Compact Image Projector Stack to Reduce Ghost Images
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Solution Overview
Problem
Existing optical systems for near eye displays and head mounted displays face challenges with bulky and costly components due to the use of reflective or transmissive display devices, which introduce ghost images and chromatic aberrations, and require complex illumination components, making them unsuitable for compact form factors.
Innovation Solution
A compact image projector is designed using an emissive display device with optical components arranged in a stack within a hollow mechanical body, employing engagement configurations and optical coupling-in configurations to reduce ghost images and chromatic aberrations, and is manufactured using plastic, glass, or polymer materials through casting or injection molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflective or transmissive display devices are used in optical systems, then image projection capability is achieved, but ghost images and chromatic aberrations are introduced
Solution Approach 1:
The patent extracts and eliminates the problematic reflective or transmissive display devices that cause ghost images and chromatic aberrations. Instead, it uses a direct light source (LED or laser) that projects light through a diffractive optical element, thereby removing the harmful reflective interfaces while maintaining image projection capability
Solution Approach 2:
The patent introduces a diffractive optical element as an intermediary between the light source and the light guide. This element modulates the light to create the image without requiring reflective or transmissive display devices, thus preventing ghost images and chromatic aberrations while achieving the desired image projection
2Reliability
If reflective or transmissive display devices with illumination components are used, then image generation is achieved, but device size and weight increase
Solution Approach 1:
The patent removes the complex illumination components (polarizers, beam combiners, separate light sources) that are required by reflective or transmissive display devices. By using a simple direct-emitting light source like LED or laser diode, the system achieves image generation with dramatically reduced weight and complexity
Solution Approach 2:
The patent merges the light source and image generation functions into a single integrated system. The LED or laser diode directly emits light that is modulated by the diffractive optical element, eliminating the need for separate illumination paths and components, thereby reducing overall device weight
3Ease of operation
If wedge coupling-in configurations are used with reflective or transmissive display devices, then light coupling into light guide is achieved, but ghost images are introduced
Solution Approach 1:
The patent eliminates the wedge coupling-in configuration that is used with reflective or transmissive display devices. Instead, it uses a simplified direct coupling approach where the diffractive optical element is positioned close to the light guide entrance, removing the wedge interface that causes ghost images while maintaining efficient light coupling
Solution Approach 2:
The diffractive optical element serves as an intermediary that directly modulates the light from the source before it enters the light guide. This eliminates the need for wedge prisms and their associated ghost image problems, while still achieving effective light coupling into the waveguide
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 results in a lightweight and cost-effective optical system that minimizes ghost images and chromatic aberrations, suitable for compact near eye displays and head mounted displays.
Implementation Method 1
a light-guide optical element having a pair of parallel major external surfaces for guiding light by internal reflection (preferably total internal reflection)
Implementation Method 2
The projected image is coupled into the light-guide optical element by an optical coupling-in configuration, as illustrated here schematically by a prism
Implementation Method 3
Part of the image wavefront is coupled out of the slab, either by use of obliquely angled partial reflectors
Implementation Method 4
impinging on an optical coupling-out configuration, as illustrated here schematically by a sequence of partially reflecting surfaces at an oblique angle (αsur) to the parallel faces
Data Source
AI summary
An optical system has a hollow mechanical body having first and second ends. An optical assembly has a plurality of optical components arranged in a stack configuration. Each of the optical components has a set of engagement configurations. For each pair of adjacent optical components in the stack configuration, at least some of the engagement configurations of a first optical component in the pair engage with at least some of the engagement configurations of a second optical component in the pair. Some of the engagement configurations of the optical component at a first end of the stack configuration engage with corresponding engagement configurations of the hollow mechanical body at the first end of the hollow mechanical body to position the other optical components of the stack configuration within the hollow mechanical body. An emissive display device is deployed at the second end of the hollow mechanical body.