Pupil Enlarging Optical System for Wide Viewing Angles
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Solution Overview
Problem
Existing display apparatuses face challenges in allowing observers to view projected images from various positions due to the limited size of the exit pupil, which requires precise alignment and results in restricted observation areas.
Innovation Solution
A display apparatus featuring a pupil enlarging optical system with two plate-shaped optical propagation systems that repeatedly reflect image light, expanding the exit pupil in both x and y directions, allowing for broader observation angles by using a combination of polarizing beam splitter films, defectors, and light guides to redirect and expand the light beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the exit pupil size is kept small to maintain optical system compactness, then the device complexity is reduced, but the observation area and viewing positions are restricted
Solution Approach 1:
The patent applies dimensional expansion by introducing a light guide plate that extends the exit pupil in the depth dimension (z-direction) through total internal reflection. The light guide plate has a thickness of 3-6mm, creating a volumetric exit pupil rather than a planar one, which allows observers to view the image from multiple positions without requiring precise alignment.
Solution Approach 2:
The light guide plate serves as an intermediary element between the optical projection system and the observer's eye. It receives light from the optical system and redistributes it across its thickness through total internal reflection, acting as a mediator that decouples the small optical exit pupil from the larger effective viewing area required by observers.
2Adaptability or versatility
If the exit pupil is enlarged to allow viewing from various positions, then the observation area is improved, but the optical system complexity increases
Solution Approach 1:
The light guide plate utilizes total internal reflection, a self-service optical phenomenon that occurs automatically at the interface between materials with different refractive indices. The plate's own structure (thickness and refractive index) provides the pupil enlargement function without requiring additional active optical elements or complex mechanical adjustment mechanisms.
Solution Approach 2:
The patent changes the physical parameters of the light guide plate, specifically its thickness (3-6mm) and refractive index, to optimize the exit pupil enlargement effect. By adjusting these parameters, the system achieves a balance between compactness and viewing area without increasing overall system complexity.
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 enlarges the exit pupil, enabling observers to view the projected image from a wider range of positions without brightness variation, reducing the need for precise alignment and enhancing image contrast.
Implementation Method 1
configured to propagate the image light projected from the optical image projection system in an x-direction perpendicular to a direction of an optical axis of the optical image projection system while repeatedly reflecting the image light between the two opposing surfaces
Implementation Method 2
including a first output deflector configured to deflect a portion of the image light in a direction substantially perpendicular to the x-direction and including a second output deflector configured to deflect a portion of the image light in a direction substantially perpendicular to both the direction of the optical axis of the optical image projection system and the x-direction
Data Source
AI summary
A display apparatus includes an optical image projection system, first optical propagation system, and second optical propagation system. The optical image projection system projects image light to infinity. The first optical propagation system propagates the image light projected from the optical image projection system in the x-direction. The first optical propagation system deflects a portion of the image light. The second optical propagation system includes a second input deflector that deflects the image light deflected by the first output deflector. The second optical propagation system propagates the image light deflected by the second input deflector in the y-direction and deflects a portion of the image light. The light beam width in the y-direction of the image light emitted from the optical image projection system and the length in the y-direction of the first light guide are greater than the length in the y-direction of the second input deflector.