Projector Array Waveguide Layout for Large Near-Eye Eyebox
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Solution Overview
Problem
Existing near-eye display systems face challenges in providing a large exit pupil (eyebox) while maintaining compact size, high resolution, and efficient light transmission, particularly in augmented reality applications, due to complex and bulky optics and interference issues in two-dimensional exit pupil expansion.
Innovation Solution
A near-eye display system utilizing an array of projectors and a waveguide for one-dimensional exit pupil expansion, where image light is expanded in two dimensions using an input coupler and an output coupler, reducing complexity and interference, and allowing for simpler manufacturing and improved color uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two-dimensional exit pupil expansion is implemented using traditional optics, then a large exit pupil and large field of view are achieved, but the system becomes bulky, complex, and suffers from light efficiency issues and color degradation
Solution Approach 1:
The patent divides the exit pupil expansion into two independent one-dimensional expansions. First, an array of projectors arranged in a first dimension provides expansion in that dimension. Second, a waveguide with input and output couplers provides expansion in a second dimension transverse to the first. This segmentation allows each dimension to be optimized independently, reducing overall system complexity while achieving the desired large exit pupil area.
Solution Approach 2:
The patent transitions from attempting simultaneous two-dimensional expansion using complex optics to a sequential approach where one dimension is handled by the projector array arrangement and the other dimension is handled by the waveguide optics. This dimensional separation simplifies the optical design while achieving the same functional goal of expanding the exit pupil in both dimensions.
2Area of stationary object
If two-dimensional exit pupil expansion is implemented using traditional optics, then a large field of view is achieved, but light efficiency deteriorates and color uniformity degrades
Solution Approach 1:
By segmenting the expansion into two independent one-dimensional processes, each process can be optimized for light efficiency. The projector array arrangement handles expansion in one dimension with minimal optical intervention, while the waveguide handles the other dimension with optimized couplers. This reduces the total number of optical interfaces and potential sources of light loss and color degradation.
Solution Approach 2:
The use of an array of projectors arranged in offset columns creates multiple copies of the image light that are then combined through the waveguide system. This copying approach allows for better light distribution and efficiency compared to single-projector systems that require complex multi-element optics to achieve the same field of view.
3Manufacturing precision
If traditional optics are used for exit pupil expansion, then color uniformity is maintained, but the system size and manufacturing cost increase
Solution Approach 1:
The system segments the optical functions so that the projector array handles color reproduction in one dimension while the waveguide handles expansion in the other dimension. This segmentation allows each component to be manufactured independently with standard processes, reducing overall manufacturing complexity and cost while maintaining color uniformity through the modular architecture.
Solution Approach 2:
The patent changes the arrangement parameters of the projector array (specifically using offset columns) to optimize both the field of view and color uniformity. This parameter optimization allows the system to achieve good color uniformity with simpler optics, reducing manufacturing cost while maintaining precision requirements.
4Weight of moving object
If a compact near-eye display system is designed, then size and weight are reduced, but achieving large exit pupil and field of view becomes more difficult
Solution Approach 1:
The patent segments the exit pupil expansion into two independent one-dimensional expansions handled by different components. The projector array handles one dimension and the waveguide handles the other dimension. This segmentation allows for a more compact integration of components compared to traditional two-dimensional expansion optics, reducing overall system size and weight while achieving the desired large exit pupil area.
Solution Approach 2:
By using the waveguide to handle expansion in the second dimension transverse to the first dimension, the system achieves compact integration. The waveguide can be integrated close to the projector array, allowing for a compact overall system that maintains a large exit pupil without requiring bulky optical components.
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 system achieves a larger eyebox with reduced complexity, cost, and weight, while maintaining high color uniformity and efficiency, suitable for augmented reality applications.
Implementation Method 1
The input coupler couples the image light from the array of projectors into a TIR path within the waveguide
Implementation Method 2
Different optical elements, including diffractive and reflective optics, may be implemented as the output coupler
Implementation Method 3
Different optical elements, including diffractive and reflective optics, may be implemented as the output coupler
Data Source
AI summary
The present disclosure describes near-eye display systems including an array of projectors and a one-dimensional exit pupil expander. The array of projectors can be arranged along a first dimension and can output image light towards an input coupler within a waveguide that provides one-dimensional exit pupil expansion. In some implementations, arrays of monochromatic projectors are implemented and arranged in offset columns. The input coupler in-couples the image light from the array of projectors into a TIR path within the waveguide. Different optical elements, including diffractive and reflective optics, may be implemented as the input coupler. The image light travels within the waveguide until it interacts with an output coupler. Upon interaction with the output coupler, the image light is expanded in a second dimension transverse to the first dimension and is coupled out of the waveguide.