Diffractive Structure Spatial Modulation for Ghost Image Suppression
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Solution Overview
Problem
Conventional optical systems with small display devices face limitations in field of view and image visibility due to large viewing distances, often resulting in restricted visibility and the formation of ghost images, especially when using waveguides for pupil expansion.
Innovation Solution
A method for determining a diffractive structure, such as a hologram, that spatially modulates light to maximize the field of view by identifying contributory and non-contributory areas of the display device, and using a pupil expander to direct light channels through the entrance aperture of the viewing system, thereby eliminating or modifying ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small display device is used in conventional optical systems, then the device size is reduced, but the field of view and image visibility are restricted due to large viewing distances
Solution Approach 1:
The patent transforms the 2D display device into a 3D volumetric light field using a diffractive structure. By encoding phase and amplitude information in the hologram, the system creates multiple light propagation paths that expand the effective viewing volume, allowing a small display device to provide a large field of view through optical dimensionality expansion.
Solution Approach 2:
The patent introduces a diffractive structure (hologram) as an intermediary between the small display device and the viewer's eye. This intermediary modulates light to create virtual images at different depths and positions, effectively bridging the gap between the small physical display and the required large viewing area.
2Adaptability or versatility
If waveguides are used for pupil expansion, then the field of view is expanded, but ghost images are formed
Solution Approach 1:
The patent extracts and eliminates the harmful ghost image components from the optical system. By carefully designing the diffractive structure to control light propagation paths, the system separates the desired primary image light from the unwanted ghost image light, effectively removing the harmful factor while preserving the field of view expansion benefit.
Solution Approach 2:
The patent applies different optical properties to different regions of the diffractive structure. By varying the local diffraction characteristics across the hologram, the system directs light from different display regions to specific viewing zones, ensuring that only the primary image reaches the viewer while ghost images are suppressed in critical viewing areas.
3Loss of information
If light is scattered from an object to form a hologram, then amplitude and phase information is captured, but the hologram reconstruction requires precise illumination conditions
Solution Approach 1:
The patent performs preliminary encoding of the light field information into a diffractive structure during the hologram creation phase. By pre-calculating and embedding the phase and amplitude relationships in the hologram pattern, the system ensures that reconstruction occurs reliably under the designed illumination conditions without requiring complex real-time adjustments.
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 enhances the field of view and image quality by ensuring that all image content reaches the viewer, reducing ghost images and allowing for accurate, sharp image projection even with small display devices and large viewing distances.
Implementation Method 1
A diffractive structure, arranged to spatially modulate light transformable by a viewing system into a target image, wherein the diffractive structure is configured to route light into a plurality of hologram channels, each hologram channel corresponding to a different part of the target image
Implementation Method 2
a waveguide arranged to receive the spatially modulated light from the diffractive structure and provide a plurality of different light propagation paths for the spatially modulated light from the display device to the entrance pupil
Data Source
AI summary
A diffractive structure arranged to spatially modulate light transformable by a viewing system into a target image. The diffractive structure is configured to generate a plurality of discrete light patterns. Each light pattern corresponds to a different part of the target image. The shape of each discrete light pattern substantially corresponds to the shape of an entrance aperture of the viewing system.