Display Diffractive Waveguide Expansion with Prism Dispersion Compensation
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Solution Overview
Problem
Existing diffractive beam expanders in virtual display devices can suffer from image deformation due to incorrect grating periods and orientations, leading to severe deformation and rejection of manufactured units, and cause chromatic aberration and dispersion-induced elongation of image points.
Innovation Solution
A display apparatus with a diffractive waveguiding expander device that includes a modifying unit comprising one or more prisms to compensate for non-zero grating vector sums, ensuring output light beams of different colors remain parallel and reducing wavelength-dependent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the sum of grating vectors of diffractive elements is designed to be zero to ensure parallel output light beams, then the image quality is improved, but any manufacturing deviation causes severe image deformation leading to product rejection
Solution Approach 1:
A modifying unit comprising at least one prism is introduced as an intermediary component between the optical engine and the diffractive waveguiding expander device. This prism compensates for non-zero grating vector sums by introducing an opposite angular deflection, thereby correcting image deformation caused by manufacturing tolerances in the diffractive elements without requiring extremely precise manufacturing of the diffractive elements themselves
Solution Approach 2:
The modifying unit with the prism performs preliminary correction of angular deflection before the light enters the diffractive waveguiding expander device. By pre-compensating for potential grating vector sum errors, the system ensures that even if the diffractive elements have manufacturing deviations, the final image quality remains stable and within acceptable ranges
2Productivity
If diffractive elements with specific grating periods and orientations are used to expand light beams, then the beam expansion function is achieved, but wavelength-dependent deformation and chromatic aberration occur
Solution Approach 1:
The modifying unit changes the angular parameter of light beams wavelength-dependently through the prism's dispersive properties. By carefully selecting the prism's material and geometry, the system compensates for wavelength-dependent angular deflections caused by the diffractive elements, ensuring that output light beams of different colors remain parallel while maintaining efficient beam expansion
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 effectively corrects wavelength-dependent image deformation, ensuring sharp and aligned output light beams, thereby improving image quality and reducing manufacturing costs by accommodating manufacturing tolerances.
Implementation Method 1
The modifying unit comprises at least a first prism to reduce the difference between the first angular deflection and the second angular deflection
Implementation Method 2
The diffractive waveguiding expander device is configured to form output light by diffractively expanding the second input light
Data Source
AI summary
A display apparatus comprises an optical engine, a modifying unit, and a diffractive waveguiding expander device. The optical engine is configured to form first input light, which comprises a plurality of input light beams representing an input image. The modifying unit is configured to form second input light from the first input light. The diffractive waveguiding expander device is configured to form output light by diffractively expanding the second input light, where the output light comprises a plurality of output light beams representing said input image. The modifying unit contain at least one prism, which compensates the angular dispersion between the plurality of output light beams caused by the possibly exists imperfection of the waveguiding expander device.