Display Device Light-Transmitting Member Optical Unit
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Solution Overview
Problem
Existing display devices with two diffraction elements in an optical conjugated relationship face challenges in size reduction due to the need for equal diffraction angles, leading to issues like ghost images and decreased resolution from zero-order light interference.
Innovation Solution
Incorporating a correction optical system with a light-transmitting member and a light shielding member in the optical path, allowing for different diffraction angles between the first and second diffraction elements while ensuring wavelength compensation and reducing zero-order light incidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If two diffraction elements are used in an optical conjugated relationship with equal diffraction angles to perform wavelength compensation, then color aberration is canceled and image resolution is maintained, but the display device increases in size
Solution Approach 1:
The patent changes the diffraction angle parameter of the first diffraction element to be different from the second diffraction element. Specifically, the first diffraction element has a diffraction angle of 10 degrees while the second has 20 degrees, breaking the conventional equal-angle requirement for wavelength compensation and enabling compact device design
Solution Approach 2:
A light shielding member is introduced as an intermediary component between the two diffraction elements. This member blocks zero-order light from the first diffraction element, preventing it from reaching the observer's eye and causing ghost images, while allowing the different diffraction angle configuration to work effectively
2Volume of moving object
If the diffraction angle of the first diffraction element is made smaller than that of the second diffraction element to reduce device size, then device compactness is improved, but zero-order light propagates through the optical system and causes ghost images
Solution Approach 1:
The patent converts the harmful zero-order light into a controllable element by using the light shielding member to selectively block it. The light shielding member transforms the potential harm of zero-order light propagation into a beneficial outcome by preventing ghost images while maintaining the compact different-angle configuration
Solution Approach 2:
The light shielding member extracts or removes the harmful zero-order light component from the optical path between the two diffraction elements, separating it from the useful diffracted light that forms the image, thereby eliminating ghost images
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 a compact display device design with improved image quality by canceling color aberration and minimizing ghost images, maintaining high resolution.
Implementation Method 1
image light emitted from an image light generating device is directed by a first diffraction element of the reflective type
Implementation Method 2
a second diffraction element deflects, toward the eye of the observer, the image light emitted from the first diffraction element
Implementation Method 3
a first light-transmitting member having optical power and provided at a first surface of the first diffraction element
Data Source
AI summary
A display device according to the present invention includes, along an optical path of image light emitted from an image light generating device, a first optical unit having positive power, a second optical unit having positive power and including a first diffraction element of a reflective type, a third optical unit having positive power, and a fourth optical unit having positive power and including a second diffraction element of a reflective type. The second optical unit includes a first light-transmitting member having optical power and provided at a first surface of the first diffraction element, and a light shielding member provided at a second surface of the first diffraction element.