Micro Mirror Array for Expanded Eye Box in HMDs
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Solution Overview
Problem
Current head mount display (HMD) systems face challenges in expanding the viewing window or eye box area, where users can observe images, as they often result in limited visibility due to fixed focal points and noise spots.
Innovation Solution
A display device comprising a light source array, a spatial light modulator, and a micro mirror array, controlled by a processor to selectively drive light sources and mirror cells, allowing image light to be focused at multiple positions within the eye box, and controlling mirror cells to direct image light either inside or outside the eye box, thereby expanding the viewing window and reducing noise spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a fixed focal point optical system is used, then the optical path is simple, but the viewing window area is limited
Solution Approach 1:
The patent divides the optical system into multiple independent components: a light source array with multiple light sources, a spatial light modulator, and a micro mirror array. Each component can be independently controlled to focus light at different positions within the eye box, thereby expanding the viewing window area while maintaining manageable system complexity through modular design.
Solution Approach 2:
The patent employs dynamic control mechanisms where the spatial light modulator and micro mirror array can be selectively adjusted to direct light from different light sources to various focal positions within the eye box. This dynamic reconfigurability allows the system to adapt to different viewing conditions and expand the effective viewing window without requiring a completely complex static optical design.
2Area of stationary object
If multiple light sources are used to expand viewing window, then the viewing window area increases, but noise spots increase
Solution Approach 1:
The patent applies local quality control by using the micro mirror array to selectively direct light from specific light sources to specific focal positions within the eye box. By controlling which light sources are activated and where their light is focused, the system can expand the viewing window while minimizing noise spots by preventing light from non-driving light sources from creating harmful focal points.
Solution Approach 2:
The spatial light modulator acts as an intermediary component between the light source array and the micro mirror array. It modulates the light from multiple light sources before the light reaches the micro mirror array, enabling selective control over which light sources contribute to the final image and which are suppressed, thereby expanding the viewing window while reducing noise spots.
3Object-generated harmful factors
If additional filters are used to reduce noise spots, then noise spots decrease, but device complexity increases
Solution Approach 1:
The patent replaces the need for additional optical filters with a controllable mechanical/optical switching system using the micro mirror array and spatial light modulator. By dynamically controlling which light sources are activated and directed to which focal positions, the system can reduce noise spots without requiring physical filters, thereby maintaining simpler device architecture while achieving the desired noise reduction.
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 effectively enlarges the viewing window by focusing image light at multiple positions within the eye box, improving visibility and reducing noise spots without the need for additional filters, enhancing the user's experience in applications like virtual and augmented reality.
Implementation Method 1
a spatial light modulator configured to modulate light from the light source array to form image light
Implementation Method 2
a focusing optical system configured to focus the image light formed by the spatial light modulator at a first position in an eye box
Implementation Method 3
The focusing optical system may comprise a first lens and a second lens that are arranged in order in the optical path from the light source array to the eye box
Implementation Method 4
control one or more mirror cells of the plurality of mirror cells to be in an ON state in which the image light is reflected in a first direction toward the first position that is inside of the eye box
Data Source
AI summary
A display device includes a light source array including a plurality of light sources where at least one of the plurality of light sources is selectively driven, a spatial light modulator for modulating light from the light source array to form image light, a focusing optical system for focusing the image light formed by the spatial light modulator at a position in a predetermined eye box, a micro mirror array arranged in an optical path formed in the focusing optical system and including a plurality of mirror cells. The plurality of mirror cells are controlled to be in an ON state in that light is reflected in a direction toward an inside of the eye box or to be in an OFF state in that light is reflected in a direction toward an outside of the eye box.