Holographic Waveguide Output Uniformity via Hologram Pre-Compensation
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Solution Overview
Problem
Conventional holographic projectors rely on complex dielectric stacks to moderate waveguide emissions, which are difficult to manufacture over a broadband of wavelengths, and require a complex graded coating to compensate for intensity loss in waveguide emissions.
Innovation Solution
A projection system using a hologram engine and waveguide with partially reflective-transmissive surfaces that angularly distribute light to compensate for intensity loss, eliminating the need for complex coatings by leveraging the hologram's spatial domain distribution of image content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex dielectric stacks are used to moderate waveguide emissions, then emission control is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the emission control function from the complex dielectric stack and relocates it to the hologram pattern. By encoding intensity compensation information directly into the hologram, the system eliminates the need for complex graded coatings on the waveguide, thereby reducing manufacturing complexity while maintaining emission control
Solution Approach 2:
The hologram acts as an intermediary that mediates between the light source and the waveguide emission. It pre-processes the light intensity distribution according to the expected propagation losses, so that the waveguide can use a simple uniform coating instead of a complex graded coating to achieve uniform emission intensity
2Illumination intensity
If complex graded coatings are applied to compensate for intensity loss, then emission uniformity is improved, but manufacturing difficulty increases
Solution Approach 1:
The system performs preliminary action by encoding the intensity compensation pattern into the hologram before light enters the waveguide. This pre-compensation approach eliminates the need for complex graded coatings, making manufacturing easier while achieving uniform emission intensity across all emission zones
Solution Approach 2:
The patent changes the parameter distribution in the hologram pattern to compensate for the exponential intensity loss in the waveguide. By modifying the amplitude and/or phase parameters of the hologram pixels, the system achieves uniform emission intensity without requiring complex graded coatings
3Ease of manufacture
If simple uniform coatings are used on waveguide surfaces, then manufacturing ease is improved, but emission uniformity deteriorates due to intensity loss
Solution Approach 1:
The system uses a feedback approach where the hologram pattern is calculated based on the known intensity loss characteristics of the waveguide. The hologram compensates for the expected intensity decay, enabling simple uniform coatings to produce uniform emission by pre-balancing the intensity distribution
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 allows for efficient waveguiding of holographic light without the need for complex coatings, reducing manufacturing complexity and enabling high-quality image reproduction across a broad spectrum.
Implementation Method 1
The display device is arranged to display a hologram of an image and spatially modulate light in accordance with the displayed hologram to form a holographic wavefront
Implementation Method 2
The waveguide comprising a pair of parallel reflective surfaces arranged to waveguide the holographic wavefront therebetween. A first surface of the pair of parallel reflective surfaces is partially reflective-transmissive
Data Source
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AI summary
A projection system comprising a display device, a hologram engine and a waveguide. The display device is arranged to display a hologram of an image and spatially modulate light in accordance with the hologram to form a holographic wavefront. The hologram engine is arranged to calculate the hologram. The hologram is arranged to angularly distribute light within the holographic wavefront in accordance with spatial position within the image such that continuous angular ranges of the holographic wavefront respectively correspond with continuous regions of the image. The waveguide comprising a pair of parallel reflective surfaces arranged to waveguide the holographic wavefront therebetween. A first surface of the pair of parallel reflective surfaces is partially reflective-transmissive so as to form an output comprising a plurality of emission zones for the holographic wavefront. The hologram engine is arranged to modify the hologram to at least partially compensate for a decrease in intensity of the emission from each successive emission zone of the waveguide caused by the partial reflection-transmissions at the first surface during waveguiding.