Light Guide Plate Reflecting Units for Virtual Image Display Resolution
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Solution Overview
Problem
Existing light guide plates for virtual image display devices, such as head-mount displays, suffer from local degradation of image resolution due to differences in light beam width caused by varying total reflection angles within the plate.
Innovation Solution
A light guide plate design featuring a light entrance section, a light guide section with opposing total reflection surfaces, and an image take-out section with varying reflecting unit sizes and pitches to adjust for total reflection angles, ensuring consistent effective light beam width and preventing resolution degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If parallel partial reflecting surfaces are used in the light guide plate, then the image light can be taken out, but the resolution degrades locally due to differences in light beam width caused by varying total reflection angles
Solution Approach 1:
The patent applies local quality by varying the sizes and pitches of reflecting units at different positions in the image take-out section. Specifically, reflecting units closer to the light entrance section are made smaller with smaller pitches, while those farther away are made larger with larger pitches. This local variation compensates for the different total reflection angles experienced by light beams at different positions, maintaining consistent effective light beam width and preventing local resolution degradation.
Solution Approach 2:
The patent changes the parameters of reflecting units (size and pitch) along the arranging direction to compensate for variations in total reflection angle. By adjusting these parameters, the effective light beam width is maintained across different positions, resolving the contradiction between image light take-out capability and image resolution.
2Device complexity
If uniform reflecting units are used throughout the light guide plate, then the structure is simple, but the effective light beam width varies causing resolution degradation
Solution Approach 1:
Instead of using uniform reflecting units throughout, the patent implements local quality by making reflecting units have different sizes and pitches depending on their position. Units nearer to the light entrance section are smaller with tighter pitches, while units farther away are larger with wider pitches. This local differentiation maintains consistent effective light beam width without requiring overly complex structures.
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 effectively maintains a sufficient effective light beam width, preventing image light deterioration and ensuring high-resolution virtual image display by adjusting reflecting unit sizes and pitches in accordance with total reflection angles, thereby preventing local resolution degradation.
Implementation Method 1
a light guide section having first and second total reflection surfaces extending so as to be opposed to each other, and adapted to guide the image light taken in from the light entrance section by total reflection on the first and second total reflection surfaces
Implementation Method 2
an image take-out section having a plurality of reflecting units arranged in a predetermined arranging direction, and adapted to make it possible to take out the image light, which enters via the light guide section, to an outside by bend of a light path in the plurality of reflecting units
Data Source
AI summary
The sizes of the respective reflecting units vary in the image take-out section along the Z direction in association with the state of the total reflection angle in the light guide section. Thus, it becomes possible to keep the sufficient effective light beam width of the image light input thereto in all of the reflecting units. Therefore, the deterioration in the image light caused by the reflection in the reflecting units can be avoided, and as a result, the degradation of the resolution of the image due to the virtual image light thus emitted can be prevented.