Light Engine Hologram Channels for Compact Wide-Field Projection
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Solution Overview
Problem
Existing image projection systems, such as head-up displays, face limitations in expanding the range of angles of light rays that can propagate through an eye's pupil, leading to a restricted field of view and sensitivity to eye position, particularly in systems with a small display device and large projection distance.
Innovation Solution
A light engine comprising a display device, a hologram replicator, and a control device that angularly distributes spatially modulated light according to image content, using waveguide pupil expanders to increase the range of angles and reduce stray light, allowing for a larger viewing area and efficient propagation of holograms or images to the viewer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small display device is used with large projection distance, then the system becomes more compact and suitable for head-up displays, but the range of angles of light rays that can propagate through the eye's pupil is restricted
Solution Approach 1:
The patent divides the light field into multiple angular channels using a hologram that angularly distributes spatially modulated light. Each angular channel corresponds to a specific viewing angle, allowing the system to expand the effective viewing angle range without increasing the physical display device size. This segmentation of the light field by angle resolves the contradiction between compact system size and expanded viewing adaptability.
Solution Approach 2:
The patent introduces angular distribution as an additional dimension for light organization. By using a hologram to angularly distribute light according to image content, the system effectively adds an angular dimension to the light propagation paths. This allows multiple viewing angles to be accommodated within the same physical space, resolving the contradiction between compact size and viewing angle range.
2Area of stationary object
If the display device aperture is limited, then the system remains compact, but the exit pupil is restricted leading to sensitivity to eye position
Solution Approach 1:
The patent introduces a waveguide pupil expander as an intermediary component between the display device and the viewer's eye. This waveguide receives the limited light from the small display aperture and expands it into a larger exit pupil. The waveguide acts as a mediator that transforms the restricted input pupil into an expanded output pupil, reducing sensitivity to eye position while maintaining the compact display device aperture.
Solution Approach 2:
The patent changes the spatial parameters of the light field by expanding the exit pupil area using the waveguide. This parameter transformation allows the system to maintain a small display device aperture while achieving a larger effective exit pupil that is less sensitive to eye position variations. The waveguide effectively transforms the aperture parameter from the input side to the output side.
3Adaptability or versatility
If waveguide pupil expanders are used to expand the exit pupil, then the viewing area increases and eye position sensitivity is reduced, but the system complexity increases
Solution Approach 1:
The patent integrates multiple functions into the waveguide pupil expander, which simultaneously performs pupil expansion, angular channel separation, and stray light reduction. By combining these functions into a single component, the patent reduces the overall system complexity that would otherwise result from adding separate components for each function. This multi-functionality approach resolves the contradiction between expanded viewing adaptability and system complexity.
Solution Approach 2:
The patent merges the hologram, waveguide, and angular distribution mechanisms into an integrated optical system. By combining these elements that work together to expand the viewing area and reduce eye position sensitivity, the system achieves the desired adaptability without the complexity of separate, independently controlled components. The integration of these elements resolves the contradiction between enhanced viewing area and system complexity.
4Adaptability or versatility
If angular channels are used to distribute light according to image content, then the field of view is expanded, but stray light and ghost images increase
Solution Approach 1:
The patent extracts and separates stray light from the main angular channels using the waveguide structure. By designing the waveguide to guide only the desired angular channels while excluding stray light paths, the system maintains the expanded field of view provided by angular channel distribution while removing the harmful stray light effect. This extraction of unwanted light resolves the contradiction between expanded field of view and stray light reduction.
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 viewing area and reduces ghost images, enabling efficient and compact image projection systems with improved eye-box movement and reduced complexity, suitable for applications like automotive head-up displays.
Implementation Method 1
guiding light from its input port to a respective output port by internal reflection between a pair of parallel surfaces
Implementation Method 2
a diffractive structure arranged to spatially modulate light in accordance with the hologram, wherein the diffractive structure is arranged to angularly distribute spatially modulated light of the image
Data Source
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AI summary
A light engine is disclosed, the light engine arranged to form an image visible from a viewing window. The light engine comprises: a display device arranged to display a hologram of the image and spatially modulate light in accordance with the hologram, wherein the hologram is configured to angularly distribute spatially modulated light of the image in accordance with position of image content, such that angular channels of the spatially modulated light correspond with respective continuous regions of the image; a hologram replicator arranged to receive the spatially modulated light and provide a plurality of different light propagation paths for the spatially modulated light from the display device to the viewing window, the hologram replicator comprising a first replicator and a second replicator; and a control device disposed in an optical path between the first replicator and the second replicator, wherein the control device comprises an array of cells arranged such that a first viewing position within the viewing window receives a first channel of light spatially modulated by the hologram in accordance with a first region of the image and a second viewing position within the viewing window receives a second channel of light spatially modulated by the hologram in accordance with a second region of the image. The control device is angled such that light from the first replicator is incident at an acute angle on the control device, and each cell of the array is switchable between a first state and a second state, wherein in each cell in the first state light is relayed to be coupled into the second replicator and in each cell in the second state light remains uncoupled into the second replicator.