Light-Guiding Plate Tilt for Image Display Ghost Prevention
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Solution Overview
Problem
Existing image display apparatuses suffer from reduced image contrast due to light feedback from the light-guiding plate, causing ghost images when light from one part of the image forming device is reflected onto another part, especially when displaying different intensity images like 'white' and 'black'.
Innovation Solution
The image display apparatus is designed such that light emitted from the image forming device is collimated and incident on the light-guiding plate at specific angles, ensuring that any reflection occurs in a direction away from the image forming device, preventing light feedback and maintaining optical wavefront information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If light is incident on the light-guiding plate at zero degrees (perpendicularly), then the optical system is simplified and light transmission is efficient, but light is reflected back to the image forming device causing reduced image contrast and ghost images
Solution Approach 1:
The patent introduces asymmetry by tilting the light-guiding plate relative to the optical axis. The plate is configured at a specific angle (e.g., 45 degrees) so that light incident from the collimating optical system strikes the plate at non-zero angles. This asymmetric configuration ensures that reflected light is directed away from the image forming device, preventing feedback and ghost images while maintaining optical efficiency.
Solution Approach 2:
Instead of directing light perpendicularly to the light-guiding plate (conventional approach), the patent inverts the approach by intentionally incidenting light at oblique angles. This inversion of the incident angle strategy transforms the harmful reflection back toward the image forming device into useful reflected light directed away from it, thereby eliminating the harmful feedback effect.
2Object-affected harmful factors
If an antireflective film is provided on the plane of incidence of the light-guiding plate, then some light reflection is reduced, but part of the light is still reflected back causing ghost images and reduced image contrast
Solution Approach 1:
The patent extracts and removes the problematic reflection pathway by changing the geometric configuration. Instead of attempting to suppress reflection through coating alone, the design extracts the reflected light from the harmful feedback path by tilting the light-guiding plate, directing it away from the image forming device. This geometric extraction is more effective than relying solely on antireflective coatings.
3Device complexity
If light from one part of the image forming device is reflected onto another part, then the display can be made with simpler optical components, but image contrast is reduced due to ghost images
Solution Approach 1:
The asymmetric tilting of the light-guiding plate creates directionality in light propagation. Light from different parts of the image forming device is directed at different angles onto the tilted plate, and the reflection geometry ensures that these reflected rays are directed away from the image forming device rather than back into it. This asymmetric configuration prevents cross-talk and maintains image contrast.
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 improves image contrast and prevents ghost images, allowing for high-quality image display by ensuring that light is not fed back to the image forming device, thereby enhancing the overall image quality.
Implementation Method 1
a light-guiding plate propagating thereinside the light received thereby with total reflection and outputting the propagated light
Implementation Method 2
a first optical member reflecting the light received by the light-guiding plate so as to cause the light received by the light-guiding plate to be totally reflected inside the light-guiding plate
Data Source
AI summary
An image display apparatus includes an image forming device having pixels; a collimating optical system collimating light from the image forming device; and an optical device receiving, guiding, and outputting the collimated light as directional rays in different directions. The optical device includes a light-guiding plate; a first optical member reflecting or diffracting the light so as to totally reflect the light inside the light-guiding plate; and a second optical member causing the propagated light to emerge from the light-guiding plate. When a light ray emitted from a pixel located farthest from the center of the image forming device and a light ray emitted from a pixel located at the center of the image forming device pass through a front nodal point of the collimating optical system and are respectively incident on the collimating optical system and the light-guiding plate at angles θ1 and θ2, θ2>θ1 is satisfied.