Optical Device Using Mixed Diffraction Elements for Color Uniformity
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Solution Overview
Problem
Existing image projecting apparatuses face challenges with color unevenness due to wavelength dependency of optical diffraction elements, leading to increased manufacturing costs and difficulties in controlling diffraction angles, which degrade image quality.
Innovation Solution
An optical device configuration featuring a light guide with a transmission type first diffraction element for emitting light, a transmission type second diffraction element for entering light, and a reflection type third diffraction element on the opposite face, allowing zero-order light to be diffracted and increasing light emission efficiency, while maintaining a simple structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple optical diffraction elements are layer-stacked to address wavelength dependency, then color unevenness is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple diffraction elements of different types (transmission type and reflection type) into a single integrated optical device structure. The transmission type diffraction element is disposed on the light incident surface while the reflection type diffraction element is disposed on the light emitting surface, merging their functions into one compact unit that reduces color unevenness without requiring separate stacked layers.
Solution Approach 2:
The optical device is segmented into functionally distinct components: a transmission type diffraction element for causing light to enter the light guide, and a reflection type diffraction element for causing guided light to be emitted. This segmentation allows each element to be optimized for its specific function while working together to reduce color unevenness.
2Manufacturing precision
If multiple optical diffraction elements are provided in stacked layers, then wavelength dependency is compensated, but light control becomes difficult and image quality degrades
Solution Approach 1:
The patent merges the light entry function and light emission function into a single optical device with properly positioned diffraction elements. The transmission type diffraction element is placed on the light incident surface and the reflection type diffraction element is placed on the light emitting surface, allowing coordinated control of light paths without the complexity of stacked layers.
Solution Approach 2:
The light guide acts as an intermediary medium between the two diffraction elements. The transmission type diffraction element couples light into the light guide, which then guides the light to the reflection type diffraction element for emission. This intermediary structure enables independent optimization of each diffraction element's function while maintaining overall system control.
3Productivity
If zero-order light is not diffracted by the second diffraction element, then light emission efficiency is low, but adding more diffraction elements increases complexity
Solution Approach 1:
The patent utilizes the zero-order light that passes through the transmission type diffraction element by directing it to the reflection type diffraction element on the opposite surface. This merged configuration ensures that zero-order light is not wasted but is instead effectively diffracted to contribute to light emission, improving overall efficiency without adding stacked layers.
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 enables the display of bright and high-quality virtual images with improved light emission efficiency and reduced manufacturing complexity, addressing the issues of color unevenness and image quality degradation.
Implementation Method 1
a first diffraction element that is a transmission type diffraction element provided on a first face of the light guide and that diffracts and emits at least a portion of light which is guided along inside the light guide
Implementation Method 2
a second diffraction element that is a transmission type diffraction element provided on the first face of the light guide and that diffracts at least a portion of light which enters the light guide
Implementation Method 3
a third diffraction element that is a reflection type diffraction element provided on a face which is an opposite face of the light guide from the first face, and that diffracts at least a portion of light which enters an inside of the light guide via the second diffraction element
Data Source
AI summary
An optical device includes a light guide plate; a first diffraction element that is a transmission type diffraction element provided on a first face of the light guide plate and that diffracts and ejects at least a portion of light which is guided along inside the light guide plate; a second diffraction element that is a transmission type diffraction element provided on the first face of the light guide plate and that diffracts at least a portion of light proceeding to the light guide plate; and a third diffraction element that is a reflection type diffraction element provided on a face which is an opposite face of the light guide plate from the first face, and that diffracts at least a portion of light which enters an inside of the light guide plate via the second diffraction element.