AR Optical Device Using Micro-Mirror Array for Wide Field of View
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Solution Overview
Problem
Conventional augmented reality optical devices are cumbersome, expensive to manufacture, and have limitations in field of view and focal length adjustment, often requiring separate operations or hardware for adjusting focal length, and previous solutions using small reflective units resulted in a narrow field of view.
Innovation Solution
An optical device utilizing multiple reflective units smaller than the human pupil, with distances between them set to 8 mm or less, arranged to maintain a wide field of view and improve luminous uniformity by creating a pinhole effect and increasing the depth of field, allowing for a wider eye box without disconnecting virtual images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical systems (prisms, HMD) are used to implement augmented reality, then virtual images can be superimposed on real world images, but the device weight and volume become considerable and manufacturing costs are high
Solution Approach 1:
The patent divides the single large reflective surface into multiple small reflective units (micro-mirrors) arranged in an array. Each micro-mirror is significantly smaller than the human pupil diameter, allowing them to be distributed across a larger area while maintaining compact form factor. This segmentation enables the system to achieve the required optical function with much lighter and smaller components compared to conventional single-prism HMD systems.
2Reliability
If conventional optical systems are used, then augmented reality can be implemented, but the manufacturing processes are complicated and costs are high
Solution Approach 1:
The patent replaces complex mechanical optical systems (prisms, lenses, mirrors) with a electronically controllable array of micro-mirrors. Each micro-mirror can be independently controlled via electrical signals, allowing dynamic adjustment of reflected light paths. This substitution of mechanical optical components with electro-optical elements simplifies manufacturing processes and reduces system complexity while maintaining augmented reality functionality.
3Reliability
If a single small reflective unit is used to reflect virtual images through the pupil, then the depth of field increases and virtual images remain clear at various focal lengths, but the field of view becomes narrow
Solution Approach 1:
The patent uses multiple small reflective units arranged in an array where each unit corresponds to a specific angular direction. By distributing many such units across the aperture, the system maintains the depth of field benefit of small reflective elements while collectively providing a wide field of view. Each micro-mirror handles a specific angular range, and the combination of all micro-mirrors covers the full desired field of view.
Solution Approach 2:
The patent transitions from a single reflective element to a two-dimensional array of reflective units. This spatial arrangement in multiple dimensions allows the system to simultaneously achieve narrow effective aperture for each unit (providing depth of field) and large overall aperture coverage (providing wide field of view). The angular distribution of multiple units in different positions creates the expanded field of view while maintaining image clarity.
4Area of stationary object
If multiple reflective units are used to widen field of view, then field of view increases, but virtual images may become disconnected if spacing between units is too large
Solution Approach 1:
The patent optimizes the spacing parameter between adjacent reflective units to be equal to or less than the diameter of the human pupil. This parameter control ensures that the exit pupils from adjacent micro-mirrors overlap or at least touch, preventing gaps in the visual field. By carefully controlling this critical dimension, the system achieves wide field of view through multiple units while maintaining continuous, seamless virtual images without disconnection.
Data Source
AI summary
The present invention relates to an optical device for augmented reality, and provides an optical device for augmented reality, the optical device including: a plurality of reflective units arranged to reflect image light, output from an image output unit configured to output image light corresponding to an image for augmented reality, toward the pupil of an eye of an user; wherein each of the plurality of reflective units is disposed such that the distance to an adjacent reflective unit is 8 mm or less.