Angled Decoupling Structure for Smart Glasses
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Solution Overview
Problem
Data glasses face the issue of 'footprint overlap' which limits the field of view and exit pupil size due to the need for a relatively high lens thickness, causing rays to be lost during the decoupling process, especially when trying to increase the field of view angle or eye box diameter.
Innovation Solution
The use of a decoupling structure with two substructures arranged at an angle β to each other on the spectacle lens, which shifts the reflection points outside the decoupling structure, allowing for increased light throughput and reduced lens thickness, and includes a beam splitter structure to align partial imaging beam paths for recombination at a common image point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a relatively high lens thickness is used to guide the imaging beam path with multiple total reflections, then the light throughput is sufficient, but the field of view and exit pupil size are limited due to footprint overlap
Solution Approach 1:
The decoupling structure is divided into two separate decoupling elements arranged at an angle to each other. This segmentation allows the beam paths to be decoupled in two stages, preventing the footprint overlap that occurs with a single decoupling structure, thereby enabling a larger field of view without increasing lens thickness
Solution Approach 2:
The two decoupling elements are arranged at an angle β to each other, introducing an angular dimension to the decoupling process. This angular arrangement separates the footprint areas of different beam paths in the angular domain, preventing overlap and enabling increased field of view while maintaining compact lens thickness
2Area of stationary object
If the field of view angle is increased, then the desired extension of the light pipe is achieved, but footprint overlap occurs causing rays to be lost during decoupling
Solution Approach 1:
By dividing the decoupling structure into two separate decoupling elements, each element handles a portion of the beam paths. This segmentation ensures that rays from different field positions are decoupled at different locations, preventing footprint overlap and eliminating light loss even when the eye box diameter is increased
Solution Approach 2:
The two decoupling elements act as intermediary structures that progressively decouple different portions of the beam paths. This intermediate decoupling approach prevents direct footprint overlap between rays from different field positions, reducing light loss while enabling larger eye box diameter
3Device complexity
If a single decoupling structure is used, then the structure is simple, but footprint overlap limits the performance of data glasses
Solution Approach 1:
The decoupling structure is segmented into two decoupling elements arranged at an angle to each other. This segmentation increases the field of view by preventing footprint overlap, while the modular nature of the two elements keeps the overall structural complexity manageable
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 significantly reduces the 'footprint overlap' issue, enabling a larger field of view angle and eye box diameter with a thinner lens, allowing for improved light throughput and integration into data glasses without increasing bulk.
Implementation Method 1
Light generated by an imaging device is collimated outside of the lens and coupled via the front surface of the lens, from where it propagates to the eye via multiple total reflection
Implementation Method 2
The two partial imaging beam paths are reflected by a reflection surface formed on the outer surface of the spectacle lens in the coupling section in such a way
Data Source
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AI summary
The invention relates to an imaging optical unit for producing a virtual image. The imaging optical unit comprises at least one eyeglass lens (1) to be worn in front of the eye, which has an inner surface (3) to be directed toward the eye and an outer surface (5) to be directed away from the eye; a display device (13), which comprises an image generator (15) for displaying an initial image, wherein the image generator (15) is the starting point of an imaging beam path that produces the virtual image from the initial image; an incoupling device (29, 31, 33) for coupling the imaging beam path in between the inner surface (3) and the outer surface (5) of the eyeglass lens (1); and an outcoupling structure (7, 107, 207) present in the eyeglass lens (1) for coupling the imaging beam path out of the eyeglass lens (1) toward the eye. The incoupling device (29, 31, 33) couples the imaging beam path in between the inner surface (3) and the outer surface (5) of the eyeglass lens (1) in such a way that the imaging beam path is conducted to the outcoupling structure (7) by means of reflections between the inner surface (3) and the outer surface (5). The outcoupling structure (7) is composed, along a separating line (39), of two partial structures (41, 43), which extend at an angle β to each other and which couple beam paths (25, 27) incident from different directions out toward the eye, wherein the different directions of the incident beam paths (25, 27) are determined by the angle (β) between the partial structures (41, 43). There is a beam-splitting structure (21, 23) between the display device (7) and the region of the eyeglass lens (1) in which the first reflection occurs. The beam-splitting structure splits the imaging beam path extending from the image generator (15) into two imaging partial beam paths, which form the beam paths (25, 27) incident on the partial structures (41, 43) of the outcoupling structure from different directions.