SLM Pixel Resampling for Wider Eyeboxes and Reduced Artifacts
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Solution Overview
Problem
Existing image forming systems, such as holographic displays, suffer from undesirable higher diffraction orders that cause visual artifacts and limit the size of the eyebox, which is the region where a human eye pupil can receive image light, especially when a large field-of-view is desired.
Innovation Solution
The system employs a spatial light modulator (SLM) with a resampling layer that subsamples each pixel with two or more samples per pixel, increasing the spacing between diffraction orders and forming multiple exit pupils, while using a blurring layer to mitigate intensity loss and visual aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a spatial light modulator uses conventional pixel sampling, then the device complexity is reduced, but higher diffraction orders cause visual artifacts and limit the eyebox size
Solution Approach 1:
The patent divides each pixel into multiple subsamples (e.g., 2x2 grid of 4 samples per pixel), creating a resampled pixel structure. This segmentation of pixels into multiple sampling points allows the system to control diffraction orders more precisely while managing complexity through structured subdivision rather than simple pixel multiplication
Solution Approach 2:
The patent introduces an additional sampling dimension by creating multiple discrete samples within each pixel's spatial footprint. This dimensional expansion from single-point pixel sampling to multi-point subsampling enables better control over diffraction pattern spacing without proportionally increasing overall device complexity
2Area of stationary object
If the spacing between diffraction orders is increased to expand eyebox, then the eyebox size increases, but intensity loss and visual aberrations occur
Solution Approach 1:
The patent introduces a blurring layer as an intermediary element between the resampled pixel structure and the final diffraction pattern. This blurring layer acts as a mediator that smooths transitions and reduces abrupt intensity variations, thereby maintaining intensity levels while preserving the expanded eyebox effect from increased diffraction order spacing
Solution Approach 2:
The patent modifies the optical parameters of the system by introducing controlled blurring that changes the point spread function. This parameter change in the optical transfer function allows the system to maintain adequate intensity in higher diffraction orders while achieving increased spacing between them, thus expanding the eyebox without significant intensity loss
3Area of stationary object
If multiple exit pupils are formed to increase eyebox, then the eyebox size increases, but multiple images may align with the human eye pupil causing visual artifacts
Solution Approach 1:
The patent applies different sampling strategies to different regions of the spatial light modulator. By creating multiple discrete samples within each pixel's local region and controlling their phase relationships, the system ensures that only one exit pupil aligns with the human eye pupil at a time, preventing multiple image alignment while maintaining expanded eyebox coverage
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 enhances the size of the eyebox by ensuring only one exit pupil aligns with the human eye pupil at a time, reducing visual artifacts and increasing brightness of higher diffraction orders, thus improving the viewing experience.
Implementation Method 1
a plurality of pixels configured to diffract incident light and to cause the diffracted light to exit the spatial light modulator
Implementation Method 2
a resampling layer configured to interact with the incident light to subsample each of the plurality of pixels with two or more discrete samples of the incident light per pixel at respective positions on the pixel, to affect an angle of each diffraction order of light exiting the spatial light modulator
Data Source
Figure 1
Figure 2A~2B
Figure 2C~3
AI summary
An image forming system includes a spatial light modulator (SLM) including a plurality of pixels. Each pixel is configured to diffract incident light and cause the diffracted light to exit the SLM, where a first diffraction order of light exiting the SLM passes through a first exit pupil and higher diffraction orders of light exiting the SLM pass through additional exit pupils having different positions from the first exit pupil. Control logic operatively coupled to the plurality of pixels is configured to control each pixel to control its modulation of the light incident on the pixel and cause the plurality of pixels to collectively form an image at each exit pupil. A light source is configured to emit incident light toward the SLM. A resampling layer is configured to subsample each pixel electrode with two or more samples per pixel to increase a spacing between each exit pupil.