Display Device Optical Unit with High Modulus Glass Member
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Solution Overview
Problem
Display devices with diffraction elements face issues of reduced resolution due to peripheral wavelengths causing color aberration and image blur, especially when using plastic lenses that expand or contract during exposure, affecting diffraction performance.
Innovation Solution
A display device configuration with a first optical unit, a second optical unit including a reflection-type diffraction element and a correction optical system with a transmissive first member and second member, where the first member has an elastic modulus of 50 GPa or greater, and the second member has optical power, to correct the diffraction angles and compensate for peripheral wavelengths, thereby maintaining image quality and reducing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a plastic lens member is used to reduce weight, then the weight of the lens member is reduced, but the diffraction element expands or contracts during exposure, resulting in poor diffraction performance
Solution Approach 1:
The patent changes the material parameter (elastic modulus) from plastic to glass, which has higher rigidity and does not expand or contract during exposure, thereby maintaining diffraction performance while accepting increased weight
Solution Approach 2:
The patent uses a composite structure combining glass (first member) and resin (second member), where the glass provides dimensional stability for diffraction performance and the resin provides lightweighting and optical power functions
2Power
If a lens member with optical power is provided on one surface side of the first diffraction element, then optical power is provided, but refraction at the curved surface greatly affects the exposure, resulting in blur and reduced resolution
Solution Approach 1:
The patent divides the optical system into two separate members: the first member (glass) for diffraction with flat exposure surface, and the second member (resin) for optical power with curved surface, thereby separating the conflicting requirements of flat exposure surface and curved optical surface
Solution Approach 2:
The patent introduces a flat- surfaced first member as an intermediary between the light and the curved second member, allowing exposure to occur on a flat surface while still providing optical power through the subsequent curved surface
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 configuration effectively cancels color aberration, maintains high image quality, and allows for size reduction of the display device by ensuring accurate diffraction performance and wavelength compensation across different wavelengths.
Implementation Method 1
interference fringes are optimized in the diffraction element to obtain an optimum diffraction angle and optimum diffraction efficiency
Implementation Method 2
the second diffraction element deflects, toward the eye of the observer, the imaging light emitted from the first diffraction element
Implementation Method 3
the first member is transmissive and has an elastic modulus of 50 GPa or greater
Implementation Method 4
the second member is transmissive and has optical power
Data Source
AI summary
A display device according to the present disclosure includes a first optical unit having positive power, a second optical unit including a first diffraction element and having positive power, a third optical unit having positive power, and a fourth optical unit including a second diffraction element and having positive power, and the first to fourth optical units are provided along an optical path of imaging light emitted from an imaging light generating device. The second optical unit further includes a first member provided at one surface side of the first diffraction element, and a second member provided on a side of the first member opposite to a side where the first diffraction element is located, the first member is transmissive and has an elastic modulus of 50 GPa or greater, and the second member is transmissive and has optical power.