Projector Eyepiece Waveguide Filters for Artifact Mitigation
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Solution Overview
Problem
Existing augmented reality systems suffer from artifacts and ghost images due to stray light and wavelength cross-coupling, which degrade image quality and user experience.
Innovation Solution
The use of absorptive color filters and optimized sub-pupil arrangements in conjunction with planar waveguides and diffractive optical elements to reduce stray light and wavelength cross-coupling, enhancing brightness, contrast, and color accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional projection display systems are used, then light from overhead lights and unintended reflections can be coupled into the eyepiece, but this creates artifacts and ghost images that degrade image quality
Solution Approach 1:
The patent introduces an intermediary optical element (such as a beam splitter or dichroic mirror) between the projection system and the eyepiece. This intermediary selectively transmits the projected light wavelengths while reflecting or blocking stray light from overhead lights and unintended reflections, thereby preventing artifacts and ghost images from entering the eyepiece without requiring complete system redesign
Solution Approach 2:
The patent applies wavelength-selective filtering at specific locations within the optical path, particularly at the eyepiece interface. By placing spectral filters or dichroic coatings at strategic positions, the system allows desired projected light to pass through while locally blocking harmful stray light, thus improving image quality without affecting the overall simplicity of the projection system
2Illumination intensity
If color filters are used to reduce wavelength cross-coupling, then brightness and contrast are enhanced, but the system complexity increases
Solution Approach 1:
The patent employs optical elements such as dichroic mirrors or beam splitters that perform multiple functions simultaneously: they separate wavelengths to reduce cross-coupling, reflect stray light to prevent artifacts, and maintain high transmission of desired light. This multi-functionality achieves brightness and contrast enhancement without proportionally increasing system complexity
Solution Approach 2:
The patent utilizes optical elements with wavelength-dependent parameters, such as dichroic mirrors with specific reflection and transmission bands. By carefully selecting the spectral characteristics of these elements, the system achieves effective wavelength separation and artifact reduction while maintaining high overall transmission, thus enhancing brightness and contrast without excessive complexity
3Measurement precision
If absorptive color filters are used to reduce stray light, then contrast and color accuracy improve, but light transmission is reduced
Solution Approach 1:
The patent introduces reflective or dichroic filtering elements as intermediaries that redirect or selectively transmit light rather than absorbing it. These elements achieve superior color accuracy and contrast by reflecting unwanted wavelengths away from the optical path while maintaining high transmission of desired wavelengths, thereby improving measurement precision without significant energy loss
Solution Approach 2:
The patent replaces absorptive color filters with reflective or dichroic optical elements. Instead of absorbing stray light and losing it as heat, these elements reflect unwanted wavelengths away from the optical path or redirect them to alternative paths, thereby achieving the same color separation and contrast improvement while preserving more light energy for the final image
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 approach effectively minimizes artifacts and ghost images, improves resolution and dynamic range, reduces eye strain, and enhances overall image quality in augmented reality systems.
Implementation Method 1
An optical filter is coupled to a second planar waveguide at a second lateral position that is different from the first lateral position. The optical filter is operable to transmit light in a first wavelength range and absorb light in a second wavelength range.
Implementation Method 2
Each planar waveguide includes a diffractive optical element disposed at a first lateral position. The diffractive optical element is configured to diffract light at the first lateral position.
Data Source
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AI summary
An eyepiece unit with optical filters includes a set of waveguide layers including a first waveguide layer and a second waveguide layer. The first waveguide layer is disposed in a first lateral plane and includes a first incoupling diffractive element disposed at a first lateral position, a first waveguide, and a first outcoupling diffractive element. The second waveguide layer is disposed in a second lateral plane adjacent to the first lateral plane and includes a second incoupling diffractive element disposed at a second lateral position, a second waveguide, and a second outcoupling diffractive element. The eyepiece unit also includes a set of optical filters including a first optical filter positioned at the first lateral position and operable to attenuate light outside a first spectral band and a second optical filter positioned at the second lateral position and operable to attenuate light outside a second spectral band.