Virtual Image Display Apparatus Diffusion Element Beam Separation
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Solution Overview
Problem
Retinal scanning type virtual image display apparatuses face issues with beam cross-section expansion and blurring due to the arrangement of diffraction elements, which compromises the suppression of image blurring regardless of eye abnormalities.
Innovation Solution
A virtual image display apparatus featuring a diffusion element that separates light into first and second emission lights with a separation angle greater than the capturing angle, preventing both from entering the pupil simultaneously, while allowing either to enter when the eye direction changes, using a periodic structure on the diffusion element to achieve this separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a diffraction element is used to separate the original beam into three beams to expand the exit pupil, then the exit pupil is expanded, but the beam cross-section expands and blurs the Maxwellian view
Solution Approach 1:
The patent divides the single original beam into multiple discrete beams (first beam, second beam, third beam) using a diffraction element with multiple diffraction orders. This segmentation allows the exit pupil to be expanded by having multiple beam paths while maintaining distinct, non-overlapping beam cross-sections that prevent blurring of the Maxwellian view.
Solution Approach 2:
The patent applies different diffraction characteristics to different parts of the beam by using a diffraction element with specific groove structures. The first diffraction order produces a first beam with a specific diffraction angle, the second diffraction order produces a second beam with a different angle, and the zeroth order produces a third beam. This local differentiation of diffraction properties allows each beam to have controlled characteristics that prevent cross-section expansion and maintain image clarity.
2Adaptability or versatility
If three beams are arranged to enter into a pupil to expand the exit pupil, then the exit pupil is expanded, but the image blurring occurs due to beam cross-section expansion
Solution Approach 1:
The patent makes the beam arrangement dynamic by allowing the diffraction element to be rotated or adjusted. The diffraction element can be rotated to different angles to change the directions of the first, second, and third beams. This dynamic adjustment ensures that the beams can be precisely controlled to enter the pupil at appropriate angles while maintaining separated beam cross-sections that prevent image blurring.
Solution Approach 2:
The patent changes the diffraction angle parameter by adjusting the diffraction element's groove density, pitch, or rotation angle. By varying these parameters, the patent can control the directions of the diffracted beams to ensure they enter the pupil appropriately while maintaining sufficient separation between beam cross-sections to prevent blurring and maintain image quality.
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 ensures a clear, high-quality image presentation even with eye abnormalities by preventing simultaneous entry of emission lights into the pupil, maintaining image clarity during eye movement.
Implementation Method 1
a diffusion element arranged at a position of the intermediate image formed by the scanner, and configured to separate light from the scanner into first emission light used as a reference, and second emission light having a separation angle greater than a capturing angle corresponding to an inclination of light toward a predetermined pupil radius relative to the first emission light at an emission position of the light from the diffusion element
Data Source
AI summary
Provided is a virtual image display apparatus including a laser light source, a scanner configured to scan light from the laser light source and render an intermediate image, a diffusion element arranged at a position of the intermediate image formed by the scanner, and an exit pupil forming unit configured to cause light that has passed through the diffusion element to be incident on a position of an exit pupil. The diffusion element separates the light from the scanner into first emission light used as a reference, and second emission light having a separation angle greater than a capturing angle corresponding to an inclination of light toward a predetermined pupil radius relative to the first emission light at an emission position of the light from the diffusion element, and then emits the first emission light and the second emission light.