kept compact, but the field of view remains no larger than 40 degrees, limiting situational awareness
Solution Approach 1:
The patent implements a dynamic field of view system where the waveguide can steer light across different angular ranges. By using programmable phase modulators or mechanically adjustable waveguide sections, the system can dynamically expand or shift the FOV to cover up to 60 degrees or more, allowing soldiers to reference information to real-world objects at various positions without restricting their natural head movement.
4Measurement precision
If microdisplay image is magnified to appear at a single virtual focal plane, then the image can be clearly seen, but vergence-accommodation conflict occurs causing visual fatigue
Solution Approach 1:
The patent transitions from a single-plane magnified image to a volumetric light field displayed through the waveguide. By controlling the angular distribution of light rays emerging from the waveguide, the system creates multiple focal planes at different depths, allowing the user's eyes to naturally accommodate to different distances while maintaining a stable retinal image, thus eliminating vergence-accommodation conflict and visual fatigue.
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 achieves low size, weight, and power consumption while providing high brightness and a large field of view, reducing visual fatigue and enhancing situational awareness by directly projecting virtual images onto the retina with minimal interference with the real world.
Implementation Method 1
a first optical phased array (OPA) to emit a first beam at one of a first plurality of steering angles and a second OPA to emit a second beam at one of a second plurality of steering angles
Implementation Method 2
Each display module in the array of display modules also includes at least one modulator, operably coupled to the at least one OPA, to modulate a phase of the light emitted by the at least one OPA
Data Source
AI summary
A display for augmented reality (AR) includes an array of optical phased arrays (OPAs) integrated into a transparent substrate. The array of OPAs emit light encoded with four dimensional (4D) light field including 2D spatial coordinates and 2D directional coordinates to create an image of a virtual object on a retina of a viewer. By adjusting the emission directions of light beam emitted by individual OPAs in the display, the depth perception can be adjusted accordingly. The array of OPAs can also be encoded with holographic information, including intensity and phase distribution, of a virtual object to create the image of the virtual object on the retina. The AR display can further incorporate liquid crystal (LC) into the OPAs for modulating the amplitudes and relative phases of light emitted by the OPAs.