Image Display Apparatus with Inclined Optical Axis for Trapezoidal Projection
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Solution Overview
Problem
Projectors used for digital signage and automobile head-up displays face issues with focus imbalance and uneven illuminance distribution when projecting trapezoidal images, particularly when the projected surface is inclined relative to the optical axis.
Innovation Solution
An image display device with a refractive optical system comprising multiple lenses, where the optical axis is inclined at 1° or more relative to the image forming surface, and a condensing optical system with a focal point closer to the field lens than the image forming element, ensuring that first and second rays form distinct portions of the trapezoidal shape with adjusted focal points to balance illuminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the projected surface is inclined with respect to the optical axis to achieve trapezoidal image projection, then the adaptability to different projection surfaces is improved, but the focus balance and illuminance distribution deteriorate
Solution Approach 1:
The patent introduces an asymmetric optical element (prism or lens with asymmetric surface) in the illumination optical system that creates asymmetric illuminance distribution on the image forming element. This asymmetric illumination compensates for the asymmetric illuminance distribution caused by the inclined projection surface, thereby maintaining uniform overall illuminance in the projected image while preserving the ability to project on inclined surfaces.
Solution Approach 2:
The patent changes the illuminance distribution parameter on the image forming element by introducing an asymmetric optical element. This parameter change compensates for the illuminance imbalance caused by the inclined projection surface, allowing the system to maintain uniform illuminance in the final projected image while adapting to different projection surface angles.
2Ease of operation
If uniform illuminance is provided on the image forming element, then the ease of manufacture and operation is improved, but the illuminance distribution in the projected image deteriorates when the surface is inclined
Solution Approach 1:
The patent introduces an asymmetric optical element (prism or lens with asymmetric surface) in the illumination optical system that creates asymmetric illuminance distribution on the image forming element. This asymmetric illumination compensates for the asymmetric illuminance distribution caused by the inclined projection surface, thereby maintaining uniform overall illuminance in the projected image while preserving the ability to project on inclined surfaces.
Solution Approach 2:
The patent applies local quality by creating different illuminance conditions in different regions of the image forming element. The asymmetric optical element specifically adjusts the illuminance in regions that will be projected to the inclined surface, compensating for the expected illuminance imbalance in those specific areas while leaving other regions unaffected.
3Manufacturing precision
If the optical axis is perpendicular to the image forming surface, then the manufacturing precision and focus are improved, but the adaptability to inclined projection surfaces deteriorates
Solution Approach 1:
The patent introduces an asymmetric optical element (prism or lens with asymmetric surface) in the illumination optical system that creates asymmetric illuminance distribution on the image forming element. This asymmetric illumination compensates for the asymmetric illuminance distribution caused by the inclined projection surface, thereby maintaining uniform overall illuminance in the projected image while preserving the ability to project on inclined surfaces.
Solution Approach 2:
The asymmetric optical element acts as an intermediary between the uniform illumination source and the inclined projection surface. It transforms the uniform illumination into asymmetric illumination that pre-compensates for the illuminance imbalance that would occur on the inclined surface, serving as a mediator that enables both perpendicular optical axis and inclined projection adaptability.
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 effectively eliminates focus imbalance and illuminance distribution issues in trapezoidal images, providing a balanced and uniform visual experience for digital signage and HUD systems.
Implementation Method 1
a projection optical system having a refractive optical system (21) composed of a plurality of lenses sharing an optical axis L for projecting an image formed by the image forming element (30) onto a projected surface
Implementation Method 2
The illumination optical system includes a condenser lens and a field lens as a condensing optical system, the condenser lens is between the field lens and the light source
Data Source
AI summary
An image display apparatus includes an image forming element, an illumination optical system that guides light emitted from a light source to the image forming element, and a plurality of lenses that project a trapezoidal image formed by the image forming element onto a projected surface. The plurality of lenses have an optical axis that is at an inclination of 1° or more with respect to a perpendicular of a plane including an image forming surface of the image forming element. First rays of the light have a first focal point and second rays of the light have a second focal point. The first focal point is farther from the image forming element than the second focal point is from the image forming element. The first rays form the first portion of the trapezoidal shape and the second rays form the second portion of the trapezoidal shape.