Diffractive Optical Combiner for Near-Eye Displays
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Solution Overview
Problem
Conventional holographic and angled transparent substrate combiners used in head-up displays are expensive, difficult to mass produce, and have limited lifespan due to environmental factors, making them unsuitable for compact applications like head-mounted displays.
Innovation Solution
A diffractive optical combiner system with multiple color layers, each with a diffractive grating coated with a color filter, embedded in index-matched materials, which combines image light with external scene light using reflective and partially transmissive filters to direct colors substantially normal to the user's eye, allowing for compact and durable near-eye displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If holographic combiners are used, then image combination capability is achieved, but manufacturing cost increases and production difficulty increases
Solution Approach 1:
The combiner is divided into multiple discrete layers (diffractive grating layer, first color combiner layer, second color combiner layer, third color combiner layer) that can be manufactured and assembled separately. Each layer performs a specific function (diffraction, color separation, reflection/transmission), allowing for simplified manufacturing processes and easier quality control compared to monolithic holographic combiners.
Solution Approach 2:
The combiner assembly serves multiple functions through its layered structure: it combines images, separates colors, reflects light, and transmits light simultaneously. Each layer is designed to perform specific optical functions that collectively achieve the overall image combination capability while using readily manufacturable components.
2Reliability
If holographic combiners are used, then image combination capability is achieved, but device lifespan decreases due to environmental degradation
Solution Approach 1:
By segmenting the combiner into multiple replaceable layers, the patent enables selective replacement of degraded components. If one layer deteriorates due to environmental factors, only that specific layer needs replacement rather than the entire combiner, thereby extending the overall device lifespan.
Solution Approach 2:
The layered structure allows individual layers to be designed as disposable or replaceable components. When a layer degrades from environmental exposure, it can be replaced with a new layer, extending the functional life of the combiner system without requiring replacement of the entire assembly.
3Reliability
If clear see-through substrate combiners are used, then external view transmission is achieved, but device size increases due to bulky lenses and angled substrate
Solution Approach 1:
The patent transitions from a single-plane clear substrate to a multi-layer stacked architecture, adding the dimension of layering. This allows optical functions (diffraction, color separation, reflection, transmission) to be achieved in a compact vertical arrangement rather than requiring large angled substrates and bulky external lenses, thereby reducing overall device volume while maintaining external view transmission.
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 diffractive optical combiner system effectively combines virtual and real images in a compact form, reducing material costs and environmental degradation, enabling durable and efficient near-eye displays for augmented reality applications.
Implementation Method 1
A diffractive optical combiner system with multiple color layers, each with a diffractive grating... directs colors substantially normal to the user's eye
Implementation Method 2
each with a diffractive grating coated with a color filter
Implementation Method 3
combines image light with external scene light using reflective and partially transmissive filters
Data Source
AI summary
An optical combiner includes a first, second, and third color combiner layer (“CCL”). The first CCL includes a first diffractive grating coated with a first filter configured to reflect a first color light and pass a second and a third color light. The second CCL includes a second diffractive grating coated with a second filter configured to reflect the second color light and pass the third color light. The third CCL includes a third diffractive grating coated with a third filter configured to partially reflect visible light. The diffractive gratings are each embedded in an index matched material and are angle-tuned diffractive gratings configured to receive image light at an angle and respectively reflect the first, second, and third color light in the image light at an order of diffraction that directs the light to an eye of a user.