Image Display Device Dual Diffraction Elements Aberration Correction
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Solution Overview
Problem
Image display devices using diffraction elements, such as holographic elements, face a reduction in image resolution due to the spectrum width of light sources like LEDs and OLEDs, as different wavelengths cause shifts in diffraction angles, leading to focal point misalignment on the retina.
Innovation Solution
An image display device configuration that includes a projection system optical unit, a correction system optical unit, and two diffraction elements, where the image light is dispersed by the second diffraction element and focused by the first diffraction element, compensating for wavelength-dependent diffraction angle shifts, ensuring parallel rays are directed to the observer's eye, thereby maintaining image resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a light source with spectrum width (LED, OLED) is used, then the device can be more practical and cost-effective, but image resolution deteriorates due to wavelength-dependent diffraction angle shifts
Solution Approach 1:
The patent divides the diffraction function into two separate elements: a first diffraction element that disperses light into wavelengths, and a second diffraction element that focuses the dispersed light. This segmentation allows each element to be optimized for its specific function, resolving the contradiction between using broad-spectrum light sources and maintaining image resolution.
Solution Approach 2:
The patent introduces an intermediary optical system between the two diffraction elements that includes a correction system optical unit. This intermediary system corrects aberrations of the dispersed light before it reaches the second diffraction element, thereby maintaining image quality when using light sources with spectrum width.
2Power
If interference fringes are optimized for a specific wavelength, then diffraction efficiency is maximized, but rays with shifted wavelengths cause focal point misalignment
Solution Approach 1:
The patent segments the diffraction process into two stages performed by separate elements. The first element disperses light while the second element focuses it, allowing each to be optimized for its specific wavelength range. This resolves the contradiction by enabling broad-spectrum efficiency while maintaining focal point alignment through the coordinated action of both elements.
Solution Approach 2:
The patent changes the optical parameters (diffraction angles, focal lengths) of the two diffraction elements to compensate for wavelength-dependent shifts. By carefully designing the parameters of both elements, the system maintains focal point alignment across the spectrum width of practical light sources like LEDs and OLEDs.
3Device complexity
If a single diffraction element is used, then the device structure is simpler, but color unevenness and resolution loss occur
Solution Approach 1:
The patent divides the optical system into distinct functional units: a projection system optical unit, a correction system optical unit, and two diffraction elements. This segmentation, while increasing structural complexity, enables each unit to perform its specific function optimally, thereby improving image quality and resolving the contradiction between simplicity and performance.
Solution Approach 2:
The patent introduces a correction system optical unit as an intermediary between the two diffraction elements. This intermediary unit corrects aberrations and enables the system to achieve high image quality by compensating for the limitations of using practical light sources with spectrum width.
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 configuration effectively compensates for wavelength-dependent diffraction angle shifts, reducing focal point misalignment and maintaining image resolution, even with light sources having spectrum widths, allowing for high-quality image display.
Implementation Method 1
a first diffraction element (61) configured to deflect image light incident on a first incident surface
Implementation Method 2
a second diffraction element (31) configured to deflect the image light incident on a second incident surface and disperse the image light into rays of respective wavelengths
Implementation Method 3
a correction system optical unit (21) configured to correct aberrations of the image light
Data Source
AI summary
An image display device includes an image light generation unit configured to generate image light, a projection system optical unit configured to project the image light, a correction system optical unit configured to correct aberrations, a first diffraction element configured to deflect the image light incident on a first incident surface, and a second diffraction element configured to deflect the image light incident on a second incident surface. The projection system optical unit, the second diffraction element, the correction system optical unit, and the first diffraction element are arranged in this order in a direction of the image light emitted from the image light generation unit, and the image light deflected and dispersed into rays of respective wavelengths by the second diffraction element is focused by the first diffraction element.