Switchable Hot Mirror Array for Compact Eye Imaging

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Solution Overview

Problem

Positioning eye-imaging cameras on head-mounted devices poses challenges due to occlusion of the real-world view and oblique viewing angles, leading to increased device cost and complexity with traditional single hot mirrors.

Innovation Solution

Employing a switchable hot mirror array with multiple, angled mirrors that can be controlled to reflect or transmit infrared light selectively, allowing for a more compact design without sacrificing camera field of view.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple separate imaging systems are used to cover different spectral regions, then spectral coverage is improved, but device complexity increases

Engineering Contradiction:
Improvespectral coverageVSAvoiddevice complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple imaging systems into a single integrated system that uses a single objective lens and sensor platform. Different hot mirror configurations enable the same physical system to capture UV, visible, and SWIR spectral regions sequentially, eliminating the need for multiple separate imaging systems while maintaining full spectral coverage

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The single imaging system is designed to perform multiple functions by switching between different hot mirror configurations. The same objective lens and sensor can capture images across UV, visible, and SWIR regions by changing the spectral filtering configuration, making the system universal rather than specialized for one spectral band

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If multiple separate imaging systems are used, then spectral coverage is improved, but alignment precision becomes more difficult

Engineering Contradiction:
Improvespectral coverageVSAvoidalignment precision
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

By merging multiple imaging functions into a single system with a common objective lens and sensor platform, the patent eliminates the need for precise alignment between multiple separate systems. The shared optical path ensures automatic co-alignment of UV, visible, and SWIR images, solving the alignment precision problem while maintaining spectral coverage

Inventive Principle:
Principle #5Merging (Combining)

3Device complexity

If a single imaging system is used, then device complexity is reduced, but spectral coverage is limited

Engineering Contradiction:
Improvedevice complexityVSAvoidspectral coverage
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent introduces dynamic switching capability between different hot mirror configurations within the single imaging system. The ability to change spectral filtering configurations allows the system to adapt and cover UV, visible, and SWIR regions sequentially, enabling a simple single-system architecture to achieve multi-spectral coverage through dynamic reconfiguration

Inventive Principle:
Principle #15Dynamics

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

Enables a more compact form factor for head-mounted devices while maintaining effective eye imaging, reducing bulkiness and weight, and minimizing design complications.

Implementation Method 1

hot mirrors that reflect infrared radiation

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 2

hot mirrors that reflect infrared radiation while transmitting visible light

Methodology Applied
Scientific EffectOptical filtering: Filter (optical)

Implementation Method 3

single objective lens to a single imaging sensor

Methodology Applied
Scientific EffectOptical focusing: Lens

Data Source

PatentEP4505236B1Eye-imaging system with switchable hot mirrors
Publication Date: 2026.05.06 MICROSOFT TECHNOLOGY LICENSING LLC
  • EP4505236B1 patent drawingFigure 1~2
  • EP4505236B1 patent drawingFigure 3
  • EP4505236B1 patent drawingFigure 4A~4B

AI summary

Examples are disclosed that relate to using an array of hot mirrors in an eye-imaging system. One example provides a head-mounted display system, comprising a frame, an eye-imaging camera supported on the frame, a switchable hot mirror array comprising a plurality of switchable hot mirrors configured to direct light reflecting from an eye toward the eye-imaging camera, and a controller configured to control switching of a reflectivity of each of the plurality of switchable hot mirrors.